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Sample records for residual refractive error

  1. Refractive Errors

    Science.gov (United States)

    ... Conditions Frequently Asked Questions Español Condiciones Chinese Conditions Refractive Errors in Children En Español Read in Chinese How does the ... birth and can occur at any age. The prevalence of myopia is low in US children under the age of eight, but much higher ...

  2. Uncorrected refractive errors

    Directory of Open Access Journals (Sweden)

    Kovin S Naidoo

    2012-01-01

    Full Text Available Global estimates indicate that more than 2.3 billion people in the world suffer from poor vision due to refractive error; of which 670 million people are considered visually impaired because they do not have access to corrective treatment. Refractive errors, if uncorrected, results in an impaired quality of life for millions of people worldwide, irrespective of their age, sex and ethnicity. Over the past decade, a series of studies using a survey methodology, referred to as Refractive Error Study in Children (RESC, were performed in populations with different ethnic origins and cultural settings. These studies confirmed that the prevalence of uncorrected refractive errors is considerably high for children in low-and-middle-income countries. Furthermore, uncorrected refractive error has been noted to have extensive social and economic impacts, such as limiting educational and employment opportunities of economically active persons, healthy individuals and communities. The key public health challenges presented by uncorrected refractive errors, the leading cause of vision impairment across the world, require urgent attention. To address these issues, it is critical to focus on the development of human resources and sustainable methods of service delivery. This paper discusses three core pillars to addressing the challenges posed by uncorrected refractive errors: Human Resource (HR Development, Service Development and Social Entrepreneurship.

  3. Uncorrected refractive errors.

    Science.gov (United States)

    Naidoo, Kovin S; Jaggernath, Jyoti

    2012-01-01

    Global estimates indicate that more than 2.3 billion people in the world suffer from poor vision due to refractive error; of which 670 million people are considered visually impaired because they do not have access to corrective treatment. Refractive errors, if uncorrected, results in an impaired quality of life for millions of people worldwide, irrespective of their age, sex and ethnicity. Over the past decade, a series of studies using a survey methodology, referred to as Refractive Error Study in Children (RESC), were performed in populations with different ethnic origins and cultural settings. These studies confirmed that the prevalence of uncorrected refractive errors is considerably high for children in low-and-middle-income countries. Furthermore, uncorrected refractive error has been noted to have extensive social and economic impacts, such as limiting educational and employment opportunities of economically active persons, healthy individuals and communities. The key public health challenges presented by uncorrected refractive errors, the leading cause of vision impairment across the world, require urgent attention. To address these issues, it is critical to focus on the development of human resources and sustainable methods of service delivery. This paper discusses three core pillars to addressing the challenges posed by uncorrected refractive errors: Human Resource (HR) Development, Service Development and Social Entrepreneurship.

  4. The uncorrected refractive error challenge

    Directory of Open Access Journals (Sweden)

    Kovin Naidoo

    2016-11-01

    Full Text Available Refractive error affects people of all ages, socio-economic status and ethnic groups. The most recent statistics estimate that, worldwide, 32.4 million people are blind and 191 million people have vision impairment. Vision impairment has been defined based on distance visual acuity only, and uncorrected distance refractive error (mainly myopia is the single biggest cause of worldwide vision impairment. However, when we also consider near visual impairment, it is clear that even more people are affected. From research it was estimated that the number of people with vision impairment due to uncorrected distance refractive error was 107.8 million,1 and the number of people affected by uncorrected near refractive error was 517 million, giving a total of 624.8 million people.

  5. REFRACTIVE ERROR STATUS IN BAYELSA STATE, NIGERIA

    African Journals Online (AJOL)

    LIVINGSTON

    vision) thus making refractive error the leading cause of low vision and the second leading cause of blindness following cataract which remained the leading cause of blindness globally. Various studies have documented the prevalence of refractive errors in different population groups. Among adult Chinese population in ...

  6. Relationship between conjunctivochalasis and refractive error.

    Science.gov (United States)

    Mimura, Tatsuya; Usui, Tomohiko; Yamagami, Satoru; Funatsu, Hideharu; Noma, Hidetaka; Toyono, Tetsuya; Mori, Mikiro; Amano, Shiro

    2011-03-01

    To assess the relation between the prevalence and grade of conjunctivochalasis and refractive error and to compare the grade of conjunctivochalasis between myopic and hyperopic patients. Consecutive patients aged from 3 to 94 years were chosen for this study. Exclusion criteria included a history of using contact lenses, ocular surgeries, infectious conjunctivitis, or corneal diseases. The age, gender, medical history, ocular history, the grade and other parameters of inferior conjunctivochalasis classified into three locations (nasal, middle, and temporal), and refractive error were determined in all subjects. Patients were divided into three groups as follows: a hyperopic group (≥0.0 D), an emmetropic group (refractive error, especially in patients over 40 years old (Prefractive error and the grade of conjunctivochalasis in a large consecutive series of patients. Our results suggest that the prevalence and grade of conjunctivochalasis are dependent on refractive error, with hyperopia being an important risk factor for conjunctivochalasis.

  7. Survey of Radar Refraction Error Corrections

    Science.gov (United States)

    2016-11-01

    RANGE YUMA PROVING GROUND NAVAL AIR WARFARE CENTER AIRCRAFT DIVISION NAVAL AIR WARFARE CENTER WEAPONS DIVISION NAVAL UNDERSEA WARFARE CENTER...estimation for an electromagnetic wave propagating at radio frequencies through the earth’s atmosphere. Appendices contain descriptive material on the...of Radar Refraction Error Corrections, RCC 266-16 vii Acronyms BAE BAE Systems CRPL Central Radio Propagation Laboratory EM electromagnetic

  8. 37 REFRACTIVE ERROR BLINDNESS IN YENAGOA, BAYELSA ...

    African Journals Online (AJOL)

    Vol. 12 No. 1 December, 2010. Refractive Error Blindness in Yenagoa, Bayelsa State, Nigeria. 39. (PVA) was measured using a snellen visual acuity chart and a full ocular examination was carried out including anterior segment examination using a. Haag-Streit slit lamp biomicroscope and a posterior segment examination.

  9. Pattern Of Refractive Errors Among Computer Users In A Nigerian ...

    African Journals Online (AJOL)

    Background: Refractive error is a common cause of ocular morbidity. Computer use is associated with eye strain which may be due to refractive errors. Objective: To ascertain the prevalence and pattern of refractive errors among computer users. Method: A cross-sectional survey of 560 computer users in Enugu urban, ...

  10. Refractive Error Status In Bayelsa State, Nigeria | Koroye-Egbe ...

    African Journals Online (AJOL)

    Refractive errors affect the whole spectrum of the population without regard to age, gender, race and ethnic group. Uncorrected refractive errors have severe consequences for the individual, family and society.Records showthat no study documenting the distribution of refractive errors in Bayelsa State had been carried out.

  11. Delivering refractive error services: primary eye care centres and outreach

    OpenAIRE

    Naidoo, Kovin; Ravilla, Dhivya

    2007-01-01

    Addressing refractive errors, the second major cause of preventable blindness, is now a priority for eye care programmes.Although a simple pair of spectacles will correct refractive error, there exists a high prevalence of uncorrected refractive error. This is due in large part to the cost and inaccessibility of refraction and spectacle dispensing services, which are usually offered only at secondary and tertiary eye care centres.

  12. Case Finding for Refractive Errors: Assessment of Refractive Error and Visual Impairment in Children

    OpenAIRE

    Ellwein, Leon B

    2002-01-01

    The World Health Organization informal planning meeting, in July 2000, clearly indicated that detailed comparisons of refractive error prevalence across study reports are generally not possible because of different measurement methods and definitions.1 Further, because most studies are carried out using samples of unknown representativeness, interpretation of the findings in a population-based context has problems.

  13. Case Finding for Refractive Errors: Assessment of Refractive Error and Visual Impairment in Children

    Directory of Open Access Journals (Sweden)

    Leon B Ellwein

    2002-01-01

    Full Text Available The World Health Organization informal planning meeting, in July 2000, clearly indicated that detailed comparisons of refractive error prevalence across study reports are generally not possible because of different measurement methods and definitions.1 Further, because most studies are carried out using samples of unknown representativeness, interpretation of the findings in a population-based context has problems.

  14. Association of refractive error with optic nerve hypoplasia.

    Science.gov (United States)

    Pang, Yi; Frantz, Kelly A; Roberts, Daniel K

    2015-09-01

    To evaluate the association of refractive error with optic nerve hypoplasia (ONH). A total of 30 ONH subjects were recruited and underwent comprehensive eye exams. Refractive error data from this group was compared to data from a group of 3232 non-ONH subjects from the same facility. Spherical equivalent was calculated to assess refractive error. Multiple logistic regression was used to evaluate the relationship between ONH and refractive error while controlling for age, race, and gender. The prevalence of hyperopia (≥+1.00 D), myopia (refractive errors, particularly hyperopia. Anisometropia tended to be more likely to occur in subjects with unilateral ONH than in bilateral ONH. Based on our findings, we recommend that clinicians perform a comprehensive eye examination on all patients with ONH and prescribe for existing refractive error when visual acuity or general visual function can realistically be improved. © 2015 The Authors Ophthalmic & Physiological Optics © 2015 The College of Optometrists.

  15. PREVALENCE OF REFRACTIVE ERRORS IN MADRASSA STUDENTS OF HARIPUR DISTRICT.

    Science.gov (United States)

    Atta, Zoia; Arif, Abdus Salam; Ahmed, Iftikhar; Farooq, Umer

    2015-01-01

    Visual impairment due to refractive errors is one of the most common problems among school-age children and is the second leading cause of treatable blindness. The Right to Sight, a global initiative launched by a coalition of non-government organizations and the World Health Organization (WHO), aims to eliminate avoidable visual impairment and blindness at a global level. In order to achieve this goal it is important to know the prevalence of different refractive errors in a community. Children and teenagers are the most susceptible groups to be affected by refractive errors. So, this population needs to be screened for different types of refractive errors. The study was done with the objective to find the frequency of different types of refractive errors in students of madrassas between the ages of 5-20 years in Haripur. This cross sectional study was done with 300 students between ages of 5-20 years in Madrassas of Haripur. The students were screened for refractive errors and the types of the errors were noted. After screening for refractive errors-the glasses were prescribed to the students. Myopia being 52.6% was the most frequent refractive error in students, followed by hyperopia 28.4% and astigmatism 19%. This study showed that myopia is an important problem in madrassa population. Females and males are almost equally affected. Spectacle correction of refractive errors is the cheapest and easy solution of this problem.

  16. Ethnic differences in undercorrected refractive error in Asians.

    Science.gov (United States)

    Pan, Chen-Wei; Chiang, Peggy Pei-Chia; Wong, Tien Y; Zheng, Ying-Feng; Chew, Merwyn; Saw, Seang-Mei; Lamoureux, Ecosse L; Cheng, Ching-Yu

    2014-02-01

    To describe the ethnic variations in the prevalence and risk factors for undercorrected refractive error and its impact on vision-specific functioning (VF) in a multiethnic Asian population. A total of 3353 Chinese, 3400 Indians, and 3280 Malays in Singapore participated in this population-based cross-sectional study. Distance presenting visual acuity (VA) was measured using a logarithm of the minimum angle of resolution number chart. Best-corrected VA was assessed using the same test protocol as presenting VA. Undercorrected refractive error was defined as an improvement of at least 0.2 logarithm of the minimum angle of resolution (two lines equivalent) in the best-corrected VA compared with the presenting VA in the better eye when presenting VA was less than 20/40 in the better eye. The VF-11 questionnaire measured participants' VF. Multivariate linear regression was performed to assess the impact of undercorrected refractive error on the overall VF score. Regardless of ethnicity, participants with undercorrected refractive error had a reduction in VF score compared to those with normal vision in both eyes. The overall prevalence of undercorrected refractive error was highest in Indians (25.1%), followed by Malays (22.2%) and Chinese (19.7%). Undercorrected refractive error was less common in spectacles or contact lenses wearers than in non-spectacle wearers or non-contact lenses wearers. Adults with mild to moderate refractive errors were most likely to have undercorrected refractive error (p refractive errors (p refractive error. In Singapore, undercorrected refractive error is most prevalent in Indians and least prevalent in Chinese. The impact of undercorrected refractive error on VF was consistent across all three ethnicities. There may be higher barriers to visual correction among Malays or Indians compared with Chinese in Singapore.

  17. Training to meet the need for refractive error services

    Directory of Open Access Journals (Sweden)

    Hannah Faal

    2007-09-01

    Full Text Available In many low- and middle-income countries, there are inadequate refractive error services for the many people who are currently either blind or visually impaired because they lack a pair of spectacles.The prioritisation of refractive error and low vision services within VISION 2020: The Right to Sight has provided an impetus and framework for the development of refractive error programmes to meet this need for services.

  18. Influence of uncorrected refractive error and unmet refractive error on visual impairment in a Brazilian population.

    Science.gov (United States)

    Ferraz, Fabio H; Corrente, José E; Opromolla, Paula; Schellini, Silvana A

    2014-06-25

    The World Health Organization (WHO) definitions of blindness and visual impairment are widely based on best-corrected visual acuity excluding uncorrected refractive errors (URE) as a visual impairment cause. Recently, URE was included as a cause of visual impairment, thus emphasizing the burden of visual impairment due to refractive error (RE) worldwide is substantially higher. The purpose of the present study is to determine the reversal of visual impairment and blindness in the population correcting RE and possible associations between RE and individual characteristics. A cross-sectional study was conducted in nine counties of the western region of state of São Paulo, using systematic and random sampling of households between March 2004 and July 2005. Individuals aged more than 1 year old were included and were evaluated for demographic data, eye complaints, history, and eye exam, including no corrected visual acuity (NCVA), best corrected vision acuity (BCVA), automatic and manual refractive examination. The definition adopted for URE was applied to individuals with NCVA > 0.15 logMAR and BCVA ≤ 0.15 logMAR after refractive correction and unmet refractive error (UREN), individuals who had visual impairment or blindness (NCVA > 0.5 logMAR) and BCVA ≤ 0.5 logMAR after optical correction. A total of 70.2% of subjects had normal NCVA. URE was detected in 13.8%. Prevalence of 4.6% of optically reversible low vision and 1.8% of blindness reversible by optical correction were found. UREN was detected in 6.5% of individuals, more frequently observed in women over the age of 50 and in higher RE carriers. Visual impairment related to eye diseases is not reversible with spectacles. Using multivariate analysis, associations between URE and UREN with regard to sex, age and RE was observed. RE is an important cause of reversible blindness and low vision in the Brazilian population.

  19. Refractive errors in presbyopic patients in Kano, Nigeria | Lawan ...

    African Journals Online (AJOL)

    Background: The study is a retrospective review of the pattern of refractive errors in presbyopic patients seen in the eye clinic from January to December, 2009. Patients and Methods: The clinic refraction register was used to retrieve the case folders of all patients refracted during the review period. Information extracted ...

  20. Refractive errors in presbyopic patients in Kano, Nigeria

    African Journals Online (AJOL)

    Background:The study is a retrospective review of the pattern of refractive errors in presbyopic patients seen in the eye clinic from January to December, 2009. Patients and Methods: The clinic refraction register was used to retrieve the case folders of all patients refracted during the review period. Information extracted ...

  1. Refractive error among urban preschool children in Xuzhou, China

    OpenAIRE

    Wang, Xiaojuan; Liu, Dan; Feng, Ruifang; Zhao, Huashuo; Wang, Qinmei

    2014-01-01

    The prevalence of refractive errors in urban preschool children in Xuzhou, China remains unknown. Children attending twelve randomly selected kindergartens participated in this study. Visual acuity, ocular alignment, cover-uncover test, cycloplegic refraction, slit-lamp and funduscopy were performed under a standardized testing environment. Cycloplegic streak retinoscopy was performed for all subjects. The mean spherical equivalent (SE) refractive error was the main outcome measure. Emmetropi...

  2. Screening for Uncorrected Refractive Error Among Primary School ...

    African Journals Online (AJOL)

    A study on screening for uncorrected refractive error in primary school children has not been done in Bayelsa State, South-South Nigeria. This study aims to screen for uncorrected refractive error among primary school children in Bayelsa State and use the data to plan for an effective school Eye Health Program. A cross ...

  3. Paediatric Refractive Errors in an Eye Clinic in Osogbo, Nigeria ...

    African Journals Online (AJOL)

    Background: Paediatric ophthalmology is an emerging subspecialty in Nigeria and as such there is paucity of data on refractive errors in the country. This study set out to determine the pattern of refractive errors in children attending an eye clinic in South West Nigeria. Methods: A descriptive study of 180 consecutive ...

  4. Refractive errors among students of a postprimary institution in a ...

    African Journals Online (AJOL)

    Out of these, 9 (2.53%) had uncorrected vision worse than 6/9 in either or both eyes. Uncorrected refractive error accounted for the reduced vision in 7 cases 5 of which were myopia. Conclusion: There is a prevalence of refractive error of 1.97% among students of this rural girls' secondary school in South-Eastern Nigeria.

  5. Prevalence of Refractive Error and Visual Impairment among Rural ...

    African Journals Online (AJOL)

    Refractive error was the major cause of visual impairment accounting for 54% of all causes in the study group. No child was found wearing ... So, large scale community level screening for refractive error should be conducted and integrated with regular school eye screening programs. Effective strategies need to be devised ...

  6. Prevalence of refractive errors among junior high school students in ...

    African Journals Online (AJOL)

    Among school children, uncorrected refractive errors have a considerable impact on their participation and learning in class. The aim of this study was to assess the prevalence of refractive error among students in the Ejisu-Juabeng Municipality of Ghana. A survey with multi-stage sampling was undertaken. We interviewed ...

  7. Refractive errors in school children in Onitsha, Nigeria | Nwosu ...

    African Journals Online (AJOL)

    Conclusions: There is a high incidence of uncorrected refractive errors among school children, although many were of small degrees. The cooperation of parents and teachers is vital in identifying and treating this modifiable cause of poor academic performance and learning difficulties. Keywords: refractive errors, school ...

  8. Prevalence of Refractive Error in Singaporean Chinese Children: The Strabismus, Amblyopia, and Refractive Error in Young Singaporean Children (STARS) Study

    OpenAIRE

    Dirani, Mohamed; Chan, Yiong-Huak; Gazzard, Gus; Hornbeak, Dana Marie; Leo, Seo-Wei; Selvaraj, Prabakaran; Zhou, Brendan; Young, Terri L.; Mitchell, Paul; Varma, Rohit; Wong, Tien Yin; Saw, Seang-Mei

    2010-01-01

    Using population-based data, the authors report, for the first time, the prevalence of refractive error in Singaporean Chinese children aged 6 to 72 months. In selected regions of Singapore, myopia has been shown to affect more than 80% of adults; therefore, this paper provides insights into the development of refractive error at a very young age.

  9. Refractive Errors in State Junior High School Students in Bandung

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    Sabila Tasyakur Nikmah

    2016-12-01

    Full Text Available Background: Uncorrected refractive error is one of the avoidable causes of vision impairment in children and adults. Vision problem in children has been shown to affect their psychological and academic performance. This study aims at identifying and gaining more insights on the characteristic of the refractive errors in state junior high school students in Bandung to avoid uncorrected refractive errors. Methods: A cross-sectional study was conducted in September–November 2015 in state junior high schools in Bandung, West Java, Indonesia. Sample was selected using multistage random sampling technique. Children were examined using tumbling E examination; then students with visual acuity worse than 6/12 underwent Snellen Chart test, refractometry without pupil dilatation, correction with trial lens, then was followed by direct ophthalmoscopy. Results: From a total of 435 children who completed all the examination, 80 children (18.39% had refractive errors; consisted of 151 eyes (94.38% with myopia and 9 eyes (5.62% with astigmatism. Refractive errors were found to be more common in female children (73.7% than male children (26.3%. Among those with refractive errors, 45 children (56.3% did not use any corrective glasses before the examination. Conclusions: Routine refractive error test in vision screening examination is needed for students. It is equally important to raise more awareness toward eye disease in community.

  10. Screening for refractive error among primary school children in ...

    African Journals Online (AJOL)

    Introduction: Background: Vision screening study in primary school children has not been done in Bayelsa State. This study aims to screen for refractive error among primary school children in Bayelsa State and use the data to plan for school Eye Health Program. Methods: A cross sectional study on screening for refractive ...

  11. The prevalence of uncorrected refractive errors in underserved rural areas

    Directory of Open Access Journals (Sweden)

    Hassan Hashemi

    2017-12-01

    Full Text Available Purpose: To determine the prevalence of uncorrected refractive errors, need for spectacles, and the determinants of unmet need in underserved rural areas of Iran. Methods: In a cross-sectional study, multistage cluster sampling was done in 2 underserved rural areas of Iran. Then, all subjects underwent vision testing and ophthalmic examinations including the measurement of uncorrected visual acuity (UCVA, best corrected visual acuity, visual acuity with current spectacles, auto-refraction, retinoscopy, and subjective refraction. Need for spectacles was defined as UCVA worse than 20/40 in the better eye that could be corrected to better than 20/40 with suitable spectacles. Results: Of the 3851 selected individuals, 3314 participated in the study. Among participants, 18.94% [95% confidence intervals (CI: 13.48–24.39] needed spectacles and 11.23% (95% CI: 7.57–14.89 had an unmet need. The prevalence of need for spectacles was 46.8% and 23.8% in myopic and hyperopic participants, respectively. The prevalence of unmet need was 27% in myopic, 15.8% in hyperopic, and 25.46% in astigmatic participants. Multiple logistic regression showed that education and type of refractive errors were associated with uncorrected refractive errors; the odds of uncorrected refractive errors were highest in illiterate participants, and the odds of unmet need were 12.13, 5.1, and 4.92 times higher in myopic, hyperopic and astigmatic participants as compared with emmetropic individuals. Conclusion: The prevalence of uncorrected refractive errors was rather high in our study. Since rural areas have less access to health care facilities, special attention to the correction of refractive errors in these areas, especially with inexpensive methods like spectacles, can prevent a major proportion of visual impairment. Keywords: Uncorrected refractive errors, Population-based study, Unmet need

  12. Longitudinal study of spherical refractive error in infantile nystagmus syndrome.

    Science.gov (United States)

    Healey, Natasha; McClelland, Julie F; Saunders, Kathryn J; Jackson, A Jonathan

    2014-05-01

    To explore the onset and progression of spherical refractive error in a population with infantile nystagmus syndrome. Retrospective refractive error data were obtained from 147 medical records of children with infantile nystagmus syndrome (albinism n = 98; idiopathic infantile nystagmus n = 49), attending a low vision clinic in Northern Ireland, over a 24 year period (1986-2010). Data were categorised by age to allow for comparisons with published studies. A prospective group of participants with Infantile nystagmus syndrome (INS) [n = 22 (albinism n = 18, idiopathic infantile nystagmus n = 4)] (aged 0-4) were also recruited. Cycloplegic streak retinoscopy was performed biannually, over a 3 year period. Spherical equivalent refractive error and most ametropic meridian were analysed. The mean spherical equivalent refractive errors for albinism and idiopathic infantile nystagmus groups (across all age categories) were hypermetropic, with highest levels demonstrated by the participants with albinism aged 1 ≤ 4 years (Mann-Whitney U test, p = 0.013). Mean most ametropic meridian was highest in the albinism group aged 1 ≤ 12 years (Mann-Whitney U test, p refractive errors over time. Prospective participants were hypermetropic at all visits and those with albinism had, on average, higher refractive errors than those with idiopathic infantile nystagmus (IIN). No significant correlations were noted between visual acuity and spherical equivalent refractive errors or most ametropic meridian. Hypermetropia is the most prevalent spherical refractive error in the INS population, irrespective of level of visual acuity. Individuals with infantile nystagmus syndrome fail to demonstrate typical patterns of emmetropisation, particularly in the presence of albinism. © 2014 The Authors Ophthalmic & Physiological Optics © 2014 The College of Optometrists.

  13. Prevalence of refractive error and spectacle coverage in Zoba Ma'ekel Eritrea: a rapid assessment of refractive error.

    Science.gov (United States)

    Chan, Ving Fai; Mebrahtu, Goitom; Ramson, Prasidh; Wepo, Mary; Naidoo, Kovin S

    2013-06-01

    To determine the prevalence of refractive error and spectacle coverage in Zoba Ma'ekel, Eritrea in order to assist in planning for refractive services and blindness prevention strategies. A community-based cross-sectional study using multistage cluster sampling was conducted. A total of 3200 participants aged 15-50 years were enumerated and examined using the Rapid Assessment of Refractive Error (RARE) protocol. The response rate was 99.1%. The prevalence of refractive error was 6.4% (95% confidence interval [CI], 5.6-7.2%). Spectacle coverage for refractive error was 22.2% (95% CI 16.7-28.5%). It was higher among males than females (Fisher's exact test, p = 0.028), and highest in those who had completed secondary school (48.6%, 95% CI 31.9-65.6%) and those who resided in Asmara (Fisher's exact test, p prevalence of presbyopia was 32.9% (95% CI 30.3-35.7%) with 94.9% correctable. Spectacle use for presbyopia was 9.9% (95% CI 7.2-13.4%), which was lowest in those with no formal schooling but highest in those who had completed secondary school (χ(2) test, p refractive service planning in Zoba Ma'ekel. Uncorrected refractive error is of public health importance and prompt measures are needed to address the problem.

  14. Refractive Error, Srabismus and Amblyopia in Congenital Ptosis

    Directory of Open Access Journals (Sweden)

    R Thapa

    2010-03-01

    Full Text Available INTRODUCTION: Congenital ptosis is often associated with visual impairment. The aim of the study is to find out the pattern of refractive error,strabismus and amblyopia in patients with congenital ptosis in a hospital setting. METHODS: This is a hospital based prospective and descriptive study conducted at Tribhuvan University, B P Koirala Lion's Centre for Ophthalmic studies in Nepal from February 2003 to July 2004. All the consecutive cases with congenital ptosis were included and cases with pseudoptosis were excluded from the study. RESULTS: Among the 78 cases (95 eyes of congenital ptosis, refractive error was present in 13 cases (16.7% with astigmatism as the commonestrefractive error (8.9%. Strabismus was found in 23 cases (26.9% of congenital ptosis. Among the strabismus, combined exotropia with hypotropia was found in the majority of cases (16.7%. Visual impairment due to amblyopia was found in 15 cases (19.2% of congenital ptosis with mixed strabismic and refractive etiology as the commonest one (46.7% followed by pure strabismic (26.7%, pure refractive (20% and stimulus deprivationamblyopia (6.7%. CONCLUSIONS: Patients with congenital ptosis have higher rate of amblyopia due to greater prevalence of strabismus and refractive errors although stimulus deprivation amblyopia is less common. Early ophthalmic evaluation and timely treatment of these conditions may help prevent the irreversible visual impairment in case of congenital ptosis. Keywords: amblyopia, congenital ptosis, refractive error, strabismus.

  15. Refractive error magnitude and variability: Relation to age.

    Science.gov (United States)

    Irving, Elizabeth L; Machan, Carolyn M; Lam, Sharon; Hrynchak, Patricia K; Lillakas, Linda

    2018-03-19

    To investigate mean ocular refraction (MOR) and astigmatism, over the human age range and compare severity of refractive error to earlier studies from clinical populations having large age ranges. For this descriptive study patient age, refractive error and history of surgery affecting refraction were abstracted from the Waterloo Eye Study database (WatES). Average MOR, standard deviation of MOR and astigmatism were assessed in relation to age. Refractive distributions for developmental age groups were determined. MOR standard deviation relative to average MOR was evaluated. Data from earlier clinically based studies with similar age ranges were compared to WatES. Right eye refractive errors were available for 5933 patients with no history of surgery affecting refraction. Average MOR varied with age. Children <1 yr of age were the most hyperopic (+1.79D) and the highest magnitude of myopia was found at 27yrs (-2.86D). MOR distributions were leptokurtic, and negatively skewed. The mode varied with age group. MOR variability increased with increasing myopia. Average astigmatism increased gradually to age 60 after which it increased at a faster rate. By 85+ years it was 1.25D. J 0 power vector became increasingly negative with age. J 45 power vector values remained close to zero but variability increased at approximately 70 years. In relation to comparable earlier studies, WatES data were most myopic. Mean ocular refraction and refractive error distribution vary with age. The highest magnitude of myopia is found in young adults. Similar to prevalence, the severity of myopia also appears to have increased since 1931. Copyright © 2018 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.

  16. Paediatric Refractive Errors in an Eye Clinic in Osogbo, Nigeria.

    Science.gov (United States)

    Michaeline, Isawumi; Sheriff, Agboola; Bimbo, Ayegoro

    2016-03-01

    Paediatric ophthalmology is an emerging subspecialty in Nigeria and as such there is paucity of data on refractive errors in the country. This study set out to determine the pattern of refractive errors in children attending an eye clinic in South West Nigeria. A descriptive study of 180 consecutive subjects seen over a 2-year period. Presenting complaints, presenting visual acuity (PVA), age and sex were recorded. Clinical examination of the anterior and posterior segments of the eyes, extraocular muscle assessment and refraction were done. The types of refractive errors and their grades were determined. Corrected VA was obtained. Data was analysed using descriptive statistics in proportions, chi square with p value 75.0%, visual impairment20% and low vision 23.3%. Low grade spherical and cylindrical errors occurred most frequently (35.6% and 59.9% respectively). Regular astigmatism was significantly more common, P <0.001. The commonest diagnosis was simple myopic astigmatism (41.1%). Four cases of strabismus were seen. Simple spherical and cylindrical errors were the commonest types of refractive errors seen. Visual impairment and low vision occurred and could be a cause of absenteeism from school. Low-cost spectacle production or dispensing unit and health education are advocated for the prevention of visual impairment in a hospital set-up.

  17. Refractive error among urban preschool children in Xuzhou, China.

    Science.gov (United States)

    Wang, Xiaojuan; Liu, Dan; Feng, Ruifang; Zhao, Huashuo; Wang, Qinmei

    2014-01-01

    The prevalence of refractive errors in urban preschool children in Xuzhou, China remains unknown. Children attending twelve randomly selected kindergartens participated in this study. Visual acuity, ocular alignment, cover-uncover test, cycloplegic refraction, slit-lamp and funduscopy were performed under a standardized testing environment. Cycloplegic streak retinoscopy was performed for all subjects. The mean spherical equivalent (SE) refractive error was the main outcome measure. Emmetropia was defined as refractive status between +1.75 diopters (D) and -0.75D. Myopia, hyperopia, astigmatism and anisometropia were defined as SE +2.0 D, cylindrical error > 1.0 D and SE difference ≥ 1 D between fellow eyes, respectively. Out of 2349 eligible children, 2255 (96%) children completed a refractive examination. Of the 2255 children, the mean SE of right eyes was +1.14 ± 0.95 diopters (D). Mean SE of the right eyes did not decline with age (r = -0.01; P = 0.56). The majority (86.6%) of children were emmetropia. The prevalence of myopia and hyperopia was 0.9% and 14.3%, respectively. The mean astigmatism for the right eyes was 0.87 ± 0.62 D. The prevalence of With-the-rule, against the rule and oblique astigmatism was 93.8%, 4.7% and 1.5%, respectively. The mean anisometropia between two eyes was 0.14 ± 0.38 D. The most common type of refractive error was hyperopia (14.3%), followed by astigmatism (8.8%), anisometropia (3.2%), and myopia (0.9%). The refractive status in this population of urban Xuzhou preschool children was stable and there was no evidence of a myopic refractive shift over this age range in our cross-sectional study.

  18. Small Refractive Errors – Their Correction and Practical Importance

    OpenAIRE

    Skrbek, Matej; Petrová, Sylvie

    2013-01-01

    Small refractive errors present a group of specific far-sighted refractive dispositions that are compensated by enhanced accommodative exertion and aren’t exhibited by loss of the visual acuity1. This paper should answer a few questions about their correction, flowing from theoretical presumptions and expectations of this dilemma. The main goal of this research was to (dis)confirm the hypothesis about convenience, efficiency and frequency of the correction that do not raise the visual acui...

  19. Is there an association between convergence insufficiency and refractive errors?

    Directory of Open Access Journals (Sweden)

    Samuel Otabor Wajuihian

    2017-04-01

    Full Text Available Background: Refractive errors and convergence insufficiency play major roles in reading efficiency. Uncorrected refractive errors are a primary cause of binocular anomalies, including convergence insufficiency. Symptoms of asthenopia in both refractive and binocular vision anomalies are similar. Despite the relationships that exist between them, the extent of association between refractive errors and convergence insufficiency has not been studied extensively. Aim: The aim of this study was to determine the prevalence of convergence insufficiency and refractive errors and investigate their associations with gender and age in a sample of high school children. Methods: The study design was cross-sectional and comprised data from 1056 African high school students aged 13–18 years, who were randomly selected from 13 high schools in uMhlathuze municipality in the province of KwaZulu-Natal, South Africa. In the final sample, 403 (38% were males and 653 (62% were females. The participants’ mean age and standard deviation were 15.89 ± 1.58 years and median age was 16 years. Refractive errors, heterophoria, near point of convergence, fusional vergences and accommodative functions were evaluated. Results: Prevalences for convergence insufficiency were as follows: low suspect 12.4% (confidence interval, [CI] 10.2–14.4, high suspect 6.3% (CI, 5.0–7.9, definite 4.6% (CI, 3.4–5.9, and pseudo-convergence insufficiency 2.1% (CI, 1.2–3.0. Refractive errors were: hyperopia 6.8% (CI, 5.3–8.4, myopia 6.0% (CI, 4.6–7.5, astigmatism 2.3% (CI, 1.8–3.2, anisometropia 1.3% (CI, 0.7–2.0 and emmetropia 86.2% (CI, 85.1–89.1. There were no significant associations between convergence insufficiency and gender (p = 0.32, age (p = 0.38, grade levels (p = 0.99 or refractive errors (p = 0.08. Conclusion: The prevalence of clinically significant convergence insufficiency and refractive errors was low in this sample of black high school students in South

  20. Prevalence of refractive errors in children in Equatorial Guinea.

    Science.gov (United States)

    Soler, Margarita; Anera, Rosario G; Castro, José J; Jiménez, Raimundo; Jiménez, José R

    2015-01-01

    The aim of this work is to evaluate the epidemiological aspects of the refractive errors in school-aged children in Malabo (Island of Bioko), Equatorial Guinea (western-central Africa). A total of 425 schoolchildren (209 male subjects and 216 female subjects, aged between 6 and 16 years) were examined to evaluate their refraction errors in Malabo, Equatorial Guinea (western-central Africa). The examination included autorefraction with cycloplegia, measurement of visual acuity (VA) for far vision, and the curvature radii of the main meridians of the anterior surface of the cornea. A low prevalence of myopia was found (≤-0.50 diopters [D] spherical equivalent), with unilateral and bilateral myopia being 10.4 and 5.2%, respectively. The prevalence of unilateral and bilateral hypermetropia (≥2.0 D spherical equivalent) was 3.1 and 1.6%, respectively. Astigmatism (≤-0.75 D) was found in unilateral form in 32.5% of these children, whereas bilateral astigmatism was found in 11.8%. After excluding children having any ocular pathology, the low prevalence of high refractive errors signified good VA in these children. Significant differences were found in the distribution of the refractive errors by age and type of schooling (public or private) but not by sex. In general, the radii of the anterior of the cornea did not vary significantly with age. The mean refractive errors found were low and therefore VA was high in these children. There was a low prevalence of myopia, with significantly higher values in those who attended private schools (educationally and socioeconomically more demanding). Astigmatism was the most frequent refractive error.

  1. Refractive Errors and Strabismus in Down's Syndrome in Korea

    OpenAIRE

    Han, Dae Heon; Kim, Kyun Hyung; Paik, Hae Jung

    2012-01-01

    Purpose The aims of this study were to examine the distribution of refractive errors and clinical characteristics of strabismus in Korean patients with Down's syndrome. Methods A total of 41 Korean patients with Down's syndrome were screened for strabismus and refractive errors in 2009. Results A total of 41 patients with an average age of 11.9 years (range, 2 to 36 years) were screened. Eighteen patients (43.9%) had strabismus. Ten (23.4%) of 18 patients exhibited esotropia and the others ha...

  2. Refractive error in school children in Agona Swedru, Ghana

    Directory of Open Access Journals (Sweden)

    G. O. Ovenseri-Ogbomo

    2010-12-01

    Full Text Available Uncorrected refractive errors remains a public health problem among different population groups. Among schoolchildren, uncorrected refractive errors have a considerable impact on learning andacademic achievement especially in underserved and under-resourced communities. A school based cross-sectional study was carriedout to estimate the prevalence and distribution of refractive error among schoolchildren in the Agona Swedru municipality of Central Region of Ghana. 637 schoolchildren aged 11-18 years old were randomly selected for the study. Non-cycloplegic refraction was performed on each child who failed the reading test. Hyperopia was defined as spherical power of ≥ + 0.75 D, myopia as ≤ – 0.50 D and astigmatism as a cylindrical power of ≤ – 0.50 D. Of the children examined, only 13.3% had previously had an eye examination.Visual impairment (VA of 6/12 or worse in the better eye was present in 4.5% of the children examined. Of those who failed the reading test, 85.9% had refractive error. The prevalence of hyperopia, myopia and astigmatism was 5.0%, 1.7% and 6.6% respectively. The study concludes that uncorrected refractive error is a common cause of visual impairment among schoolchildren in the municipality. A low uptake of eye care is also noted in the study. The study therefore recommends that the education authority in collaboration with the District Health Directorate institute appropriate measures to ensure compulsory eye examination for schoolchildren in the Agona Swedru district. (S Afr Optom 2010 69(2 86-92

  3. Relationship between refractive error and influencing factors in Children

    Directory of Open Access Journals (Sweden)

    Hai-Jun Shi

    2014-08-01

    Full Text Available AIM: To evaluate the relationship between axial length(AL, corneal and lens refractive power, and the refractive error in children.METHODS:Totally 44 children 88 eyes with refractive error who underwent retinoscopy with cycloplegia, to be measured spherical equivalent refractive error. Axial length was measured by a noncontact optical biometry(ZEISS IOL-Master, and corneal K and anterior chamber depth(ACDwere also measured by the same machine. The refractive power of the lens was calculated by using the SRK formula. The patients were divided into 3 groups, myopia(SE+0.50Dand emmetropia(0 to +0.50D. Linear Correlation and Regression were used to evaluate the correlation among the optical parameters.RESULTS:Totally 44 subjects, 88 eyes, average 9.04±2.39 years, spherical equivalent(SE-3.50D to +8.75D. Hyperopic AL was shorter than the other two groups(PCONCLUSION:As the children's growing up, SE trends to myopia, and AL becomes longer, and lens power is stronger.

  4. Refractive errors in Cameroonians diagnosed with complete oculocutaneous albinism.

    Science.gov (United States)

    Eballé, André Omgbwa; Mvogo, Côme Ebana; Noche, Christelle; Zoua, Marie Evodie Akono; Dohvoma, Andin Viola

    2013-01-01

    Albinism causes significant eye morbidity and amblyopia in children. The aim of this study was to determine the refractive state in patients with complete oculocutaneous albinism who were treated at the Gynaeco-Obstetric and Paediatric Hospital, Yaoundé, Cameroon and evaluate its effect on vision. We carried out this retrospective study at the ophthalmology unit of our hospital. All oculocutaneous albino patients who were treated between March 1, 2003 and December 31, 2011 were included. Thirty-five patients (70 eyes) diagnosed with complete oculocutaneous albinism were enrolled. Myopic astigmatism was the most common refractive error (40%). Compared with myopic patients, those with myopic astigmatism and hypermetropic astigmatism were four and ten times less likely, respectively, to demonstrate significant improvement in distance visual acuity following optical correction. Managing refractive errors is an important way to reduce eye morbidity-associated low vision in oculocutaneous albino patients.

  5. Refractive error in underserved adults: causes and potential solutions.

    Science.gov (United States)

    Jeganathan, V Swetha E; Robin, Alan L; Woodward, Maria A

    2017-07-01

    To evaluate the epidemiology of uncorrected refractive errors (URE) in adults both in the United States and globally, health outcomes impacted by URE, common barriers to treatment, and propose potential interventions. URE is the main cause of visual impairment and the second leading cause of blindness globally. Rates of URE are rising, and cause disability that reduces productivity, economic earnings, and the quality of life of affected individuals. Economic barriers, healthcare access, and sociocultural constraints are among the most fundamental barriers to correcting URE. However, innovative approaches are poised to lower rates of URE. URE is a leading cause of preventable visual impairment with serious health consequences. Numerous social and financial barriers are associated with the high prevalence of URE in low-income adults. Novel delivery programs for eyeglasses and programs to provide refractive surgery to correct refractive error could decrease rates of URE.

  6. Refractive errors in a Brazilian population: age and sex distribution.

    Science.gov (United States)

    Ferraz, Fabio H; Corrente, José E; Opromolla, Paula; Padovani, Carlos Roberto; Schellini, Silvana A

    2015-01-01

    To determine the prevalence of refractive errors and their distribution according to age and sex in a Brazilian population. This population-based cross-sectional study involved 7654 Brazilian inhabitants of nine municipalities of Sao Paulo State, Brazil, between March 2004 and July 2005. Participants aged >1 year were selected using a random, stratified, household cluster sampling technique, excluding individuals with previous refractive or cataract surgery. Myopia was defined as spherical equivalent (SE) ≤-0.5D, high myopia as SE ≤-3.0D, hyperopia as SE ≥+0.5D, high hyperopia as SE ≥+3D, astigmatism as ≤-0.5DC and anisometropia as ≥1.0D difference between eyes. Age, sex, complaints and a comprehensive eye examination including cycloplegic refraction test were collected and analysed using descriptive analysis, univariate and multivariate methods. The prevalence of astigmatism was 59.7%, hyperopia 33.8% and myopia was 25.3%. Astigmatism had a progressive increase with age. With-the-rule (WTR) axes of astigmatism were more frequently observed in the young participants and the against-the-rule (ATR) axes were more frequent in the older subjects. The onset of myopia occurred more frequently between the 2nd and 3rd decades of life. Anisometropia showed a prevalence of 13.2% (95% CI 12.4-13.9; p refractive error and hyperopia was also associated with sex. Hyperopia was associated with WTR axes (odds ratio 0.73; 95% CI: 0.6-0.8; p prevalent refractive error in a Brazilian population. There was a strong relationship between age and all refractive errors and between hyperopia and sex. WTR astigmatism was more frequently associated with hyperopia and ATR astigmatism with myopia. The vast majority of participants had low-grade refractive error, which favours planning aimed at correction of refractive error in the population. © 2014 The Authors Ophthalmic & Physiological Optics © 2014 The College of Optometrists.

  7. Prevalence of Refractive Error in a Rural Ogoni Community in ...

    African Journals Online (AJOL)

    Results: The prevalence of refractive error was 28.5%. Of this, hypermetropia was seen in 19.2%, while myopia was seen in 9.3% of the cases. Most of the study population (71.5%) were emmetropic. The highest number of emmetropes and hypermetropes occurred in the 20-29 year age group, while most myopes were ...

  8. Management of Refractive Errors And Low Vision Among Basic ...

    African Journals Online (AJOL)

    The study sought to discuss the management of refractive errors and low vision among basic school children in the Atwima district. A sample of 1,177 public basic school children aged between 5-19 years was randomly selected from ten basic schools for examination. Thirteen key informants in the district were purposively ...

  9. Refractive errors in Kaduna, Nigeria | Bagaiya | Nigerian Journal of ...

    African Journals Online (AJOL)

    Conclusion: Refractive error is a common cause of visual impairment among ophthalmic patients in Kaduna. Judicious management of the meagre resources on appropriate lens category, which in this study is presbyopic lens type, cannot be overemphasized. Key Words: Hypermetropia, myopia, astigmatism. Nigerian ...

  10. Refractive Errors in Primary School Children in Nigeria | Faderin ...

    African Journals Online (AJOL)

    The study was carried out to determine the prevalence of refractive errors in primary school children in the Nigerian Army children school. Bonny Camp, Lagos, Nigeria. A total of 919 pupils from two primary schools (one private school and one public school) were screened. The schools and classes were selected using ...

  11. Pattern of Refractive Errors Among Ophthalmic Outpatients of ...

    African Journals Online (AJOL)

    Introduction: Uncorrected refractive error (RE) is the most common cause of visual impairment (VI) in the world. It has significant effects on individuals and community, restricting some educational and occupational employment opportunities of the otherwise healthy individual. A significant percentage of the world population ...

  12. Prevalence of Refractive Error Among school children in Meseret ...

    African Journals Online (AJOL)

    The problem of visual impairment among school children is so prevalent that it greatly reduces children's ability to study and attend classes finally leading to a grave socio economic burden to the society. The study determined the prevalence of refractive error among school children of Meseret General Primary School, ...

  13. refractive error status of patients in bayelsa state, nigeria

    African Journals Online (AJOL)

    Adebayo Adio

    hyperopia (>+0.50D) to be 20.6% in Bangladesh. A recent national survey in Pakistan reported that refractive error is the commonest cause of moderate visual impairment (VA <6/18 to. $6/60) accounting for 43%, followed by cataract. A hospital-based. 8. Correspondence: A Koroye-Egbe, Niger Delta University Teaching ...

  14. Refractive errors among students enrolled in Assiut University, Egypt

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    Mohamed S. H. Massoud

    2015-01-01

    Refractive error is a common cause of visual impairment among the group of adolescents admitted for university education in Upper Egypt. Myopia is particularly more prevalent than that reported in other regions of Egypt and other countries. Early detection and correction is essential to avoid ametropic amblyopia.

  15. Prevalence of refractive error in school children of Karachi.

    Science.gov (United States)

    Alam, Haseeb; Siddiqui, M Irfanullah; Jafri, Syed Imtiaz Ahmed; Khan, Abdul Sattar; Ahmed, Syed Ishtiaq; Jafar, Mohammad

    2008-06-01

    To find out the prevalence of refractive error and the eye morbidity in the school children and the associated factors. One thousand students were selected from different schools of Karachi adopting two stage sampling technique. List of schools was obtained from Board of Secondary Education and 20 schools were randomly selected from the list in the five districts of Karachi during that period. Fifty students from each school were then selected adopting simple random technique. A total of 1000 children from 20 schools were selected. However 940 were examined. The prevalence of refractive error was 8.9%. Mean age of the students was 9.49 +/- 2.5. Dominant ethnic group was Urdu speaking. Only 10.9% children were ever checked for their ophthalmic examination. Refractive error was associated with female sex but no association was found with class, age, ethnicity, parental education and other risk factors. About 1% students were color blind. Lack of association with increasing class may be due to poor educational training at Public sector schools. An increased prevalence of refractive error was found in this study. There is a need of periodical eye examination, preferably while entering and leaving the school.

  16. Refractive errors in children with autism in a developing country ...

    African Journals Online (AJOL)

    Background: In a resource.limited country visual problems of mentally challenged individuals are often neglected. Aim: The present study aims to study refractive errors in children diagnosed with autism in a developing country. Materials and Methods: Ophthalmic examination was carried out on children diagnosed with ...

  17. Pattern Of Refractive Errors At Obafemi Awolowo University ...

    African Journals Online (AJOL)

    The youngest age of presentation for presbyopia was 36 years. Astigmatism occurred in 55.8% of the patients seen. Most of the patients (68.3%) had myopic astigmatism. One of the two patients who had anisometropia had developed amblyopia in the more hypermetropic eye. Conclusion: Since refractive errors were found ...

  18. Contribution of refractive errors to visual impairment in patients at ...

    African Journals Online (AJOL)

    Objective: To determine the contribution of refractive error to visual impairment in visually impaired patients attending Korle-Bu Teaching Hospital, Ghana. Method: This study was conducted over a period of 1 year beginning October 2002 at Korle-Bu Teaching Hospital. Every 4th consecutive new case attending the eye ...

  19. Refractive errors and school performance in Brazzaville, Congo ...

    African Journals Online (AJOL)

    Background: Wearing glasses before ten years is becoming more common in developed countries. In black Africa, for cultural or irrational reasons, this attitude remains exceptional. This situation is a source of amblyopia and learning difficulties. Objective: To determine the role of refractive errors in school performance in ...

  20. Prevalence of Refractive errors among Primary School Pupils in ...

    African Journals Online (AJOL)

    Administrator

    Computer generated random numbers were used to randomly select Kilungu divison from 5 divisions ... 94.4% (1358) had normal vision (=6/18). The prevalence of refractive errors was 5.2% (95% CI). 0. 50. 100. 150 ... all cases of reduced vision (figure 2). This was almost half of what Nzuki et al found in Nairobi's. Langata ...

  1. refractive errors among secondary school students in Isuikwuato

    African Journals Online (AJOL)

    Eyamba

    STUDENTS IN ISUIKWUATO LOCAL GOVERNMENT AREA OF. ABIA STATE, NIGERIA. NELSON CHUKWUDI ... Local Government Area, Abia State, Nigeria was conducted. Pre-tested questionnaires were administered by ... Refractive Error. (ametropia) occurs when parallel rays of light fail to converge to a sharp focus on ...

  2. Prevalence of refractive errors among schoolchildren in rural central Ethiopia.

    Science.gov (United States)

    Mehari, Zelalem Addisu; Yimer, Abdirahman Wollie

    2013-01-01

    The aim of the present study was to assess the prevalence of refractive errors and visual impairment among schoolchildren in rural central Ethiopia. A cross-sectional study was conducted from November 2010 to January 2011 among 5,470 schoolchildren from 14 schools, of whom 4,238 (aged 7-18 years) were screened for refractive errors. In all participants, uncorrected vision and best corrected visual acuity were determined and those with a visual acuity of 6/12 or worse, underwent a complete ophthalmic examination to determine the cause of visual impairment. Myopia was defined as a spherical equivalent of -0.50 dioptre (D) or greater in one or both eyes and hyperopia as a spherical equivalent of +2.00 D or greater. A cylindrical power of -0.50 DC (D cylinder) or greater was considered as astigmatism. Chi-square was used to test differences in proportions. Differences were considered to be statistically significant at the five per cent level. Of the 4,238 children, 405 (9.5 per cent) were visually impaired and of these 267 children were diagnosed as having refractive errors, with an overall prevalence of 6.3 per cent, comprised of 6.1 per cent in boys and 6.6 per cent in girls. Myopia is the most prevalent refractive error; accounting for 6.0 per cent, followed by compound myopic astigmatism 1.2 per cent, then simple myopic astigmatism 0.5 per cent, mixed astigmatism 0.26 per cent and finally hyperopia 0.33 per cent. Reasons for visual acuity of 6/12 or worse in the better eye were found to be refractive error (65.9 per cent), corneal problems (12.8 per cent) and amblyopia (9.6 per cent). The prevalence of manifest strabismus in the study group was 1.1 per cent (n = 45). The study concluded that uncorrected refractive error is a common cause of visual impairment among schoolchildren in rural central Ethiopia. This indicates the need for regular school-screening programs that provide glasses at low cost or free of charge for those who have refractive errors. © 2012 The

  3. Small refractive errors--their correction and practical importance.

    Science.gov (United States)

    Skrbek, Matej; Petrová, Sylvie

    2013-04-01

    Small refractive errors present a group of specifc far-sighted refractive dispositions that are compensated by enhanced accommodative exertion and aren't exhibited by loss of the visual acuity. This paper should answer a few questions about their correction, flowing from theoretical presumptions and expectations of this dilemma. The main goal of this research was to (dis)confirm the hypothesis about convenience, efficiency and frequency of the correction that do not raise the visual acuity (or if the improvement isn't noticeable). The next goal was to examine the connection between this correction and other factors (age, size of the refractive error, etc.). The last aim was to describe the subjective personal rating of the correction of these small refractive errors, and to determine the minimal improvement of the visual acuity, that is attractive enough for the client to purchase the correction (glasses, contact lenses). It was confirmed, that there's an indispensable group of subjects with good visual acuity, where the correction is applicable, although it doesn't improve the visual acuity much. The main importance is to eliminate the asthenopia. The prime reason for acceptance of the correction is typically changing during the life, so as the accommodation is declining. Young people prefer the correction on the ground of the asthenopia, caused by small refractive error or latent strabismus; elderly people acquire the correction because of improvement of the visual acuity. Generally the correction was found useful in more than 30%, if the gain of the visual acuity was at least 0,3 of the decimal row.

  4. Prevalence of refractive error, presbyopia and spectacle coverage in Kahama District, Tanzania: a rapid assessment of refractive error.

    Science.gov (United States)

    Mashayo, Eden R; Chan, Ving Fai; Ramson, Prasidh; Chinanayi, Farai; Naidoo, Kovin S

    2015-01-01

    In Tanzania, the prevalence of refractive error and presbyopia have not been comprehensively assessed, limiting appropriate planning and implementation of delivery of vision care. This study sought to determine the prevalence of refractive error and presbyopia, spectacle coverage and the barriers to uptake of refractive services in people aged 15 years and older in the Kahama district of Tanzania. A cross-sectional community-based survey was conducted using 54 randomly selected clusters. Respondents 15 years and older were interviewed and underwent standardised clinical eye examinations. Uncorrected refractive error (URE) was defined as presenting vision worse than 6/12 that could be corrected to better than 6/12 using a pinhole. Spectacle coverage was defined as the proportion of need that was met (those that improved from unaided vision with their own spectacle correction). A total of 3,230 subjects (99.75 per cent of 3,240 eligible) participated in the study with 57.2 per cent males and the median age of participants was 35 years (inter-quartile range, 24 to 49). The prevalence of visual impairment was 10.4 per cent (95% CI 9.4 to 11.4) and was lower in those who had completed their primary school education (odds ratio (OR) 0.54, 95% CI: 0.40 to 0.72) and highest in subjects 40 years and older (OR 3.17, 95% CI: 2.14 to 4.70) and farmers (OR 8.57 95% CI: 2.27 to 32.43). Refractive error prevalence was 7.5 per cent (95% CI: 6.65 to 8.54) and this was highest in participants over 40 years (OR 1.60, 95% CI: 1.14 to 2.25) and in students (OR 3.64, 95% CI: 1.35 to 9.86). Prevalence of presbyopia was 46.5 per cent (773/1,663, 95% CI: 44.34 to 48.75). Spectacle coverage for refractive error and presbyopia was 1.69% (95% CI: 0 to 3.29) and 0.42% (95% CI: 0 to 1.26), respectively. Uncorrected refractive error is a public health challenge in the Kahama district and sustainable service delivery and health promotion efforts are needed. © 2014 The Authors. Clinical and

  5. Child development and refractive errors in preschool children.

    Science.gov (United States)

    Ibironke, Josephine O; Friedman, David S; Repka, Michael X; Katz, Joanne; Giordano, Lydia; Hawse, Patricia; Tielsch, James M

    2011-02-01

    Many parents are concerned about their child's development. The purpose of this study is to determine whether parental concerns about overall development are associated with significant refractive errors among urban preschool children. A cross-sectional population-based study was conducted to evaluate the prevalence of ocular disorders in white and African American children aged 6 through 71 months in Baltimore, Maryland. A comprehensive eye examination with cycloplegic refraction was performed. Parental concerns about development were measured with the Parents' Evaluation of Developmental Status screening tool. Of 2546 eligible children 2381 (93.5%), completed the refraction and the parental interview. Parental concerns about development were present in 510 of the 2381 children evaluated [21.4%; 95% confidence intervals (CI): 9.8 to 23.1]. The adjusted odds ratios [OR] of parental concerns with hyperopia [≥3.00 diopters (D)] was 1.26 (95% CI: 0.90 to 1.74), with myopia (≥1.00 D) was 1.29 (95% CI: 0.83 to 2.03), with astigmatism (≥1.50 D) was 1.44 (95% CI: 1.08 to 1.93) irrespective of the type of astigmatism, and with anisometropia (≥2.00 D) was 2.61 (95% CI: 1.07 to 6.34). The odds of parental concerns about development significantly increased in children older than 36 months with hyperopia ≥3.00 D, astigmatism ≥1.50 D, or anisometropia ≥2.00 D. Parental concerns about general developmental problems were associated with some types of refractive error, astigmatism ≥1.50 D and anisometropia ≥2.00 D, in children aged 6 to 71 months. Parental concerns were also more likely in children older than 36 months with hypermetropia, astigmatism, or anisometropia. Parental concerns were not associated with myopia. Because of the potential consequences of uncorrected refractive errors, children whose parents have expressed concerns regarding development should be referred for an eye examination with cycloplegic refraction to rule out significant refractive

  6. Heritability and familial aggregation of refractive error in the Old Order Amish.

    Science.gov (United States)

    Peet, Jon A; Cotch, Mary-Frances; Wojciechowski, Robert; Bailey-Wilson, Joan E; Stambolian, Dwight

    2007-09-01

    To determine the heritability of refractive error and familial aggregation of myopia and hyperopia in an elderly Old Order Amish (OOA) population. Nine hundred sixty-seven siblings (mean age, 64.2 years) in 269 families were recruited for the Amish Eye Study in the Lancaster County area of Pennsylvania. Refractive error was determined by noncycloplegic manifest refraction. Heritability of refractive error was estimated with multivariate linear regression as twice the residual sibling-sibling correlation after adjustment for age and gender. Logistic regression models were used to estimate the sibling recurrence odds ratio (OR(s)). Myopia and hyperopia were defined with five different thresholds. The age- and gender-adjusted heritability of refractive error was 70% (95% CI: 48%-92%) in the OOA. Age and gender-adjusted OR(s) and sibling recurrence risk (lambda(s)), with different thresholds defining myopia ranged from 3.03 (95% CI: 1.58-5.80) to 7.02 (95% CI: 3.41-14.46) and from 2.36 (95% CI: 1.65-3.19) to 5.61 (95% CI: 3.06-9.34). Age and gender-adjusted OR(s) and lambda(s) for different thresholds of hyperopia ranged from 2.31 (95% CI: 1.56-3.42) to 2.94 (95% CI: 2.04-4.22) and from 1.33 (95% CI: 1.22-1.43) to 1.85 (95% CI: 1.18-2.78), respectively. Women were significantly more likely than men to have hyperopia. There was no significant gender difference in the risk of myopia. In the OOA, refractive error is highly heritable. Hyperopia and myopia aggregate strongly in OOA families.

  7. Refractive errors in Cameroonians diagnosed with complete oculocutaneous albinism

    Directory of Open Access Journals (Sweden)

    Eballé AO

    2013-07-01

    Full Text Available André Omgbwa Eballé1,3, Côme Ebana Mvogo2, Christelle Noche4, Marie Evodie Akono Zoua2, Andin Viola Dohvoma21Faculty of Medicine and Pharmaceutical Sciences, University of Douala, Douala, Cameroon, 2Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé, Cameroon; 3Yaoundé Gynaeco-obstetric and Paediatric Hospital. Yaoundé, Cameroon; 4Faculty of Medicine, Université des Montagnes. Bangangté, CameroonBackground: Albinism causes significant eye morbidity and amblyopia in children. The aim of this study was to determine the refractive state in patients with complete oculocutaneous albinism who were treated at the Gynaeco-Obstetric and Paediatric Hospital, Yaoundé, Cameroon and evaluate its effect on vision.Methods: We carried out this retrospective study at the ophthalmology unit of our hospital. All oculocutaneous albino patients who were treated between March 1, 2003 and December 31, 2011 were included.Results: Thirty-five patients (70 eyes diagnosed with complete oculocutaneous albinism were enrolled. Myopic astigmatism was the most common refractive error (40%. Compared with myopic patients, those with myopic astigmatism and hypermetropic astigmatism were four and ten times less likely, respectively, to demonstrate significant improvement in distance visual acuity following optical correction.Conclusion: Managing refractive errors is an important way to reduce eye morbidity-associated low vision in oculocutaneous albino patients.Keywords: albinism, visual acuity, refraction, Cameroon

  8. LASIK for spherical refractive myopia: effect of topographic astigmatism (ocular residual astigmatism, ORA) on refractive outcome.

    Science.gov (United States)

    Frings, Andreas; Richard, Gisbert; Steinberg, Johannes; Skevas, Christos; Druchkiv, Vasyl; Katz, Toam; Linke, Stephan J

    2015-01-01

    In eyes with a preoperative plano refractive cylinder, it would appear that there is no rationale for astigmatic treatment. The aim of this retrospective, cross-sectional data analysis was to determine the amount of topographic astigmatism in refractive plano eyes that results in reduced efficacy after myopic laser in situ keratomileusis (LASIK). This study included 267 eyes from 267 consecutive myopic patients with a refractive plano cylinder. Receiver operating characteristic analysis was used to find the cut-off values of preoperative ocular residual astigmatism (= topographic astigmatism) that can best discriminate between groups of efficacy and safety indices in preoperative plano refractive cylinder eyes. Preoperative ocular residual astigmatism (ORA) (or topographic astigmatism) of ≤0.9 diopters (D) resulted in an efficacy index of at least 0.8 statistically significantly more frequently than eyes with a preoperative ORA of >0.9 D. Eyes with a high ORA preoperatively also had a high ORA postoperatively. Regression analysis showed that each diopter of preoperative ORA reduced efficacy by 0.07. A preoperative corneal astigmatism of ≥0.9 D could (partially) be taken into account in the LASIK design, even if the subjective refractive astigmatism is neutral.

  9. LASIK for spherical refractive myopia: effect of topographic astigmatism (ocular residual astigmatism, ORA on refractive outcome.

    Directory of Open Access Journals (Sweden)

    Andreas Frings

    Full Text Available In eyes with a preoperative plano refractive cylinder, it would appear that there is no rationale for astigmatic treatment. The aim of this retrospective, cross-sectional data analysis was to determine the amount of topographic astigmatism in refractive plano eyes that results in reduced efficacy after myopic laser in situ keratomileusis (LASIK.This study included 267 eyes from 267 consecutive myopic patients with a refractive plano cylinder. Receiver operating characteristic analysis was used to find the cut-off values of preoperative ocular residual astigmatism (= topographic astigmatism that can best discriminate between groups of efficacy and safety indices in preoperative plano refractive cylinder eyes.Preoperative ocular residual astigmatism (ORA (or topographic astigmatism of ≤0.9 diopters (D resulted in an efficacy index of at least 0.8 statistically significantly more frequently than eyes with a preoperative ORA of >0.9 D. Eyes with a high ORA preoperatively also had a high ORA postoperatively. Regression analysis showed that each diopter of preoperative ORA reduced efficacy by 0.07.A preoperative corneal astigmatism of ≥0.9 D could (partially be taken into account in the LASIK design, even if the subjective refractive astigmatism is neutral.

  10. The Social and Economic Impact of Refractive Error in Mozambique

    OpenAIRE

    Thompson, Stephen James

    2014-01-01

    The purpose of this thesis is to investigate potential key determinants of the success, or otherwise, of endeavours to address avoidable Visual Impairment (VI) by addressing Uncorrected Refractive Error (URE) in Mozambique and the wider region of sub-Saharan Africa by providing optometric services. It includes a Cost Benefit Analysis (CBA) of a higher education optometry training programme, barriers that might prevent the realisation of overarching goals despite a successful training programm...

  11. A STUDY ON PREVALENCE OF REFRACTIVE ERRORS IN SCHOOL CHILDREN

    OpenAIRE

    Kolli Sree Karuna

    2014-01-01

    ‘’Sarvendriya nam nayanam pradhanam” Of all the organs in the body, eyes are the most important. The blindness or defect in vision decreases the productivity of the nation in addition to increased dependability. The refractive errors in the school children throw them in to defective future. Nutrition deficiency, mental strain, wrong reading habits etc are some of the causes for this defect in these children. Vision is essential for all the children, for the academic and overal...

  12. Refractive error in Nigerian adults: prevalence, type, and spectacle coverage.

    Science.gov (United States)

    Ezelum, Christian; Razavi, Hessom; Sivasubramaniam, Selvaraj; Gilbert, Clare E; Murthy, Gudlavalleti V S; Entekume, Gabriel; Abubakar, Tafida

    2011-07-23

    To provide data on prevalence and types of refractive error and the spectacle-wearing rate among adults in Nigeria and the degree to which the need for distance correction could be met by off-the-shelf spectacles. Multistage, stratified, cluster random sampling with probability proportional to size was used to identify a nationally representative sample of 15,027 persons aged ≥40 years. Distance vision was measured using a reduced logMAR tumbling-E chart. All participants underwent autorefraction, and those with presenting acuity of refractive error was responsible for 77.9% of mild visual impairment (prevalence of myopia (≤0.5 D) and high myopia (≤5.0 D) were 16.2% and 2.1%, respectively. Spectacles could improve the vision of 1279 (9.4%) and 882 (6.5%) participants at the 6/12 and 6/18 level, respectively, but only 3.4% and 4.4% of these individuals wore spectacles to the examination site. Approximately 2,140,000 adults in Nigeria would benefit from spectacles that improved their vision from refractive errors are an important cause of visual impairment in Nigeria, and services must be dramatically improved to meet the need.

  13. Refractive errors and amblyopia in children entering school: Shahrood, Iran.

    Science.gov (United States)

    Jamali, Payman; Fotouhi, Akbar; Hashemi, Hassan; Younesian, Masud; Jafari, Alireza

    2009-04-01

    To determine the prevalence of amblyopia, strabismus, and refractive errors in children entering school. In this cross-sectional population-based study, 6-year-old children enrolling in Shahrood schools were randomly sampled. Those with organic blindness or mental retardation were excluded. Ocular alignment, visual acuity, stereopsis, cover testing, and cycloplegic refraction were recorded for all children by an optometrist. A diagnosis of amblyopia was based on a best-corrected visual acuity of 6/12 or less in one or both eyes, or a bilateral difference of at least two best-corrected visual acuity lines. A total of 902 children were invited for optometry examinations, among which 827 (91.7%) responded and 815 children (98.5%) were included in the study. The prevalence of significantly reduced visual acuity (uncorrected VA amblyopia was 3.6 and 1.7%, respectively. The prevalence of hyperopia (+2.00 D or worse), myopia (-0.50 D or worse), astigmatism (0.75 D or worse), and anisometropia (1.00 D or more) were 20.5, 1.7, 19.6, and 2.2%, respectively. Significant refractive error, defined as hyperopia >+3.50 D, myopia >-3.00 D, astigmatism >1.50 D in the orthogonal meridian or >1.00 D in the oblique meridian, or anisometropia (hyperopic >1.00 D, myopic >3.00 D) was detected in 2.1, 0.1, 5.0, and 0.9% of the sample, respectively. Strabismus was diagnosed in 1.2% of children. Overall, 52 children (6.4%; 95% confidence interval [CI], 4.7-8.1%) were at risk of amblyopia; of these, 81% had significant refractive errors, 11% had strabismus, and 8% had both. A considerable proportion of 6-year-old children have strabismus and/or significant, potentially amblyogenic refractive errors. The relatively high rate of hyperopia and astigmatism in the studied population needs more attention. The results of the study emphasize the need for adequate diagnostic and therapeutic eye care services for preschool children.

  14. Prevalence of Amblyopia and Refractive Errors Among Primary School Children

    Science.gov (United States)

    Rajavi, Zhale; Sabbaghi, Hamideh; Baghini, Ahmad Shojaei; Yaseri, Mehdi; Moein, Hamidreza; Akbarian, Shadi; Behradfar, Narges; Hosseini, Simin; Rabei, Hossein Mohammad; Sheibani, Kourosh

    2015-01-01

    Purpose: To determine the prevalence of amblyopia and refractive errors among 7 to 12-year-old primary school children in Tehran, Iran. Methods: This population-based cross-sectional study included 2,410 randomly selected students. Visual acuity was tested using an E-chart on Yang vision tester. Refractive errors were measured by photorefractometry and cycloautorefraction. Strabismus was checked using cover test. Direct ophthalmoscopy was used to assess the anterior segment, lens opacities, red reflex and fundus. Functional amblyopia was defined as best corrected visual acuity ≤20/40 in one or both eyes with no anatomical problems. Results: Amblyopia was present in 2.3% (95% CI: 1.8% to 2.9%) of participants with no difference between the genders. Amblyopic subjects were significantly younger than non-amblyopic children (P=0.004). Overall, 15.9% of hyperopic and 5.9% of myopic cases had amblyopia. The prevalence of hyperopia ≥+2.00D, myopia ≤-0.50D, astigmatism ≥0.75D, and anisometropia (≥1.00D) was 3.5%, 4.9%, 22.6%, and 3.9%, respectively. With increasing age, the prevalence of myopia increased (Prefractive errors, especially anisometropia (OR=12.87) and hyperopia (OR=11.87), were important amblyogenic risk factors. Conclusion: The high prevalence of amblyopia in our subjects in comparison to developed countries reveals the necessity of timely and sensitive screening methods. Due to the high prevalence of amblyopia among children with refractive errors, particularly high hyperopia and anisometropia, provision of glasses should be specifically attended by parents and supported by the Ministry of Health and insurance organizations. PMID:27051485

  15. Prevalence of Amblyopia and Refractive Errors Among Primary School Children.

    Science.gov (United States)

    Rajavi, Zhale; Sabbaghi, Hamideh; Baghini, Ahmad Shojaei; Yaseri, Mehdi; Moein, Hamidreza; Akbarian, Shadi; Behradfar, Narges; Hosseini, Simin; Rabei, Hossein Mohammad; Sheibani, Kourosh

    2015-01-01

    To determine the prevalence of amblyopia and refractive errors among 7 to 12-year-old primary school children in Tehran, Iran. This population-based cross-sectional study included 2,410 randomly selected students. Visual acuity was tested using an E-chart on Yang vision tester. Refractive errors were measured by photorefractometry and cycloautorefraction. Strabismus was checked using cover test. Direct ophthalmoscopy was used to assess the anterior segment, lens opacities, red reflex and fundus. Functional amblyopia was defined as best corrected visual acuity ≤20/40 in one or both eyes with no anatomical problems. Amblyopia was present in 2.3% (95% CI: 1.8% to 2.9%) of participants with no difference between the genders. Amblyopic subjects were significantly younger than non-amblyopic children (P=0.004). Overall, 15.9% of hyperopic and 5.9% of myopic cases had amblyopia. The prevalence of hyperopia ≥+2.00D, myopia ≤-0.50D, astigmatism ≥0.75D, and anisometropia (≥1.00D) was 3.5%, 4.9%, 22.6%, and 3.9%, respectively. With increasing age, the prevalence of myopia increased (Pprevalence of amblyopia in our subjects in comparison to developed countries reveals the necessity of timely and sensitive screening methods. Due to the high prevalence of amblyopia among children with refractive errors, particularly high hyperopia and anisometropia, provision of glasses should be specifically attended by parents and supported by the Ministry of Health and insurance organizations.

  16. The prevalence and risk indicators of uncorrected refractive error and unmet refractive need in Latinos: the Los AngelesLatino Eye Study.

    Science.gov (United States)

    Varma, Rohit; Wang, Michelle Y; Ying-Lai, Mei; Donofrio, Jill; Azen, Stanley P

    2008-12-01

    To determine the age- and sex-specific prevalence and risk indicators of uncorrected refractive error and unmet refractive need among a population-based sample of Latino adults. Self-identified Latinos 40 years of age and older (n = 6129) from six census tracts in La Puente, California, underwent a complete ophthalmic examination, and a home-administered questionnaire provided self-reported data on potential risk indicators. Uncorrected refractive error was defined as a >or=2-line improvement with refraction in the better seeing eye. Unmet refractive need was defined as having or=20/40 after refraction (definition 1) or having or=2-line improvement with refraction (definition 2). Sex- and age-specific prevalence and significant risk indicators for uncorrected refractive error and unmet refractive need were calculated. The overall prevalence of uncorrected refractive error was 15.1% (n = 926). The overall prevalence of unmet refractive need was 8.9% (n = 213, definition 1) and 9.6% (n = 218, definition 2). The prevalence of uncorrected refractive error and either definition of unmet refractive need increased with age (P refractive error and unmet refractive need. The data suggest that the prevalence of uncorrected refractive error and unmet refractive need is high in Latinos of primarily Mexican ancestry. Better education and access to care in older Latinos are likely to decrease the burden of uncorrected refractive error in Latinos.

  17. Population density and refractive error among Chinese children.

    Science.gov (United States)

    Zhang, Mingzhi; Li, Liping; Chen, Lizhen; Lee, Jack; Wu, Jiasi; Yang, Amy; Chen, Connie; Xu, Daocheng; Lam, Dennis S C; Sharma, Abhishek; Griffiths, Sian; Gao, Yang; Congdon, Nathan

    2010-10-01

    China is urbanizing rapidly, and the prevalence of myopia is high. This study was conducted to identify the reasons for observed differences in the prevalence of myopia among urban versus rural Chinese children. All children with uncorrected acuity of 6/12 or worse and a 50% random sample of children with vision better than 6/12 at all secondary schools in mixed rural-urban Liangying Township, Guangdong, underwent cycloplegic refraction, and provided data on age, gender, parental education, weekly near work and time outdoors, and urban development level of respondents' neighborhoods (12-item questionnaire). Population density of 32 villages and urban zones in Liangying was calculated from census figures (mean population density, 217 persons/km(2); range, 94-957; mean for Guangdong, 486). Among 5844 eligible children, 4612 (78.9%) had parental consent and completed examinations; 2957 were refracted per protocol, and 2480 (83.9%) of these had questionnaire data. Those with completed examinations were more likely to be girls (P population density (P = 0.003), but not development index, parental education, or time outdoors were significantly associated with more myopic refractive error. Higher population density appears to be associated with myopia risk, independent of academic activity, time spent outdoors, familial educational level, or economic development, factors that have been thought to explain higher myopia prevalence among urban children. Mechanisms for this apparent association should be sought.

  18. Uncorrected Refractive Error in a Latino Population: Proyecto VER

    Science.gov (United States)

    Uribe, Jorge A.; Swenor, Bonnielin K.; Muñoz, Beatriz E.; West, Sheila K.

    2010-01-01

    Purpose To determine the prevalence of refractive error (RE), and the proportion of those with uncorrected refractive error and factors associated with uncorrected RE in Latino adults. Design Population-based, cross-sectional study. Participants A random sample of 4,509 Latinos ≥40 years from Tucson and Nogales, Arizona with both ophthalmic evaluation and questionnaire were included in these analyses. Methods A case of RE was defined as subject wearing prescription glasses for distance vision whose presenting visual acuity (PVA) was 20/25 or better, or subject with PVA worse than 20/25 in at least one eye who improved ≥2 lines after subjective refraction and whose refractive correction met these cutoffs: sphere 1.0D or cylinder ≥+1.0D. Among those with RE, those who on refraction achieved ≥2 line improvement in at least one eye (definition 1) or in both eyes (definition 2) were classified as uncorrected RE. A questionnaire on access to care, acculturation, perceived barriers, income, and education was asked. Main Outcome Measures Prevalence of RE and proportion of uncorrected RE Results The overall prevalence of RE in at least one eye was 64%, and in both eyes was 51%. Of participants with RE in at least one eye, 35% have uncorrected RE. Of those with RE in both eyes, 19% have uncorrected RE. As compared to those with corrected RE, those with uncorrected RE in at least one eye were more likely to have lower levels of acculturation (Odds Ratio [OR]=1.2; 95% Confidence Interval [CI]: 1.1–1.4 per unit decrease) and education (OR=1.6 for ≤6 years vs. >12 years; 95% CI: 1.2–2.2). Uncorrected RE was also significantly associated with not having insurance (OR=1.4; 95% CI: 1.1–1.6), a low family income (OR=1.4; 95% CI: 1.1–1.7 1 year vs. <6 months). Conclusions In our sample of Latinos the overall proportion of uncorrected RE is high, and suggests that one third of those with RE may benefit from a new pair of glasses. Indices of marginalization are

  19. Refractive status and prevalence of refractive errors in suburban school-age children.

    Science.gov (United States)

    Pi, Lian-Hong; Chen, Lin; Liu, Qin; Ke, Ning; Fang, Jing; Zhang, Shu; Xiao, Jun; Ye, Wei-Jiang; Xiong, Yan; Shi, Hui; Yin, Zheng-Qin

    2010-10-18

    This study investigated the distribution pattern of refractive status and prevalence of refractive errors in school-age children in Western China to determine the possible environmental factors. A random sampling strategy in geographically defined clusters was used to identify children aged 6-15 years in Yongchuan, a socio-economically representative area in Western China. We carried out a door-to-door survey and actual eye examinations, including visual acuity measurements, stereopsis examination, anterior segment and eyeball movements, fundus examinations, and cycloplegic retinoscopy with 1% cyclopentolate. A total of 3469 children living in 2552 households were selected, and 3070 were examined. The distributions of refractive status were positively-skewed for 6-8-year-olds, and negatively-skewed for 9-12 and 13-15-year-olds. The prevalence of hyperopia (≥+2.00 D spherical equivalent [SE]), myopia (≤-0.50 D SE), and astigmatism (≥1.00 diopter of cylinder [DC]) were 3.26%, 13.75%, and 3.75%, respectively. As children's ages increased, the prevalence rate of hyperopia decreased (PChildren in academically challenging schools had a higher risk of myopia (Prefractive status changes gradually from positively-skewed to negatively-skewed distributions as age increases, with 9-year-old being the critical age for the changes. Environmental factors and study intensity influence the occurrence and development of myopia.

