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Sample records for astigmatism

  1. Optics of astigmatism and retinal image quality

    OpenAIRE

    Vilaseca, M.; Díaz-Doutón, F.; Luque, S. O.; Aldaba, M.; Arjona, M.; Pujol, J.

    2012-01-01

    In the first part of this chapter, the optical condition of astigmatism is defined. The main causes and available classifications of ocular astigmatism are briefly described. The most relevant optical properties of image formation in an astigmatic eye are analysed and compared to that of an emmetropic eye and an eye with spherical ametropia. The spectacle prescription and axis notation for astigmatism are introduced, and the correction of astigmatism by means of lenses is briefly described. ...

  2. Anterior and Posterior Corneal Astigmatism after Refractive Lenticule Extraction for Myopic Astigmatism

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    Kazutaka Kamiya

    2015-01-01

    Full Text Available Purpose. To assess the amount and the axis orientation of anterior and posterior corneal astigmatism after refractive lenticule extraction (ReLEx for myopic astigmatism. Methods. We retrospectively examined 53 eyes of 53 consecutive patients (mean age ± standard deviation, 33.2 ± 6.5 years undergoing ReLEx to correct myopic astigmatism (manifest cylinder = 0.5 diopters (D. Power vector analysis was performed with anterior and posterior corneal astigmatism measured with a rotating Scheimpflug system (Pentacam HR, Oculus and refractive astigmatism preoperatively and 3 months postoperatively. Results. Anterior corneal astigmatism was significantly decreased, measuring 1.42 ± 0.73 diopters (D preoperatively and 1.11 ± 0.53 D postoperatively (p<0.001, Wilcoxon signed-rank test. Posterior corneal astigmatism showed no significant change, falling from 0.44 ± 0.12 D preoperatively to 0.42 ± 0.13 D postoperatively (p=0.18. Refractive astigmatism decreased significantly, from 0.92 ± 0.51 D preoperatively to 0.27 ± 0.44 D postoperatively (p<0.001. The anterior surface showed with-the-rule astigmatism in 51 eyes (96% preoperatively and 48 eyes (91% postoperatively. By contrast, the posterior surface showed against-the-rule astigmatism in all eyes preoperatively and postoperatively. Conclusions. The surgical effects were largely attributed to the astigmatic correction of the anterior corneal surface. Posterior corneal astigmatism remained unchanged even after ReLEx for myopic astigmatism.

  3. Distribution of posterior corneal astigmatism according to axis orientation of anterior corneal astigmatism.

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    Toshiyuki Miyake

    Full Text Available To investigate the distribution of posterior corneal astigmatism in eyes with with-the-rule (WTR and against-the-rule (ATR anterior corneal astigmatism.We retrospectively examined six hundred eight eyes of 608 healthy subjects (275 men and 333 women; mean age ± standard deviation, 55.3 ± 20.2 years. The magnitude and axis orientation of anterior and posterior corneal astigmatism were determined with a rotating Scheimpflug system (Pentacam HR, Oculus when we divided the subjects into WTR and ATR anterior corneal astigmatism groups.The mean magnitudes of anterior and posterior corneal astigmatism were 1.14 ± 0.76 diopters (D, and 0.37 ± 0.19 D, respectively. We found a significant correlation between the magnitudes of anterior and posterior corneal astigmatism (Pearson correlation coefficient r = 0.4739, P<0.001. In the WTR anterior astigmatism group, we found ATR astigmatism of the posterior corneal surface in 402 eyes (96.6%. In the ATR anterior astigmatism group, we found ATR posterior corneal astigmatism in 82 eyes (73.9%. Especially in eyes with ATR anterior corneal astigmatism of 1 D or more and 1.5 D or more, ATR posterior corneal astigmatism was found in 28 eyes (59.6% and 9 eyes (42.9%, respectively.WTR anterior astigmatism and ATR posterior astigmatism were found in approximately 68% and 91% of eyes, respectively. The magnitude and the axis orientation of posterior corneal astigmatism were not constant, especially in eyes having high ATR anterior corneal astigmatism, as is often the case in patients who have undergone toric IOL implantation.