  20. Prevalence of refractive error in Singaporean Chinese children: the strabismus, amblyopia, and refractive error in young Singaporean Children (STARS) study.

    Science.gov (United States)

    Dirani, Mohamed; Chan, Yiong-Huak; Gazzard, Gus; Hornbeak, Dana Marie; Leo, Seo-Wei; Selvaraj, Prabakaran; Zhou, Brendan; Young, Terri L; Mitchell, Paul; Varma, Rohit; Wong, Tien Yin; Saw, Seang-Mei

    2010-03-01

    To determine the prevalence of refractive error types in Singaporean Chinese children aged 6 to 72 months. The Strabismus, Amblyopia and Refractive Error in Singaporean Children (STARS) is a population-based study in southwest Singapore. Door-to-door recruitment of participants was used, with disproportionate random sampling in 6-month increments. Parental questionnaires were administered. Participant eye examinations included logMAR visual acuity, cycloplegic autorefraction, and ocular biometry. Overall and age-specific prevalences of myopia (spherical equivalence [SE] or= +3.00 D), astigmatism (cylinder >or= +1.50 D), and anisometropia (SE difference between each eye >or=2.00 D) were calculated. A total of 3009 children were examined (participation rate, 72.3%). Right eye (OD) cycloplegia data were available for 1375 boys and 1264 girls (mean age, 41 months). Mean OD SE was +0.69 D (SD 1.15). Overall myopia prevalence was 11.0% with no variance between the sexes (P = 0.91). The prevalence of high myopia (at least -6.00 D) was 0.2%. The prevalences of hyperopia, astigmatism, and anisometropia were 1.4%, 8.6%, and 0.6%, respectively. Most astigmatism (>95%) was with-the-rule (cylinder axes between 1 degrees and 15 degrees or 165 degrees and 180 degrees ). Myopia was present in 15.8%, 14.9%, 20.2%, 8.6%, 7.6%, and 6.4% of children aged 6 to 11, 12 to 23, 24 to 35, 36 to 47, 48 to 59, and 60 to 72 months, respectively. Prevalence increased with age for astigmatism (P prevalences of myopia and astigmatism in young Singaporean Chinese children are high, but that of hyperopia is low. Age effects were observed for each refractive error category, but differences between the sexes were not significant. Age-related variation in myopia prevalence may be influenced by ocular development, environment, and/or testability.

  1. Prevalence of amblyopia and refractive errors among primary school children

    Directory of Open Access Journals (Sweden)

    Zhale Rajavi

    2015-01-01

    Results: Amblyopia was present in 2.3% (95% CI: 1.8% to 2.9% of participants with no difference between the genders. Amblyopic subjects were significantly younger than non-amblyopic children (P=0.004. Overall, 15.9% of hyperopic and 5.9% of myopic cases had amblyopia. The prevalence of hyperopia ≥+2.00D, myopia ≤-0.50D, astigmatism ≥0.75D, and anisometropia (≥1.00D was 3.5%, 4.9%, 22.6%, and 3.9%, respectively. With increasing age, the prevalence of myopia increased (P<0.001, that of hyperopia decreased (P=0.007, but astigmatism showed no change. Strabismus was found in 2.3% of cases. Strabismus (OR=17.9 and refractive errors, especially anisometropia (OR=12.87 and hyperopia (OR=11.87, were important amblyogenic risk factors. Conclusion: The high prevalence of amblyopia in our subjects in comparison to developed countries reveals the necessity of timely and sensitive screening methods. Due to the high prevalence of amblyopia among children with refractive errors, particularly high hyperopia and anisometropia, provision of glasses should be specifically attended by parents and supported by the Ministry of Health and insurance organizations.

  2. Effects of different types of refractive errors on bilateral amblyopia

    Directory of Open Access Journals (Sweden)

    Mücella Arıkan Yorgun

    2012-12-01

    Full Text Available Objectives: Identifying effects of different types of refractiveerrors on final visual acuity and stereopsis levels inpatients with bilateral amblyopia.Materials and methods: Patients with bilateral amblyopialower than ≥1.5 D anisometropia were included. Thepatients were classified according to the level of sphericalequivalent (0-4 D and >4 D of hypermetropia, the levelof astigmatism (below and above 2D in positive cylinderand type of composed refractive error [ 4 D of hypermetropiaand 2 D of astigmatism (group III]. Initialand final binocular best corrected visual acuities (BCVAwere compared between groups.Results: The initial binocular BCVA levels were significantlylower in patients with > 4 D of hypermetropia(p=0.028, without correction after treatment (p=0.235.The initial binocular BCVA was not different betweenastigmatism groups, but final BCVA levels were significantlylower in 4-6D of astigmatism compared with 2-4D of astigmatism (p=0.001. During comparison of composedrefractive errors, only the initial binocular BCVAwas significantly lower in group I compared to group II(p=0.015. The final binocular BCVA levels were not differentbetween groups I and III (p>0.05.Conclusions: Although the initial BCVA is lower in patientswith higher levels of hypermetropia, the response ofpatients to treatment with glasses is good. The responseof patients with high levels of astigmatism seems to belimited. J Clin Exp Invest 2012; 3(4: 467-471Key words: Amblyopia, isoametropic amblyopia, hypermetropia,refractive amblyopia, visual acuity

  3. The distribution of refractive errors among children attending Lumbini Eye Institute, Nepal.

    Science.gov (United States)

    Rai, S; Thapa, H B; Sharma, M K; Dhakhwa, K; Karki, R

    2012-01-01

    Uncorrected refractive error is an important cause of childhood blindness and visual impairment. To describe the patterns of refractive errors among children attending the outpatient clinic at the Department of Pediatric Ophthalmology, Lumbini Eye Institute, Bhairahawa, Nepal. Records of 133 children with refractive errors aged 5 - 15 years from both the urban and rural areas of Nepal and the adjacent territory of India attending the hospital between September and November 2010 were examined for patterns of refractive errors. The SPSS statistical software was used to perform data analysis. The commonest type of refractive error among the children was astigmatism (47 %) followed by myopia (34 %) and hyperopia (15 %). The refractive error was more prevalent among children of both the genders of age group 11-15 years as compared to their younger counterparts (RR = 1.22, 95 % CI = 0.66 - 2.25). The refractive error was more common (70 %) in the rural than the urban children (26 %). The rural females had a higher (38 %) prevalence of myopia than urban females (18 %). Among the children with refractive errors, only 57 % were using spectacles at the initial presentation. Astigmatism is the commonest type of refractive error among the children of age 5 - 15 years followed by hypermetropia and myopia. Refractive error remains uncorrected in a significant number of children. © NEPjOPH.

  4. Effect of chalazion excision on refractive error and corneal topography.

    Science.gov (United States)

    Bagheri, Abbas; Hasani, Hamid R; Karimian, Farid; Abrishami, Mohammad; Yazdani, Shahin

    2009-01-01

    To evaluate refractive and corneal topographic changes following excision of chalazia. This prospective noncomparative quasi-experimental clinical trial includes consecutive patients older than 7 years with chalazia of minimum duration of 1 month who underwent excision of the lesions by an internal or external approach. Overall, 253 lids from 228 eyes of 195 patients including 110 female subjects with mean age of 31-/+14 years (range 7-71) were studied. Mean duration of presenting symptoms was 4-/+2.8 months (range 1-24). Lesions were equally distributed in medial, central, and lateral areas of the eyelids. The chalazia were single in 172 (88.2%) and multiple in 23 (11.8%) patients. Mean change in best-corrected visual acuity, spherical equivalent refractive error, and difference of keratometry (corneal astigmatism) were 0.0004-/+0.007 logMAR (p=0.3), -0.06-/+0.6 D (p=0.1), and 0.34-/+0.35 (pChalazion excision can decrease corneal astigmatism and irregularity, which is more prominent in single, firm, and central upper lid lesions. These findings may have implications in pediatric patients at risk for amblyopia.

  5. Uncorrected refractive errors, presbyopia and spectacle coverage in Kamuli District, Uganda

    OpenAIRE

    Naomi Nsubuga; Prasidh Ramson; Pirindha Govender; VingFai Chan; Mary Wepo; Kovin S. Naidoo

    2016-01-01

    Background: Successful refractive error programmes arise from evidence that can be collected cost effectively and timely. Aim: To investigate the prevalence of uncorrected refractive error (URE), presbyopia and spectacle coverage in the Kamuli district, Uganda. Setting: The study was conducted in the Kamuli district in Uganda. Methods: The Rapid Assessment of Refractive Error (RARE) study design is a communitybased cross-sectional study using multistage cluster random sampling to ...

  6. Prevalence of Uncorrected Refractive Error and Other Eye Problems Among Urban and Rural School Children

    OpenAIRE

    Padhye, Amruta S.; Khandekar, Rajiv; Dharmadhikari, Sheetal; Dole, Kuldeep; Gogate, Parikshit; Deshpande, Madan

    2009-01-01

    Background: Uncorrected refractive error is an avoidable cause of visual impairment. Aim: To compare the magnitude and determinants of uncorrected refractive error, such as age, sex, family history of refractive error and use of spectacles among school children 6-15 years old in urban and rural Maharashtra, India. Study Design: This was a review of school-based vision screening conducted in 2004-2005. Materials and Methods: Optometrists assessed visual acuity, amblyopia and strabismus ...

  7. Prevalence of refractive errors among school children in Northeastern Iran.

    Science.gov (United States)

    Rezvan, Farhad; Khabazkhoob, Mehdi; Fotouhi, Akbar; Hashemi, Hassan; Ostadimoghaddam, Hadi; Heravian, Javad; Azizi, Elham; Khorasani, Abbas Azimi; Yekta, Abbas Ali

    2012-01-01

    To determine the prevalence of refractive errors among schoolchildren in Northeastern Iran by age and gender. Using multistage random cluster sampling, 2020 schoolchildren 6-17 years of age were selected for this cross-sectional study. The participants totalled 1551 (response rate 76.8%) elementary and junior high school children (41.5% boys and 58.5% girls) from the northeast of Iran. Cycloplegic autorefraction was used to determine refractive error. Myopia was defined as a spherical equivalent (SE) of -0.50 dioptre (D) or worse, hyperopia as a SE of +2.00 D or more, and astigmatism as cylinder equal to or worse than -0.75 D. The prevalence of uncorrected, habitual and optimal visual acuity of 6/12 (0.30 logMAR) or worse in the better eye was 2.2%, 1.0%, and 0.2% respectively. The prevalence rates of myopia, hyperopia and astigmatism were 4.3% (95%CI: 3.3-5.3), 5.4% (95%CI: 4.3-6.5) and 11.5% (95%CI: 9.9-13.1) respectively and were not related to gender. The prevalence of myopia and against-the-rule astigmatism increased significantly with age (p prevalence of hyperopia significantly decreased with age (p prevalence of myopia in schoolchildren in Northeastern Iran is considerably lower than that of East Asian populations, but similar to many other populations, including South Africa, Chile and other countries of the Middle East. Whilst comparisons with other studies show that the prevalence of hyperopia and astigmatism in Northeastern Iran is higher than that of some countries, it is lower compared with others. Ophthalmic & Physiological Optics © 2011 The College of Optometrists.

  8. Parental myopia, near work, school achievement, and children's refractive error.

    Science.gov (United States)

    Mutti, Donald O; Mitchell, G Lynn; Moeschberger, Melvin L; Jones, Lisa A; Zadnik, Karla

    2002-12-01

    To quantify the degree of association between juvenile myopia and parental myopia, near work, and school achievement. Refractive error, parental refractive status, current level of near activities (assumed working distance-weighted hours per week spent studying, reading for pleasure, watching television, playing video games or working on the computer), hours per week spent playing sports, and level of school achievement (scores on the Iowa Tests of Basic Skills [ITBS]) were assessed in 366 eighth grade children who participated in the Orinda Longitudinal Study of Myopia in 1991 to 1996. Children with myopia were more likely to have parents with myopia; to spend significantly more time studying, more time reading, and less time playing sports; and to score higher on the ITBS Reading and Total Language subtests than emmetropic children (chi(2) and Wilcoxon rank-sum tests; P effects between parental myopia, near work, sports activity, and school achievement, suggesting that each factor has an independent association with myopia. The multivariate odds ratio (95% confidence interval) for two compared with no parents with myopia was 6.40 (2.17-18.87) and was 1.020 (1.008-1.032) for each diopter-hour per week of near work. Interactions between parental myopia and near work were not significant (P = 0.67), indicating no increase in the risk associated with near work with an increasing number of parents with myopia. Heredity was the most important factor associated with juvenile myopia, with smaller independent contributions from more near work, higher school achievement, and less time in sports activity. There was no evidence that children inherit a myopigenic environment or a susceptibility to the effects of near work from their parents.

  9. A survey of the prevalence of refractive errors among children in ...

    African Journals Online (AJOL)

    Background : Refractive errors are a known cause of visual impairment and may cause blindness worldwide. In children, refractive errors may prevent those afflicted from progressing with their studies. In Uganda, like in many developing countries, there is no established vision-screening programme for children on ...

  10. Ocular Co-morbidity in Patients with Refractive Errors in Nigeria ...

    African Journals Online (AJOL)

    Purpose: To d etermine the p attern and p revalence of other ocu lar p roblems seen in p atients with refractive errors in a Nigerian teaching hosp ital. Methods: A retrosp ective hosp ital-based review of all consecu tive p atients who p resented with signs and symp toms of refractive errors at the Obafemi Awolowo University ...

  11. Prevalence of Refractive errors in Primary school children in a rural ...

    African Journals Online (AJOL)

    Prevalence of Refractive errors in Primary school children in a rural community in Ebonyi state of Nigeria. ... International Journal of Medicine and Health Development ... This study aimed to screen primary school children in two rural primary schools in Nchokko Community of Igbeagu Izzi, Ebonyi State for refractive errors.

  12. An international collaborative family-based whole genome quantitative trait linkage scan for myopic refractive error

    DEFF Research Database (Denmark)

    Abbott, Diana; Li, Yi-Ju; Guggenheim, Jeremy A

    2012-01-01

    To investigate quantitative trait loci linked to refractive error, we performed a genome-wide quantitative trait linkage analysis using single nucleotide polymorphism markers and family data from five international sites.......To investigate quantitative trait loci linked to refractive error, we performed a genome-wide quantitative trait linkage analysis using single nucleotide polymorphism markers and family data from five international sites....

  13. Magnitude and determinants of refractive error among school children of two districts of Kathmandu, Nepal

    Directory of Open Access Journals (Sweden)

    Srijana Adhikari

    2013-01-01

    Conclusions: Refractive error is of public health magnitude among school children of 14-16 years of age. School screening program in countries like Nepal for early detection of treatable disease is useful to detect and correct refractive error in older students.

  14. Refractive error and monocular viewing strengthen the hollow-face illusion.

    Science.gov (United States)

    Hill, Harold; Palmisano, Stephen; Matthews, Harold

    2012-01-01

    We measured the strength of the hollow-face illusion--the 'flipping distance' at which perception changes between convex and concave--as a function of a lens-induced 3 dioptre refractive error and monocular/binocular viewing. Refractive error and closing one eye both strengthened the illusion to approximately the same extent. The illusion was weakest viewed binocularly without refractive error and strongest viewed monocularly with it. This suggests binocular cues disambiguate the illusion at greater distances than monocular cues, but that both are disrupted by refractive error. We argue that refractive error leaves the ambiguous low-spatial-frequency shading information critical to the illusion largely unaffected while disrupting other, potentially disambiguating, depth/distance cues.

  15. Screening for uncorrected refractive error in secondary school-age students in Fiji.

    Science.gov (United States)

    Lindquist, Anthea C; Cama, Ana; Keeffe, Jill E

    2011-01-01

    To estimate the rate of uncorrected refractive error and the associations with gender, age, ethnicity and place of residence. Population-based study. Secondary school students in the Central Division of Fiji. All 58 secondary schools in the Central Division of Fiji were invited to participate and one class per year level at each participating school was randomly selected for screening. Visual acuity was tested using a logMAR chart and pinhole. Outcomes of screening included normal vision, corrected refractive error, uncorrected refractive error (VA Prevalence of uncorrected refractive error. The participation rate of schools was 91% with 8201 students aged 12-20 years; 8021 students had normal vision; 180 had impaired vision (166 refractive error and 14 low vision). The rate of refractive error was 2.0% (95% CI: 1.7-2.3). Indian students were nearly 6 times more likely (OR: 5.89; 95% CI: 4.17-8.34; P refractive error than Fijians. The rate of uncorrected refractive error was 0.9% (95% CI: 0.7-1.1) in Fijian students (OR: 2.89; 95% CI: 1.37-6.10; P = 0.01) and those living in rural areas (OR: 3.28; 95% CI: 1.32-8.16; P = 0.01) were more likely to have uncorrected refractive error. The rate decreased by 20% (95% CI: 4.0-33.0) with each year of increasing age. The prevalence of uncorrected refractive error in children is relatively low in Fiji with higher rates in Fijian and rural children. © 2011 The Authors. Clinical and Experimental Ophthalmology © 2011 Royal Australian and New Zealand College of Ophthalmologists.

  16. Development and distribution of refractive error in children with Down's syndrome.

    Science.gov (United States)

    Al-Bagdady, Mohammad; Murphy, Paul J; Woodhouse, J Margaret

    2011-08-01

    Previous studies have described the emmetropisation process as inactive in Down's syndrome (DS). However, these studies investigated only a small age range of children-either young children or teenagers. The present study aims to describe refractive error development and distribution in DS throughout childhood and early teenage years. Subjects were recruited from the Cardiff University Down's Syndrome Vision Research cohort. Refractive error was measured using Mohindra retinoscopy. Subjects were grouped into 15 yearly age groups to allow a cross-sectional assessment of refractive error distribution (n=182). Longitudinal refractive development was observed in 12 children with DS whose refractive error had been monitored throughout their childhood and teenage years. Children were hypermetropic, on average, at all ages, albeit with a wide variation in refractive errors. Change in power vector components, M, J(0) and J(45), and the presence of significant astigmatism (≥1.00 D) was assessed with age. There were no statistically significant difference in M and J(0) across age groups. However, there was a significant difference in J(45). Prevalence of significant oblique astigmatism increased with age and was highly prevalent (45%) in teenage years. Longitudinally, no significant change in refractive error was reported with regards to the spherical component. The results provide further evidence of the failure in the emmetropisation process in children with DS. Change in spherical refractive error is minimal throughout childhood and early adulthood. The children show a specific development of oblique astigmatism that may be suggestive of a mechanical induction through eyelids.

  17. Refractive errors among children, adolescents and adults attending eye clinics in Mexico

    Directory of Open Access Journals (Sweden)

    Francisco Gomez-Salazar

    2017-05-01

    Full Text Available AIM: To assess the proportion of refractive errors in the Mexican population that visited primary care optometry clinics in fourteen states of Mexico. METHODS: Refractive data from 676 856 patients aged 6 to 90y were collected from optometry clinics in fourteen states of Mexico between 2014 and 2015. The refractive errors were classified by the spherical equivalent (SE, as follows: sphere+½ cylinder. Myopia (SE>-0.50 D, hyperopia (SE>+0.50 D, emmetropia (-0.50≤SE≤+0.50, and astigmatism alone (cylinder≥-0.25 D. A negative cylinder was selected as a notation. RESULTS: The proportion (95% confidence interval among all of the subjects was hyperopia 21.0% (20.9-21.0, emmetropia 40.7% (40.5-40.8, myopia 24.8% (24.7-24.9 and astigmatism alone 13.5% (13.4-13.5. Myopia was the most common refractive error and frequency seemed to increase among the young population (10 to 29 years old, however, hyperopia increased among the aging population (40 to 79 years old, and astigmatism alone showed a decreasing trend with age (6 to 90y; from 19.7% to 10.8%. There was a relationship between age and all refractive errors (approximately 60%, aged 50 and older. The proportion of any clinically important refractive error was higher in males (61.2% than in females (58.3%; P<0.0001. From fourteen states that collected information, the proportion of refractive error showed variability in different geographical areas of Mexico. CONCLUSION: Myopia is the most common refractive error in the population studied. This study provides the first data on refractive error in Mexico. Further programs and studies must be developed to address the refractive errors needs of the Mexican population.

  18. Prevalence and pattern of refractive errors among primary school children in Al Hassa , Saudi Arabia.

    Science.gov (United States)

    Al Wadaani, Fahd Abdullah; Amin, Tarek Tawfik; Ali, Ayub; Khan, Atuar Rahman

    2012-11-11

    Some 12.8 million in the age group 5-15 years are visually impaired from uncorrected or inadequately corrected refractive errors. In Saudi Arabia, the size of this public health problem is not well defined especially among primary schoolchildren. The purpose of this cross-sectional study was to assess the prevalence and pattern of refractive errors among primary school children in Al Hassa, Saudi Arabia.  A total of 2246 Saudi primary school children aged 6 to 14 years of both genders were selected using multistage sampling method form 30 primary schools located in the three different areas of Al Hassa. School children were interviewed to collect demographics and vision data using a special data collection form followed by screening for refractive errors by trained optometrists within the school premises using a standardized protocol. Assessment of visual acuity and ocular motility evaluation were carried out and cover-uncover test was performed. Children detected with defective vision were referred for further examination employing subjective refraction with auto refractometer and objective refraction using streak retinoscopy after 1% cyclopentolate. Of the screened school children (N=2002), the overall prevalence of refractive errors was 13.7% (n=274), higher among females (Odds ratio, OR=1.39, P=0.012) and significantly more among students of rural residence (OR=2.40, P=0.001). The prevalence of refractive errors was disproportionately more among those aged 12-14 years (OR=9.02, P=0.001). Only 9.4% of students with poor vision were wore spectacles for correction. Myopia was the most commonly encountered refractive error among both genders (65.7% of the total errors encountered). Uncorrected refractive errors affected a sizable portion of primary school children in Al Hassa, Saudi Arabia. Primary schoolchildren especially females, rural and older children represents high risk group for refractive errors for which the included children were unaware.

  19. Refractive, corneal and ocular residual astigmatism: distribution in a German population and age-dependency - the Gutenberg health study.

    Science.gov (United States)

    Schuster, Alexander Karl-Georg; Pfeiffer, Norbert; Schulz, Andreas; Hoehn, René; Ponto, Katharina A; Wild, Philipp S; Blettner, Maria; Beutel, Manfred E; Lackner, Karl J; Münzel, Thomas; Mirshahi, Alireza

    2017-12-01

    Worldwide, the most frequent cause of visual impairment is uncorrected refractive error. This analysis focused on the distribution and associations of refractive, corneal and ocular residual astigmatism. As part of the Gutenberg Health study, a population-based cross-sectional study was conducted in the general population of Germany. A comprehensive ophthalmological examination including refraction, tonometry, and Scheimpflug imaging of the anterior cornea (Pachycam) was performed. In addition to the magnitude and type (with-the-rule, against-the-rule, oblique) of the refractive or corneal astigmatism, we calculated the vector components (J 0 , J 45 ) of both astigmatisms and calculated the ocular residual astigmatism. We performed multiple quantile regression analysis to evaluate the factors associated with refractive, corneal and ocular residual astigmatisms. A total of 13,558 subjects (49% female) with a mean age of 54.0 years (range 35-74 years) were included in this study. The prevalence of refractive astigmatism (>1.0D) was 13.0% in right eyes and 12.0% in left eyes, and 85% of these subjects wore spectacles. The distribution of refractive astigmatism showed a two-peak distribution with high astigmatism for with-the-rule and against-the-rule astigmatism. The associated factors were corneal curvature, age and sex for the different astigmatisms (p prevalence of different astigmatisms within a European population. We confirmed a shift with aging from with-the-rule to against-the-rule astigmatism to refractive and corneal astigmatism. Astigmatism has a large impact on visual perception; more than 85% of people with astigmatism over one diopter wore glasses for distance vision.

  20. Effect of watching 3-dimensional television on refractive error in children.

    Science.gov (United States)

    Kim, Seung-Hyun; Suh, Young-Woo; Choi, Yong-Min; Han, Ji-Yoon; Nam, Gi-Tae; You, Eun-Joo; Cho, Yoonae A

    2015-02-01

    To investigate the effect of watching 3-dimensional (3D) television (TV) on refractive error in children. Sixty healthy volunteers, aged 6 to 12 years, without any ocular abnormalities other than refractive error were recruited for this study. They watched 3D TV for 50 minutes at a viewing distance of 2.8 meters. The image disparity of the 3D contents was from -1 to 1 degree. Refractive errors were measured both before and immediately after watching TV and were rechecked after a 10-minute rest period. The refractive errors before and after watching TV were compared. The amount of refractive change was also compared between myopes and controls. The refractive error of the participants who showed a myopic shift immediately after watching TV were compared across each time point to assure that the myopic shift persisted after a 10-minute rest. The mean age of the participants was 9.23 ± 1.75 years. The baseline manifest refractive error was -1.70 ± 1.79 (-5.50 to +1.25) diopters. The refractive errors immediately after watching and after a 10-minute rest were -1.75 ± 1.85 and -1.69 ± 1.80 diopters, respectively, which were not different from the baseline values. Myopic participants (34 participants), whose spherical equivalent was worse than -0.75 diopters, also did not show any significant refractive change after watching 3D TV. A myopic shift was observed in 31 participants with a mean score of 0.29 ± 0.23 diopters, which resolved after a 10-minute rest. Watching properly made 3D content on a 3D TV for 50 minutes with a 10-minute intermission at more than 2.8 meters of viewing distance did not affect the refractive error of children.

  1. Prevalence of refractive error in Europe: the European Eye Epidemiology (E(3)) Consortium.

    Science.gov (United States)

    Williams, Katie M; Verhoeven, Virginie J M; Cumberland, Phillippa; Bertelsen, Geir; Wolfram, Christian; Buitendijk, Gabriëlle H S; Hofman, Albert; van Duijn, Cornelia M; Vingerling, Johannes R; Kuijpers, Robert W A M; Höhn, René; Mirshahi, Alireza; Khawaja, Anthony P; Luben, Robert N; Erke, Maja Gran; von Hanno, Therese; Mahroo, Omar; Hogg, Ruth; Gieger, Christian; Cougnard-Grégoire, Audrey; Anastasopoulos, Eleftherios; Bron, Alain; Dartigues, Jean-François; Korobelnik, Jean-François; Creuzot-Garcher, Catherine; Topouzis, Fotis; Delcourt, Cécile; Rahi, Jugnoo; Meitinger, Thomas; Fletcher, Astrid; Foster, Paul J; Pfeiffer, Norbert; Klaver, Caroline C W; Hammond, Christopher J

    2015-04-01

    To estimate the prevalence of refractive error in adults across Europe. Refractive data (mean spherical equivalent) collected between 1990 and 2013 from fifteen population-based cohort and cross-sectional studies of the European Eye Epidemiology (E(3)) Consortium were combined in a random effects meta-analysis stratified by 5-year age intervals and gender. Participants were excluded if they were identified as having had cataract surgery, retinal detachment, refractive surgery or other factors that might influence refraction. Estimates of refractive error prevalence were obtained including the following classifications: myopia ≤-0.75 diopters (D), high myopia ≤-6D, hyperopia ≥1D and astigmatism ≥1D. Meta-analysis of refractive error was performed for 61,946 individuals from fifteen studies with median age ranging from 44 to 81 and minimal ethnic variation (98 % European ancestry). The age-standardised prevalences (using the 2010 European Standard Population, limited to those ≥25 and prevalence of myopia in younger participants [47.2 % (CI 41.8-52.5) in 25-29 years-olds]. Refractive error affects just over a half of European adults. The greatest burden of refractive error is due to myopia, with high prevalence rates in young adults. Using the 2010 European population estimates, we estimate there are 227.2 million people with myopia across Europe.

  2. Prevalence of Refractive Errors in the INK Area, Durban, South Africa.

    Science.gov (United States)

    Mashige, Khathutshelo Percy; Jaggernath, Jyotikumarie; Ramson, Prasidh; Martin, Carrin; Chinanayi, Farai S; Naidoo, Kovin S

    2016-03-01

    To determine the prevalence and types of refractive errors in persons aged 35 years and older in the Inanda, Ntuzuma, and KwaMashu (INK) area of Durban, KwaZulu-Natal Province, South Africa. Refractive error data were obtained by autorefraction (Retinomax K-Plus; Nikon, Tokyo, Japan), retinoscopy, and subjective refraction. Refractive error was defined using spherical equivalents as myopia (+0.5D). Astigmatism was defined as cylinder equal to or greater than -0.5D in either eye. Participants' ages ranged from 35 to 90 years, with a mean of 53.05 ± 11.4 years. Women comprised 75% of the subjects. The prevalence of refractive error was 57.3%, with myopia 11.4%, hyperopia 37.7%, and astigmatism 25.7%. Myopia and astigmatism were significantly more prevalent in men (p prevalent in women (p refractive errors, with myopia, hyperopia, and astigmatism being significantly associated with sex. This study suggests that there is a need for interventions to alleviate refractive error in the INK area as well as in other communities affected by the lack of access to affordable services.

  3. Magnitude and determinants of refractive error among school children of two districts of Kathmandu, Nepal.

    Science.gov (United States)

    Adhikari, Srijana; Nepal, Bhagwat P; Shrestha, Jeevan Kumar; Khandekar, Rajiv

    2013-09-01

    The purpose of this study is to assess the magnitude and determinants of refractive error among school children of Lalitpur and Bhaktapur districts in Kathmandu Valley of Nepal. A descriptive study was carried out in 2003 in four schools; two in each district. A detailed ocular examination was conducted of all children attending these schools and that included visual acuity testing, slit lamp examination, fundus evaluation, retinoscopy, cycloplegic refraction and subjective refraction. Myopia was defined as more than -0.5 D and hypermetropia was defined as error of more than +1 D. A total of 2000 students of 5-16 years of age were examined. The prevalence of refractive error was 8.60% (95% confidence interval [CI] 7.37-9.83). The prevalence of myopia was 6.85% (95% CI 5.74-7.96). The best-corrected visual acuity was 6/9 or less in the eye of 12.8% children with refractive error. Refractive error is of public health magnitude among school children of 14-16 years of age. School screening program in countries like Nepal for early detection of treatable disease is useful to detect and correct refractive error in older students.

  4. Refractive errors among children, adolescents and adults attending eye clinics in Mexico

    Science.gov (United States)

    Gomez-Salazar, Francisco; Campos-Romero, Abraham; Gomez-Campaña, Humberto; Cruz-Zamudio, Cinthia; Chaidez-Felix, Mariano; Leon-Sicairos, Nidia; Velazquez-Roman, Jorge; Flores-Villaseñor, Hector; Muro-Amador, Secundino; Guadron-Llanos, Alma Marlene; Martinez-Garcia, Javier J.; Murillo-Llanes, Joel; Sanchez-Cuen, Jaime; Llausas-Vargas, Alejando; Alapizco-Castro, Gerardo; Irineo-Cabrales, Ana; Graue-Hernandez, Enrique; Ramirez-Luquin, Tito; Canizalez-Roman, Adrian

    2017-01-01

    AIM To assess the proportion of refractive errors in the Mexican population that visited primary care optometry clinics in fourteen states of Mexico. METHODS Refractive data from 676 856 patients aged 6 to 90y were collected from optometry clinics in fourteen states of Mexico between 2014 and 2015. The refractive errors were classified by the spherical equivalent (SE), as follows: sphere+½ cylinder. Myopia (SE>-0.50 D), hyperopia (SE>+0.50 D), emmetropia (-0.50≤SE≤+0.50), and astigmatism alone (cylinder≥-0.25 D). A negative cylinder was selected as a notation. RESULTS The proportion (95% confidence interval) among all of the subjects was hyperopia 21.0% (20.9-21.0), emmetropia 40.7% (40.5-40.8), myopia 24.8% (24.7-24.9) and astigmatism alone 13.5% (13.4-13.5). Myopia was the most common refractive error and frequency seemed to increase among the young population (10 to 29 years old), however, hyperopia increased among the aging population (40 to 79 years old), and astigmatism alone showed a decreasing trend with age (6 to 90y; from 19.7% to 10.8%). There was a relationship between age and all refractive errors (approximately 60%, aged 50 and older). The proportion of any clinically important refractive error was higher in males (61.2%) than in females (58.3%; PMexico. CONCLUSION Myopia is the most common refractive error in the population studied. This study provides the first data on refractive error in Mexico. Further programs and studies must be developed to address the refractive errors needs of the Mexican population. PMID:28546940

  5. Prevalence of refractive error, presbyopia, and unmet need of spectacle coverage in a northern district of Bangladesh: Rapid Assessment of Refractive Error study.

    Science.gov (United States)

    Muhit, Mohammad; Minto, Hasan; Parvin, Afroza; Jadoon, Mohammad Z; Islam, Johurul; Yasmin, Sumrana; Khandaker, Gulam

    2018-04-01

    To determine the prevalence of refractive error (RE), presbyopia, spectacle coverage, and barriers to uptake optical services in Bangladesh. Rapid assessment of refractive error (RARE) study following the RARE protocol was conducted in a northern district (i.e., Sirajganj) of Bangladesh (January 2010-December 2012). People aged 15-49 years were selected, and eligible participants had habitual distance and near visual acuity (VA) measured and ocular examinations were performed in those with VArefraction services is required to correct REs and presbyopia in Bangladesh.

  6. Prevalence of refractive error in Europe: the European Eye Epidemiology (E3) Consortium

    NARCIS (Netherlands)

    K.M. Williams (Katie M.); V.J.M. Verhoeven (Virginie); P. Cumberland (Phillippa); G. Bertelsen (Geir); C. Wolfram (Christian); G.H.S. Buitendijk (Gabrielle); A. Hofman (Albert); C.M. van Duijn (Cornelia); J.R. Vingerling (Hans); R.W.A.M. Kuijpers (Robert); R. Höhn (René); A. Mirshahi (Alireza); A.P. Khawaja (Anthony P.); R.N. Luben (Robert N.); M.G. Erke (Maja Gran); T. Von Hanno (Therese); O. Mahroo (Omar); R. Hogg (Ruth); C. Gieger (Christian); A. Cougnard-Grégoire (Audrey); E. Anastasopoulos (Eleftherios); A. Bron (Alain); J.-F. Dartigues; J.-F. Korobelnik (Jean-François); C. Creuzot-Garcher (Catherine); F. Topouzis (Fotis); C. Delcourt (Cécile); J.S. Rahi (Jugnoo); T. Meitinger (Thomas); A. Fletcher (Astrid); P.J. Foster (Paul J.); N. Pfeiffer (Norbert); C.C.W. Klaver (Caroline); C.J. Hammond (Christopher)

    2015-01-01

    textabstractTo estimate the prevalence of refractive error in adults across Europe. Refractive data (mean spherical equivalent) collected between 1990 and 2013 from fifteen population-based cohort and cross-sectional studies of the European Eye Epidemiology (E3) Consortium were combined in a random

  7. Refractive errors in patients attending a private hospital in Jos, Nigeria

    African Journals Online (AJOL)

    2013-05-02

    May 2, 2013 ... Conclusion: The study shows that refractive error is a common cause of VI and myopia is the most common type. It confirms that most of the .... obtained from the management of the Hospital. The study ..... Basic and Clinical Science Course 1992‑1993 Section 3: Optics, Refraction, and Contact Lenses.

  8. Refractive error assessment: influence of different optical elements and current limits of biometric techniques.

    Science.gov (United States)

    Ribeiro, Filomena; Castanheira-Dinis, Antonio; Dias, Joao Mendanha

    2013-03-01

    To identify and quantify sources of error on refractive assessment using exact ray tracing. The Liou-Brennan eye model was used as a starting point and its parameters were varied individually within a physiological range. The contribution of each parameter to refractive error was assessed using linear regression curve fits and Gaussian error propagation analysis. A MonteCarlo analysis quantified the limits of refractive assessment given by current biometric measurements. Vitreous and aqueous refractive indices are the elements that influence refractive error the most, with a 1% change of each parameter contributing to a refractive error variation of +1.60 and -1.30 diopters (D), respectively. In the phakic eye, axial length measurements taken by ultrasound (vitreous chamber depth, lens thickness, and anterior chamber depth [ACD]) were the most sensitive to biometric errors, with a contribution to the refractive error of 62.7%, 14.2%, and 10.7%, respectively. In the pseudophakic eye, vitreous chamber depth showed the highest contribution at 53.7%, followed by postoperative ACD at 35.7%. When optic measurements were considered, postoperative ACD was the most important contributor, followed by anterior corneal surface and its asphericity. A MonteCarlo simulation showed that current limits of refractive assessment are 0.26 and 0.28 D for the phakic and pseudophakic eye, respectively. The most relevant optical elements either do not have available measurement instruments or the existing instruments still need to improve their accuracy. Ray tracing can be used as an optical assessment technique, and may be the correct path for future personalized refractive assessment. Copyright 2013, SLACK Incorporated.

  9. Prevalence of refraction errors and color blindness in heavy vehicle drivers.

    Science.gov (United States)

    Erdoğan, Haydar; Ozdemir, Levent; Arslan, Seher; Cetin, Ilhan; Ozeç, Ayşe Vural; Cetinkaya, Selma; Sümer, Haldun

    2011-01-01

    To investigate the frequency of eye disorders in heavy vehicle drivers. A cross-sectional type study was conducted between November 2004 and September 2006 in 200 driver and 200 non-driver persons. A complete ophthalmologic examination was performed, including visual acuity, and dilated examination of the posterior segment. We used the auto refractometer for determining refractive errors. According to eye examination results, the prevalence of the refractive error was 21.5% and 31.3% in study and control groups respectively (P<0.05). The most common type of refraction error in the study group was myopic astigmatism (8.3%) while in the control group simple myopia (12.8%). Prevalence of dyschromatopsia in the rivers, control group and total group was 2.2%, 2.8% and 2.6% respectively. A considerably high number of drivers are in lack of optimal visual acuity. Refraction errors in drivers may impair the traffic security.

  10. Prevalence of refractive errors among primary school children in a tropical area, Southeastern Iran

    Directory of Open Access Journals (Sweden)

    Monireh Mahjoob

    2016-02-01

    Conclusions: Refractive errors affect a sizable portion of students in Zahedan. Although myopia is not very prevalent, the high rate of hyperopia in the studied population emphasizes its need for attention.

  11. Screening for refractive error among primary school children in Bayelsa state, Nigeria

    OpenAIRE

    Opubiri, Ibeinmo; Pedro-Egbe, Chinyere

    2013-01-01

    Introduction Vision screening study in primary school children has not been done in Bayelsa State. This study aims to screen for refractive error among primary school children in Bayelsa State and use the data to plan for school Eye Health Program. Methods A cross sectional study on screening for refractive error in school children was carried out in Yenagoa Local Government Area of Bayelsa State in June 2009. A multistage sampling technique was used to select the study population (pupils age...

  12. The Determinants of Early Refractive Error on School-Going Chinese Children

    OpenAIRE

    K. Jayaraman; Mohammad Iranmanesh; Chuan Chin Liang; Mahboobeh Iranmanesh

    2016-01-01

    Refractive error is a common social issue in every walks of human life, and its prevalence recorded the highest among Chinese population, particularly among people living in southern China, Hong Kong, Thailand, Singapore, and Malaysia. Refractive error is the simplest disorder to treat and supposed to cost the effective health care intervention. The present study included 168 Chinese school-going children aged 10 to 12...

  13. Falls and Postural Control in Older Adults With Eye Refractive Errors

    Directory of Open Access Journals (Sweden)

    Afsun Nodehi-Moghadam

    2016-04-01

    Conclusion: Vision impairment of older adults due to refractive error is not associated with an increase in falls. Furthermore, TUG test results did not show balance disorders in these groups. Further research, such as assessment of postural control with advanced devices and considering other falling risk factors is also needed to identify the predictors of falls in older adults with eye refractive errors.

  14. Prevalence and predictors of refractive error in a genetically isolated population: the Norfolk Island Eye Study.

    Science.gov (United States)

    Sherwin, Justin C; Kelly, John; Hewitt, Alex W; Kearns, Lisa S; Griffiths, Lyn R; Mackey, David A

    2011-11-01

    We aimed to determine the prevalence and associations of refractive error on Norfolk Island. Population-based study on Norfolk Island, South Pacific. All permanent residents on Norfolk Island aged ≥ 15 years were invited to participate. Patients underwent non-cycloplegic autorefraction, slit-lamp biomicroscope examination and biometry assessment. Only phakic eyes were analysed. Prevalence and multivariate associations of refractive error and myopia. There were 677 people (645 right phakic eyes, 648 left phakic eyes) aged ≥ 15 years were included in this study. Mean age of participants was 51.1 (standard deviation 15.7; range 15-81). Three hundred and seventy-six people (55.5%) were female. Adjusted to the 2006 Norfolk Island population, prevalence estimates of refractive error were as follows: myopia (mean spherical equivalent ≥ -1.0 D) 10.1%, hypermetropia (mean spherical equivalent ≥ 1.0 D) 36.6%, and astigmatism 17.7%. Significant independent predictors of myopia in the multivariate model were lower age (P refractive error were increasing age (P prevalence of myopia on Norfolk Island is lower than on mainland Australia, and the Norfolk Island population demonstrates ethnic differences in the prevalence estimates. Given the significant associations between refractive error and several ocular biometry characteristics, Norfolk Island may be a useful population in which to find the genetic basis of refractive error. © 2011 The Authors. Clinical and Experimental Ophthalmology © 2011 Royal Australian and New Zealand College of Ophthalmologists.

  15. Prevalence of refractive errors in school-age children in Morocco.

    Science.gov (United States)

    Anera, Rosario G; Soler, Margarita; de la Cruz Cardona, Juan; Salas, Carlos; Ortiz, Carolina

    2009-03-01

    The prevalence of refractive errors in school-age children in Morocco was assessed. A total of 545 children (300 boys and 245 girls, between 6 and 16 years of age) attending school were examined to assess their refractive errors in a field study in Morocco (North Africa). The examination included autorefraction under cycloplegia and visual acuity, stereopsis and anterior corneal-radius measurements . We found a low prevalence of myopia (prevalence of hyperopia (> or =2.0 D SE in at least one eye) was 18.3%. Astigmatism (children. The low prevalence of large refractive errors makes visual acuity in these children very good. In general, the corneal radii did not significantly vary with age. There were no significant differences between the distribution of refractive errors in these children according to gender but there were with respect to age. There was a low prevalence of myopia in these African children, astigmatism being the most frequent refractive error. The mean refractive errors found were low, and therefore visual acuity was high in these children.

  16. The patterns of refractive errors among the school children of rural and urban settings in Nepal.

    Science.gov (United States)

    Pokharel, A; Pokharel, P K; Das, H; Adhikari, S

    2010-01-01

    The uncorrected refractive error is an important cause of childhood blindness and visual impairment. To study the patterns of refractive errors among the urban and rural school going children of Nepal. A total of 440 school children of urban and rural schools within the age range of 7-15 years were selected for this study using multi-stage randomization technique. The overall prevalance of refractive error in school children was 19.8 %. The commonest refractive error among the students was myopia (59.8 %), followed by hypermetropia (31.0 %). The children of age group 12-15 years had the higher prevalence of myopia as compared to the younger counterparts (42.5 % vs 17.2 %). The prevalence of myopia was 15.5 % among the urban students as compared to 8.2 % among the rural ones (RR = 1.89, 95 % CI = 1.1-3.24). The hypermetropia was more common in urban students than in rural ones (6.4 %) vs 5.9 %, RR = 1.08 (95 % CI: 0.52-2.24). The prevalence of refractive error in the school children of Nepal is 19.8 %. The students from urban settings are more likely to have refractive error than their rural counterparts. © Nepal Ophthalmic Society.

  17. Prevalence of refractive error among school children in North-West Rajasthan

    OpenAIRE

    Khan, Nabab Ali; Jangir, Mahendra Kumar; Kochar, Anju; Bhargava, Poonam

    2016-01-01

    Purpose : To study the prevalence and relative frequency of refractive error among school children in North west Rajasthan so that an effective approach can be planned to tackle the burden of readily correctable refraction problems.Methods: A cross-sectional descriptive study was carried out to study the magnitude of refractive errors among school children in North-west Rajasthan.Results : A total of 1078 children were examined.  The subjects consist of 702 females (65.1%) and 376 males (34.9...

  18. Prevalence of refractive errors in the European adult population: the Gutenberg Health Study (GHS).

    Science.gov (United States)

    Wolfram, Christian; Höhn, René; Kottler, Ulrike; Wild, Philipp; Blettner, Maria; Bühren, Jens; Pfeiffer, Norbert; Mirshahi, Alireza

    2014-07-01

    To study the distribution of refractive errors among adults of European descent. Population-based eye study in Germany with 15010 participants aged 35-74 years. The study participants underwent a detailed ophthalmic examination according to a standardised protocol. Refractive error was determined by an automatic refraction device (Humphrey HARK 599) without cycloplegia. Definitions for the analysis were myopia +0.5 D, astigmatism >0.5 cylinder D and anisometropia >1.0 D difference in the spherical equivalent between the eyes. Exclusion criterion was previous cataract or refractive surgery. 13959 subjects were eligible. Refractive errors ranged from -21.5 to +13.88 D. Myopia was present in 35.1% of this study sample, hyperopia in 31.8%, astigmatism in 32.3% and anisometropia in 13.5%. The prevalence of myopia decreased, while the prevalence of hyperopia, astigmatism and anisometropia increased with age. 3.5% of the study sample had no refractive correction for their ametropia. Refractive errors affect the majority of the population. The Gutenberg Health Study sample contains more myopes than other study cohorts in adult populations. Our findings do not support the hypothesis of a generally lower prevalence of myopia among adults in Europe as compared with East Asia.

  19. Refractive error study in young subjects: results from a rural area in Paraguay.

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    Signes-Soler, Isabel; Hernández-Verdejo, José Luis; Estrella Lumeras, Miguel Angel; Tomás Verduras, Elena; Piñero, David P

    2017-01-01

    To evaluate the distribution of refractive error in young subjects in a rural area of Paraguay in the context of an international cooperation campaign for the prevention of blindness. A sample of 1466 young subjects (ranging from 3 to 22 years old), with a mean age of 11.21±3.63 years old, were examined to assess their distance visual acuity (VA) and refractive error. The first screening examination performed by trained volunteers, included visual acuity testing, autokeratometry and non-cycloplegic autorefraction. Inclusion criteria for a second complete cycloplegic eye examination by an optometrist were VA prevalence of hyperopia of 5.2% (0.2% of the total) in this specific group. Furthermore, myopia (spherical equivalent ≤-0.5 D) was found in 37.7% of the refracted children (0.5% of the total). The prevalence of refractive astigmatism (cylinder ≤-1.50 D) was 15.8% (0.6% of the total). Visual impairment (VI) (0.05≤VA≤0.3) was found in 12/114 (0.4%) of the refracted eyes. Main causes for VI were refractive error (58%), retinal problems (17%, 2/12), albinism (17%, 2/12) and unknown (8%, 1/12). A low prevalence of refractive error has been found in this rural area of Paraguay, with higher prevalence of myopia than of hyperopia.

  20. Prevalence of refractive errors among school children in gondar town, northwest ethiopia.

    Science.gov (United States)

    Yared, Assefa Wolde; Belaynew, Wasie Taye; Destaye, Shiferaw; Ayanaw, Tsegaw; Zelalem, Eshete

    2012-10-01

    Many children with poor vision due to refractive error remain undiagnosed and perform poorly in school. The situation is worse in the Sub-Saharan Africa, including Ethiopia, and current information is lacking. The objective of this study is to determine the prevalence of refractive error among children enrolled in elementary schools in Gondar town, Ethiopia. This was a cross-sectional study of 1852 students in 8 elementary schools. Subjects were selected by multistage random sampling. The study parameters were visual acuity (VA) evaluation and ocular examination. VA was measured by staff optometrists with the Snellen E-chart while students with subnormal vision were examined using pinhole, retinoscopy evaluation and subjective refraction by ophthalmologists. The study cohort was comprised of 45.8% males and 54.2% females from 8 randomly selected elementary schools with a response rate of 93%. Refractive errors in either eye were present in 174 (9.4%) children. Of these, myopia was diagnosed in 55 (31.6%) children in the right and left eyes followed by hyperopia in 46 (26.4%) and 39 (22.4%) in the right and left eyes respectively. Low myopia was the most common refractive error in 61 (49.2%) and 68 (50%) children for the right and left eyes respectively. Refractive error among children is a common problem in Gondar town and needs to be assessed at every health evaluation of school children for timely treatment.

  1. Higher order ocular aberrations and their relation to refractive error and ocular biometry in children.

    Science.gov (United States)

    Little, Julie-Anne; McCullough, Sara J; Breslin, Karen M M; Saunders, Kathryn J

    2014-07-15

    The interaction between higher order ocular aberrations (HOA) and refractive error is not yet fully understood. This study investigated HOA in relation to refractive error and ocular biometric parameters in a population with a high prevalence of ametropia. The HOA were investigated in two cohorts of Caucasian children aged 9 to 10 and 15 to 16 years (n = 313). These aberrations were measured for a 5-mm pupil with the IRX3 aberrometer. Cycloplegic refractive error and ocular biometry measures, including axial length and corneal curvature, also were assessed with the Shin-Nippon SRW-5000 auto-refractor and Zeiss IOLMaster, respectively. Participants were divided into refractive groups for analysis of HOA. The magnitude of total HOA was higher in this population at 0.27 μm (interquartile range [IQR], 0.22-0.32 μm) than other HOA reported in the literature. The profile of HOA was not significantly different across the two age cohorts or across refractive groups, nor did spherical aberration differ significantly with age (Z₄⁰ = 0.07 μm for both cohorts). Multivariate linear regression analysis demonstrated spherical aberration was significantly related to axial length (but not refractive grouping), with longer eyes having less positive values of fourth order and root mean square (RMS) spherical aberration. This study found no significant difference in HOA across refractive groups. The current study also highlights the importance of knowledge of axial length when analyzing HOA. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

  2. Refractive error and patterns of spectacle use in 12-year-old Australian children.

    Science.gov (United States)

    Robaei, Dana; Kifley, Annette; Rose, Kathryn A; Mitchell, Paul

    2006-09-01

    To document the prevalence of visual impairment resulting from refractive error and to describe patterns of spectacle use in a representative sample of 12-year-old Australian school children. Population-based cross-sectional study. Two thousand three hundred fifty-three predominantly 12-year-old children examined from 2004 through 2005. Logarithm of the minimum angle of resolution (logMAR) visual acuity (VA) was measured unaided and with spectacles if worn. Subjective refraction, cycloplegic autorefraction (with cyclopentolate), and detailed dilated fundus examination were performed. Myopia was defined as spherical equivalent (SE) refraction refraction > or =2.0 D, and astigmatism as cylinder > or =1.0 D. Uncorrected visual impairment was defined using unaided VA, and presenting visual impairment was defined using spectacle-corrected VA, if worn. Visual impairment was defined as VA refraction, and undercorrection as presenting impairment in the better eye, improving by at least 2 lines with refraction. Uncorrected and presenting visual impairment in at least 1 eye because of refractive error was found in 10.4% and 3.7%, respectively. Spectacle use was reported by 448 children (19.0%); 204 (46.3%) had myopia, 48 (10.9%) had hyperopia, and 96 (21.8%) had astigmatism in at least 1 eye; 38.3% had no significant refractive error in either eye. Eight children were in need of spectacles and 37 children (8.3% of spectacle users) were undercorrected. Nonrefractive spectacle users were more likely to report eyestrain and headache or to have had learning difficulty at school (Pprevalence of undercorrected refractive error in a population of Australian children. Nonrefractive prescription of spectacles is common.

  3. Prevalence of amblyopia and refractive errors in an unscreened population of children.

    Science.gov (United States)

    Polling, Jan-Roelof; Loudon, Sjoukje E; Klaver, Caroline C W

    2012-11-01

    To describe the frequency of refractive errors and amblyopia in unscreened children aged 2 months to 12 years from a rural town in Poland. Five hundred ninety-one children were identified by medical records and examined in a standardized manner.Visual acuity was measured using LogMAR charts; refractive error was determined using retinoscopy or autorefraction after cycloplegia. Myopia was defined as spherical equivalent (SE) ≤ -0.50 D, emmetropia as SE between -0.5 D and+0.5 D, mild hyperopia as SE between +0.5 D and +2.0 D, and high hyperopia as SE Q+2.0 D. Amblyopia was classified as best-corrected visual acuity ≥0.3 (≤ 20/40) LogMAR, in combination with a 2 LogMAR line difference between the two eyes and the presence of an amblyogenic factor. Refractive errors ranged from 84.2% in children aged up to 2 years to 75.5% in those aged 10 to 12 years.Refractive error showed a myopic shift with age; myopia prevalence increased from 2.2% in those aged 6 to 7 years to 6.3% in those aged 10 to 12 years. Of the examined children, 77 (16.3%) had refractive errors, with visual loss; of these,60 (78%) did not use corrections. The prevalence of amblyopia was 3.1%, and refractive error attributed to the amblyopiain 9 of 13 (69%) children. Refractive errors are common in Caucasian children and often remain undiagnosed. The prevalence of amblyopia was three times higher in this unscreened population compared with screened populations. Greater awarenessof these common treatable visual conditions in children is warranted.

  4. Prevalence of uncorrected refractive error and other eye problems among urban and rural school children.

    Science.gov (United States)

    Padhye, Amruta S; Khandekar, Rajiv; Dharmadhikari, Sheetal; Dole, Kuldeep; Gogate, Parikshit; Deshpande, Madan

    2009-04-01

    Uncorrected refractive error is an avoidable cause of visual impairment. To compare the magnitude and determinants of uncorrected refractive error, such as age, sex, family history of refractive error and use of spectacles among school children 6-15 years old in urban and rural Maharashtra, India. This was a review of school-based vision screening conducted in 2004-2005. Optometrists assessed visual acuity, amblyopia and strabismus in rural children. Teachers assessed visual acuity and then optometrists confirmed their findings in urban schools. Ophthalmologists screened for ocular pathology. Data of uncorrected refractive error, amblyopia, strabismus and blinding eye diseases was analyzed to compare the prevalence and risk factors among children of rural and urban areas. We examined 5,021 children of 8 urban clusters and 7,401 children of 28 rural clusters. The cluster-weighted prevalence of uncorrected refractive error in urban and rural children was 5.46% (95% CI, 5.44-5.48) and 2.63% (95% CI, 2.62-2.64), respectively. The prevalence of myopia, hypermetropia and astigmatism in urban children was 3.16%, 1.06% and 0.16%, respectively. In rural children, the prevalence of myopia, hypermetropia and astigmatism was 1.45%, 0.39% and 0.21%, respectively. The prevalence of amblyopia was 0.8% in urban and 0.2% in rural children. Thirteen to 15 years old children attending urban schools were most likely to have uncorrected myopia. The prevalence of uncorrected refractive error, especially myopia, was higher in urban children. Causes of higher prevalence and barriers to refractive error correction services should be identified and addressed. Eye screening of school children is recommended. However, the approach used may be different for urban and rural school children.

  5. Screening for refractive error among primary school children in Bayelsa State, Nigeria.

    Science.gov (United States)

    Opubiri, Ibeinmo; Pedro-Egbe, Chinyere

    2013-01-01

    Vision screening study in primary school children has not been done in Bayelsa State. This study aims to screen for refractive error among primary school children in Bayelsa State and use the data to plan for school Eye Health Program. A cross sectional study on screening for refractive error in school children was carried out in Yenagoa Local Government Area of Bayelsa State in June 2009. A multistage sampling technique was used to select the study population (pupils aged between 5-15 years). Visual acuity (VA) for each eye, was assessed outside the classroom at a distance of 6 meters. Those with VA ≤6/9 were presented with a pinhole and the test repeated. Funduscopy was done inside a poorly lit classroom. An improvement of the VA with pinhole was considered refractive error. Data was analyzed with EPI INFO version 6. A total of 1,242 school children consisting of 658 females and 584 males were examined. About 97.7% of pupils had normal VA (VA of 6/6) while 56 eyes had VAs ≤ 6/9. Of these 56 eyes, the visual acuity in 49 eyes (87.5%) improved with pinhole. Twenty seven pupils had refractive error, giving a prevalence of 2.2%. Refractive error involved both eyes in 22 pupils (81.5%) and the 8-10 years age range had the highest proportion (40.7%) of cases of refractive error followed by the 9-13 year-old age range (37%). The prevalence of refractive error was 2.2% and most eyes (97.7%) had normal vision.

  6. Prevalence of the refractive errors by age and gender: the Mashhad eye study of Iran.

    Science.gov (United States)

    Ostadimoghaddam, Hadi; Fotouhi, Akbar; Hashemi, Hassan; Yekta, Abbasali; Heravian, Javad; Rezvan, Farhad; Ghadimi, Hamidreza; Rezvan, Bijan; Khabazkhoob, Mehdi

    2011-11-01

    Refractive errors are a common eye problem. Considering the low number of population-based studies in Iran in this regard, we decided to determine the prevalence rates of myopia and hyperopia in a population in Mashhad, Iran. Cross-sectional population-based study. Random cluster sampling. Of 4453 selected individuals from the urban population of Mashhad, 70.4% participated. Refractive error was determined using manifest (age > 15 years) and cycloplegic refraction (age ≤ 15 years). Myopia was defined as a spherical equivalent of -0.5 diopter or worse. An spherical equivalent of +0.5 diopter or worse for non-cycloplegic refraction and an spherical equivalent of +2 diopter or worse for cycloplegic refraction was used to define hyperopia. Prevalence of refractive errors. The prevalence of myopia and hyperopia in individuals ≤ 15 years old was 3.64% (95% CI: 2.19-5.09) and 27.4% (95% CI: 23.72-31.09), respectively. The same measurements for subjects > 15 years of age was 22.36% (95% CI: 20.06-24.66) and 34.21% (95% CI: 31.57-36.85), respectively. Myopia was found to increase with age in individuals ≤ 15 years and decrease with age in individuals > 15 years of age. The rate of hyperopia showed a significant increase with age in individuals > 15 years. The prevalence of astigmatism was 25.64% (95% CI: 23.76-27.51). In children and the elderly, hyperopia is the most prevalent refractive error. After hyperopia, astigmatism is also of importance in older ages. Age is the most important demographic factor associated with different types of refractive errors. © 2011 The Authors. Clinical and Experimental Ophthalmology © 2011 Royal Australian and New Zealand College of Ophthalmologists.

  7. Prevalence of refractive errors in the Slovak population calculated using the Gullstrand schematic eye model.

    Science.gov (United States)

    Popov, I; Valašková, J; Štefaničková, J; Krásnik, V

    2017-01-01

    A substantial part of the population suffers from some kind of refractive errors. It is envisaged that their prevalence may change with the development of society. The aim of this study is to determine the prevalence of refractive errors using calculations based on the Gullstrand schematic eye model. We used the Gullstrand schematic eye model to calculate refraction retrospectively. Refraction was presented as the need for glasses correction at a vertex distance of 12 mm. The necessary data was obtained using the optical biometer Lenstar LS900. Data which could not be obtained due to the limitations of the device was substituted by theoretical data from the Gullstrand schematic eye model. Only analyses from the right eyes were presented. The data was interpreted using descriptive statistics, Pearson correlation and t-test. The statistical tests were conducted at a level of significance of 5%. Our sample included 1663 patients (665 male, 998 female) within the age range of 19 to 96 years. Average age was 70.8 ± 9.53 years. Average refraction of the eye was 2.73 ± 2.13D (males 2.49 ± 2.34, females 2.90 ± 2.76). The mean absolute error from emmetropia was 3.01 ± 1.58 (males 2.83 ± 2.95, females 3.25 ± 3.35). 89.06% of the sample was hyperopic, 6.61% was myopic and 4.33% emmetropic. We did not find any correlation between refraction and age. Females were more hyperopic than males. We did not find any statistically significant hypermetopic shift of refraction with age. According to our estimation, the calculations of refractive errors using the Gullstrand schematic eye model showed a significant hypermetropic shift of more than +2D. Our results could be used in future for comparing the prevalence of refractive errors using same methods we used.Key words: refractive errors, refraction, Gullstrand schematic eye model, population, emmetropia.

  8. Measurement of refractive errors in young myopes using the COAS Shack-Hartmann aberrometer.

    Science.gov (United States)

    Salmon, Thomas O; West, Roger W; Gasser, Wayne; Kenmore, Todd

    2003-01-01

    To evaluate the Complete Ophthalmic Analysis System (COAS; WaveFront Science) for accuracy, repeatability, and instrument myopia when measuring myopic refractive errors. We measured the refractive errors of 20 myopic subjects (+0.25 to -10 D sphere; 0 to -1.75 D cylinder) with a COAS, a phoropter, and a Nidek ARK-2000 autorefractor. Measurements were made for right and left eyes, with and without cycloplegia, and data were analyzed for large and small pupils. We used the phoropter refraction as our estimate of the true refractive error, so accuracy was defined as the difference between phoropter refraction and that of the COAS and autorefractor. Differences and means were computed using power vectors, and accuracy was summarized in terms of mean vector and mean spherocylindrical power errors. To assess repeatability, we computed the mean vector deviation for each of five measurements from the mean power vector and computed a coefficient of repeatability. Instrument myopia was defined as the difference between cycloplegic and noncycloplegic refractions for the same eyes. Without cycloplegia, both the COAS and autorefractor had mean power vector errors of 0.3 to 0.4 D. Cycloplegia improved autorefractor accuracy by 0.1 D, but COAS accuracy remained the same. For large pupils, COAS accuracy was best when Zernike mode Z4(0) (primary spherical aberration) was included in the computation of sphere power. COAS repeatability was slightly better than autorefraction repeatability. Mean instrument myopia for the COAS was not significantly different from zero. When measuring myopes, COAS accuracy, repeatability, and instrument myopia were similar to those of the autorefractor. Error margins for both were better than the accuracy of subjective refraction. We conclude that in addition to its capability to measure higher-order aberrations, the COAS can be used as a reliable, accurate autorefractor.

  9. Prevalence of refractive error in the United States, 1999-2004.

    Science.gov (United States)

    Vitale, Susan; Ellwein, Leon; Cotch, Mary Frances; Ferris, Frederick L; Sperduto, Robert

    2008-08-01

    To describe the prevalence of refractive error in the United States. The 1999-2004 National Health and Nutrition Examination Survey (NHANES) used an autorefractor to obtain refractive error data on a nationally representative sample of the US noninstitutionalized, civilian population 12 years and older. Using data from the eye with a greater absolute spherical equivalent (SphEq) value, we defined clinically important refractive error as follows: hyperopia, SphEq value of 3.0 diopters (D) or greater; myopia, SphEq value of -1.0 D or less; and astigmatism, cylinder of 1.0 D or greater in either eye. Of 14,213 participants 20 years or older who completed the NHANES, refractive error data were obtained for 12,010 (84.5%). The age-standardized prevalences of hyperopia, myopia, and astigmatism were 3.6% (95% confidence interval [CI], 3.2%-4.0%), 33.1% (95% CI, 31.5%-34.7%), and 36.2% (95% CI, 34.9%-37.5%), respectively. Myopia was more prevalent in women (39.9%) than in men (32.6%) (P refractive error affects half of the US population 20 years or older.

  10. Survey on Visual Impairment and Refractive Errors on Ta′u Island, American Samoa

    Directory of Open Access Journals (Sweden)

    Shawn S Barnes

    2011-01-01

    Full Text Available Purpose: To assess the prevalence of presenting visual impairment and refractive errors on the isolated island of Ta′u, American Samoa. Methods: Presenting visual acuity and refractive errors of 124 adults over 40 years of age (55 male and 69 female were measured using the Snellen chart and an autorefractometer. This sample represented over 50% of the island′s eligible population. Results: In this survey, all presenting visual acuity (VA was uncorrected. Of the included sample, 10.5% presented with visual impairment (visual acuity lower than 6/18, but equal to or better than 3/60 in the better eye and 4.8% presented with VA worse than 6/60 in the better eye. Overall, 4.0% of subjects presented with hyperopia (+3 D or more, 3.2% were myopic (‑1 D or less, and 0.8% presented with high myopia (‑5 D or less. There was no significant difference between genders in terms of visual impairment or refractive errors. Conclusion: This study represents the first population-based survey on presenting visual acuity and refractive errors in American Samoa. In addition to providing baseline data on vision and refractive errors, we found that the prevalence of myopia and hyperopia was much lower than expected.

  11. Prevalence of refractive error in mentally retarded students of Kathmandu Valley.

    Science.gov (United States)

    Ghising, R; Shakya, S; Rizyal, A; Shrestha, R; Shrestha, S; Wang-Harris, S

    2007-12-01

    Mental retardation also known as 'mentally handicap' means a delay or insufficient development of mental capacities. The prevalence of mental retardation in Nepal is 4.1%. Vision being the best sense for their education and daily activities, a cross-sectional and descriptive study was conducted to find out the refractive error among the students in the schools for mentally retarded people. A total of 134 clinically diagnosed cases of mentally retarded students from three different schools of Kathmandu Valley were examined. Distance visual acuity was taken with the help of Cat Ford Vision Drum, SG chart and Kay Picture Test method but first preference was given to SG chart. Cyclo-retinoscopy and fundus examination under mydriasis were done in all the cases. Examination revealed that more than half of the examined had one or more ocular disorders with refractive error being the most common type of ocular morbidity followed by ocular motility disorders. Refractive errors were found in 34.4% in which the most common type of refractive error was simple hypermetropia. In conclusion refractive error was seen commonly among mentally retarded people of Kathmandu Valley.

  12. The Determinants of Early Refractive Error on School-Going Chinese Children

    Directory of Open Access Journals (Sweden)

    K. Jayaraman

    2016-04-01

    Full Text Available Refractive error is a common social issue in every walks of human life, and its prevalence recorded the highest among Chinese population, particularly among people living in southern China, Hong Kong, Thailand, Singapore, and Malaysia. Refractive error is the simplest disorder to treat and supposed to cost the effective health care intervention. The present study included 168 Chinese school-going children aged 10 to 12 years; they were selected from different schools of urban Malaysia. It was surprising to see that 112 (66.7% children had the early onset of refractive error; refractive error was also detected late among the primary school or secondary school students. The findings revealed that the determinants of refractive error among Chinese children were personal achievements and machine dependence. The possible reasons for the above significant factors emerged could be attributed to the inbuilt culture and traditions of Chinese parents who insist that their children should be hardworking and focus on school subjects so that their parents allow them to use luxury electronic devices.

  13. High Prevalence of Refractive Errors in 7 Year Old Children in Iran

    Science.gov (United States)

    HASHEMI, Hassan; YEKTA, Abbasali; JAFARZADEHPUR, Ebrahim; OSTADIMOGHADDAM, Hadi; ETEMAD, Koorosh; ASHARLOUS, Amir; NABOVATI, Payam; KHABAZKHOOB, Mehdi

    2016-01-01

    Background: The latest WHO report indicates that refractive errors are the leading cause of visual impairment throughout the world. The aim of this study was to determine the prevalence of myopia, hyperopia, and astigmatism in 7 yr old children in Iran. Methods: In a cross-sectional study in 2013 with multistage cluster sampling, first graders were randomly selected from 8 cities in Iran. All children were tested by an optometrist for uncorrected and corrected vision, and non-cycloplegic and cycloplegic refraction. Refractive errors in this study were determined based on spherical equivalent (SE) cyloplegic refraction. Results: From 4614 selected children, 89.0% participated in the study, and 4072 were eligible. The prevalence rates of myopia, hyperopia and astigmatism were 3.04% (95% CI: 2.30–3.78), 6.20% (95% CI: 5.27–7.14), and 17.43% (95% CI: 15.39–19.46), respectively. Prevalence of myopia (P=0.925) and astigmatism (P=0.056) were not statistically significantly different between the two genders, but the odds of hyperopia were 1.11 (95% CI: 1.01–2.05) times higher in girls (P=0.011). The prevalence of with-the-rule astigmatism was 12.59%, against-the-rule was 2.07%, and oblique 2.65%. Overall, 22.8% (95% CI: 19.7–24.9) of the schoolchildren in this study had at least one type of refractive error. Conclusion: One out of every 5 schoolchildren had some refractive error. Conducting multicenter studies throughout the Middle East can be very helpful in understanding the current distribution patterns and etiology of refractive errors compared to the previous decade. PMID:27114984

  14. High Prevalence of Refractive Errors in 7 Year Old Children in Iran.

    Science.gov (United States)

    Hashemi, Hassan; Yekta, Abbasali; Jafarzadehpur, Ebrahim; Ostadimoghaddam, Hadi; Etemad, Koorosh; Asharlous, Amir; Nabovati, Payam; Khabazkhoob, Mehdi

    2016-02-01

    The latest WHO report indicates that refractive errors are the leading cause of visual impairment throughout the world. The aim of this study was to determine the prevalence of myopia, hyperopia, and astigmatism in 7 yr old children in Iran. In a cross-sectional study in 2013 with multistage cluster sampling, first graders were randomly selected from 8 cities in Iran. All children were tested by an optometrist for uncorrected and corrected vision, and non-cycloplegic and cycloplegic refraction. Refractive errors in this study were determined based on spherical equivalent (SE) cyloplegic refraction. From 4614 selected children, 89.0% participated in the study, and 4072 were eligible. The prevalence rates of myopia, hyperopia and astigmatism were 3.04% (95% CI: 2.30-3.78), 6.20% (95% CI: 5.27-7.14), and 17.43% (95% CI: 15.39-19.46), respectively. Prevalence of myopia (P=0.925) and astigmatism (P=0.056) were not statistically significantly different between the two genders, but the odds of hyperopia were 1.11 (95% CI: 1.01-2.05) times higher in girls (P=0.011). The prevalence of with-the-rule astigmatism was 12.59%, against-the-rule was 2.07%, and oblique 2.65%. Overall, 22.8% (95% CI: 19.7-24.9) of the schoolchildren in this study had at least one type of refractive error. One out of every 5 schoolchildren had some refractive error. Conducting multicenter studies throughout the Middle East can be very helpful in understanding the current distribution patterns and etiology of refractive errors compared to the previous decade.

  15. School-based approaches to the correction of refractive error in children.

    Science.gov (United States)

    Sharma, Abhishek; Congdon, Nathan; Patel, Mehul; Gilbert, Clare

    2012-01-01

    The World Health Organization estimates that 13 million children aged 5-15 years worldwide are visually impaired from uncorrected refractive error. School vision screening programs can identify and treat or refer children with refractive error. We concentrate on the findings of various screening studies and attempt to identify key factors in the success and sustainability of such programs in the developing world. We reviewed original and review articles describing children's vision and refractive error screening programs published in English and listed in PubMed, Medline OVID, Google Scholar, and Oxford University Electronic Resources databases. Data were abstracted on study objective, design, setting, participants, and outcomes, including accuracy of screening, quality of refractive services, barriers to uptake, impact on quality of life, and cost-effectiveness of programs. Inadequately corrected refractive error is an important global cause of visual impairment in childhood. School-based vision screening carried out by teachers and other ancillary personnel may be an effective means of detecting affected children and improving their visual function with spectacles. The need for services and potential impact of school-based programs varies widely between areas, depending on prevalence of refractive error and competing conditions and rates of school attendance. Barriers to acceptance of services include the cost and quality of available refractive care and mistaken beliefs that glasses will harm children's eyes. Further research is needed in areas such as the cost-effectiveness of different screening approaches and impact of education to promote acceptance of spectacle-wear. School vision programs should be integrated into comprehensive efforts to promote healthy children and their families. Copyright © 2012 Elsevier Inc. All rights reserved.

  16. Uncorrected refractive error in older British adults: the EPIC-Norfolk Eye Study.

    Science.gov (United States)

    Sherwin, Justin C; Khawaja, Anthony P; Broadway, David; Luben, Robert; Hayat, Shabina; Dalzell, Nichola; Wareham, Nicholas J; Khaw, Kay-Tee; Foster, Paul J

    2012-07-01

    To investigate the prevalence of, and demographic associations with, uncorrected refractive error (URE) in an older British population. Data from 4428 participants, aged 48-89 years, who attended an eye examination in the third health check of the European Prospective Investigation into Cancer-Norfolk study and had also undergone an ophthalmic examination were assessed. URE was defined as ≥1 line improvement of visual acuity with pinhole-correction in the better eye in participants with LogMar presenting visual acuity (PVA) Refractive error was measured using an autorefractor without cycloplegia. Myopia was defined as spherical equivalent ≤-0.5 dioptre, and hypermetropia ≥0.5 dioptre. Adjusted to the 2010 midyear British population, the prevalence of URE in this Norfolk population was 1.9% (95% CI 0.6% to 3.1%). Lower self-rated distance vision was correlated with higher prevalence of URE (p(trend)refractive error. Wearing distance spectacles was inversely associated with URE (OR 0.34, 95% CI 0.21 to 0.55, prefractive error (prefractive error (p(trend)refractive error is common, the prevalence of URE was found to be low in this population reflecting a low prevalence of PVA<0.3.

  17. Refractive errors, visual impairment, and the use of low-vision devices in albinism in Malawi.

    Science.gov (United States)

    Schulze Schwering, M; Kumar, N; Bohrmann, D; Msukwa, G; Kalua, K; Kayange, P; Spitzer, M S

    2015-04-01

    This study focuses on the refractive implications of albinism in Malawi, which is mostly associated with the burden of visual impairment. The main goal was to describe the refractive errors and to analyze whether patients with albinism in Malawi, Sub-Saharan Africa, benefit from refraction. Age, sex, refractive data, uncorrected and best-corrected visual acuity (UCVA, BCVA), colour vision, contrast sensitivity, and the prescription of sunglasses and low vision devices were collected for a group of 120 albino individuals with oculocutaneous albinism (OCA). Refractive errors were evaluated objectively and subjectively by retinoscopy, and followed by cycloplegic refraction to reconfirm the results. Best-corrected visual acuity (BCVA) was also assessed binocularly. One hundred and twenty albino subjects were examined, ranging in age from 4 to 25 years (median 12 years), 71 (59 %) boys and 49 (41 %) girls. All exhibited horizontal pendular nystagmus. Mean visual acuity improved from 0.98 (0.33) logMAR to 0.77 (0.15) logMAR after refraction (p albinism who were hyperopic more than +1.5 D hardly improved from refraction. With the rule (WTR) astigmatism was more present (37.5 %) than against the rule (ATR) astigmatism (3.8 %). Patients with astigmatism less than 1.5 D improved in 15/32 of cases (47 %) by 2 lines or more. Patients with astigmatism equal to or more than 1.5 D in any axis improved in 26/54 of cases (48 %) by 2 lines or more. Refraction improves visual acuity of children with oculocutaneous albinism in a Sub-Saharan African population in Malawi. The mean improvement was 2 logMAR units.

  18. Role of Refractive Errors in Inducing Asthenopic Symptoms Among Spectacle Corrected Ammetropes

    Directory of Open Access Journals (Sweden)

    Padma B Prabhu

    2016-04-01

    Full Text Available Refractive errors are a major cause of asthenopic symptoms in young age group. Aim and objectives: This study tries to ascertain the prevalence of refractive errors in a cohort of subjects with spectacle corrected ammetropia and to elucidate the relation between the type, severity and subcategories of refractive errors in such a group. Design: Descriptive cross sectional study Methods: This is a prospective analysis of cases with asthenopia and coexistant significant refractive errors warranting use of spectacles. Best corrected visual acuity of 20/20 was ensured. Retinoscopy readings after complete cycloplegia were noted. Spherical equivalent was calculated from the absolute retinoscopy reading. Ammetropia not fully corrected with spectacles, history of migraine, headache not related to constant near work, symptoms less than three months duration, associated accomodation-convergence anomalies and latent squints were excluded. Results: The study group included thirty five patients. The mean age was 23.48 years; SD 6.97. There were 15 males and 20 females. Twenty seven patients had bilateral symptoms (77.14%. Thirty six subjects (58.08% had a spherical equivalent between 0.25D to 0.75D. The refractive errors included myopia (n-10, hypermetropia (n-26 and astigmatism (n-26. Near work associated headache was observed in 39 patients (62.86%. 46.15% of the cases with near work related headache had uncorrected astigmatism. Conclusion: Asthenopic symptoms are frequent and significant among spectacle corrected ammetropes. Lower degrees of refractive errors are more symptomatic. Hypermetropia and astigmatism constitute the major causative factors.

  19. Prevalence of refractive error in rural Myanmar: the Meiktila Eye Study.

    Science.gov (United States)

    Gupta, A; Casson, R J; Newland, H S; Muecke, J; Landers, J; Selva, D; Aung, T

    2008-01-01

    To determine the prevalence of refractive error and associated risk factors in the Meiktila District of central rural Myanmar. Population-based cross-sectional study. Randomized stratified cluster sampling of the inhabitants 40 years or older from villages in Meiktila was performed; 2481 eligible participants were identified, 2076 participated in the study, and adequate refractive data were obtained on 1863 individuals (75.1%). Demographic data including age, gender, and education level were obtained from all participants. The ophthalmic examination included autorefraction, nuclear opalescence (NO) grading at the slit lamp, and applanation tonometry. Refractive errors were classified by type of ametropia and their prevalence was determined. Univariate and multivariate analyses were performed and odds ratios were calculated for the predictors of refractive error within the statistical models. Mean refractive error measured -1.3 diopters (D) (standard deviation [SD], 2.9) and mean cylindrical error measured 1.1 D (SD, 1.5). Myopia of >-1.0 and >-6.0 D occurred in 42.7% (95% confidence interval [CI], 40.4%-44.9%) and 6.5% (95% CI, 5.4%-7.6%) of subjects, respectively. Myopic refractive error was associated significantly with a higher degree of NO (P+1.0 D occurred in 15% (95% CI, 5.4%-7.6%) of the population and was associated with higher education levels (Pprevalent in older subjects and in those with increased NO. The prevalence rates of myopia in the > or =40 age group are higher than those found in other Asian regions and are likely to contribute to visual impairment.

  20. Screening of primary school children for refractive error in South-South Nigeria.

    Science.gov (United States)

    Opubiri, Ibeinmo; Pedro-Egbe, Chinyere Nnenne

    2012-07-01

    Vision screening study in primary school children has not been done in Bayelsa State, South-South Nigeria. This study was therefore conducted to screen primary school children for refractive error in Bayelsa State and use the data to plan for an effective school Eye Health Program. A cross sectional study on screening for refractive error in school children was carried out in Yenagoa Local Government Area of Bayelsa State in June 2009. A multistage sampling technique was used to select the study population (pupils aged 5-15 years). Visual acuity for each eye was assessed by an Ophthalmic nurse and Optometrist outside the classroom, at 6 meters distance. Those with visual acuity of 6/9 or less were presented with a pinhole and the test repeated. Improvement of visual acuity with pinhole was considered refractive error. Funduscopy was done inside a poorly lit classroom. Data was analyzed with EPI INFO version 6. A total of 1,242 (658 females and 584 males) Pupils were examined. About 97.7% of eyes had normal vision of 6/6 while 49 out of 56 eyes, with visual acuity of 6/9 or less, improved with pinhole. Twenty seven pupils had refractive error, giving a prevalence of 2.2%. Refractive error involved both eyes in 22 pupils (81.5%) with the 8-10 years age range having the highest proportion (40.7%) of cases followed by 11-13 years age range (37.0%). The prevalence of refractive error in school children in Bayelsa State, South-South Nigeria was low.

  1. PREVALENCE OF REFRACTIVE ERRORS AMONG CHILDREN IN RURA L AREAS OF CHITTOOR DISTRICT, A . P

    Directory of Open Access Journals (Sweden)

    Sadana

    2015-08-01

    Full Text Available BACKGROUND: The uncorrected refractive errors are the main cause of low vision which hampers performance at school, reduces productivity and impairs quality of life. It is considered to be one of the most important priorities in the global initiation for the elimination of avoidable blindness. The refractive errors are especially common among children as they do not complain and adjust with circumstances. School children constitute an ideal group for study of refractive errors because most of them go to school, easily accessible and offer excellent opportunity for services and health education. MATERIAL & METHODS: This is a cross sectional study conducted among 2,568 children attending various government schools in the rural areas of Chittoor district. The study was carried out during January to June 2015. A preliminary examination of visual acuity was determined by Snellen’s chart and those with defective vision were subjected to detailed eye examination by a specialist. The results were analyzed using MS excel software and Epiinfo 7 software version using percentages and Chi - square test. RESULTS: The overall prevalence of refractive errors among children was found to be 11.3%. (Astigmatism - 5.8%; myopia - 4.2%; hypermetropia - 1.4%. The prevalence of refractive errors increased steadily from 5.7% in 5 - 7 years age group to 14.7% in 14 - 16 years group. The prevalence was found to be similar in male and female children. The prevalence of myopia and astigmatism was found to increase steadily with age while hypermetropia showed an inverse trend CONCLUSIONS: Examination of school children for refractive errors is a useful strategy for early diagnosis and intervention.

  2. Rapid Assessment of Refractive Error, Presbyopia, and Visual Impairment and Associated Quality of Life in Nampula, Mozambique

    OpenAIRE

    Loughman, James; Nxele, Lindelwa; Faria, Cesar; Thompson, Stephen; Ramson, Prasidh; Chinanyi, Farai; Naidoo, Kovin S.

    2015-01-01

    Introduction: Uncorrected refractive error is the leading cause of visual impairment worldwide and leads to an impaired quality of life. This study was designed to determine the prevalence of uncorrected refractive error and presbyopia, to assess spectacle coverage, and to evaluate visual health-related quality of life among persons aged 15–50 years old in Nampula, Mozambique. Methods: Participants were assessed using a validated rapid assessment of refractive error protocol, comprised of ...

  3. Refractive error study in young subjects: results from a rural area in Paraguay

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    Isabel Signes-Soler

    2017-03-01

    Full Text Available AIM: To evaluate the distribution of refractive error in young subjects in a rural area of Paraguay in the context of an international cooperation campaign for the prevention of blindness. METHODS: A sample of 1466 young subjects (ranging from 3 to 22 years old, with a mean age of 11.21±3.63 years old, were examined to assess their distance visual acuity (VA and refractive error. The first screening examination performed by trained volunteers, included visual acuity testing, autokeratometry and non-cycloplegic autorefraction. Inclusion criteria for a second complete cycloplegic eye examination by an optometrist were VA <20/25 (0.10 logMAR or 0.8 decimal and/or corneal astigmatism ≥1.50 D. RESULTS: An uncorrected distance VA of 0 logMAR (1.0 decimal was found in 89.2% of children. VA <20/25 and/or corneal astigmatism ≥1.50 D was found in 3.9% of children (n=57, with a prevalence of hyperopia of 5.2% (0.2% of the total in this specific group. Furthermore, myopia (spherical equivalent ≤-0.5 D was found in 37.7% of the refracted children (0.5% of the total. The prevalence of refractive astigmatism (cylinder ≤-1.50 D was 15.8% (0.6% of the total. Visual impairment (VI (0.05≤VA≤0.3 was found in 12/114 (0.4% of the refracted eyes. Main causes for VI were refractive error (58%, retinal problems (17%, 2/12, albinism (17%, 2/12 and unknown (8%, 1/12. CONCLUSION: A low prevalence of refractive error has been found in this rural area of Paraguay, with higher prevalence of myopia than of hyperopia.

  4. Incidence of the refractive errors in children 3 to 9 years of age, in the city of Tetovo, Macedonia

    Directory of Open Access Journals (Sweden)

    Ejup Mahmudi

    2013-01-01

    Conclusions: The study showed a considerable prevalence rates of refractive errors myopia, hypermethropia, astigmatism and amblyopia at children of 3-9 years of age in Tetovo. There was no correlation between sex of the children's and the refractive errors founds. There was a correlation with the need for corrective spectacles and the refractive errors they represent. Refractive errors was registered in high percentage at rural area than in urban area. Although with best corrected vision the prevalence of impairment was less in urban than in rural populations, blindness remained nearly twice as high in the rural population as in the urban population with both baseline and best corrected visual acuity.

  5. Breastfeeding and association with refractive error in young Singapore Chinese children.

    Science.gov (United States)

    Sham, W K; Dirani, M; Chong, Y S; Hornbeak, D M; Gazzard, G; Li, J; Saw, S M

    2010-05-01

    The objective of this study was to investigate an association between spherical refractive error and breastfeeding. Strabismus, amblyopia, and refractive errors in Singaporean preschoolers (STARS) is a cross-sectional population-based study of 3009 Chinese children aged 6-72 months conducted between June 2006 and September 2008 in Singapore. Parents were asked about the history of breastfeeding in face-to-face interviews. Children without cycloplegia or without refraction assessment were excluded. The final sample analysed was 2639 children (1375 male, 1264 female). Out of those who were breastfed, 842 (41.3%) were breastfed for more than 3 months and 599 (29.4%) were breastfed longer than 6 months. The prevalence of myopia, defined as the spherical equivalent refraction of the right eye of at least -0.5 dioptres (D), was 11.3% (95% CI (10.1, 12.5)). The mean spherical equivalent refraction of breastfed children was 0.12 D higher than that of children who were not breastfed (P-value=0.03). Breastfeeding, however, was not associated with myopia (adjusted OR=0.85; 95% CI (0.62, 1.18)). The results show that breastfeeding is associated with more hyperopic spherical equivalent refraction in young Chinese children in Singapore.

  6. Refractive error in Chinese with type 2 diabetes and its association with glycaemic control.

    Science.gov (United States)

    Song, E; Qian, Deng-Juan; Wang, Shan; Xu, Cailian; Pan, Chen-Wei

    2018-03-01

    The aim of this study was to determine the prevalence of refractive errors and their association with glycaemic control among adults with type 2 diabetes mellitus (T2DM) in eastern China. A community-based survey, including 913 adults with T2DM aged 30 to 89 years, was conducted. Refractive error was assessed by autorefraction, after which subjective refraction was performed. Ocular biometric parameters were measured by non-contact partial coherence laser interferometry. Myopia was defined as spherical equivalent (SE) less than -0.50 dioptres (D), high myopia as SE less than -5.00 D, hyperopia as SE greater than 0.50 D and astigmatism as cylinder less than -0.50 D. After excluding participants who had undergone cataract surgery, 839 were included in the data analyses and 96.1 per cent were found to have refractive errors. The overall prevalences of myopia, high myopia, hyperopia and astigmatism were 28.2 per cent (95 per cent confidence interval [CI] 25.2-31.3), 6.3 per cent (95 per cent CI 4.7-8.0), 46.4 per cent (95 per cent CI 43.0-49.7) and 81.0 per cent (95 per cent CI 78.4-83.7) with no gender differences observed (all p > 0.10). In multivariate analysis, myopia was associated with decreasing age (odds ratio [OR] = 0.86, p = 0.01; per year increase), higher blood levels of haemoglobin A 1c (HbA 1c ) (OR = 1.12, p = 0.05; per unit increase), higher education levels (OR = 5.10, p Refractive errors may be associated with glycaemic control among T2DM patients. Longitudinal analyses are warranted to examine the relationship between changes in HbA 1c and the development of refractive errors. © 2017 Optometry Australia.

  7. Refractive error in school children in an urban and rural setting in Cambodia.

    Science.gov (United States)

    Gao, Zoe; Meng, Ngy; Muecke, James; Chan, Weng Onn; Piseth, Horm; Kong, Aimee; Jnguyenphamhh, Theresa; Dehghan, Yalda; Selva, Dinesh; Casson, Robert; Ang, Kim

    2012-02-01

    To assess the prevalence of refractive error in schoolchildren aged 12-14 years in urban and rural settings in Cambodia's Phnom Penh and Kandal provinces. Ten schools from Phnom Penh Province and 26 schools from Kandal Province were randomly selected and surveyed in October 2010. Children were examined by teams of Australian and Cambodian optometrists, ophthalmic nurses and ophthalmologists who performed visual acuity (VA) testing and cycloplegic refraction. A total of 5527 children were included in the study. The prevalence of uncorrected, presenting and best-corrected VA ≤ 6/12 in the better eye were 2.48% (95% confidence interval [CI] 2.02-2.83%), 1.90% (95% CI 1.52-2.24%) and 0.36% (95% CI 0.20-0.52%), respectively; 43 children presented with glasses whilst a total of 315 glasses were dispensed. The total prevalence of refractive error was 6.57% (95% CI 5.91-7.22%), but there was a significant difference between urban (13.7%, 95% CI 12.2-15.2%) and rural (2.5%, 95% CI 2.03-3.07%) schools (P Refractive error accounted for 91.2% of visually impaired eyes, cataract for 1.7%, and other causes for 7.1%. Myopia (spherical equivalent ≤ -0.50 diopters [D] in either eye) was associated with increased age, female gender and urban schooling. The prevalence of refractive error was significantly higher in urban Phnom Penh schools than rural schools in Kandal Province. The prevalence of refractive error, particularly myopia was relatively low compared to previous reports in Asia. The majority of children did not have appropriate correction with spectacles, highlighting the need for more effective screening and optical intervention.

  8. Prevalence and associated risk factors of undercorrected refractive errors among people with diabetes in Shanghai.

    Science.gov (United States)

    Zhu, Mengjun; Tong, Xiaowei; Zhao, Rong; He, Xiangui; Zhao, Huijuan; Zhu, Jianfeng

    2017-11-28

    To investigate the prevalence and risk factors of undercorrected refractive error (URE) among people with diabetes in the Baoshan District of Shanghai, where data for undercorrected refractive error are limited. The study was a population-based survey of 649 persons (aged 60 years or older) with diabetes in Baoshan, Shanghai in 2009. One copy of the questionnaire was completed for each subject. Examinations included a standardized refraction and measurement of presenting and best-corrected visual acuity (BCVA), tonometry, slit lamp biomicroscopy, and fundus photography. The calculated age-standardized prevalence rate of URE was 16.63% (95% confidence interval [CI] 13.76-19.49). For visual impairment subjects (presenting vision worse than 20/40 in the better eye), the prevalence of URE was up to 61.11%, and 75.93% of subjects could achieve visual acuity improvement by at least one line using appropriate spectacles. Under multiple logistic regression analysis, older age, female gender, non-farmer, increasing degree of myopia, lens opacities status, diabetic retinopathy (DR), body mass index (BMI) index lower than normal, and poor glycaemic control were associated with higher URE levels. Wearing distance eyeglasses was a protective factor for URE. The undercorrected refractive error in diabetic adults was high in Shanghai. Health education and regular refractive assessment are needed for diabetic adults. Persons with diabetes should be more aware that poor vision is often correctable, especially for those with risk factors.

  9. Three-dimensional ray-tracing model for the study of advanced refractive errors in keratoconus.

    Science.gov (United States)

    Schedin, Staffan; Hallberg, Per; Behndig, Anders

    2016-01-20

    We propose a numerical three-dimensional (3D) ray-tracing model for the analysis of advanced corneal refractive errors. The 3D modeling was based on measured corneal elevation data by means of Scheimpflug photography. A mathematical description of the measured corneal surfaces from a keratoconus (KC) patient was used for the 3D ray tracing, based on Snell's law of refraction. A model of a commercial intraocular lens (IOL) was included in the analysis. By modifying the posterior IOL surface, it was shown that the imaging quality could be significantly improved. The RMS values were reduced by approximately 50% close to the retina, both for on- and off-axis geometries. The 3D ray-tracing model can constitute a basis for simulation of customized IOLs that are able to correct the advanced, irregular refractive errors in KC.

  10. Prevalence and Risk Factors for Refractive Error in Adult Chinese Americans: The Chinese American Eye Study.

    Science.gov (United States)

    Varma, Rohit; Torres, Mina; McKean-Cowdin, Roberta; Rong, Fen; Hsu, Chunyi; Jiang, Xuejuan

    2017-03-01

    To estimate the prevalence of refractive errors in adult Chinese Americans, and to evaluate factors associated with myopia and high myopia. A population-based, cross-sectional study. Chinese Americans 50 years and older residing in Monterey Park, California, were recruited. Noncycloplegic automated refraction with supplemental subjective refraction was performed. Myopia, high myopia, hyperopia, and high hyperopia were defined as a spherical equivalent of +0.5 D, and ≥+3.0 D, respectively. Astigmatism and high astigmatism were defined as a cylinder of >0.5 D and >2.25 D, respectively. Risk factor assessment was guided by a conceptual model. Data from 4144 participants were analyzed. The overall prevalence of myopia, high myopia, hyperopia, high hyperopia, astigmatism, and high astigmatism in the right eye was 35.1% (95% confidence interval, 33.6%-36.6%), 7.4% (6.6%-8.3%), 40.2% (38.7%-41.8%), 2.7% (2.2%-3.3%), 45.6% (44.1%-47.2%), and 3.7% (3.1%-4.3%), respectively. The prevalence of myopia and high myopia was lower among older individuals (P refractive errors (P prevalence of refractive errors, except for a higher prevalence of hyperopia among female subjects (P = .010). Age, acculturation, education, income, marital status, birth country, history of ocular disease, nonocular comorbidities, and recent eye examination were associated with prevalence of myopia. All of these factors, except for acculturation, were also associated with high myopia. Our data present the first population-based estimates of the prevalence of refractive errors among adult Chinese Americans. Compared with whites, Hispanics, and blacks, Chinese Americans have a higher burden of myopia, high myopia, and astigmatism. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. Prevalence of Refractive Error in Adult Chinese Americans: The Chinese American Eye Study

    Science.gov (United States)

    Varma, Rohit; Torres, Mina; McKean-Cowdin, Roberta; Rong, Fen; Hsu, Chunyi; Jiang, Xuejuan

    2016-01-01

    Purpose To estimate the prevalence of refractive errors in adult Chinese Americans, and evaluate factors associated with myopia and high myopia. Design A population-based, cross-sectional study. Methods Chinese Americans 50 years and older residing in Monterey Park, California, were recruited. Noncycloplegic automated refraction with supplemental subjective refraction was performed. Myopia, high myopia, hyperopia, and high hyperopia were defined as a spherical equivalent of +0.5D, and ≥ +3.0D, respectively. Astigmatism and high astigmatism were defined as a cylinder of > 0.5D and > 2.25D, respectively. Risk factor assessment was guided by a conceptual model. Results Data from 4144 participants were analyzed. The overall prevalence of myopia, high myopia, hyperopia, high hyperopia, astigmatism, and high astigmatism was 35.1% (95% confidence interval, 33.6%–36.6%), 7.4% (6.6%–8.3%), 40.2% (38.7%–41.8%), 2.7% (2.2%–3.3%), 45.6% (44.1%–47.2%), and 3.7% (3.1%–4.3%), respectively. The prevalence of myopia and high myopia was lower among older individuals (Ps refractive errors (Ps prevalence of refractive errors, except for a higher prevalence of hyperopia among females (P = 0.010). Age, acculturation, education, income, marital status, birth country, history of ocular disease, non-ocular comorbidities, and recent eye exam were associated with prevalence of myopia. All of these factors, except for acculturation, were also associated with high myopia. Conclusions Our data present the first population-based estimates of the prevalence of refractive errors among adult Chinese Americans. Compared with whites, Hispanics, and blacks, Chinese Americans have a higher burden of myopia, high myopia, and astigmatism. PMID:27769895

  12. The Effect of Age, Accommodation, and Refractive Error on the Adult Human Eye.

    Science.gov (United States)

    Richdale, Kathryn; Bullimore, Mark A; Sinnott, Loraine T; Zadnik, Karla

    2016-01-01

    To quantify changes in ocular dimensions associated with age, refractive error, and accommodative response, in vivo, in 30- to 50-year-old human subjects. The right eyes of 91 adults were examined using ultrasonography, phakometry, keratometry, pachymetry, interferometry, anterior segment optical coherence tomography, and high-resolution magnetic resonance imaging. Accommodation was measured subjectively with a push-up test and objectively using open-field autorefraction. Regression analyses were used to assess differences in ocular parameters with age, refractive error, and accommodation. With age, crystalline lens thickness increased (0.03 mm/yr), anterior lens curvature steepened (0.11 mm/yr), anterior chamber depth decreased (0.02 mm/yr), and lens equivalent refractive index decreased (0.001/yr) (all p error is significantly correlated with not only the axial dimensions but also the anterior equatorial dimension of the adult eye. Further testing and development of accommodating intraocular lenses should account for differences in patients' preoperative refractive error.

  13. Development of refractive error and strabismus in children with Down syndrome

    NARCIS (Netherlands)

    Cregg, M; Woodhouse, JM; Stewart, Ruth E.; Pakeman, VH; Bromham, NR; Gunter, HL; Trojanowska, L; Parker, M; Fraser, WI

    PURPOSE. To investigate the development of refractive errors and strabismus in a cohort of children with Down syndrome. METHOD. Data for 55 children with Down syndrome who are participating in this longitudinal study of visual development, first examined by us when aged less than 2 years and on at

  14. Association between childhood strabismus and refractive error in Chinese preschool children.

    Science.gov (United States)

    Zhu, Hui; Yu, Jia-Jia; Yu, Rong-Bin; Ding, Hui; Bai, Jing; Chen, Ji; Liu, Hu

    2015-01-01

    To investigate the association between concomitant esotropia or concomitant exotropia and refractive error in preschool children. A population-based sample of 5831 children aged 3 to 6 years was selected from all kindergartens in a representative county (Yuhuatai District, Nanjing, Jiangsu Province) of Nanjing, China. Clinical examinations including ocular alignment, ocular motility, visual acuity, optometry, stereopsis screening, slit lamp examination and fundus examination were performed by trained ophthalmologists and optometrists. Odd ratios (OR) and 95% confidence intervals (95% CI) were calculated to evaluate the association of refractive error with concomitant esotropia and concomitant exotropia. In multivariate logistic regression analysis, concomitant esotropia was associated independently with spherical equivalent anisometropia (OR, 3.15 for 0.50 to = 1.00 D of anisometropia) and hyperopia. There was a severity-dependent association of hyperopia with the development of concomitant esotropia, with ORs increasing from 9.3 for 2.00 to = 5.00 D of hyperopia. Concomitant exotropia was associated with astigmatism (OR, 3.56 for 0.50 to 1.00 D of astigmatism, and 1.9 for refractive error and the prevalence of concomitant esotropia and concomitant exotropia, which should be considered when managing childhood refractive error.

  15. The prevalence of refractive errors in 6- to 15-year-old schoolchildren in Dezful, Iran

    Directory of Open Access Journals (Sweden)

    Reza Norouzirad

    2015-03-01

    Conclusion: This study showed a considerably high prevalence of refractive errors among the Iranian population of schoolchildren in Dezful in the west of Iran. The prevalence of myopia is considerably high compared to previous studies in Iran and increases with age.

  16. A Meta-Analysis for Association of Maternal Smoking with Childhood Refractive Error and Amblyopia

    Directory of Open Access Journals (Sweden)

    Li Li

    2016-01-01

    Full Text Available Background. We aimed to evaluate the association between maternal smoking and the occurrence of childhood refractive error and amblyopia. Methods. Relevant articles were identified from PubMed and EMBASE up to May 2015. Combined odds ratio (OR corresponding with its 95% confidence interval (CI was calculated to evaluate the influence of maternal smoking on childhood refractive error and amblyopia. The heterogeneity was evaluated with the Chi-square-based Q statistic and the I2 test. Potential publication bias was finally examined by Egger’s test. Results. A total of 9 articles were included in this meta-analysis. The pooled OR showed that there was no significant association between maternal smoking and childhood refractive error. However, children whose mother smoked during pregnancy were 1.47 (95% CI: 1.12–1.93 times and 1.43 (95% CI: 1.23-1.66 times more likely to suffer from amblyopia and hyperopia, respectively, compared with children whose mother did not smoke, and the difference was significant. Significant heterogeneity was only found among studies involving the influence of maternal smoking on children’s refractive error (P<0.05; I2=69.9%. No potential publication bias was detected by Egger’s test. Conclusion. The meta-analysis suggests that maternal smoking is a risk factor for childhood hyperopia and amblyopia.

  17. contribution of refractive errors to visual im- pairment in patients at ...

    African Journals Online (AJOL)

    DOfori-Adjei

    2007-06-01

    Jun 1, 2007 ... standard deviation 2.9. The rest of the patients were 16 to 87 years old with a mean age of 37, median 32, and standard deviation 17.4. About. 1% of the study group (children excluded) were professionals or in the managerial positions. Table 1 Summary: visual impairment (VI) and refractive error (RE).

  18. Prevalence of Refractive Error in a Rural Ogoni Community in Souther

    African Journals Online (AJOL)

    Department of Ophthalmology, University of Port Harcourt Teaching Hospital, Port Harcourt. 2 ... Refractive error is a common cause of impaired vision, and ... 6 impaired, 10% had severe visual impairment, and 1% was blind. It was estimated that about 1.5 million Nigerian. 6 adults need spectacles for distant vision. Studies ...

  19. Refractive Error in a Sample of Black High School Children in South Africa.

    Science.gov (United States)

    Wajuihian, Samuel Otabor; Hansraj, Rekha

    2017-12-01

    This study focused on a cohort that has not been studied and who currently have limited access to eye care services. The findings, while improving the understanding of the distribution of refractive errors, also enabled identification of children requiring intervention and provided a guide for future resource allocation. The aim of conducting the study was to determine the prevalence and distribution of refractive error and its association with gender, age, and school grade level. Using a multistage random cluster sampling, 1586 children, 632 males (40%) and 954 females (60%), were selected. Their ages ranged between 13 and 18 years with a mean of 15.81 ± 1.56 years. The visual functions evaluated included visual acuity using the logarithm of minimum angle of resolution chart and refractive error measured using the autorefractor and then refined subjectively. Axis astigmatism was presented in the vector method where positive values of J0 indicated with-the-rule astigmatism, negative values indicated against-the-rule astigmatism, whereas J45 represented oblique astigmatism. Overall, patients were myopic with a mean spherical power for right eye of -0.02 ± 0.47; mean astigmatic cylinder power was -0.09 ± 0.27 with mainly with-the-rule astigmatism (J0 = 0.01 ± 0.11). The prevalence estimates were as follows: myopia (at least -0.50) 7% (95% confidence interval [CI], 6 to 9%), hyperopia (at least 0.5) 5% (95% CI, 4 to 6%), astigmatism (at least -0.75 cylinder) 3% (95% CI, 2 to 4%), and anisometropia 3% (95% CI, 2 to 4%). There was no significant association between refractive error and any of the categories (gender, age, and grade levels). The prevalence of refractive error in the sample of high school children was relatively low. Myopia was the most prevalent, and findings on its association with age suggest that the prevalence of myopia may be stabilizing at late teenage years.

  20. Refractive Errors in Koreans: The Korea National Health and Nutrition Examination Survey 2008-2012.

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    Rim, Tyler Hyungtaek; Kim, Seung-Hyun; Lim, Key Hwan; Choi, Moonjung; Kim, Hye Young; Baek, Seung-Hee

    2016-06-01

    Our study provides epidemiologic data on the prevalence of refractive errors in all age group ≥5 years in Korea. In 2008 to 2012, a total of 33,355 participants aged ≥5 years underwent ophthalmologic examinations. Using the right eye, myopia was defined as a spherical equivalent (SE) less than -0.5 or -1.0 diopters (D) in subjects aged 19 years and older or as an SE less than -0.75 or -1.25 D in subjects aged 5 to 18 years according to non-cycloplegic refraction. Other refractive errors were defined as follows: high myopia as an SE less than -6.0 D; hyperopia as an SE larger than +0.5 D; and astigmatism as a cylindrical error less than -1.0 D. The prevalence and risk factors of myopia were evaluated. Prevalence rates with a 95% confidence interval were determined for myopia (SE prevalence of myopia demonstrated a nonlinear distribution with the highest peak between the ages of 19 and 29 years. The prevalence of hyperopia decreased with age in subjects aged 39 years or younger and then increased with age in subjects aged 40 years or older. The prevalence of astigmatism gradually increased with age. Education was associated with all refractive errors; myopia was more prevalent and hyperopia and astigmatism were less prevalent in the highly educated groups. In young generations, the prevalence of myopia in Korea was much higher compared to the white or black populations in Western countries and is consistent with the high prevalence found in most other Asian countries. The overall prevalence of hyperopia was much lower compared to that of the white Western population. Age and education level were significant predictive factors associated with all kinds of refractive errors.

  1. Assumption-free estimation of the genetic contribution to refractive error across childhood.

    Science.gov (United States)

    Guggenheim, Jeremy A; St Pourcain, Beate; McMahon, George; Timpson, Nicholas J; Evans, David M; Williams, Cathy

    2015-01-01

    Studies in relatives have generally yielded high heritability estimates for refractive error: twins 75-90%, families 15-70%. However, because related individuals often share a common environment, these estimates are inflated (via misallocation of unique/common environment variance). We calculated a lower-bound heritability estimate for refractive error free from such bias. Between the ages 7 and 15 years, participants in the Avon Longitudinal Study of Parents and Children (ALSPAC) underwent non-cycloplegic autorefraction at regular research clinics. At each age, an estimate of the variance in refractive error explained by single nucleotide polymorphism (SNP) genetic variants was calculated using genome-wide complex trait analysis (GCTA) using high-density genome-wide SNP genotype information (minimum N at each age=3,404). The variance in refractive error explained by the SNPs ("SNP heritability") was stable over childhood: Across age 7-15 years, SNP heritability averaged 0.28 (SE=0.08, pchildhood. Simulations suggested lack of cycloplegia during autorefraction led to a small underestimation of SNP heritability (adjusted SNP heritability=0.35; SE=0.09). To put these results in context, the variance in refractive error explained (or predicted) by the time participants spent outdoors was time spent reading was childhood. Notwithstanding the strong evidence of association between time outdoors and myopia, and time reading and myopia, less than 1% of the variance in myopia at age 15 was explained by crude measures of these two risk factors, indicating that their effects may be limited, at least when averaged over the whole population.

  2. Psychometric properties of the national eye institute refractive error correction quality-of-life questionnaire among Iranian patients

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    Amir H Pakpour

    2013-01-01

    Conclusions: The Iranian version of the NEI-RQL-42 is a valid and reliable instrument to assess refractive error correction quality-of-life in Iranian patients. Moreover this questionnaire can be used to evaluate the effectiveness of interventions in patients with refractive errors.

  3. Prevalence and risk factors of undercorrected refractive errors among Singaporean Malay adults: the Singapore Malay Eye Study.

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    Rosman, Mohamad; Wong, Tien Y; Tay, Wan-Ting; Tong, Louis; Saw, Seang-Mei

    2009-08-01

    To describe the prevalence and the risk factors of undercorrected refractive error in an adult urban Malay population. This population-based, cross-sectional study was conducted in Singapore in 3280 Malay adults, aged 40 to 80 years. All individuals were examined at a centralized clinic and underwent standardized interviews and assessment of refractive errors and presenting and best corrected visual acuities. Distance presenting visual acuity was monocularly measured by using a logarithm of the minimum angle of resolution (logMAR) number chart at a distance of 4 m, with the participants wearing their "walk-in" optical corrections (spectacles or contact lenses), if any. Refraction was determined by subjective refraction by trained, certified study optometrists. Best corrected visual acuity was monocularly assessed and recorded in logMAR scores using the same test protocol as was used for presenting visual acuity. Undercorrected refractive error was defined as an improvement of at least 0.2 logMAR (2 lines equivalent) in the best corrected visual acuity compared with the presenting visual acuity in the better eye. The mean age of the subjects included in our study was 58 +/- 11 years, and 52% of the subjects were women. The prevalence rate of undercorrected refractive error among Singaporean Malay adults in our study (n = 3115) was 20.4% (age-standardized prevalence rate, 18.3%). More of the women had undercorrected refractive error than the men (21.8% vs. 18.8%, P = 0.04). Undercorrected refractive error was also more common in subjects older than 50 years than in subjects aged 40 to 49 years (22.6% vs. 14.3%, P Malay adults with refractive errors was higher than that of the Singaporean Chinese adults with refractive errors. Undercorrected refractive error is a significant cause of correctable visual impairment among Singaporean Malay adults, affecting one in five persons.

  4. Refractive errors in a rural Korean adult population: the Namil Study

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    Yoo, Y C; Kim, J M; Park, K H; Kim, C Y; Kim, T-W

    2013-01-01

    Purpose To assess the prevalence of refractive errors, including myopia, high myopia, hyperopia, astigmatism, and anisometropia, in rural adult Koreans. Methods We identified 2027 residents aged 40 years or older in Namil-myeon, a rural town in central South Korea. Of 1928 eligible residents, 1532 subjects (79.5%) participated. Each subject underwent screening examinations including autorefractometry, corneal curvature measurement, and best-corrected visual acuity. Results Data from 1215 phakic right eyes were analyzed. The prevalence of myopia (spherical equivalent (SE) +0.5 D) was 41.8% (95% CI: 38.9−44.4%), of astigmatism (cylinder 1.0 D) was 13.8% (95% CI: 11.9−15.8%). Myopia prevalence decreased with age and tended to transition into hyperopia with age up to 60−69 years. In subjects older than this, the trend in SE refractive errors reversed with age. The prevalence of astigmatism and anisometropia increased consistently with age. The refractive status was not significantly different between males and females. Conclusions The prevalence of myopia and hyperopia in rural adult Koreans was similar to that of rural Chinese. The prevalence of high myopia was lower in this Korean sample than in other East Asian populations, and astigmatism was the most frequently occurring refractive error. PMID:24037232

  5. [The analysis of refractive error of long axial high myopic eyes after IOL implantation].

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    Zheng, Qian; Zhao, Zhennan; Lian, Hengli; Zhao, Yun'e

    2015-04-01

    To investigate the factors that influence the postoperative refractive error in long axial high myopic eyes, and to compare the accuracy of optimized Haigis and SRK/T formulas. Retrospective study. From May 2008 to December 2010, 137 high myopic eyes (with axial length (AL) greater than or equal to 26 mm) of 137 patients, who got cataract surgeries at Eye Hospital of Wenzhou Medical University, were enrolled for this study. The AL, corneal curvature (K), and anterior chamber depth (ACD) were measured by IOL-Master preoperatively. The intraocular lens (IOL) power was determined by optimized Haigis and SRK/T formulas, respectively. The preoperative and postoperative refractions were measured with phoropter. The target refraction after monofocal foldable IOL implantation was between -1.96 D to -7.39 D depending on the optimized Haigis formula. The mean absolute error (MAE) equals to the absolute difference between the target refraction and the 3 months postoperative actual refraction. One-way both groups, which the AL groups were as follow: 26 mm≤AL≤28 mm, 28 mmrefractive error and the parameters obtained preoperatively. (1) The IOL power is related to AL, K, ACD and preoperative spherical equivalent, the regression formulas is P=118.966-1.860AL-1.255K (F=472.86, P=0.00). (2) In AL groups: No statistical difference of MAE was found between each pair of groups by optimized Haigis (F=2.73, P=0.06). However, MAE difference were found between group 26 mm≤AL≤28 mm (-0.05±1.04) D and group 30 mm

  6. Prevalence of refractive errors in students with and without color vision deficiency

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    Hadi Ostadimoghaddam

    2014-01-01

    Full Text Available Purpose: To evaluate refractive errors in school age children with color vision deficiency (CVD and those with normal color vision (NCV in order to make a better understanding of the emmetropization process. Methods: A total of 4,400 primary school students aged 7-12 years were screened for color vision using Ishihara pseudoisochromatic color vision plate sets. Of these, 160 (3.6% students had CVD. A total of 400 age- and sex-matched students with NCV were selected as controls. Refractive status was evaluated using objective cyclorefraction. Results: The CVD group included 136 male (85% and 24 female (15% subjects with mean age of 10.1 ± 1.8 years. The NCV group comprised of 336 male (84% and 64 female (16% subjects with mean age of 10.5 ± 1.2 years. The prevalence of myopia (7.7% vs. 13.9%, P < 0.001 and hyperopia (41% vs. 57.4%, P = 0.03 was significantly lower in the CVD group. Furthermore, subjects with CVD subjects demonstrated a lower magnitude of refractive errors as compared to the CVD group (mean refractive error: +0.54 ± 0.19 D versus + 0.74 ± 1.12 D, P < 0.001. Conclusion: Although the lower prevalence of myopia in subjects with CVD group supports the role of longitudinal chromatic aberration in the development of refractive errors; the lower prevalence of hyperopia in this group is an opposing finding. Myopia is a multifactorial disorder and longitudinal chromatic aberration is not the only factor influencing the emmetropization process.

  7. Risk factors for refractive errors in primary school children (6-12 years old) in Nakhon Pathom Province.

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    Yingyong, Penpimol

    2010-11-01

    Refractive error is one of the leading causes of visual impairment in children. An analysis of risk factors for refractive error is required to reduce and prevent this common eye disease. To identify the risk factors associated with refractive errors in primary school children (6-12 year old) in Nakhon Pathom province. A population-based cross-sectional analytic study was conducted between October 2008 and September 2009 in Nakhon Pathom. Refractive error, parental refractive status, and hours per week of near activities (studying, reading books, watching television, playing with video games, or working on the computer) were assessed in 377 children who participated in this study. The most common type of refractive error in primary school children was myopia. Myopic children were more likely to have parents with myopia. Children with myopia spend more time at near activities. The multivariate odds ratio (95% confidence interval)for two myopic parents was 6.37 (2.26-17.78) and for each diopter-hour per week of near work was 1.019 (1.005-1.033). Multivariate logistic regression models show no confounding effects between parental myopia and near work suggesting that each factor has an independent association with myopia. Statistical analysis by logistic regression revealed that family history of refractive error and hours of near-work were significantly associated with refractive error in primary school children.

  8. PREVALENCE OF UNCORRECTED REFRACTIVE ERRORS IN ADULTS AGED 30 YEARS AND ABOVE IN A RURAL POPULATION IN PAKISTAN.

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    Abdullah, Ayesha S; Jadoon, Milhammad Zahid; Akram, Mohammad; Awan, Zahid Hussain; Azam, Mohammad; Safdar, Mohammad; Nigar, Mohammad

    2015-01-01

    Uncorrected refractive errors are a leading cause of visual disability globally. This population-based study was done to estimate the prevalence of uncorrected refractive errors in adults aged 30 years and above of village Pawakah, Khyber Pakhtunkhwa (KPK), Pakistan. It was a cross-sectional survey in which 1000 individuals were included randomly. All the individuals were screened for uncorrected refractive errors and those whose visual acuity (VA) was found to be less than 6/6 were refracted. In whom refraction was found to be unsatisfactory (i.e., a best corrected visual acuity of prevalence of uncorrected refractive errors was found to be 23.97% among males and 20% among females. The prevalence of visually disabling refractive errors was 6.89% in males and 5.71% in females. The prevalence was seen to increase with age, with maximum prevalence in 51-60 years age group. Hypermetropia (10.14%) was found to be the commonest refractive error followed by Myopia (6.00%) and Astigmatism (5.6%). The prevalence of Presbyopia was 57.5% (60.45% in males and 55.23% in females). Poor affordability was the commonest barrier to the use of spectacles, followed by unawareness. Cataract was the commonest reason for impaired vision after refractive correction. The prevalence of blindness was 1.96% (1.53% in males and 2.28% in females) in this community with cataract as the commonest cause. Despite being the most easily avoidable cause of subnormal vision uncorrected refractive errors still account for a major proportion of the burden of decreased vision in this area. Effective measures for the screening and affordable correction of uncorrected refractive errors need to be incorpora'ted into the health care delivery system.

  9. Prevalence of uncorrected refractive errors in adults aged 30 years and above in a rural population in Pakistan

    International Nuclear Information System (INIS)

    Abdullah, A.S.; Azam, M.; Nigar, M.

    2015-01-01

    Uncorrected refractive errors are a leading cause of visual disability globally. This population-based study was done to estimate the prevalence of uncorrected refractive errors in adults aged 30 years and above of village Pawakah, Khyber Pakhtunkhwa (KPK), Pakistan. Methods: It was a cross-sectional survey in which 1000 individuals were included randomly. All the individuals were screened for uncorrected refractive errors and those whose visual acuity (VA) was found to be less than 6/6 were refracted. In whom refraction was found to be unsatisfactory (i.e., a best corrected visual acuity of <6/6) further examination was done to establish the cause for the subnormal vision. Results: A total of 917 subjects participated in the survey (response rate 92%). The prevalence of uncorrected refractive errors was found to be 23.97% among males and 20% among females. The prevalence of visually disabling refractive errors was 6.89% in males and 5.71% in females. The prevalence was seen to increase with age, with maximum prevalence in 51-60 years age group. Hypermetropia (10.14%) was found to be the commonest refractive error followed by Myopia (6.00%) and Astigmatism (5.6%). The prevalence of Presbyopia was 57.5% (60.45% in males and 55.23% in females). Poor affordability was the commonest barrier to the use of spectacles, followed by unawareness. Cataract was the commonest reason for impaired vision after refractive correction. The prevalence of blindness was 1.96% (1.53% in males and 2.28% in females) in this community with cataract as the commonest cause. Conclusions: Despite being the most easily avoidable cause of subnormal vision uncorrected refractive errors still account for a major proportion of the burden of decreased vision in this area. Effective measures for the screening and affordable correction of uncorrected refractive errors need to be incorporated into the health care delivery system. (author)

  10. Analysis of aggregate surgically induced refractive change, prediction error, and intraocular astigmatism.

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    Holladay, J T; Moran, J R; Kezirian, G M

    2001-01-01

    To demonstrate analytical methods for evaluating the results of keratorefractive surgical procedures and emphasize the importance of intraocular astigmatism. University of Texas Medical School, Houston, Texas, USA. A standard data set, provided by an editor of this journal, comprising the preoperative and postoperative keratometric and refractive measurements of 100 eyes that had keratorefractive surgery was evaluated by 2 methods, vector and spheroequivalent (SEQ) analysis. The individual and aggregate surgically induced refractive changes (SIRCs) and prediction errors were determined from the refractive and keratometric measurements using both methods and then compared. The refraction vertex distance, keratometric index of refraction, and corneal asphericity were used to make the results calculated from refractive data directly comparable to those derived from keratometric data. Doubled-angle and equivalency plots as well as frequency and cumulative histograms were used to display the data. Standard descriptive statistics were used to determine the mean and standard deviation of the aggregate induced astigmatism after converting the polar values (cylinder and axis) to Cartesian (x and y) values. The preoperative SEQ refractive errors were undercorrected by at least 0.25 diopter (D) in most cases (78%). Six percent were corrected within +/- 0.24 D, and 16% were overcorrected by at least 0.25 D SEQ. The mean SEQ was -6.68 D +/- 2.49 (SD) before and -0.61 +/- 0.82 D after surgery, reflecting a SIRC SEQ of -6.07 +/- 2.40 D. The defocus equivalent (DEQ) was 7.41 +/- 2.53 D before and 0.96 +/- 0.74 D after surgery; for a nominal 3.0 mm pupil, this corresponded to an estimated improvement in uncorrected visual acuity (UCVA) from worse than 20/200 to better than 20/25, respectively. The predictability of the treatment decreased as the attempted refractive correction increased. The average magnitude of the refractive astigmatism was 1.46 +/- 0.61 D before and 0.40 +/- 0

  11. Rapid assessment of refractive error in the eThekwini Municipality of KwaZulu-Natal, Durban, South Africa.

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    Naidoo, Kovin S; Chinanayi, Farai S; Ramson, Prasidh; Mashige, Khathutshelo P

    2016-07-01

    Population-based studies involving refractive error in South Africa are few because they are expensive to conduct and require a high level of expertise. Rapid assessment of refractive error (RARE) is a relatively less resource-intensive method designed to assess the magnitude of uncorrected refractive error (URE), spectacle coverage and barriers to access of services. This information is useful for designing and implementing programs as well as for policy development. The purpose of this study was to determine the prevalence of uncorrected refractive error and spectacle coverage and to explore the barriers to uptake of refractive services in persons 15 to 35 years old in the eThekwini municipality, Durban, South Africa. A cross-sectional epidemiological study was conducted using the RARE protocol. A total of 1,543 participants were enumerated and 1,516 were examined. Uncorrected refractive error was defined as presenting visual acuity less than 6/12 that could be corrected to 6/12 or better using a pinhole. Spectacle coverage was defined as the proportion of need that was already met with spectacle correction. The prevalence of age and sex adjusted URE was 1.5% (95 per cent CI: 0.7 -2.3). Odds for uncorrected refractive error in women were 0.5 (95 per cent CI: 0.3-0.9) lower compared to men. There was a statistically significant association between uncorrected refractive error and respondents 15 to 24 years old (p prevalence of spectacle use among participants was 3.8 per cent. The low prevalence of uncorrected refractive error found in this study agrees with previous studies that indicate that despite uncorrected refractive error being the most common cause of visual impairment and the second most common cause of blindness worldwide, its prevalence is relatively low in South Africans. © 2016 Optometry Australia.

  12. Short-duration transient visual evoked potential for objective measurement of refractive errors.

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    Anand, Aashish; De Moraes, Carlos Gustavo V; Teng, Christopher C; Liebmann, Jeffrey M; Ritch, Robert; Tello, Celso

    2011-12-01

    This study examined effects of uncorrected refractive errors (RE) in a short-duration transient visual evoked potential (SD t-VEP) system and investigated their role for objective measurement of RE. Refractive errors were induced by means of trial lenses in 35 emmetropic subjects. A synchronized single-channel EEG was recorded for emmetropia, and each simulated refractive state to generate 21 VEP responses for each subject. P100 amplitude (N75 trough to P100 peak) and latency were identified by an automated post-signal processing algorithm. Induced hypermetropia and myopia correlated strongly with both P100 amplitude and latency. To minimize the effect of baseline shift and waveform fluctuations, a VEP scoring system, based on software-derived P100 latency, amplitude and waveform quality, was used to estimate the RE. Using the VEP scores, a single VEP response had a high sensitivity and specificity for discerning emmetropia, small RE (<2 diopter) within a 2 diopter range and large RE (2-14 diopter) within a 4 diopter range. The VEP scoring system has a potential for objective screening of RE and for a more accurate 3-step objective refraction.

  13. The Association of Refractive Error with Glaucoma in a Multiethnic Population.

    Science.gov (United States)

    Shen, Ling; Melles, Ronald B; Metlapally, Ravikanth; Barcellos, Lisa; Schaefer, Catherine; Risch, Neil; Herrinton, Lisa J; Wildsoet, Christine; Jorgenson, Eric

    2016-01-01

    To evaluate the association between refractive error and the prevalence of glaucoma by race or ethnicity. Cross-sectional study. Kaiser Permanente Northern California Health Plan members with refractive error measured at 35 years of age or older between 2008 and 2014 and with no history of cataract surgery, refractive surgery, or a corneal disorder. We identified 34 040 members with glaucoma or ocular hypertension (OHTN; cases) and 403 398 members without glaucoma (controls). Glaucoma cases were classified as primary angle-closure glaucoma (PACG); 1 of the 4 forms of open-angle glaucoma: primary open-angle glaucoma (POAG), normal-tension glaucoma (NTG), pigmentary glaucoma (PIGM), and pseudoexfoliation glaucoma (PEX); or OHTN. Refractive error, expressed as spherical equivalent (SE), was coded as a continuous trait and also as categories. Logistic regression analyses were used to estimate the association between refractive error and the prevalence of glaucoma overall and in specific racial or ethnic groups. The association between refractive error and glaucoma subtypes evaluated as odds ratios (ORs) with 95% confidence intervals (CIs). In controls, the mean SE was -0.59 diopters (D) (standard deviation, 2.62 D). Each 1-D reduction in SE was associated with a 22% decrease in the odds of PACG (OR, 0.78; 95% CI, 0.77-0.80) and with increases in the odds of open-angle glaucoma ranging from 1.23 (95% CI, 1.20-1.26) for PIGM, to 1.07 (95% CI, 1.03-1.11) for PEX, and to 1.05 (95% CI, 1.04-1.06) for OHTN. In addition, we observed a stronger association between myopia and POAG among non-Hispanic whites (OR, 1.12; 95% CI, 1.11-1.13) and NTG among Asians (OR, 1.17; 95% CI, 1.15-1.20) and non-Hispanic whites (OR, 1.19; 95% CI, 1.15-1.22). Myopia was associated with an increased prevalence of all forms of open-angle glaucoma and OHTN, whereas hyperopia was associated with a substantially increased prevalence of PACG. Although high myopia is a strong risk factor for glaucoma

  14. Visual symptoms associated with refractive errors among Thangka artists of Kathmandu valley.

    Science.gov (United States)

    Dhungel, Deepa; Shrestha, Gauri Shankar

    2017-12-21

    Prolong near work, especially among people with uncorrected refractive error is considered a potential source of visual symptoms. The present study aims to determine the visual symptoms and the association of those with refractive errors among Thangka artists. In a descriptive cross-sectional study, 242 (46.1%) participants of 525 thangka artists examined, with age ranged between 16 years to 39 years which comprised of 112 participants with significant refractive errors and 130 absolutely emmetropic participants, were enrolled from six Thangka painting schools. The visual symptoms were assessed using a structured questionnaire consisting of nine items and scoring from 0 to 6 consecutive scales. The eye examination included detailed anterior and posterior segment examination, objective and subjective refraction, and assessment of heterophoria, vergence and accommodation. Symptoms were presented in percentage and median. Variation in distribution of participants and symptoms was analysed using the Kruskal Wallis test for mean, and the correlation with the Pearson correlation coefficient. A significance level of 0.05 was applied for 95% confidence interval. The majority of participants (65.1%) among refractive error group (REG) were above the age of 30 years, with a male predominance (61.6%), compared to the participants in the normal cohort group (NCG), where majority of them (72.3%) were below 30 years of age (72.3%) and female (51.5%). Overall, the visual symptoms are high among Thangka artists. However, blurred vision (p = 0.003) and dry eye (p = 0.004) are higher among the REG than the NCG. Females have slightly higher symptoms than males. Most of the symptoms, such as sore/aching eye (p = 0.003), feeling dry (p = 0.005) and blurred vision (p = 0.02) are significantly associated with astigmatism. Thangka artists present with significant proportion of refractive error and visual symptoms, especially among females. The most commonly reported

  15. Refractive error in central India: the Central India Eye and Medical Study.

    Science.gov (United States)

    Nangia, Vinay; Jonas, Jost B; Sinha, Ajit; Matin, Arshia; Kulkarni, Maithili

    2010-04-01

    To evaluate the refractive error and its associations in the adult population of rural Central India. Population-based study. The Central India Eye and Medical Study is a population-based study performed in a markedly rural region in Central India. It included 4711 subjects (aged 30 years or older) of 5885 eligible subjects (response rate, 80.1%). The participants underwent a detailed ophthalmic and medical examination, including standardized questions on the socioeconomic background, lifestyle, and social relations. This study was focused on the refractive error, the prevalence of hyperopia and myopia, and its factors. Refractive error. After exclusion of pseudophakic or aphakic eyes, 9076 (96.3%) eyes of 4619 (98.0%) subjects (2472 females) were included into the study. The mean refractive error was -0.20+/-1.51 diopters (D). Myopia of more than -0.50 D, -1.0 D, more than -6.0 D, and more than -8 D occurred in 17.0+/-0.6%, 13.0+/-0.5%, 0.9+/-1.4%, and 0.4+/-0.1% of the subjects, respectively. Hyperopia of more than 0.50 D was detected in 18.0+/-0.6% of the subjects. Refractive error was associated significantly (i.e., became more hyperopic) with lower age (Prefractive power (Prefractive error was not significantly associated with the level of education (P = 0.56). High myopia (>-8 D) was associated significantly with male gender (P = 0.03) and lower best-corrected visual acuity (Prefractive error (Perror was 0.29+/-0.60 D and was associated significantly with higher age (Prefractive power (P<0.001). The rural population of Central India has not experienced a myopic shift as described for many urban populations at the Pacific Rim. Correspondingly, the relatively low level of education was not associated with myopia. Urbanization may be a major factor for myopization. Proprietary or commercial disclosure may be found after the references. Copyright 2010 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

  16. Prevalence of Refractive Errors among High School Students in Western Iran

    Science.gov (United States)

    Hashemi, Hassan; Rezvan, Farhad; Beiranvand, Asghar; Papi, Omid-Ali; Hoseini Yazdi, Hosein; Ostadimoghaddam, Hadi; Yekta, Abbas Ali; Norouzirad, Reza; Khabazkhoob, Mehdi

    2014-01-01

    Purpose To determine the prevalence of refractive errors among high school students. Methods In a cross-sectional study, we applied stratified cluster sampling on high school students of Aligoudarz, Western Iran. Examinations included visual acuity, non-cycloplegic refraction by autorefraction and fine tuning with retinoscopy. Myopia and hyperopia were defined as spherical equivalent of -0.5/+0.5 diopter (D) or worse, respectively; astigmatism was defined as cylindrical error >0.5 D and anisometropia as an interocular difference in spherical equivalent exceeding 1 D. Results Of 451 selected students, 438 participated in the study (response rate, 97.0%). Data from 434 subjects with mean age of 16±1.3 (range, 14 to 21) years including 212 (48.8%) male subjects was analyzed. The prevalence of myopia, hyperopia and astigmatism was 29.3% [95% confidence interval (CI), 25-33.6%], 21.7% (95%CI, 17.8-25.5%), and 20.7% (95%CI, 16.9-24.6%), respectively. The prevalence of myopia increased significantly with age [odds ratio (OR)=1.30, P=0.003] and was higher among boys (OR=3.10, Pprevalence of hyperopia was significantly higher in girls (OR=0.49, P=0.003). The prevalence of astigmatism was 25.9% in boys and 15.8% in girls (OR=2.13, P=0.002). The overall prevalence of high myopia and high hyperopia were 0.5% and 1.2%, respectively. The prevalence of with-the-rule, against-the-rule, and oblique astigmatism was 14.5%, 4.8% and 1.4%, respectively. Overall, 4.6% (95%CI, 2.6-6.6%) of subjects were anisometropic. Conclusion More than half of high school students in Aligoudarz had at least one type of refractive error. Compared to similar studies, the prevalence of refractive errors was high in this age group. PMID:25279126

  17. Association between childhood strabismus and refractive error in Chinese preschool children.

    Directory of Open Access Journals (Sweden)

    Hui Zhu

    Full Text Available To investigate the association between concomitant esotropia or concomitant exotropia and refractive error in preschool children.A population-based sample of 5831 children aged 3 to 6 years was selected from all kindergartens in a representative county (Yuhuatai District, Nanjing, Jiangsu Province of Nanjing, China. Clinical examinations including ocular alignment, ocular motility, visual acuity, optometry, stereopsis screening, slit lamp examination and fundus examination were performed by trained ophthalmologists and optometrists. Odd ratios (OR and 95% confidence intervals (95% CI were calculated to evaluate the association of refractive error with concomitant esotropia and concomitant exotropia.In multivariate logistic regression analysis, concomitant esotropia was associated independently with spherical equivalent anisometropia (OR, 3.15 for 0.50 to = 1.00 D of anisometropia and hyperopia. There was a severity-dependent association of hyperopia with the development of concomitant esotropia, with ORs increasing from 9.3 for 2.00 to = 5.00 D of hyperopia. Concomitant exotropia was associated with astigmatism (OR, 3.56 for 0.50 to 1.00 D of astigmatism, and 1.9 for <0.00 D of astigmatism, myopia (OR, 40.54 for -1.00 to <0.00 D of myopia, and 18.93 for <-1.00 D of myopia, and hyperopia (OR, 67.78 for 1.00 to <2.00 D of hyperopia, 23.13 for 2.00 to <3.00 D of hyperopia, 25.57 for 3.00 to <4.00 D of hyperopia, and 8.36 for 4.00 to <5.00 D of hyperopia.This study highlights the close associations between refractive error and the prevalence of concomitant esotropia and concomitant exotropia, which should be considered when managing childhood refractive error.

  18. Magnitude and determinants of refractive error among school children of two districts of Kathmandu, Nepal

    OpenAIRE

    Srijana Adhikari; Bhagwat P Nepal; Jeevan Kumar Shrestha; Rajiv Khandekar

    2013-01-01

    Purpose: The purpose of this study is to assess the magnitude and determinants of refractive error among school children of Lalitpur and Bhaktapur districts in Kathmandu Valley of Nepal. Materials and Methods: A descriptive study was carried out in 2003 in four schools; two in each district. A detailed ocular examination was conducted of all children attending these schools and that included visual acuity testing, slit lamp examination, fundus evaluation, retinoscopy, cycloplegic refracti...

  19. Strabismus, visual acuity, and uncorrected refractive error in portuguese children aged 6 to 11 years.

    Science.gov (United States)

    Lança, Carla; Serra, Helena; Prista, João

    2014-09-01

    Visual anomalies that affect school-age children represent an important public health problem. Data on the prevalence are lacking in Portugal but is needed for planning vision services. This study was conducted to determine the prevalence of strabismus, decreased visual acuity, and uncorrected refractive error in Portuguese children aged 6 to 11 years. A cross-sectional study was carried out on a sample of 672 school-age children (7.69±1.19 years). Children received an orthoptic assessment (visual acuity, ocular alignment, and ocular movements) and non-cycloplegic autorefraction. After orthoptic assessment, 13.8% of children were considered abnormal (n=93). Manifest strabismus was found in 4% of the children. Rates of esotropia (2.1%) were slightly higher than exotropia (1.8%). Strabismus rates were not statistically significant different per sex (p=0.681) and grade (p=0.228). Decreased visual acuity at distance was present in 11.3% of children. Visual acuity≤20/66 (0.5 logMAR) was found in 1.3% of the children. We also found that 10.3% of children had an uncorrected refractive error. Strabismus affects a small proportion of the Portuguese school-age children. Decreased visual acuity and uncorrected refractive error affected a significant proportion of school-age children. New policies need to be developed to address this public health problem.

  20. Amblyopia and refractive errors among school-aged children with low socioeconomic status in southeastern Turkey.

    Science.gov (United States)

    Caca, Ihsan; Cingu, Abdullah Kursat; Sahin, Alparslan; Ari, Seyhmus; Dursun, Mehmet Emin; Dag, Umut; Balsak, Selahattin; Alakus, Fuat; Yavuz, Abdullah; Palanci, Yilmaz

    2013-01-01

    To investigate the prevalence of refractive errors and other eye diseases, incidence and types of amblyopia in school-aged children, and their relation to gender, age, parental education, and socioeconomic factors. A total of 21,062 children 6 to 14 years old were screened. The examination included visual acuity measurements and ocular motility evaluation. Autorefraction under cycloplegia and examination of the external eye, anterior segment, media, and fundus were performed. There were 11,118 females and 9,944 males. The average age was 10.56 ± 3.59 years. When all of the children were evaluated, 3.2% had myopia and 5.9% had hyperopia. Astigmatism 0.50 D or greater was present in 14.3% of children. Myopia was associated with older age, female gender, and higher parental education. Hyperopia was inversely proportional with older age. Spectacles were needed in 4,476 (22.7%) children with refractive errors, and 10.6% of children were unaware of their spectacle needs. Amblyopia was detected in 2.6% of all children. The most common causes of amblyopia were anisometropia (1.2%) and strabismus (0.9%). Visual impairment is a common disorder in school-aged children. Eye health screening programs are beneficial in early detection and proper treatment of refractive errors. Copyright 2013, SLACK Incorporated.

  1. Avoidance of serious medical errors in refractive surgery using a custom preoperative checklist.

    Science.gov (United States)

    Robert, Marie-Claude; Choi, Catherine J; Shapiro, Fred E; Urman, Richard D; Melki, Samir

    2015-10-01

    To implement and measure the effect of a surgical safety checklist on the prevention of serious medical errors (never-events). Boston Eye Group, Boston, Massachusetts, USA. Retrospective cohort study. A safety checklist incorporating 28 sources of error was designed and implemented in December 2011 at the Boston Eye Group's refractive surgical center. Consecutive patients who had primary or enhancement laser vision correction (LVC) between July 2009 and February 2014 were included in this study. Before that date, a general checklist fashioned around the World Health Organization time-out procedure was used. The latter subjects were recruited as controls. The perioperative characteristics of both groups were retrospectively compared. The study comprised 2951 consecutive patients who had primary or enhancement LVC between July 2009 and February 2014; of these, 1417 patients (2744 eyes) had LVC after the implementation of a presurgical safety checklist. The general checklist fashioned around the World Health Organization time-out procedure was used for 1534 patients (2969 eyes). Both groups were comparable in patient age. The most common surgical procedures were laser in situ keratomileusis (78%) and laser-assisted subepithelial keratectomy with mitomycin-C (16%). Although there were 2 (0.07%) serious errors in the prechecklist cohort, none occurred following implementation of the safety checklist protocol (P = .23). The medical errors involved wrong refractive aim in 1 patient and wrong person-wrong procedure-wrong aim in another. Multiple potential sources of error exist in refractive surgery. The broad-scale implementation of a detailed presurgical safety checklist was helpful in minimizing and preventing serious errors (never-events) during LVC. Drs. Shapiro and Urman are members of the Institute for Safety in Office-Based Surgery, a nonprofit organization whose aims are to implement safety checklists for office-based surgery. No author has a financial or

  2. Comparison of Refractive Error Changes in Retinopathy of Prematurity Patients Treated with Diode and Red Lasers.

    Science.gov (United States)

    Roohipoor, Ramak; Karkhaneh, Reza; Riazi Esfahani, Mohammad; Alipour, Fateme; Haghighat, Mahtab; Ebrahimiadib, Nazanin; Zarei, Mohammad; Mehrdad, Ramin

    2016-01-01

    To compare refractive error changes in retinopathy of prematurity (ROP) patients treated with diode and red lasers. A randomized double-masked clinical trial was performed, and infants with threshold or prethreshold type 1 ROP were assigned to red or diode laser groups. Gestational age, birth weight, pretreatment cycloplegic refraction, time of treatment, disease stage, zone and disease severity were recorded. Patients received either red or diode laser treatment and were regularly followed up for retina assessment and refraction. The information at month 12 of corrected age was considered for comparison. One hundred and fifty eyes of 75 infants were enrolled in the study. Seventy-four eyes received diode and 76 red laser therapy. The mean gestational age and birth weight of the infants were 28.6 ± 3.2 weeks and 1,441 ± 491 g, respectively. The mean baseline refractive error was +2.3 ± 1.7 dpt. Posttreatment refraction showed a significant myopic shift (mean 2.6 ± 2.0 dpt) with significant difference between the two groups (p diode laser treatment (mean 6.00 dpt) and a lesser shift among children with zone II and red laser treatment (mean 1.12 dpt). The linear regression model, using the generalized estimating equation method, showed that the type of laser used has a significant effect on myopic shift even after adjustment for other variables. Myopic shift in laser-treated ROP patients is related to the type of laser used and the involved zone. Red laser seems to cause less myopic shift than diode laser, and those with zone I involvement have a greater myopic shift than those with ROP in zone II. © 2016 S. Karger AG, Basel.

  3. Toric intraocular lens orientation and residual refractive astigmatism: an analysis

    Directory of Open Access Journals (Sweden)

    Potvin R

    2016-09-01

    Full Text Available Rick Potvin,1 Brent A Kramer,2 David R Hardten,3 John P Berdahl4 1Science in Vision, Akron, NY, 2University of Iowa Carver College of Medicine, Iowa City, IA, 3Minnesota Eye Consultants, Minnetonka, MN, 4Vance Thompson Vision, Sioux Falls, SD, USA Purpose: To analyze intraocular lens (IOL orientation data from an online toric back-calculator (astigmatismfix.com for determining if differences were apparent by lens type.Methods: A retrospective review of astigmatismfix.com toric back-calculations that included IOL identification and intended orientation axis.Results: Of 12,812 total validated calculation records, 8,229 included intended orientation and lens identification data. Of the latter, 5,674 calculations (69% involved lenses oriented 5° or more from their intended position. Using estimated toric lens usage data, the percentage of lenses with orientation ≥5° from intended was 0.89% overall, but the percentage varied significantly between specific toric lens brands (P<0.05. The percentage of back-calculations related to lenses that were not oriented as intended was also statistically significantly different by lens brand (P<0.05. When IOLs were misoriented, they were significantly more likely to be misoriented in a counterclockwise direction (P<0.05. This was found to be due to a bias toward counterclockwise orientation observed with one specific brand, a bias that was not observed with the other three brands analyzed here.Conclusion: The percentage of eyes with lens orientation ≥5° from intended in the Toric Results Analyzer data set was <1% of toric IOLs in general, with the relative percentage of Tecnis® Toric IOLs significantly higher than AcrySof® Toric IOLs. Both of these had higher rates than the Staar® Toric and Trulign® Toric lenses, with the availability of higher Tecnis and AcrySof cylinder powers a likely contributing factor. The AcrySof Toric IOL appears to be less likely than the Tecnis Toric IOL to cause residual

  4. Prevalence of amblyopia and patterns of refractive error in the amblyopic children of a tertiary eye care center of Nepal.

    Science.gov (United States)

    Sapkota, K; Pirouzian, A; Matta, N S

    2013-01-01

    Refractive error is a common cause of amblyopia. To determine prevalence of amblyopia and the pattern and the types of refractive error in children with amblyopia in a tertiary eye hospital of Nepal. A retrospective chart review of children diagnosed with amblyopia in the Nepal Eye Hospital (NEH) from July 2006 to June 2011 was conducted. Children of age 13+ or who had any ocular pathology were excluded. Cycloplegic refraction and an ophthalmological examination was performed for all children. The pattern of refractive error and the association between types of refractive error and types of amblyopia were determined. Amblyopia was found in 0.7 % (440) of 62,633 children examined in NEH during this period. All the amblyopic eyes of the subjects had refractive error. Fifty-six percent (248) of the patients were male and the mean age was 7.74 ± 2.97 years. Anisometropia was the most common cause of amblyopia (p less than 0.001). One third (29 %) of the subjects had bilateral amblyopia due to high ametropia. Forty percent of eyes had severe amblyopia with visual acuity of 20/120 or worse. About twothirds (59.2 %) of the eyes had astigmatism. The prevalence of amblyopia in the Nepal Eye Hospital is 0.7%. Anisometropia is the most common cause of amblyopia. Astigmatism is the most common types of refractive error in amblyopic eyes. © NEPjOPH.

  5. Five-Year Progression of Refractive Errors and Incidence of Myopia in School-Aged Children in Western China

    Directory of Open Access Journals (Sweden)

    Wen-Jun Zhou

    2016-07-01

    Full Text Available Background: To determine the change in refractive error and the incidence of myopia among school-aged children in the Yongchuan District of Chongqing City, Western China. Methods: A population-based cross-sectional survey was initially conducted in 2006 among 3070 children aged 6 to 15 years. A longitudinal follow-up study was then conducted 5 years later between November 2011 and March 2012. Refractive error was measured under cycloplegia with autorefraction. Age, sex, and baseline refractive error were evaluated as risk factors for progression of refractive error and incidence of myopia. Results: Longitudinal data were available for 1858 children (60.5%. The cumulative mean change in refractive error was −2.21 (standard deviation [SD], 1.87 diopters (D for the entire study population, with an annual progression of refraction in a myopic direction of −0.43 D. Myopic progression of refractive error was associated with younger age, female sex, and higher myopic or hyperopic refractive error at baseline. The cumulative incidence of myopia, defined as a spherical equivalent refractive error of −0.50 D or more, among initial emmetropes and hyperopes was 54.9% (95% confidence interval [CI], 45.2%–63.5%, with an annual incidence of 10.6% (95% CI, 8.7%–13.1%. Myopia was found more likely to happen in female and older children. Conclusions: In Western China, both myopic progression and incidence of myopia were higher than those of children from most other locations in China and from the European Caucasian population. Compared with a previous study in China, there was a relative increase in annual myopia progression and annual myopia incidence, a finding which is consistent with the increasing trend on prevalence of myopia in China.

  6. Five-Year Progression of Refractive Errors and Incidence of Myopia in School-Aged Children in Western China

    Science.gov (United States)

    Zhou, Wen-Jun; Zhang, Yong-Ye; Li, Hua; Wu, Yu-Fei; Xu, Ji; Lv, Sha; Li, Ge; Liu, Shi-Chun; Song, Sheng-Fang

    2016-01-01

    Background To determine the change in refractive error and the incidence of myopia among school-aged children in the Yongchuan District of Chongqing City, Western China. Methods A population-based cross-sectional survey was initially conducted in 2006 among 3070 children aged 6 to 15 years. A longitudinal follow-up study was then conducted 5 years later between November 2011 and March 2012. Refractive error was measured under cycloplegia with autorefraction. Age, sex, and baseline refractive error were evaluated as risk factors for progression of refractive error and incidence of myopia. Results Longitudinal data were available for 1858 children (60.5%). The cumulative mean change in refractive error was −2.21 (standard deviation [SD], 1.87) diopters (D) for the entire study population, with an annual progression of refraction in a myopic direction of −0.43 D. Myopic progression of refractive error was associated with younger age, female sex, and higher myopic or hyperopic refractive error at baseline. The cumulative incidence of myopia, defined as a spherical equivalent refractive error of −0.50 D or more, among initial emmetropes and hyperopes was 54.9% (95% confidence interval [CI], 45.2%–63.5%), with an annual incidence of 10.6% (95% CI, 8.7%–13.1%). Myopia was found more likely to happen in female and older children. Conclusions In Western China, both myopic progression and incidence of myopia were higher than those of children from most other locations in China and from the European Caucasian population. Compared with a previous study in China, there was a relative increase in annual myopia progression and annual myopia incidence, a finding which is consistent with the increasing trend on prevalence of myopia in China. PMID:26875599

  7. Five-Year Progression of Refractive Errors and Incidence of Myopia in School-Aged Children in Western China.

    Science.gov (United States)

    Zhou, Wen-Jun; Zhang, Yong-Ye; Li, Hua; Wu, Yu-Fei; Xu, Ji; Lv, Sha; Li, Ge; Liu, Shi-Chun; Song, Sheng-Fang

    2016-07-05

    To determine the change in refractive error and the incidence of myopia among school-aged children in the Yongchuan District of Chongqing City, Western China. A population-based cross-sectional survey was initially conducted in 2006 among 3070 children aged 6 to 15 years. A longitudinal follow-up study was then conducted 5 years later between November 2011 and March 2012. Refractive error was measured under cycloplegia with autorefraction. Age, sex, and baseline refractive error were evaluated as risk factors for progression of refractive error and incidence of myopia. Longitudinal data were available for 1858 children (60.5%). The cumulative mean change in refractive error was -2.21 (standard deviation [SD], 1.87) diopters (D) for the entire study population, with an annual progression of refraction in a myopic direction of -0.43 D. Myopic progression of refractive error was associated with younger age, female sex, and higher myopic or hyperopic refractive error at baseline. The cumulative incidence of myopia, defined as a spherical equivalent refractive error of -0.50 D or more, among initial emmetropes and hyperopes was 54.9% (95% confidence interval [CI], 45.2%-63.5%), with an annual incidence of 10.6% (95% CI, 8.7%-13.1%). Myopia was found more likely to happen in female and older children. In Western China, both myopic progression and incidence of myopia were higher than those of children from most other locations in China and from the European Caucasian population. Compared with a previous study in China, there was a relative increase in annual myopia progression and annual myopia incidence, a finding which is consistent with the increasing trend on prevalence of myopia in China.

  8. Uncorrected refractive error and associated factors among primary school children in Debre Markos District, Northwest Ethiopia.

    Science.gov (United States)

    Sewunet, Sintayehu Aweke; Aredo, Kassahun Ketema; Gedefew, Molla

    2014-07-29

    Uncorrected Refractive Error is one of the leading cause amblyopia that exposes children to poor school performance. It refrain them from productive working lives resulting in severe economic and social loses in their latter adulthood lives. The objective of the study was to assess the prevalence of uncorrected refractive error and its associated factors among school children in Debre Markos District. A cross section study design was employed. Four hundred thirty two students were randomly selected using a multistage stratified sampling technique. The data were collected by trained ophthalmic nurses through interview, structured questionnaires and physical examinations. Snellens visual acuity measurement chart was used to identify the visual acuity of students. Students with visual acuity less than 6/12 had undergone further examination using auto refractor and cross-checked using spherical and cylindrical lenses. The data were entered into epi data statistical software version 3.1 and analyzed by SPSS version 20. The statistical significance was set at α ≤ 0.05. Descriptive, bivariate and multivariate analyses were done using odds ratios with 95% confidence interval. Out of 432 students selected for the study, 420 (97.2%) were in the age group 7-15 years. The mean age was 12 ± 2.1SD. Overall prevalence of refractive error was 43 (10.2%). Myopia was found among the most dominant 5.47% followed by astigmatism 1.9% and hyperopia 1.4% in both sexes. Female sex (AOR: 3.96, 95% CI: 1.55-10.09), higher grade level (AOR: 4.82, 95% CI: 1.98-11.47) and using computers regularly (AOR: 4.53, 95% CI: 1.58-12.96) were significantly associated with refractive error. The burden of uncorrected refractive errors is high among primary schools children. Myopia was common in both sexes. The potential risk factors were sex, regular use of computers and higher grade level of students. Hence, school health programs should work on health information dissemination and eye health care

  9. Refractive error and visual impairment in school children in Northern Ireland.

    Science.gov (United States)

    O'Donoghue, L; McClelland, J F; Logan, N S; Rudnicka, A R; Owen, C G; Saunders, K J

    2010-09-01

    To describe the prevalence of refractive error (myopia and hyperopia) and visual impairment in a representative sample of white school children. The Northern Ireland Childhood Errors of Refraction study, a population-based cross-sectional study, examined 661 white 12-13-year-old and 392 white 6-7-year-old children between 2006 and 2008. Procedures included assessment of monocular logarithm of the minimum angle of resolution (logMAR), visual acuity (unaided and presenting) and binocular open-field cycloplegic (1% cyclopentolate) autorefraction. Myopia was defined as -0.50DS or more myopic spherical equivalent refraction (SER) in either eye, hyperopia as > or =+2.00DS SER in either eye if not previously classified as myopic. Visual impairment was defined as >0.30 logMAR units (equivalent to 6/12). Levels of myopia were 2.8% (95% CI 1.3% to 4.3%) in younger and 17.7% (95% CI 13.2% to 22.2%) in older children: corresponding levels of hyperopia were 26% (95% CI 20% to 33%) and 14.7% (95% CI 9.9% to 19.4%). The prevalence of presenting visual impairment in the better eye was 3.6% in 12-13-year-old children compared with 1.5% in 6-7-year-old children. Almost one in four children fails to bring their spectacles to school. This study is the first to provide robust population-based data on the prevalence of refractive error and visual impairment in Northern Irish school children. Strategies to improve compliance with spectacle wear are required.

  10. Distribution of Binocular Vision Anomalies and Refractive Errors in Iranian Children With Learning Disabilities

    Directory of Open Access Journals (Sweden)

    Yekta

    2015-11-01

    Full Text Available Background Visual problems in children contribute to learning disorders, which are one of the most influential factors in learning. Objectives The aim of the present study was to determine the prevalence of refractive and binocular vision errors in children with learning disorders. Patients and Methods In this cross-sectional study, 406 children with learning disorders with a mean age of 8.56 ± 2.4 years were evaluated. Examinations included the determination of refractive errors with an auto-refractometer and static retinoscopy, measurement of visual acuity with a Snellen chart, evaluation of ocular deviation, and measurement of stereopsis, amplitude of accommodation, and near point of convergence. Results Of the 406 participants, 319 (78.6% were emmetropic in the right eye, 14.5% had myopia, and 6.9% had hyperopia according to cycloplegic refraction. Astigmatism was detected in 75 (18.5% children. In our study, 89.9% of the children had no deviation, 1.0% had esophoria, and 6.4% had exophoria . In addition, 2.2% of the children had suppression. The near point of convergence ranged from 3 to 18 cm, with a mean of 10.12 ± 3.274 cm. Moreover, 98.5 and 98.0% of the participants achieved complete vision with the best correction in the right and left eye, respectively. The best corrected visual acuity in the right and left eye was achieved in 98.5 and 98.0% of the children, respectively. Conclusions The pattern of visual impairment in learning-impaired children is not much different from that in normal children; however, because these children may not be able to express themselves clearly, lack of correct diagnosis and appropriate treatment has resulted in a marked defect in recognizing visual disorders in these children. Therefore, gaining knowledge of the prevalence of refractive errors in children with learning disorders can be considered the first step in their treatment.