  4. A design of PAL with astigmatism

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    Wei, Yefei; Xiang, Huazhong; Zhu, Tianfeng; Chen, Jiabi

    2015-08-01

    Progressive addition lens (PAL) is designed for those who suffer from myopia and presbyopia to have a clear vision from a far distance to a nearby distance. Additionally there are many people that also suffer from astigmatism and need to be corrected. The cylinder power can't be simply added to the diopter of the PAL directly, because the diopter of the PAL needs to be changed smoothly. A methods has been proposed in this article to solve the problem, the freeform surface height of a PAL without astigmatism and the cylindrical lens surface height for the correction of astigmatism are calculated separately. The both two surface heights were added together, then the final surface is produced and shown with the both properties of PALs and cylindrical lenses used to correct the astigmatism.

  5. Tubular astigmatism-tunable fluidic lens.

    Science.gov (United States)

    Kopp, Daniel; Zappe, Hans

    2016-06-15

    We demonstrate a new means to fabricate three-dimensional liquid lenses which may be tuned in focal length and astigmatism. Using actuation by electrowetting-on-dielectrics, astigmatism in arbitrary directions may be tuned independently, with almost no cross talk between orthogonal orientations. The lens is based on electrodes structured on planar polyimide foils and subsequently rolled, enabling high-resolution patterning of complex electrodes along the azimuthal and radial directions of the lens. Based on a design established through fluidic and optical simulations, the astigmatism tuning is experimentally verified by a change of the corresponding Zernike coefficients measured using a Shack-Hartmann wavefront sensor. It was seen that the back focal length can be tuned by 5 mm and 0° and 45° astigmatism by 3 μm through application of voltages in the range of 50  Vrms. It was observed that the cross talk with other aberrations is very low, suggesting a novel means for astigmatism control in imaging systems.

  6. Tubular astigmatism-tunable fluidic lens.

    Science.gov (United States)

    Kopp, Daniel; Zappe, Hans

    2016-06-15

    We demonstrate a new means to fabricate three-dimensional liquid lenses which may be tuned in focal length and astigmatism. Using actuation by electrowetting-on-dielectrics, astigmatism in arbitrary directions may be tuned independently, with almost no cross talk between orthogonal orientations. The lens is based on electrodes structured on planar polyimide foils and subsequently rolled, enabling high-resolution patterning of complex electrodes along the azimuthal and radial directions of the lens. Based on a design established through fluidic and optical simulations, the astigmatism tuning is experimentally verified by a change of the corresponding Zernike coefficients measured using a Shack-Hartmann wavefront sensor. It was seen that the back focal length can be tuned by 5 mm and 0° and 45° astigmatism by 3 μm through application of voltages in the range of 50  Vrms. It was observed that the cross talk with other aberrations is very low, suggesting a novel means for astigmatism control in imaging systems. PMID:27304276

  7. Selective suture cutting for control of astigmatism following cataract surgery

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    Bansal R

    1992-01-01

    Full Text Available Use of 10-0 monofilament nylon in ECCE cataract surgery leads to high with the rule astigmatism. Many intraoperative and post operative methods have been used to minimise post operative astigmatism. We did selective suture cutting in 38 consecutive patients. Mean keratometric astigmatism at three and six weeks post operative was 5.76 and 5.42 dioptres (D respectively. 77.5% of eyes had astigmatism above 2 D. Selective suture cutting along the axis of the plus high cylinder was done after six weeks of surgery. Mean post suture cutting keratometric astigmatism was 3.3 D and 70% of the eyes had astigmatism below 2 D. After 3 months of surgery mean keratometric astigmatism was reduced to 1.84 D. Axis of the astigmatism also changed following suture cutting. 40% of the eyes showed improvement in their Snellen acuity following reduction in the cylindrical power.

  8. Three methods for correction of astigmatism during phacoemulsification

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    Hossein Mohammad-Rabei

    2016-01-01

    Conclusion: There was no significant difference in astigmatism reduction among the three methods of astigmatism correction during phacoemulsification. Each of these methods can be used at the discretion of the surgeon.