  11. Nine Loci for Ocular Axial Length Identified through Genome-wide Association Studies, Including Shared Loci with Refractive Error

    NARCIS (Netherlands)

    Cheng, Ching-Yu; Schache, Maria; Ikram, M. Kamran; Young, Terri L.; Guggenheim, Jeremy A.; Vitart, Veronique; Macgregor, Stuart; Verhoeven, Virginie J. M.; Barathi, Veluchamy A.; Liao, Jiemin; Hysi, Pirro G.; Bailey-Wilson, Joan E.; St Pourcain, Beate; Kemp, John P.; McMahon, George; Timpson, Nicholas J.; Evans, David M.; Montgomery, Grant W.; Mishra, Aniket; Wang, Ya Xing; Wang, Jie Jin; Rochtchina, Elena; Polasek, Ozren; Wright, Alan F.; Amin, Najaf; van Leeuwen, Elisabeth M.; Wilson, James F.; Pennell, Craig E.; van Duijn, Cornelia M.; de Jong, Paulus T. V. M.; Vingerling, Johannes R.; Zhou, Xin; Chen, Peng; Li, Ruoying; Tay, Wan-Ting; Zheng, Yingfeng; Chew, Merwyn; Burdon, Kathryn P.; Craig, Jamie E.; Iyengar, Sudha K.; Igo, Robert P.; Lass, Jonathan H.; Chew, Emily Y.; Haller, Toomas; Mihailov, Evelin; Metspalu, Andres; Wedenoja, Juho; Simpson, Claire L.; Wojciechowski, Robert; Höhn, René; Mirshahi, Alireza; Zeller, Tanja; Pfeiffer, Norbert; Lackner, Karl J.; Bettecken, Thomas; Meitinger, Thomas; Oexle, Konrad; Pirastu, Mario; Portas, Laura; Nag, Abhishek; Williams, Katie M.; Yonova-Doing, Ekaterina; Klein, Ronald; Klein, Barbara E.; Hosseini, S. Mohsen; Paterson, Andrew D.; Makela, Kari-Matti; Lehtimaki, Terho; Kahonen, Mika; Raitakari, Olli; Yoshimura, Nagahisa; Matsuda, Fumihiko; Chen, Li Jia; Pang, Chi Pui; Yip, Shea Ping; Yap, Maurice K. H.; Meguro, Akira; Mizuki, Nobuhisa; Inoko, Hidetoshi; Foster, Paul J.; Zhao, Jing Hua; Vithana, Eranga; Tai, E.-Shyong; Fan, Qiao; Xu, Liang; Campbell, Harry; Fleck, Brian; Rudan, Igor; Aung, Tin; Hofman, Albert; Uitterlinden, André G.; Bencic, Goran; Khor, Chiea-Chuen; Forward, Hannah; Pärssinen, Olavi; Mitchell, Paul; Rivadeneira, Fernando; Hewitt, Alex W.; Williams, Cathy; Oostra, Ben A.; teo, Yik-Ying; Hammond, Christopher J.; Stambolian, Dwight; Mackey, David A.; Klaver, Caroline C. W.; Wong, Tien-Yin; Saw, Seang-Mei; Baird, Paul N.; Rahi, Jugnoo S.; Yamashiro, Kenji; Miyake, Masahiro; Delcourt, Cécile; Maubaret, Cecilia; Northstone, Kate; Ring, Susan M.; Davey-Smith, George; Fogarty, Rhys D.; Chew, Emily; Janmahasathian, Sarayut; Bailey Wilson, Joan E.; Lu, Yi; Jonas, Jost B.; Nangia, Vinay; Hayward, Caroline; Vatavuk, Zoran; Mohsen Hosseini, S.; Fondran, Jeremy R.; Feng, Sheng; Klaver, Caroline C.; Wegner, Aharon; Ho, Daniel W. H.; Murgia, Federico; Biino, Genevra; Ang, Wei; Kamran Ikram, M.; Deangelis, Margaret M.; Morrison, Margaux; Zhou, Xiangtian; Chen, Wei; D Paterson, Andrew; Lehtimäki, Terho; Mäkelä, Kari-Matti; Kähönen, Mika; Reinhart, William; Belin, Michael W.; Schultze, Robert L.; Morason, Todd; Sugar, Alan; Mian, Shahzad; Soong, Hunson Kaz; Colby, Kathryn; Jurkunas, Ula; Yee, Richard; Vital, Mark; Alfonso, Eduardo; Karp, Carol; Lee, Yunhee; Yoo, Sonia; Hammersmith, Kristin; Cohen, Elisabeth; Laibson, Peter; Rapuano, Christopher; Ayres, Brandon; Croasdale, Christopher; Caudill, James; Patel, Sanjay; Baratz, Keith; Bourne, William; Maguire, Leo; Sugar, Joel; Tu, Elmer; Djalilian, Ali; Mootha, Vinod; McCulley, James; Bowman, Wayne; Cavanaugh, H. Dwight; Verity, Steven; Verdier, David; Renucci, Ann; Oliva, Matt; Rotkis, Walter; Hardten, David R.; Fahmy, Ahmad; Brown, Marlene; Reeves, Sherman; Davis, Elizabeth A.; Lindstrom, Richard; Hauswirth, Scott; Hamilton, Stephen; Lee, W. Barry; Price, Francis; Price, Marianne; Kelly, Kathleen; Peters, Faye; Shaughnessy, Michael; Steinemann, Thomas; Dupps, B. J.; Meisler, David M.; Mifflin, Mark; Olson, Randal; Aldave, Anthony; Holland, Gary; Mondino, Bartly J.; Rosenwasser, George; Gorovoy, Mark; Dunn, Steven P.; Heidemann, David G.; Terry, Mark; Shamie, Neda; Rosenfeld, Steven I.; Suedekum, Brandon; Hwang, David; Stone, Donald; Chodosh, James; Galentine, Paul G.; Bardenstein, David; Goddard, Katrina; Chin, Hemin; Mannis, Mark; Varma, Rohit; Borecki, Ingrid; Donnelly, Peter; Barroso, Ines; Blackwell, Jenefer M.; Bramon, Elvira; Brown, Matthew A.; Casas, Juan P.; Corvin, Aiden; Deloukas, Panos; Duncanson, Audrey; Jankowski, Janusz; Markus, Hugh S.; Mathew, Christopher G.; Palmer, Colin N. A.; Plomin, Robert; Rautanen, Anna; Sawcer, Stephen J.; Trembath, Richard C.; Viswanathan, Ananth C.; Wood, Nicholas W.; Spencer, Chris C. A.; Band, Gavin; Bellenguez, Céline; Freeman, Colin; Hellenthal, Garrett; Giannoulatou, Eleni; Pirinen, Matti; Pearson, Richard; Strange, Amy; Su, Zhan; Vukcevic, Damjan; Langford, Cordelia; Hunt, Sarah E.; Edkins, Sarah; Gwilliam, Rhian; Blackburn, Hannah; Bumpstead, Suzannah J.; Dronov, Serge; Gillman, Matthew; Gray, Emma; Hammond, Naomi; Jayakumar, Alagurevathi; McCann, Owen T.; Liddle, Jennifer; Potter, Simon C.; Ravindrarajah, Radhi; Ricketts, Michelle; Waller, Matthew; Weston, Paul; Widaa, Sara; Whittaker, Pamela; Genuth, S.; Nathan, D. M.; Zinman, B.; Crofford, O.; Crandall, J.; Reid, M.; Brown-Friday, J.; Engel, S.; Sheindlin, J.; Martinez, H.; Shamoon, H.; Engel, H.; Phillips, M.; Gubitosi-Klug, R.; Mayer, L.; Pendegast, S.; Zegarra, H.; Miller, D.; Singerman, L.; Smith-Brewer, S.; Novak, M.; Quin, J.; Dahms, W.; Genuth, Saul; Palmert, M.; Brillon, D.; Lackaye, M. E.; Kiss, S.; Chan, R.; Reppucci, V.; Lee, T.; Heinemann, M.; Whitehouse, F.; Kruger, D.; Jones, J. K.; McLellan, M.; Carey, J. D.; Angus, E.; Thomas, A.; Galprin, A.; Bergenstal, R.; Johnson, M.; Spencer, M.; Morgan, K.; Etzwiler, D.; Kendall, D.; Aiello, Lloyd Paul; Golden, E.; Jacobson, A.; Beaser, R.; Ganda, O.; Hamdy, O.; Wolpert, H.; Sharuk, G.; Arrigg, P.; Schlossman, D.; Rosenzwieg, J.; Rand, L.; Larkin, M.; Ong, M.; Godine, J.; Cagliero, E.; Lou, P.; Folino, K.; Fritz, S.; Crowell, S.; Hansen, K.; Gauthier-Kelly, C.; Service, J.; Ziegler, G.; Luttrell, L.; Caulder, S.; Lopes-Virella, M.; Colwell, J.; Soule, J.; Fernandes, J.; Hermayer, K.; Kwon, S.; Brabham, M.; Blevins, A.; Parker, J.; Lee, D.; Patel, N.; Pittman, C.; Lindsey, P.; Bracey, M.; Lee, K.; Nutaitis, M.; Farr, A.; Elsing, S.; Thompson, T.; Selby, J.; Lyons, T.; Yacoub-Wasef, S.; Szpiech, M.; Wood, D.; Mayfield, R.; Molitch, M.; Schaefer, B.; Jampol, L.; Lyon, A.; Gill, M.; Strugula, Z.; Kaminski, L.; Mirza, R.; Simjanoski, E.; Ryan, D.; Kolterman, O.; Lorenzi, G.; Goldbaum, M.; Sivitz, W.; Bayless, M.; Counts, D.; Johnsonbaugh, S.; Hebdon, M.; Salemi, P.; Liss, R.; Donner, T.; Gordon, J.; Hemady, R.; Kowarski, A.; Ostrowski, D.; Steidl, S.; Jones, B.; Herman, W. H.; Martin, C. L.; Pop-Busui, R.; Sarma, A.; Albers, J.; Feldman, E.; Kim, K.; Elner, S.; Comer, G.; Gardner, T.; Hackel, R.; Prusak, R.; Goings, L.; Smith, A.; Gothrup, J.; Titus, P.; Lee, J.; Brandle, M.; Prosser, L.; Greene, D. A.; Stevens, M. J.; Vine, A. K.; Bantle, J.; Wimmergren, N.; Cochrane, A.; Olsen, T.; Steuer, E.; Rath, P.; Rogness, B.; Hainsworth, D.; Goldstein, D.; Hitt, S.; Giangiacomo, J.; Schade, D. S.; Canady, J. L.; Chapin, J. E.; Ketai C, L. H.; Braunstein, S.; Bourne, P. A.; Schwartz, S.; Brucker, A.; Maschak-Carey, B. J.; Baker, L.; Orchard, T.; Silvers, N.; Ryan, C.; Songer, T.; Doft, B.; Olson, S.; Bergren, R. L.; Lobes, L.; Paczan Rath, P.; Becker, D.; Rubinstein, D.; Conrad, P. W.; Yalamanchi, S.; Drash, A.; Morrison, A.; Bernal, M. L.; Vaccaro-Kish, J.; Malone, J.; Pavan, P. R.; Grove, N.; Iyer, M. N.; Burrows, A. F.; Tanaka, E. A.; Gstalder, R.; Dagogo-Jack, S.; Wigley, C.; Ricks, H.; Kitabchi, A.; Murphy, M. B.; Moser, S.; Meyer, D.; Iannacone, A.; Chaum, E.; Yoser, S.; Bryer-Ash, M.; Schussler, S.; Lambeth, H.; Raskin, P.; Strowig, S.; Barnie, A.; Devenyi, R.; Mandelcorn, M.; Brent, M.; Rogers, S.; Gordon, A.; Palmer, J.; Catton, S.; Brunzell, J.; Wessells, H.; de Boer, I. H.; Hokanson, J.; Purnell, J.; Ginsberg, J.; Kinyoun, J.; Deeb, S.; Weiss, M.; Meekins, G.; Distad, J.; van Ottingham, L.; Dupre, J.; Harth, J.; Nicolle, D.; Driscoll, M.; Mahon, J.; Canny, C.; May, M.; Lipps, J.; Agarwal, A.; Adkins, T.; Survant, L.; Pate, R. L.; Munn, G. E.; Lorenz, R.; Feman, S.; White, N.; Levandoski, L.; Boniuk, I.; Grand, G.; Thomas, M.; Joseph, D. D.; Blinder, K.; Shah, G.; Burgess, I.; Santiago, J.; Tamborlane, W.; Gatcomb, P.; Stoessel, K.; Taylor, K.; Goldstein, J.; Novella, S.; Mojibian, H.; Cornfeld, D.; Lima, J.; Bluemke, D.; Turkbey, E.; van der Geest, R. J.; Liu, C.; Malayeri, A.; Jain, A.; Miao, C.; Chahal, H.; Jarboe, R.; Maynard, J.; Gaston, P.; Trail, R.; Lachin, J.; Cleary, P.; Backlund, J.; Sun, W.; Braffett, B.; Klumpp, K.; Chan, K.; Diminick, L.; Rosenberg, D.; Petty, B.; Determan, A.; Kenny, D.; Rutledge, B.; Younes, Naji; Dews, L.; Hawkins, M.; Cowie, C.; Fradkin, J.; Siebert, C.; Eastman, R.; Danis, R.; Gangaputra, S.; Neill, S.; Davis, M.; Hubbard, L.; Wabers, H.; Burger, M.; Dingledine, J.; Gama, V.; Sussman, R.; Steffes, M.; Bucksa, J.; Nowicki, M.; Chavers, B.; O'Leary, D.; Polak, J.; Harrington, A.; Funk, L.; Crow, R.; Gloeb, B.; Thomas, S.; O'Donnell, C.; Soliman, E.; Zhang, Z. M.; Prineas, R.; Campbell, C.; Sandstrom, D.; Williams, T.; Geckle, M.; Cupelli, E.; Thoma, F.; Burzuk, B.; Woodfill, T.; Low, P.; Sommer, C.; Nickander, K.; Budoff, M.; Detrano, R.; Wong, N.; Fox, M.; Kim, L.; Oudiz, R.; Weir, G.; Espeland, M.; Manolio, T.; Singer, D.; Stern, M.; Boulton, A. E.; Clark, C.; D'Agostino, R.; Garvey, W. T.; Lyons, T. J.; Jenkins, A.; Virella, G.; Jaffa, A.; Carter, Rickey; Lackland, D.; McGee, D.; Zheng, D.; Mayfield, R. K.; Boright, A.; Bull, S.; Sun, L.; Scherer, S.; Natarajan, R.; Miao, F.; Zhang, L.; Chen, Z.

    2013-01-01

    Refractive errors are common eye disorders of public health importance worldwide. Ocular axial length (AL) is the major determinant of refraction and thus of myopia and hyperopia. We conducted a meta-analysis of genome-wide association studies for AL, combining 12,531 Europeans and 8,216 Asians. We

  12. [Comparative study of refractive errors in simple congenital myogenic ptosis and control children].

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    Pérez-Iñigo, M A; González, I; Mayoral, F; Ferrer, C; Honrubia, F M

    2008-10-01

    To study refractive errors in children with relatively serious congenital myogenic ptosis and to carry out a comparative study in relation to control children in our population. We included 35 children with simple congenital myogenic ptosis, 27 of them had minor ptosis, 3 moderate ptosis and 5 serious ptosis. Thirty-five children were also in the control group. One eye of every subject was included, the worst eye in subjects of the ptosis group and an eye selected at random in control group subjects. A comparative study of refractive data in every group was carried out, using the Student's t-test, ANOVA and Chi square or Yates correction tests. We obtained significant differences between children with ptosis and controls in average spherical equivalent (3.08/1.49), in average absolute sphere (2.80/1.42) and in average absolute cylinder (0.81/0.31) (p5.99), and between the need for optical correction and the presence of ptosis (chi2=15.92>3.84). Children with simple congenital myogenic ptosis in our enviroment have greater refractive errors than control children. Ptosis children require optical correction more frequently than control. The more serious the ptosis, the more likelihood there is of having astigmatism.

  13. The prevalence rates of refractive errors among children, adolescents, and adults in Germany

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    Sandra Jobke

    2008-10-01

    Full Text Available Sandra Jobke1, Erich Kasten2, Christian Vorwerk31Institute of Medical Psychology, 3Department of Ophthalmology, Otto-von Guericke-University of Magdeburg, Magdeburg, Germany; 2Institute of Medical Psychology, University Hospital Schleswig-Holstein, Luebeck, GermanyPurpose: The prevalence rates of myopia vary between 5% in Australian Aborigines to 84% in Hong Kong and Taiwan, 30% in Norwegian adults, and 49.5% in Swedish schoolchildren. The aim of this study was to determine the prevalence of refractive errors in German children, adolescents, and adults.Methods: The parents (aged 24–65 years and their children (516 subjects aged 2–35 years were asked to fill out a questionnaire about their refractive error and spectacle use. Emmetropia was defined as refractive status between +0.25D and –0.25D. Myopia was characterized as ≤−0.5D and hyperopia as ≥+0.5D. All information concerning refractive error were controlled by asking their opticians.Results: The prevalence rates of myopia differed significantly between all investigated age groups: it was 0% in children aged 2–6 years, 5.5% in children aged 7–11 years, 21.0% in adolescents (aged 12–17 years and 41.3% in adults aged 18–35 years (Pearson’s Chi-square, p = 0.000. Furthermore, 9.8% of children aged 2–6 years were hyperopic, 6.4% of children aged 7–11 years, 3.7% of adolescents, and 2.9% of adults (p = 0.380. The prevalence of myopia in females (23.6% was significantly higher than in males (14.6%, p = 0.018. The difference between the self-reported and the refractive error reported by their opticians was very small and was not significant (p = 0.850.Conclusion: In Germany, the prevalence of myopia seems to be somewhat lower than in Asia and Europe. There are few comparable studies concerning the prevalence rates of hyperopia.Keywords: Germany, hyperopia, incidence, myopia, prevalence

  14. Refractive error and vision correction in a general sports-playing population.

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    Zeri, Fabrizio; Pitzalis, Sabrina; Di Vizio, Assunta; Ruffinatto, Tiziana; Egizi, Fabrizio; Di Russo, Francesco; Armstrong, Richard; Naroo, Shehzad A

    2018-03-01

    To evaluate, in an amateur sports-playing population, the prevalence of refractive error, the type of vision correction used during sport and attitudes toward different kinds of vision correction used in various types of sports. A questionnaire was used for people engaging in sport and data was collected from sport centres, gyms and universities that focused on the motor sciences. One thousand, five hundred and seventy-three questionnaires were collected (mean age 26.5 ± 12.9 years; 63.5 per cent male). Nearly all (93.8 per cent) subjects stated that their vision had been checked at least once. Fifty-three subjects (3.4 per cent) had undergone refractive surgery. Of the remainder who did not have refractive surgery (n = 1,519), 580 (38.2 per cent) reported a defect of vision, 474 (31.2 per cent) were myopic, 63 (4.1 per cent) hyperopic and 241 (15.9 per cent) astigmatic. Logistic regression analysis showed that the best predictors for myopia prevalence were gender (p prevalence of outdoor activity have lower prevalence of myopia. Contact lens penetration over the study sample was 18.7 per cent. Contact lenses were the favourite system of correction among people interviewed compared to spectacles and refractive surgery (p prevalence in the adult population. However, subjects engaging in outdoor sports had lower rates of myopia prevalence. Penetration of contact lens use in sport was four times higher than the overall adult population. Contact lenses were the preferred system of correction in sports compared to spectacles or refractive surgery, but this preference was affected by the type of sport practised and by the age and level of sports activity for which the preference was required. © 2017 Optometry Australia.

  15. A POPULATION BASED STUDY OF REFRACTIVE ERRORS IN CHILDREN AMONG AGE GROUP OF 7-15 YEARS

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    Dhanya

    2016-03-01

    Full Text Available INTRODUCTION Refractive error is the most common cause of visual impairment around the world and the second leading cause of treatable blindness. Very early detection and treatment of visual impairment in children results in a reduction in the number of school children with poor sight being uncorrected. AIM To study the prevalence of uncorrected refractive errors among children of 7-15 years of age group. MATERIALS AND METHODS A total of 958 children of age group 7-15 years were examined during a time period of 1 year from June 2014 to May 2015. The examination included visual acuity, slit lamp examination, auto refractometer, keratometry, A-Scan Biometry and fundoscopic examination. Patients were then taken to assess the refractive error under the cycloplegic effect of 1% homatropine by streak retinoscopy. Hyperopia was defined as spherical power of >+2.00 D, Myopia as -0.50 D. RESULTS Visual impairment (VA of 6/12 or worse in better eye was present in 8.14% of the children examined. The prevalence of myopia, hypermetropia and astigmatism was 4.70%, 1.24%, 2.2% respectively, Myopia was commonly seen in older age group children. CONCLUSION Refractive error was the main cause of visual impairment in children between 7-15 years. Myopia was the most common refractive error particularly in older children. Uncorrected refractive errors among children have a considerable impact on learning and their academic achievement. Diagnosis and correction of refractive error is the most effective form of eye care. As it is an easily treatable cause of visual impairment, effective strategies should be developed to eliminate refractive error in children.

  16. Generational difference of refractive error and risk factors in the Handan Offspring Myopia Study.

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    Lin, Zhong; Gao, Tie Ying; Vasudevan, Balamurali; Jhanji, Vishal; Ciuffreda, Kenneth J; Zhang, Peng; Li, Lei; Mao, Guang Yun; Wang, Ning Li; Liang, Yuan Bo

    2014-08-05

    To report the refractive error difference (RED) between parents and their children, and its risk factors, in a rural area of China. Children (6-17 years) and their parents (36.2 ± 4.1 years) from the Handan Offspring Myopia Study (HOMS) were enrolled. Cycloplegic autorefraction (cyclopentolate 1%, Topcon KR8800) of the children and noncycloplegic autorefraction of their parents were assessed. A detailed vision-based questionnaire was also completed. Refractive error difference was defined as the difference between the parental spherical equivalent (SE) and their children's SE. Generational myopic shift was defined as the estimated RED when a child would be 18 years old according to a prediction model. Three hundred fifty-six pairs of parents and 585 children were enrolled. The RED (median, quartiles) increased from -1.33 (-1.99, -0.98) diopters (D) in children aged 6 to 7 years to 0.81 (-0.16, 2.28) D in children aged 16 to 17 years. The children's SE was predicted to approach the parental SE at 14 years of age. Moreover, the children's estimated myopic shift would be 1.03 D. Multiple linear regression revealed that older children (β = 0.23 D/y, P children's refraction was estimated to be similar to the parental refraction at 14 years of age. Moreover, the generational myopic shift was estimated to be approximately 1 D at 18 years of age. These data suggest that the generational difference reflects the increasing prevalence of myopia in the younger generation, which is likely due to changes in environmental exposure. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

  17. Refractive errors in 3-6 year-old Chinese children: a very low prevalence of myopia?

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    Weizhong Lan

    Full Text Available PURPOSE: To examine the prevalence of refractive errors in children aged 3-6 years in China. METHODS: Children were recruited for a trial of a home-based amblyopia screening kit in Guangzhou preschools, during which cycloplegic refractions were measured in both eyes of 2480 children. Cycloplegic refraction (from 3 to 4 drops of 1% cyclopentolate to ensure abolition of the light reflex was measured by both autorefraction and retinoscopy. Refractive errors were defined as followed: myopia (at least -0.50 D in the worse eye, hyperopia (at least +2.00 D in the worse eye and astigmatism (at least 1.50 D in the worse eye. Different definitions, as specified in the text, were also used to facilitate comparison with other studies. RESULTS: The mean spherical equivalent refractive error was at least +1.22 D for all ages and both genders. The prevalence of myopia for any definition at any age was at most 2.5%, and lower in most cases. In contrast, the prevalence of hyperopia was generally over 20%, and declined slightly with age. The prevalence of astigmatism was between 6% and 11%. There was very little change in refractive error with age over this age range. CONCLUSIONS: Previous reports of less hyperopic mean spherical equivalent refractive error, and more myopia and less hyperopia in children of this age may be due to problems with achieving adequate cycloplegia in children with dark irises. Using up to 4 drops of 1% cyclopentolate may be necessary to accurately measure refractive error in paediatric studies of such children. Our results suggest that children from all ethnic groups may follow a similar pattern of early refractive development, with little myopia and a hyperopic mean spherical equivalent over +1.00 D up to the age of 5-6 years in most conditions.

  18. Refractive Errors in 3–6 Year-Old Chinese Children: A Very Low Prevalence of Myopia?

    Science.gov (United States)

    Lin, Lixia; Li, Zhen; Zeng, Junwen; Yang, Zhikuan; Morgan, Ian G.

    2013-01-01

    Purpose To examine the prevalence of refractive errors in children aged 3–6 years in China. Methods Children were recruited for a trial of a home-based amblyopia screening kit in Guangzhou preschools, during which cycloplegic refractions were measured in both eyes of 2480 children. Cycloplegic refraction (from 3 to 4 drops of 1% cyclopentolate to ensure abolition of the light reflex) was measured by both autorefraction and retinoscopy. Refractive errors were defined as followed: myopia (at least −0.50 D in the worse eye), hyperopia (at least +2.00 D in the worse eye) and astigmatism (at least 1.50 D in the worse eye). Different definitions, as specified in the text, were also used to facilitate comparison with other studies. Results The mean spherical equivalent refractive error was at least +1.22 D for all ages and both genders. The prevalence of myopia for any definition at any age was at most 2.5%, and lower in most cases. In contrast, the prevalence of hyperopia was generally over 20%, and declined slightly with age. The prevalence of astigmatism was between 6% and 11%. There was very little change in refractive error with age over this age range. Conclusions Previous reports of less hyperopic mean spherical equivalent refractive error, and more myopia and less hyperopia in children of this age may be due to problems with achieving adequate cycloplegia in children with dark irises. Using up to 4 drops of 1% cyclopentolate may be necessary to accurately measure refractive error in paediatric studies of such children. Our results suggest that children from all ethnic groups may follow a similar pattern of early refractive development, with little myopia and a hyperopic mean spherical equivalent over +1.00 D up to the age of 5–6 yearsin most conditions. PMID:24205064

  19. Population-based survey of refractive error among school-aged children in rural northern China: the Heilongjiang eye study.

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    Li, Zhijian; Xu, Keke; Wu, Shubin; Lv, Jia; Jin, Di; Song, Zhen; Wang, Zhongliang; Liu, Ping

    2014-01-01

    The prevalence of refractive error in the north of China is unknown. The study aimed to estimate the prevalence and associated factors of refractive error in school-aged children in a rural area of northern China. Cross-sectional study. The cluster random sampling method was used to select the sample. A total of 1700 subjects of 5 to 18 years of age were examined. All participants underwent ophthalmic evaluation. Refraction was performed under cycloplegia. Association of refractive errors with age, sex, and education was analysed. The main outcome measure was prevalence rates of refractive error among school-aged children. Of the 1700 responders, 1675 were eligible. The prevalence of uncorrected, presenting, and best-corrected visual acuity of 20/40 or worse in the better eye was 6.3%, 3.0% and 1.2%, respectively. The prevalence of myopia was 5.0% (84/1675, 95% CI, 4.8%-5.4%) and of hyperopia was 1.6% (27/1675, 95% CI, 1.0%-2.2%). Astigmatism was evident in 2.0% of the subjects. Myopia increased with increasing age, whereas hyperopia and astigmatism were associated with younger age. Myopia, hyperopia and astigmatism were more common in females. We also found that prevalence of refractive error were associated with education. Myopia and astigmatism were more common in those with higher degrees of education. This report has provided details of the refractive status in a rural school-aged population. Although the prevalence of refractive errors is lower in the population, the unmet need for spectacle correction remains a significant challenge for refractive eye-care services. © 2013 Royal Australian and New Zealand College of Ophthalmologists.

  20. Refractive errors in 3-6 year-old Chinese children: a very low prevalence of myopia?

    Science.gov (United States)

    Lan, Weizhong; Zhao, Feng; Lin, Lixia; Li, Zhen; Zeng, Junwen; Yang, Zhikuan; Morgan, Ian G

    2013-01-01

    To examine the prevalence of refractive errors in children aged 3-6 years in China. Children were recruited for a trial of a home-based amblyopia screening kit in Guangzhou preschools, during which cycloplegic refractions were measured in both eyes of 2480 children. Cycloplegic refraction (from 3 to 4 drops of 1% cyclopentolate to ensure abolition of the light reflex) was measured by both autorefraction and retinoscopy. Refractive errors were defined as followed: myopia (at least -0.50 D in the worse eye), hyperopia (at least +2.00 D in the worse eye) and astigmatism (at least 1.50 D in the worse eye). Different definitions, as specified in the text, were also used to facilitate comparison with other studies. The mean spherical equivalent refractive error was at least +1.22 D for all ages and both genders. The prevalence of myopia for any definition at any age was at most 2.5%, and lower in most cases. In contrast, the prevalence of hyperopia was generally over 20%, and declined slightly with age. The prevalence of astigmatism was between 6% and 11%. There was very little change in refractive error with age over this age range. Previous reports of less hyperopic mean spherical equivalent refractive error, and more myopia and less hyperopia in children of this age may be due to problems with achieving adequate cycloplegia in children with dark irises. Using up to 4 drops of 1% cyclopentolate may be necessary to accurately measure refractive error in paediatric studies of such children. Our results suggest that children from all ethnic groups may follow a similar pattern of early refractive development, with little myopia and a hyperopic mean spherical equivalent over +1.00 D up to the age of 5-6 years in most conditions.

  1. Profile of refractive errors in European Caucasian children with Autistic Spectrum Disorder; increased prevalence and magnitude of astigmatism.

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    Anketell, Pamela M; Saunders, Kathryn J; Gallagher, Stephen; Bailey, Clare; Little, Julie-Anne

    2016-07-01

    Autistic Spectrum Disorder (ASD) is a common neurodevelopmental disorder characterised by impairment of communication, social interaction and repetitive behaviours. Only a small number of studies have investigated fundamental clinical measures of vision including refractive error. The aim of this study was to describe the refractive profile of a population of children with ASD compared to typically developing (TD) children. Refractive error was assessed using the Shin-Nippon NVision-K 5001 open-field autorefractor following the instillation of cyclopentolate hydrochloride 1% eye drops. A total of 128 participants with ASD (mean age 10.9 ± 3.3 years) and 206 typically developing participants (11.5 ± 3.1 years) were recruited. There was no significant difference in median refractive error, either by spherical equivalent or most ametropic meridian between the ASD and TD groups (Spherical equivalent, Mann-Whitney U307 = 1.15, p = 0.25; Most Ametropic Meridian, U305 = 0.52, p = 0.60). Median refractive astigmatism was -0.50DC (range 0.00 to -3.50DC) for the ASD group and -0.50DC (Range 0.00 to -2.25DC) for the TD group. Magnitude and prevalence of refractive astigmatism (defined as astigmatism ≥1.00DC) was significantly greater in the ASD group compared to the typically developing group (ASD 26%, TD 8%, magnitude U305 = 3.86, p = 0.0001; prevalence (χ12=17.71 , p refractive profile of a population of European Caucasian children with ASD compared to a TD population of children. Unlike other neurodevelopmental conditions, there was no increased prevalence of spherical refractive errors in ASD but astigmatic errors were significantly greater in magnitude and prevalence. This highlights the need to examine refractive errors in this population. © 2016 The Authors Ophthalmic & Physiological Optics © 2016 The College of Optometrists.

  2. Prevalence of refractive error and visual impairment among rural school-age children of Goro District, Gurage Zone, Ethiopia.

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    Kedir, Jafer; Girma, Abonesh

    2014-10-01

    Refractive error is one of the major causes of blindness and visual impairment in children; but community based studies are scarce especially in rural parts of Ethiopia. So, this study aims to assess the prevalence of refractive error and its magnitude as a cause of visual impairment among school-age children of rural community. This community-based cross-sectional descriptive study was conducted from March 1 to April 30, 2009 in rural villages of Goro district of Gurage Zone, found south west of Addis Ababa, the capital of Ethiopia. A multistage cluster sampling method was used with simple random selection of representative villages in the district. Chi-Square and t-tests were used in the data analysis. A total of 570 school-age children (age 7-15) were evaluated, 54% boys and 46% girls. The prevalence of refractive error was 3.5% (myopia 2.6% and hyperopia 0.9%). Refractive error was the major cause of visual impairment accounting for 54% of all causes in the study group. No child was found wearing corrective spectacles during the study period. Refractive error was the commonest cause of visual impairment in children of the district, but no measures were taken to reduce the burden in the community. So, large scale community level screening for refractive error should be conducted and integrated with regular school eye screening programs. Effective strategies need to be devised to provide low cost corrective spectacles in the rural community.

  3. Relationship between ocular wavefront aberrations and refractive error in Chinese school children.

    Science.gov (United States)

    Li, Tao; Zhou, Xiaodong; Chen, Zhi; Zhou, Xingtao; Chu, Renyuan; Hoffman, Matthew R

    2012-07-01

    The relationship between ocular wavefront aberrations and refractive error in children's eyes remains controversial. The purpose of this study is to re-examine this relationship in Chinese school children under natural distance accommodation. Ocular wavefront aberrations were measured in 86 Chinese children with spherical equivalent refraction (SER) between +0.5 D and -6.0 D and astigmatism less than -1.00 D. Wavefront aberrations were calculated using an objective method based on the Hartmann-Shack principle. Refractive error was obtained using a phoropter after cycloplegia. Subjects were categorised into three groups based on the mean SER: emmetropia (SER from -0.50 D to +0.50 D), mild myopia (SER greater than -0.50 D to -3.00 D) and moderate myopia (SER greater than -3.00 D to -6.00 D). Of the 86 participants, 22 were emmetropic, 43 were mildly myopic and 21 were moderately myopic. The root mean square (RMS) values of higher-order aberrations, Zernike coefficients (third-, fourth- and fifth-order aberrations) and R(j) (the ratio of third-, fourth- or fifth-order aberrations to total higher-order aberrations) were compared across the three refractive groups. No significant correlations were found between the RMS values of total higher-order aberrations, third-order aberrations, fourth-order aberrations, fifth-order aberrations, spherical aberration or coma and SER. No significant differences in the RMS values of total higher-order aberrations or R(j) were observed among the groups. The difference in fifth-order aberrations was statistically significant among the groups (p = 0.022); no other differences in higher-order aberration were found. Aside from C (3,1), no other differences were observed for Zernike coefficients. Ocular wavefront aberrations are similar among Chinese school children with different refractive errors under natural accommodation for a distance target. There is no evidence that myopes have a different amount of ocular higher-order aberrations

  4. The status of refractive errors in elementary school children in South Jeolla Province, South Korea

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    Jang JU

    2015-07-01

    Full Text Available Jung Un Jang,1 Inn-Jee Park2 1Department of Optometry, Eulji University, Seongnam, 2Department of Optometry, Kaya University, Gimhae, South Korea Purpose: To assess the prevalence of refractive errors among elementary school children in South Jeolla Province of South Korea. Methods: The subjects were aged 8–13 years; a total of 1,079 elementary school children from Mokpo, South Jeolla Province, were included. In all participants, uncorrected visual acuity and objective and subjective refractions were determined using auto Ref-Keratometer and phoropter. A spherical equivalent of -0.50 diopter (D or worse was defined as myopia, +0.50 D or more was defined as hyperopia, and a cylinder refraction greater than 0.75 D was defined as astigmatism. Results: Out of 1,079 elementary school children, the prevalence of uncorrected, best-corrected, and corrected visual acuity with own spectacles of 20/40 or worse in the better eye was 26.1%, 0.4%, and 20.2%, respectively. The uncorrected visual acuity was 20/200 or worse in the better eye in 5.7% of school children, and 5.2% of them already wore corrective spectacles. The prevalence of myopia, hyperopia, and astigmatism was 46.5% (95% confidence interval [CI]: 43.56–49.5, 6.2% (95% CI: 4.92–7.81, and 9.4% (95% CI: 7.76–11.25, respectively. Conclusion: The present study reveals a considerably higher prevalence of refractive error among elementary school children in South Jeolla Province of South Korea, exceeding 50% of subjects. The prevalence of myopia in the school children in Korea is similar to many other countries including People’s Republic of China, Malaysia, and Hong Kong. This may indicate that genetics and educational influences, such as studying and learning, may play a role in the progression of myopia in Korean elementary school children. Keywords: refractive error, elementary school children, visual acuity, myopia, astigmatism

  5. Prevalence of refractive error among preschool children in an urban population: the Baltimore Pediatric Eye Disease Study.

    Science.gov (United States)

    Giordano, Lydia; Friedman, David S; Repka, Michael X; Katz, Joanne; Ibironke, Josephine; Hawes, Patricia; Tielsch, James M

    2009-04-01

    To determine the age-specific prevalence of refractive errors in white and African-American preschool children. The Baltimore Pediatric Eye Disease Study is a population-based evaluation of the prevalence of ocular disorders in children aged 6 to 71 months in Baltimore, Maryland. Among 4132 children identified, 3990 eligible children (97%) were enrolled and 2546 children (62%) were examined. Cycloplegic autorefraction was attempted in all children with the use of a Nikon Retinomax K-Plus 2 (Nikon Corporation, Tokyo, Japan). If a reliable autorefraction could not be obtained after 3 attempts, cycloplegic streak retinoscopy was performed. Mean spherical equivalent (SE) refractive error, astigmatism, and prevalence of higher refractive errors among African-American and white children. The mean SE of right eyes was +1.49 diopters (D) (standard deviation [SD] = 1.23) in white children and +0.71 D (SD = 1.35) in African-American children (mean difference of 0.78 D; 95% confidence interval [CI], 0.67-0.89). Mean SE refractive error did not decline with age in either group. The prevalence of myopia of 1.00 D or more in the eye with the lesser refractive error was 0.7% in white children and 5.5% in African-American children (relative risk [RR], 8.01; 95% CI, 3.70-17.35). The prevalence of hyperopia of +3 D or more in the eye with the lesser refractive error was 8.9% in white children and 4.4% in African-American children (RR, 0.49; 95% CI, 0.35-0.68). The prevalence of emmetropia (refractive errors are uncommon in this population of urban preschool children. There was no evidence for a myopic shift over this age range in this cross-sectional study. A small proportion of preschool children would likely benefit from refractive correction, but few have had this prescribed.

  6. Refractive optics to compensate x-ray mirror shape-errors

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    Laundy, David; Sawhney, Kawal; Dhamgaye, Vishal; Pape, Ian

    2017-08-01

    Elliptically profiled mirrors operating at glancing angle are frequently used at X-ray synchrotron sources to focus X-rays into sub-micrometer sized spots. Mirror figure error, defined as the height difference function between the actual mirror surface and the ideal elliptical profile, causes a perturbation of the X-ray wavefront for X- rays reflecting from the mirror. This perturbation, when propagated to the focal plane results in an increase in the size of the focused beam. At Diamond Light Source we are developing refractive optics that can be used to locally cancel out the wavefront distortion caused by figure error from nano-focusing elliptical mirrors. These optics could be used to correct existing optical components on synchrotron radiation beamlines in order to give focused X-ray beam sizes approaching the theoretical diffraction limit. We present our latest results showing measurement of the X-ray wavefront error after reflection from X-ray mirrors and the translation of the measured wavefront into a design for refractive optical elements for correction of the X-ray wavefront. We show measurement of the focused beam with and without the corrective optics inserted showing reduction in the size of the focus resulting from the correction to the wavefront.

  7. Refractive error and visual impairment in private school children in Ghana.

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    Kumah, Ben D; Ebri, Anne; Abdul-Kabir, Mohammed; Ahmed, Abdul-Sadik; Koomson, Nana Ya; Aikins, Samual; Aikins, Amos; Amedo, Angela; Lartey, Seth; Naidoo, Kovin

    2013-12-01

    To assess the prevalence of refractive error and visual impairment in private school children in Ghana. A random selection of geographically defined classes in clusters was used to identify a sample of school children aged 12 to 15 years in the Ashanti Region. Children in 60 clusters were enumerated and examined in classrooms. The examination included visual acuity, retinoscopy, autorefraction under cycloplegia, and examination of anterior segment, media, and fundus. For quality assurance, a random sample of children with reduced and normal vision were selected and re-examined independently. A total of 2454 children attending 53 private schools were enumerated, and of these, 2435 (99.2%) were examined. Prevalence of uncorrected, presenting, and best visual acuity of 20/40 or worse in the better eye was 3.7, 3.5, and 0.4%, respectively. Refractive error was the cause of reduced vision in 71.7% of 152 eyes, amblyopia in 9.9%, retinal disorders in 5.9%, and corneal opacity in 4.6%. Exterior and anterior segment abnormalities occurred in 43 (1.8%) children. Myopia (at least -0.50 D) in one or both eyes was present in 3.2% of children when measured with retinoscopy and in 3.4% measured with autorefraction. Myopia was not significantly associated with gender (P = 0.82). Hyperopia (+2.00 D or more) in at least one eye was present in 0.3% of children with retinoscopy and autorefraction. The prevalence of reduced vision in Ghanaian private school children due to uncorrected refractive error was low. However, the prevalence of amblyopia, retinal disorders, and corneal opacities indicate the need for early interventions.

  8. Genetically low vitamin D concentrations and myopic refractive error: a Mendelian randomization study.

    Science.gov (United States)

    Cuellar-Partida, Gabriel; Williams, Katie M; Yazar, Seyhan; Guggenheim, Jeremy A; Hewitt, Alex W; Williams, Cathy; Wang, Jie Jin; Kho, Pik-Fang; Saw, Seang Mei; Cheng, Ching-Yu; Wong, Tien Yin; Aung, Tin; Young, Terri L; Tideman, J Willem L; Jonas, Jost B; Mitchell, Paul; Wojciechowski, Robert; Stambolian, Dwight; Hysi, Pirro; Hammond, Christopher J; Mackey, David A; Lucas, Robyn M; MacGregor, Stuart

    2017-12-01

    Myopia prevalence has increased in the past 20 years, with many studies linking the increase to reduced time spent outdoors. A number of recent observational studies have shown an inverse association between vitamin D [25(OH)D] serum levels and myopia. However, in such studies it is difficult to separate the effects of time outdoors and vitamin D levels. In this work we use Mendelian randomization (MR) to assess if genetically determined 25(OH)D levels contribute to the degree of myopia. We performed MR using results from a meta-analysis of refractive error (RE) genome-wide association study (GWAS) that included 37 382 and 8 376 adult participants of European and Asian ancestry, respectively, published by the Consortium for Refractive Error And Myopia (CREAM). We used single nucleotide polymorphisms (SNPs) in the DHCR7, CYP2R1, GC and CYP24A1 genes with known effects on 25(OH)D concentration as instrumental variables (IV). We estimated the effect of 25(OH)D on myopia level using a Wald-type ratio estimator based on the effect estimates from the CREAM GWAS. Using the combined effect attributed to the four SNPs, the estimate for the effect of 25(OH)D on refractive error was -0.02 [95% confidence interval (CI) -0.09, 0.04] dioptres (D) per 10 nmol/l increase in 25(OH)D concentration in Caucasians and 0.01 (95% CI -0.17, 0.19) D per 10 nmol/l increase in Asians. The tight confidence intervals on our estimates suggest the true contribution of vitamin D levels to degree of myopia is very small and indistinguishable from zero. Previous findings from observational studies linking vitamin D levels to myopia were likely attributable to the effects of confounding by time spent outdoors. © The Author 2017; all rights reserved. Published by Oxford University Press on behalf of the International Epidemiological Association

  9. Prevalence of Refractive Errors among High School Students in Western Iran

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    Hassan Hashemi

    2014-01-01

    Full Text Available Purpose: To determine the prevalence of refractive errors among high school students. Methods: In a cross-sectional study, we applied stratified cluster sampling on high school students of Aligoudarz, Western Iran. Examinations included visual acuity, non-cycloplegic refraction by autorefraction and fine tuning with retinoscopy. Myopia and hyperopia were defined as spherical equivalent of -0.5/+0.5 diopter (D or worse, respectively; astigmatism was defined as cylindrical error >0.5 D and anisometropia as an interocular difference in spherical equivalent exceeding 1 D. Results: Of 451 selected students, 438 participated in the study (response rate, 97.0%. Data from 434 subjects with mean age of 16΁1.3 (range, 14 to 21 years including 212 (48.8% male subjects was analyzed. The prevalence of myopia, hyperopia and astigmatism was 29.3% [95% confidence interval (CI, 25-33.6%], 21.7% (95%CI, 17.8-25.5%, and 20.7% (95%CI, 16.9-24.6%, respectively. The prevalence of myopia increased significantly with age [odds ratio (OR=1.30, P=0.003] and was higher among boys (OR=3.10, P<0.001. The prevalence of hyperopia was significantly higher in girls (OR=0.49, P=0.003. The prevalence of astigmatism was 25.9% in boys and 15.8% in girls (OR=2.13, P=0.002. The overall prevalence of high myopia and high hyperopia were 0.5% and 1.2%, respectively. The prevalence of with-the-rule, against-the-rule, and oblique astigmatism was 14.5%, 4.8% and 1.4%, respectively. Overall, 4.6% (95%CI, 2.6-6.6% of subjects were anisometropic. Conclusion: More than half of high school students in Aligoudarz had at least one type of refractive error. Compared to similar studies, the prevalence of refractive errors was high in this age group.

  10. Prevalence of refractive error in malay primary school children in suburban area of Kota Bharu, Kelantan, Malaysia.

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    Hashim, Syaratul-Emma; Tan, Hui-Ken; Wan-Hazabbah, W H; Ibrahim, Mohtar

    2008-11-01

    Refractive error remains one of the primary causes of visual impairment in children worldwide, and the prevalence of refractive error varies widely. The objective of this study was to determine the prevalence of refractive error and study the possible associated factors inducing refractive error among primary school children of Malay ethnicity in the suburban area of Kota Bharu, Kelantan, Malaysia. A school-based cross-sectional study was performed from January to July 2006 by random selection on Standard 1 to Standard 6 students of 10 primary schools in the Kota Bharu district. Visual acuity assessment was measured using logMAR ETDRS chart. Positive predictive value of uncorrected visual acuity equal or worse than 20/40, was used as a cut-off point for further evaluation by automated refraction and retinoscopic refraction. A total of 840 students were enumerated but only 705 were examined. The prevalence of uncorrected visual impairment was seen in 54 (7.7%) children. The main cause of the uncorrected visual impairment was refractive error which contributed to 90.7% of the total, and with 7.0% prevalence for the studied population. Myopia is the most common type of refractive error among children aged 6 to 12 years with prevalence of 5.4%, followed by hyperopia at 1.0% and astigmatism at 0.6%. A significant positive correlation was noted between myopia development with increasing age (P prevalence of myopia compared with Malays in the metropolitan cities of Kuala Lumpur (9.2%) and Singapore (22.1%). The ethnicity-specific prevalence rate of myopia was the lowest among Malays in Kota Bharu, followed by Kuala Lumpur, and is the highest among Singaporean Malays. Better socio-economic factors could have contributed to higher myopia rates in the cities, since the genetic background of these ethnic Malays are similar.

  11. Refractive Error and the Risk of Age-Related Macular Degeneration in the South Korean Population.

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    Lin, Shuai-Chun; Singh, Kuldev; Chao, Daniel L; Lin, Shan C

    2016-01-01

    We investigated the association between refractive error and the prevalence of age-related macular degeneration (AMD) in a population-based study. This was a cross-sectional study. Right eyes were included from 14,067 participants aged 40 years and older with gradable fundus photographs and refraction data from the fourth and the fifth Korea National Health and Nutrition Examination Survey 2008 to 2011. Early and late AMD was graded based on the International Age-Related Maculopathy Epidemiological Study Group grading system. Autorefraction data were collected to calculate spherical equivalent refraction in diopters (D) and classified into 4 groups: hyperopia (≥1.0 D), emmetropia (-0.99 to 0.99 D), mild myopia (-1.0 to -2.99 D), and moderate to high myopia (≤-3.0 D). After adjustment for potential confounders, each diopter increase in spherical equivalent was associated with a 16% [odds ratio (OR), 1.16; 95% confidence interval (CI), 1.08-1.25] and 18% (OR, 1.18; 95% CI, 1.10-1.27) increased risk of any (early + late) and early AMD, respectively. Mild and moderate to high myopia were associated with lower odds of any and early AMD compared with hyperopia (any AMD: OR, 0.62; 95% CI, 0.4-0.95 for mild myopia; OR, 0.41; 95% CI, 0.21-0.81 for moderate to high myopia; early AMD: OR, 0.63; 95% CI, 0.4-0.99 for mild myopia; OR, 0.36; 95% CI, 0.16-0.77 for moderate to high myopia group). There was no association between refractive status and the likelihood of late AMD (P = 0.91). Myopia is associated with lower odds of any and early AMD, but not with late AMD in the South Korean population.

  12. Association between reading speed, cycloplegic refractive error, and oculomotor function in reading disabled children versus controls.

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    Quaid, Patrick; Simpson, Trefford

    2013-01-01

    Approximately one in ten students aged 6 to 16 in Ontario (Canada) school boards have an individual education plan (IEP) in place due to various learning disabilities, many of which are specific to reading difficulties. The relationship between reading (specifically objectively determined reading speed and eye movement data), refractive error, and binocular vision related clinical measurements remain elusive. One hundred patients were examined in this study (50 IEP and 50 controls, age range 6 to 16 years). IEP patients were referred by three local school boards, with controls being recruited from the routine clinic population (non-IEP patients in the same age group). A comprehensive eye examination was performed on all subjects, in addition to a full binocular vision work-up and cycloplegic refraction. In addition to the cycloplegic refractive error, the following binocular vision related data was also acquired: vergence facility, vergence amplitudes, accommodative facility, accommodative amplitudes, near point of convergence, stereopsis, and a standardized symptom scoring scale. Both the IEP and control groups were also examined using the Visagraph III system, which permits recording of the following reading parameters objectively: (i) reading speed, both raw values and values compared to grade normative data, and (ii) the number of eye movements made per 100 words read. Comprehension was assessed via a questionnaire administered at the end of the reading task, with each subject requiring 80% or greater comprehension. The IEP group had significantly greater hyperopia compared to the control group on cycloplegic examination. Vergence facility was significantly correlated to (i) reading speed, (ii) number of eye movements made when reading, and (iii) a standardized symptom scoring system. Vergence facility was also significantly reduced in the IEP group versus controls. Significant differences in several other binocular vision related scores were also found. This

  13. Prevalence of refractive errors in a multiethnic Asian population: the Singapore epidemiology of eye disease study.

    Science.gov (United States)

    Pan, Chen-Wei; Zheng, Ying-Feng; Anuar, Ainur Rahman; Chew, Merwyn; Gazzard, Gus; Aung, Tin; Cheng, Ching-Yu; Wong, Tien Y; Saw, Seang-Mei

    2013-04-09

    To determine the prevalence of refractive errors in a multiethnic Asian population aged over 40 years and to examine secular trends and racial differences. A total of 10,033 adults (3353 Chinese, 3400 Indians, and 3280 Malays) participated in this study. Refractive error was determined by subjective refraction. Ocular biometric parameters were determined by partial coherence interferometry. Myopia and high myopia were defined as spherical equivalent (SE) of less than -0.5 diopters (D) and -5.0 D, respectively. Hyperopia was defined as SE of more than 0.5 D. Astigmatism was defined as cylinders less than -0.5 D. The prevalence of myopia, high myopia, hyperopia and astigmatism in Singapore adults aged over 40 years was 38.9% (95% confidence interval [CI] 37.1, 40.6); 8.4% (95% CI 8.0, 8.9); 31.5% (95% 30.5, 32.5); and 58.8% (95% CI 57.8, 59.9), respectively. Compared with the Tanjong Pagar Survey 12 years ago, there was a significant increase in the prevalence of astigmatism and mean axial length (AL) in Chinese adults aged over 40 years in Singapore. Chinese were most likely to be affected by myopia, high myopia, astigmatism, and had the longest AL among the three racial groups. The prevalence of myopia in Singapore adults is lower compared with the younger "myopia" generation in Singapore. The prevalence of astigmatism and mean AL have been increasing significantly within the past 12 years in the Chinese population. Chinese adults had higher prevalence of myopia, high myopia, astigmatism, as well as the longer AL compared with non-Chinese adults in Singapore.

  14. Pharmacological therapies for cataract and refractive errors: landscaping niches of ocular drug patenting.

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    Mucke, Hermann Am; Mucke, Peter; Mucke, Eva

    2012-05-01

    We have used a focused and comprehensive ophthalmology patent database to characterize the international patenting landscape dedicated to the pharmacological treatment of cataract, corneal opacities and dystrophies, and complicated refractive errors. A total of 201 disclosures related to cataract or corneal clouding (published between 1982 and 2011), and 99 documents (published between 1991 and 2011) related to refractive or geometry errors were identified. Current applications for the treatment or prevention of primary cataract have ceased to address diabetic cataract specifically through the inhibition of glycation-specific mechanisms. The most innovative approaches for pharmacotherapy of the lens focus on phase separation inhibitors, modulators of the TGF-β pathway, and matrix metalloproteinase inhibition. Patenting for the prevention of secondary cataracts as a delayed complication of intraocular lens insertion follows similar routes. For keratoconus, progressive myopia and Avellino corneal dystrophy, the focus remains on efficiently stabilizing the corrected shape of the cornea in the course of orthokeratology treatments. We expect future patenting in the fields of our investigation to concentrate more heavily on molecular medicine, in close lockstep with biotechnology and genetic testing.

  15. Ocular biometry and determinants of refractive error in a founder population of European ancestry.

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    Hilkert, Sarah M; Parness-Yossifon, Reut; Mets-Halgrimson, Rebecca; Mets, Marilyn B

    2018-01-01

    The prevalence of myopia is increasing worldwide. Previous studies have found a positive association between myopia, education, and near activities, while others have noted a negative association with outdoor exposure. This study reports refractive error and biometry in a founder population of European ancestry, the Hutterites, and discusses risk factors contributing to myopia. Cross-sectional study, including complete eye exams with retinoscopy and biometry. 939 study participants, ages 6 to 89, were examined. Females were significantly more myopic than males (SE -0.87 ± 2.07 and -0.40 ± 1.49 in females and males, respectively, p refractive error among the Hutterites. As a genetically isolated population with a communal lifestyle, the Hutterites present a unique opportunity to study risk factors for myopia. Hutterite females are more myopic than males, a finding which has only been reported in a few other populations. Hutterite children complete compulsory education through the 8th grade, after which women and men assume gender-specific occupational tasks. Men often work outside on the farm, while women engage in more domestic activities inside. These occupational differences likely contribute to the increased myopia comparing females to males, and their uniform lifestyle reduces the impact of potential confounding factors, such as education and income. The Hutterites are more myopic than most other North American and European populations. Greater time spent doing near work and less time spent outdoors likely explain the increased myopia comparing females to males.

  16. Prevalence of uncorrected refractive errors among children aged 3-10 years in western Saudi Arabia

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    Nojood Hameed R. Alrahili

    2017-08-01

    Full Text Available Objectives: To determine the prevalence of uncorrected refractive errors (URE among children 3-10 years and to affirm the necessity of a national school-based visual screening program for school-aged children. Methods: This retrospective cross-sectional study was conducted in Medina, Saudi Arabia in 2015. Children were selected through a multistage stratified random sampling from 8 kindergarten and 8 primary schools. Those included were screened to diagnose UREs using a visual acuity chart and an auto refractometer according to American guidelines. The prevalence and types of UREs were estimated. Results: Of the 2121 children enumerated, 1893 were examined, yielding a response rate of 89.3%. The prevalence of UREs was 34.9% (95% CI = 32.8%-37.1%, with significant differences in different age groups. The prevalence of astigmatism (25.3% was higher compared to that of anisometropia (7.4%, hypermetropia (1.5%, and myopia (0.7%. Risk of uncorrected refractive error was positively associated with age, and this was noted in astigmatism, myopia, and anisometropia. In addition, the risk of hypermetropia was associated with boys and that of myopia was associated with girls. Conclusions: The prevalence of UREs, particularly astigmatism, was high among children aged 3-10 years in Medina, with significant age differences. Vision screening programs targeting kindergarten and primary schoolchildren are crucial to lessen the risk of preventable visual impairment due to UREs.

  17. Prevalence of Visual Impairment and Refractive Errors in Children of South Sinai, Egypt.

    Science.gov (United States)

    Yamamah, Gamal Abdel Naser; Talaat Abdel Alim, Ahmed Ahmed; Mostafa, Yehia Salah El Din; Ahmed, Rania Ahmed Abdel Salam; Mohammed, Asmaa Mahmoud; Mahmoud, Asmaa Mohammed

    2015-01-01

    To assess the prevalence and causes of visual impairment in children of South Sinai, and to evaluate outcomes of rehabilitation programs. Population-based, cross-sectional analysis of 2070 healthy school children screened for visual impairment from 2009 through 2010 in cities of South Sinai and their surrounding Bedouin settlements. Visual acuity (VA) was tested using Snellen charts followed by cycloplegic autorefractometry for cases with presenting VA ≤ 6/9. Appropriate eyeglasses were prescribed and VA re-evaluated. This study included 1047 boys and 1023 girls, mean age 10.7 ± 3.1 years. Visual impairment (uncorrected VA ≤ 6/9) was detected in 29.4% of children, while 2.0% had moderate-severe visual impairment (uncorrected VA ≤ 6/24). There were statistically significant differences in prevalence of visual impairment between the studied cities (p visual impairment was significantly higher among girls (p visual impairment. Only age was a reliable predictor of visual impairment (odds ratio 0.94, p visual impairment, 90.32% of which comprised refractive errors (mainly astigmatism) which were significantly corrected with eyeglasses. VA screening and correction of refractive errors are of the utmost importance for ensuring better visual outcomes and improved school performance.

  18. The quality of systematic reviews about interventions for refractive error can be improved: a review of systematic reviews.

    Science.gov (United States)

    Mayo-Wilson, Evan; Ng, Sueko Matsumura; Chuck, Roy S; Li, Tianjing

    2017-09-05

    Systematic reviews should inform American Academy of Ophthalmology (AAO) Preferred Practice Pattern® (PPP) guidelines. The quality of systematic reviews related to the forthcoming Preferred Practice Pattern® guideline (PPP) Refractive Errors & Refractive Surgery is unknown. We sought to identify reliable systematic reviews to assist the AAO Refractive Errors & Refractive Surgery PPP. Systematic reviews were eligible if they evaluated the effectiveness or safety of interventions included in the 2012 PPP Refractive Errors & Refractive Surgery. To identify potentially eligible systematic reviews, we searched the Cochrane Eyes and Vision United States Satellite database of systematic reviews. Two authors identified eligible reviews and abstracted information about the characteristics and quality of the reviews independently using the Systematic Review Data Repository. We classified systematic reviews as "reliable" when they (1) defined criteria for the selection of studies, (2) conducted comprehensive literature searches for eligible studies, (3) assessed the methodological quality (risk of bias) of the included studies, (4) used appropriate methods for meta-analyses (which we assessed only when meta-analyses were reported), (5) presented conclusions that were supported by the evidence provided in the review. We identified 124 systematic reviews related to refractive error; 39 met our eligibility criteria, of which we classified 11 to be reliable. Systematic reviews classified as unreliable did not define the criteria for selecting studies (5; 13%), did not assess methodological rigor (10; 26%), did not conduct comprehensive searches (17; 44%), or used inappropriate quantitative methods (3; 8%). The 11 reliable reviews were published between 2002 and 2016. They included 0 to 23 studies (median = 9) and analyzed 0 to 4696 participants (median = 666). Seven reliable reviews (64%) assessed surgical interventions. Most systematic reviews of interventions for

  19. Age-related association of refractive error with intraocular pressure in the Korea National Health and Nutrition Examination Survey.

    Science.gov (United States)

    Choi, Jin A; Han, Kyungdo; Park, Yong-Moon; Park, Chan Kee

    2014-01-01

    To investigate the distribution of intraocular pressure (IOP) and refractive errors according to age group in a representative sample of non-glaucomatous Korean adults. A total of 7,277 adults (≥ 19 years) who participated in the Korea National Health and Nutrition Examination Survey (KNHANES) from 2008 to 2011 underwent ophthalmic examination were divided into three groups according to age: the young- (19-39 years), middle- (40-59 years), and old- (≥ 60 years) age groups. Simple and multiple regression analyses between IOP and various parameters (including the refractive error) were conducted. The mean IOP of the total population was 14.0 ± 0.1 mmHg [young: 13.9 ± 0.1 mmHg; middle: 14.1 ± 0.1 mmHg; old: 13.8 ± 0.2 mmHg (P for trend = 0.085)]. Myopia and high myopia were more prevalent in the young- (70.8% and 16.1%, respectively), compared to the middle- (44.6% and 10.9%) and old- (8.9% and 2.2%) age groups. Univariate analysis in the total population showed that higher IOP was associated with myopic refractive error, the female gender, higher body mass index (BMI), diabetes, hypertension, and hypercholesterolemia (all Prefractive error, the female gender, higher BMI, hypercholesterolemia and diabetes (all Prefractive error was not significant (P = 0.828). In multiple linear regression analysis, similar significant relationships between the refractive error and IOP were found in the young- and middle-age groups (beta =  -0.08 and -0.12; P = 0.002 and refractive error was an independent predictor of higher IOP in non- glaucomatous eyes, and the association between refractive error and IOP differed according to age.

  20. Visual outcome after correcting the refractive error of large pupil patients with wavefront-guided ablation

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    Khalifa MA

    2012-12-01

    Full Text Available Mounir A Khalifa,1,2 Waleed A Allam,1,2 Mohamed S Shaheen2,31Ophthalmology Department, Tanta University Eye Hospital, Tanta, Egypt; 2Horus Vision Correction Center, Alexandria, Egypt; 3Ophthalmology Department, Alexandria University, Alexandria, EgyptPurpose: To investigate the efficacy and predictability of wavefront-guided laser in situ keratomileusis (LASIK treatments using the iris registration (IR technology for the correction of refractive errors in patients with large pupils.Setting: Horus Vision Correction Center, Alexandria, Egypt.Methods: Prospective noncomparative study including a total of 52 eyes of 30 consecutive laser refractive correction candidates with large mesopic pupil diameters and myopia or myopic astigmatism. Wavefront-guided LASIK was performed in all cases using the VISX STAR S4 IR excimer laser platform. Visual, refractive, aberrometric and mesopic contrast sensitivity (CS outcomes were evaluated during a 6-month follow-up.Results: Mean mesopic pupil diameter ranged from 8.0 mm to 9.4 mm. A significant improvement in uncorrected distance visual acuity (UCDVA (P < 0.01 was found postoperatively, which was consistent with a significant refractive correction (P < 0.01. No significant change was detected in corrected distance visual acuity (CDVA (P = 0.11. Efficacy index (the ratio of postoperative UCDVA to preoperative CDVA and safety index (the ratio of postoperative CDVA to preoperative CDVA were calculated. Mean efficacy and safety indices were 1.06 ± 0.33 and 1.05 ± 0.18, respectively, and 92.31% of eyes had a postoperative spherical equivalent within ±0.50 diopters (D. Manifest refractive spherical equivalent improved significantly (P < 0.05 from a preoperative level of −3.1 ± 1.6 D (range −6.6 to 0 D to −0.1 ± 0.2 D (range −1.3 to 0.1 D at 6 months postoperative. No significant changes were found in mesopic CS (P ≥ 0.08, except CS for three cycles/degree, which improved significantly (P = 0

  1. Prevalence of anisometropia and its association with refractive error and amblyopia in preschool children.

    Science.gov (United States)

    Afsari, Sonia; Rose, Kathryn A; Gole, Glen A; Philip, Krupa; Leone, Jody F; French, Amanda; Mitchell, Paul

    2013-09-01

    To determine the age and ethnicity-specific prevalence of anisometropia in Australian preschool-aged children and to assess in this population-based study the risk of anisometropia with increasing ametropia levels and risk of amblyopia with increasing anisometropia. A total 2090 children (aged 6-72 months) completed detailed eye examinations in the Sydney Paediatric Eye Disease Study, including cycloplegic refraction, and were included. Refraction was measured using a Canon RK-F1 autorefractor, streak retinoscopy and/or the Retinomax K-Plus 2 autorefractor. Anisometropia was defined by the spherical equivalent (SE) difference, and plus cylinder difference for any cylindrical axis between eyes. The overall prevalence of SE and cylindrical anisometropia ≥1.0 D were 2.7% and 3.0%, for the overall sample and in children of European-Caucasian ethnicity, 3.2%, 1.9%; East-Asian 1.7%, 5.2%; South-Asian 2.5%, 3.6%; Middle-Eastern ethnicities 2.2%, 3.3%, respectively. Anisometropia prevalence was lower or similar to that in the Baltimore Pediatric Eye Disease Study, Multi-Ethnic Pediatric Eye Disease Study and the Strabismus, Amblyopia and Refractive error in Singapore study. Risk (OR) of anisometropic amblyopia with ≥1.0 D of SE and cylindrical anisometropia was 12.4 (CI 4.0 to 38.4) and 6.5 (CI 2.3 to 18.7), respectively. We found an increasing risk of anisometropia with higher myopia ≥-1.0 D, OR 61.6 (CI 21.3 to 308), hyperopia > +2.0 D, OR 13.6 (CI 2.9 to 63.6) and astigmatism ≥1.5 D, OR 30.0 (CI 14.5 to 58.1). In this preschool-age population-based sample, anisometropia was uncommon with inter-ethnic differences in cylindrical anisometropia prevalence. We also quantified the rising risk of amblyopia with increasing SE and cylindrical anisometropia, and present the specific levels of refractive error and associated increasing risk of anisometropia.

  2. Prevalence of visual impairment and refractive errors among different ethnic groups in schoolchildren in Turpan, China.

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    Chin, Man Pan; Siong, Kar Ho; Chan, Ka Ho; Do, Chi Wai; Chan, Henry Ho Lung; Cheong, Allen Ming Yan

    2015-05-01

    There is currently limited information about ethnic differences in myopia prevalence within mainland China, especially in rural or semi-rural areas. We examined the prevalence of refractive errors, visual impairment and spectacle coverage in school children of varying ethnicity in Turpan, Xinjiang province. A community eye care service was provided for five schools. Presenting monocular distance and near visual acuity (VA), and ocular alignment were assessed. Retinoscopy and cycloplegic subjective refraction were performed for participants with presenting visual impairment (distance VA worse than 0.3 logMAR; Snellen 6/12 or 20/40) or abnormal binocular vision. Questionnaires administered prior to the eye examinations were used to collect information regarding personal lifestyle and parental myopia. A total of 646 out of 690 (94%) subjects aged four to 19 years (11.9 ± 2.6; mean ± S.D.) completed the eye examination. Three hundred and eighty-two (59%) of participants were of Uyghur ethnicity, followed by Han, 176 (27%) and Hui, 74 (12%). The mean age of Uyghur, Han and Hui students was 12.3 ± 2.7, 11.4 ± 2.6 and 11.4 ± 2.3 years respectively, in which the Uyghur students were significantly older than the Han and Hui students (F(3,631) = 5.58 p prevalence of presenting visual impairment was not significantly different among the ethnic groups (p = 0.26). After cycloplegic refraction, most subjects' VA (98%) improved to better than 0.3 logMAR (Snellen 6/12 or 20/40). The prevalence of "clinically-significant myopia" (≤-0.50 dioptres) was 27%, 18% and 13% in Han, Hui and Uyghur children, respectively (p prevalence of astigmatism (Uyghur 12%, Han 5%, Hui 4%). The overall spectacle coverage was 36%, while spectacle coverage among ethnic groups were similar (Han, 41%; Uyghur, 32%; Hui, 41%; χ(2) = 2.23, df = 2, p = 0.33). The prevalence of clinically significant myopia varied markedly with ethnicity in school children sampled from a semi-rural region of mainland

  3. Hyperopic refractive error and shorter axial length are associated with age-related macular degeneration: the Singapore Malay Eye Study.

    Science.gov (United States)

    Lavanya, Raghavan; Kawasaki, Ryo; Tay, Wan Ting; Cheung, Gemmy C M; Mitchell, Paul; Saw, Seang-Mei; Aung, Tin; Wong, Tien Y

    2010-12-01

    To describe the association between refractive errors, ocular biometry, and age-related macular degeneration (AMD) in an Asian Malay population in Singapore. A population-based study of 3280 Malay individuals aged 40 to 80 years was conducted in Singapore. Early- and late-AMD signs were graded from retinal photographs according to the Wisconsin grading system. Autorefraction, followed by subjective refraction, was performed to obtain spherical equivalent refraction (SER) in diopters, with emmetropia defined as SER -0.5 to +0.5 D, hyperopia as > +0.5 D, and myopia as education, height, and systolic blood pressure. Each diopter increase in hyperopic refraction and each millimeter decrease in axial length was associated with an 8% (OR, 1.08; CI, 1.01-1.16; P = 0.03) and 29% (OR, 1.29; CI, 1.06-1.57; P = 0.01) increased risk of early AMD, respectively. No significant association was noted of refractive error and ocular biometry with late AMD. Hyperopic refractive error and shorter axial length are associated with early AMD in Asian eyes.

  4. Global Vision Impairment and Blindness Due to Uncorrected Refractive Error, 1990-2010.

    Science.gov (United States)

    Naidoo, Kovin S; Leasher, Janet; Bourne, Rupert R; Flaxman, Seth R; Jonas, Jost B; Keeffe, Jill; Limburg, Hans; Pesudovs, Konrad; Price, Holly; White, Richard A; Wong, Tien Y; Taylor, Hugh R; Resnikoff, Serge

    2016-03-01

    The purpose of this systematic review was to estimate worldwide the number of people with moderate and severe visual impairment (MSVI; presenting visual acuity refractive error (URE), to estimate trends in prevalence from 1990 to 2010, and to analyze regional differences. The review focuses on uncorrected refractive error which is now the most common cause of avoidable visual impairment globally. : The systematic review of 14,908 relevant manuscripts from 1990 to 2010 using Medline, Embase, and WHOLIS yielded 243 high-quality, population-based cross-sectional studies which informed a meta-analysis of trends by region. The results showed that in 2010, 6.8 million (95% confidence interval [CI]: 4.7-8.8 million) people were blind (7.9% increase from 1990) and 101.2 million (95% CI: 87.88-125.5 million) vision impaired due to URE (15% increase since 1990), while the global population increased by 30% (1990-2010). The all-age age-standardized prevalence of URE blindness decreased 33% from 0.2% (95% CI: 0.1-0.2%) in 1990 to 0.1% (95% CI: 0.1-0.1%) in 2010, whereas the prevalence of URE MSVI decreased 25% from 2.1% (95% CI: 1.6-2.4%) in 1990 to 1.5% (95% CI: 1.3-1.9%) in 2010. In 2010, URE contributed 20.9% (95% CI: 15.2-25.9%) of all blindness and 52.9% (95% CI: 47.2-57.3%) of all MSVI worldwide. The contribution of URE to all MSVI ranged from 44.2 to 48.1% in all regions except in South Asia which was at 65.4% (95% CI: 62-72%). : We conclude that in 2010, uncorrected refractive error continues as the leading cause of vision impairment and the second leading cause of blindness worldwide, affecting a total of 108 million people or 1 in 90 persons.

  5. Refractive error and visual functions in children with special needs compared with the first grade school students in oman.

    Science.gov (United States)

    Vora, Urmi; Khandekar, Rajiv; Natrajan, Sarvanan; Al-Hadrami, Khalfan

    2010-10-01

    We evaluated the refractive status and visual function of children with special needs (other handicap) in 2010 and compared them with healthy 1(st) grade school students in Oman. This was a cohort study. Optometrists recorded vision using a logarithm of minimum angle of resolution (LogMAR) chart. Preferential looking method was used for testing 31 children. Cycloplegic refraction was performed on all children. Contrast sensitivity was tested using 2.5%, 10%, and 100% contrast charts. Ocular movement, alignment, and anterior segment were also assessed. A pediatrician reviewed the health records of all the children at the time of their enrollment in this study to determine if the child had been diagnosed with a systemic condition or syndromes. The visual functions were assessed by study investigators. We estimated the rates and the risk of different visual function defects in children with special needs. The prevalence of refractive error in 70 children (4.7 ± 0.8 years) with special needs (group 1) and 175 normal healthy first grade students (group 2) were 58.5% and 2.9%, respectively. The risk of refractive error was significantly higher in children with special needs [relative risk, 48.1 (95% confidence interval, 17.54-131.8)]. Hyperopia (>1.00 D), myopia (≥ 1.00D) and astigmatism (≥ ±1.00 D) were found in 18.6%, 24.3%, and 27.1%, respectively, in group 1. Six children in this group had defective near vision. Sixteen (80%) children with Down syndrome had refractive error. Seven (50%) children with developmental disorder showed decreased contrast sensitivity. Prevalence of uncorrected refractive error was much higher in children with special needs. Prevalence of strabismus, nystagmus, and reduced contrast sensitivity was also higher in children with special needs. Early vision screening, visual function assessment, correction of refractive error, and frequent follow-up are recommended.

  6. Exceptionally low prevalence of refractive error and visual impairment in schoolchildren from Lao People's Democratic Republic.

    Science.gov (United States)

    Casson, Robert J; Kahawita, Shyalle; Kong, Aimee; Muecke, James; Sisaleumsak, Siphetthavong; Visonnavong, Vithoune

    2012-10-01

    Vientiane Province is an urbanizing region in Southeast Asia. We aimed to determine the prevalence of refractive error and visual impairment in primary school-aged children in this region. Prospective, cross-sectional survey. A total of 2899 schoolchildren from Vientiane Province, Lao People's Democratic Republic (Lao PDR). Ten districts from Vientiane were randomly selected and 2 primary schools were randomly selected from each district. All children aged 6 to 11 years at selected schools were eligible to participate. The examination included visual acuity (VA) testing, cycloplegic retinoscopy with subjective refinement if indicated, ocular motility testing, and anterior segment and fundus examinations in visually impaired children. Cycloplegic refraction and VA. There was an estimated total of 3330 children who were eligible to participate, and data were recorded from 2899 (87%) of these children. Complete refractive data were available on 2842 children (85% of eligible population). The mean spherical equivalent (SE) in the right eyes was +0.60 diopter (D) (95% confidence interval [CI], 0.49-0.72), and the mean SE in the left eyes was +0.59 (95% CI, 0.50-0.68). The prevalence of hyperopia was 2.8% (95% CI, 1.9-3.7; 88 subjects), and the prevalence of myopia was 0.8% (95% CI, 0.3-1.4; 24 subjects). The majority of children (98%; 95% CI, 97.0-99.0) had normal unaided binocular VA (at least 20/32 in their better eye). The overall prevalence of any visual impairment (presenting VA prevalence in this population. Copyright © 2012 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

  7. Prevalence and predictors of refractive error and spectacle coverage in Nakuru, Kenya: a cross-sectional, population-based study.

    Science.gov (United States)

    Bastawrous, Andrew; Mathenge, Wanjiku; Foster, Allen; Kuper, Hannah

    2013-10-01

    A cross-sectional study was undertaken in Nakuru, Kenya to assess the prevalence of refractive error and the spectacle coverage in a population aged ≥50 years. Of the 5,010 subjects who were eligible, 4,414 underwent examination (response rate 88.1 %). LogMAR visual acuity was assessed in all participants and refractive error was measured in both eyes using a Topcon auto refractor RM8800. Detailed interviews were undertaken and ownership of spectacles was assessed. Refractive error was responsible for 51.7 % of overall visual impairment (VI), 85.3 % (n = 191) of subjects with mild VI, 42.7 % (n = 152) of subjects with moderate VI, 16.7 % (n = 3) of subjects with severe VI and no cases of blindness. Myopia was more common than hyperopia affecting 59.5 % of those with refractive error compared to 27.4 % for hyperopia. High myopia (+5.0 DS). Of those who needed distance spectacles (spectacle coverage), 25.5 % owned spectacles. In conclusion, the oldest, most poor and least educated are most likely to have no spectacles and they should be specifically targeted when refractive services are put in place.

  8. Main visual symptoms associated to refractive errors and spectacle need in a Brazilian population.

    Science.gov (United States)

    Schellini, Silvana; Ferraz, Fabio; Opromolla, Paula; Oliveira, Laryssa; Padovani, Carlos

    2016-01-01

    To determine the main visual symptoms in a Brazilian population sample, associated to refractive errors (REs) and spectacle need to suggest priorities in preventive programs. A cross-sectional study was conducted in nine counties of the southeast region of Brazil, using a systematic sampling of households, between March 2004 and July 2005. The population was defined as individuals aged between 1 and 96y, inhabitants of 3600 residences to be evaluated and 3012 households were included, corresponding to 8010 subjects considered for participation in the survey, of whom 7654 underwent ophthalmic examinations. The individuals were evaluated according their demographic data, eye complaints and eye examination including the RE and the need to prescribe spectacles according to age. Statistical analysis was performed using SPSS software package and descriptive analysis using 95% confidence intervals (PBrazilian population.

  9. Steps towards Smarter Solutions in Optometry and Ophthalmology?Inter-Device Agreement of Subjective Methods to Assess the Refractive Errors of the Eye

    OpenAIRE

    Ohlendorf, Arne; Leube, Alexander; Wahl, Siegfried

    2016-01-01

    Purpose: To investigate the inter-device agreement and mean differences between a newly developed digital phoropter and the two standard methods (trial frame and manual phoropter). Methods: Refractive errors of two groups of participants were measured by two examiners (examiner 1 (E1): 36 subjects; examiner 2 (E2): 38 subjects). Refractive errors were assessed using a trial frame, a manual phoropter and a digital phoropter. Inter-device agreement regarding the measurement of refractive errors...

  10. [Improvement of vision through perceptual learning in the case of refractive errors and presbyopia : A critical valuation].

    Science.gov (United States)

    Heinrich, S P

    2017-02-01

    The idea of compensating or even rectifying refractive errors and presbyopia with the help of vision training is not new. For most approaches, however, scientific evidence is insufficient. A currently promoted method is "perceptual learning", which is assumed to improve stimulus processing in the brain. The basic phenomena of perceptual learning have been demonstrated by a multitude of studies. Some of these specifically address the case of refractive errors and presbyopia. However, many open questions remain, in particular with respect to the transfer of practice effects to every-day vision. At present, the method should therefore be judged with caution.

  11. Feasibility of Residual Stress Nondestructive Estimation Using the Nonlinear Property of Critical Refraction Longitudinal Wave

    Directory of Open Access Journals (Sweden)

    Yu-Hua Zhang

    2017-01-01

    Full Text Available Residual stress has significant influence on the performance of mechanical components, and the nondestructive estimation of residual stress is always a difficult problem. This study applies the relative nonlinear coefficient of critical refraction longitudinal (LCR wave to nondestructively characterize the stress state of materials; the feasibility of residual stress estimation using the nonlinear property of LCR wave is verified. The nonlinear ultrasonic measurements based on LCR wave are conducted on components with known stress state to calculate the relative nonlinear coefficient. Experimental results indicate that the relative nonlinear coefficient monotonically increases with prestress and the increment of relative nonlinear coefficient is about 80%, while the wave velocity only decreases about 0.2%. The sensitivity of the relative nonlinear coefficient for stress is much higher than wave velocity. Furthermore, the dependence between the relative nonlinear coefficient and deformation state of components is found. The stress detection resolution based on the nonlinear property of LCR wave is 10 MPa, which has higher resolution than wave velocity. These results demonstrate that the nonlinear property of LCR wave is more suitable for stress characterization than wave velocity, and this quantitative information could be used for residual stress estimation.

  12. Prevalence of heterophoria and associations with refractive error, heterotropia and ethnicity in Australian school children.

    Science.gov (United States)

    Leone, Jody F; Cornell, Elaine; Morgan, Ian G; Mitchell, Paul; Kifley, Annette; Wang, Jie Jin; Rose, Kathryn A

    2010-05-01

    AIMS To establish the prevalence of heterophoria and its association with refractive error and ethnicity in a population-based study of Australian schoolchildren. METHODS The Sydney Myopia Study is a stratified, random cluster (school-based) sample of 4093 students (examined: 2003-2005). Two samples aged 6 (n=1692) and 12 years (n=2289) without heterotropia were included. Prevalent heterophoria was assessed using cover un-cover and prism bar alternate cover testing at 33 cm and 6 m distance fixation. Cycloplegic autorefraction (1% cyclopentolate) was performed. Significant refractive error was defined as or =+2.00SE. RESULTS Exophoria was highly prevalent at near fixation (age 6: 58.3%, age 12: 52.2%). Orthophoria predominated at distance fixation (age 6: 85.4%, age 12: 90.9%). Hyperopia was associated with esophoria at near (age 6: OR 1.7, 95% CI 1.1 to 2.8, age 12: OR 2.9, CI 1.1 to 2.8) and distance fixation (age 6: OR 9.7, CI 3.5 to 26, age 12: 9.6 OR, CI 4.2 to 22). Myopia was associated with exophoria at near (OR 2.1, CI 1.5 to 2.7) and distance fixation (OR 3.1, CI 2.1 to 4.4) for 12-year-old children only. Exophoria was more frequent in children of East Asian than European Caucasian origins, even after adjusting for refraction; at near (age 6: OR 1.4, CI 1.0 to 2.0, age 12: OR 1.4, CI 1.0 to 1.9) and distance (age 12: OR 1.7, CI 1.1 to 2.7). CONCLUSION Contrary to other studies, exophoria, not orthophoria, was predominant for near. Exophoria was more prevalent in children of East Asian origin. Longitudinal studies are needed to establish if incident heterotropia is preceded by heterophoria.

  13. Refractive errors among patients attending the ophthalmology department of a medical college in North-East India

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    Tanie Natung

    2017-01-01

    Full Text Available Purpose: To determine the magnitude and pattern of refractive errors among patients attending the ophthalmology department of a new medical college in North-East India. Materials and Methods: A prospective study of the new patients (age ≥5 years, who were phakic and whose unaided visual acuities were worse than 20/20 but improved with pinhole, was done. Complete ophthalmic examination and refraction with appropriate cycloplegia for age were done for the 4582 eligible patients. Spherical equivalents (SE of refractive errors of the right eyes were used for analysis. Results: Of the 4582 eligible patients, 2546 patients had refractive errors (55.56%. The proportion of emmetropia (SE − 0.50–+0.50 diopter sphere [DS], myopia (SE −0.50 DS, high myopia (SE >−5.0 DS, and hypermetropia (+0.50 DS for adults and >+2.0 DS for children were 53.1%, 27.4%, 2.6%, and 16.9%, respectively. The proportion of hyperopia increased till 59 years and then decreased with age (P = 0.000. The proportion of myopia and high myopia decreased significantly with age after 39 years (P = 0.000 and P = 0.004, respectively. Of the 1510 patients with astigmatism, 17% had with-the-rule (WTR, 23.4% had against-the-rule (ATR, and 19% had oblique astigmatisms. The proportion of WTR and ATR astigmatisms significantly decreased (P = 0.000 and increased (P = 0.000 with age, respectively. Conclusions: This study has provided the magnitude and pattern of refractive errors in the study population. It will serve as the initial step for conducting community-based studies on the prevalence of refractive errors in this part of the country since such data are lacking from this region. Moreover, this study will help the primary care physicians to have an overview of the magnitude and pattern of refractive errors presenting to a health-care center as refractive error is an established and significant public health problem worldwide.

  14. Optical correction of refractive error for preventing and treating eye symptoms in computer users.

    Science.gov (United States)

    Heus, Pauline; Verbeek, Jos H; Tikka, Christina

    2018-04-10

    Computer users frequently complain about problems with seeing and functioning of the eyes. Asthenopia is a term generally used to describe symptoms related to (prolonged) use of the eyes like ocular fatigue, headache, pain or aching around the eyes, and burning and itchiness of the eyelids. The prevalence of asthenopia during or after work on a computer ranges from 46.3% to 68.5%. Uncorrected or under-corrected refractive error can contribute to the development of asthenopia. A refractive error is an error in the focusing of light by the eye and can lead to reduced visual acuity. There are various possibilities for optical correction of refractive errors including eyeglasses, contact lenses and refractive surgery. To examine the evidence on the effectiveness, safety and applicability of optical correction of refractive error for reducing and preventing eye symptoms in computer users. We searched the Cochrane Central Register of Controlled Trials (CENTRAL); PubMed; Embase; Web of Science; and OSH update, all to 20 December 2017. Additionally, we searched trial registries and checked references of included studies. We included randomised controlled trials (RCTs) and quasi-randomised trials of interventions evaluating optical correction for computer workers with refractive error for preventing or treating asthenopia and their effect on health related quality of life. Two authors independently assessed study eligibility and risk of bias, and extracted data. Where appropriate, we combined studies in a meta-analysis. We included eight studies with 381 participants. Three were parallel group RCTs, three were cross-over RCTs and two were quasi-randomised cross-over trials. All studies evaluated eyeglasses, there were no studies that evaluated contact lenses or surgery. Seven studies evaluated computer glasses with at least one focal area for the distance of the computer screen with or without additional focal areas in presbyopic persons. Six studies compared computer

  15. The prevalence of refractive error in three communities of Cape Town, South Africa

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    M. Otutu

    2012-12-01

    Full Text Available The prevalence, distribution and demographic associations of refractive error in three communities in Cape Town, South Africa were assessed. In this cross-sectional study, a clustered random sampling procedure was used to recruit participants (n=176; age=40.6±14.7 years; males=76, females=96 from Khayelitsha, Milnerton, and Mitchell’s Plain. From March to May 2010, participants underwent autore-fraction and subjective refraction eye examinations.A structured interview was used to collect data on sociodemographics, age, gender, level of education, employment and race. Participants younger than 15 years, non-residents, or residents for less than six months, who declined signing the informed consent forms were excluded from the study. In this study myopia was defined as the spherical equivalent value in the better eye of −1.00D or worse and hyperopia as the spherical equivalent value in the better eye of ≥1.00D. Astigmatism was defined as −0.50 cylinder or worse in the better eye. The prevalence of myopia was 17.4% with a 90% confidence interval (CI of 12.65-22.15, hyperopia was 13.4% (90% CI 9.13-17.67, and astigmatism was 60% (90% CI 53.86-66.14. Myopia was found to be significantly associated with race and age; while hyperopia was significantly associated with age, employment and race. The results of this study may assist in planning for eye care on district level. (S Afr Optom 2012 71(1 32-38

  16. Ocular residual astigmatism (ORA) in pre-cataract eyes prior to and after refractive lens exchange.

    Science.gov (United States)

    Katz, Toam; Steinberg, Johannes; Druchkiv, Vasyl; Linke, Stephan J; Frings, Andreas

    2017-08-01

    The purpose of this study was to analyze ocular residual astigmatism (ORA) before and after implantation of two different optical types of non-toric multifocal intraocular lenses (MIOL) in pre-cataract patients. This retrospective cohort study analyzed 72 eyes from 72 consecutive patients after MIOL surgery . To investigate magnitude and axis of astigmatic changes, the concepts of true corneal astigmatism and Alpins vector method were applied. There were no statistically significant between-group differences prior to surgery. The mean refractive surgically induced astigmatism (RSIA) (P = 0.063) and the topographic SIA (TSIA) (P = 0.828) did not differ significantly between the lenses, and the summated vector mean for ORA was reduced in terms of magnitude by approximately 0.30 Diopter. ORA in pseudophakic eyes mainly results from the posterior corneal surface and less from IOL tilting, postoperative posterior capsule shrinkage, or secondary cataract.

  17. Is emmetropia the natural endpoint for human refractive development? An analysis of population-based data from the refractive error study in children (RESC).

    Science.gov (United States)

    Morgan, Ian G; Rose, Kathryn A; Ellwein, Leon B

    2010-12-01

    To determine the natural end-point for refractive development during childhood. Cycloplegic (1% cyclopentolate) autorefraction was performed on 38, 811 children aged 5 and 15 in population-based samples at eight sites in the Refractive Error Study in Children (RESC). Refractions (right eye) were categorized as myopic (≤-0.5 D), emmetropic (>-0.5 to ≤+0.5 D), mildly hyperopic (>+0.5 to ≤+2.0 D and hyperopic (>+2.0 D). At five sites (Jhapa - rural Nepal, New Delhi - urban India, Mahabubnagar - rural India, Durban - semi-urban South Africa and La Florida - urban Chile), there was prevalent category at all ages, except for Mahabubnagar where emmetropia became the marginally most prevalent category at ages 14 and 15. At the other sites (Gombak - semi-urban Malaysia, Shunyi - semi-rural China and Guangzhou - urban China), there was substantial (>35%) myopia by age 15. At these sites, mild hyperopia was the most prevalent category during early childhood, and myopia became the predominant category later. In Gombak district and Guangzhou, emmetropia was a minor category at all ages, with myopia increasing as mild hyperopia decreased. In Shunyi district, emmetropia was the most prevalent category over the ages 11-14. Emmetropia was not the predominant outcome for refractive development in children. Instead, populations were predominantly mildly hyperopic or substantial amounts of myopia appeared in them. This suggests that mild hyperopia is the natural state of refractive development in children and that emmetropia during childhood carries the risk of subsequent progression to myopia. © 2009 The Authors. Journal compilation © 2009 Acta Ophthalmol.

  18. Genome-wide meta-analyses of multiancestry cohorts identify multiple new susceptibility loci for refractive error and myopia

    NARCIS (Netherlands)

    Verhoeven, Virginie J. M.; Hysi, Pirro G.; Wojciechowski, Robert; Fan, Qiao; Guggenheim, Jeremy A.; Höhn, René; Macgregor, Stuart; Hewitt, Alex W.; Nag, Abhishek; Cheng, Ching-Yu; Yonova-Doing, Ekaterina; Zhou, Xin; Ikram, M. Kamran; Buitendijk, Gabriëlle H. S.; McMahon, George; Kemp, John P.; Pourcain, Beate St; Simpson, Claire L.; Mäkelä, Kari-Matti; Lehtimäki, Terho; Kähönen, Mika; Paterson, Andrew D.; Hosseini, S. Mohsen; Wong, Hoi Suen; Xu, Liang; Jonas, Jost B.; Pärssinen, Olavi; Wedenoja, Juho; Yip, Shea Ping; Ho, Daniel W. H.; Pang, Chi Pui; Chen, Li Jia; Burdon, Kathryn P.; Craig, Jamie E.; Klein, Barbara E. K.; Klein, Ronald; Haller, Toomas; Metspalu, Andres; Khor, Chiea-Chuen; Tai, E.-Shyong; Aung, Tin; Vithana, Eranga; Tay, Wan-Ting; Barathi, Veluchamy A.; Chen, Peng; Li, Ruoying; Liao, Jiemin; Zheng, Yingfeng; Bergen, Arthur A. B.; Chen, Wei

    2013-01-01

    Refractive error is the most common eye disorder worldwide and is a prominent cause of blindness. Myopia affects over 30% of Western populations and up to 80% of Asians. The CREAM consortium conducted genome-wide meta-analyses, including 37,382 individuals from 27 studies of European ancestry and

  19. TO ASSESS THE IMPACT OF THE EDUCATIONAL INTERVENTIONS FOR UNCORRECTED REFRACTIVE ERROR AMONG SCHOOL CHILDREN IN MEERUT.

    Directory of Open Access Journals (Sweden)

    A Davey

    2013-08-01

    Full Text Available Background: Eyes are the best God gift to our body as vision is important in development as it allows interaction with the environment. Appropriate correction prevents the development of childhood amblyopia and enables better performance at school. Later in life carrier of the youth is very much dependent on the visual acuity. Therefore study aims to find the prevalence of the uncorrected refractive error among school children in the age group of 13-16 years and factors contributing to the refractive error. Methods: It is institutional based crossed sectional study in English medium private school children in the age group 13-16 years. For one week they were screened for visual acuity from a Standard Snellen Chart. On pre-informed date educational intervention was conducted; they were followed up after one week of intervention for final assessment. Results: Prevalence of the uncorrected refractive error was 14.8% Distance for watching TV less than 3 m and computer less than 1 m were highly significant. Prolonged duration of TV watching for more than 4 hours in a day and indulgence in computers for more than one year were also significant. In follow up after education intervention, all the children with uncorrected refractive error except 2 had paid visit to ophthalmologist. Conclusion: Community based screening through school is most appropriate strategy to detect early any visual impairment, but school based approach must include teachers orientation also for prevention of eye disease.

  20. Cost-effectiveness of screening and correcting refractive errors in school children in Africa, Asia, America and Europe.

    NARCIS (Netherlands)

    Baltussen, R.M.P.M.; Naus, J.; Limburg, H.

    2009-01-01

    OBJECTIVE: To estimate the costs and effects of alternative strategies for annual screening of school children for refractive errors, and the provision of spectacles, in different WHO sub-regions in Africa, Asia, America and Europe. METHODS: We developed a mathematical simulation model for

  1. Refractive error and presbyopia in timor-leste: the impact of 5 years of a national spectacle program.

    Science.gov (United States)

    Ramke, Jacqueline; Brian, Garry; Naduvilath, Thomas

    2012-01-25

    To characterize refractive error, presbyopia, and spectacle correction among adults aged ≥40 years in Timor-Leste in 2010 and examine the impact of the National Spectacle Program by comparing results to those obtained 5 years earlier. A population-based, cross-sectional survey sampled 50 clusters of 45 people each. Participants with uncorrected and undercorrected refractive error (presenting visual acuity <6/18, but ≥6/18 in the better eye with pinhole), uncorrected and undercorrected presbyopia (refractive error (≥6/18 in the better eye with presenting spectacles), and corrected presbyopia (binocular ≥N8 with presenting spectacles) were identified. Willingness to wear and to pay for spectacles was elicited. Data were adjusted for sex, age, and urban/rural domicile, to compare results from 2005 and 2010. A participation rate of 89.5% (n = 2014) was achieved. The 2010 sex-age-domicile-adjusted parameters were as follows: 3.7% (95% confidence interval [CI], 2.8%-4.5%) met refractive error need; 9.6% (95% CI, 8.3%-10.9%) unmet refractive error need; 27.6% (95% CI, 22.2%-32.9%) refractive error correction coverage; 8.6% (95% CI, 7.4%-9.8%) met presbyopia need; 41.8% (95% CI, 39.7%-44.0%) unmet presbyopia need; and, 17.0% (95% CI, 14.7%-19.3%) presbyopia correction coverage. Refractive error correction coverage was significantly higher in 2010 than in 2005 (8.0%; 95% CI, 4.5%-11.6%), but presbyopia correction coverage was unchanged. Almost all the 2010 sample (99.5%) were willing to wear spectacles if needed. Sex-age-domicile-adjusted willingness to pay at least US$1.00 for spectacles was 56.9% (95% CI, 54.7%-59.1%) in 2010, significantly greater than in 2005 (47.2%; 95% CI, 44.5%-49.9%). The National Spectacle Program has not produced uniform improvement across all service indicators. Evidence-based enhancements may now be initiated.

  2. Racial variations in the prevalence of refractive errors in the United States: the multi-ethnic study of atherosclerosis.

    Science.gov (United States)

    Pan, Chen-Wei; Klein, Barbara E K; Cotch, Mary Frances; Shrager, Sandi; Klein, Ronald; Folsom, Aaron; Kronmal, Richard; Shea, Steven J; Burke, Gregory L; Saw, Seang-Mei; Wong, Tien Y

    2013-06-01

    To describe racial variations in the prevalence of refractive errors among adult white, Chinese, Hispanic, and black subjects in the United States. Cross-sectional data from a prospective cohort study-the Multi-Ethnic Study of Atherosclerosis (MESA). A total of 6000 adults aged 45 to 84 years living in the United States participated in the study. Refractive error was assessed, without cycloplegia, in both eyes of all participants using an autorefractor. After excluding eyes with cataract, cataract surgery, or previous refractive surgery, the eye with the larger absolute spherical equivalent (SE) value for each participant was used to classify refractive error. Any myopia was defined as SE of -1.0 diopters (D) or less; high myopia was defined as SE of -5.0 D or less; any hyperopia was defined as SE of +1.0 D or more; clinically significant hyperopia was defined as SE of +3.0 D or more. Astigmatism was defined as a cylinder value of +1.0 D or more. After excluding 508 participants with cataracts in both eyes, 838 participants with cataract surgery, 90 participants with laser refractive surgery, and 134 participants who refused to remove their contact lenses for the refraction measurement, 4430 adults with refractive error assessment in at least 1 eye contributed to the analysis. The prevalence of myopia among MESA participants was 25.1%, with lowest rates in Hispanic participants (14.2%), followed by black (21.5%) and white participants (31.0%), and highest rates in Chinese participants (37.2%). The overall rates of high myopia and astigmatism were 4.6% and 45.0%, respectively, with Chinese subjects also having the highest rates of high myopia (11.8%) and astigmatism (53.4%). The overall prevalence of any hyperopia was 38.2% and clinically significant hyperopia was 6.1%, with Hispanic participants having the highest rates of hyperopia (50.2%) and clinically significant hyperopia (8.8%). In multivariate analyses adjusting for age, sex, race, and study site, higher

  3. Analysis of refractive error in visual impairment among residents aged 40 years and above in Dongguan City

    Directory of Open Access Journals (Sweden)

    Shu-Hui Chen

    2015-06-01

    Full Text Available AIM: To investigate the prevalence rate of visual impairment caused by refractive error among residents aged 40 years and above, and the influence factors of vision correction. METHODS: We conducted an epidemiological survey of diabetes and diabetic retinopathy among residents aged 40 and above in Guangdong Province, Hengli Town, Dongguan City from 2011 to 2012. At the same time, according to World Health Organization(WHO, according to the daily life vision, 0.05≤visual ability RESULTS: The prevalence rate of visual impairment was 7.90%(707/8 952. The prevalence rate of visual impairment caused by refractive error was 5.57%(499/8 952, accounted for visual impairment of 70.58%(499/707. The prevalence rate of correction of refractive error among visual impairment was 5.36%(480/8 952, accounting for visual impairment of 67.89%(480/707. The prevalence rate of visual impairment uncorrected was 0.21%(19/8 952, accounting for visual impairment of 2.69%(19/707. By χ2 test, with the increase of age, the rate of visual impairment caused by refractive error was significantly decreased(PPP>0.05. The rate of visual impairment can be corrected decreases with age, from 92.1% to 49.1%, there was a statistically significant difference(PPP>0.05. CONCLUSION: Through the development of refractive error correction of positive, can make the daily life of visual impairment in about 2/3 of patients improve eyesight and improve the quality of life of residents.

  4. Knowledge, attitude and associated factors among primary school teachers regarding refractive error in school children in Gondar city, Northwest Ethiopia.

    Science.gov (United States)

    Alemayehu, Abiy Maru; Belete, Gizchewu Tilahun; Adimassu, Nebiyat Feleke

    2018-01-01

    Refractive error is an important cause of correctable visual impairment in the worldwide with a global distribution of 1.75% to 20.7% among schoolchildren. Teacher's knowledge about refractive error play an important role in encouraging students to seek treatment that helps in reducing the burden of visual impairment. To determine knowledge, attitude and associated factors among primary school teachers regarding refractive error in school children in Gondar city. Institution based cross-sectional study was conducted on 565 primary school teachers in Gondar city using pretested and structured self-administered questionnaire. For processing and analysis, SPSS version 20 was used and variables which had a P value of knowledge and 57.2% (95% CI: 52.9, 61.4) had favorable attitude towards refractive error. History of spectacle use [AOR = 2.13 (95% CI: 1.32, 3.43)], history of eye examination [AOR = 1.67 (95% CI: 1.19, 2.34)], training on eye health [AOR = 1.94 (95% CI; 1.09, 3.43)] and 11-20 years of experience [AOR = 2.53 (95% CI: 1.18, 5.43)] were positively associated with knowledge. Whereas being male [AOR = 2.03 (95% CI: 1.37, 3.01)], older age [AOR = 3.05 (95% CI: 1.07, 8.72)], 31-40 years of experience [AOR = 0.23 (95% CI: 0.07, 0.72)], private school type [AOR = 1.76 (95% CI: 1.06, 2.93)] and 5th -8th teaching category [AOR = 1.54 (95% CI: 1.05, 2.24)] were associated with attitude. Knowledge and attitude of study subjects were low which needs training of teachers about the refractive error.

  5. Heritability of strabismus: genetic influence is specific to eso-deviation and independent of refractive error.

    Science.gov (United States)

    Sanfilippo, Paul G; Hammond, Christopher J; Staffieri, Sandra E; Kearns, Lisa S; Melissa Liew, S H; Barbour, Julie M; Hewitt, Alex W; Ge, Dongliang; Snieder, Harold; Mackinnon, Jane R; Brown, Shayne A; Lorenz, Birgit; Spector, Tim D; Martin, Nicholas G; Wilmer, Jeremy B; Mackey, David A

    2012-10-01

    Strabismus represents a complex oculomotor disorder characterized by the deviation of one or both eyes and poor vision. A more sophisticated understanding of the genetic liability of strabismus is required to guide searches for associated molecular variants. In this classical twin study of 1,462 twin pairs, we examined the relative influence of genes and environment in comitant strabismus, and the degree to which these influences can be explained by factors in common with refractive error. Participants were examined for the presence of latent ('phoria') and manifest ('tropia') strabismus using cover-uncover and alternate cover tests. Two phenotypes were distinguished: eso-deviation (esophoria and esotropia) and exo-deviation (exophoria and exotropia). Structural equation modeling was subsequently employed to partition the observed phenotypic variation in the twin data into specific variance components. The prevalence of eso-deviation and exo-deviation was 8.6% and 20.7%, respectively. For eso-deviation, the polychoric correlation was significantly greater in monozygotic (MZ) (r = 0.65) compared to dizygotic (DZ) twin pairs (r = 0.33), suggesting a genetic role (p = .003). There was no significant difference in polychoric correlation between MZ (r = 0.55) and DZ twin pairs (r = 0.53) for exo-deviation (p = .86), implying that genetic factors do not play a significant role in the etiology of exo-deviation. The heritability of an eso-deviation was 0.64 (95% CI 0.50-0.75). The additive genetic correlation for eso-deviation and refractive error was 0.13 and the bivariate heritability (i.e., shared variance) was less than 1%, suggesting negligible shared genetic effect. This study documents a substantial heritability of 64% for eso-deviation, yet no corresponding heritability for exo-deviation, suggesting that the genetic contribution to strabismus may be specific to eso-deviation. Future studies are now needed to identify the genes associated with eso-deviation and

  6. The Association of Central corneal thickness with Intra-ocular Pressure and Refractive Error in a Nigerian Population

    OpenAIRE

    Iyamu, Eghosasere; Memeh, Misan

    2008-01-01

    The purpose of this study was to determine the variation of central corneal thickness (CCT) with intraocular pressure (IOP) and spherical equivalent refractive error. A total of thirty-nine (N=39) subjects within 20-75 years with mean age 45.2 ± 15.4 years were used for this study. The central corneal thickness was assessed with the Corneo-Gage plus ultrasonic Pachymeter, the IOP with slit-lamp mounted Goldmann applanation tonometer and refractive status by Protec 2000 autorefractor, phoropte...

  7. Compensation of X-ray mirror shape-errors using refractive optics

    Energy Technology Data Exchange (ETDEWEB)

    Sawhney, Kawal, E-mail: Kawal.sawhney@diamond.ac.uk; Laundy, David; Pape, Ian [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom); Dhamgaye, Vishal [Indus Synchrotrons Utilisation Division, Raja Ramanna Centre for Advanced Technology, Indore 452012 (India)

    2016-08-01

    Focusing of X-rays to nanometre scale focal spots requires high precision X-ray optics. For nano-focusing mirrors, height errors in the mirror surface retard or advance the X-ray wavefront and after propagation to the focal plane, this distortion of the wavefront causes blurring of the focus resulting in a limit on the spatial resolution. We describe here the implementation of a method for correcting the wavefront that is applied before a focusing mirror using custom-designed refracting structures which locally cancel out the wavefront distortion from the mirror. We demonstrate in measurements on a synchrotron radiation beamline a reduction in the size of the focal spot of a characterized test mirror by a factor of greater than 10 times. This technique could be used to correct existing synchrotron beamline focusing and nanofocusing optics providing a highly stable wavefront with low distortion for obtaining smaller focus sizes. This method could also correct multilayer or focusing crystal optics allowing larger numerical apertures to be used in order to reduce the diffraction limited focal spot size.

  8. Spherical equivalent refractive error in preschool children from a population with a high prevalence of astigmatism.

    Science.gov (United States)

    Dobson, Velma; Harvey, Erin M; Miller, Joseph M

    2007-02-01

    To describe spherical equivalent (sph eq) refractive errors in preschool members of a Native American tribe with a high prevalence of astigmatism. Cycloplegic autorefraction measurements were obtained for 819 three- and four-year-old Tohono O'odham children, with follow-up measurements in 146 after 4 to 8 years. Mean sph eq was significantly more hyperopic in the astigmatic group than in the non-astigmatic group (1.24 vs. 0.87 D). At follow-up, prevalence of hyperopic sph eq and hyperopic astigmatism had significantly decreased, and prevalence of emmetropic/myopic sph eq and myopic astigmatism had significantly increased. The decrease in mean sph eq was similar in astigmats and non-astigmats. Astigmatism did not change over time. Most preschool children in this highly astigmatic population are hyperopic, with astigmats showing higher mean hyperopic sph eq than non-astigmats. Astigmats and non-astigmats show a similar decrease in amount of hyperopic sph eq over follow-up of 4 to 8 years.

  9. Correlations between refractive error and biometric parameters in human eyes using the LenStar 900.

    Science.gov (United States)

    O'Donnell, Clare; Hartwig, Andreas; Radhakrishnan, Hema

    2011-02-01

    To investigate the relationship between refractive error and ocular biometry in healthy subjects using a new optical low coherence reflectometry device. Biometric measurements were obtained with a LenStar LS 900 (Haag Streit, Switzerland) on one eye of 70 phakic subjects (mean ± SD age; 29 ± 9 years). Forty myopes and 30 non-myopes (best sphere range -9.63 D to +0.63 D) were included. Outcome measures were compared for the two groups using one way between groups ANOVA. These included; keratometry, central corneal thickness, iris width, anterior chamber depth, pupil diameter, lens thickness, axial length and retinal thickness. No mydriatic or cycloplegic agents were used. There were significant differences between groups for keratometry readings (p = 0.021 and p = 0.038 for steep and flat k readings respectively), anterior chamber depth (p = 0.001), lens thickness (p = 0.026) and axial length (pbiometric parameters assessed and provides information about the relationships between these biometric parameters and age. The results, coupled with a unique ability to image and analyse the ocular structures non-invasively make the LenStar a promising new instrument for ocular evaluation in research and clinical practice. Copyright © 2010 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

  10. Refractive Errors and Amblyopia in the UCLA Preschool Vision Program; First Year Results.

    Science.gov (United States)

    Hendler, Karen; Mehravaran, Shiva; Lu, Xiang; Brown, Stuart I; Mondino, Bartly J; Coleman, Anne L

    2016-12-01

    To report the outcomes of full ophthalmic examination for preschool children in LA County who failed screening with the Retinomax Autorefractor. Retrospective, cross-sectional study. Between August 2012 and May 2013, the University of California Los Angeles (UCLA) preschool vision program screened 11 260 preschool children aged 3-5 years in Los Angeles County using the Retinomax Autorefractor only. Of those, 1007 children who failed the screening were examined by an ophthalmologist on the UCLA Mobile Eye Clinic. Data from the eye examination were recorded for all children. Amblyopia was defined as unilateral if there was ≥2 line interocular difference in the best-corrected visual acuity (BCVA) and as bilateral if BCVA was amblyopia was found in 9% of those examined, or 0.8% of the original population. Of the amblyopic subjects, 77% were unilateral. Screening of preschoolers with the Retinomax led to diagnosis and early treatment of uncorrected refractive errors and amblyopia. By treating children early, amblyopia may be prevented, quality of life improved, and academic achievements enhanced. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. The Study of Refractive Errors among Carpet Weaver Women in Rural Sephidehkesh of Qazvin, Qazvin, Iran

    Directory of Open Access Journals (Sweden)

    Nikpey A

    2012-09-01

    Full Text Available Background and Objectives: Carpet weaver women due to long working in inappropriate environment are at risk for certain eye disease. The aim of this study is to determine the refractive errors among carpet weavers women in rural Sephidehkesh of Qazvin.Methods: 28 Carpet weaver women were under optometric eye examinations. Light Intensity at work stations was measured, using luxmeter and eye examinations were done by using the ophthalmoscope and retinoscop. Data were analyzed using one-side T-test.Results: The result of this study showed, general and local light intensity in 13 carpet weaving workshops, respectively 160 and 154 Lux that was much less than the minimum and maximum recommended values of 200 to 300 Lux. Only one of 28 Carpet weaver women was healthy and others were visually impaired. In addition to poor eyesight, workers complained of headache, itching and burning eyes.Conclusion: The results show, due to inappropriate working condition in carpet weaving workshops, most young workers are suffering from eye impairment and is predicted the severity of myopia to increase with working experience and age.

  12. Refractive errors progression among pupils in Hetian Road primary school of Shanghai: 1-year followed-up

    Directory of Open Access Journals (Sweden)

    Hui Shi

    2013-12-01

    Full Text Available AIM:To investigate the progression of refractive errors of pupils in Hetian Road primary school of Shanghai Zhabei community and analyze the relationship between refractive errors progression and relative factors. METHODS:All the 6-12 years old in-school pupils in Hetian Road primary school of Shanghai Zhabei community were invited in the study. The participates were examined first-visit in May 2011 and second-visit in May 2012. All the 303 pupils(606 eyeswere investigated the age, height(H, weight(W, uncorrected visual acuity(UCVA, diopter of spherical(DS, diopter of cylinder(DC, spherical equivalent(SE, axial length(AL, and corneal curvature(K. The progression of refractive condition was described and the relevant factors were analyzed.RESULTS:Among 606 eyes, the progression of average SE was -0.45±0.60D and the progression of average AL was 0.32±0.25mm. The progression of SE diopter was positively correlated with the progression of AL(r=0.409, PP=0.004. The youngest pupils with 6-8 years old, had the fastest progression of AL(0.39±0.24mm, PP>0.05. The incidence of poor sight(UCVACONCLUSION:Myopia is the main progression of refractive error in the pupils of Hetian Road primary school in Shanghai Zhabei community. AL and growth development is closely related to the progression of refractive errors.

  13. Screening for significant refractive error using a combination of distance visual acuity and near visual acuity.

    Directory of Open Access Journals (Sweden)

    Peiyao Jin

    Full Text Available To explore the effectiveness of using a series of tests combining near visual acuity (NVA and distance visual acuity (DVA for large-scale screenings for significant refractive error (SRE in primary school children.Each participant underwent DVA, NVA and cycloplegic autorefraction measurements. SREs, including high myopia, high hyperopia and high astigmatism were analyzed. Cycloplegic refraction results were considered to be the gold standard for the comparison of different screening measurements. Receiver-operating characteristic (ROC curves were constructed to compare the area under the curve (AUC and the Youden index among DVA, NVA and the series combined tests of DVA and NVA. The efficacies (including sensitivity, specificity, positive predictive value, and negative predictive value of each test were evaluated. Only the right eye data of each participant were analysed for statistical purpose.A total of 4416 children aged 6 to 12 years completed the study, among which 486 students had right eye SRE (SRE prevalence rate = 11.01%. There was no difference in the prevalence of high hyperopia and high astigmatism among different age groups. However, the prevalence of high myopia significantly increased with the age (χ² = 381.81, p<0.01. High hyperopia was the biggest SRE factor associated with amblyopia(p<0.01,OR = 167.40, 95% CI: 75.14∼372.94. The DVA test was better than the NVA test for detecting high myopia (Z = 2.71, p<0.01, but the NVA test was better for detecting high hyperopia (Z = 2.35, p = 0.02 and high astigmatism (Z = 4.45, p<0.01. The series combined DVA and NVA test had the biggest AUC and the highest Youden Index for detecting high hyperopia, myopia, astigmatism, as well as all of the SREs (all p<0.01.The series combined DVA and NVA test was more accurate for detecting SREs than either of the two tests alone. This new method could be applied to large-scale SRE screening of children, aged 6 to 12, in areas that are less

  14. Screening for significant refractive error using a combination of distance visual acuity and near visual acuity.

    Science.gov (United States)

    Jin, Peiyao; Zhu, Jianfeng; Zou, Haidong; Lu, Lina; Zhao, Huijuan; Li, Qiangqiang; He, Xiangui

    2015-01-01

    To explore the effectiveness of using a series of tests combining near visual acuity (NVA) and distance visual acuity (DVA) for large-scale screenings for significant refractive error (SRE) in primary school children. Each participant underwent DVA, NVA and cycloplegic autorefraction measurements. SREs, including high myopia, high hyperopia and high astigmatism were analyzed. Cycloplegic refraction results were considered to be the gold standard for the comparison of different screening measurements. Receiver-operating characteristic (ROC) curves were constructed to compare the area under the curve (AUC) and the Youden index among DVA, NVA and the series combined tests of DVA and NVA. The efficacies (including sensitivity, specificity, positive predictive value, and negative predictive value) of each test were evaluated. Only the right eye data of each participant were analysed for statistical purpose. A total of 4416 children aged 6 to 12 years completed the study, among which 486 students had right eye SRE (SRE prevalence rate = 11.01%). There was no difference in the prevalence of high hyperopia and high astigmatism among different age groups. However, the prevalence of high myopia significantly increased with the age (χ² = 381.81, p<0.01). High hyperopia was the biggest SRE factor associated with amblyopia(p<0.01,OR = 167.40, 95% CI: 75.14∼372.94). The DVA test was better than the NVA test for detecting high myopia (Z = 2.71, p<0.01), but the NVA test was better for detecting high hyperopia (Z = 2.35, p = 0.02) and high astigmatism (Z = 4.45, p<0.01). The series combined DVA and NVA test had the biggest AUC and the highest Youden Index for detecting high hyperopia, myopia, astigmatism, as well as all of the SREs (all p<0.01). The series combined DVA and NVA test was more accurate for detecting SREs than either of the two tests alone. This new method could be applied to large-scale SRE screening of children, aged 6 to 12, in areas that are less

  15. distribution of refractive errors among school children in abia state of ...

    African Journals Online (AJOL)

    INTRODUCTION. The “refractive status” of the eye is an expression used to denote the relationship between the refractive mechanism (dioptrics) of the eye and the spatial location of the sensory layer of the eye (retina). This is broadly classified into two groups–emmertropia and ametropia. The latter term is employed to ...

  16. Prevalence of visual impairment and uncorrected refractive error - report from a Canadian urban population-based study.

    Science.gov (United States)

    Robinson, Barbara; Feng, Yunwei; Woods, Craig A; Fonn, Desmond; Gold, Deborah; Gordon, Keith

    2013-06-01

    The prevalence of visual impairment due to uncorrected refractive error has not been previously studied in Canada. A population-based study was conducted in Brantford, Ontario. The target population included all people 40 years of age and older. Study participants were selected using a randomized sampling strategy based on postal codes. Presenting distance and near visual acuities were measured with habitual spectacle correction, if any, in place. Best corrected visual acuities were determined for all participants who had a presenting distance visual acuity of less than 20/25. Population weighted prevalence of distance visual impairment (visual acuity refraction. Population weighted prevalence of near visual impairment (visual acuity refraction. Multivariable adjusted analysis showed that the odds of having distance visual impairment was independently associated with increased age (odds ratio, OR, 3.56, 95% CI 1.22-10.35; ≥65 years compared to those 39-64 years), and time since last eye examination (OR 4.93, 95% CI 1.19-20.32; ≥5 years compared to ≤2 years). The same factors appear to be associated with increased prevalence of near visual impairment but were not statistically significant. The majority of visual impairment found in Brantford was due to uncorrected refractive error. Factors that increased the prevalence of visual impairment were the same for distance and near visual acuity measurements.

  17. The Association of Central corneal thickness with Intra-ocular Pressure and Refractive Error in a Nigerian Population

    Directory of Open Access Journals (Sweden)

    Eghosasere Iyamu

    2008-01-01

    Full Text Available The purpose of this study was to determine the variation of central corneal thickness (CCT with intraocular pressure (IOP and spherical equivalent refractive error. A total of thirty-nine (N=39 subjects within 20-75 years with mean age 45.2 ± 15.4 years were used for this study. The central corneal thickness was assessed with the Corneo-Gage plus ultrasonic Pachymeter, the IOP with slit-lamp mounted Goldmann applanation tonometer and refractive status by Protec 2000 autorefractor, phoropter and trial lens set. Results obtained showed that there was no linear correlation between CCT and spherical equivalent errors, although the association between them was significant (p<0.05. The linear correlation between CCT and IOP was not statistically significant. The central corneal thickness was weakly correlated with age; with increasing age the central corneal thickness decreases. Neither the central corneal thickness nor the intraocular pressure was affected by gender.

  18. Education influences the association between genetic variants and refractive error: a meta-analysis of five Singapore studies.

    Science.gov (United States)

    Fan, Qiao; Wojciechowski, Robert; Kamran Ikram, M; Cheng, Ching-Yu; Chen, Peng; Zhou, Xin; Pan, Chen-Wei; Khor, Chiea-Chuen; Tai, E-Shyong; Aung, Tin; Wong, Tien-Yin; Teo, Yik-Ying; Saw, Seang-Mei

    2014-01-15

    Refractive error is a complex ocular trait governed by both genetic and environmental factors and possibly their interplay. Thus far, data on the interaction between genetic variants and environmental risk factors for refractive errors are largely lacking. By using findings from recent genome-wide association studies, we investigated whether the main environmental factor, education, modifies the effect of 40 single nucleotide polymorphisms on refractive error among 8461 adults from five studies including ethnic Chinese, Malay and Indian residents of Singapore. Three genetic loci SHISA6-DNAH9, GJD2 and ZMAT4-SFRP1 exhibited a strong association with myopic refractive error in individuals with higher secondary or university education (SHISA6-DNAH9: rs2969180 A allele, β = -0.33 D, P = 3.6 × 10(-6); GJD2: rs524952 A allele, β = -0.31 D, P = 1.68 × 10(-5); ZMAT4-SFRP1: rs2137277 A allele, β = -0.47 D, P = 1.68 × 10(-4)), whereas the association at these loci was non-significant or of borderline significance in those with lower secondary education or below (P for interaction: 3.82 × 10(-3)-4.78 × 10(-4)). The evidence for interaction was strengthened when combining the genetic effects of these three loci (P for interaction = 4.40 × 10(-8)), and significant interactions with education were also observed for axial length and myopia. Our study shows that low level of education may attenuate the effect of risk alleles on myopia. These findings further underline the role of gene-environment interactions in the pathophysiology of myopia.

  19. Education influences the association between genetic variants and refractive error: a meta-analysis of five Singapore studies

    Science.gov (United States)

    Fan, Qiao; Wojciechowski, Robert; Kamran Ikram, M.; Cheng, Ching-Yu; Chen, Peng; Zhou, Xin; Pan, Chen-Wei; Khor, Chiea-Chuen; Tai, E-Shyong; Aung, Tin; Wong, Tien-Yin; Teo, Yik-Ying; Saw, Seang-Mei

    2014-01-01

    Refractive error is a complex ocular trait governed by both genetic and environmental factors and possibly their interplay. Thus far, data on the interaction between genetic variants and environmental risk factors for refractive errors are largely lacking. By using findings from recent genome-wide association studies, we investigated whether the main environmental factor, education, modifies the effect of 40 single nucleotide polymorphisms on refractive error among 8461 adults from five studies including ethnic Chinese, Malay and Indian residents of Singapore. Three genetic loci SHISA6-DNAH9, GJD2 and ZMAT4-SFRP1 exhibited a strong association with myopic refractive error in individuals with higher secondary or university education (SHISA6-DNAH9: rs2969180 A allele, β = −0.33 D, P = 3.6 × 10–6; GJD2: rs524952 A allele, β = −0.31 D, P = 1.68 × 10−5; ZMAT4-SFRP1: rs2137277 A allele, β = −0.47 D, P = 1.68 × 10−4), whereas the association at these loci was non-significant or of borderline significance in those with lower secondary education or below (P for interaction: 3.82 × 10−3–4.78 × 10−4). The evidence for interaction was strengthened when combining the genetic effects of these three loci (P for interaction = 4.40 × 10−8), and significant interactions with education were also observed for axial length and myopia. Our study shows that low level of education may attenuate the effect of risk alleles on myopia. These findings further underline the role of gene–environment interactions in the pathophysiology of myopia. PMID:24014484

  20. Prevalence of vision impairment and refractive error in school children in Ba Ria - Vung Tau province, Vietnam.

    Science.gov (United States)

    Paudel, Prakash; Ramson, Prasidh; Naduvilath, Thomas; Wilson, David; Phuong, Ha Thanh; Ho, Suit M; Giap, Nguyen V

    2014-04-01

    To assess the prevalence of vision impairment and refractive error in school children 12-15 years of age in Ba Ria - Vung Tau province, Vietnam. Prospective, cross-sectional study. 2238 secondary school children. Subjects were selected based on stratified multistage cluster sampling of 13 secondary schools from urban, rural and semi-urban areas. The examination included visual acuity measurements, ocular motility evaluation, cycloplegic autorefraction, and examination of the external eye, anterior segment, media and fundus. Visual acuity and principal cause of vision impairment. The prevalence of uncorrected and presenting visual acuity ≤6/12 in the better eye were 19.4% (95% confidence interval, 12.5-26.3) and 12.2% (95% confidence interval, 8.8-15.6), respectively. Refractive error was the cause of vision impairment in 92.7%, amblyopia in 2.2%, cataract in 0.7%, retinal disorders in 0.4%, other causes in 1.5% and unexplained causes in the remaining 2.6%. The prevalence of vision impairment due to myopia in either eye (-0.50 diopter or greater) was 20.4% (95% confidence interval, 12.8-28.0), hyperopia (≥2.00 D) was 0.4% (95% confidence interval, 0.0-0.7) and emmetropia with astigmatism (≥0.75 D) was 0.7% (95% confidence interval, 0.2-1.2). Vision impairment due to myopia was associated with higher school grade and increased time spent reading and working on a computer. Uncorrected refractive error, particularly myopia, among secondary school children in Vietnam is a major public health problem. School-based eye health initiative such as refractive error screening is warranted to reduce vision impairment. © 2013 The Authors. Clinical & Experimental Ophthalmology published by Wiley Publishing Asia Pty Ltd on behalf of Royal Australian and New Zealand College of Ophthalmologists.

  1. Prevalence of vision impairment and refractive error in school children in Ba Ria – Vung Tau province, Vietnam

    Science.gov (United States)

    Paudel, Prakash; Ramson, Prasidh; Naduvilath, Thomas; Wilson, David; Phuong, Ha Thanh; Ho, Suit M; Giap, Nguyen V

    2014-01-01

    Background To assess the prevalence of vision impairment and refractive error in school children 12–15 years of age in Ba Ria – Vung Tau province, Vietnam. Design Prospective, cross-sectional study. Participants 2238 secondary school children. Methods Subjects were selected based on stratified multistage cluster sampling of 13 secondary schools from urban, rural and semi-urban areas. The examination included visual acuity measurements, ocular motility evaluation, cycloplegic autorefraction, and examination of the external eye, anterior segment, media and fundus. Main Outcome Measures Visual acuity and principal cause of vision impairment. Results The prevalence of uncorrected and presenting visual acuity ≤6/12 in the better eye were 19.4% (95% confidence interval, 12.5–26.3) and 12.2% (95% confidence interval, 8.8–15.6), respectively. Refractive error was the cause of vision impairment in 92.7%, amblyopia in 2.2%, cataract in 0.7%, retinal disorders in 0.4%, other causes in 1.5% and unexplained causes in the remaining 2.6%. The prevalence of vision impairment due to myopia in either eye (–0.50 diopter or greater) was 20.4% (95% confidence interval, 12.8–28.0), hyperopia (≥2.00 D) was 0.4% (95% confidence interval, 0.0–0.7) and emmetropia with astigmatism (≥0.75 D) was 0.7% (95% confidence interval, 0.2–1.2). Vision impairment due to myopia was associated with higher school grade and increased time spent reading and working on a computer. Conclusions Uncorrected refractive error, particularly myopia, among secondary school children in Vietnam is a major public health problem. School-based eye health initiative such as refractive error screening is warranted to reduce vision impairment. PMID:24299145

  2. Refractive error and risk of early or late age-related macular degeneration: a systematic review and meta-analysis.

    Science.gov (United States)

    Li, Ying; Wang, Jiwen; Zhong, Xiaojing; Tian, Zhen; Wu, Peipei; Zhao, Wenbo; Jin, Chenjin

    2014-01-01

    To summarize relevant evidence investigating the associations between refractive error and age-related macular degeneration (AMD). Systematic review and meta-analysis. We searched Medline, Web of Science, and Cochrane databases as well as the reference lists of retrieved articles to identify studies that met the inclusion criteria. Extracted data were combined using a random-effects meta-analysis. Studies that were pertinent to our topic but did not meet the criteria for quantitative analysis were reported in a systematic review instead. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) for the associations between refractive error (hyperopia, myopia, per-diopter increase in spherical equivalent [SE] toward hyperopia, per-millimeter increase in axial length [AL]) and AMD (early and late, prevalent and incident). Fourteen studies comprising over 5800 patients were eligible. Significant associations were found between hyperopia, myopia, per-diopter increase in SE, per-millimeter increase in AL, and prevalent early AMD. The pooled ORs and 95% CIs were 1.13 (1.06-1.20), 0.75 (0.56-0.94), 1.10 (1.07-1.14), and 0.79 (0.73-0.85), respectively. The per-diopter increase in SE was also significantly associated with early AMD incidence (OR, 1.06; 95% CI, 1.02-1.10). However, no significant association was found between hyperopia or myopia and early AMD incidence. Furthermore, neither prevalent nor incident late AMD was associated with refractive error. Considerable heterogeneity was found among studies investigating the association between myopia and prevalent early AMD (P = 0.001, I2 = 72.2%). Geographic location might play a role; the heterogeneity became non-significant after stratifying these studies into Asian and non-Asian subgroups. Refractive error is associated with early AMD but not with late AMD. More large-scale longitudinal studies are needed to further investigate such associations.

  3. Vision screening to detect refractive errors in three selected secondary schools in Birnin Kebbi, North West, Nigeria

    Directory of Open Access Journals (Sweden)

    Aliyu Hamza Balarabe

    2015-01-01

    Full Text Available Objective: The objective of this study was to determine the prevalence of uncorrected refractive error among students in three selected secondary schools in Birnin Kebbi metropolis as many children with poor vision due to refractive error remain undiagnosed and perform poorly in schools. Materials and Methods: This was a cross-sectional study that was conducted over a period of 2 months (May-June 2014. A total of 614 students were included from three randomly chosen secondary schools in Birnin Kebbi, Nigeria. Subjects were selected using random sampling technique from the list of students available through the help of their class teachers. Visual acuity (VA was measured with a Snellen chart, while students with subnormal vision (VA ≤ 6/9 were examined using pinhole, and subsequently referred for detailed eye examination and retinoscopy evaluation. Results: The age range was from 11 to 20 years comprising 50.8% (n = 312 males and 48.2% (n = 302 females. Refractive error in either eye was present in 30 (4.8% children. Of these, myopia was diagnosed in 18 (60% children, and then hyperopia in 7 (23.3%, and astigmatism in 5 (16.7% subjects. Spectacle coverage was low as only three pupils were found to be using glasses with lack of awareness and lack of access to eye care services as major barriers. Conclusions: Uncorrected refractive error is found among secondary schools students in Birnin Kebbi, and there is a need for the establishment of regular and effective school vision screening program to detect and refer patients for treatment.

  4. Prevalence of vision impairment and refractive error in school children in Ba Ria ? Vung Tau province, Vietnam

    OpenAIRE

    Paudel, Prakash; Ramson, Prasidh; Naduvilath, Thomas; Wilson, David; Phuong, Ha Thanh; Ho, Suit M; Giap, Nguyen V

    2014-01-01

    Background To assess the prevalence of vision impairment and refractive error in school children 12?15 years of age in Ba Ria ? Vung Tau province, Vietnam. Design Prospective, cross-sectional study. Participants 2238 secondary school children. Methods Subjects were selected based on stratified multistage cluster sampling of 13 secondary schools from urban, rural and semi-urban areas. The examination included visual acuity measurements, ocular motility evaluation, cycloplegic autorefraction, a...

  5. Prevalence of visual impairment due to uncorrected refractive error: Results from Delhi-Rapid Assessment of Visual Impairment Study.

    Science.gov (United States)

    Senjam, Suraj Singh; Vashist, Praveen; Gupta, Noopur; Malhotra, Sumit; Misra, Vasundhara; Bhardwaj, Amit; Gupta, Vivek

    2016-05-01

    To estimate the prevalence of visual impairment (VI) due to uncorrected refractive error (URE) and to assess the barriers to utilization of services in the adult urban population of Delhi. A population-based rapid assessment of VI was conducted among people aged 40 years and above in 24 randomly selected clusters of East Delhi district. Presenting visual acuity (PVA) was assessed in each eye using Snellen's "E" chart. Pinhole examination was done if PVA was refractive error were recorded with questionnaires. Of 2421 individuals enumerated, 2331 (96%) individuals were examined. Females were 50.7% among them. The mean age of all examined subjects was 51.32 ± 10.5 years (standard deviation). VI in either eye due to URE was present in 275 individuals (11.8%, 95% confidence interval [CI]: 10.5-13.1). URE was identified as the most common cause (53.4%) of VI. The overall prevalence of VI due to URE in the study population was 6.1% (95% CI: 5.1-7.0). The elder population as well as females were more likely to have VI due to URE (odds ratio [OR] = 12.3; P prevalence of VI due to URE among the urban adult population of Delhi is still high despite the availability of abundant eye care facilities. The majority of reported barriers are related to human behavior and attitude toward the refractive error. Understanding these aspects will help in planning appropriate strategies to eliminate VI due to URE.

  6. Systematic measurement errors involved in over-refraction using an autorefractor (Grand-Seiko WV-500): is measurement of accommodative lag through spectacle lenses valid?

    Science.gov (United States)

    Kimura, Shuhei; Hasebe, Satoshi; Ohtsuki, Hiroshi

    2007-05-01

    Lags of accommodation in ametropic children are often evaluated through spectacle lenses (over-refraction). This study investigated the validity of over-refraction when using an autorefractor. Using an autorefractor (Shin-Nippon SRW-500/Grand-Seiko WV-500), refractive readings were obtained in 25 cyclopleged eyes (mean +/- S.D. refraction: -3.44 +/- 3.56 D, range: from -10.56 to +0.25 D) while placing spherical lenses of different power (from -5.00 to +5.00 D) in front of the eye at a vertex distance of 12 mm. Based on the refractive readings with and without the lens, and the lens power, measurement errors were estimated. Similarly, the measurement errors were estimated also in model eyes of -10.00, -4.75, 0.00 and +10.00 D. The results were compared with ray-tracing simulations based on the internal specifications of the autorefractor. Measurement errors were found unless the power of the spectacle lens was equal to the refractive error of the eye. When the spectacle lens power was greater (less myopic or more hyperopic) than the refraction of the eye, the measurement error was negative in sign and greater than -0.3 D. It follows that, when an accommodative response is measured in myopic subjects, the refractive reading usually becomes more myopic than the refraction of the eye including the accommodative response; hence, the accommodative response is overestimated, and the lag of accommodation is underestimated. The autorefraction through spectacle lenses involved systematic measurement errors. The extent of the errors is usually small but needs to be taken into account in a comparative study of accommodative responses among different refractive groups.

  7. Refractive error, visual acuity and causes of vision loss in children in Shandong, China. The Shandong Children Eye Study.

    Science.gov (United States)

    Wu, Jian Feng; Bi, Hong Sheng; Wang, Shu Mei; Hu, Yuan Yuan; Wu, Hui; Sun, Wei; Lu, Tai Liang; Wang, Xing Rong; Jonas, Jost B

    2013-01-01

    To examine the prevalence of refractive errors and prevalence and causes of vision loss among preschool and school children in East China. Using a random cluster sampling in a cross-sectional school-based study design, children with an age of 4-18 years were selected from kindergartens, primary schools, and junior and senior high schools in the rural Guanxian County and the city of Weihai. All children underwent a complete ocular examination including measurement of uncorrected (UCVA) and best corrected visual acuity (BCVA) and auto-refractometry under cycloplegia. Myopia was defined as refractive error of ≤-0.5 diopters (D), high myopia as ≤ -6.0D, and amblyopia as BCVA ≤ 20/32 without any obvious reason for vision reduction and with strabismus or refractive errors as potential reasons. Out of 6364 eligible children, 6026 (94.7%) children participated. Prevalence of myopia (overall: 36.9 ± 0.6%;95% confidence interval (CI):36.0,38.0) increased (PPrevalence of high myopia (2.0 ± 0.2%) increased from 0.7 ± 0.3% (95%CI:0.1,1.3) in 10-years olds to 13.9 ± 3.0 (95%CI:7.8,19.9) in 17-years olds. It was associated with older age (OR:1.50;95%CI:1.41,1.60;Prefractive error (Prefractive error as cause in 1975 (32.9%) children. Amblyopia (BCVA ≤ 20/32) was detected in 44 (0.7%) children (11 children with bilateral amblyopia). In coastal East China, about 14% of the 17-years olds were highly myopic, and 80% were myopic. Prevalence of myopia increased with older age, female gender and urban region. About 0.7% of pre-school children and school children were amblyopic.

  8. Non-topography-guided PRK combined with CXL for the correction of refractive errors in patients with early stage keratoconus.

    Science.gov (United States)

    Fadlallah, Ali; Dirani, Ali; Chelala, Elias; Antonios, Rafic; Cherfan, George; Jarade, Elias

    2014-10-01

    To evaluate the safety and clinical outcome of combined non-topography-guided photorefractive keratectomy (PRK) and corneal collagen cross-linking (CXL) for the treatment of mild refractive errors in patients with early stage keratoconus. A retrospective, nonrandomized study of patients with early stage keratoconus (stage 1 or 2) who underwent simultaneous non-topography-guided PRK and CXL. All patients had at least 2 years of follow-up. Data were collected preoperatively and postoperatively at the 6-month, 1-year, and 2-year follow-up visit after combined non-topography-guided PRK and CXL. Seventy-nine patients (140 eyes) were included in the study. Combined non-topography-guided PRK and CXL induced a significant improvement in both visual acuity and refraction. Uncorrected distance visual acuity significantly improved from 0.39 ± 0.22 logMAR before combined non-topography-guided PRK and CXL to 0.12 ± 0.14 logMAR at the last follow-up visit (P topography-guided PRK and CXL (P topography-guided PRK and CXL is an effective and safe option for correcting mild refractive error and improving visual acuity in patients with early stable keratoconus. Copyright 2014, SLACK Incorporated.

  9. The prevalence of uncorrected refractive error in urban, suburban, exurban and rural primary school children in Indonesian population.

    Science.gov (United States)

    Mahayana, Indra Tri; Indrawati, Sagung Gede; Pawiroranu, Suhardjo

    2017-01-01

    Uncorrected refractive error (URE) is a major health problem among school children. This study was aimed to determine the frequency and patterns of URE across 4 gradients of residential densities (urban, exurban, suburban and rural). This was a cross-sectional study of school children from 3 districts in Yogyakarta and 1 district near Yogyakarta, Indonesia. The information regarding age, sex, school and school grader were recorded. The Snellen's chart was used to measure the visual acuity and to perform the subjective refraction. The district was then divided into urban, suburban, exurban and rural area based on their location and population. In total, 410 school children were included in the analyses (urban=79, exurban=73, suburban=160 and rural=98 school children). Urban school children revealed the worst visual acuity ( P refractive error across residential densities ( P =0.003). The risk of URE development in urban, suburban, exurban, and rural were 2.218 (95%CI: 0.914-5.385), 3.019 (95%CI: 1.266-7.197), 0.502 (95%CI: 0.195-1.293), and 0.130 (95%CI:0.017-0.972), respectively. Urban school children showed the worst visual acuity. The school children in urban and suburban residential area had 2 and 3 times higher risk of developing the URE.

  10. Prevalence and determinants of spectacle nonwear among rural Chinese secondary schoolchildren: the Xichang Pediatric Refractive Error Study Report 3.

    Science.gov (United States)

    Congdon, Nathan; Zheng, Mingwei; Sharma, Abhishek; Choi, Kai; Song, Yue; Zhang, Mingzhi; Wang, Mingfei; Zhou, Zhongxia; Li, Liping; Liu, Xueyu; Liu, Xiaojian; Lam, Dennis S C

    2008-12-01

    To study spectacle wear among rural Chinese children. Visual acuity, refraction, spectacle wear, and visual function were measured. Among 1892 subjects (84.7% of the sample), the mean (SD) age was 14.7 (0.8) years. Among 948 children (50.1%) potentially benefiting from spectacle wear, 368 (38.8%) did not own them. Among 580 children owning spectacles, 17.9% did not wear them at school. Among 476 children wearing spectacles, 25.0% had prescriptions that could not improve their visual acuity to better than 6/12. Therefore, 62.3% (591 of 948) of children needing spectacles did not benefit from appropriate correction. Children not owning and not wearing spectacles had better self-reported visual function but worse visual acuity at initial examination than children wearing spectacles and had a mean (SD) refractive error of -2.06 (1.15) diopter (D) and -2.78 (1.32) D, respectively. Girls (P children (P = .03) were more likely to be wearing their spectacles. A common reason for nonwear (17.0%) was the belief that spectacles weaken the eyes. Among children without spectacles, 79.3% said their families would pay for them (mean, US $15). Although half of the children could benefit from spectacle wear, 62.3% were not wearing appropriate correction. These children have significant uncorrected refractive errors. There is potential to support programs through spectacle sales.

  11. The KwaZulu-Natal Child Eye Care Programme: Delivering refractive error services to primary school learners

    Directory of Open Access Journals (Sweden)

    Y. I. Mahraj

    2011-12-01

    Full Text Available Globally, over 300 million people are estimated to be visually impaired. Uncorrected refractive error is the primary cause of almost half of all visual impairment, resulting in the global economy losing $269 billion in productivity annually. There is a definitive level of urgency in the treatment of refractive error in children as uncorrected refractive error results in the failure of normal visual maturation, termed amblyopia, which cannot be corrected in adult life. In South Africa, the lack of appropriatechild eye care strategies has posed a serious problem to the visual health of children. In 2006, the International Centre for Eye Care Education (ICEE conducted a situational analysis of child eye care services in the province of KwaZulu-Natal (KZN. The findings of this analysis indicated a dire need for comprehensive services in the province. Stakeholders (the KwaZulu-Natal Department of Healthand the KwaZulu-Natal Department of Education were advised on the value of a short-term strategy as the underpinning of a long-term sustainable approach. This resulted in the formation of a trialliance to implement the KZN Child Eye Care Programme. Eighty (80 individuals who were previously volunteers for the KZN Department of Health were trained in vision screening. These vi-sion screeners screened 239 606 primary school children from February 2007 to May 2008. Seven percent (15 944 of the children failed the vision screening and were referred for optometric assessments. Of the 15 944 children that failed the vision screening, 10 707 children were examined by optometrists and 1083 were found to have a refractive error and were therefore supplied with spectacles. The study indicates that a short-term programme to address a backlog of services can reach many underserved children. This programme identified many challenges of implementing a vision screening programme such as poor uptake of refractive services by learners in the absence of an appropriate

  12. Refractive errors survey in primary school children (6-12 year old) in 2 provinces: Bangkok and Nakhonpathom (one year result).

    Science.gov (United States)

    Yingyong, Penpimol

    2010-10-01

    Refractive error is an important cause of preventable visual impairment and blindness worldwide. Population-based studies will continue to be a key part in identification ofthe magnitude and the importance of this common eye disease. To assess the prevalence of the refractive error in primary school-aged children in Bangkok and Nakhonpathom together with the provision of the appropriately free of charge spectacles. A Population-based cross-sectional analytic study was conducted between October 2008 and September 2009. Random selection of geographically defined clusters was used to identify the study sample. The examination included visual acuity (VA) by Snellen chart and pinhole correction, autorefraction under cycloplegic refraction, ocular motility evaluation, examination of the external eye, anterior segment, media, and fundus. Ophthalmologists screened for ocular abnormalities. Among 2340 children, 1100 in Bangkok and 1240 in Nakhonpathom were examined The prevalence of refractive error in Bangkok and Nakhornpathom were 12.7% and 5.7% respectively. Refractive error was the cause in 97.6% of eyes with reduced vision, amblyopia in 0.5%, other causes in 0.8%, and unexplained causes in 1.1%. The present study showed a relative high prevalence of uncorrected refractive error in the central part of Thailand especially in Bangkok. Eye health education and screening is recommended to evaluate the need for refractive correction with appropriate prescription of spectacles.

  13. The KwaZulu-Natal Child Eye Care Programme: Delivering refractive error services to primary school learners

    Directory of Open Access Journals (Sweden)

    Y. I. Mahraj

    2011-12-01

    sion screeners screened 239 606 primary school children from February 2007 to May 2008. Seven percent (15 944 of the children failed the vision screening and were referred for optometric assessments. Of the 15 944 children that failed the vision screening, 10 707 children were examined by optometrists and 1083 were found to have a refractive error and were therefore supplied with spectacles. The study indicates that a short-term programme to address a backlog of services can reach many underserved children. This programme identified many challenges of implementing a vision screening programme such as poor uptake of refractive services by learners in the absence of an appropriate referral system and high attrition of trained vision screeners. (S Afr Optom 2011 70(2 61-68

  14. Assessing the accuracy and feasibility of a refractive error screening program conducted by school teachers in pre-primary and primary schools in Thailand.

    Science.gov (United States)

    Teerawattananon, Kanlaya; Myint, Chaw-Yin; Wongkittirux, Kwanjai; Teerawattananon, Yot; Chinkulkitnivat, Bunyong; Orprayoon, Surapong; Kusakul, Suwat; Tengtrisorn, Supaporn; Jenchitr, Watanee

    2014-01-01

    As part of the development of a system for the screening of refractive error in Thai children, this study describes the accuracy and feasibility of establishing a program conducted by teachers. To assess the accuracy and feasibility of screening by teachers. A cross-sectional descriptive and analytical study was conducted in 17 schools in four provinces representing four geographic regions in Thailand. A two-staged cluster sampling was employed to compare the detection rate of refractive error among eligible students between trained teachers and health professionals. Serial focus group discussions were held for teachers and parents in order to understand their attitude towards refractive error screening at schools and the potential success factors and barriers. The detection rate of refractive error screening by teachers among pre-primary school children is relatively low (21%) for mild visual impairment but higher for moderate visual impairment (44%). The detection rate for primary school children is high for both levels of visual impairment (52% for mild and 74% for moderate). The focus group discussions reveal that both teachers and parents would benefit from further education regarding refractive errors and that the vast majority of teachers are willing to conduct a school-based screening program. Refractive error screening by health professionals in pre-primary and primary school children is not currently implemented in Thailand due to resource limitations. However, evidence suggests that a refractive error screening program conducted in schools by teachers in the country is reasonable and feasible because the detection and treatment of refractive error in very young generations is important and the screening program can be implemented and conducted with relatively low costs.

  15. Assessing the accuracy and feasibility of a refractive error screening program conducted by school teachers in pre-primary and primary schools in Thailand.

    Directory of Open Access Journals (Sweden)

    Kanlaya Teerawattananon

    Full Text Available As part of the development of a system for the screening of refractive error in Thai children, this study describes the accuracy and feasibility of establishing a program conducted by teachers.To assess the accuracy and feasibility of screening by teachers.A cross-sectional descriptive and analytical study was conducted in 17 schools in four provinces representing four geographic regions in Thailand. A two-staged cluster sampling was employed to compare the detection rate of refractive error among eligible students between trained teachers and health professionals. Serial focus group discussions were held for teachers and parents in order to understand their attitude towards refractive error screening at schools and the potential success factors and barriers.The detection rate of refractive error screening by teachers among pre-primary school children is relatively low (21% for mild visual impairment but higher for moderate visual impairment (44%. The detection rate for primary school children is high for both levels of visual impairment (52% for mild and 74% for moderate. The focus group discussions reveal that both teachers and parents would benefit from further education regarding refractive errors and that the vast majority of teachers are willing to conduct a school-based screening program.Refractive error screening by health professionals in pre-primary and primary school children is not currently implemented in Thailand due to resource limitations. However, evidence suggests that a refractive error screening program conducted in schools by teachers in the country is reasonable and feasible because the detection and treatment of refractive error in very young generations is important and the screening program can be implemented and conducted with relatively low costs.

  16. The Articulatory Phonetics of /r/ for Residual Speech Errors.

    Science.gov (United States)

    Boyce, Suzanne E

    2015-11-01

    Effective treatment for children with residual speech errors (RSEs) requires in-depth knowledge of articulatory phonetics, but this level of detail may not be provided as part of typical clinical coursework. At a time when new imaging technologies such as ultrasound continue to inform our clinical understanding of speech disorders, incorporating contemporary work in the basic articulatory sciences into clinical training becomes especially important. This is particularly the case for the speech sound most likely to persist among children with RSEs-the North American English rhotic sound, /r/. The goal of this article is to review important information about articulatory phonetics as it affects children with RSE who present with /r/ production difficulties. The data presented are largely drawn from ultrasound and magnetic resonance imaging studies. This information will be placed in a clinical context by comparing productions of typical adult speakers to successful versus misarticulated productions of two children with persistent /r/ difficulties. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

  17. Common Mechanisms Underlying Refractive Error Identified in Functional Analysis of Gene Lists From Genome-Wide Association Study Results in 2 European British Cohorts

    Science.gov (United States)

    Hysi, Pirro G.; Mahroo, Omar A.; Cumberland, Phillippa; Wojciechowski, Robert; Williams, Katie M.; Young, Terri L.; Mackey, David A.; Rahi, Jugnoo S.; Hammond, Christopher J.

    2014-01-01

    IMPORTANCE To date, relatively few genes responsible for a fraction of heritability have been identified by means of large genetic association studies of refractive error. OBJECTIVE To explore the genetic mechanisms that lead to refractive error in the general population. DESIGN, SETTING, AND PARTICIPANTS Genome-wide association studies were carried out in 2 British population-based independent cohorts (N = 5928 participants) to identify genes moderately associated with refractive error. MAIN OUTCOMES AND MEASURES Enrichment analyses were used to identify sets of genes overrepresented in both cohorts. Enriched groups of genes were compared between both participating cohorts as a further measure against random noise. RESULTS Groups of genes enriched at highly significant statistical levels were remarkably consistent in both cohorts. In particular, these results indicated that plasma membrane (P = 7.64 × 10−30), cell-cell adhesion (P = 2.42 × 10−18), synaptic transmission (P = 2.70 × 10−14), calcium ion binding (P = 3.55 × 10−15), and cation channel activity (P = 2.77 × 10−14) were significantly overrepresented in relation to refractive error. CONCLUSIONS AND RELEVANCE These findings provide evidence that development of refractive error in the general population is related to the intensity of photosignal transduced from the retina, which may have implications for future interventions to minimize this disorder. Pathways connected to the procession of the nerve impulse are major mechanisms involved in the development of refractive error in populations of European origin. PMID:24264139

  18. Refractive errors in patients attending a private hospital in Jos, Nigeria

    African Journals Online (AJOL)

    The eye with the better presenting visual acuity was used for classifying the patient. The spherical equivalent refraction was used with the formula (sphere plus cylinder/2). Results: Two thousand eight hundred ninety eight patients were seen at the hospital for various eye problems. Six hundred one (20.7%) patients with ...

  19. The albino chick as a model for studying ocular developmental anomalies, including refractive errors, associated with albinism.

    Science.gov (United States)

    Rymer, Jodi; Choh, Vivian; Bharadwaj, Shrikant; Padmanabhan, Varuna; Modilevsky, Laura; Jovanovich, Elizabeth; Yeh, Brenda; Zhang, Zhan; Guan, Huanxian; Payne, W; Wildsoet, Christine F

    2007-10-01

    Albinism is associated with a variety of ocular anomalies including refractive errors. The purpose of this study was to investigate the ocular development of an albino chick line. The ocular development of both albino and normally pigmented chicks was monitored using retinoscopy to measure refractive errors and high frequency A-scan ultrasonography to measure axial ocular dimensions. Functional tests included an optokinetic nystagmus paradigm to assess visual acuity, and flash ERGs to assess retinal function. The underlying genetic abnormality was characterized using a gene microarray, PCR and a tyrosinase assay. The ultrastructure of the retinal pigment epithelium (RPE) was examined using transmission electron microscopy. PCR confirmed that the genetic abnormality in this line is a deletion in exon 1 of the tyrosinase gene. Tyrosinase gene expression in isolated RPE cells was minimally detectable, and there was minimal enzyme activity in albino feather bulbs. The albino chicks had pink eyes and their eyes transilluminated, reflecting the lack of melanin in all ocular tissues. All three main components, anterior chamber, crystalline lens and vitreous chamber, showed axial expansion over time in both normal and albino animals, but the anterior chambers of albino chicks were consistently shallower than those of normal chicks, while in contrast, their vitreous chambers were longer. Albino chicks remained relatively myopic, with higher astigmatism than the normally pigmented chicks, even though both groups underwent developmental emmetropization. Albino chicks had reduced visual acuity yet the ERG a- and b-wave components had larger amplitudes and shorter than normal implicit times. Developmental emmetropization occurs in the albino chick but is impaired, likely because of functional abnormalities in the RPE and/or retina as well as optical factors. In very young chicks the underlying genetic mutation may also contribute to refractive error and eye shape abnormalities.

  20. A comparative clinical survey of the prevalence of refractive errors and eye diseases in urban and rural school children.

    Science.gov (United States)

    Uzma, Nazia; Kumar, B Santhosh; Khaja Mohinuddin Salar, B M; Zafar, Mohammed Atheshm; Reddy, V Devender

    2009-06-01

    To assess the prevalence of refractive error and common ocular diseases in school-aged children in urban and rural populations in and around Hyderabad, India. Population-based, cross-sectional study. A total of 3314 school children, 1789 from urban areas and 1525 from rural areas. The examination included visual acuity measurements, retinoscopy and autorefraction under cycloplegia, examination of the anterior segment and external eye, and ocular motility evaluation. In the urban group the prevalence of uncorrected presenting and best-corrected visual impairment (prevalence of refractive error was greater (25.2%) in the urban than the rural group (8%). Myopia measured with autorefraction was observed in 51.4% of urban children and 16.7% in rural children. Increased literacy rate, duration of study hours, and older age of the child were found to have contributed more to the prevalence of myopia in the urban group. Hyperopia with autorefraction was found to be 3.3% in the urban and 3.1% in the rural group. Hyperopia was associated with younger age in the study group. Trachoma was the leading cause of ocular morbidity in the rural group (3.5%) compared with the urban group (0.16%). Night blindness was reported in 3.2% of children in the rural group and 0.33% in the urban group. Vitamin A deficiency, low socio-economic status, and poor personal and environmental hygienic practice were found to have a positive correlation with ocular morbidity among rural group children. Provision of health education, periodic visual screening programs, and primary eye care by trained health care personnel in the elementary schools will prevent the prevalence of refractive errors and common ocular diseases in school children.

  1. Visual impairment attributable to uncorrected refractive error and other causes in the Ghanaian youth: The University of Cape Coast Survey.

    Science.gov (United States)

    Abokyi, Samuel; Ilechie, Alex; Nsiah, Peter; Darko-Takyi, Charles; Abu, Emmanuel Kwasi; Osei-Akoto, Yaw Jnr; Youfegan-Baanam, Mathurin

    2016-01-01

    To determine the prevalence of visual impairment attributable to refractive error and other causes in a youthful Ghanaian population. A prospective survey of all consecutive visits by first-year tertiary students to the Optometry clinic between August, 2013 and April, 2014. Of the 4378 first-year students aged 16-39 years enumerated, 3437 (78.5%) underwent the eye examination. The examination protocol included presenting visual acuity (PVA), ocular motility, and slit-lamp examination of the external eye, anterior segment and media, and non-dilated fundus examination. Pinhole acuity and fundus examination were performed when the PVA≤6/12 in one or both eyes to determine the principal cause of the vision loss. The mean age of participants was 21.86 years (95% CI: 21.72-21.99). The prevalence of bilateral visual impairment (BVI; PVA in the better eye ≤6/12) and unilateral visual impairment UVI; PVA in the worse eye ≤6/12) were 3.08% (95% CI: 2.56-3.72) and 0.79% (95% CI: 0.54-1.14), respectively. Among 106 participants with BVI, refractive error (96.2%) and corneal opacity (3.8%) were the causes. Of the 27 participants with UVI, refractive error (44.4%), maculopathy (18.5%) and retinal disease (14.8%) were the major causes. There was unequal distribution of BVI in the different age groups, with those above 20 years having a lesser burden. Eye screening and provision of affordable spectacle correction to the youth could be timely to eliminate visual impairment. Copyright © 2014 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

  2. Prevalence and risk factors for refractive errors: Korean National Health and Nutrition Examination Survey 2008-2011.

    Directory of Open Access Journals (Sweden)

    Eun Chul Kim

    Full Text Available PURPOSE: To examine the prevalence and risk factors of refractive errors in a representative Korean population aged 20 years old or older. METHODS: A total of 23,392 people aged 20+ years were selected for the Korean National Health and Nutrition Survey 2008-2011, using stratified, multistage, clustered sampling. Refractive error was measured by autorefraction without cycloplegia, and interviews were performed regarding associated risk factors including gender, age, height, education level, parent's education level, economic status, light exposure time, and current smoking history. RESULTS: Of 23,392 participants, refractive errors were examined in 22,562 persons, including 21,356 subjects with phakic eyes. The overall prevalences of myopia ( 0.5 D were 48.1% (95% confidence interval [CI], 47.4-48.8, 4.0% (CI, 3.7-4.3, and 24.2% (CI, 23.6-24.8, respectively. The prevalence of myopia sharply decreased from 78.9% (CI, 77.4-80.4 in 20-29 year olds to 16.1% (CI, 14.9-17.3 in 60-69 year olds. In multivariable logistic regression analyses restricted to subjects aged 40+ years, myopia was associated with younger age (odds ratio [OR], 0.94; 95% Confidence Interval [CI], 0.93-0.94, p < 0.001, education level of university or higher (OR, 2.31; CI, 1.97-2.71, p < 0.001, and shorter sunlight exposure time (OR, 0.84; CI, 0.76-0.93, p = 0.002. CONCLUSIONS: This study provides the first representative population-based data on refractive error for Korean adults. The prevalence of myopia in Korean adults in 40+ years (34.7% was comparable to that in other Asian countries. These results show that the younger generations in Korea are much more myopic than previous generations, and that important factors associated with this increase are increased education levels and reduced sunlight exposures.