  9. Rectangular Laser Resonators with Astigmatic Compensation

    DEFF Research Database (Denmark)

    Skettrup, Torben

    2005-01-01

    An investigation of rectangular resonators with a view to the compensation of astigmatism has been performed. In order to have beam waists placed at the same positions in the tangential and sagittal planes, pairs of equal mirrors were considered. It was found that at least two concave mirrors...... are necessary to obtain compensation. Four-concave-mirror systems are most stable close to the quadratic geometry, although the symmetric quadratic resonator itself cannot be compensated for astigmatism. Using four equal concave mirrors, compensation of astigmatism can be obtained in two arms at the same time....... Usually several stability ranges are found for four-mirror resonators with pair-wise equal mirrors, and it is possible with these systems to obtain small compensated beam waist radii suitable for frequency conversion. Relevant formulae are given and several relevant examples are shown using simulation...

  10. Astigmatism in relation to length and site of corneal lacerations

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    Srihari Atti

    2016-01-01

    Conclusions: The corneal astigmatism depends upon the length and site of corneal laceration. Severity of astigmatism was directly proportion to the length of corneal laceration. The wound was nearer to the centre of the cornea, the greater was the astigmatism. [Int J Res Med Sci 2016; 4(1.000: 165-168

  11. Optical advantages of astigmatic aberration corrected heliostats

    Science.gov (United States)

    van Rooyen, De Wet; Schöttl, Peter; Bern, Gregor; Heimsath, Anna; Nitz, Peter

    2016-05-01

    Astigmatic aberration corrected heliostats adapt their shape in dependence of the incidence angle of the sun on the heliostat. Simulations show that this optical correction leads to a higher concentration ratio at the target and thus in a decrease in required receiver aperture in particular for smaller heliostat fields.

  12. Surgical management of astigmatism with toric intraocular lenses

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    Bruna V. Ventura

    2014-04-01

    Full Text Available Correction of corneal astigmatism is a key element of cataract surgery, since post-surgical residual astigmatism can compromise the patient's uncorrected visual acuity. Toric intraocular lenses (IOLs compensate for corneal astigmatism at the time of surgery, correcting ocular astigmatism. They are a predictable treatment. However, accurate measurement of corneal astigmatism is mandatory for choosing the correct toric IOL power and for planning optimal alignment. When calculating the power of toric IOLs, it is important to consider anterior and posterior corneal astigmatism, along with the surgically induced astigmatism. Accurate toric lens alignment along the calculated meridian is also crucial to achieve effective astigmatism correction. There are several techniques to guide IOL alignment, including the traditional manual marking technique and automated systems based on anatomic and topographic landmarks. The aim of this review is to provide an overview on astigmatism management with toric IOLs, including relevant patient selection criteria, corneal astigmatism measurement, toric IOL power calculation, toric IOL alignment, clinical outcomes and complications.

  13. Effects of posterior corneal astigmatism on the accuracy of AcrySof toric intraocular lens astigmatism correction

    Science.gov (United States)

    Zhang, Bin; Ma, Jing-Xue; Liu, Dan-Yan; Guo, Cong-Rong; Du, Ying-Hua; Guo, Xiu-Jin; Cui, Yue-Xian

    2016-01-01

    AIM To evaluate the effects of posterior corneal surface measurements on the accuracy of total estimated corneal astigmatism. METHODS Fifty-seven patients with toric intraocular lens (IOL) implantation and posterior corneal astigmatism exceeding 0.5 diopter were enrolled in this retrospective study. The keratometric astigmatism (KA) and total corneal astigmatism (TA) were measured using a Pentacam rotating Scheimpflug camera to assess the outcomes of AcrySof IOL implantation. Toric IOLs were evaluated in 26 eyes using KA measurements and in 31 eyes using TA measurements. Preoperative corneal astigmatism and postoperative refractive astigmatism were recorded for statistical analysis. The cylindrical power of toric IOLs was estimated in all eyes. RESULTS In all cases, the difference of toric IOL astigmatism magnitude between KA and TA measurements for the estimation of preoperative corneal astigmatism was statistically significant. Of a total of 57 cases, the 50.88% decreased from Tn to Tn-1, and 10.53% decreased from Tn to Tn-2. In all cases, 5.26% increased from Tn to Tn+1. The mean postoperative astigmatism within the TA group was significantly lower than that in the KA group. CONCLUSION The accuracy of total corneal astigmatism calculations and the efficacy of toric IOL correction can be enhanced by measuring both the anterior and posterior corneal surfaces using a Pentacam rotating Scheimpflug camera. PMID:27672591