  3. Development of refractive error in individual children with regressed retinopathy of prematurity.

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    Wang, Jingyun; Ren, Xiaowei; Shen, Li; Yanni, Susan E; Leffler, Joel N; Birch, Eileen E

    2013-09-05

    We investigated longitudinally the refraction development in children with regressed retinopathy of prematurity (ROP), including those with and those without a history of peripheral retinal laser photocoagulation. Longitudinal (0-7 years) cycloplegic refraction data were collected prospectively for two groups of preterm children: severe ROP group included those with regressed ROP following bilateral panretinal laser photocoagulation (n = 37; median gestational age [GA] = 25.2; range, 22.7-27.9 weeks) and mild/no ROP group included those with spontaneously regressed ROP or no ROP (n = 27; median GA = 27.1; range, 23.1-32.0 weeks). Analyses were based on spherical equivalent (SEQ), anisometropia, astigmatism, and age (corrected for gestation). The prevalence, magnitude, and rate of myopic progression all were significantly higher in the severe ROP group than in the mild/no ROP group. Longitudinal SEQ in the severe ROP group were best fit with a bilinear model. Before 1.3 years old, the rate of myopic shift was -4.7 diopters (D)/y; after 1.3 years, the rate slowed to -0.15 D/y. Longitudinal SEQ in the mild/no ROP group was best fit with a linear model, with a rate of -0.004 D/y. Anisometropia in the severe ROP group increased approximately three times faster than in the mild/no ROP group. In the severe ROP group, with-the-rule astigmatism increased significantly with age. The severe ROP group progressed rapidly toward myopia, particularly during the first 1.3 years; anisometropia and astigmatism also increased with age. The mild/no ROP group showed little change in refraction. Infants treated with laser photocoagulation for severe ROP should be monitored with periodic cycloplegic refractions and provided with early optical correction.

  4. Corrective Lens Use and Refractive Error Among United States Air Force Aircrew

    Science.gov (United States)

    2010-03-01

    among-USAF aircrew based on eyeglass orders processed through the Spectacle-Request-Transmission-System (SRTS).- Currently, 41% of active duty USAF...contact lens fittings, laser eye protection , and cor- neal refractive surgery (CRS) procedures. The Aerospace Ophthalmology Branch of the USAF School of...based on eyeglass orders filled by the Department of Defense (DoD) Optical Fabrication Enterprise as reported in the Spectacle Request Transmission

  5. Age-Specific Prevalence of Visual Impairment and Refractive Error in Children Aged 3-10 Years in Shanghai, China.

    Science.gov (United States)

    Ma, Yingyan; Qu, Xiaomei; Zhu, Xiaofeng; Xu, Xun; Zhu, Jianfeng; Sankaridurg, Padmaja; Lin, Senlin; Lu, Lina; Zhao, Rong; Wang, Ling; Shi, Huijing; Tan, Hui; You, Xiaofang; Yuan, Hong; Sun, Sifei; Wang, Mingjin; He, Xiangui; Zou, Haidong; Congdon, Nathan

    2016-11-01

    We assessed changes in age-specific prevalence of refractive error at the time of starting school, by comparing preschool and school age cohorts in Shanghai, China. A cross-sectional study was done in Jiading District, Shanghai during November and December 2013. We randomly selected 7 kindergartens and 7 primary schools, with probability proportionate to size. Chinese children (n = 8398) aged 3 to 10 years were enumerated, and 8267 (98.4%) were included. Children underwent distance visual acuity assessment and refraction measurement by cycloplegic autorefraction and subjective refraction. The prevalence of uncorrected visual acuity (UCVA), presenting visual acuity, and best-corrected visual acuity in the better eye of ≤20/40 was 19.8%, 15.5%, and 1.7%, respectively. Among those with UCVA ≤ 20/40, 93.2% could achieve visual acuity of ≥20/32 with refraction. Only 28.7% (n = 465) of children with UCVA in the better eye of ≤20/40 wore glasses. Prevalence of myopia (spherical equivalent ≤-0.5 diopters [D] in at least one eye) increased from 1.78% in 3-year-olds to 52.2% in 10-year-olds, while prevalence of hyperopia (spherical equivalent ≥+2.0 D) decreased from 17.8% among 3-year-olds to 2.6% by 10 years of age. After adjusting for age, attending elite "high-level" school was statistically associated with greater myopia prevalence. The prevalence of myopia was lower or comparable to that reported in other populations from age 3 to 5 years, but increased dramatically after 6 years, consistent with a strong environmental role of schooling on myopia development.

  6. The prevalence of uncorrected refractive error in urban, suburban, exurban and rural primary school children in Indonesian population

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    Indra Tri Mahayana

    2017-11-01

    Full Text Available Uncorrected refractive error (URE is a major health problem among school children. This study was aimed to determine the frequency and patterns of URE across 4 gradients of residential densities (urban, exurban, suburban and rural. This was a cross-sectional study of school children from 3 districts in Yogyakarta and 1 district near Yogyakarta, Indonesia. The information regarding age, sex, school and school grader were recorded. The Snellen’s chart was used to measure the visual acuity and to perform the subjective refraction. The district was then divided into urban, suburban, exurban and rural area based on their location and population. In total, 410 school children were included in the analyses (urban=79, exurban=73, suburban=160 and rural=98 school children. Urban school children revealed the worst visual acuity (P<0.001 and it was significant when compared with exurban and rural. The proportion of URE among urban, suburban, exurban and rural area were 10.1%, 12.3%, 3.8%, and 1%, respectively, and it was significant when compared to the proportion of ametropia and corrected refractive error across residential densities (P=0.003. The risk of URE development in urban, suburban, exurban, and rural were 2.218 (95%CI: 0.914-5.385, 3.019 (95%CI: 1.266-7.197, 0.502 (95%CI: 0.195-1.293, and 0.130 (95%CI:0.017-0.972, respectively. Urban school children showed the worst visual acuity. The school children in urban and suburban residential area had 2 and 3 times higher risk of developing the URE.

  7. The contributions of near work and outdoor activity to the correlation between siblings in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study.

    Science.gov (United States)

    Jones-Jordan, Lisa A; Sinnott, Loraine T; Graham, Nicholas D; Cotter, Susan A; Kleinstein, Robert N; Manny, Ruth E; Mutti, Donald O; Twelker, J Daniel; Zadnik, Karla

    2014-09-09

    We determined the correlation between sibling refractive errors adjusted for shared and unique environmental factors using data from the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study. Refractive error from subjects' last study visits was used to estimate the intraclass correlation coefficient (ICC) between siblings. The correlation models used environmental factors (diopter-hours and outdoor/sports activity) assessed annually from parents by survey to adjust for shared and unique environmental exposures when estimating the heritability of refractive error (2*ICC). Data from 700 families contributed to the between-sibling correlation for spherical equivalent refractive error. The mean age of the children at the last visit was 13.3 ± 0.90 years. Siblings engaged in similar amounts of near and outdoor activities (correlations ranged from 0.40-0.76). The ICC for spherical equivalent, controlling for age, sex, ethnicity, and site was 0.367 (95% confidence interval [CI] = 0.304, 0.420), with an estimated heritability of no more than 0.733. After controlling for these variables, and near and outdoor/sports activities, the resulting ICC was 0.364 (95% CI = 0.304, 0.420; estimated heritability no more than 0.728, 95% CI = 0.608, 0.850). The ICCs did not differ significantly between male-female and single sex pairs. Adjusting for shared family and unique, child-specific environmental factors only reduced the estimate of refractive error correlation between siblings by 0.5%. Consistent with a lack of association between myopia progression and either near work or outdoor/sports activity, substantial common environmental exposures had little effect on this correlation. Genetic effects appear to have the major role in determining the similarity of refractive error between siblings. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

  8. Refractive error, visual acuity and causes of vision loss in children in Shandong, China. The Shandong Children Eye Study.

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    Jian Feng Wu

    Full Text Available PURPOSE: To examine the prevalence of refractive errors and prevalence and causes of vision loss among preschool and school children in East China. METHODS: Using a random cluster sampling in a cross-sectional school-based study design, children with an age of 4-18 years were selected from kindergartens, primary schools, and junior and senior high schools in the rural Guanxian County and the city of Weihai. All children underwent a complete ocular examination including measurement of uncorrected (UCVA and best corrected visual acuity (BCVA and auto-refractometry under cycloplegia. Myopia was defined as refractive error of ≤-0.5 diopters (D, high myopia as ≤ -6.0D, and amblyopia as BCVA ≤ 20/32 without any obvious reason for vision reduction and with strabismus or refractive errors as potential reasons. RESULTS: Out of 6364 eligible children, 6026 (94.7% children participated. Prevalence of myopia (overall: 36.9 ± 0.6%;95% confidence interval (CI:36.0,38.0 increased (P<0.001 from 1.7 ± 1.2% (95%CI:0.0,4.0 in the 4-years olds to 84.6 ± 3.2% (95%CI:78.0,91.0 in 17-years olds. Myopia was associated with older age (OR:1.56;95%CI:1.52,1.60;P<0.001, female gender (OR:1.22;95%CI:1.08,1.39;P = 0.002 and urban region (OR:2.88;95%CI:2.53,3.29;P<0.001. Prevalence of high myopia (2.0 ± 0.2% increased from 0.7 ± 0.3% (95%CI:0.1,1.3 in 10-years olds to 13.9 ± 3.0 (95%CI:7.8,19.9 in 17-years olds. It was associated with older age (OR:1.50;95%CI:1.41,1.60;P<0.001 and urban region (OR:3.11;95%CI:2.08,4.66;P<0.001. Astigmatism (≥ 0.75D (36.3 ± 0.6%;95%CI:35.0,38.0 was associated with older age (P<0.001;OR:1.06;95%CI:1.04,1.09, more myopic refractive error (P<0.001;OR:0.94;95%CI:0.91,0.97 and urban region (P<0.001;OR:1.47;95%CI:1.31,1.64. BCVA was ≤ 20/40 in the better eye in 19 (0.32% children. UCVA ≤ 20/40 in at least one eye was found in 2046 (34.05% children, with undercorrected refractive error as cause in 1975 (32.9% children. Amblyopia

  9. Reducing visual deficits caused by refractive errors in school and preschool children: results of a pilot school program in the Andean region of Apurimac, Peru.

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    Latorre-Arteaga, Sergio; Gil-González, Diana; Enciso, Olga; Phelan, Aoife; García-Muñoz, Angel; Kohler, Johannes

    2014-01-01

    Refractive error is defined as the inability of the eye to bring parallel rays of light into focus on the retina, resulting in nearsightedness (myopia), farsightedness (Hyperopia) or astigmatism. Uncorrected refractive error in children is associated with increased morbidity and reduced educational opportunities. Vision screening (VS) is a method for identifying children with visual impairment or eye conditions likely to lead to visual impairment. To analyze the utility of vision screening conducted by teachers and to contribute to a better estimation of the prevalence of childhood refractive errors in Apurimac, Peru. Design : A pilot vision screening program in preschool (Group I) and elementary school children (Group II) was conducted with the participation of 26 trained teachers. Children whose visual acuity wasrefractive error were calculated against clinical examination. Program assessment with participants was conducted to evaluate outcomes and procedures. A total sample of 364 children aged 3-11 were screened; 45 children were examined at Centro Oftalmológico Monseñor Enrique Pelach (COMEP) Eye Hospital. Prevalence of refractive error was 6.2% (Group I) and 6.9% (Group II); specificity of teacher vision screening was 95.8% and 93.0%, while positive predictive value was 59.1% and 47.8% for each group, respectively. Aspects highlighted to improve the program included extending training, increasing parental involvement, and helping referred children to attend the hospital. Prevalence of refractive error in children is significant in the region. Vision screening performed by trained teachers is a valid intervention for early detection of refractive error, including screening of preschool children. Program sustainability and improvements in education and quality of life resulting from childhood vision screening require further research.

  10. Cost-effectiveness of screening and correcting refractive errors in school children in Africa, Asia, America and Europe.

    Science.gov (United States)

    Baltussen, Rob; Naus, Jeroen; Limburg, Hans

    2009-02-01

    To estimate the costs and effects of alternative strategies for annual screening of school children for refractive errors, and the provision of spectacles, in different WHO sub-regions in Africa, Asia, America and Europe. We developed a mathematical simulation model for uncorrected refractive error, using prevailing prevalence and incidence rates. Remission rates reflected the absence or presence of screening strategies for school children. All screening strategies were implemented for a period of 10 years and were compared to a situation were no screening was implemented. Outcome measures were life years adjusted for disability (DALYs), costs of screening and provision of spectacles and follow-up for six different screening strategies, and cost-effectiveness in international dollars per DALY averted. Epidemiological information was derived from the burden of disease study from the World Health Organization (WHO). Cost data were derived from large databases from the WHO. Both univariate and multivariate sensitivity analyses were performed on key parameters to determine the robustness of the model results. In all regions, screening of 5-15 years old children yields most health effects, followed by screening of 11-15 years old, 5-10 years old, and screening of 8 and 13 years old. Screening of broad-age intervals is always more costly than screening of single-age intervals, and there are important economies of scale for simultaneous screening of both 5-10 and 11-15-year-old children. In all regions, screening of 11-15 years old is the most cost-effective intervention, with the cost per DALY averted ranging from I$67 per DALY averted in the Asian sub-region to I$458 per DALY averted in the European sub-region. The incremental cost per DALY averted of screening 5-15 years old ranges between I$111 in the Asian sub-region to I$672 in the European sub-region. Considering the conservative study assumptions and the robustness of study conclusions towards changes in these

  11. Prevalence and associations of refractive error in indigenous Australians within central Australia: the Central Australian Ocular Health Study.

    Science.gov (United States)

    Landers, John; Henderson, Tim; Craig, Jamie

    2010-05-01

    To determine the prevalence and associations of refractive error within the indigenous Australian population living in central Australia. 1884 individuals aged 20 years or older, living in one of 30 remote communities within the statistical local area of 'central Australia' were recruited for this study. This equated to 36% of those aged 20 years or older and 67% of those aged 40 years or older within this district. Participants were recruited as they presented to the eye clinic at each remote community. Participants underwent subjective refraction to determine spherical equivalent and then had a slit-lamp anterior segment examination. Participants were only included if they were phakic and only the right eye was considered. The prevalence of hypermetropia worse than +1.0 dioptres (D), myopia worse than -0.5 D and astigmatism worse than 1.0 D is presented. From those recruited, 15.2% were hypermetropic; 11.1% were myopic; and 6.2% had astigmatism. Participants became progressively more hypermetropic with increasing age until the age of 70 years, after which time they become more myopic. Furthermore, there was an increasing likelihood of myopia and a decreasing likelihood of hypermetropia with increasing nuclear opalescent cataract. Our study has shown that indigenous Australians are less likely to be ametropic compared with non-indigenous groups. Variations with age and nuclear opalescent cataract seen in other previous work have also been observed in our sample.

  12. Differences in prevalence of refractive errors in young Asian males in Singapore between 1996-1997 and 2009-2010.

    Science.gov (United States)

    Koh, Victor; Yang, Adeline; Saw, Seang Mei; Chan, Yiong Huak; Lin, Sheng Tong; Tan, Mellisa Mei Hui; Tey, Frederick; Nah, Gerard; Ikram, M Kamran

    2014-08-01

    To determine the differences in prevalence rates of refractive errors in young Singaporean males over a 13-year period between 1996-1997 and 2009-2010 METHODS: Non-cycloplegic autorefraction data were obtained in a survey of 15,085 young male subjects (mean age 19.5 ± 1.4 years, range 16-25 years) in 1996-1997 using a Nikon NRK-8000 autorefractor. A second survey of 28,908 male subjects (mean age 19.8 ± 1.2 years, range 17-29 years) was conducted in 2009-2010 using a Huvitz MRK-3100 autorefractor. The overall prevalence of myopia (spherical equivalent, SEq, worse than -0.5 diopters, D) was similar in 2009-2010 (81.6%) and 1996-1997 (79.2%; odds ratio 1.38, 95% confidence interval 1.31-1.46; p prevalence of high myopia (SEq worse than -6.0D) increased from 13.1% in 1996-1997 to 14.7% in 2009-2010 (p prevalence of refractive astigmatism increased significantly from 41.4% in 1996-1997 to 50.9% in 2009-2010 (p prevalence of myopia and high myopia remained high and the prevalence of astigmatism increased in young male adults in Singapore over a 13-year period after controlling for age, education and ethnicity.

  13. Comparing sports vision among three groups of soft tennis adolescent athletes: Normal vision, refractive errors with and without correction

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    Shih-Tsun Chang

    2015-01-01

    Full Text Available Background: The effect of correcting static vision on sports vision is still not clear. Aim: To examine whether sports vision (depth perception [DP], dynamic visual acuity [DVA], eye movement [EM], peripheral vision [PV], and momentary vision [MV], were different among soft tennis adolescent athletes with normal vision (Group A, with refractive error and corrected with (Group B and without eyeglasses (Group C. Setting and Design: A cross-section study was conducted. Soft tennis athletes aged 10–13 who played softball tennis for 2–5 years, and who were without any ocular diseases and without visual training for the past 3 months were recruited. Materials and Methods: DPs were measured in an absolute deviation (mm between a moving rod and fixing rod (approaching at 25 mm/s, receding at 25 mm/s, approaching at 50 mm/s, receding at 50 mm/s using electric DP tester. A smaller deviation represented better DP. DVA, EM, PV, and MV were measured on a scale from 1 (worse to 10 (best using ATHLEVISION software. Statistical Analysis: Chi-square test and Kruskal–Wallis test was used to compare the data among the three study groups. Results: A total of 73 athletes (37 in Group A, 8 in Group B, 28 in Group C were enrolled in this study. All four items of DP showed significant difference among the three study groups (P = 0.0051, 0.0004, 0.0095, 0.0021. PV displayed significant difference among the three study groups (P = 0.0044. There was no significant difference in DVA, EM, and MV among the three study groups. Conclusions: Significant better DP and PV were seen among soft tennis adolescent athletes with normal vision than those with refractive error regardless whether they had eyeglasses corrected. On the other hand, DVA, EM, and MV were similar among the three study groups.

  14. Visual Impairment, Undercorrected Refractive Errors, and Activity Limitations in Older Adults: Findings From the Three-City Alienor Study.

    Science.gov (United States)

    Naël, Virginie; Pérès, Karine; Carrière, Isabelle; Daien, Vincent; Scherlen, Anne-Catherine; Arleo, Angelo; Korobelnik, Jean-Francois; Delcourt, Cécile; Helmer, Catherine

    2017-04-01

    As vision is required in almost all activities of daily living, visual impairment (VI) may be one of the major treatable factors for preventing activity limitations. We aimed to evaluate the attributable risk of VI associated with activity limitations and the extent to which limitations are avoidable with optimal optical correction of undercorrected refractive errors. We analyzed 709 older adults from the Three-City-Alienor population-based study. VI was defined by presenting distance visual acuity in the better-seeing eye. Multivariate modified Poisson regressions were used to estimate the associations between vision, activity limitations, and social participation restrictions. Population attributable risk (PAR) and generalized impact fraction (GIF) were estimated. Bootstrapping was used to estimate 95% confidence intervals (CI). After adjustment for potential confounders, VI was associated with each domain of activity limitations, except basic activities of daily living (ADL) limitations. These associations were found for even minimal levels of VI. PAR was estimated at 10.1% (95% CI: 5.2-10.6) for mobility limitations, at 26.0% (95% CI: 13.5-41.2) for instrumental ADL (IADL) limitations, and at 24.9% (95% CI: 10.5-47.1) for social participation restrictions. GIF for improvement of undercorrected refractive errors was 6.1% (95% CI: 3.8-8.5) for mobility limitations, 15.8% (95% CI: 11.5-20.1) for IADL limitations and 21.4% (95% CI: 13.8-28.5) for social participation restrictions. About one-sixth of IADL limitations and one-fifth of social participation restrictions could be prevented by an optimal optical correction. These results underline the importance of eye examinations in older adults to prevent disability.

  15. The influence of refractive error and lattice degeneration on the incidence of retinal detachment.

    Science.gov (United States)

    Burton, T C

    1989-01-01

    This study indicates the feasibility of stratifying the general population into various risk pools for retinal detachment depending on a person's age, refractive status, and the presence of lattice degeneration. At first impression the risks seem at variance with the fine clinical studies of Byer, who has shown a very low detachment rate in the population with lattice degeneration. In all likelihood the vast majority of his patients were emmetropic or mildly myopic, so that very few would be expected to develop detachments during their entire lifetimes, let along during intervals of only 10 to 20 years. This study shows the futility of following, or treating prophylactically, young emmetropic individuals with lattice degeneration. Assuming that prophylaxis is actually effective, one would have to treat 1000 emmetropic lattice patients in the 30 to 39 year age group to prevent a single detachment over a 10-year period. Lattice patients with low to moderate degrees of myopia tend to develop detachments between 40 and 60 years of age caused by premature posterior vitreous separation and tractional tears. Clearly prophylaxis for this group is not warranted, since only 5% to 10% of these individuals will experience detachments in their lifetimes. On the other hand this study has verified the previous suspicions that persons with myopia exceeding -5.0 D accompanied by lattice degeneration have an extraordinarily high risk of detachment during their lifetimes. Detachments in this group tend to cluster in the second, third, and fourth decades, are typically caused by atrophic holes, are slowly progressive, and are often simultaneously bilateral. Enhanced vigilance is certainly appropriate during this time and perhaps consideration should be given to prophylactically treating this group. This would be no small task, since within a population of 1 million persons there would be about 1150 aged 10 to 39 years with myopia exceeding -5.0 D and lattice degeneration. Only 4

  16. High prevalence of refractive errors in a rural population: 'Nooravaran Salamat' Mobile Eye Clinic experience.

    Science.gov (United States)

    Hashemi, Hassan; Rezvan, Farhad; Ostadimoghaddam, Hadi; Abdollahi, Majid; Hashemi, Maryam; Khabazkhoob, Mehdi

    2013-01-01

    The prevalence of myopia and hyperopia and determinants were determined in a rural population of Iran. Population-based cross-sectional study. Using random cluster sampling, 13 of the 83 villages of Khaf County in the north east of Iran were selected. Data from 2001 people over the age of 15 years were analysed. Visual acuity measurement, non-cycloplegic refraction and eye examinations were done at the Mobile Eye Clinic. The prevalence of myopia and hyperopia based on spherical equivalent worse than -0.5 dioptre and +0.5 dioptre, respectively. The prevalence of myopia, hyperopia and anisometropia in the total study sample was 28% (95% confidence interval: 25.9-30.2), 19.2% (95% confidence interval: 17.3-21.1), and 11.5% (95% confidence interval: 10.0-13.1), respectively. In the over 40 population, the prevalence of myopia and hyperopia was 32.5% (95% confidence interval: 28.9-36.1) and 27.9% (95% confidence interval: 24.5-31.3), respectively. In the multiple regression model for this group, myopia strongly correlated with cataract (odds ratio = 1.98 and 95% confidence interval: 1.33-2.93), and hyperopia only correlated with age (P < 0.001). The prevalence of high myopia and high hyperopia was 1.5% and 4.6%. In the multiple regression model, anisometropia significantly correlated with age (odds ratio = 1.04) and cataract (odds ratio = 5.2) (P < 0.001). The prevalence of myopia and anisometropia was higher than that in previous studies in urban population of Iran, especially in the elderly. Cataract was the only variable that correlated with myopia and anisometropia. © 2013 The Authors. Clinical and Experimental Ophthalmology © 2013 Royal Australian and New Zealand College of Ophthalmologists.

  17. Error Budget for a Calibration Demonstration System for the Reflected Solar Instrument for the Climate Absolute Radiance and Refractivity Observatory

    Science.gov (United States)

    Thome, Kurtis; McCorkel, Joel; McAndrew, Brendan

    2013-01-01

    A goal of the Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission is to observe highaccuracy, long-term climate change trends over decadal time scales. The key to such a goal is to improving the accuracy of SI traceable absolute calibration across infrared and reflected solar wavelengths allowing climate change to be separated from the limit of natural variability. The advances required to reach on-orbit absolute accuracy to allow climate change observations to survive data gaps exist at NIST in the laboratory, but still need demonstration that the advances can move successfully from to NASA and/or instrument vendor capabilities for spaceborne instruments. The current work describes the radiometric calibration error budget for the Solar, Lunar for Absolute Reflectance Imaging Spectroradiometer (SOLARIS) which is the calibration demonstration system (CDS) for the reflected solar portion of CLARREO. The goal of the CDS is to allow the testing and evaluation of calibration approaches, alternate design and/or implementation approaches and components for the CLARREO mission. SOLARIS also provides a test-bed for detector technologies, non-linearity determination and uncertainties, and application of future technology developments and suggested spacecraft instrument design modifications. The resulting SI-traceable error budget for reflectance retrieval using solar irradiance as a reference and methods for laboratory-based, absolute calibration suitable for climatequality data collections is given. Key components in the error budget are geometry differences between the solar and earth views, knowledge of attenuator behavior when viewing the sun, and sensor behavior such as detector linearity and noise behavior. Methods for demonstrating this error budget are also presented.

  18. A method to evaluate residual phase error for polar formatted synthetic aperture radar systems

    Science.gov (United States)

    Musgrove, Cameron; Naething, Richard

    2013-05-01

    Synthetic aperture radar systems that use the polar format algorithm are subject to a focused scene size limit inherent to the polar format algorithm. The classic focused scene size limit is determined from the dominant residual range phase error term. Given the many sources of phase error in a synthetic aperture radar, a system designer is interested in how much phase error results from the assumptions made with the polar format algorithm. Autofocus algorithms have limits to the amount and type of phase error that can be corrected. Current methods correct only one or a few terms of the residual phase error. A system designer needs to be able to evaluate the contribution of the residual or uncorrected phase error terms to determine the new focused scene size limit. This paper describes a method to estimate the complete residual phase error, not just one or a few of the dominant residual terms. This method is demonstrated with polar format image formation, but is equally applicable to other image formation algorithms. A benefit for the system designer is that additional correction terms can be added or deleted from the analysis as necessary to evaluate the resulting effect upon image quality.

  19. Pencil kernel correction and residual error estimation for quality-index-based dose calculations

    International Nuclear Information System (INIS)

    Nyholm, Tufve; Olofsson, Joergen; Ahnesjoe, Anders; Georg, Dietmar; Karlsson, Mikael

    2006-01-01

    Experimental data from 593 photon beams were used to quantify the errors in dose calculations using a previously published pencil kernel model. A correction of the kernel was derived in order to remove the observed systematic errors. The remaining residual error for individual beams was modelled through uncertainty associated with the kernel model. The methods were tested against an independent set of measurements. No significant systematic error was observed in the calculations using the derived correction of the kernel and the remaining random errors were found to be adequately predicted by the proposed method

  20. Reducing visual deficits caused by refractive errors in school and preschool children: results of a pilot school program in the Andean region of Apurimac, Peru

    Directory of Open Access Journals (Sweden)

    Sergio Latorre-Arteaga

    2014-02-01

    Full Text Available Background: Refractive error is defined as the inability of the eye to bring parallel rays of light into focus on the retina, resulting in nearsightedness (myopia, farsightedness (Hyperopia or astigmatism. Uncorrected refractive error in children is associated with increased morbidity and reduced educational opportunities. Vision screening (VS is a method for identifying children with visual impairment or eye conditions likely to lead to visual impairment. Objective: To analyze the utility of vision screening conducted by teachers and to contribute to a better estimation of the prevalence of childhood refractive errors in Apurimac, Peru. Design: A pilot vision screening program in preschool (Group I and elementary school children (Group II was conducted with the participation of 26 trained teachers. Children whose visual acuity was<6/9 [20/30] (Group I and≤6/9 (Group II in one or both eyes, measured with the Snellen Tumbling E chart at 6 m, were referred for a comprehensive eye exam. Specificity and positive predictive value to detect refractive error were calculated against clinical examination. Program assessment with participants was conducted to evaluate outcomes and procedures. Results: A total sample of 364 children aged 3–11 were screened; 45 children were examined at Centro Oftalmológico Monseñor Enrique Pelach (COMEP Eye Hospital. Prevalence of refractive error was 6.2% (Group I and 6.9% (Group II; specificity of teacher vision screening was 95.8% and 93.0%, while positive predictive value was 59.1% and 47.8% for each group, respectively. Aspects highlighted to improve the program included extending training, increasing parental involvement, and helping referred children to attend the hospital. Conclusion: Prevalence of refractive error in children is significant in the region. Vision screening performed by trained teachers is a valid intervention for early detection of refractive error, including screening of preschool children

  1. Residual-based a posteriori error estimation for multipoint flux mixed finite element methods

    KAUST Repository

    Du, Shaohong

    2015-10-26

    A novel residual-type a posteriori error analysis technique is developed for multipoint flux mixed finite element methods for flow in porous media in two or three space dimensions. The derived a posteriori error estimator for the velocity and pressure error in L-norm consists of discretization and quadrature indicators, and is shown to be reliable and efficient. The main tools of analysis are a locally postprocessed approximation to the pressure solution of an auxiliary problem and a quadrature error estimate. Numerical experiments are presented to illustrate the competitive behavior of the estimator.

  2. Ametropia, retinal anatomy, and OCT abnormality patterns in glaucoma. 1. Impacts of refractive error and interartery angle.

    Science.gov (United States)

    Elze, Tobias; Baniasadi, Neda; Jin, Qingying; Wang, Hui; Wang, Mengyu

    2017-12-01

    Retinal nerve fiber layer thickness (RNFLT) measured by optical coherence tomography (OCT) is widely used in clinical practice to support glaucoma diagnosis. Clinicians frequently interpret peripapillary RNFLT areas marked as abnormal by OCT machines. However, presently, clinical OCT machines do not take individual retinal anatomy variation into account, and according diagnostic biases have been shown particularly for patients with ametropia. The angle between the two major temporal retinal arteries (interartery angle, IAA) is considered a fundamental retinal ametropia marker. Here, we analyze peripapillary spectral domain OCT RNFLT scans of 691 glaucoma patients and apply multivariate logistic regression to quantitatively compare the diagnostic bias of spherical equivalent (SE) of refractive error and IAA and to identify the precise retinal locations of false-positive/negative abnormality marks. Independent of glaucoma severity (visual field mean deviation), IAA/SE variations biased abnormality marks on OCT RNFLT printouts at 36.7%/22.9% of the peripapillary area, respectively. 17.2% of the biases due to SE are not explained by IAA variation, particularly in inferonasal areas. To conclude, the inclusion of SE and IAA in OCT RNFLT norms would help to increase diagnostic accuracy. Our detailed location maps may help clinicians to reduce diagnostic bias while interpreting retinal OCT scans. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

  3. Ametropia, retinal anatomy, and OCT abnormality patterns in glaucoma. 1. Impacts of refractive error and interartery angle

    Science.gov (United States)

    Elze, Tobias; Baniasadi, Neda; Jin, Qingying; Wang, Hui; Wang, Mengyu

    2017-12-01

    Retinal nerve fiber layer thickness (RNFLT) measured by optical coherence tomography (OCT) is widely used in clinical practice to support glaucoma diagnosis. Clinicians frequently interpret peripapillary RNFLT areas marked as abnormal by OCT machines. However, presently, clinical OCT machines do not take individual retinal anatomy variation into account, and according diagnostic biases have been shown particularly for patients with ametropia. The angle between the two major temporal retinal arteries (interartery angle, IAA) is considered a fundamental retinal ametropia marker. Here, we analyze peripapillary spectral domain OCT RNFLT scans of 691 glaucoma patients and apply multivariate logistic regression to quantitatively compare the diagnostic bias of spherical equivalent (SE) of refractive error and IAA and to identify the precise retinal locations of false-positive/negative abnormality marks. Independent of glaucoma severity (visual field mean deviation), IAA/SE variations biased abnormality marks on OCT RNFLT printouts at 36.7%/22.9% of the peripapillary area, respectively. 17.2% of the biases due to SE are not explained by IAA variation, particularly in inferonasal areas. To conclude, the inclusion of SE and IAA in OCT RNFLT norms would help to increase diagnostic accuracy. Our detailed location maps may help clinicians to reduce diagnostic bias while interpreting retinal OCT scans.

  4. A Refined Algorithm On The Estimation Of Residual Motion Errors In Airborne SAR Images

    Science.gov (United States)

    Zhong, Xuelian; Xiang, Maosheng; Yue, Huanyin; Guo, Huadong

    2010-10-01

    Due to the lack of accuracy in the navigation system, residual motion errors (RMEs) frequently appear in the airborne SAR image. For very high resolution SAR imaging and repeat-pass SAR interferometry, the residual motion errors must be estimated and compensated. We have proposed a new algorithm before to estimate the residual motion errors for an individual SAR image. It exploits point-like targets distributed along the azimuth direction, and not only corrects the phase, but also improves the azimuth focusing. But the required point targets are selected by hand, which is time- and labor-consuming. In addition, the algorithm is sensitive to noises. In this paper, a refined algorithm is proposed aiming at these two shortcomings. With real X-band airborne SAR data, the feasibility and accuracy of the refined algorithm are demonstrated.

  5. Refractive errors in premature infants with retinopathy of prematurity after anti-vascular endothelial growth factor (anti-VEGF therapy

    Directory of Open Access Journals (Sweden)

    Vujanović Milena S.

    2017-01-01

    Full Text Available Background/Aim. Retinopathy of prematurity (ROP is a vasoproliferative retinopathy which affects the blood vessels of the retina during its development. The aim of this study was to evaluate the incidence and the degree of refractive errors in premature infants with severe ROP treated with antivascular endothelial growth factor (anti-VEGF (bevacizumab. Methods. This prospective study included 21 patients (42 eyes nine months old who received intravitreal injection of anti-VEGF therapy. The control group consisted of 45 patients (90 eyes who were subjected to laser treatment. In cycloplegia each patient underwent retinoscopy, keratorefractometry, and A-scan ultrasonography. Results. Myopia was present in 47.62% of the eyes in the study group and in 33.33% of the eyes in the control group, but there were no statistically significant differences between these groups. Seven (16.67% eyes in the study group and 17 (18.89% eyes in the control group were discovered to have high myopia (SE– spherical equivalents < -3.0 D – dioptre. Clinically significant hypermetropia was higher in the study group (47.62% than in the control group (34.44%, but with no statistically significant difference. In addition, high hypermetropia was significantly greater in the control group (15.56% than in the study group (11.90% (p < 0.001. Astigmatism was more common in the control group than in the study group (81.11% vs 71.43%, respectively, especially high astigmatism (56% vs 43%, respectively. Also the more common form of astigmatism was with the rule (WTR both in the study and the control group (42.86% vs 55.56%, respectively. Anisometropia was significantly greater in the control group (24.44% than in the study group (9.52% (p < 0.05. The children from the study group had significantly greater lens thickness, and a shorter anterior chamber depth than children from the control group (p < 0.01. There was no significant difference in the axial length of the eye between

  6. Dosimetric Implications of Residual Tracking Errors During Robotic SBRT of Liver Metastases

    International Nuclear Information System (INIS)

    Chan, Mark; Grehn, Melanie; Cremers, Florian; Siebert, Frank-Andre; Wurster, Stefan; Huttenlocher, Stefan; Dunst, Jürgen; Hildebrandt, Guido; Schweikard, Achim; Rades, Dirk; Ernst, Floris

    2017-01-01

    Purpose: Although the metric precision of robotic stereotactic body radiation therapy in the presence of breathing motion is widely known, we investigated the dosimetric implications of breathing phase–related residual tracking errors. Methods and Materials: In 24 patients (28 liver metastases) treated with the CyberKnife, we recorded the residual correlation, prediction, and rotational tracking errors from 90 fractions and binned them into 10 breathing phases. The average breathing phase errors were used to shift and rotate the clinical tumor volume (CTV) and planning target volume (PTV) for each phase to calculate a pseudo 4-dimensional error dose distribution for comparison with the original planned dose distribution. Results: The median systematic directional correlation, prediction, and absolute aggregate rotation errors were 0.3 mm (range, 0.1-1.3 mm), 0.01 mm (range, 0.00-0.05 mm), and 1.5° (range, 0.4°-2.7°), respectively. Dosimetrically, 44%, 81%, and 92% of all voxels differed by less than 1%, 3%, and 5% of the planned local dose, respectively. The median coverage reduction for the PTV was 1.1% (range in coverage difference, −7.8% to +0.8%), significantly depending on correlation (P=.026) and rotational (P=.005) error. With a 3-mm PTV margin, the median coverage change for the CTV was 0.0% (range, −1.0% to +5.4%), not significantly depending on any investigated parameter. In 42% of patients, the 3-mm margin did not fully compensate for the residual tracking errors, resulting in a CTV coverage reduction of 0.1% to 1.0%. Conclusions: For liver tumors treated with robotic stereotactic body radiation therapy, a safety margin of 3 mm is not always sufficient to cover all residual tracking errors. Dosimetrically, this translates into only small CTV coverage reductions.

  7. Fibonacci collocation method with a residual error Function to solve linear Volterra integro differential equations

    Directory of Open Access Journals (Sweden)

    Salih Yalcinbas

    2016-01-01

    Full Text Available In this paper, a new collocation method based on the Fibonacci polynomials is introduced to solve the high-order linear Volterra integro-differential equations under the conditions. Numerical examples are included to demonstrate the applicability and validity of the proposed method and comparisons are made with the existing results. In addition, an error estimation based on the residual functions is presented for this method. The approximate solutions are improved by using this error estimation.

  8. Dosimetric Implications of Residual Tracking Errors During Robotic SBRT of Liver Metastases

    Energy Technology Data Exchange (ETDEWEB)

    Chan, Mark [Department for Radiation Oncology, University Medical Center Schleswig-Holstein, Kiel (Germany); Tuen Mun Hospital, Hong Kong (China); Grehn, Melanie [Department for Radiation Oncology, University Medical Center Schleswig-Holstein, Lübeck (Germany); Institute for Robotics and Cognitive Systems, University of Lübeck, Lübeck (Germany); Cremers, Florian [Department for Radiation Oncology, University Medical Center Schleswig-Holstein, Lübeck (Germany); Siebert, Frank-Andre [Department for Radiation Oncology, University Medical Center Schleswig-Holstein, Kiel (Germany); Wurster, Stefan [Saphir Radiosurgery Center Northern Germany, Güstrow (Germany); Department for Radiation Oncology, University Medicine Greifswald, Greifswald (Germany); Huttenlocher, Stefan [Saphir Radiosurgery Center Northern Germany, Güstrow (Germany); Dunst, Jürgen [Department for Radiation Oncology, University Medical Center Schleswig-Holstein, Kiel (Germany); Department for Radiation Oncology, University Clinic Copenhagen, Copenhagen (Denmark); Hildebrandt, Guido [Department for Radiation Oncology, University Medicine Rostock, Rostock (Germany); Schweikard, Achim [Institute for Robotics and Cognitive Systems, University of Lübeck, Lübeck (Germany); Rades, Dirk [Department for Radiation Oncology, University Medical Center Schleswig-Holstein, Lübeck (Germany); Ernst, Floris [Institute for Robotics and Cognitive Systems, University of Lübeck, Lübeck (Germany); and others

    2017-03-15

    Purpose: Although the metric precision of robotic stereotactic body radiation therapy in the presence of breathing motion is widely known, we investigated the dosimetric implications of breathing phase–related residual tracking errors. Methods and Materials: In 24 patients (28 liver metastases) treated with the CyberKnife, we recorded the residual correlation, prediction, and rotational tracking errors from 90 fractions and binned them into 10 breathing phases. The average breathing phase errors were used to shift and rotate the clinical tumor volume (CTV) and planning target volume (PTV) for each phase to calculate a pseudo 4-dimensional error dose distribution for comparison with the original planned dose distribution. Results: The median systematic directional correlation, prediction, and absolute aggregate rotation errors were 0.3 mm (range, 0.1-1.3 mm), 0.01 mm (range, 0.00-0.05 mm), and 1.5° (range, 0.4°-2.7°), respectively. Dosimetrically, 44%, 81%, and 92% of all voxels differed by less than 1%, 3%, and 5% of the planned local dose, respectively. The median coverage reduction for the PTV was 1.1% (range in coverage difference, −7.8% to +0.8%), significantly depending on correlation (P=.026) and rotational (P=.005) error. With a 3-mm PTV margin, the median coverage change for the CTV was 0.0% (range, −1.0% to +5.4%), not significantly depending on any investigated parameter. In 42% of patients, the 3-mm margin did not fully compensate for the residual tracking errors, resulting in a CTV coverage reduction of 0.1% to 1.0%. Conclusions: For liver tumors treated with robotic stereotactic body radiation therapy, a safety margin of 3 mm is not always sufficient to cover all residual tracking errors. Dosimetrically, this translates into only small CTV coverage reductions.

  9. Dosimetric Implications of Residual Tracking Errors During Robotic SBRT of Liver Metastases.

    Science.gov (United States)

    Chan, Mark; Grehn, Melanie; Cremers, Florian; Siebert, Frank-Andre; Wurster, Stefan; Huttenlocher, Stefan; Dunst, Jürgen; Hildebrandt, Guido; Schweikard, Achim; Rades, Dirk; Ernst, Floris; Blanck, Oliver

    2017-03-15

    Although the metric precision of robotic stereotactic body radiation therapy in the presence of breathing motion is widely known, we investigated the dosimetric implications of breathing phase-related residual tracking errors. In 24 patients (28 liver metastases) treated with the CyberKnife, we recorded the residual correlation, prediction, and rotational tracking errors from 90 fractions and binned them into 10 breathing phases. The average breathing phase errors were used to shift and rotate the clinical tumor volume (CTV) and planning target volume (PTV) for each phase to calculate a pseudo 4-dimensional error dose distribution for comparison with the original planned dose distribution. The median systematic directional correlation, prediction, and absolute aggregate rotation errors were 0.3 mm (range, 0.1-1.3 mm), 0.01 mm (range, 0.00-0.05 mm), and 1.5° (range, 0.4°-2.7°), respectively. Dosimetrically, 44%, 81%, and 92% of all voxels differed by less than 1%, 3%, and 5% of the planned local dose, respectively. The median coverage reduction for the PTV was 1.1% (range in coverage difference, -7.8% to +0.8%), significantly depending on correlation (P=.026) and rotational (P=.005) error. With a 3-mm PTV margin, the median coverage change for the CTV was 0.0% (range, -1.0% to +5.4%), not significantly depending on any investigated parameter. In 42% of patients, the 3-mm margin did not fully compensate for the residual tracking errors, resulting in a CTV coverage reduction of 0.1% to 1.0%. For liver tumors treated with robotic stereotactic body radiation therapy, a safety margin of 3 mm is not always sufficient to cover all residual tracking errors. Dosimetrically, this translates into only small CTV coverage reductions. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. Facts about Refractive Errors

    Science.gov (United States)

    ... to sight-saving treatments and plays a key role in reducing visual impairment and blindness. NEI Home Contact Us A-Z Site Map NEI on Social Media Information in Spanish (Información en español) Website, Social ...

  11. Prevalence of visual impairment and refractive error in school-aged children in South Darfur State of Sudan

    Directory of Open Access Journals (Sweden)

    Saif H. Alrasheed

    2016-10-01

    Full Text Available Background: Global estimates suggest there are almost 19 million visually impaired children worldwide, the major cause being uncorrected refractive error (RE. Aim: To assess the prevalence of visual impairment (VI and RE among Sudanese school-aged children. Setting: Eight randomly selected primary schools from 21 districts in South Darfur State of Sudan were involved. Methods: A school-based cross-sectional study of RE and VI in primary schoolchildren from grades 1 to 8 (children aged 6–15 years was investigated. A Refractive Error Study in Children (RESC protocol was implemented to determine the prevalence of RE and VI in these schoolaged children. Participants were enrolled through stratified multistage cluster sampling of four all-male and four all-female primary schools from South Darfur State of Sudan. Examination procedures followed the RESC protocol, which included visual acuity (VA measurements, binocular vision assessments, retinoscopy and autorefraction under cycloplegia, as well as examination of the external eye, anterior-segment, media and fundus. Results: A total of 1775 children were invited to participate in the study and 1678 were examined resulting in a participation rate of 94.5%. The findings indicated that the prevalence of uncorrected, presenting and best-corrected VA of 6/12 or worse was 6.4% (95% confidence interval [CI], 4.9–7.9, 4.4% (95% CI, 2.9–5.9 and 1.2% (95% CI, 0.3–2.7 respectively. RE was the cause of VI in 57% of participants, retinal disorders in 13.1%, amblyopia in 5.6%, corneal opacity in 0.9%, cataract in 3.7%, with the causes of reduced vision undetermined in 10.3% and various other causes contributed 9.3%. External and anterior-segment abnormalities were observed in 10.2% of children. This was mainly allergic conjunctivitis (5.3% followed by bacterial and viral conjunctivitis (4.2%. The prevalence of myopia (≥|-0.50 D| in one or both eyes was 6.8% (95% CI, 5.3–8.3, hypermetropia (≥ 2 D was

  12. CORRELATION OF FUNDUS CHANGES IN RELATION TO REFRACTIVE ERROR IN PATIENTS WITH MYOPIA- A CLINICAL PROSPECTIVE STUDY

    Directory of Open Access Journals (Sweden)

    Balasubramanian M. Manickavelu

    2018-01-01

    Full Text Available BACKGROUND Retina is unique among the complex element of the central nervous system and the special senses. It may be readily viewed during life and it is sufficiently transparent, so that alterations within and adjacent to it may be observed in vivo. The peripheral retina owing to its thinness comparing to that of the central part, poorly-developed retinal cells, absence of large blood vessels, relatively insensitive to light, less resistance to traction, forms a seat for various lesions, which are potentially dangerous for the vision. It is in myopia that we meet the most frequent and the most obvious anomalies in the fundus changes, which bear some relation to the degree of myopia and appeal to be concerned with it either as a cause or effect or perhaps both. The aim of our study is to correlate fundus changes in relation to refractive error in patients with myopia. MATERIALS AND METHODS In our study, 100 cases of myopic (-6D:50 cases patients were selected. Detailed evaluation done. History of refractive error includes duration, age at which spectacles were worn for the first time. Time of last change of spectacles, family history of myopia, history of other symptoms like progressive loss of vision, defective vision related to day or night, sudden loss of vision, flashes and floaters. Anterior segment was examined followed by the recording of initial visual acuity and the best corrected visual acuity was noted. IOP was measured for all the cases using Schiotz tonometry. Axial length was measured in all the cases. Fundus examined with direct ophthalmoscope, indirect ophthalmoscope, 3 mirror and 90D lens. Bscan was done in few cases. The media, disc, vessels, macula and the surrounding retina were examined. The periphery was examined with indentation method. The various fundus features and pathological lesions in different degrees of myopia were noted. RESULTS Females were comparatively more affected. Highest incidence was seen in the younger

  13. Effect of distance vision and refractive error on the spontaneous eye blink activity in human subjects in primary eye gaze.

    Science.gov (United States)

    Doughty, Michael J

    2018-04-04

    To evaluate whether visual target character and visibility affects spontaneous eye blink rate (SEBR) in primary eye gaze and silence. Video recordings were made of young healthy adults who were either emmetropic (n=32) or who wore spectacles for refractive error (range -4.75D and +4.50D (n=31). Emmetropes had 5min recordings made whilst seated and looking towards a distant whiteboard. For spectacle wearers, recordings were made whilst looking towards the whiteboard with a 35mm sized cross, and repeated after spectacle removal. The average number of eye blinks over 5min was assessed, and its intra-subject variability as the coefficient of variation (COV). Over 5min without a distance target, an average SEBR of 10.4blinks/min was observed in emmetropes with a of COV=38.1%, and a significant increase in SEBR over the 5th minute to 13.6blinks/min. Hyperopes being asked to look towards a distant target showed the essentially same blinking rate of 11.1/min with or without spectacle wear with the intra-subject variability (COV) being 21.3%. Myopic subjects showed a slightly higher SEBR if looking towards a target without their spectacles (12.4 vs. 11.0blinks/min), with the COV being 18.8%. The studies indicate that some form of visual target could be useful to promote constancy of spontaneous eye blink activity over time, but that a distance visual target (when provided) does not need to be seen clearly. Crown Copyright © 2018. Published by Elsevier España, S.L.U. All rights reserved.

  14. The opportunistic screening of refractive errors in school-going children by pediatrician using enhanced Brückner test

    Directory of Open Access Journals (Sweden)

    Piyush Jain

    2016-01-01

    Full Text Available Aim: The aim of this study was to compare the results of enhanced Brückner test (EBT performed by a pediatrician and an experienced pediatric ophthalmologist. Subjects and Methods: In this prospective double-masked cohort study, a pediatrician and a pediatric ophthalmologist performed the EBT in a classroom of a school in semi-dark lighting condition using a direct ophthalmoscope. The results of the test were compared using 2 × 2 Bayesian table and kappa statistics. The findings of the pediatric ophthalmologists were considered gold standard. Results: Two hundred and thirty-six eyes of 118 subjects, mean age 6.8 ± 0.5 years (range, 5.4–7.8 years, were examined. The time taken to complete this test was <10 s per subject. The ophthalmologist identified 59 eyes as ametropic (12 hyperopic and 47 myopic eyes and 177 as emmetropic compared to 61 eyes as ametropic and 175 emmetropic by pediatrician. The prevalence of the test positive was 25.9%. The sensitivity of the pediatrician was 90.2%, specificity was 97.7%, predictive value of the positive test was 93.2%, and predictive value of the negative test was 96.6%. The clinical agreement (kappa between the pediatric ophthalmologist and the pediatrician was 0.9. Conclusion: The results of the EBT performed by pediatrician were comparable to that of an experienced pediatric ophthalmologist. Opportunistic screening of refractive errors using EBT by a pediatrician can be an important approach in the detection of ametropia in children.

  15. Variations of OCT measurements corrected for the magnification effect according to axial length and refractive error in children

    Directory of Open Access Journals (Sweden)

    Inmaculada Bueno-Gimeno

    2018-01-01

    Full Text Available Purpose: The aim of this paper was to examine the distribution of macular, retinal nerve fiber layer (RNFL thickness and optic disc parameters of myopic and hyperopic eyes in comparison with emmetropic control eyes and to investigate their variation according to axial length (AL and spherical equivalent (SE in healthy children. Methods: This study included 293 pairs of eyes of 293 children (145 boys and 148 girls, ranging in age from 6 to 17 years. Subjects were divided according to SE in control (emmetropia, 99 children, myopia (100 children and hyperopia (94 children groups and according to axial AL in 68 short (25.00mm, 36. Macular parameters, RNFL thickness and optic disc morphology were assessed by the CirrusTM HD-OCT. AL was measured using the IOL-Master system. Littmann’s formula was used for calculating the corrected AL-related ocular magnification. Results: Mean age (±SD was 10.84±3.05 years; mean (±SD SE was +0.14±0.51 D (range from −8.75 to +8.25 D and mean AL (±SD was 23.12±1.49. Average RNFL thickness, average macular thickness and macular volume decreased as AL and myopia increased. No correlations between AL/SE and optic disc parameters were found after correcting for magnification effect. Conclusions: AL and refractive error affect measurements of macular and RNFL thickness in healthy children. To make a correct interpretation of OCT measurements, ocular magnification effect should be taken into account by clinicians or OCT manufacturers.

  16. PREVALENCE OF REFRACTIVE ERROR, STRABISMUS AND AMBLYOPIA AMONG CHILDREN WITH NORMAL DEVELOPMENT OR GLOBAL DEVELOPMENTAL DELAY/INTELLECTUAL DISABILITY ATTENDING OPHTHALMOLOGY OPD AT KLES HOSPITAL, BELAGAVI- A RETROSPECTIVE STUDY

    Directory of Open Access Journals (Sweden)

    Smitha K. S

    2017-04-01

    Full Text Available BACKGROUND Global developmental delay/intellectual disability are on a rise in children in the present time. Ocular and visual anomalies are frequently associated with it of which refractive errors are the most frequent. This if goes unnoticed leads to strabismus and amblyopia. MATERIALS AND METHODS This study aims to assess the prevalence of refractive error, strabismus and amblyopia among children with normal development or global developmental delay/intellectual disability attending ophthalmology OPD at KLES Hospital, Belagavi. Case records of all 200 new patients less than or equal to 12 years of age group who attended KLES, Dr. Prabhakar Kore Hospital between January 2015 and December 2015 were retrospectively reviewed. RESULTS The male:female ratio was 1.22:1. Out of the total evaluated 200 cases, 130 cases were with normal development and 70 with GDD/ID. Refractive errors were 85%, whereas the cases of amblyopia was 45.50% and strabismus 39.50%. Amblyopia with refractive error having GDD/ID was stastically significant as compared to amblyopia with refractive error having normal development (p=0.001. CONCLUSION Refractive error was the most common ocular disorder seen. Refractive error with amblyopia is more in children with GDD/ID as compared to normal children. Owing to the high percentage of visual anomalies, ophthalmological referral becomes essential in children with developmental anomalies.

  17. Accommodation: The role of the external muscles of the eye: A consideration of refractive errors in relation to extraocular malfunction.

    Science.gov (United States)

    Hargrave, B K

    2014-11-01

    Speculation as to optical malfunction has led to dissatisfaction with the theory that the lens is the sole agent in accommodation and to the suggestion that other parts of the eye are also conjointly involved. Around half-a-century ago, Robert Brooks Simpkins suggested that the mechanical features of the human eye were precisely such as to allow for a lengthening of the globe when the eye accommodated. Simpkins was not an optical man but his theory is both imaginative and comprehensive and deserves consideration. It is submitted here that accommodation is in fact a twofold process, and that although involving the lens, is achieved primarily by means of a give - and - take interplay between adducting and abducting external muscles, whereby an elongation of the eyeball is brought about by a stretching of the delicate elastic fibres immediately behind the cornea. The three muscles responsible for convergence (superior, internal and inferior recti) all pull from in front backwards, while of the three abductors (external rectus and the two obliques) the obliques pull from behind forwards, allowing for an easy elongation as the eye turns inwards and a return to its original length as the abducting muscles regain their former tension, returning the eye to distance vision. In refractive errors, the altered length of the eyeball disturbs the harmonious give - and - take relationship between adductors and abductors. Such stresses are likely to be perpetuated and the error exacerbated. Speculation is not directed towards a search for a possible cause of the muscular imbalance, since none is suspected. Muscles not used rapidly lose tone, as evidenced after removal of a limb from plaster. Early attention to the need for restorative exercise is essential and results usually impressive. If flexibility of the external muscles of the eyes is essential for continuing good sight, presbyopia can be avoided and with it the supposed necessity of glasses in middle life. Early attention

  18. Refractive errors and visual acuity impairment among self-selected Hispanic, white, and black adults examined by the UCLA Mobile Eye Clinic.

    Science.gov (United States)

    Macias, E P; Lee, D A; Oelrich, F O

    1999-11-01

    Occurrence of refractive errors and uncorrected visual acuity impairment among self-selected, indigent, medically underserved Hispanic, white, and black adults examined by the staff of the UCLA Mobile Eye Clinic (MEC) are described in this study and compared to population-based studies. The study sample consisted of all 2,970 Hispanic, 1,228 white, and 1,028 black participants, for a total of 5,226 self-selected adults, ages 25 to 74 years, who received vision screenings and eye examinations by the staff of the UCLA MEC from 1987 to 1997. Tests consisted of visual acuity, refractive error, intraocular pressure, retinoscopy, slit-lamp biomicroscopy, direct ophthalmoscopic examination, and indirect ophthalmoloscopy with pupillary dilation. Levels of visual acuity impairment were defined as mild (20/50-20/80), moderate (20/100), or severe (20/200 or worse) in either eye. Self-selected whites in this study had higher rates of astigmatism, anisometropia, and hyperopia, while myopia was higher among self-selected blacks. Myopia and hyperopia occurred more frequently among younger age groups for all ethnic groups. Whites had a higher occurrence of mild, moderate, and severe visual acuity impairment, as compared with Hispanics and blacks. Both refractive errors and impaired visual acuity of this self-selected sample are similar to those of adults from the National Health and Nutrition Examination Survey, Hispanic Health and Nutrition Examination Survey, and the Baltimore Eye Survey. The data presented in this study provide a crude estimate of the occurrence of refractive errors and impaired visual acuity among self-selected, medically underserved, indigent Hispanic, white, and black adults in the Los Angeles area.

  19. Minimizing Actuator-Induced Residual Error in Active Space Telescope Primary Mirrors

    Science.gov (United States)

    2010-09-01

    modeling process using Matlab and MSC Nastran to sim- ulate actuator-induced residual error. . . . . . . . . . . . . . . . . . 47 3-3 Finite element mirror...automatically gener- ates the structural design of space telescope via Nastran , adds representative dynamic disturbances, simulates the application of...polynomials and Bessel functions. The authors employ a piezoelectrically- actuated membrane mirror model implemented using MSC Nastran to calculate the

  20. Prevalence of refractive errors and ocular disorders in preschool and school children of Ibiporã - PR, Brazil (1989 to 1996

    Directory of Open Access Journals (Sweden)

    Schimiti Rui Barroso

    2001-01-01

    Full Text Available Purpose: To establish the prevalence of refractive errors and ocular disorders in preschool and schoolchildren of Ibiporã, Brazil. Methods: A survey of 6 to 12-year-old children from public and private elementary schools was carried out in Ibiporã between 1989 and 1996. Visual acuity measurements were performed by trained teachers using Snellen's chart. Children with visual acuity <0.7 in at least one eye were referred to a complete ophthalmologic examination. Results: 35,936 visual acuity measurements were performed in 13,471 children. 1.966 children (14.59% were referred to an ophthalmologic examination. Amblyopia was diagnosed in 237 children (1.76%, whereas strabismus was observed in 114 cases (0.84%. Cataract (n=17 (0.12%, chorioretinitis (n=38 (0.28% and eyelid ptosis (n=6 (0.04% were also diagnosed. Among the 614 (4.55% children who were found to have refractive errors, 284 (46.25% had hyperopia (hyperopia or hyperopic astigmatism, 206 (33.55% had myopia (myopia or myopic astigmatism and 124 (20.19% showed mixed astigmatism. Conclusions: The study determined the local prevalence of amblyopia, refractive errors and eye disorders among preschool and schoolchildren.

  1. Visual disability, visual function, and myopia among rural chinese secondary school children: the Xichang Pediatric Refractive Error Study (X-PRES)--report 1.

    Science.gov (United States)

    Congdon, Nathan; Wang, Yunfei; Song, Yue; Choi, Kai; Zhang, Mingzhi; Zhou, Zhongxia; Xie, Zhenling; Li, Liping; Liu, Xueyu; Sharma, Abhishek; Wu, Bin; Lam, Dennis S C

    2008-07-01

    To evaluate visual acuity, visual function, and prevalence of refractive error among Chinese secondary-school children in a cross-sectional school-based study. Uncorrected, presenting, and best corrected visual acuity, cycloplegic autorefraction with refinement, and self-reported visual function were assessed in a random, cluster sample of rural secondary school students in Xichang, China. Among the 1892 subjects (97.3% of the consenting children, 84.7% of the total sample), mean age was 14.7 +/- 0.8 years, 51.2% were female, and 26.4% were wearing glasses. The proportion of children with uncorrected, presenting, and corrected visual disability (visual disability when tested without correction, 98.7% was due to refractive error, while only 53.8% (414/770) of these children had appropriate correction. The girls had significantly (P visual disability and myopia visual function (ANOVA trend test, P Visual disability in this population was common, highly correctable, and frequently uncorrected. The impact of refractive error on self-reported visual function was significant. Strategies and studies to understand and remove barriers to spectacle wear are needed.

  2. Genome-wide meta-analyses of multi-ethnic cohorts identify multiple new susceptibility loci for refractive error and myopia

    Science.gov (United States)

    Verhoeven, Virginie J.M.; Hysi, Pirro G.; Wojciechowski, Robert; Fan, Qiao; Guggenheim, Jeremy A.; Höhn, René; MacGregor, Stuart; Hewitt, Alex W.; Nag, Abhishek; Cheng, Ching-Yu; Yonova-Doing, Ekaterina; Zhou, Xin; Ikram, M. Kamran; Buitendijk, Gabriëlle H.S.; McMahon, George; Kemp, John P.; St. Pourcain, Beate; Simpson, Claire L.; Mäkelä, Kari-Matti; Lehtimäki, Terho; Kähönen, Mika; Paterson, Andrew D.; Hosseini, S. Mohsen; Wong, Hoi Suen; Xu, Liang; Jonas, Jost B.; Pärssinen, Olavi; Wedenoja, Juho; Yip, Shea Ping; Ho, Daniel W. H.; Pang, Chi Pui; Chen, Li Jia; Burdon, Kathryn P.; Craig, Jamie E.; Klein, Barbara E. K.; Klein, Ronald; Haller, Toomas; Metspalu, Andres; Khor, Chiea-Chuen; Tai, E-Shyong; Aung, Tin; Vithana, Eranga; Tay, Wan-Ting; Barathi, Veluchamy A.; Chen, Peng; Li, Ruoying; Liao, Jiemin; Zheng, Yingfeng; Ong, Rick T.; Döring, Angela; Evans, David M.; Timpson, Nicholas J.; Verkerk, Annemieke J.M.H.; Meitinger, Thomas; Raitakari, Olli; Hawthorne, Felicia; Spector, Tim D.; Karssen, Lennart C.; Pirastu, Mario; Murgia, Federico; Ang, Wei; Mishra, Aniket; Montgomery, Grant W.; Pennell, Craig E.; Cumberland, Phillippa M.; Cotlarciuc, Ioana; Mitchell, Paul; Wang, Jie Jin; Schache, Maria; Janmahasathian, Sarayut; Igo, Robert P.; Lass, Jonathan H.; Chew, Emily; Iyengar, Sudha K.; Gorgels, Theo G.M.F.; Rudan, Igor; Hayward, Caroline; Wright, Alan F.; Polasek, Ozren; Vatavuk, Zoran; Wilson, James F.; Fleck, Brian; Zeller, Tanja; Mirshahi, Alireza; Müller, Christian; Uitterlinden, Andre’ G.; Rivadeneira, Fernando; Vingerling, Johannes R.; Hofman, Albert; Oostra, Ben A.; Amin, Najaf; Bergen, Arthur A.B.; Teo, Yik-Ying; Rahi, Jugnoo S.; Vitart, Veronique; Williams, Cathy; Baird, Paul N.; Wong, Tien-Yin; Oexle, Konrad; Pfeiffer, Norbert; Mackey, David A.; Young, Terri L.; van Duijn, Cornelia M.; Saw, Seang-Mei; Wilson, Joan E. Bailey; Stambolian, Dwight; Klaver, Caroline C.; Hammond, Christopher J.

    2013-01-01

    Refractive error is the most common eye disorder worldwide, and a prominent cause of blindness. Myopia affects over 30% of Western populations, and up to 80% of Asians. The CREAM consortium conducted genome-wide meta-analyses including 37,382 individuals from 27 studies of European ancestry, and 8,376 from 5 Asian cohorts. We identified 16 new loci for refractive error in subjects of European ancestry, of which 8 were shared with Asians. Combined analysis revealed 8 additional loci. The new loci include genes with functions in neurotransmission (GRIA4), ion channels (KCNQ5), retinoic acid metabolism (RDH5), extracellular matrix remodeling (LAMA2, BMP2), and eye development (SIX6, PRSS56). We also confirmed previously reported associations with GJD2 and RASGRF1. Risk score analysis using associated SNPs showed a tenfold increased risk of myopia for subjects with the highest genetic load. Our results, accumulated across independent multi-ethnic studies, considerably advance understanding of mechanisms involved in refractive error and myopia. PMID:23396134

  3. Steps towards Smarter Solutions in Optometry and Ophthalmology—Inter-Device Agreement of Subjective Methods to Assess the Refractive Errors of the Eye

    Directory of Open Access Journals (Sweden)

    Arne Ohlendorf

    2016-07-01

    Full Text Available Purpose: To investigate the inter-device agreement and mean differences between a newly developed digital phoropter and the two standard methods (trial frame and manual phoropter. Methods: Refractive errors of two groups of participants were measured by two examiners (examiner 1 (E1: 36 subjects; examiner 2 (E2: 38 subjects. Refractive errors were assessed using a trial frame, a manual phoropter and a digital phoropter. Inter-device agreement regarding the measurement of refractive errors was analyzed for differences in terms of the power vector components (spherical equivalent (SE and the cylindrical power vector components J0 and J45 between the used methods. Intraclass correlation coefficients (ICC’s were calculated to evaluate correlations between the used methods. Results: Analyzing the variances between the three methods for SE, J0 and J45 using a two-way ANOVA showed no significant differences between the methods (SE: p = 0.13, J0: p = 0.58 and J45: p = 0.96 for examiner 1 and for examiner 2 (SE: p = 0.88, J0: p = 0.95 and J45: p = 1. Mean differences and ±95% Limits of Agreement for each pair of inter-device agreement regarding the SE for both examiners were as follows: Trial frame vs. digital phoropter: +0.10 D ± 0.56 D (E1 and +0.19 D ± 0.60 D (E2, manual phoropter vs. trial frame: −0.04 D ± 0.59 D (E1 and −0.12 D ± 0.49 D (E2 and for manual vs. digital phoropter: +0.06 D ± 0.65 D (E1 and +0.08 D ± 0.45 D (E2. ICCs revealed high correlations between all methods for both examiner (p < 0.001. The time to assess the subjective refraction was significantly smaller with the digital phoropter (examiner 1: p < 0.001; examiner 2: p < 0.001. Conclusion: “All used subjective methods show a good agreement between each other terms of ICC (>0.9. Assessing refractive errors using different subjective methods, results in similar mean differences and 95% limits of agreement, when compared to those reported in studies comparing

  4. Structural brain differences in school-age children with residual speech sound errors.

    Science.gov (United States)

    Preston, Jonathan L; Molfese, Peter J; Mencl, W Einar; Frost, Stephen J; Hoeft, Fumiko; Fulbright, Robert K; Landi, Nicole; Grigorenko, Elena L; Seki, Ayumi; Felsenfeld, Susan; Pugh, Kenneth R

    2014-01-01

    The purpose of the study was to identify structural brain differences in school-age children with residual speech sound errors. Voxel based morphometry was used to compare gray and white matter volumes for 23 children with speech sound errors, ages 8;6-11;11, and 54 typically speaking children matched on age, oral language, and IQ. We hypothesized that regions associated with production and perception of speech sounds would differ between groups. Results indicated greater gray matter volumes for the speech sound error group relative to typically speaking controls in bilateral superior temporal gyrus. There was greater white matter volume in the corpus callosum for the speech sound error group, but less white matter volume in right lateral occipital gyrus. Results may indicate delays in neuronal pruning in critical speech regions or differences in the development of networks for speech perception and production. Copyright © 2013 Elsevier Inc. All rights reserved.

  5. Steps towards Smarter Solutions in Optometry and Ophthalmology-Inter-Device Agreement of Subjective Methods to Assess the Refractive Errors of the Eye.

    Science.gov (United States)

    Ohlendorf, Arne; Leube, Alexander; Wahl, Siegfried

    2016-07-13

    To investigate the inter-device agreement and mean differences between a newly developed digital phoropter and the two standard methods (trial frame and manual phoropter). Refractive errors of two groups of participants were measured by two examiners (examiner 1 (E1): 36 subjects; examiner 2 (E2): 38 subjects). Refractive errors were assessed using a trial frame, a manual phoropter and a digital phoropter. Inter-device agreement regarding the measurement of refractive errors was analyzed for differences in terms of the power vector components (spherical equivalent (SE) and the cylindrical power vector components J0 and J45) between the used methods. Intraclass correlation coefficients (ICC's) were calculated to evaluate correlations between the used methods. Analyzing the variances between the three methods for SE, J0 and J45 using a two-way ANOVA showed no significant differences between the methods (SE: p = 0.13, J0: p = 0.58 and J45: p = 0.96) for examiner 1 and for examiner 2 (SE: p = 0.88, J0: p = 0.95 and J45: p = 1). Mean differences and ±95% Limits of Agreement for each pair of inter-device agreement regarding the SE for both examiners were as follows: Trial frame vs. digital phoropter: +0.10 D ± 0.56 D (E1) and +0.19 D ± 0.60 D (E2), manual phoropter vs. trial frame: -0.04 D ± 0.59 D (E1) and -0.12 D ± 0.49 D (E2) and for manual vs. digital phoropter: +0.06 D ± 0.65 D (E1) and +0.08 D ± 0.45 D (E2). ICCs revealed high correlations between all methods for both examiner (p digital phoropter (examiner 1: p 0.9). Assessing refractive errors using different subjective methods, results in similar mean differences and 95% limits of agreement, when compared to those reported in studies comparing subjective refraction non-cylcoplegic retinoscopy or autorefraction".

  6. Steps towards Smarter Solutions in Optometry and Ophthalmology—Inter-Device Agreement of Subjective Methods to Assess the Refractive Errors of the Eye

    Science.gov (United States)

    Ohlendorf, Arne; Leube, Alexander; Wahl, Siegfried

    2016-01-01

    Purpose: To investigate the inter-device agreement and mean differences between a newly developed digital phoropter and the two standard methods (trial frame and manual phoropter). Methods: Refractive errors of two groups of participants were measured by two examiners (examiner 1 (E1): 36 subjects; examiner 2 (E2): 38 subjects). Refractive errors were assessed using a trial frame, a manual phoropter and a digital phoropter. Inter-device agreement regarding the measurement of refractive errors was analyzed for differences in terms of the power vector components (spherical equivalent (SE) and the cylindrical power vector components J0 and J45) between the used methods. Intraclass correlation coefficients (ICC’s) were calculated to evaluate correlations between the used methods. Results: Analyzing the variances between the three methods for SE, J0 and J45 using a two-way ANOVA showed no significant differences between the methods (SE: p = 0.13, J0: p = 0.58 and J45: p = 0.96) for examiner 1 and for examiner 2 (SE: p = 0.88, J0: p = 0.95 and J45: p = 1). Mean differences and ±95% Limits of Agreement for each pair of inter-device agreement regarding the SE for both examiners were as follows: Trial frame vs. digital phoropter: +0.10 D ± 0.56 D (E1) and +0.19 D ± 0.60 D (E2), manual phoropter vs. trial frame: −0.04 D ± 0.59 D (E1) and −0.12 D ± 0.49 D (E2) and for manual vs. digital phoropter: +0.06 D ± 0.65 D (E1) and +0.08 D ± 0.45 D (E2). ICCs revealed high correlations between all methods for both examiner (p digital phoropter (examiner 1: p 0.9). Assessing refractive errors using different subjective methods, results in similar mean differences and 95% limits of agreement, when compared to those reported in studies comparing subjective refraction non-cylcoplegic retinoscopy or autorefraction”. PMID:27417629

  7. Prevalence of refractive errors in students in Northeastern Brazil Prevalência dos erros refrativos em estudantes do Nordeste Brasileiro

    Directory of Open Access Journals (Sweden)

    Carlos Alexandre de Amorim Garcia

    2005-06-01

    Full Text Available PURPOSE: To determine the prevalence of refractive errors in the public and private school system in the city of Natal, Northeastern Brazil. METHODS: Refractometry was performed on both eyes of 1,024 randomly selected students, enrolled in the 2001 school year and the data were evaluated by the SPSS Data Editor 10.0. Ametropia was divided into: 1- from 0.1 to 0.99 diopter (D; 2- 1.0 to 2.99D; 3- 3.00 to 5.99D and 4- 6D or greater. Astigmatism was regrouped in: I- with-the-rule (axis from 0 to 30 and 150 to 180 degrees, II- against-the-rule (axis between 60 and 120 degrees and III- oblique (axis between > 30 and 120 and OBJETIVO: Determinar a prevalência das ametropias em estudantes das redes pública e privada de Natal-RN. MÉTODOS: Foi realizada refratometria de 2.048 olhos de estudantes matriculados no ano letivo de 2001 e os dados avaliados com planilha do SPSS Data Editor 11. As ametropias foram divididas em: 1- de 0,1 até 0,99D (dioptria; 2- 1,0 até 2,99D; 3- 3,00 até 5,99D e 4- 6D ou maior. O astigmatismo foi reagrupado em I- a favor da regra (eixo entre 0 a 30 e 150 a 180 graus, II- contra a regra (eixo entre 60 e 120 graus e III- oblíquo (eixo entre >30 e 120 e <150 graus. A faixa etária foi categorizada em 1- 5 a 10 anos, 2- 11 a 15 anos, 3- 16 a 20 anos, 4- 21anos ou mais. RESULTADOS: Dos erros refrativos, a hipermetropia foi o mais comum com 71%, em seguida astigmatismo, 34% e miopia, 13,3%. 48,5% dos míopes e 34,1% dos hipermétropes tinham astigmatismo. De acordo com as dioptrias, 58,1% dos míopes estão no grupo 1, 39% distribuídos entre os grupos 2 e 3. Os hipermétropes enquadram-se em sua maioria no grupo 1 (61,7% e o astigmatismo no mesmo grupo com 70,6%. A associação dos eixos do astigmatismo dos dois olhos mostrou 95,2% com eixo a favor da regra nos dois olhos, diminuindo a porcentagem para os do eixo contra a regra (82,1% e menor ainda para os do eixo oblíquo, apenas 50%. CONCLUSÃO: Os resultados encontrados

  8. Prevalence of Refractive Errors and Number Needed to Screen among Rural High School Children in Southern India: A Cross-sectional Study.

    Science.gov (United States)

    John, Deepika Dorothy; Paul, Padma; Kujur, Evon Selina; David, Sarada; Jasper, Smitha; Muliyil, Jayaprakash

    2017-08-01

    Avoidable blindness is mainly due to uncorrected refractive errors (URE). School Eye Screening (SES) can be used as an initiative to address this issue. To determine prevalence of URE and Number Needed to Screen (NNS) to find one child with low vision or blindness from URE among rural school children. A cross-sectional study was performed in 22 government schools with sixth to ninth grades in Kaniyambadi block of Vellore District of Tamil Nadu, India. There were 4739 children on the rolls. Among children present, all those identified to have a visual deficit in either eye, using a single line 20/40 Snellen's optotype E chart at 6 m, were referred to the hospital for confirmatory evaluation. Blindness (uncorrected) was defined as inability to see 20/200 in the better eye. In two of these schools, visual deficits were validated through a second school based examination by a clinician. Of the 4739 children on rolls, 601 were absent; all 4138 (87.3%) who were present underwent screening; 2.3% (98) {95% Confidence Interval (CI) 1.8 to 2.8} failed the screening test in at least one eye and were referred for examination. Only 28 (28.6%) of 98 children who were referred came for examination to the hospital. In the 2 of the 22 schools where the visual deficit was validated, there were no false positives. The prevalence of refractive error in these two schools was 2.2% (95% CI 1.7 - 2.7). NNS to detect one child with low vision or blindness from URE was 147. Magnitude of refractive error, low NNS, low response to referral necessitates complete care at school and hence a relook at the current SES program.

  9. Shifted Legendre method with residual error estimation for delay linear Fredholm integro-differential equations

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    Şuayip Yüzbaşı

    2017-03-01

    Full Text Available In this paper, we suggest a matrix method for obtaining the approximate solutions of the delay linear Fredholm integro-differential equations with constant coefficients using the shifted Legendre polynomials. The problem is considered with mixed conditions. Using the required matrix operations, the delay linear Fredholm integro-differential equation is transformed into a matrix equation. Additionally, error analysis for the method is presented using the residual function. Illustrative examples are given to demonstrate the efficiency of the method. The results obtained in this study are compared with the known results.

  10. Value of dual biometry in the detection and investigation of error in the preoperative prediction of refractive status following cataract surgery.

    LENUS (Irish Health Repository)

    Charalampidou, Sofia

    2012-02-01

    PURPOSE: To report the value of dual biometry in the detection of biometry errors. METHODS: Study 1: retrospective study of 224 consecutive cataract operations. The intraocular lens power calculation was based on immersion biometry. Study 2: immersion biometry was compared with optical coherence biometry (OCB) in terms of axial length, anterior chamber depth, keratometry readings and the recommended lens power to achieve emmetropia. Study 3: prospective study of 61 consecutive cataract operations. Both immersion and OCB were performed, but lens power calculation was based on the latter. RESULTS: Study 1: 115 (86%), 101 (75.4%), 90 (67.2%) and 50 (37.3%) of postoperative spherical equivalents were within +\\/-1.5 dioptres (D), +\\/-1.25 D, +\\/-1 D and +\\/-0.5 D of the target, respectively. Study 2: excellent agreement between axial length readings, anterior chamber depth readings and keratometry readings by immersion biometry and OCB was observed (reflected in a mean bias of -0.065 mm, -0.048 mm and +0.1803 D, respectively, in association with OCB). Agreement between the lens power recommended by each technique to achieve emmetropia was poor (mean bias of +1.16 D in association with OCB), but improved following appropriate modification of lens constants in the Accutome A-scan software (mean bias with OCB = -0.4 D). Study 3: 37 (92.5%) and 23 (57.5%) of operated eyes achieved a postoperative refraction within +\\/-1 D and +\\/-0.5 D of target, respectively. CONCLUSION: Systematic errors in biometry can exist, in the presence of acceptable postoperative refractive results. Dual biometry allows each biometric parameter to be scrutinized in isolation, and identify sources of error that may otherwise go undetected.

  11. Differential effects of visual-acoustic biofeedback intervention for residual speech errors

    Directory of Open Access Journals (Sweden)

    Tara Mcallister Byun

    2016-11-01

    Full Text Available Recent evidence suggests that the incorporation of visual biofeedback technologies may enhance response to treatment in individuals with residual speech errors. However, there is a need for controlled research systematically comparing biofeedback versus non-biofeedback intervention approaches. This study implemented a single-subject experimental design with a crossover component to investigate the relative efficacy of visual-acoustic biofeedback and traditional articulatory treatment for residual rhotic errors. Eleven child/adolescent participants received ten sessions of visual-acoustic biofeedback and ten sessions of traditional treatment, with the order of biofeedback and traditional phases counterbalanced across participants. Probe measures eliciting untreated rhotic words were administered in at least 3 sessions prior to the start of treatment (baseline, between the two treatment phases (midpoint, and after treatment ended (maintenance, as well as before and after each treatment session. Perceptual accuracy of rhotic production was assessed by outside listeners in a blinded, randomized fashion. Results were analyzed using a combination of visual inspection of treatment trajectories, individual effect sizes, and logistic mixed-effects regression. Effect sizes and visual inspection revealed that participants could be divided into categories of strong responders (n=4, mixed/moderate responders (n=3, and non-responders (n=4. Individual results did not reveal a reliable pattern of stronger performance in biofeedback versus traditional blocks, or vice versa. Moreover, biofeedback versus traditional treatment was not a significant predictor of accuracy in the logistic mixed-effects model examining all within-treatment word probes. However, the interaction between treatment condition and treatment order was significant: biofeedback was more effective than traditional treatment in the first phase of treatment, and traditional treatment was more

  12. Comparison the post operative refractive errors in same size corneal transplantation through deep lamellar keratoplasty and penetrating keratoplasty methods after sutures removing in keratoconus patients

    Directory of Open Access Journals (Sweden)

    Hasan Razmjoo

    2016-01-01

    Full Text Available Background: Corneal transplantation is a surgery in which cornea is replaced by a donated one and can be completely penetrating keratoplasty (PK or included a part of cornea deep lamellar keratoplasty (DLK. Although the functional results are limited by some complications, it is considered as one of the most successful surgeries. This study aimed to compare the refractive errors after same size corneal transplantation through DLK and PK methods in keratoconus patients over 20 years. Materials and Methods: This descriptive, analytical study was conducted in Feiz Hospital, Sadra and Persian Clinics of Isfahan in 2013–2014. In this study, 35 patients underwent corneal transplantation by PK and 35 patients by DLK, after removing the sutures, the patients were compared in terms of best corrected visual acuity (BCVA and refractive errors. Data were analyzed using Chi-square and t Student tests by SPSS software. Results: The BCVA mean in DLK and PK groups was 6/10 ± 2/10 and 5/10 ± 2/10, respectively, with no significant difference (P = 0.4. The results showed 9 cases of DLK and 6 cases of PK had normal (8/10 ≤ BCVA visual acuity (25.7% vs. 17.1%, 24 cases of DLK and 27 cases of PK had mild vision impairment (68.6% vs. 77.1% and 2 cases of the DLK group and 2 cases of PK had moderate vision impairment, (5.7% vs. 5.7%, there was no significant difference in “BCVA” (P = 0.83. Conclusions: Both methods were acceptably effective in improving BCVA, but according to previous articles (5,9,10 the DLK method due to fewer complications and less risk of rejection was superior to another method and in the absence of any prohibition this method is recommended.

  13. Prevalence of Amblyopia in School-Aged Children and Variations by Age, Gender, and Ethnicity in a Multi-Country Refractive Error Study.

    Science.gov (United States)

    Xiao, Ou; Morgan, Ian G; Ellwein, Leon B; He, Mingguang

    2015-09-01

    To estimate the age-, gender-, and ethnicity-specific prevalence of amblyopia in children aged 5 to 15 years using data from the multi-country Refractive Error Study in Children (RESC). Population-based, cross-sectional study. Among 46 260 children aged 5 to 15 years who were enumerated from 8 sites in the RESC study, 39 551 had a detailed ocular examination and a reliable visual acuity (VA) measurement in 1 or both eyes. Information on ethnicity was available for 39 321 of these participants. This study focused on findings from the 39 321 children. The examination included VA measurements, evaluation of ocular alignment and refractive error under cycloplegia, and examination of the external eye, anterior segment, media, and fundus. The proportion of children aged 5 to 15 years with amblyopia in different ethnic cohorts. Amblyopia was defined as best-corrected visual acuity (BCVA) of ≤20/40 in either eye, with tropia, anisometropia (≥2 spherical equivalent diopters [D]), or hyperopia (≥+6 spherical equivalent D), after excluding children with fundus or anterior segment abnormalities. The overall prevalence of amblyopia was 0.74% (95% confidence interval, 0.64-0.83) with significant (P Amblyopia was not associated with age or gender. The most common cause of amblyopia was anisometropia. In this study, the prevalence of amblyopia varied with ethnicity and was highest in Hispanic children and lowest in African children. Most cases were unilateral and developed before the age of 5 years. The impact of changes of definitions on prevalence estimates is discussed. Copyright © 2015 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

  14. Changing trends in the prevalence of visual impairment, uncorrected refractive errors and use of spectacles in Mahbubnagar district in South India

    Directory of Open Access Journals (Sweden)

    Srinivas Marmamula

    2013-01-01

    Full Text Available Background/Aim: The Andhra Pradesh Eye disease Study (APEDS was a conventional cross-sectional study conducted in four locations during 1996-2000. Ten years later, a Rapid Assessment of Refractive Errors (RARE survey was conducted in one of the geographical regions. The prevalence of visual impairment (VI, uncorrected refractive error (URE, spectacles use obtained from both the surveys was compared. Settings and Design: Rural settings; cross-sectional studies. Materials and Methods: In both the surveys, distance visual acuity (VA was assessed using a logMAR chart. Pinhole VA was assessed if presenting VA was <20/20 in APEDS and <20/40 in RARE. VI was defined as presenting VA <20/40 in the better eye. URE was defined as presenting VA <20/40 and improving to ≥20/40 with a pinhole. Statistical Analysis Used: Performed using Statistical Package for Social Sciences (SPSS. Chi square tests and t-test were used. Results and Conclusions: The results from a RARE survey with 3,095 subjects were compared with an APEDS dataset that had 1,232 subjects in the same age group of 15-49 years. The prevalence of VI has decreased from 9.5% (95% CI, 7.7-11.1 in APEDS to 2.7% (95% CI, 2.1-3.3 in RARE. Similarly, the prevalence of URE in the better eye decreased from 5.8% (95% CI, 4.5-7.1 to 2.3% (95% CI, 1.8-2.8. The usage of spectacles increased from 6.6% (95% CI, 5.2-8.0 to 9.7% (95% CI, 8.7-10.7. There is a decreasing trend in the prevalence of VI and URE in Mahbubnagar district in Andhra Pradesh over a decade.

  15. Spectacle acceptance among secondary school students in rural China: the Xichang Pediatric Refractive Error Study (X-PRES)--report 5.

    Science.gov (United States)

    Li, Liping; Song, Yue; Liu, Xiaojian; Lu, Bei; Choi, Kai; Lam, Dennis S C; Zhang, Mingzhi; Zheng, Mingwei; Wang, Yunfei; Sharma, Abhishek; Congdon, Nathan

    2008-07-01

    To assess determinants of spectacle acceptance and use among rural Chinese children. Children with uncorrected acuity or = 2 lines with refraction were identified from a school-based sample of 1892 students. Information on obtaining glasses and the benefits of spectacles was provided to children, families, and teachers. Purchase of new spectacles and reasons for nonpurchase were assessed by direct inspection and interview 3 months later. Among 674 (35.6%) children requiring spectacles (mean age, 14.7 +/- 0.8 years), 597 (88.6%) were followed up. Among 339 children with no glasses at baseline, 30.7% purchased spectacles, whereas 43.2% of 258 children with inaccurate glasses replaced them. Most (70%) subjects paid US$13 to $26. Among children with bilateral vision price or parental refusal (18%), and fear glasses would weaken the eyes (13%). Only 26% of children stated that they usually wore their new glasses. Many families in rural China will pay for glasses, though spectacle acceptance was Acceptance could be improved by price reduction, education showing that glasses will not harm the eyes, and parent-focused interventions.

  16. Residual rotational set-up errors after daily cone-beam CT image guided radiotherapy of locally advanced cervical cancer

    International Nuclear Information System (INIS)

    Laursen, Louise Vagner; Elstrøm, Ulrik Vindelev; Vestergaard, Anne; Muren, Ludvig P.; Petersen, Jørgen Baltzer; Lindegaard, Jacob Christian; Grau, Cai; Tanderup, Kari

    2012-01-01

    Purpose: Due to the often quite extended treatment fields in cervical cancer radiotherapy, uncorrected rotational set-up errors result in a potential risk of target miss. This study reports on the residual rotational set-up error after using daily cone beam computed tomography (CBCT) to position cervical cancer patients for radiotherapy treatment. Methods and materials: Twenty-five patients with locally advanced cervical cancer had daily CBCT scans (650 CBCTs in total) prior to treatment delivery. We retrospectively analyzed the translational shifts made in the clinic prior to each treatment fraction as well as the residual rotational errors remaining after translational correction. Results: The CBCT-guided couch movement resulted in a mean translational 3D vector correction of 7.4 mm. Residual rotational error resulted in a target shift exceeding 5 mm in 57 of the 650 treatment fractions. Three patients alone accounted for 30 of these fractions. Nine patients had no shifts exceeding 5 mm and 13 patients had 5 or less treatment fractions with such shifts. Conclusion: Twenty-two of the 25 patients have none or few treatment fractions with target shifts larger than 5 mm due to residual rotational error. However, three patients display a significant number of shifts suggesting a more systematic set-up error.

  17. Prevalence and risk factors for myopia and other refractive errors in an adult population in southern India.

    Science.gov (United States)

    Joseph, Sanil; Krishnan, Tiruvengada; Ravindran, Ravilla D; Maraini, Giovanni; Camparini, Monica; Chakravarthy, Usha; Ravilla, Thulasiraj D; Hutchings, Andrew; Fletcher, Astrid E

    2018-05-01

    To investigate prevalence and risk factors for myopia, hyperopia and astigmatism in southern India. Randomly sampled villages were enumerated to identify people aged ≥40 years. Participants were interviewed for socioeconomic and lifestyle factors and attended a hospital-based ophthalmic examination including visual acuity measurement and objective and subjective measurement of refractive status. Myopia was defined as spherical equivalent (SE) worse than -0.75 dioptres (D), hyperopia as SE ≥+1D and astigmatism as cylinder <-0.5. The age-standardised prevalences of myopia, hyperopia and astigmatism were 35.6% (95% CI: 34.7-36.6), 17.0% (95% CI: 16.3-17.8) and 32.6 (29.3-36.1), respectively. Of those with myopia (n = 1490), 70% had advanced cataract. Of these, 79% had presenting visual acuity (VA) less than 6/18 and after best correction, 44% of these improved to 6/12 or better and 27% remained with VA less than 6/18. In multivariable analyses (excluding patients with advanced cataract), increasing nuclear opacity score, current tobacco use, and increasing height were associated with higher odds of myopia. Higher levels of education were associated with increased odds of myopia in younger people and decreased odds in older people. Increasing time outdoors was associated with myopia only in older people. Increasing age and female gender were associated with hyperopia, and nuclear opacity score, increasing time outdoors, rural residence and current tobacco use with lower odds of hyperopia. After controlling for myopia, factors associated with higher odds of astigmatism were age, rural residence, and increasing nuclear opacity score and increasing education with lower odds. In contrast to high-income settings and in agreement with studies from low-income settings, we found a rise in myopia with increasing age reflecting the high prevalence of advanced cataract. © 2018 The Authors. Ophthalmic and Physiological Optics published by John Wiley & Sons Ltd on behalf of

  18. Retinopatia da prematuridade: achados refrativos pós-tratamento com crioterapia ou laser Retinopathy of prematurity: refractive errors in patients treated with cryotherapy or laser

    Directory of Open Access Journals (Sweden)

    Sara Pozzi

    2000-10-01

    Full Text Available Objetivos: Determinar e comparar as características refrativas de uma população composta de crianças pré-termo com retinopatia da prematuridade que necessitaram de tratamento com crioterapia ou laserterapia. Método: Análise dos resultados da refração estática de 14 pacientes (de um total de 761 fichas de crianças que nasceram no Hospital São Paulo da Universidade Federal de São Paulo - Escola Paulista de Medicina, entre janeiro de 1988 e abril de 1998, que completaram um ano de idade e que apresentaram Retinopatia da Prematuridade grau 3 com características de "doença limiar" sendo tratadas com crioterapia ou laserterapia. Foram utilizados os testes estatísticos de Wilcoxon e Mann-Whitney para a avaliação dos resultados. Resultados: 64,3% dos pacientes apresentaram miopia. No grupo de pacientes que receberam tratamento com crioterapia, 80% mostrou miopia, que em todos os casos foi alta; 20% hipermetropia leve, com uma média para o equivalente esférico de --3,10 D no olho direito e --3,25 D no olho esquerdo (diferença entre ambos os olhos estatísticamente não significante. No grupo de laserterapia, 55,6% mostrou miopia, sendo 20 % dos casos miopia alta e 80% miopia leve; 11,1% apresentou-se sem ametropia e 33,3 % com hipermetropia leve. O valor da média para o equivalente esférico foi --0,58 D no olho direito e --0,83D no olho esquerdo (diferença entre ambos os olhos estatisticamente significante. A comparação dos resultados refracionais dos dois grupos mostrou uma maior incidência para miopia alta no grupo de pacientes que receberam tratamento com crioterapia (PPurpose: To examine the spherical equivalent of refractive errors in preterm children with threshold retinopathy of prematurity treated with cryotherapy or laser. Patients and Method: A group of 14 one-year-old children (selected from 761 preterm children born at the Hospital São Paulo of the Universidade Federal de São Paulo between 1988 and 1998 with stage

  19. Residual set-up errors and margins in on-line image-guided prostate localization in radiotherapy

    DEFF Research Database (Denmark)

    Poulsen, Per Rugaard; Muren, Ludvig; Høyer, Morten

    2007-01-01

    BACKGROUND AND PURPOSE: Image-guided on-line correction of the target position allows radiotherapy of prostate cancer with narrow set-up margins. The present study investigated the residual set-up error after on-line prostate localization and its impact on margins. MATERIALS AND METHODS: Prostate...... localization based on two orthogonal X-ray images of gold markers implanted in the prostate was performed with an on-board imager at four treatment sessions for 90 patients. The set-up error in the sagittal plane residual after couch adjustment was evaluated on lateral verification portal images. RESULTS...

  20. A residual-based a posteriori error estimator for single-phase Darcy flow in fractured porous media

    KAUST Repository

    Chen, Huangxin

    2016-12-09

    In this paper we develop an a posteriori error estimator for a mixed finite element method for single-phase Darcy flow in a two-dimensional fractured porous media. The discrete fracture model is applied to model the fractures by one-dimensional fractures in a two-dimensional domain. We consider Raviart–Thomas mixed finite element method for the approximation of the coupled Darcy flows in the fractures and the surrounding porous media. We derive a robust residual-based a posteriori error estimator for the problem with non-intersecting fractures. The reliability and efficiency of the a posteriori error estimator are established for the error measured in an energy norm. Numerical results verifying the robustness of the proposed a posteriori error estimator are given. Moreover, our numerical results indicate that the a posteriori error estimator also works well for the problem with intersecting fractures.

  1. Genetic properties of residual feed intakes for maintenance and growth and the implications of error measurement.

    Science.gov (United States)

    Rekaya, R; Aggrey, S E

    2015-03-01

    A procedure for estimating residual feed intake (RFI) based on information used in feeding studies is presented. Koch's classical model consists of using fixed regressions of feed intake on metabolic BW and growth, and RFI is obtained as the deviation between the observed feed intake and the expected intake for an individual with a given weight and growth rate. Estimated RFI following such a procedure intrinsically suffers from the inability to separate true RFI from the sampling error. As the latter is never equal to 0, estimated RFI is always biased, and the magnitude of such bias depends on the ratio between the true RFI variance and the residual variance. Additionally, the classical approach suffers from its inability to dissect RFI into its biological components, being the metabolic efficiency (maintaining BW) and growth efficiency. To remedy these problems we proposed a procedure that directly models the individual animal variation in feed efficiency used for body maintenance and growth. The proposed model is an extension of Koch's procedure by assuming animal-specific regression coefficients rather than population-level parameters. To evaluate the performance of both models, a data simulation was performed using the structure of an existing chicken data set consisting of 2,289 records. Data was simulated using 4 ratios between the true RFI and sampling error variances (1:1, 2:1, 4:1, and 10:1) and 5 correlation values between the 2 animal-specific random regression coefficients (-0.95, -0.5, 0, 0.5, and 0.95). The results clearly showed the superiority of the proposed model compared to Koch's procedure under all 20 simulation scenarios. In fact, when the ratio was 1:1 and the true genetic correlation was equal to -0.95, the correlation between the true and estimated RFI for animals in the top 20% was 0.60 and 0.51 for the proposed and Koch's models, respectively. This is an 18% superiority for the proposed model. For the bottom 20% of animals in the ranking

  2. Surgical Options for the Refractive Correction of Keratoconus: Myth or Reality

    Directory of Open Access Journals (Sweden)

    L. Fernández-Vega-Cueto

    2017-01-01

    Full Text Available Keratoconus provides a decrease of quality of life to the patients who suffer from it. The treatment used as well as the method to correct the refractive error of these patients may influence on the impact of the disease on their quality of life. The purpose of this review is to describe the evidence about the conservative surgical treatment for keratoconus aiming to therapeutic and refractive effect. The visual rehabilitation for keratoconic corneas requires addressing three concerns: halting the ectatic process, improving corneal shape, and minimizing the residual refractive error. Cross-linking can halt the disease progression, intrastromal corneal ring segments can improve the corneal shape and hence the visual quality and reduce the refractive error, PRK can correct mild-moderate refractive error, and intraocular lenses can correct from low to high refractive error associated with keratoconus. Any of these surgical options can be performed alone or combined with the other techniques depending on what the case requires. Although it could be considered that the surgical option for the refracto-therapeutic treatment of the keratoconus is a reality, controlled, randomized studies with larger cohorts and longer follow-up periods are needed to determine which refractive procedure and/or sequence are most suitable for each case.

  3. The accuracy of multimeridional refraction.

    Science.gov (United States)

    Long, W F

    1981-12-01

    The accuracy of meridional refraction using equally spaced preselected meridians was investigated by using populations of computer-simulated patients. The number of meridians refracted, patient refractive error, and the coarseness of phoroptor steps were varied. Results indicate that the accuracy of meridional refraction is independent of the relative orientation of the axis of the patient's astigmatism and the preselected meridians, that little is to be gained by use of a phoropter with steps finer than the usual 0.25 D, and that with a sufficient number of meridians, meridional refraction can be as accurate as more conventional techniques.

  4. Minimization and Mitigation of Wire EDM Cutting Errors in the Application of the Contour Method of Residual Stress Measurement

    Science.gov (United States)

    Ahmad, Bilal; Fitzpatrick, Michael E.

    2016-01-01

    The contour method of residual stress measurement relies on the careful application of wire electro-discharge machining (WEDM) for the cutting stage. Changes in material removal rates during the cut lead to errors in the final calculated values of residual stress. In this study, WEDM cutting parameters have been explored to identify the optimum conditions for contour method residual stress measurements. The influence of machine parameters on the surface roughness and cutting artifacts in the contour cut is discussed. It has been identified that the critical parameter in improving the surface finish is the spark pulse duration. A typical cutting artifact and its impact on measured stress values have been identified and demonstrated for a contour cut in a welded marine steel. A procedure is presented to correct contour displacement data from the influence of WEDM cutting artifacts, and is demonstrated on the correction of a measured weld residual stress. The corrected contour method improved the residual stress magnitude up to 150 MPa. The corrected contour method results were validated by X-ray diffraction, incremental center hole drilling, and neutron diffraction.

  5. Topography-modified refraction (TMR): adjustment of treated cylinder amount and axis to the topography versus standard clinical refraction in myopic topography-guided LASIK.

    Science.gov (United States)

    Kanellopoulos, Anastasios John

    2016-01-01

    To evaluate the safety, efficacy, and contralateral eye comparison of topography-guided myopic LASIK with two different refraction treatment strategies. Private clinical ophthalmology practice. A total of 100 eyes (50 patients) in consecutive cases of myopic topography-guided LASIK procedures with the same refractive platform (FS200 femtosecond and EX500 excimer lasers) were randomized for treatment as follows: one eye with the standard clinical refraction (group A) and the contralateral eye with the topographic astigmatic power and axis (topography-modified treatment refraction; group B). All cases were evaluated pre- and post-operatively for the following parameters: refractive error, best corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), topography (Placido-disk based) and tomography (Scheimpflug-image based), wavefront analysis, pupillometry, and contrast sensitivity. Follow-up visits were conducted for at least 12 months. Mean refractive error was -5.5 D of myopia and -1.75 D of astigmatism. In group A versus group B, respectively, the average UDVA improved from 20/200 to 20/20 versus 20/16; post-operative CDVA was 20/20 and 20/13.5; 1 line of vision gained was 27.8% and 55.6%; and 2 lines of vision gained was 5.6% and 11.1%. In group A, 27.8% of eyes had over -0.50 diopters of residual refractive astigmatism, in comparison to 11.7% in group B ( P Topography-modified refraction (TMR): topographic adjustment of the amount and axis of astigmatism treated, when different from the clinical refraction, may offer superior outcomes in topography-guided myopic LASIK. These findings may change the current clinical paradigm of the optimal subjective refraction utilized in laser vision correction.

  6. Topography-modified refraction (TMR: adjustment of treated cylinder amount and axis to the topography versus standard clinical refraction in myopic topography-guided LASIK

    Directory of Open Access Journals (Sweden)

    Kanellopoulos AJ

    2016-11-01

    Full Text Available Anastasios John Kanellopoulos1,2 1LaserVision Clinical and Research Institute, Athens, Greece; 2Department of Ophthalmology, NYU Medical School, New York, NY, USA Purpose: To evaluate the safety, efficacy, and contralateral eye comparison of topography-guided myopic LASIK with two different refraction treatment strategies. Setting: Private clinical ophthalmology practice. Patients and methods: A total of 100 eyes (50 patients in consecutive cases of myopic topography-guided LASIK procedures with the same refractive platform (FS200 femtosecond and EX500 excimer lasers were randomized for treatment as follows: one eye with the standard clinical refraction (group A and the contralateral eye with the topographic astigmatic power and axis (topography-modified treatment refraction; group B. All cases were evaluated pre- and post-operatively for the following parameters: refractive error, best corrected distance visual acuity (CDVA, uncorrected distance visual acuity (UDVA, topography (Placido-disk based and tomography (Scheimpflug-image based, wavefront analysis, pupillometry, and contrast sensitivity. Follow-up visits were conducted for at least 12 months. Results: Mean refractive error was -5.5 D of myopia and -1.75 D of astigmatism. In group A versus group B, respectively, the average UDVA improved from 20/200 to 20/20 versus 20/16; post-operative CDVA was 20/20 and 20/13.5; 1 line of vision gained was 27.8% and 55.6%; and 2 lines of vision gained was 5.6% and 11.1%. In group A, 27.8% of eyes had over -0.50 diopters of residual refractive astigmatism, in comparison to 11.7% in group B (P<0.01. The residual percentages in both groups were measured with refractive astigmatism of more than –0.5 diopters. Conclusion: Topography-modified refraction (TMR: topographic adjustment of the amount and axis of astigmatism treated, when different from the clinical refraction, may offer superior outcomes in topography-guided myopic LASIK. These findings

  7. Fitting correlated residual error structures in nonlinear mixed-effects models using SAS PROC NLMIXED.

    Science.gov (United States)

    Harring, Jeffrey R; Blozis, Shelley A

    2014-06-01

    Nonlinear mixed-effects (NLME) models remain popular among practitioners for analyzing continuous repeated measures data taken on each of a number of individuals when interest centers on characterizing individual-specific change. Within this framework, variation and correlation among the repeated measurements may be partitioned into interindividual variation and intraindividual variation components. The covariance structure of the residuals are, in many applications, consigned to be independent with homogeneous variances, [Formula: see text], not because it is believed that intraindividual variation adheres to this structure, but because many software programs that estimate parameters of such models are not well-equipped to handle other, possibly more realistic, patterns. In this article, we describe how the programmatic environment within SAS may be utilized to model residual structures for serial correlation and variance heterogeneity. An empirical example is used to illustrate the capabilities of the module.

  8. Refractive cylinder outcomes after calculating toric intraocular lens cylinder power using total corneal refractive power

    Directory of Open Access Journals (Sweden)

    Davison JA

    2015-08-01

    Full Text Available James A Davison,1 Richard Potvin21Wolfe Eye Clinic, Marshalltown, IA, USA; 2Science in Vision, Akron, NY, USAPurpose: To determine whether the total corneal refractive power (TCRP value, which is based on measurement of both anterior and posterior corneal astigmatism, is effective for toric intraocular lens (IOL calculation with AcrySof® Toric IOLsPatients and methods: A consecutive series of cataract surgery cases with AcrySof toric IOL implantation was studied retrospectively. The IOLMaster® was used for calculation of IOL sphere, the Pentacam® TCRP 3.0 mm apex/ring value was used as the keratometry input to the AcrySof Toric IOL Calculator and the VERION™ Digital Marker for surgical orientation. The keratometry readings from the VERION reference unit were recorded but not used in the actual calculation. Vector differences between expected and actual residual refractive cylinder were calculated and compared to simulated vector errors using the collected VERION keratometry data.Results: In total, 83 eyes of 56 patients were analyzed. Residual refractive cylinder was 0.25 D or lower in 58% of eyes and 0.5 D or lower in 80% of eyes. The TCRP-based calculation resulted in a statistically significantly lower vector error (P<0.01 and significantly more eyes with a vector error ≤0.5 D relative to the VERION-based calculation (P=0.02. The TCRP and VERION keratometry readings suggested a different IOL toric power in 53/83 eyes. In these 53 eyes the TCRP vector error was lower in 28 cases, the VERION error was lower in five cases, and the error was equal in 20 cases. When the anterior cornea had with-the-rule astigmatism, the VERION was more likely to suggest a higher toric power and when the anterior cornea had against-the-rule astigmatism, the VERION was less likely to suggest a higher toric power.Conclusion: Using the TCRP keratometry measurement in the AcrySof toric calculator may improve overall postoperative refractive results

  9. Residual sweeping errors in turbulent particle pair diffusion in a Lagrangian diffusion model.

    Directory of Open Access Journals (Sweden)

    Nadeem A Malik

    Full Text Available Thomson, D. J. & Devenish, B. J. [J. Fluid Mech. 526, 277 (2005] and others have suggested that sweeping effects make Lagrangian properties in Kinematic Simulations (KS, Fung et al [Fung J. C. H., Hunt J. C. R., Malik N. A. & Perkins R. J. J. Fluid Mech. 236, 281 (1992], unreliable. However, such a conclusion can only be drawn under the assumption of locality. The major aim here is to quantify the sweeping errors in KS without assuming locality. Through a novel analysis based upon analysing pairs of particle trajectories in a frame of reference moving with the large energy containing scales of motion it is shown that the normalized integrated error [Formula: see text] in the turbulent pair diffusivity (K due to the sweeping effect decreases with increasing pair separation (σl, such that [Formula: see text] as σl/η → ∞; and [Formula: see text] as σl/η → 0. η is the Kolmogorov turbulence microscale. There is an intermediate range of separations 1 < σl/η < ∞ in which the error [Formula: see text] remains negligible. Simulations using KS shows that in the swept frame of reference, this intermediate range is large covering almost the entire inertial subrange simulated, 1 < σl/η < 105, implying that the deviation from locality observed in KS cannot be atributed to sweeping errors. This is important for pair diffusion theory and modeling. PACS numbers: 47.27.E?, 47.27.Gs, 47.27.jv, 47.27.Ak, 47.27.tb, 47.27.eb, 47.11.-j.

  10. Impact of residual and intrafractional errors on strategy of correction for image-guided accelerated partial breast irradiation

    Directory of Open Access Journals (Sweden)

    Guo Xiao-Mao

    2010-10-01

    Full Text Available Abstract Background The cone beam CT (CBCT guided radiation can reduce the systematic and random setup errors as compared to the skin-mark setup. However, the residual and intrafractional (RAIF errors are still unknown. The purpose of this paper is to investigate the magnitude of RAIF errors and correction action levels needed in cone beam computed tomography (CBCT guided accelerated partial breast irradiation (APBI. Methods Ten patients were enrolled in the prospective study of CBCT guided APBI. The postoperative tumor bed was irradiated with 38.5 Gy in 10 fractions over 5 days. Two cone-beam CT data sets were obtained with one before and one after the treatment delivery. The CBCT images were registered online to the planning CT images using the automatic algorithm followed by a fine manual adjustment. An action level of 3 mm, meaning that corrections were performed for translations exceeding 3 mm, was implemented in clinical treatments. Based on the acquired data, different correction action levels were simulated, and random RAIF errors, systematic RAIF errors and related margins before and after the treatments were determined for varying correction action levels. Results A total of 75 pairs of CBCT data sets were analyzed. The systematic and random setup errors based on skin-mark setup prior to treatment delivery were 2.1 mm and 1.8 mm in the lateral (LR, 3.1 mm and 2.3 mm in the superior-inferior (SI, and 2.3 mm and 2.0 mm in the anterior-posterior (AP directions. With the 3 mm correction action level, the systematic and random RAIF errors were 2.5 mm and 2.3 mm in the LR direction, 2.3 mm and 2.3 mm in the SI direction, and 2.3 mm and 2.2 mm in the AP direction after treatments delivery. Accordingly, the margins for correction action levels of 3 mm, 4 mm, 5 mm, 6 mm and no correction were 7.9 mm, 8.0 mm, 8.0 mm, 7.9 mm and 8.0 mm in the LR direction; 6.4 mm, 7.1 mm, 7.9 mm, 9.2 mm and 10.5 mm in the SI direction; 7.6 mm, 7.9 mm, 9.4 mm, 10

  11. Excimer lasers for refractive surgery

    Science.gov (United States)

    Vartapetov, Serge K.

    2003-10-01

    Over the last decade excimer lasers have been broadly used for technological and medical processes. One of the most widespread applications of excimer laser is the clinical use for refractive surgery. Refractive surgery with excimer lasers is the prevalent method for the eye acuity correction. Operation at 193 nanometers, the excimer laser is able to precisely sculpt the corneal surface to correct refractive errors. Both the increase in the accuracy of sculpturing and the predictability of procedures are the key elements of the excimer laser designed for refractive surgery. The novel excimer laser for refractive surgery is offered for small aberration treatment. The excimer laser with both a full aperture Gaussian beam and fly spot system is described. The comparison of different systems of laser correction is reviewed.

  12. Diffraction grating strain gauge method: error analysis and its application for the residual stress measurement in thermal barrier coatings

    Science.gov (United States)

    Yin, Yuanjie; Fan, Bozhao; He, Wei; Dai, Xianglu; Guo, Baoqiao; Xie, Huimin

    2018-03-01

    Diffraction grating strain gauge (DGSG) is an optical strain measurement method. Based on this method, a six-spot diffraction grating strain gauge (S-DGSG) system has been developed with the advantages of high and adjustable sensitivity, compact structure, and non-contact measurement. In this study, this system is applied for the residual stress measurement in thermal barrier coatings (TBCs) combining the hole-drilling method. During the experiment, the specimen’s location is supposed to be reset accurately before and after the hole-drilling, however, it is found that the rigid body displacements from the resetting process could seriously influence the measurement accuracy. In order to understand and eliminate the effects from the rigid body displacements, such as the three-dimensional (3D) rotations and the out-of-plane displacement of the grating, the measurement error of this system is systematically analyzed, and an optimized method is proposed. Moreover, a numerical experiment and a verified tensile test are conducted, and the results verify the applicability of this optimized method successfully. Finally, combining this optimized method, a residual stress measurement experiment is conducted, and the results show that this method can be applied to measure the residual stress in TBCs.

  13. Development of an ice crystal scattering database for the global change observation mission/second generation global imager satellite mission: investigating the refractive index grid system and potential retrieval error.

    Science.gov (United States)

    Letu, Husi; Nakajima, Takashi Y; Matsui, Takashi N

    2012-09-01

    Computing time and retrieval error of the effective particle radius are important considerations when developing an ice crystal scattering database to be used in radiative transfer simulation and satellite remote sensing retrieval. Therefore, the light scattering database should be optimized based on the specifications of the satellite sensor. In this study, the grid system of the complex refractive index in the 1.6 μm (SW3) channel of the Global Change Observation Mission/Second Generation Global Imager satellite sensor is investigated for optimizing the ice crystal scattering database. This grid system is separated into twelve patterns according to the step size of the real and imaginary parts of the refractive index. Specifically, the LIght Scattering solver Applicable to particles of arbitrary Shape/Geometrical-Optics Approximation technique is used to simulate the scattering of light by randomly oriented large hexagonal ice crystals. The difference of radiance with different step size of the refractive index is calculated from the developed light scattering database using the radiative transfer (R-STAR) solver. The results indicated that the step size of the real part is a significant factor in difference of radiance.

  14. Imaging of the optic disc and retinal nerve fiber layer: the effects of age, optic disc area, refractive error, and gender

    Science.gov (United States)

    Bowd, Christopher; Zangwill, Linda M.; Blumenthal, Eytan Z.; Vasile, Cristiana; Boehm, Andreas G.; Gokhale, Parag A.; Mohammadi, Kourosh; Amini, Payam; Sankary, Timothy M.; Weinreb, Robert N.

    2002-01-01

    We cross-sectionally examined the relationship between age, optic disc area, refraction, and gender and optic disc topography and retinal nerve fiber layer (RNFL) measurements, using optical imaging techniques. One eye from each of 155 Caucasian subjects (age range 23.0-80.8 y) without ocular pathology was included. Measurements were obtained by using the Heidelberg Retina Tomography (HRT), the GDx Nerve Fiber Analyzer, and the Optical Coherence Tomograph (OCT). The effects of age were small (R2associated with most HRT parameters and isolated GDx and OCT parameters. Refraction and gender were not significantly associated with any optic disc or RNFL parameters. Although effects of age on the optic disc and RNFL are small, they should be considered in monitoring ocular disease. Optic disc area should be considered when cross-sectionally evaluating disc topography and, to a lesser extent, RNFL thickness.

  15. Energy dependent mesh adaptivity of discontinuous isogeometric discrete ordinate methods with dual weighted residual error estimators

    Science.gov (United States)

    Owens, A. R.; Kópházi, J.; Welch, J. A.; Eaton, M. D.

    2017-04-01

    In this paper a hanging-node, discontinuous Galerkin, isogeometric discretisation of the multigroup, discrete ordinates (SN) equations is presented in which each energy group has its own mesh. The equations are discretised using Non-Uniform Rational B-Splines (NURBS), which allows the coarsest mesh to exactly represent the geometry for a wide range of engineering problems of interest; this would not be the case using straight-sided finite elements. Information is transferred between meshes via the construction of a supermesh. This is a non-trivial task for two arbitrary meshes, but is significantly simplified here by deriving every mesh from a common coarsest initial mesh. In order to take full advantage of this flexible discretisation, goal-based error estimators are derived for the multigroup, discrete ordinates equations with both fixed (extraneous) and fission sources, and these estimators are used to drive an adaptive mesh refinement (AMR) procedure. The method is applied to a variety of test cases for both fixed and fission source problems. The error estimators are found to be extremely accurate for linear NURBS discretisations, with degraded performance for quadratic discretisations owing to a reduction in relative accuracy of the "exact" adjoint solution required to calculate the estimators. Nevertheless, the method seems to produce optimal meshes in the AMR process for both linear and quadratic discretisations, and is ≈×100 more accurate than uniform refinement for the same amount of computational effort for a 67 group deep penetration shielding problem.

  16. Visual Survey of Infantry Troops. Part 1. Visual Acuity, Refractive Status, Interpupillary Distance and Visual Skills

    Science.gov (United States)

    1989-06-01

    prevalence of refractive error types among infantrymen .............................. 35 15. 2ercentages of refractive errors by sphere and cylinder...not prescribing for a minimum amount. Table 14. Classification and prevalence of refractive error types among infantrymen Prevalence Refractive...with a 10 mm IPD difference was probably an accommodative esotrope. This five-plus diopter hyperope demonstrated left-eye amblyopia , 4 prism diopters

  17. The Residual Setup Errors of Different IGRT Alignment Procedures for Head and Neck IMRT and the Resulting Dosimetric Impact

    International Nuclear Information System (INIS)

    Graff, Pierre; Kirby, Neil; Weinberg, Vivian; Chen, Josephine; Yom, Sue S.; Lambert, Louise; Pouliot, Jean

    2013-01-01

    Purpose: To assess residual setup errors during head and neck radiation therapy and the resulting consequences for the delivered dose for various patient alignment procedures. Methods and Materials: Megavoltage cone beam computed tomography (MVCBCT) scans from 11 head and neck patients who underwent intensity modulated radiation therapy were used to assess setup errors. Each MVCBCT scan was registered to its reference planning kVCT, with seven different alignment procedures: automatic alignment and manual registration to 6 separate bony landmarks (sphenoid, left/right maxillary sinuses, mandible, cervical 1 [C1]-C2, and C7-thoracic 1 [T1] vertebrae). Shifts in the different alignments were compared with each other to determine whether there were any statistically significant differences. Then, the dose distribution was recalculated on 3 MVCBCT images per patient for every alignment procedure. The resulting dose-volume histograms for targets and organs at risk (OARs) were compared to those from the planning kVCTs. Results: The registration procedures produced statistically significant global differences in patient alignment and actual dose distribution, calling for a need for standardization of patient positioning. Vertically, the automatic, sphenoid, and maxillary sinuses alignments mainly generated posterior shifts and resulted in mean increases in maximal dose to OARs of >3% of the planned dose. The suggested choice of C1-C2 as a reference landmark appears valid, combining both OAR sparing and target coverage. Assuming this choice, relevant margins to apply around volumes of interest at the time of planning to take into account for the relative mobility of other regions are discussed. Conclusions: Use of different alignment procedures for treating head and neck patients produced variations in patient setup and dose distribution. With concern for standardizing practice, C1-C2 reference alignment with relevant margins around planning volumes seems to be a valid

  18. Adenine Enrichment at the Fourth CDS Residue in Bacterial Genes Is Consistent with Error Proofing for +1 Frameshifts.

    Science.gov (United States)

    Abrahams, Liam; Hurst, Laurence D

    2017-12-01

    Beyond selection for optimal protein functioning, coding sequences (CDSs) are under selection at the RNA and DNA levels. Here, we identify a possible signature of "dual-coding," namely extensive adenine (A) enrichment at bacterial CDS fourth sites. In 99.07% of studied bacterial genomes, fourth site A use is greater than expected given genomic A-starting codon use. Arguing for nucleotide level selection, A-starting serine and arginine second codons are heavily utilized when compared with their non-A starting synonyms. Several models have the ability to explain some of this trend. In part, A-enrichment likely reduces 5' mRNA stability, promoting translation initiation. However T/U, which may also reduce stability, is avoided. Further, +1 frameshifts on the initiating ATG encode a stop codon (TGA) provided A is the fourth residue, acting either as a frameshift "catch and destroy" or a frameshift stop and adjust mechanism and hence implicated in translation initiation. Consistent with both, genomes lacking TGA stop codons exhibit weaker fourth site A-enrichment. Sequences lacking a Shine-Dalgarno sequence and those without upstream leader genes, that may be more error prone during initiation, have greater utilization of A, again suggesting a role in initiation. The frameshift correction model is consistent with the notion that many genomic features are error-mitigation factors and provides the first evidence for site-specific out of frame stop codon selection. We conjecture that the NTG universal start codon may have evolved as a consequence of TGA being a stop codon and the ability of NTGA to rapidly terminate or adjust a ribosome. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  19. The Residual Setup Errors of Different IGRT Alignment Procedures for Head and Neck IMRT and the Resulting Dosimetric Impact

    Energy Technology Data Exchange (ETDEWEB)

    Graff, Pierre [Department of Radiation-Oncology, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, California (United States); Radiation-Oncology, Alexis Vautrin Cancer Center, Vandoeuvre-Les-Nancy (France); Doctoral School BioSE (EA4360), Nancy (France); Kirby, Neil [Department of Radiation-Oncology, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, California (United States); Weinberg, Vivian [Department of Radiation-Oncology, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, California (United States); Department of Biostatistics, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, California (United States); Chen, Josephine; Yom, Sue S. [Department of Radiation-Oncology, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, California (United States); Lambert, Louise [Department of Radiation-Oncology, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, California (United States); Radiation-Oncology, Montreal University Centre, Montreal (Canada); Pouliot, Jean, E-mail: jpouliot@radonc.ucsf.edu [Department of Radiation-Oncology, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, California (United States)

    2013-05-01

    Purpose: To assess residual setup errors during head and neck radiation therapy and the resulting consequences for the delivered dose for various patient alignment procedures. Methods and Materials: Megavoltage cone beam computed tomography (MVCBCT) scans from 11 head and neck patients who underwent intensity modulated radiation therapy were used to assess setup errors. Each MVCBCT scan was registered to its reference planning kVCT, with seven different alignment procedures: automatic alignment and manual registration to 6 separate bony landmarks (sphenoid, left/right maxillary sinuses, mandible, cervical 1 [C1]-C2, and C7-thoracic 1 [T1] vertebrae). Shifts in the different alignments were compared with each other to determine whether there were any statistically significant differences. Then, the dose distribution was recalculated on 3 MVCBCT images per patient for every alignment procedure. The resulting dose-volume histograms for targets and organs at risk (OARs) were compared to those from the planning kVCTs. Results: The registration procedures produced statistically significant global differences in patient alignment and actual dose distribution, calling for a need for standardization of patient positioning. Vertically, the automatic, sphenoid, and maxillary sinuses alignments mainly generated posterior shifts and resulted in mean increases in maximal dose to OARs of >3% of the planned dose. The suggested choice of C1-C2 as a reference landmark appears valid, combining both OAR sparing and target coverage. Assuming this choice, relevant margins to apply around volumes of interest at the time of planning to take into account for the relative mobility of other regions are discussed. Conclusions: Use of different alignment procedures for treating head and neck patients produced variations in patient setup and dose distribution. With concern for standardizing practice, C1-C2 reference alignment with relevant margins around planning volumes seems to be a valid

  20. Statistical tests against systematic errors in data sets based on the equality of residual means and variances from control samples: theory and applications.

    Science.gov (United States)

    Henn, Julian; Meindl, Kathrin

    2015-03-01

    Statistical tests are applied for the detection of systematic errors in data sets from least-squares refinements or other residual-based reconstruction processes. Samples of the residuals of the data are tested against the hypothesis that they belong to the same distribution. For this it is necessary that they show the same mean values and variances within the limits given by statistical fluctuations. When the samples differ significantly from each other, they are not from the same distribution within the limits set by the significance level. Therefore they cannot originate from a single Gaussian function in this case. It is shown that a significance cutoff results in exactly this case. Significance cutoffs are still frequently used in charge-density studies. The tests are applied to artificial data with and without systematic errors and to experimental data from the literature.

  1. A multi-sensor burned area algorithm for crop residue burning in northwestern India: validation and sources of error

    Science.gov (United States)

    Liu, T.; Marlier, M. E.; Karambelas, A. N.; Jain, M.; DeFries, R. S.

    2017-12-01

    A leading source of outdoor emissions in northwestern India comes from crop residue burning after the annual monsoon (kharif) and winter (rabi) crop harvests. Agricultural burned area, from which agricultural fire emissions are often derived, can be poorly quantified due to the mismatch between moderate-resolution satellite sensors and the relatively small size and short burn period of the fires. Many previous studies use the Global Fire Emissions Database (GFED), which is based on the Moderate Resolution Imaging Spectroradiometer (MODIS) burned area product MCD64A1, as an outdoor fires emissions dataset. Correction factors with MODIS active fire detections have previously attempted to account for small fires. We present a new burned area classification algorithm that leverages more frequent MODIS observations (500 m x 500 m) with higher spatial resolution Landsat (30 m x 30 m) observations. Our approach is based on two-tailed Normalized Burn Ratio (NBR) thresholds, abbreviated as ModL2T NBR, and results in an estimated 104 ± 55% higher burned area than GFEDv4.1s (version 4, MCD64A1 + small fires correction) in northwestern India during the 2003-2014 winter (October to November) burning seasons. Regional transport of winter fire emissions affect approximately 63 million people downwind. The general increase in burned area (+37% from 2003-2007 to 2008-2014) over the study period also correlates with increased mechanization (+58% in combine harvester usage from 2001-2002 to 2011-2012). Further, we find strong correlation between ModL2T NBR-derived burned area and results of an independent survey (r = 0.68) and previous studies (r = 0.92). Sources of error arise from small median landholding sizes (1-3 ha), heterogeneous spatial distribution of two dominant burning practices (partial and whole field), coarse spatio-temporal satellite resolution, cloud and haze cover, and limited Landsat scene availability. The burned area estimates of this study can be used to build

  2. REFRACTIVE NEUTRON LENS

    OpenAIRE

    Petrov, P. V.; Kolchevsky, N. N.

    2013-01-01

    Compound concave refractive lenses are used for focusing neutron beam. Investigations of spectral and focusing properties of a refractive neutron lens are presented. Resolution of the imaging system on the base of refractive neutron lenses depends on material properties and parameters of neutron source. Model of refractive neutron lens are proposed. Results of calculation diffraction resolution and focal depth of refractive neutron lens are discussed.

  3. Intelligent Planning for Laser Refractive Surgeries

    Science.gov (United States)

    Wang, Wei; Yue, Yong; Elsheikh, Ahmed; Bao, Fangjun

    2018-02-01

    Refractive error is one of leading ophthalmic diseases for both genders all over the world. Laser refractive correction surgery, e.g., laser in-situ keratomileusis (LASIK), has been commonly used worldwide. The prediction of surgical parameters, e.g., corneal ablation depth, depends on the doctor’s experience, theoretical formula and surgery reference manual in the preoperative diagnosis. The error of prediction may present a potential surgical risk and complication. Being aware of the surgery parameters is important because these can be used to estimate a patient’s post-operative visual quality and help the surgeon plan a suitable treatment. Therefore, in this paper we discuss data mining techniques that can be utilized for the prediction of laser refractive correction surgery parameters. It can provide the surgeon with a reference for possible surgical parameters and outcomes of the patient before the laser refractive correction surgery.

  4. RADIO REFRACTIVITY RADIO REFRACTIVITY STUDY IN AKURE ...

    African Journals Online (AJOL)

    eobe

    P. O. Otasowie. O. Otasowie1,* and F. O. Edeko2. 1, 2 DEPT. OF ELECTRICAL AND ELECTRONIC ENGINEERING, UNIVERSITY OF BENIN, BENIN CITY, EDO ... refractivity gradient is thus defined as: ∆. ∆. (4). Refractivity gradients change with time leading to anomalous propagation conditions. There is a convenient ...

  5. Autofocus Correction of Azimuth Phase Error and Residual Range Cell Migration in Spotlight SAR Polar Format Imagery

    OpenAIRE

    Mao, Xinhua; Zhu, Daiyin; Zhu, Zhaoda

    2012-01-01

    Synthetic aperture radar (SAR) images are often blurred by phase perturbations induced by uncompensated sensor motion and /or unknown propagation effects caused by turbulent media. To get refocused images, autofocus proves to be useful post-processing technique applied to estimate and compensate the unknown phase errors. However, a severe drawback of the conventional autofocus algorithms is that they are only capable of removing one-dimensional azimuth phase errors (APE). As the resolution be...

  6. Residual position errors of lymph node surrogates in breast cancer adjuvant radiotherapy: Comparison of two arm fixation devices and the effect of arm position correction

    International Nuclear Information System (INIS)

    Kapanen, Mika; Laaksomaa, Marko; Skyttä, Tanja; Haltamo, Mikko; Pehkonen, Jani; Lehtonen, Turkka; Kellokumpu-Lehtinen, Pirkko-Liisa; Hyödynmaa, Simo

    2016-01-01

    Residual position errors of the lymph node (LN) surrogates and humeral head (HH) were determined for 2 different arm fixation devices in radiotherapy (RT) of breast cancer: a standard wrist-hold (WH) and a house-made rod-hold (RH). The effect of arm position correction (APC) based on setup images was also investigated. A total of 113 consecutive patients with early-stage breast cancer with LN irradiation were retrospectively analyzed (53 and 60 using the WH and RH, respectively). Residual position errors of the LN surrogates (Th1-2 and clavicle) and the HH were investigated to compare the 2 fixation devices. The position errors and setup margins were determined before and after the APC to investigate the efficacy of the APC in the treatment situation. A threshold of 5 mm was used for the residual errors of the clavicle and Th1-2 to perform the APC, and a threshold of 7 mm was used for the HH. The setup margins were calculated with the van Herk formula. Irradiated volumes of the HH were determined from RT treatment plans. With the WH and the RH, setup margins up to 8.1 and 6.7 mm should be used for the LN surrogates, and margins up to 4.6 and 3.6 mm should be used to spare the HH, respectively, without the APC. After the APC, the margins of the LN surrogates were equal to or less than 7.5/6.0 mm with the WH/RH, but margins up to 4.2/2.9 mm were required for the HH. The APC was needed at least once with both the devices for approximately 60% of the patients. With the RH, irradiated volume of the HH was approximately 2 times more than with the WH, without any dose constraints. Use of the RH together with the APC resulted in minimal residual position errors and setup margins for all the investigated bony landmarks. Based on the obtained results, we prefer the house-made RH. However, more attention should be given to minimize the irradiation of the HH with the RH than with the WH.

  7. Repeatability of subjective and objective refraction.

    Science.gov (United States)

    Rosenfield, M; Chiu, N N

    1995-08-01

    Although several studies have examined the repeatability of objective refraction, data concerning the repeatability of subjective refraction under masked conditions, i.e., where the examiner is unaware of the refractive results, are limited. Accordingly, the present study compared the variability of both subjective and objective refractive techniques. Refractive error was measured in 12 subjects on 5 separate occasions. Conventional subjective procedures were used, with the exception that the sphere power scale on the phoropter was covered so that the examiner was unaware of the final result. Objective measurements were obtained using a Canon Autoref R-1 infrared autorefractor. The standard deviation (SD) of the five examinations was calculated for each individual and the mean values for the population sample determined. The mean SD's for the subjective and objective techniques were +/- 0.14 and +/- 0.18 D, indicating 95% confidence limits of +/- 0.27 and +/- 0.35 D, respectively. It is concluded that with either assessment technique, a change in refractive error of at least +/- 0.50 D should be adopted as the minimum significant shift in refractive status.

  8. Refractive index measurement based on confocal method

    Science.gov (United States)

    An, Zhe; Xu, XiPing; Yang, JinHua; Qiao, Yang; Liu, Yang

    2017-10-01

    The development of transparent materials is closed to optoelectronic technology. It plays an increasingly important role in various fields. It is not only widely used in optical lens, optical element, optical fiber grating, optoelectronics, but also widely used in the building material, pharmaceutical industry with vessel, aircraft windshield and daily wear glasses.Regard of solving the problem of refractive index measurement in optical transparent materials. We proposed that using the polychromatic confocal method to measuring the refractive index of transparent materials. In this article, we describes the principle of polychromatic confocal method for measuring the refractive index of glass,and sketched the optical system and its optimization. Then we establish the measurement model of the refractive index, and set up the experimental system. In this way, the refractive index of the glass has been calibrated for refractive index experiment. Due to the error in the experimental process, we manipulated the experiment data to compensate the refractive index measurement formula. The experiment taking the quartz glass for instance. The measurement accuracy of the refractive index of the glass is +/-1.8×10-5. This method is more practical and accurate, especially suitable for non-contact measurement occasions, which environmental requirements is not high. Environmental requirements are not high, the ordinary glass production line up to the ambient temperature can be fully adapted. There is no need for the color of the measured object that you can measure the white and a variety of colored glass.

  9. Assessment of residual error in liver position using kV cone-beam computed tomography for liver cancer high-precision radiation therapy

    International Nuclear Information System (INIS)

    Hawkins, Maria A.; Brock, Kristy K.; Eccles, Cynthia; Moseley, Douglas; Jaffray, David; Dawson, Laura A.

    2006-01-01

    Purpose: To evaluate the residual error in liver position using breath-hold kilovoltage (kV) cone-beam computed tomography (CT) following on-line orthogonal megavoltage (MV) image-guided breath-hold liver cancer conformal radiotherapy. Methods and Materials: Thirteen patients with liver cancer treated with 6-fraction breath-hold conformal radiotherapy were investigated. Before each fraction, orthogonal MV images were obtained during exhale breath-hold, with repositioning for offsets >3 mm, using the diaphragm for cranio-caudal (CC) alignment and vertebral bodies for medial-lateral (ML) and anterior posterior (AP) alignment. After repositioning, repeat orthogonal MV images, orthogonal kV fluoroscopic movies, and kV cone-beam CTs were obtained in exhale breath-hold. The cone-beam CT livers were registered to the planning CT liver to obtain the residual setup error in liver position. Results: After repositioning, 78 orthogonal MV image pairs, 61 orthogonal kV image pairs, and 72 kV cone-beam CT scans were obtained. Population random setup errors (σ) in liver position were 2.7 mm (CC), 2.3 mm (ML), and 3.0 mm (AP), and systematic errors (Σ) were 1.1 mm, 1.9 mm, and 1.3 mm in the superior, medial, and posterior directions. Liver offsets >5 mm were observed in 33% of cases; offsets >10 mm and liver deformation >5 mm were observed in a minority of patients. Conclusions: Liver position after radiation therapy guided with MV orthogonal imaging was within 5 mm of planned position in the majority of patients. kV cone-beam CT image guidance should improve accuracy with reduced dose compared with orthogonal MV image guidance for liver cancer radiation therapy

  10. Biometria ocular, erro refrativo e sua relação com a estatura, idade, sexo e escolaridade em adultos brasileiros Ocular biometry, refractive error and correlation with height, age, gender and years of formal education

    Directory of Open Access Journals (Sweden)

    Graziela Campanelli Pereira

    2007-06-01

    Full Text Available OBJETIVO: Avaliar os parâmetros biométricos oculares e o erro refrativo em adultos brasileiros e a sua relação com a estatura, idade, sexo e escolaridade. MÉTODOS: Estudo transversal que avaliou 173 indivíduos pela ceratometria, ecobiometria, refração e aferição da estatura. A análise estatística foi realizada pelo coeficiente de Pearson e pela elaboração de um modelo de regressão. RESULTADOS: Encontrou-se que: a cada aumento de 10 cm na estatura, esperar-se-ia encontrar um comprimento axial 0,32 mm mais longo, profundidade da câmara anterior 0,07 mm mais profunda, profundidade da cavidade vítrea 0,26 mm mais profunda e ceratometria 0,50 D mais plana; a cada aumento de 10 anos na idade esperar-se-ia encontrar profundidade da câmara anterior 0,15 mm mais rasa, cristalino 0,25 mm mais espesso, profundidade da cavidade vítrea 0,21 mm mais rasa e equivalente esférico 0,23 D mais positivo; a cada 10 anos de escolaridade esperar-se-ia equivalente esférico 0,74 D mais negativo. O sexo não apresentou influência. Equações referentes aos parâmetros biométricos e ao equivalente esférico foram formuladas. CONCLUSÕES: Correlações positivas foram encontradas entre: comprimento axial e estatura; profundidade da câmara anterior e da cavidade vítrea e estatura; espessura do cristalino e idade; ceratometria e estatura; equivalente esférico e idade. Correlações negativas foram encontradas entre: profundidade de câmara anterior e da cavidade vítrea e idade; equivalente esférico e escolaridade.PURPOSE: To assess ocular biometric parameters and refractive error in Brazilian adults and their relationship with height, age, gender and years of formal education. METHODS: Cross-sectional study that assessed 173 subjects by keratometry, echobiometry, refraction and measurement of body height. The statistical analysis was performed using Pearson's coefficient and a regression model was constructed. RESULTS: The correlations found were

  11. Sensitivity analysis of crustal correction and its error propagation to upper mantle residual gravity and density anomalies

    DEFF Research Database (Denmark)

    Herceg, Matija; Artemieva, Irina; Thybo, Hans

    2013-01-01

    We investigate the effect of the crustal structure heterogeneity and uncertainty in its determination on stripped gravity field. The analysis is based on interpretation of residual upper mantle gravity anomalies which are calculated by subtracting (stripping) the gravitational effect of the crust...... a relatively small range of expected density variations in the lithospheric mantle, knowledge on the uncertainties associated with incomplete knowledge of density structure of the crust is of utmost importance for further progress in such studies......) uncertainties in the velocity-density conversion and (ii) uncertainties in knowledge of the crustal structure (thickness and average Vp velocities of individual crustal layers, including the sedimentary cover). In this study, we address both sources of possible uncertainties by applying different conversions...... from velocity to density and by introducing variations into the crustal structure which corresponds to the uncertainty of its resolution by high-quality and low-quality seismic models. We examine the propagation of these uncertainties into determinations of lithospheric mantle density. The residual...

  12. Fully 3D refraction correction dosimetry system

    International Nuclear Information System (INIS)

    Manjappa, Rakesh; Makki, S Sharath; Kanhirodan, Rajan; Kumar, Rajesh; Vasu, Ram Mohan

    2016-01-01

    The irradiation of selective regions in a polymer gel dosimeter results in an increase in optical density and refractive index (RI) at those regions. An optical tomography-based dosimeter depends on rayline path through the dosimeter to estimate and reconstruct the dose distribution. The refraction of light passing through a dose region results in artefacts in the reconstructed images. These refraction errors are dependant on the scanning geometry and collection optics. We developed a fully 3D image reconstruction algorithm, algebraic reconstruction technique-refraction correction (ART-rc) that corrects for the refractive index mismatches present in a gel dosimeter scanner not only at the boundary, but also for any rayline refraction due to multiple dose regions inside the dosimeter. In this study, simulation and experimental studies have been carried out to reconstruct a 3D dose volume using 2D CCD measurements taken for various views. The study also focuses on the effectiveness of using different refractive-index matching media surrounding the gel dosimeter. Since the optical density is assumed to be low for a dosimeter, the filtered backprojection is routinely used for reconstruction. We carry out the reconstructions using conventional algebraic reconstruction (ART) and refractive index corrected ART (ART-rc) algorithms. The reconstructions based on FDK algorithm for cone-beam tomography has also been carried out for comparison. Line scanners and point detectors, are used to obtain reconstructions plane by plane. The rays passing through dose region with a RI mismatch does not reach the detector in the same plane depending on the angle of incidence and RI. In the fully 3D scanning setup using 2D array detectors, light rays that undergo refraction are still collected and hence can still be accounted for in the reconstruction algorithm. It is found that, for the central region of the dosimeter, the usable radius using ART-rc algorithm with water as RI matched

  13. Pattern of refractive anomalies in Warri Metropolis, Delta State of ...

    African Journals Online (AJOL)

    A cross-sectional prevalent study of refractive errors conducted in Warri, a metropolitan town in delta state of Nigeria revealed peculiar prevalent rates. One thousand and eighteen eyes of 6 to 64 year olds were screened for refractive anomalies and 752 (73.9%) eyes (369 male and 383 female eyes) were found with ...

  14. Atmospheric refraction : a history

    NARCIS (Netherlands)

    Lehn, WH; van der Werf, S

    2005-01-01

    We trace the history of atmospheric refraction from the ancient Greeks up to the time of Kepler. The concept that the atmosphere could refract light entered Western science in the second century B.C. Ptolemy, 300 years later, produced the first clearly defined atmospheric model, containing air of

  15. Parsimonious refraction interferometry

    KAUST Repository

    Hanafy, Sherif

    2016-09-06

    We present parsimonious refraction interferometry where a densely populated refraction data set can be obtained from just two shot gathers. The assumptions are that the first arrivals are comprised of head waves and direct waves, and a pair of reciprocal shot gathers is recorded over the line of interest. The refraction traveltimes from these reciprocal shot gathers can be picked and decomposed into O(N2) refraction traveltimes generated by N virtual sources, where N is the number of geophones in the 2D survey. This enormous increase in the number of virtual traveltime picks and associated rays, compared to the 2N traveltimes from the two reciprocal shot gathers, allows for increased model resolution and better condition numbers in the normal equations. Also, a reciprocal survey is far less time consuming than a standard refraction survey with a dense distribution of sources.

  16. Iterative supervirtual refraction interferometry

    KAUST Repository

    Al-Hagan, Ola

    2014-05-02

    In refraction tomography, the low signal-to-noise ratio (S/N) can be a major obstacle in picking the first-break arrivals at the far-offset receivers. To increase the S/N, we evaluated iterative supervirtual refraction interferometry (ISVI), which is an extension of the supervirtual refraction interferometry method. In this method, supervirtual traces are computed and then iteratively reused to generate supervirtual traces with a higher S/N. Our empirical results with both synthetic and field data revealed that ISVI can significantly boost up the S/N of far-offset traces. The drawback is that using refraction events from more than one refractor can introduce unacceptable artifacts into the final traveltime versus offset curve. This problem can be avoided by careful windowing of refraction events.

  17. Dosimetric effect of intrafraction motion and residual setup error for hypofractionated prostate intensity-modulated radiotherapy with online cone beam computed tomography image guidance.

    LENUS (Irish Health Repository)

    Adamson, Justus

    2012-02-01

    PURPOSE: To quantify the dosimetric effect and margins required to account for prostate intrafractional translation and residual setup error in a cone beam computed tomography (CBCT)-guided hypofractionated radiotherapy protocol. METHODS AND MATERIALS: Prostate position after online correction was measured during dose delivery using simultaneous kV fluoroscopy and posttreatment CBCT in 572 fractions to 30 patients. We reconstructed the dose distribution to the clinical tumor volume (CTV) using a convolution of the static dose with a probability density function (PDF) based on the kV fluoroscopy, and we calculated the minimum dose received by 99% of the CTV (D(99)). We compared reconstructed doses when the convolution was performed per beam, per patient, and when the PDF was created using posttreatment CBCT. We determined the minimum axis-specific margins to limit CTV D(99) reduction to 1%. RESULTS: For 3-mm margins, D(99) reduction was <\\/=5% for 29\\/30 patients. Using post-CBCT rather than localizations at treatment delivery exaggerated dosimetric effects by ~47%, while there was no such bias between the dose convolved with a beam-specific and patient-specific PDF. After eight fractions, final cumulative D(99) could be predicted with a root mean square error of <1%. For 90% of patients, the required margins were <\\/=2, 4, and 3 mm, with 70%, 40%, and 33% of patients requiring no right-left (RL), anteroposterior (AP), and superoinferior margins, respectively. CONCLUSIONS: For protocols with CBCT guidance, RL, AP, and SI margins of 2, 4, and 3 mm are sufficient to account for translational errors; however, the large variation in patient-specific margins suggests that adaptive management may be beneficial.

  18. The repeatability of automated and clinician refraction.

    Science.gov (United States)

    Bullimore, M A; Fusaro, R E; Adams, C W

    1998-08-01

    Auto-refractors are used as a starting point for clinicians' refractions and in studies of refractive error. We investigated the repeatability of the Hoya AR-570 and clinician refraction. Eighty-six subjects, aged 11 to 60 years, were recruited by mailing inquiries to 500 randomly selected patients who had received recent examinations at the University of California Optometric Eye Center. Contact lens wearers, patients with best corrected visual acuity worse than 20/30 in either eye, and patients with a history of diabetes were excluded. Each subject was examined by two clinicians during one visit. The first clinician obtained five auto-refractor readings for each eye (which were later averaged), performed a balanced subjective refraction (with spherical masking lenses in the phoropter), and repeated the automated refractor measurements. This protocol was then repeated by the second clinician. Clinicians were randomized with regard to testing order and masked to automated refractor results, each other's refractions, and previous spectacle prescriptions. To quantify repeatability, we used mixed model analyses of variance to estimate the appropriate variance components while accounting for the correlation among, for example, repeated measurements of the same eye. Astigmatic data were analyzed by converting into Fourier form: two cross-cylinders at axis 0 degrees (J0) and axis 45 degrees (J45). For mean spherical equivalent, the average difference between five averaged automated refractor readings, taken by two different optometrists, was +0.02 D (95% limits of agreement = -0.36 to +0.40 D). The average difference between the two optometrists' subjective refractions was -0.12 D (95% limits of agreement = -0.90 to +0.65 D). The 95% limits of agreement for the automated refractor were about half those of the clinician for both astigmatic terms (J0 and J45) and for all comparisons. Automated refraction is more repeatable than subjective refraction and therefore more

  19. Myopia onset and role of peripheral refraction

    Directory of Open Access Journals (Sweden)

    Rotolo M

    2017-06-01

    Full Text Available Maurilia Rotolo,1,2 Giancarlo Montani,2 Raul Martin1,3 1Optometry Research Group, IOBA Eye Institute, School of Optometry, Universidad de Valladolid, Valladolid, Spain; 2Optics and Optometry, Corso di Ottica e Optometria, Universita del Salento, Lecce, Italy; 3Faculty of Health and Human Sciences, School of Health Professions, Plymouth University, Peninsula Allied Health Centre, Plymouth, UK Background: To determine the peripheral refraction characteristics related to 18-month changes in refraction in Caucasian (Mediterranean children.Methods: Non-cycloplegic peripheral refraction at 10° intervals over the central ±30° of horizontal visual field over 18 months (baseline, 12 months, and 18 months of follow-up was conducted in 50 healthy children who were 8 years old. Axial length (AL was also recorded. Relative peripheral refraction (RPR was calculated and eyes were divided into three study groups: non-myopic eyes, myopic eyes, and eyes that develop myopia.Results: Myopic eyes showed hyperopic RPR and emetropic and hyperopic eyes showed myopic RPR. Univariate analysis of variance did not find any statistically significant effect of peripheral refraction (F36=0.13; P=1.00 and RPR (F36=0.79; P=0.80 on myopia onset (eyes that developed myopia along the study. All the studied groups showed an increase of AL, without statistically significant differences between the studied groups (F6=0.09; P=0.99.Conclusion: Hyperopic relative peripheral shift change in eyes that develop myopia has been found with differences in RPR between myopic (hyperopic RPR and hyperopic or emmetropic eyes (with myopic RPR. The results suggest that RPR cannot predict development or progression of myopia in Caucasian (Mediterranean children and the efficacy in slowing myopia progression obtained with treatments that manipulate the peripheral refraction is not just driven with RPR. Keywords: myopia, refractive errors, myopia onset, peripheral refraction, relative peripheral

  20. Erros de refração como causas de baixa visual em crianças da rede de escolas públicas da regional de Botucatu - SP Refractive errors as causes of visual impairment in children from public schools of the Botucatu region - SP

    Directory of Open Access Journals (Sweden)

    Claudia Akemi Shiratori de Oliveira

    2009-04-01

    Full Text Available OBJETIVO: Estudar a ocorrência dos erros refracionais em escolares de nosso meio. MÉTODOS: Estudo transversal avaliando crianças da pré-escola e do ensino básico, quanto ao sexo, tipo de erro refracional, acuidade visual e tratamento realizado. RESULTADOS: Quatro mil seiscentos e vinte e três crianças foram submetidas a exame de acuidade visual, das quais 8,1% apresentaram necessidade de exame oftalmológico completo. Houve 63,2% de portadores de astigmatismo hipermetrópico, 15,7% de astigmatismo miópico, 12,5% de astigmatismo misto, 4,9% de hipermetropia e 3,7% de miopia. Foi indicada a prescrição de lentes corretoras para 48,7% da amostra estudada. A frequência de erros refracionais na população foi de 3,9%. CONCLUSÃO: O astigmatismo hipermetrópico foi o erro de refracional mais frequente, havendo necessidade de tratamento em cerca de 50% das crianças triadas com frequência de 3,9% de erro refracional passível de correção na população de estudo.PURPOSE: To evaluate the refractive errors as cause of visual impairment in school children from the Botucatu region. METHODS: A sectional study was conducted evaluating preschool and elementary school students, according to gender, refractive error, visual acuity and treatment. RESULTS: Four thousand six hundred and twenty-three (4,623 children were submitted to visual acuity evaluation and 8.1% of them were submitted to complete ocular examination. There were 63.2% hyperopic astigmatism, 15.7% myopic astigmatism, 12.5% astigmatism, 4.9% hyperopia and 3.7% myopia. Corrective lenses were prescribed for 48.7% of the evaluated children. CONCLUSION: The most frequent refractive error was hyperopic astigmatism and 50% of the children received treatment. The frequency of refractive errors was 3.9% of the studied population.

  1. Photorefractive keratectomy in refractive accommodative esotropia.

    Science.gov (United States)

    Bilgihan, K; Akata, F; Or, M; Hasanreisoğlu, B

    1997-01-01

    Photorefractive keratectomy (PRK) was performed on a 19-year-old man with hyperopic astigmatism and refractive accommodative esotropia. The patient was orthophoric while wearing spectacles, but had an esotropia of 30 prism dioptres at near and distance vision without spectacles. The best corrected visual acuity of the right eye was 20/50 and of the left eye was 20/20. The excessive accommodative convergence of the patient was eliminated by correcting the hyperopic refractive error by performing PRK, and the patient became orthophoric after the treatment.

  2. Alternative Refractive Surgery Procedures

    Science.gov (United States)

    ... the epithelial cells. Once the epithelial flap is created and moved aside, the procedure is the same ... Sites EyeWiki International Society of Refractive Surgery * Required * First Name: * Last Name: Member ID: * Phone Number: * Email: * ...

  3. Pre- and Postcycloplegic Refractions in Children and Adolescents.

    Directory of Open Access Journals (Sweden)

    Dan Zhu

    Full Text Available To determine the difference between cycloplegic and non-cycloplegic refractive error and its associated factors in Chinese children and adolescents with a high prevalence of myopia.A school-based study including 1565 students aged 6 to 21 years was conducted in 2013 in Ejina, Inner Mongolia, China. Comprehensive eye examinations were performed. Pre-and postcycloplegic refractive error were measured using an auto-refractor. For cycloplegic refraction, one drop of topical 1.0% cyclopentolate was administered to each eye twice with a 5-minute interval and a third drop was administered 15 minutes after the second drop if the pupil size was less than 6 mm or if the pupillary light reflex was still present.Two drops of cyclopentolate were found to be sufficient in 59% of the study participants while the other 41% need an additional drop. The prevalence of myopia was 89.5% in participants aged over 12 years and 68.6% in those aged 12 years or younger (P<0.001. When myopia was defined as spherical equivalent (SE of less than -0.5 diopter (D, the prevalence estimates were 76.7% (95% confidence interval [CI] 74.6-78.8 and 54.1% (95%CI 51.6-56.6 before and after cycloplegic refraction, respectively. When hyperopia was defined as SE of more than 0.5D, the prevalence was only 2.8% (95%CI 1.9-3.6 before cycloplegic refraction while it was 15.5% (95%CI 13.7-17.3 after cycloplegic refraction. Increased difference between cycloplegic and non-cycloplegic refractive error was associated with decreased intraocular pressures (P = 0.01.Lack of cycloplegia in refractive error measurement was associated with significant misclassifications in both myopia and hyperopia among Chinese children and adolescents. Decreased intraocular pressure was related to a greater difference between cycloplegic and non-cycloplegic refractive error.

  4. Using residual stacking to mitigate site-specific errors in order to improve the quality of GNSS-based coordinate time series of CORS

    Science.gov (United States)

    Knöpfler, Andreas; Mayer, Michael; Heck, Bernhard

    2014-05-01

    Within the last decades, positioning using GNSS (Global Navigation Satellite Systems; e.g., GPS) has become a standard tool in many (geo-) sciences. The positioning methods Precise Point Positioning and differential point positioning based on carrier phase observations have been developed for a broad variety of applications with different demands for example on accuracy. In high precision applications, a lot of effort was invested to mitigate different error sources: the products for satellite orbits and satellite clocks were improved; the misbehaviour of satellite and receiver antennas compared to an ideal antenna is modelled by calibration values on absolute level, the modelling of the ionosphere and the troposphere is updated year by year. Therefore, within processing of data of CORS (continuously operating reference sites), equipped with geodetic hardware using a sophisticated strategy, the latest products and models nowadays enable positioning accuracies at low mm level. Despite the considerable improvements that have been achieved within GNSS data processing, a generally valid multipath model is still lacking. Therefore, site specific multipath still represents a major error source in precise GNSS positioning. Furthermore, the calibration information of receiving GNSS antennas, which is for instance derived by a robot or chamber calibration, is valid strictly speaking only for the location of the calibration. The calibrated antenna can show a slightly different behaviour at the CORS due to near field multipath effects. One very promising strategy to mitigate multipath effects as well as imperfectly calibrated receiver antennas is to stack observation residuals of several days, thereby, multipath-loaded observation residuals are analysed for example with respect to signal direction, to find and reduce systematic constituents. This presentation will give a short overview about existing stacking approaches. In addition, first results of the stacking approach

  5. The prevalence of refractive conditions in Puerto Rican adults attending an eye clinic system

    Directory of Open Access Journals (Sweden)

    Neisha M. Rodriguez

    2014-07-01

    Conclusion: Hyperopia is the most common refractive error and its prevalence and seems to increase among the aging population who visited the clinics. Further programs and studies must be developed to address the refractive errors needs of the adult Puerto Rican population.

  6. Impact of inter- and intrafraction deviations and residual set-up errors on PTV margins. Different alignment techniques in 3D conformal prostate cancer radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Langsenlehner, T.; Doeller, C.; Winkler, P.; Kapp, K.S. [Graz Medical Univ. (Austria). Dept. of Therapeutic Radiology and Oncology; Galle, G. [Graz Medical Univ. (Austria). Dept. of Urology

    2013-04-15

    The aim of this work was to analyze interfraction and intrafraction deviations and residual set-up errors (RSE) after online repositioning to determine PTV margins for 3 different alignment techniques in prostate cancer radiotherapy. The present prospective study included 44 prostate cancer patients with implanted fiducials treated with three-dimensional (3D) conformal radiotherapy. Daily localization was based on skin marks followed by marker detection using kilovoltage (kV) imaging and subsequent patient repositioning. Additionally, in-treatment megavoltage (MV) images were obtained for each treatment field. In an off-line analysis of 7,273 images, interfraction prostate motion, RSE after marker-based prostate localization, prostate position during each treatment session, and the effect of treatment time on intrafraction deviations were analyzed to evaluate PTV margins. Margins accounting for interfraction deviation, RSE and intrafraction motion were 14.1, 12.9, and 15.1 mm in anterior-posterior (AP), superior-inferior (SI), and left-right (LR) direction for skin mark alignment and 9.6, 8.7, and 2.6 mm for bony structure alignment, respectively. Alignment to implanted markers required margins of 4.6, 2.8, and 2.5 mm. As margins to account for intrafraction motion increased with treatment prolongation PTV margins could be reduced to 3.9, 2.6, and 2.4 mm if treatment time was {<=} 4 min. With daily online correction and repositioning based on implanted fiducials, a significant reduction of PTV margins can be achieved. The use of an optimized workflow with faster treatment techniques such as volumetric modulated arc techniques (VMAT) could allow for a further decrease. (orig.)