  14. Kerr-lens Mode Locking Without Nonlinear Astigmatism

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    Yefet, Shi; Pe'er, Avi

    2013-01-01

    We demonstrate a Kerr-lens mode locked folded cavity using a planar (non-Brewster) Ti:sapphire crystal as a gain and Kerr medium, thus cancelling the nonlinear astigmatism caused by a Brewster cut Kerr medium. Our method uses a novel cavity folding in which the intra-cavity laser beam propagates in two perpendicular planes such that the astigmatism of one mirror is compensated by the other mirror, enabling the introduction of an astigmatic free, planar-cut gain medium. We demonstrate that this configuration is inherently free of nonlinear astigmatism, which in standard cavity folding needs a special power specific compensation.

  15. Effect of astigmatism on spectral switches of partially coherent beams

    Institute of Scientific and Technical Information of China (English)

    Zhao Guang-Pu; Xiao Xi; Lü Bai-Da

    2004-01-01

    A detailed study of the spectrum of partially coherent beams diffracted at an astigmatic aperture lens is performed.Considerable attention is paid to the effect of astigmatism on spectral switches of polychromatic Gaussian Schell-model beams. It is shown that the spectral switch can also take place in the vicinity of intensity minimum in a geometrical focal plane for the astigmatic case, but the astigmatism of the lens and the spatial correlation of the beam affect the critical position uc, spectral minimum Smin, and transition height △ of spectral switches.

  16. The effects of lateral head tilt on ocular astigmatic axis

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    Hamid Fesharaki

    2014-01-01

    Conclusion: Any minimal angle of head tilt may cause erroneous measurement of astigmatic axis and should be avoided during refraction. One cannot rely on the compensatory function of ocular counter-torsion during the refraction.

  17. Treatment of corneal astigmatism with the new small-incision lenticule extraction (SMILE) laser technique: Is treatment of high degree astigmatism equally accurate, stable and safe as treatment of low degree astigmatism?

    DEFF Research Database (Denmark)

    Hansen, Rasmus Søgaard; Grauslund, Jakob; Lyhne, Niels;

    Field: Ophthalmology Introduction: SMILE has proven effective in treatment of myopia and low degrees of astigmatism (less than 2 dioptres (D)), but there are no studies on treatment of high degrees of astigmatism (2 or more D). The aim of this study was to compare results after SMILE treatment...... for low or high degrees of astigmatism concerning accuracy, stability, and safety. Methods: Retrospective study of 1017 eyes treated with SMILE for myopia with low astigmatism or myopia with high astigmatism from 2011-2013 at the Department of Ophthalmology, Odense University Hospital, Denmark. Inclusion...... criteria were: Best spectacle-corrected visual acuity (BSCVA) of 20/25 or better on Snellen chart, and no other ocular condition than myopia with or without astigmatism. Results: In total 660 eyes completed the 3 months follow-up examination, in which 536 eyes had pre-operatively low astigmatism (mean...

  18. Quasi-Bessel beams from asymmetric and astigmatic illumination sources.

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    Müller, Angelina; Wapler, Matthias C; Schwarz, Ulrich T; Reisacher, Markus; Holc, Katarzyna; Ambacher, Oliver; Wallrabe, Ulrike