  7. Impact of inter- and intrafraction deviations and residual set-up errors on PTV margins. Different alignment techniques in 3D conformal prostate cancer radiotherapy.

    Science.gov (United States)

    Langsenlehner, T; Döller, C; Winkler, P; Gallé, G; Kapp, K S

    2013-04-01

    The aim of this work was to analyze interfraction and intrafraction deviations and residual set-up errors (RSE) after online repositioning to determine PTV margins for 3 different alignment techniques in prostate cancer radiotherapy. The present prospective study included 44 prostate cancer patients with implanted fiducials treated with three-dimensional (3D) conformal radiotherapy. Daily localization was based on skin marks followed by marker detection using kilovoltage (kV) imaging and subsequent patient repositioning. Additionally, in-treatment megavoltage (MV) images were obtained for each treatment field. In an off-line analysis of 7,273 images, interfraction prostate motion, RSE after marker-based prostate localization, prostate position during each treatment session, and the effect of treatment time on intrafraction deviations were analyzed to evaluate PTV margins. Margins accounting for interfraction deviation, RSE and intrafraction motion were 14.1, 12.9, and 15.1 mm in anterior-posterior (AP), superior-inferior (SI), and left-right (LR) direction for skin mark alignment and 9.6, 8.7, and 2.6 mm for bony structure alignment, respectively. Alignment to implanted markers required margins of 4.6, 2.8, and 2.5 mm. As margins to account for intrafraction motion increased with treatment prolongation PTV margins could be reduced to 3.9, 2.6, and 2.4 mm if treatment time was ≤ 4 min. With daily online correction and repositioning based on implanted fiducials, a significant reduction of PTV margins can be achieved. The use of an optimized workflow with faster treatment techniques such as volumetric modulated arc techniques (VMAT) could allow for a further decrease.

  8. Impact of inter- and intrafraction deviations and residual set-up errors on PTV margins. Different alignment techniques in 3D conformal prostate cancer radiotherapy

    International Nuclear Information System (INIS)

    Langsenlehner, T.; Doeller, C.; Winkler, P.; Kapp, K.S.; Galle, G.

    2013-01-01

    The aim of this work was to analyze interfraction and intrafraction deviations and residual set-up errors (RSE) after online repositioning to determine PTV margins for 3 different alignment techniques in prostate cancer radiotherapy. The present prospective study included 44 prostate cancer patients with implanted fiducials treated with three-dimensional (3D) conformal radiotherapy. Daily localization was based on skin marks followed by marker detection using kilovoltage (kV) imaging and subsequent patient repositioning. Additionally, in-treatment megavoltage (MV) images were obtained for each treatment field. In an off-line analysis of 7,273 images, interfraction prostate motion, RSE after marker-based prostate localization, prostate position during each treatment session, and the effect of treatment time on intrafraction deviations were analyzed to evaluate PTV margins. Margins accounting for interfraction deviation, RSE and intrafraction motion were 14.1, 12.9, and 15.1 mm in anterior-posterior (AP), superior-inferior (SI), and left-right (LR) direction for skin mark alignment and 9.6, 8.7, and 2.6 mm for bony structure alignment, respectively. Alignment to implanted markers required margins of 4.6, 2.8, and 2.5 mm. As margins to account for intrafraction motion increased with treatment prolongation PTV margins could be reduced to 3.9, 2.6, and 2.4 mm if treatment time was ≤ 4 min. With daily online correction and repositioning based on implanted fiducials, a significant reduction of PTV margins can be achieved. The use of an optimized workflow with faster treatment techniques such as volumetric modulated arc techniques (VMAT) could allow for a further decrease. (orig.)

  9. Refractive index based measurements

    DEFF Research Database (Denmark)

    2014-01-01

    In a method for performing a refractive index based measurement of a property of a fluid such as chemical composition or temperature by observing an apparent angular shift in an interference fringe pattern produced by back or forward scattering interferometry, ambiguities in the measurement caused...

  10. Refractive index based measurements

    DEFF Research Database (Denmark)

    2014-01-01

    In a method for performing a refractive index based measurement of a property of a fluid such as chemical composition or temperature, a chirp in the local spatial frequency of interference fringes of an interference pattern is reduced by mathematical manipulation of the recorded light intensity...

  11. Refractive index based measurements

    DEFF Research Database (Denmark)

    2014-01-01

    A refractive index based measurement of a property of a fluid is measured in an apparatus comprising a variable wavelength coherent light source (16), a sample chamber (12), a wavelength controller (24), a light sensor (20), a data recorder (26) and a computation apparatus (28), by - directing...

  12. Effect of interfacial refractive index on optical molecular orientation measurements.

    Science.gov (United States)

    Ekhoff, Jessica A; Rowlen, Kathy L

    2002-12-01

    The sensitivity of optical molecular orientation measurements to assumptions regarding thin film refractive index was investigated. Specifically, the influence of the interfacial refractive index on second harmonic generation (SHG) and linear dichroism measurements made in a total internal reflection (TIR) geometry was probed for five distinct molecular systems. The five molecular thin films ranged from weakly adsorbed species in equilibrium with solution to covalently bound molecules. Polarization data from the two techniques were fit using a range of assumed interfacial refractive indices. Surprisingly, a linear relationship between the difference in calculated apparent orientation angle and the difference in solvent-prism refractive index was observed. The trend indicates that for a TIR geometry, the error introduced by the thin film refractive index is negligible when the difference in solvent and prism refractive indices is less than approximately 0.08. However, there are clearly cases, such as a glass/air interface, in which assumptions regarding the thin film refractive index can result in significant error in the extracted orientation angle.

  13. Analytical models of optical refraction in the troposphere.

    Science.gov (United States)

    Nener, Brett D; Fowkes, Neville; Borredon, Laurent

    2003-05-01

    An extremely accurate but simple asymptotic description (with known error) is obtained for the path of a ray propagating over a curved Earth with radial variations in refractive index. The result is sufficiently simple that analytic solutions for the path can be obtained for linear and quadratic index profiles. As well as rendering the inverse problem trivial for these profiles, this formulation shows that images are uniformly magnified in the vertical direction when viewed through a quadratic refractive-index profile. Nonuniform vertical distortions occur for higher-order refractive-index profiles.

  14. Neutron microscope with refractive wedge

    International Nuclear Information System (INIS)

    Masalovich, S.V.

    1990-01-01

    A possibility of applying a refractive element in a mirror-neutron microscope using ultracold neutrons to reduce neutron aberrations is considered. Application of a refractive element in a neutron microscope with horizontal optical axis is studied. A scheme of neutron microscope with a refractive wedge is presented, evaluation of quartz wedge parameters is made. It is stressed that application of refractive elements in neutron microscopes facilitates aberration reduction in neutron-optical systems

  15. Refractive error changes in children with intermittent exotropia under overminus lens therapy Alterações nos vícios refracionais em crianças com exotropia intermitente submetidas ao tratamento por meio da hipercorreção com lentes negativas

    Directory of Open Access Journals (Sweden)

    Jayter Silva de Paula

    2009-12-01

    Full Text Available PURPOSE: Intermittent exotropia may be decreased by stimulation of accommodative convergence. Once excessive accommodation has been related to myopia, our objective was to evaluate refractive errors changes in children under overcorrecting minus lens therapy. METHODS: A retrospective chart review of 21 children with intermittent exotropia was performed. All patients were treated with occlusion, and a 13-patient subset of them received overminus lens therapy (group A. Eight children received spectacles as necessary (group B. Initial age, age interval, initial spherical equivalent (SE, and magnitude of overcorrection were considered as co-variables of the mean variation in refractive error (SE of each eye between groups, through a multivariate analysis. RESULTS: Overcorrection used in group A ranged from 0.5 D to 3.5 D (2.46 ± 0.87 D. Although initial SE of each eye was significant different between group A and B (OD - p=0.02; OS - p=0.01, initial age (p=0.69, age interval (p=0.90, and mean variation in refractive errors (p=0.36 did not differ between groups. Multivariate analysis with linear regression showed no significantly difference regarding all co-variables enrolled. CONCLUSIONS: Treatment of intermittent exotropia with overcorrecting minus lens did not induce refractive errors changes, even considering age, treatment period, initial spherical equivalent and overcorrection magnitude used.OBJETIVO: A exotropia intermitente pode ser diminuída pela estimulação da convergência acomodativa. Uma vez que uma acomodação excessiva tem sido relacionada à miopização, o objetivo deste trabalho foi o de avaliar alterações nos vícios de refração de crianças submetidas à hipercorreção com lentes negativas. MÉTODOS: Foi realizada revisão dos prontuários de 21 crianças com exotropia intermitente. Todos os pacientes foram tratados com oclusão, sendo que 13 deles foram submetidos à hipercorreção com lentes negativas (grupo A. As 8

  16. The AO SR IIItm Subjective Refraction System: comparison with Phoropter measures.

    Science.gov (United States)

    Woo, G C; Woodruff, M E

    1978-08-01

    Subjective measures of refractive error were obtained on 530 eyes using the AO SR III Subjective refraction System (operated by a trained secretary) and using a phoropter (operated by optometrists and optometry students) in a clinical setting. Comparison of these measures from the present study and from a previous study by Bannon leads us to conclude that the SR III instrument is capable of estimating refractive error with good agreement with conventional refractive methods. Comparison with the Acuity Systems 6600 Auto-RefractorTM was also made.

  17. Eye laterality: a comprehensive analysis in refractive surgery candidates.

    Science.gov (United States)

    Linke, Stephan J; Druchkiv, Vasyl; Steinberg, Johannes; Richard, Gisbert; Katz, Toam

    2013-08-01

    To explore eye laterality (higher refractive error in one eye) and its association with refractive state, spherical/astigmatic anisometropia, age and sex in refractive surgery candidates. Medical records of 12 493 consecutive refractive surgery candidates were filtered. Refractive error (subjective and cycloplegic) was measured in each subject and correlated with eye laterality. Only subjects with corrected distance visual acuity (CDVA) of >20/22 in each eye were enrolled to exclude amblyopia. Associations between eye laterality and refractive state were analysed by means of t-test, chi-squared test, Spearman's correlation and multivariate logistic regression analysis, respectively. There was no statistically significant difference in spherical equivalent between right (-3.47 ± 2.76 D) and left eyes (-3.47 ± 2.76 D, p = 0.510; Pearson's r = 0.948, p laterality for anisometropia >2.5 D in myopic (-5.64 ± 2.5 D versus -4.92 ± 2.6 D; p = 0.001) and in hyperopic (4.44 ± 1.69 D versus 3.04 ± 1.79 D; p = 0.025) subjects, (II) a tendency for left eye cylindrical laterality in myopic subjects, and (III) myopic male subjects had a higher prevalence of left eye laterality. (IV) Age did not show any significant impact on laterality. Over the full refractive spectrum, this study confirmed previously described strong interocular refractive correlation but revealed a statistically significant higher rate of right eye laterality for anisometropia >2.5 D. In general, our results support the use of data from one eye only in studies of ocular refraction. © 2013 The Authors. Acta Ophthalmologica © 2013 Acta Ophthalmologica Scandinavica Foundation.

  18. Patient age, refractive index of the corneal stroma, and outcomes of uneventful laser in situ keratomileusis.

    Science.gov (United States)

    Patel, Sudi; Alió, Jorge L; Walewska, Anna; Amparo, Francisco; Artola, Alberto

    2013-03-01

    To determine the influence of age and the corneal stromal refractive index on the difference between the predicted and actual postoperative refractive error after laser in situ keratomileusis (LASIK) and whether the precision of outcomes could be improved by considering age and the refractive index. Vissum Instituto Oftalmologico de Alicante, Alicante, Spain. Case series. Flaps were created using a mechanical microkeratome. The stromal refractive index was measured using a VCH-1 refractometer after flap lifting. Refractive data were obtained 1, 3, and 6 months postoperatively. Uneventful LASIK was performed in 133 eyes. The mean age, refractive index, and applied corrections were 33.4 years ± 9.49 (SD), 1.368 ± 0.006, and -2.43 ± 3.36 diopters (D), respectively. The difference between the predicted and actual postoperative refractive error = 2.315-0.021 age-1.106 refractive index (F = 3.647, r = 0.254, P=.029; n = 109) at 1 month and = 11.820-0.023 age-7.976 refractive index (F = 3.392, r = 0.261, P=.022, n = 106) at 3 months. A correlation between the actual and calculated postoperative refraction improved from r = -0.178 (P=.064; n = 75) to r = -0.418 (P0.50 D) of LASIK could be avoided by considering patient age and the refractive index and by adjusting the applied correction accordingly. Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  19. Human resources for refraction services in Central Nepal.

    Science.gov (United States)

    Kandel, Himal; Murthy, G V S; Bascaran, Covadonga

    2015-07-01

    Uncorrected refractive error is a public health problem globally and in Nepal. Planning of refraction services is hampered by a paucity of data. This study was conducted to determine availability and distribution of human resources for refraction, their efficiency, the type and extent of their training; the current service provision of refraction services and the unmet need in human resources for refraction in Central Nepal. This was a descriptive cross-sectional study. All refraction facilities in the Central Region were identified through an Internet search and interviews of key informants from the professional bodies and parent organisations of primary eye centres. A stratified simple random sampling technique was used to select 50 per cent of refraction facilities. The selected facilities were visited for primary data collection. Face-to-face interviews were conducted with the managers and the refractionists available in the facilities using a semi-structured questionnaire. Data was collected in 29 centres. All the managers (n=29; response rate 100 per cent) and 50 refractionists (Response rate 65.8 per cent) were interviewed. Optometrists and ophthalmic assistants were the main providers of refraction services (n=70, 92.11 per cent). They were unevenly distributed across the region, highly concentrated around urban areas. The median number of refractions per refractionist per year was 3,600 (IQR: 2,400 - 6,000). Interviewed refractionists stated that clients' knowledge, attitude and practice related factors such as lack of awareness of the need for refraction services and/or availability of existing services were the major barriers to the output of refraction services. The total number of refractions carried out in the Central Region per year was 653,176. An additional 170 refractionists would be needed to meet the unmet need of 1,323,234 refractions. The study findings demand a major effort to develop appropriately trained personnel when planning

  20. Long-term refractive change after intraocular lens implantation in childhood.

    Science.gov (United States)

    Walker, Randy A; Romanchuk, Kenneth G

    2006-08-01

    To determine refractive change occurring with age in children who had cataract removal with intraocular lens implantation and in whom the immediate postoperative refraction was targeted either to match the refractive error of the opposite eye in unilateral cases, or for only a small refractive error when surgery was bilateral. Retrospective review of the refractive error over time in 36 eyes of 25 children who underwent cataract removal (11 bilateral) with insertion of an intraocular lens from 1987 to 1998 and who had at least 4 years follow-up, but no glaucoma. Mean age at surgery was 5.5 years (median 5.7 y, range 1.3-12 y), with a mean follow-up of 8 years (median 6 y, range 4-16 y). The average refraction followed a logarithmic decline with age. Although eyes with unilateral surgery had a slightly faster rate of change and lower final refraction than did eyes with bilateral surgery, this difference was not statistically significant. Variation from this trend was also observed in 3 patients. When the hyperopic refractive error created immediately after surgery was small, children usually became significantly myopic when older, often creating anisometropic myopia in unilateral cases. When implanting intraocular lenses bilaterally one should aim for a significant but balanced hyperopic correction immediately postoperatively in young patients, anticipating that there will be emmetropization with aging. Parents should be warned that variations can occur.

  1. Refraction corrected calibration for aquatic locomotion research: application of Snell's law improves spatial accuracy

    NARCIS (Netherlands)

    Henrion, S.; Spoor, C.W.; Pieters, R.P.M.; Müller, U.K.; Leeuwen, van J.L.

    2015-01-01

    Images of underwater objects are distorted by refraction at the water–glass–air interfaces and these distortions can lead to substantial errors when reconstructing the objects' position and shape. So far, aquatic locomotion studies have minimized refraction in their experimental setups and used the

  2. Atmosphere Refraction Effects in Object Locating for Optical Satellite Remote Sensing Images

    Directory of Open Access Journals (Sweden)

    YAN Ming

    2015-09-01

    Full Text Available The collinear rigorous geometric model contains the atmosphere refraction geometric error in off-nadir observation. In order to estimate and correct the atmosphere refraction geometric error, the ISO international standard atmospheric model and Owens atmosphere refractive index algorithm are applied to calculate the index of atmosphere refraction in different latitude and altitude. The paper uses the weighted mean algorithm to reduce the eight layers ISO standard atmospheric model into a simple troposphere and stratosphere two layers spherical atmosphere. And the LOS vector track geometric algorithm is used to estimate the atmosphere refraction geometric error in different observation off-nadir angle. The results show that the atmosphere refraction will introduce about 2.5 m or 9 m geometric displacement in 30 or 45 degree off-nadir angle individual. Therefore, during geo-location processing of agile platform and extra wide high spatial resolution imagery, there is need to take into account the influence of atmosphere refraction and correct the atmosphere refraction geometric error to enhance the geo-location precision without GCPs.

  3. Refractive Correction In A Selected Adult Population In Isiala Ngwa ...

    African Journals Online (AJOL)

    This study was carried out to determine the types, distribution and frequency of refractive errors in adults in Isiala Ngwa South L.G.A. A 3-day vision screening program was carried out in November 2007 in which three hundred and forty two adults aged 40 to 80 years were screened for pathological conditions.The mean age ...

  4. Axial Length/Corneal Radius of Curvature Ratio and Refractive ...

    African Journals Online (AJOL)

    2017-12-05

    Dec 5, 2017 ... variously described as determined by the ocular biometric variables. There have been many studies on the relationship between refractive error and ocular axial length (AL), anterior chamber depth, corneal radius of curvature (CR), keratometric readings as well as other ocular biometric variables such as ...

  5. Refraction and Ocular Biometry of Preschool Children in Shanghai, China.

    Science.gov (United States)

    Zhang, Luoli; He, Xiangui; Qu, Xiaomei; You, Xiaofang; Wang, Bingjie; Shi, Huijing; Tan, Hui; Zou, Haidong; Zhu, Jianfeng

    2018-01-01

    To investigate the refraction and ocular biometry characteristics and to examine the prevalence of refractive errors in preschool children aged 3 to 6 years in Shanghai, China. A school-based cross-sectional study was conducted in Jiading and Xuhui District, Shanghai, in 2013. We randomly selected 7 kindergartens in Jiading District and 10 kindergartens in Xuhui District, with a probability proportionate to size. The children underwent comprehensive eye examinations, including cycloplegic refraction and biometric measurements. Myopia, hyperopia, astigmatism were defined as spherical equivalent (SE) ≤ -0.50 D, SE ≥ +2.00 D, and cylindrical diopters ≤ -1.00 D. The mean SE for 3- to 6-year-old children was +1.20 D (standard deviation [SD] 1.05), and the mean axial length (AL) was 22.29 mm (SD 0.73). The overall prevalence of myopia and astigmatism was 3.7% and 18.3%, respectively. No difference in prevalence of astigmatism was found across age groups. There was a statistically significant association between lower cylindrical diopters and higher spherical diopters (Spearman's correlation: -0.21, P < 0.001). Chinese children aged 3 to 6 years in the Shanghai area were mostly mildly hyperopic, with a low prevalence of myopia. Refractive astigmatism for children may be relatively stable throughout the preschool stage. Astigmatism was significantly associated with refractive error.

  6. A new low-cost, compact, auto-phoropter for refractive assessment in developing countries

    OpenAIRE

    Amirsolaimani, Babak; Peyman, Gholam; Schwiegerling, Jim; Bablumyan, Arkady; Peyghambarian, N.

    2017-01-01

    Using a phoropter to measure the refractive error is one of the most commonly used methods by ophthalmologists and optometrists. Here, we demonstrate design and fabrication of a portable automatic phoropter with no need for patient’s feedback. The system is based on three tunable-focus fluidic lenses and thin-film holographic optical elements to perform automatic refractive error measurement and provide a diagnostic prescription without supervision. Three separate lenses are deployed to corre...

  7. Human eye ocular component analysis for refractive state and refractive surgery

    Directory of Open Access Journals (Sweden)

    Chao-Kai Chang

    2017-07-01

    Full Text Available AIM: To analyze the clinical factors influencing the human vision corrections via the changing of ocular components of human eye in various applications; and to analyze refractive state via a new effective axial length. METHODS: An effective eye model was introduced by the ocular components of human eye including refractive indexes, surface radius (r1, r2, R1, R2 and thickness (t, T of the cornea and lens, the anterior chamber depth (S1 and the vitreous length (S2. Gaussian optics was used to calculate the change rate of refractive error per unit amount of ocular components of a human eye (the rate function M. A new criterion of myopia was presented via an effective axial length. RESULTS: For typical corneal and lens power of 42 and 21.9 diopters, the rate function Mj (j=1 to 6 were calculated for a 1% change of r1, r2, R1, R2, t, T (in diopters M1=+0.485, M2=-0.063, M3=+0.053, M4=+0.091, M5=+0.012, and M6=-0.021 diopters. For 1.0 mm increase of S1 and S2, the rate functions were M7=+1.35, and M8=-2.67 diopter/mm, respectively. These rate functions were used to analyze the clinical outcomes in various applications including laser in situ keratomileusis surgery, corneal cross linking procedure, femtosecond laser surgery and scleral ablation for accommodation. CONCLUSION: Using Gaussian optics, analytic formulas are presented for the change of refractive power due to various ocular parameter changes. These formulas provide useful clinical guidance in refractive surgery and other related procedures.

  8. US trends in refractive surgery: 2003 ISRS/AAO survey.

    Science.gov (United States)

    Duffey, Richard J; Leaming, David

    2005-01-01

    To determine the latest trends in refractive surgery in the United States. All U.S. members of the International Society of Refractive Surgery of the American Academy of Ophthalmology were mailed the 2003 refractive surgery survey dealing with volumes, types, preferences of refractive surgery performed, and use of new emerging technology. Questions regarding radial keratotomy (RK), astigmatic keratotomy (AK), limbal relaxing incisions (LRI), photorefractive keratectomy (PRK), laser in situ keratomileusis (LASIK), laser subepithelial keratomileusis (LASEK), intracorneal ring segments (ICRS), laser thermokeratoplasty (LTK), conductive keratoplasty (CK), phakic intraocular lenses (PIOL), clear lens extractions (CLE), and scleral expansion (SE) procedures were examined in the survey. Use of lasers, microkeratomes, pupillometry instruments, postoperative medications, wavefront analyzers, topographers, etc were examined. In 2003, LASIK continued to dominate for refractive errors between -8.00 to +3 diopters. Surgeons are waiting on the PIOL for high myopes and are performing CLE for high hyperopes. Photorefractive keratectomy, LASIK, LASEK, CLE, PIOL, and CK appeared to have bright futures; whereas, RK, ICR, LTK and SE were on the decline. Bilateral LASIK at the same surgical session is offered by 98% of surgeons. VISX lasers are used 2:1 over all other lasers in the United States. Zeiss-Humphrey still dominates topographers at 37%. The Bausch & Lomb Hansatome (48%) leads microkeratomes. Surgeons are charging, on average, 300-500 dollars more per eye for custom ablations and these ablations have already been accepted and integrated into refractive practices. Comanaging of refractive surgery patients is significantly down from previous years. Fourth-generation fluoroquinolones overtook the postoperative antibiotic prescriptions, with prednisolone and fluoromethalone dominating as anti-inflammatories. Trends and changes as refractive surgery grows in the mainstream of

  9. Projection-simulated ametropia. A model for teaching subjective refraction.

    Science.gov (United States)

    Henningsen, M A; Guyton, D L

    1985-06-01

    Teaching subjective refraction techniques ("refractometry") is enhanced by having the student experience the effect of each lens change "through the eyes of the patient." A projector, positioned behind the phoropter, projects a visual acuity chart through the phoropter onto the far wall. "Unknown" refractive errors are simulated by attaching trial lenses to the lens barrel of the projector, and the student progressively clears the projected image as he learns the standard steps of subjective refractometry. The focus sensitivity of each lens change can be varied, if desired, by stopping down the projection system. This simulation, which uses equipment readily available in most ophthalmology offices, has proven useful for both demonstration and practice.

  10. An alternative clinical routine for subjective refraction based on power vectors with trial frames.

    Science.gov (United States)

    María Revert, Antonia; Conversa, Maria Amparo; Albarrán Diego, César; Micó, Vicente

    2017-01-01

    Subjective refraction determines the final point of refractive error assessment in most clinical environments and its foundations have remained unchanged for decades. The purpose of this paper is to compare the results obtained when monocular subjective refraction is assessed in trial frames by a new clinical procedure based on a pure power vector interpretation with conventional clinical refraction procedures. An alternative clinical routine is described that uses power vector interpretation with implementation in trial frames. Refractive error is determined in terms of: (i) the spherical equivalent (M component), and (ii) a pair of Jackson Crossed Cylinder lenses oriented at 0°/90° (J 0 component) and 45°/135° (J 45 component) for determination of astigmatism. This vector subjective refraction result (VR) is compared separately for right and left eyes of 25 subjects (mean age, 35 ± 4 years) against conventional sphero-cylindrical subjective refraction (RX) using a phoropter. The VR procedure was applied with both conventional tumbling E optotypes (VR1) and modified optotypes with oblique orientation (VR2). Bland-Altman plots and intra-class correlation coefficient showed good agreement between VR, and RX (with coefficient values above 0.82) and anova showed no significant differences in any of the power vector components between RX and VR. VR1 and VR2 procedure results were similar (p ≥ 0.77). The proposed routine determines the three components of refractive error in power vector notation [M, J 0 , J 45 ], with a refraction time similar to the one used in conventional subjective procedures. The proposed routine could be helpful for inexperienced clinicians and for experienced clinicians in those cases where it is difficult to get a valid starting point for conventional RX (irregular corneas, media opacities, etc.) and for refractive situations/places with inadequate refractive facilities/equipment. © 2016 The Authors Ophthalmic & Physiological

  11. Comparison of the VISX WaveScan and OPD-Scan Ⅲ with the subjective refraction

    Directory of Open Access Journals (Sweden)

    Ran Zhu

    2014-10-01

    Full Text Available AIM: To compare the refractive errors measured by the VISX WaveScan, OPD-Scan Ⅲ and the subjective refraction.METHODS: Seventy-six patients(152 eyeswere recruited from January 2013 to December 2013. All patients were measured with subjective refraction by the phoropter(NIDEK, RT-5 100, objective refraction by the WaveScan(AMO Company, USA, OPD-Scan Ⅲ(Nidek Technologies, Japan. The sphere, cylinder, axis of the three methods were compared and analyzed.RESULTS: The sphere measured by WaveScan was lower than that by subjective refraction, the difference was 0.13±0.30D(t=3.753, Pt=3.664, PP>0.05. The value of the difference between WaveScan and subjective refraction was 5.87°±6.19° for the axis and the difference between OPD-Scan Ⅲ and subjective refraction was 3.82°±3.95°. There was statistic significance(t=2.817, P=0.006. CONCLUSION: For sphere and cylinder,WaveScan generated some deviation relative to subjective refraction. The Nidek OPD-Scan Ⅲ gives more accurate measures of objective refraction when compared with subjective refraction.

  12. Refractive profile in oculocutaneous albinism and its correlation with final visual outcome.

    Science.gov (United States)

    Yahalom, Claudia; Tzur, Veronica; Blumenfeld, Anat; Greifner, Gabriel; Eli, Dalia; Rosenmann, Ada; Glanzer, Sherry; Anteby, Irene

    2012-04-01

    To evaluate the prevalence of refractive errors in different subtypes of oculocutaneous albinism, and to see if there is any correlation between refractive errors and final visual outcome in this population. This is a retrospective study of 132 albino patients, ranging in age from 0.5 to 35 years. They were divided into four subtypes: OCA1A, OCA1B and OCA1C, and OCA2. Refractive errors were evaluated objectively by cycloplegic refraction and subjectively in cooperative patients. Best corrected visual acuity was assessed binocularly. Refractive errors were divided into three groups--hypermetropia, myopia and astigmatism--to avoid the use of spherical equivalent. Refractive errors were mainly astigmatism and hypermetropia. The OCA1A group showed high hypermetropia (≥ 5 dioptres) in 43.4% of patients, reaching significantly higher levels than in other subgroups (p=0.007). Mean visual acuity in logMAR was: OCA1A=0.81, OCA1B=0.64, OCA1C=0.61 and OCA2=0.48. Astigmatism averaged 2.1 dioptres (consistently with-the-rule), and it was homogeneously distributed between all subgroups (53%). The poorest visual acuity was found in those with OCA1A, which was associated with the highest rate of high hypermetropia (statistically significant different from other subgroups). Astigmatism was the most common visually significant refractive error across all subtypes of albinism. These results may help to clarify the prevalence of refractive errors in albino patients and aid the prediction of visual outcome in this heterogeneous population.

  13. An optomechanical model eye for ophthalmological refractive studies.

    Science.gov (United States)

    Arianpour, Ashkan; Tremblay, Eric J; Stamenov, Igor; Ford, Joseph E; Schanzlin, David J; Lo, Yuhwa

    2013-02-01

    To create an accurate, low-cost optomechanical model eye for investigation of refractive errors in clinical and basic research studies. An optomechanical fluid-filled eye model with dimensions consistent with the human eye was designed and fabricated. Optical simulations were performed on the optomechanical eye model, and the quantified resolution and refractive errors were compared with the widely used Navarro eye model using the ray-tracing software ZEMAX (Radiant Zemax, Redmond, WA). The resolution of the physical optomechanical eye model was then quantified with a complementary metal-oxide semiconductor imager using the image resolution software SFR Plus (Imatest, Boulder, CO). Refractive, manufacturing, and assembling errors were also assessed. A refractive intraocular lens (IOL) and a diffractive IOL were added to the optomechanical eye model for tests and analyses of a 1951 U.S. Air Force target chart. Resolution and aberrations of the optomechanical eye model and the Navarro eye model were qualitatively similar in ZEMAX simulations. Experimental testing found that the optomechanical eye model reproduced properties pertinent to human eyes, including resolution better than 20/20 visual acuity and a decrease in resolution as the field of view increased in size. The IOLs were also integrated into the optomechanical eye model to image objects at distances of 15, 10, and 3 feet, and they indicated a resolution of 22.8 cycles per degree at 15 feet. A life-sized optomechanical eye model with the flexibility to be patient-specific was designed and constructed. The model had the resolution of a healthy human eye and recreated normal refractive errors. This model may be useful in the evaluation of IOLs for cataract surgery. Copyright 2013, SLACK Incorporated.

  14. Parsimonious Refraction Interferometry and Tomography

    KAUST Repository

    Hanafy, Sherif

    2017-02-04

    We present parsimonious refraction interferometry and tomography where a densely populated refraction data set can be obtained from two reciprocal and several infill shot gathers. The assumptions are that the refraction arrivals are head waves, and a pair of reciprocal shot gathers and several infill shot gathers are recorded over the line of interest. Refraction traveltimes from these shot gathers are picked and spawned into O(N2) virtual refraction traveltimes generated by N virtual sources, where N is the number of geophones in the 2D survey. The virtual traveltimes can be inverted to give the velocity tomogram. This enormous increase in the number of traveltime picks and associated rays, compared to the many fewer traveltimes from the reciprocal and infill shot gathers, allows for increased model resolution and a better condition number with the system of normal equations. A significant benefit is that the parsimonious survey and the associated traveltime picking is far less time consuming than that for a standard refraction survey with a dense distribution of sources.

  15. Comparison of the VISX wavescan and OPD-scan III with the subjective refraction.

    Science.gov (United States)

    Zhu, R; Long, K-L; Wu, X-M; Li, Q-D

    2016-07-01

    To compare the refractive errors measured by the VISX WaveScan, OPD-Scan III and the subjective refraction. The optometry accuracy of computer operated aberrometer used before refractive surgery has been debatable. Hence, a clear study on the role of such automated equipment in optometry is the need of the hour as compared to subjective refraction. Seventy-six patients (152 eyes) were recruited from January 2013 to December 2013. All patients were measured with subjective refraction by the phoropter (NIDEK, RT-5100), objective refraction by the WaveScan (AMO Company, USA), OPD-Scan III (Nidek Technologies, Japan). The sphere, cylinder, axis of the three methods were compared and analyzed. The diopter of sphere power measured by WaveScan was lower than that of the subjective refraction and the difference was 0.13 ± 0. 30D (t = 3. 753, p 0. 05). The value of the difference between WaveScan and subjective refraction was 5.87°±6.19°on average, while the difference between OPD-Scan III and subjective refraction was 3.82°±3.95°on average. The differences between the two were statistically significant (t =2. 817, p =0. 006). The results of sphere and cylinder measured by WaveScan and subjective refraction were different. As the latest integrated equipment, the Nidek OPD-Scan III gives a more accurate measurement of objective refraction when compared with subjective refraction. The latest Nidek OPD-Scan III may prove to be an useful tool for preoperative optometry deviation based on objective refraction.

  16. Pattern of Refractive Errors Among Ophthalmic Outpatients of ...

    African Journals Online (AJOL)

    of consecutive patients attending a tertiary eye facility who were diagnosed with RE and/or presbyopia from January 2010 to. December ... of VISION. 2020, the data presented in this study will help in planning result-oriented intervention programs in the state. ... In the period under review, a total of 676 consecutive patients ...

  17. Refractive errors in type 2 diabetic patients | Mwale | East African ...

    African Journals Online (AJOL)

    : EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT · http://dx.doi.org/10.4314/eamj.v84i6.9534 · AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians ...

  18. Prevalence of myopia amongst patients with refractive error in

    African Journals Online (AJOL)

    User

    prevalence estimate of males is higher than females which are in contrast with a number of studies that report of a higher prevalence in girls than in boys. (Zadnik et al., 2003; Ip et al., 2008; Rudnicka et al., 2008). ... engineering students and microscopist (Zadnik and Mutti, 1987; McBrien and Adams, 1997;. Kinje et al., 2000 ...

  19. Poor vision, refractive errors and barriers to treatment among ...

    African Journals Online (AJOL)

    Structured questionnaire were also administered to the participants to collect demographic data, history of driving and RTAs and utilization of eye care services as well as identification of the colours of the traffic light. Results: A total of 206 male drivers were interviewed and examined. Over 12% of the commercial drivers do ...

  20. Prevalence of Presbyopia, Refractive Errors and Usage of ...

    African Journals Online (AJOL)

    Their age ranged from 20-90 years (mean: 44.2 years, SD 9.2). 78 (35.3%) persons complained of difficulty in reading small prints while 17(7.7%) persons complained of poor distant vision. Ten (4.5%) drivers had a visual acuity of <6/12 and thus did not qualify to possess a driving licence. Presbyopia was the most common ...

  1. Prevalence of Myopia amongst patients with refractive error in the ...

    African Journals Online (AJOL)

    Journal of Science and Technology (Ghana). Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 33, No 2 (2013) >. Log in or Register to get access to full text downloads.

  2. Bayesian inversion of refraction seismic traveltime data

    Science.gov (United States)

    Ryberg, T.; Haberland, Ch

    2018-03-01

    We apply a Bayesian Markov chain Monte Carlo (McMC) formalism to the inversion of refraction seismic, traveltime data sets to derive 2-D velocity models below linear arrays (i.e. profiles) of sources and seismic receivers. Typical refraction data sets, especially when using the far-offset observations, are known as having experimental geometries which are very poor, highly ill-posed and far from being ideal. As a consequence, the structural resolution quickly degrades with depth. Conventional inversion techniques, based on regularization, potentially suffer from the choice of appropriate inversion parameters (i.e. number and distribution of cells, starting velocity models, damping and smoothing constraints, data noise level, etc.) and only local model space exploration. McMC techniques are used for exhaustive sampling of the model space without the need of prior knowledge (or assumptions) of inversion parameters, resulting in a large number of models fitting the observations. Statistical analysis of these models allows to derive an average (reference) solution and its standard deviation, thus providing uncertainty estimates of the inversion result. The highly non-linear character of the inversion problem, mainly caused by the experiment geometry, does not allow to derive a reference solution and error map by a simply averaging procedure. We present a modified averaging technique, which excludes parts of the prior distribution in the posterior values due to poor ray coverage, thus providing reliable estimates of inversion model properties even in those parts of the models. The model is discretized by a set of Voronoi polygons (with constant slowness cells) or a triangulated mesh (with interpolation within the triangles). Forward traveltime calculations are performed by a fast, finite-difference-based eikonal solver. The method is applied to a data set from a refraction seismic survey from Northern Namibia and compared to conventional tomography. An inversion test

  3. US trends in refractive surgery: 2002 ISRS survey.

    Science.gov (United States)

    Duffey, Richard J; Leaming, David

    2003-01-01

    To determine the latest trends in refractive surgery in the United States. The full U.S. membership of the International Society of Refractive Surgery (ISRS) (approximately 900 members) was mailed the 2002 refractive surgery survey dealing with volumes, types, preferences of refractive surgery performed, and use of emerging technology. Questions regarding RK, AK, PRK, LASIK, LASEK, intracorneal ring segments (ICRS), laser thermal keratoplasty (LTK), conductive keratoplasty (CK), phakic intraocular lenses (PIOL), and clear lens extractions (CLE) were examined in the survey. Procedure preference for low, moderate, and high myopia, and hyperopia, were compared with the results from the surveys of the previous 5 years. Preference for unilateral versus bilateral same-day surgery, laser type, and microkeratome choice were also compared with the survey data from previous years. Incidence and frequency of co-management of refractive surgery patients were compared with 1999-2001 data. New questions regarding pupil measurement/documentation, wavefront aberrometry, and custom ablations were incorporated into the 2002 survey. As refractive surgery grows in the mainstream of ophthalmology, trends and changes in the United States continue to be elucidated by this professional organization survey. LASIK continues to dominate for refractive errors between -10.00 to +3.00 D. LASIK, LASEK, CLE, PIOL, and CK appear to have bright futures, whereas, RK, ICR, and LTK are on the decline. VISX continues to be utilized 2:1 over all other lasers combined, and instrumentation pupillometry is preferred 2:1 over pupil gauge cards. Currently, wavefront aberrometry and custom ablations are minimally employed but appear poised to be the wave of the future.

  4. Analysis of refractive state in 708 children with ametropic amblyopia

    Directory of Open Access Journals (Sweden)

    Ju-Fen Huang

    2016-01-01

    Full Text Available AIM: To analyze the refractive state and explore the epidemiologic feature of children with ametropic amblyopia.METHODS: This study retrospectively analyzed 708 children(1 416 eyeswith amblyopia from January 2012 to December 2013 in Special Department of Strabismus and Amblyopic and Department of Pediatric Ophthalmology in our hospital, who were diagnosed as ametropic amblyopia and accepted centrally comprehensive training. The refractive state were given epidemiologic analyze.RESULTS: In the 708 cases(1 416 eyes, there were 190 eyes with hyperopia(13.42%,612 eyes with hyperopia astigmatism(43.22%,18 eyes with myopia(1.27%,134 eyes with myopia astigmatism(9.46%,462 eyes with mixed astigmatism(32.63%. The distributions of refractive state in children at different age were different, and the difference was statistically significant(PCONCLUSION: Hyperopia ametropia and mixed astigmatism are the main types of refractive errors in amblyopia children. The level of amblyopia is related to refractive state and astigmatism axial.

  5. Changes in refractive characteristics in Japanese children with Down syndrome.

    Science.gov (United States)

    Horio, Junna; Kaneko, Hiroki; Takayama, Kei; Tuzuki, Kinichi; Kakihara, Hiroko; Iwami, Miou; Kawase, Yoshikatsu; Tsunekawa, Taichi; Yamaguchi, Naoko; Nonobe, Norie; Terasaki, Hiroko

    2018-03-01

    To investigate the refractive characteristics of Japanese children with Down syndrome. Retrospective study. The clinical records of refractive errors and ocular manifestations in children with Down syndrome who visited the Aichi Children's Health and Medical Center between November 2001 and January 2016 were retrospectively reviewed. The children were divided into the 3 following groups depending on their age: group 1 (≤ 6 years), group 2 (7-12 years), and group 3 (13-19 years). The collection of refractive error data was performed only for the right eyes and only once for each child, when the children were last examined with their pupils dilated. The study included 416 children (224 boys, 192 girls; average age, 6.1 ± 4.1 years). Group 3 had significantly stronger myopia than did groups 1 and 2. The mean cylindrical power in all the children was - 2.1 ± 1.2 diopters (D), and cylindrical power ≤ - 1.0 D (stronger than - 1.0 D) was seen in 366 eyes (88%). No significant difference in cylindrical power was found among the 3 groups. The spherical equivalent refraction showed an age-dependent myopic shift. Given that the amount of astigmatism did not show age-dependent differences, the age-dependent myopic shift could be due mainly to the change in spherical power.

  6. Residual deposits (residual soil)

    International Nuclear Information System (INIS)

    Khasanov, A.Kh.

    1988-01-01

    Residual soil deposits is accumulation of new formate ore minerals on the earth surface, arise as a result of chemical decomposition of rocks. As is well known, at the hyper genes zone under the influence of different factors (water, carbonic acid, organic acids, oxygen, microorganism activity) passes chemical weathering of rocks. Residual soil deposits forming depends from complex of geologic and climatic factors and also from composition and physical and chemical properties of initial rocks

  7. Refractive states of eyes and associations between ametropia and age, breed, and axial globe length in domestic cats.

    Science.gov (United States)

    Konrade, Kricket A; Hoffman, Allison R; Ramey, Kelli L; Goldenberg, Ruby B; Lehenbauer, Terry W

    2012-02-01

    To determine the refractive states of eyes in domestic cats and to evaluate correlations between refractive error and age, breed, and axial globe measurements. 98 healthy ophthalmologically normal domestic cats. The refractive state of 196 eyes (2 eyes/cat) was determined by use of streak retinoscopy. Cats were considered ametropic when the mean refractive state was ≥ ± 0.5 diopter (D). Amplitude-mode ultrasonography was used to determine axial globe length, anterior chamber length, and vitreous chamber depth. Mean ± SD refractive state of all eyes was -0.78 ± 1.37 D. Mean refractive error of cats changed significantly as a function of age. Mean refractive state of kittens (≤ 4 months old) was -2.45 ± 1.57 D, and mean refractive state of adult cats (> 1 year old) was -0.39 ± 0.85 D. Mean axial globe length, anterior chamber length, and vitreous chamber depth were 19.75 ± 1.59 mm, 4.66 ± 0.86 mm, and 7.92 ± 0.86 mm, respectively. Correlations were detected between age and breed and between age and refractive states of feline eyes. Mean refractive error changed significantly as a function of age, and kittens had greater negative refractive error than did adult cats. Domestic shorthair cats were significantly more likely to be myopic than were domestic mediumhair or domestic longhair cats. Domestic cats should be included in the animals in which myopia can be detected at a young age, with a likelihood of progression to emmetropia as cats mature.

  8. [Diurnal fluctuations in human refraction].

    Science.gov (United States)

    Krause, K; Taege, A

    1988-01-01

    The spectacle values of young healthy students were determined morning and afternoon by means of phoropter and autorefractometer. In addition, keratometry was performed. When the morning and afternoon refraction values were compared the latter were found to be about 0.25 diopters lower. This effect cannot be attributed exclusively to changes in the radius of the cornea.

  9. SEISMIC REFRACTION INVESTIGATION OF GROUNDWATER ...

    African Journals Online (AJOL)

    There was a good correlation between seismic interpretation and borehole lithologic section within the study area. With a considerable saturated thickness, areas of good potential aquifers for groundwater development abound in the study area. KeyWords: Seismic refraction, groundwater development, basement, Oban ...

  10. Refraction and Ocular Biometry of Preschool Children in Shanghai, China

    Directory of Open Access Journals (Sweden)

    Luoli Zhang

    2018-01-01

    Full Text Available Purpose. To investigate the refraction and ocular biometry characteristics and to examine the prevalence of refractive errors in preschool children aged 3 to 6 years in Shanghai, China. Methods. A school-based cross-sectional study was conducted in Jiading and Xuhui District, Shanghai, in 2013. We randomly selected 7 kindergartens in Jiading District and 10 kindergartens in Xuhui District, with a probability proportionate to size. The children underwent comprehensive eye examinations, including cycloplegic refraction and biometric measurements. Myopia, hyperopia, astigmatism were defined as spherical equivalent (SE ≤ −0.50 D, SE ≥ +2.00 D, and cylindrical diopters ≤ −1.00 D. Results. The mean SE for 3- to 6-year-old children was +1.20 D (standard deviation [SD] 1.05, and the mean axial length (AL was 22.29 mm (SD 0.73. The overall prevalence of myopia and astigmatism was 3.7% and 18.3%, respectively. No difference in prevalence of astigmatism was found across age groups. There was a statistically significant association between lower cylindrical diopters and higher spherical diopters (Spearman’s correlation: −0.21, P<0.001. Conclusion. Chinese children aged 3 to 6 years in the Shanghai area were mostly mildly hyperopic, with a low prevalence of myopia. Refractive astigmatism for children may be relatively stable throughout the preschool stage. Astigmatism was significantly associated with refractive error.

  11. Effect of Cycloplegia on the Refractive Status of Children: The Shandong Children Eye Study

    Science.gov (United States)

    Hu, Yuan Yuan; Wu, Jian Feng; Lu, Tai Liang; Wu, Hui; Sun, Wei; Wang, Xing Rong

    2015-01-01

    Purpose To determine the effect of 1% cyclopentolate on the refractive status of children aged 4 to 18 years. Methods Using a random cluster sampling in a cross-sectional school-based study design, children with an age of 4–18 years were selected from kindergardens, primary schools, junior and senior high schools in a rural county and a city. Auto-refractometry was performed before and after inducing cycloplegia which was achieved by 1% cyclopentolate eye drops. Results Out of 6364 eligible children, data of 5999 (94.3%) children were included in the statistical analysis. Mean age was 10.0±3.3 years (range: 4–18 years). Mean difference between cycloplegic and non-cycloplegic refractive error (DIFF) was 0.78±0.79D (median: 0.50D; range: -1.00D to +10.75D). In univariate analysis, DIFF decreased significantly with older age (Prefractive error (Prefractive error (Prefractive error (PPrevalence of emmetropia decreased from 37.5% before cycloplegia to 19.8% after cycloplegia while the remaining eyes became hyperopic under cycloplegia. Conclusions The error committed by using non-cycloplegic versus cycloplegic refractometry in children with mid to dark-brown iris color decreased with older age, and in parallel manner, with more myopic cycloplegic refractive error. Non-cycloplegic refractometric measures lead to a misclassification of refractive error in a significant proportion of children. PMID:25658329

  12. Effect of cycloplegia on the refractive status of children: the Shandong children eye study.

    Science.gov (United States)

    Hu, Yuan Yuan; Wu, Jian Feng; Lu, Tai Liang; Wu, Hui; Sun, Wei; Wang, Xing Rong; Bi, Hong Sheng; Jonas, Jost B

    2015-01-01

    To determine the effect of 1% cyclopentolate on the refractive status of children aged 4 to 18 years. Using a random cluster sampling in a cross-sectional school-based study design, children with an age of 4-18 years were selected from kindergardens, primary schools, junior and senior high schools in a rural county and a city. Auto-refractometry was performed before and after inducing cycloplegia which was achieved by 1% cyclopentolate eye drops. Out of 6364 eligible children, data of 5999 (94.3%) children were included in the statistical analysis. Mean age was 10.0±3.3 years (range: 4-18 years). Mean difference between cycloplegic and non-cycloplegic refractive error (DIFF) was 0.78±0.79D (median: 0.50D; range: -1.00D to +10.75D). In univariate analysis, DIFF decreased significantly with older age (Prefractive error (Prefractive error (Prefractive error (PPrevalence of emmetropia decreased from 37.5% before cycloplegia to 19.8% after cycloplegia while the remaining eyes became hyperopic under cycloplegia. The error committed by using non-cycloplegic versus cycloplegic refractometry in children with mid to dark-brown iris color decreased with older age, and in parallel manner, with more myopic cycloplegic refractive error. Non-cycloplegic refractometric measures lead to a misclassification of refractive error in a significant proportion of children.

  13. A Large-Scale Computational Analysis of Corneal Structural Response and Ectasia Risk in Myopic Laser Refractive Surgery.

    Science.gov (United States)

    Dupps, William Joseph; Seven, Ibrahim

    2016-08-01

    To investigate biomechanical strain as a structural susceptibility metric for corneal ectasia in a large-scale computational trial. A finite element modeling study was performed using retrospective Scheimpflug tomography data from 40 eyes of 40 patients. LASIK and PRK were simulated with varied myopic ablation profiles and flap thickness parameters across eyes from LASIK candidates, patients disqualified for LASIK, subjects with atypical topography, and keratoconus subjects in 280 simulations. Finite element analysis output was then interrogated to extract several risk and outcome variables. We tested the hypothesis that strain is greater in known at-risk eyes than in normal eyes, evaluated the ability of a candidate strain variable to differentiate eyes that were empirically disqualified as LASIK candidates, and compared the performance of common risk variables as predictors of this novel susceptibility marker across multiple virtual subjects and surgeries. A candidate susceptibility metric that expressed mean strains across the anterior residual stromal bed was significantly higher in eyes with confirmed ectatic predisposition in preoperative and all postoperative cases (P≤.003). The strain metric was effective at differentiating normal and at-risk eyes (area under receiver operating characteristic curve ≥ 0.83, P≤.002), was highly correlated to thickness-based risk metrics (as high as R(2) = 95%, Pectasia risk and provides a novel biomechanical construct for expressing structural risk in refractive surgery. Mechanical strain is an effective marker of known ectasia risk and correlates to predicted refractive error after myopic photoablative surgery.

  14. Refracting surface plasmon polaritons with nanoparticle arrays

    DEFF Research Database (Denmark)

    Radko, I.P.; Evlyukhin, A.B.; Boltasseva, Alexandra

    2008-01-01

    Refraction of surface plasmon polaritons (SPPs) by various structures formed by a 100-nm-period square lattice of gold nanoparticles on top of a gold film is studied by leakage radiation microscopy. SPP refraction by a triangular-shaped nanoparticle array indicates that the SPP effective refractive...... to design nanoparticle arrays for specific applications requiring in-plane SPP manipulation....

  15. Super-Virtual Refraction Interferometric Redatuming: Enhancing the Refracted Energy

    KAUST Repository

    Aldawood, Ali

    2012-02-26

    onshore seismic data processing. Refraction tomography is becoming a common way to estimate an accurate near surface velocity model. One of the problems with refraction tomography is the low signal to noise ration in far offset data. To improve, we propose using super-virtual refraction interferometry to enhance the weak energy at far offsets. We use Interferometric Green\\'s functions to redatum sources by cross-correlating two traces recorded at receiver stations, A and B, from a source at location W. The result is a redatumed trace with a virtual source at A and a receiver at B, which can also be obtained by correlating two traces recorded at A and B from different shots. Stacking them would enhance the signal-to-noise ratio of this "virtual" trace. We next augment redatuming with convolution and stacking. The trace recorded at B from a virtual source at A is convolved with the original trace recorded at A from a source at W. The result is a "super-virtual" trace at B in the far-offset from a source at W. Stacking N traces gives a vN-improvement. We applied our method to noisy synthetic and field data recorded over a complex near-surface and we could pick more traces at far offsets. It was possible to accommodate more picks resulting in a better subsurface coverage

  16. Modification of Low Refractive Index Polycarbonate for High Refractive Index Applications

    Directory of Open Access Journals (Sweden)

    Gunjan Suri

    2009-01-01

    Full Text Available Polycarbonates and polythiourethanes are the most popular materials in use today, for optical applications. Polycarbonates are of two types which fall in the category of low refractive index and medium refractive index. The present paper describes the conversion of low refractive index polycarbonates into high refractive index material by the use of a high refractive index monomer, polythiol, as an additive. Novel polycarbonates, where the properties of refractive index and Abbe number can be tailor made, have been obtained. Thermal studies and refractive index determination indicate the formation of a new polymer with improved properties and suitable for optical applications.

  17. What is refractive optical bistability

    International Nuclear Information System (INIS)

    Dzhehov, Tomislav

    1993-01-01

    The basic elements of the theory of refractive optical bistability, assuming mediums with linear absorption are given. Special attention is paid to bistable etalons of semiconductor materials an oxide glasses, since some of them are considered as promising components for optical bistability applications. The design optimization of such devices for minimum switching intensity is analyzed. Computer simulation of the transfer characteristic recording for two InSb etalons is presented. (author)

  18. Medication Errors

    Science.gov (United States)

    ... for You Agency for Healthcare Research and Quality: Medical Errors and Patient Safety Centers for Disease Control and ... Quality Chasm Series National Coordinating Council for Medication Error Reporting and Prevention ... Devices Radiation-Emitting Products Vaccines, Blood & Biologics Animal & ...

  19. Corneal wavefront-guided LASIK retreatments for correction of highly aberrated corneas following refractive surgery.

    Science.gov (United States)

    Alió, Jorge; Galal, Ahmed; Montalbán, Raúl; Piñero, David

    2007-10-01

    To investigate the safety and efficacy of customized corneal wavefront-guided retreatment in symptomatic patients with highly aberrated corneas following LASIK. This prospective study included 75 eyes of 59 patients with significant visual symptoms who underwent LASIK for the correction of residual refractive error. Ablation profiles were calculated using CSO corneal topography and ESIRIS/Schwind laser platform. Eyes were divided into two groups: those with significant night vision symptoms (37 eyes; night symptoms group) and those with decentration, irregular ablation profile, and flap complications (38 eyes; corneal complications group). Corneal topography and aberrations, visual acuity, point spread function (PSF), refractive outcome, and subjective symptoms were evaluated preoperatively, and 1, 3, and 6 months postoperatively. Mean uncorrected visual acuity was 20/32 preoperatively and 20/25 at 6 months postoperatively in the night symptoms group and 20/40 preoperatively and 20/30 at 6 months postoperatively in the corneal complications group. Mean best spectacle-corrected visual acuity was 20/25 both preoperatively and 6 months postoperatively in both groups (t test, P = .219 and P = .149 for the night symptoms and corneal complications groups, respectively). Safety index was 1.1 in both groups, and efficacy index was 0.93 and 0.92, respectively. Statistically significant improvement of total corneal higher order aberrations, tilt, and improvement of spherical aberrations and coma were observed, with corresponding improvement of PSF. Corneal wavefront-guided LASIK retreatment with CSO topography, ORK-W software, and ESIRIS/Schwind laser platform is safe and effective for treating symptomatic patients affected by corneal higher order aberrations or corneal irregularities following LASIK surgery.

  20. About the correctness of laser refractive surgery in children

    Directory of Open Access Journals (Sweden)

    V. V. Kurenkov

    2016-01-01

    Full Text Available Disturbances of refraction are one of the most urgent problems of pediatric ophthalmology. Late and incomplete correction of refractive errors leads to the development of amblyopia, disturbances of binocular vision, the appearance of strabismus. Such complications reduce the quality of life, drastically limit the choice of professional child. Pediatric Ophthalmology always face a choice: many drugs and technologies are not approved for use in pediatric patients, practitioners are forced to use their «off-label», but such situations require great care and strict medical indications. For example, refractive surgery has worked well in adults, but its use remains controversial in children for security reasons and unpredictable effects. Several authors have described the use of laser refractive surgery in children under the age of 18 years, but there are no results of a multicenter, controlled study evaluating the safety, efficacy, and especially long-term results. In all the studies, the calculation was performed on adult nomograms ablation, while not proved how they are accurate for children. Long-term results and data on the endothelial cell density, corneal curvature changes in catamnesis are presented no longer than two years. Despite the fact that currently there is insufficient information about the results of remote application keratorefractive laser surgery in children, and there are no indication system and contraindications, modern achievements in medicine should be used in pediatric patients, and our successful track record proves it clearly. Undoubtedly, the positive experience of the laser surgery use in a child with clouding of the cornea in the outcome of herpetic keratitis, which provided a positive result: high visual acuity, binocular vision and lack of infection relapses for 2 years, requires study, evidence multicenter studies, and possibly expansion of indications for refractive laser surgery.

  1. Refractions

    DEFF Research Database (Denmark)

    Hougaard, Anna Katrine; Søberg, Martin; Lorentsen, Elise

    2016-01-01

    The book focuses on new directions in architectural research, how architects develop new knowledge through their artistic design practice, working in a field between Art and Science. What new digital potentials are there in architectural media like models and drawings and how to put words on arti...... on artistic research? The book offers theoretical articles, picture galleries of artistic projects, and interviews with senior-researchers at the Danish Academy of Architecture in Copenhagen and their built architectural projects.......The book focuses on new directions in architectural research, how architects develop new knowledge through their artistic design practice, working in a field between Art and Science. What new digital potentials are there in architectural media like models and drawings and how to put words...

  2. Refractive Surgery: Malpractice Litigation Outcomes.

    Science.gov (United States)

    Custer, Benjamin L; Ballard, Steven R; Carroll, Robert B; Barnes, Scott D; Justin, Grant A

    2017-10-01

    To review data on malpractice claims related to refractive surgery to identify common allegations and injuries and financial outcomes. The WestlawNext database was reviewed for all malpractice lawsuits/settlements related to refractive eye surgery. Data evaluated included patient demographics, type of operation performed, plaintiff allegation, nature of injury, and litigation outcomes. A total of 167 cases met the inclusion criteria, of which 108 cases (64.7%) were found to be favorable and 59 cases (35.3%) unfavorable to the defendant. A total of 141 cases were tried by a jury with 108 cases (76.4%) favorable and 33 cases (23.6%) unfavorable to the defendant. Laser in situ keratomileusis was performed in 127 cases (76%). The most common allegations were negligence in treatment or surgery in 127 cases (76%) and lack of informed consent in 83 cases (49.7%). For all cases, the need for future surgery (P = 0.0001) and surgery resulting in keratoconus (P = 0.05) were more likely to favor the plaintiff. In jury verdict decisions, cases in which failure to diagnose a preoperative condition was alleged favored the defendant (P = 0.03), whereas machine malfunction (P = 0.05) favored the plaintiff. After adjustment for inflation, the overall mean award was $1,287,872. Jury verdicts and settlements led to mean awards of $1,604,801 and $826,883, respectively. Malpractice litigation in refractive surgery tends to favor the defendant. However, large awards and settlements were given in cases that were favorable to the plaintiff. The need for future surgery and surgery leading to keratoconus increased the chance of an unfavorable outcome.

  3. Theory of supervirtual refraction interferometry

    KAUST Repository

    Bharadwaj, Pawan

    2012-01-01

    Inverting for the subsurface velocity distribution by refraction traveltime tomography is a well-accepted imaging method by both the exploration and earthquake seismology communities. A significant drawback, however, is that the recorded traces become noisier with increasing offset from the source position, and so accurate picking of traveltimes in far-offset traces is often prevented. To enhance the signal-to-noise ratio (SNR) of the far-offset traces, we present the theory of supervirtual refraction interferometry where the SNR of far-offset head-wave arrivals can be theoretically increased by a factor proportional to; here, N is the number of receiver or source positions associated with the recording and generation of the head-wave arrival. There are two steps to this methodology: correlation and summation of the data to generate traces with virtual head-wave arrivals, followed by the convolution of the data with the virtual traces to create traces with supervirtual head-wave arrivals. This method is valid for any medium that generates head-wave arrivals recorded by the geophones. Results with both synthetic traces and field data demonstrate the feasibility of this method. There are at least four significant benefits of supervirtual interferometry: (1) an enhanced SNR of far-offset traces so the first-arrival traveltimes of the noisy far-offset traces can be more reliably picked to extend the useful aperture of the data, (2) the SNR of head waves in a trace that arrive later than the first arrival can be enhanced for accurate traveltime picking and subsequent inversion by later-arrival traveltime tomography, (3) common receiver-pair gathers can be analysed to detect the presence of diving waves in the first arrivals, which can be used to assess the nature of the refracting boundary, and (4) the source statics term is eliminated in the correlation operations so that the timing of the virtual traces is independent of the source excitation time. This suggests the

  4. Operator errors

    International Nuclear Information System (INIS)

    Knuefer; Lindauer

    1980-01-01

    Besides that at spectacular events a combination of component failure and human error is often found. Especially the Rasmussen-Report and the German Risk Assessment Study show for pressurised water reactors that human error must not be underestimated. Although operator errors as a form of human error can never be eliminated entirely, they can be minimized and their effects kept within acceptable limits if a thorough training of personnel is combined with an adequate design of the plant against accidents. Contrary to the investigation of engineering errors, the investigation of human errors has so far been carried out with relatively small budgets. Intensified investigations in this field appear to be a worthwhile effort. (orig.)

  5. [Refractive lenticule extraction - The ReLEx/SMILE technique : Video article].

    Science.gov (United States)

    Blum, M; Sekundo, W

    2017-09-01

    Refractive lenticule extraction (ReLEx/SMILE) is a refractive surgical method developed by the authors in stages primarily for correction of myopia and myopic astigmatism, in which a femtosecond laser is exclusively used. In the (ReLEx/SMILE) method a refractive lenticule is generated by the femtosecond laser, which is subsequently extracted through a small incision. Opening of the corneal surface with a flap and use of an excimer laser is no longer necessary. In 2013 the method was newly assessed and classified by the Joint Commisssion for Refractive Surgery (KRC) of the Professional Association of Ophthalmologists (BVA) and the German Ophthalmological Society (DOG). This article presents the individual stages of the technique in a video and possible errors and their avoidance are explained.

  6. Analysis of visual acuity before and after refraction in people over 50 in ophthalmic outpatients

    Directory of Open Access Journals (Sweden)

    Dan Shui

    2013-08-01

    Full Text Available AIM: To investigate the visual acuity of people over 50 years in ophthalmic clinic and visual impairment before and after refractive correction.METHODS: Totally 149 cases(298 eyesof refractive error were examined and corrected using autorefractor and retinal optometry. The information of age, sex, economy, income and living standard were collected by questionnaire.RESULTS: Out of 149 cases(298 eyes, 281 eyes(98.6%had refractive error. 119 eyes(42.3%had myopia, 94 eyes(33.5%had hyperopia and 68 eyes(24.2%had mixed astigmatism. The mean visual acuity was 0.42±0.21 and 0.63±0.32 respectively before and after correction. Corrected visual impairment was in 186 eyes(65.3%. Old age, low education, low income and rural area were risk factors for visual impairment. CONCLUSION: Uncorrected refractive error is an important cause of visual impairment in elderly people. It can be promoted by refractive correction, which may benefit for their living quality.

  7. [Complications after refractive surgery abroad].

    Science.gov (United States)

    Terzi, E; Kern, T; Kohnen, T

    2008-05-01

    In this article a retrospective analysis of patients presenting at a German university following refractive surgery abroad is presented. A total of 20 cases of patients who had undergone treatment between 1998 and 2006 in China (1 case), Greece (1 case), Iran (1 case), Russia (2 cases), Switzerland (1 case), Slovakia (1 case), Spain (2 cases), South Africa (3 cases), Turkey (6 cases) and the USA (2 cases) were analyzed retrospectively. The following complications were observed: epithelial ingrowth into the interface with or without melting of the flap (6 cases), corneal ectasia (2 cases), dislocation of a phakic posterior chamber intraocular lens and prolapse into the anterior chamber with endothelial cell loss (1 case), secondary increase of intraocular pressure following implantation of a phakic intraocular lens (1 case), flap-related complications following laser-in-situ keratomileusis (LASIK) (2 cases), keratitis (1 case), dislocation of the complete flap (1 case), diffuse lamellar keratitis (DLK) grade IV (1 case), hyperopia as a consequence of radial keratotomy (1 case), and under correction/over correction and poor optical quality following laser epithelial keratomileusis (LASEK) and LASIK for high myopia (5 cases) with possible early corneal ectasia. There are four important problems arising from refractive surgery abroad, often referred to as "LASIK tourism": wrong indications, insufficient management of complications, lack of postoperative care and the health economic aspect.

  8. Refractive index of plant cell walls

    Science.gov (United States)

    Gausman, H. W.; Allen, W. A.; Escobar, D. E.

    1974-01-01

    Air was replaced with media of higher refractive indices by vacuum infiltration in leaves of cucumber, blackeye pea, tomato, and string bean plants, and reflectance of noninfiltrated and infiltrated leaves was spectrophotometrically measured. Infiltrated leaves reflected less light than noninfiltrated leaves over the 500-2500-nm wavelength interval because cell wall-air interfaces were partly eliminated. Minimal reflectance should occur when the average refractive index of plant cell walls was matched by the infiltrating fluid. Although refractive indices that resulted in minimal reflectance differed among the four plant genera, an average value of 1.425 approximates the refractive index of plant cell walls for the four plant genera.

  9. Influence of corneal asphericity on the refractive outcome of intraocular lens implantation in cataract surgery.

    Science.gov (United States)

    Savini, Giacomo; Hoffer, Kenneth J; Barboni, Piero

    2015-04-01

    To evaluate the possible influence of anterior corneal surface asphericity on the refractive outcomes in eyes having intraocular lens (IOL) implantation after cataract surgery. Fondazione G.B. Bietti IRCCS, Rome, Italy. Retrospective comparative case series. Intraocular lens power was calculated using the Haigis, Hoffer Q, Holladay 1, and SRK/T formulas. Asphericity (Q-value) was measured at 8.0 mm with a Placido-disk corneal topographer (Keratron), a rotating Scheimpflug camera (Pentacam), and a rotating Scheimpflug camera combined with Placido-disk corneal topography (Sirius). The relationship between the error in refraction prediction (ie, difference between expected refraction and refraction measured 1 month after surgery) and the Q-value was assessed by linear regression. The same IOL model (Acrysof SA60AT) was implanted in 115 eyes of 115 consecutive patients. Regression analysis showed a statistically significant relationship between the error in refraction prediction and the Q-value with all formulas and all devices. In all cases, a more negative Q-value (prolate cornea) was associated with a myopic outcome, whereas a more positive Q-value (oblate cornea) was associated with a hyperopic outcome. The highest coefficient of determination was detected between the Hoffer Q formula and the Placido-disk corneal topographer (R(2) = 0.2630), for which the error in refraction prediction (y) was related to the Q-value (x) according to the formula y = -0.2641 + 1.4589 × x. Corneal asphericity influences the refractive outcomes of IOL implantation and should be taken into consideration when using third-generation IOL power formulas. Dr. Hoffer receives book royalties from Slack, Inc., Thorofare, New Jersey, and formula royalties from all manufacturers using the Hoffer Q formula. No other author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  10. Refractive predictability of a 3-piece intraocular lens platform versus its 1-piece counterpart.

    Science.gov (United States)

    Mednick, Zale D; Varma, Devesh K; Campos-Möller, Xavier; Ahmed, Iqbal Ike K

    2017-04-01

    To compare the refractive outcomes of a 3-piece acrylic intraocular lens (IOL) with its 1-piece counterpart after phacoemulsification with in-the-bag implantation. Retrospective chart review. One-hundred twenty-six eyes of 95 patients were analyzed in the study, including 60 eyes of 43 patients receiving a 3-piece IOL and 66 eyes of 52 patients receiving a 1-piece IOL. Randomized chart review of all patients who underwent uncomplicated phacoemulsification with in-the-bag IOL implantation with either a 3-piece hydrophobic acrylic IOL (Tecnis ZA9003) or a 1-piece hydrophobic acrylic IOL (Tecnis ZCB00) between 2006 and 2014 in a tertiary ophthalmology care centre in Mississauga, Ontario. Preoperative visual acuity and refraction, anterior chamber depth, axial length, IOL design and power, predicted refraction, postoperative visual acuity, and refraction were recorded. Mean absolute error was 0.40 ± 0.27 in the ZA9003 group and 0.39 ± 0.35 in the ZCB00 group, with no statistically significant difference between the 2 IOLs (p = 0.86). Mean arithmetic error was 0.11 ± 0.47 D in the ZA9003 group and 0.01 ± 0.47 D in the ZCB00 group (p = 0.019). In the ZA9003 group, 23 (38%), 42 (70%), and 52 (87%) of 60 eyes were within 0.25, 0.50, and 0.75 D, respectively, of predicted postoperative refraction. In the ZCB00 group, 32 (48%), 46 (70%), and 56 (85%) of 66 eyes were within 0.25, 0.50, and 0.75 D, respectively, of predicted postoperative refraction (p = 0.2836, p = 1.00, p = 0.8044). The ZA9003 and the ZCB00 have similar mean absolute error and thus appear to have similar refractive predictability. Copyright © 2017 Canadian Ophthalmological Society. Published by Elsevier Inc. All rights reserved.

  11. Medical error

    African Journals Online (AJOL)

    QuickSilver

    is only when mistakes are recognised that learning can occur...All our previous medical training has taught us to fear error, as error is associated with blame. This fear may lead to concealment and this is turn can lead to fraud'. How real this fear is! All of us, during our medical training, have had the maxim 'prevention is.

  12. Estimating index of refraction for material identification in comparison to existing temperature emissivity separation algorithms

    Science.gov (United States)

    Martin, Jacob A.; Gross, Kevin C.

    2016-05-01

    As off-nadir viewing platforms become increasingly prevalent in remote sensing, material identification techniques must be robust to changing viewing geometries. Current identification strategies generally rely on estimating reflectivity or emissivity, both of which vary with viewing angle. Presented here is a technique, leveraging polarimetric and hyperspectral imaging (P-HSI), to estimate index of refraction which is invariant to viewing geometry. Results from a quartz window show that index of refraction can be retrieved to within 0.08 rms error from 875-1250 cm-1 for an amorphous material. Results from a silicon carbide (SiC) wafer, which has much sharper features than quartz glass, show the index of refraction can be retrieved to within 0.07 rms error. The results from each of these datasets show an improvement when compared with a maximum smoothness TES algorithm.

  13. Refractive and corneal astigmatism in white school children in northern ireland.

    Science.gov (United States)

    O'Donoghue, Lisa; Rudnicka, Alicja R; McClelland, Julie F; Logan, Nicola S; Owen, Christopher G; Saunders, Kathryn J

    2011-06-08

    To study the prevalence of and relation between refractive and corneal astigmatism in white school children in Northern Ireland and to describe the association between refractive astigmatism and refractive error. Stratified random clustering was used to recruit 1053 white children, 392 aged 6-7 years and 661 aged 12-13 years. Eye examinations included cycloplegic autorefraction and ocular biometric measures of axial length and corneal curvature. The prevalence of refractive astigmatism (≥ 1 DC) did not differ significantly between 6- to 7-year-old children (24%; 95% confidence interval [CI], 19-30) and 12- to 13-year-old children (20%; 95% CI, 14-25). The prevalence of corneal astigmatism (≥ 1 DC) also did not differ significantly between 6- to 7-year-old children (29%; 95% CI, 24-34) and 12- to 13-year-old children (25%; 95% CI, 21-28). While levels of refractive astigmatism and corneal astigmatism were similar, refractive astigmatism was predominantly oblique (76%; 95% CI, 67-85, of 6- to 7-year-olds; 59%; 95% CI, 48-70, of 12- to 13-year-olds), but corneal astigmatism was predominantly with-the-rule (80%; 95% CI, 72-87, of 6- to 7-year-olds; 82%; 95% CI, 74-90, of 12- to 13-year-olds). The prevalence of refractive astigmatism was associated with increasing myopia and hyperopia. This study is the first to provide robust population-based data on the prevalence of astigmatism in white school children in the United Kingdom. The prevalence of refractive astigmatism and corneal astigmatism is stable between 6 and 7 years and 12 and 13 years, although this finding would need to be confirmed by prospective studies. There is a high prevalence of refractive and corneal astigmatism which is associated with ametropia.

  14. Influence of refraction index strength on the light propagation in dielectrics material with periodic refraction index

    Energy Technology Data Exchange (ETDEWEB)

    Hidayat, Arif, E-mail: arif.hidayat.fmipa@um.ac.id; Latifah, Eny; Kurniati, Diana; Wisodo, Hari [Nonlinear Optics Group Department of Physics, Faculty of Mathematics and Natural Sciences State University of Malang (Indonesia)

    2016-04-19

    This study investigated the influence of refraction index strength on the light propagation in refraction index-varied dielectric material. This dielectric material served as photonic lattice. The behavior of light propagation influenced by variation of refraction index in photonic lattice was investigated. Modes of the guiding light were determined numerically using squared-operator iteration method. It was found that the greater the strength of refraction index, the smaller the guiding modes.

  15. Effect of refractive factors on myopia in college students

    Directory of Open Access Journals (Sweden)

    Li Wang

    2014-11-01

    Full Text Available AIM: To examin college students part of refractive features(corneal curvature, axial length, and understand their impact on college students myopia.METHODS: In 456 college students(912 eyeswith myopia, cycloplegic retinoscopy optometry was used to measure the refractive error, corneal curvature, and axial length. The data were conducted and analyzed.RESULTS: In 456 cases(912 eyeswith myopia, diopter of 524 eyes was less then -3.00DS, accounting for 57.5%, -3.25~-6.00DS was in 265 eyes(29.1%and 123 eyes were more than -6.25DS, accounting for 13.5%. The mean axial length was significantly different between high myopia and low to moderate myopia(PPCONCLUSION: Students with low myopia was for most, accounting for 57.5%. The incidence of myopia in girls was more than that in boys. This situation may be related to female puberty earlier than boys. There is no evidence that myopia in students of moderate or low myopia group is due to axial extension. It probably caused by unbalanced curvature of refraction elements and matching disorders. In the high myopia group, myopia mainly dues to axial myopia growth.

  16. Measurements of photoinduced refractive index changes in ...

    Indian Academy of Sciences (India)

    Abstract. We report the pump–probe measurements of nonlinear refractive index changes in photochromic bacteriorhodopsin films. The photoinduced absorption is caused by pump beam at 532 nm and the accompanying refractive index changes are studied using a probe beam at 633 nm. The proposed technique is ...

  17. Microstructured optical fiber refractive index sensor

    DEFF Research Database (Denmark)

    Town, Graham E.; McCosker, Ravi; Yuan, Scott Wu

    2010-01-01

    We describe a dual-core microstructured optical fiber designed for refractive index sensing of fluids. We show that by using the exponential dependence of intercore coupling on analyte refractive index, both large range and high sensitivity can be achieved in the one device. We also show...

  18. Effect of cycloplegia on the refractive status of children: the Shandong children eye study.

    Directory of Open Access Journals (Sweden)

    Yuan Yuan Hu

    Full Text Available To determine the effect of 1% cyclopentolate on the refractive status of children aged 4 to 18 years.Using a random cluster sampling in a cross-sectional school-based study design, children with an age of 4-18 years were selected from kindergardens, primary schools, junior and senior high schools in a rural county and a city. Auto-refractometry was performed before and after inducing cycloplegia which was achieved by 1% cyclopentolate eye drops.Out of 6364 eligible children, data of 5999 (94.3% children were included in the statistical analysis. Mean age was 10.0±3.3 years (range: 4-18 years. Mean difference between cycloplegic and non-cycloplegic refractive error (DIFF was 0.78±0.79D (median: 0.50D; range: -1.00D to +10.75D. In univariate analysis, DIFF decreased significantly with older age (P<0.001;correlation coefficient r:-0.24, more hyperopic non-cycloplegic refractive error (P<0.001;r = 0.13 and more hyperopic cycloplegic refractive error (P<0.001;r = 0.49. In multivariate analysis, higher DIFF was associated with higher cycloplegic refractive error (P<0.001; standardized regression coefficient beta:0.50; regression coefficient B: 0.19; 95% confidence interval (CI: 0.18, 0.20, followed by lower intraocular pressure (P<0.001; beta: -0.06; B: -0.02; 95%CI: -0.03, -0.01, rural region of habitation (P = 0.001; beta: -0.04; B: -0.07; 95%CI: -0.11, -0.03, and, to a minor degree, with age (P = 0.006; beta: 0.04; B: 0.009; 95%CI: 0.003, 0.016. 66.4% of all eyes with non-cycloplegic myopia (≤-0.50D remained myopic after cycloplegia while the remaining 33.6% of eyes became emmetropic (18.0% or hyperopic (15.7% under cycloplegia. Prevalence of emmetropia decreased from 37.5% before cycloplegia to 19.8% after cycloplegia while the remaining eyes became hyperopic under cycloplegia.The error committed by using non-cycloplegic versus cycloplegic refractometry in children with mid to dark-brown iris color decreased with older age, and in parallel

  19. Einstein's error

    International Nuclear Information System (INIS)

    Winterflood, A.H.

    1980-01-01

    In discussing Einstein's Special Relativity theory it is claimed that it violates the principle of relativity itself and that an anomalous sign in the mathematics is found in the factor which transforms one inertial observer's measu