    2016-07-25

    We study the spatial intensity distribution and the self-reconstruction of quasi-Bessel beams produced from refractive axicon lenses with edge emitting laser diodes as asymmetric and astigmatic illumination sources. Comparing these to a symmetric mono-mode fiber source, we find that the asymmetry results in a transition of a quasi-Bessel beam into a bow-tie shaped pattern and eventually to a line shaped profile at a larger distance along the optical axis. Furthermore, we analytically estimate and discuss the effects of astigmatism, substrate modes and non-perfect axicons. We find a good agreement between experiment, simulation and analytic considerations. Results include the derivation of a maximal axicon angle related to astigmatism of the illuminating beam, impact of laser diode beam profile imperfections like substrate modes and a longitudinal oscillation of the core intensity and radius caused by a rounded axicon tip. PMID:27464190

  19. Interaction of axial and oblique astigmatism in theoretical and physical eye models.

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    Liu, Tao; Thibos, Larry N

    2016-09-01

    The interaction between oblique and axial astigmatism was investigated analytically (generalized Coddington's equations) and numerically (ray tracing) for a theoretical eye model with a single refracting surface. A linear vector-summation rule for power vector descriptions of axial and oblique astigmatism was found to account for their interaction over the central 90° diameter of the visual field. This linear summation rule was further validated experimentally using a physical eye model measured with a laboratory scanning aberrometer. We then used the linear summation rule to evaluate the relative contributions of axial and oblique astigmatism to the total astigmatism measured across the central visual field. In the central visual field, axial astigmatism dominates because the oblique astigmatism is negligible near the optical axis. At intermediate eccentricities, axial and oblique astigmatism may have equal magnitude but orthogonal axes, which nullifies total astigmatism at two locations in the visual field. At more peripheral locations, oblique astigmatism dominates axial astigmatism, and the axes of total astigmatism become radially oriented, which is a trait of oblique astigmatism. When eccentricity is specified relative to a foveal line-of-sight that is displaced from the eye's optical axis, asymmetries in the visual field map of total astigmatism can be used to locate the optical axis empirically and to estimate the relative contributions of axial and oblique astigmatism at any retinal location, including the fovea. We anticipate the linear summation rule will benefit many topics in vision science (e.g., peripheral correction, emmetropization, meridional amblyopia) by providing improved understanding of how axial and oblique astigmatism interact to produce net astigmatism. PMID:27607493

  20. Astigmatically compensated cw dye laser resonators using lenses

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    Hueffer, W.; Schieder, R.; Brinkmann, U. (Koeln Univ. (Germany, F.R.). 1. Physikalisches Inst.)

    1978-01-01

    The compensation of the astigmatism of Brewster-angled dye cells can be performed with lenses as well as with spherical mirrors. The advantages of cw dye laser resonators using lenses lie in the linear configuration of the optics and the convenient adjustability of astigmatism compensation. An output efficiency of 30% already at 1.6 W pumping power has been observed. In addition, ring laser resonators with lenses have been investigated and they delivered up to 400mW single mode power in travelling wave operation at less than 2 W pumping power.

  1. An astigmatic corrected target-aligned heliostat for high concentration

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    Zaibel, R.; Dagan, E.; Karni, J. [Solar Research Facility, The Weizmann Institute of Science, Rehovot (Israel); Ries, Harald [Ludwig-Maximilians-Universitaet, Sektion Physik, Munich (Germany)

    1995-05-28

    Conventional heliostats suffer from astigmatism for non-normal incidence. For tangential rays the focal length is shortened while for sagittal rays it is longer than the nominal focal length. Due to this astigmatism it is impossible to produce a sharp image of the sun, and the rays will be spread over a larger area. In order to correct this the heliostat should have different curvature radii along the sagittal and tangential direction in the heliostat plane just like a non axial part of a paraboloid. In conventional heliostats, where the first axis, fixed with respect to the ground, is vertical while the second, fixed with respect to the reflector surface, is horizontal, such an astigmatism correction is not practical because the sagittal and tangential directions rotate with respect to the reflector. We suggest an alternative mount where the first axis is oriented towards the target. The second axis, perpendicular to the first and tangent to the reflector, coincides with the tangential direction. With this mounting sagittal and tangential direction are fixed with respect to the reflector during operation. Therefore a partial astigmatism compensation is possible. We calculate the optimum correction and show the performance of the heliostat. We also show predicted yearly average concentrations

  2. Defocus and twofold astigmatism correction in HAADF-STEM

    International Nuclear Information System (INIS)

    A new simultaneous autofocus and twofold astigmatism correction method is proposed for High Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM). The method makes use of a modification of image variance, which has already been used before as an image quality measure for different types of microscopy, but its use is often justified on heuristic grounds. In this paper we show numerically that the variance reaches its maximum at Scherzer defocus and zero astigmatism. In order to find this maximum a simultaneous optimization of three parameters (focus, x- and y-stigmators) is necessary. This is implemented and tested on a FEI Tecnai F20. It successfully finds the optimal defocus and astigmatism with time and accuracy, compared to a human operator. -- Research highlights: → A new simultaneous defocus and astigmatism correction method is proposed. → The method does not depend on the image Fourier transform. → The method does not require amorphous area of the sample. → The method is tested numerically as well, as for the real-world application.

  3. Success rates in the correction of astigmatism with toric and spherical soft contact lens fittings

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    Sevda Aydin Kurna

    2010-08-01

    Full Text Available Sevda Aydin Kurna, Tomris Şengör, Murat Ün, Suat AkiFatih Sultan Mehmet Education and Research Hospital, Ophthalmology Clinics, lstanbul, TurkeyObjectives: To evaluate success rates in the correction of astigmatism with toric and spherical soft contact lens fitting.Methods: 30 patients with soft toric lenses having more than 1.25 D of corneal astigmatism (25 eyes; Group A or having 0.75–1.25 D of corneal astigmatism (22 eyes; Group B and 30 patients with soft spheric lenses having 0.75–1.25 D of corneal astigmatism (28 eyes; Group C or less than 0.75 D of corneal astigmatism (23 eyes; Group D were included in the study. Corrected and uncorrected monocular visual acuity measurement with logMAR, biomicroscopic properties, autorefractometry and corneal topography were performed for all patients immediately before and at least 20 minutes after the application of contact lenses. ­Success of contact lens fitting was evaluated by three parameters: astigmatic neutralization, visual success, and retinal deviation.Results: After soft toric lens application, spheric dioptres, cylindric and keratometric astigmatism, and retinal deviation decreased significantly in Groups A and B (P < 0.05. In Group C, spheric dioptres and retinal deviation decreased (P < 0.05, while cylindric and keratometric astigmatism did not change significantly (P > 0.05. In Group D, spheric dioptres, retinal deviation, and cylindric astigmatism decreased (P < 0.05. Keratometric astigmatism did not change significantly (P > 0.05 and astigmatic neutralization even increased.Conclusions: Visual acuity and residual spherical equivalent refraction remained between tolerable limits with the use of toric and spheric contact lenses. Spherical lenses failed to mask corneal toricity during topography, while toric lenses caused central neutralization and decrease in corneal cylinder in low and moderate astigmatic eyes.Keywords: astigmatism, soft toric lenses, soft spheric lenses

  4. [Results of refractive surgery in hyperopic and combined astigmatism].

    Science.gov (United States)

    Vlaicu, Valeria

    2013-01-01

    The refractive surgery includes a lot of procedures for changing the refraction of the eye to obtain a better visual acuity with no glasses or contact lenses. LASIK is the most commonly performed laser refractive surgery today. The goal is to present the postoperative evolution of the refraction and visual acuity after LASIK for Mixed and Hyperopic Astigmatism. The results show that LASIK is safe and predictible if we have well performed interventions and well-selected patients.

  5. Focusing properties of Gaussian Schell-model beams by an astigmatic aperture lens

    Institute of Scientific and Technical Information of China (English)

    Pan Liu-Zhan; Ding Chao-Liang

    2007-01-01

    This paper studies the focusing properties of Gaussian Schell-model (GSM) beams by an astigmatic aperture lens.It is shown that the axial irradiance distribution, the maximum axial irradiance and its position of focused GSM beams by an astigmatic aperture lens depend upon the astigmatism of the lens, the coherence of partially coherent light, the truncation parameter of the aperture and Fresnel number. The numerical calculation results are given to illustrate how these parameters affect the focusing property.

  6. Correction of high amounts of astigmatism through orthokeratology. A case report

    OpenAIRE

    Baertschi, Michael; Wyss, Michael

    2010-01-01

    The purpose of this case report is to introduce a method for a successful treatment of high astigmatism with a new orthokeratology design, called FOKX (Falco Kontaktlinsen, Switzerland). This novel toric orthokeratology contact lens design, the fitting approach and the performance of FOKX lenses will be illustrated in the form of a case report. Correcting astigmatism with orthokeratology offers a new perspective for all patients suffering astigmatism.

  7. Toric Intraocular Lenses in the Correction of Astigmatism During Cataract Surgery

    DEFF Research Database (Denmark)

    Kessel, Line; Andresen, Jens; Tendal, Britta;

    2016-01-01

    TOPIC: We performed a systematic review and meta-analysis to evaluate the benefit and harms associated with implantation of toric intraocular lenses (IOLs) during cataract surgery. Outcomes were postoperative uncorrected distance visual acuity (UCDVA) and distance spectacle independence. Harms were...... evaluated as surgical complications and residual astigmatism. CLINICAL RELEVANCE: Postoperative astigmatism is an important cause of suboptimal UCDVA and need for distance spectacles. Toric IOLs may correct for preexisting corneal astigmatism at the time of surgery. METHODS: We performed a systematic...

  8. Finite element simulation of arcuates for astigmatism correction.

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    Lanchares, Elena; Calvo, Begoña; Cristóbal, José A; Doblaré, Manuel

    2008-01-01

    In order to simulate the corneal incisions used to correct astigmatism, a three-dimensional finite element model was generated from a simplified geometry of the anterior half of the ocular globe. A hyperelastic constitutive behavior was assumed for cornea, limbus and sclera, which are collagenous materials with a fiber structure. Due to the preferred orientations of the collagen fibrils, corneal and limbal tissues were considered anisotropic, whereas the sclera was simplified to an isotropic one assuming that fibrils are randomly disposed. The reference configuration, which includes the initial strain distribution that balances the intraocular pressure, is obtained by an iterative process. Then the incisions are simulated. The final positions of the nodes belonging to the incised meridian and to the perpendicular one are fitted by both radii of curvature, which are used to calculate the optical power. The simulated incisions were those specified by Lindstrom's nomogram [Chu, Y., Hardten, D., Lindquist, T., Lindstrom, R., 2005. Astigmatic keratotomy. Duane's Ophthalmology. Lippincott Williams and Wilkins, Philadelphia] to achieve 1.5, 2.25, 3.0, 4.5 and 6.0D of astigmatic change, using the next values for the parameters: length of 45 degrees , 60 degrees and 90 degrees , an optical zone of 6mm, single or paired incisions. The model gives results similar to those in Lindstrom's nomogram [Chu et al., 2005] and can be considered a useful tool to plan and simulate refractive surgery by predicting the outcomes of different sorts of incisions and to optimize the values for the parameters involved: depth, length, position. PMID:18177656

  9. Quasi two-dimensional astigmatic solitons in soft chiral metastructures.

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    Laudyn, Urszula A; Jung, Paweł S; Karpierz, Mirosław A; Assanto, Gaetano

    2016-01-01

    We investigate a non-homogeneous layered structure encompassing dual spatial dispersion: continuous diffraction in one transverse dimension and discrete diffraction in the orthogonal one. Such dual diffraction can be balanced out by one and the same nonlinear response, giving rise to light self-confinement into astigmatic spatial solitons: self-focusing can compensate for the spreading of a bell-shaped beam, leading to quasi-2D solitary wavepackets which result from 1D transverse self-localization combined with a discrete soliton. We demonstrate such intensity-dependent beam trapping in chiral soft matter, exhibiting one-dimensional discrete diffraction along the helical axis and one-dimensional continuous diffraction in the orthogonal plane. In nematic liquid crystals with suitable birefringence and chiral arrangement, the reorientational nonlinearity is shown to support bell-shaped solitary waves with simple astigmatism dependent on the medium birefringence as well as on the dual diffraction of the input wavepacket. The observations are in agreement with a nonlinear nonlocal model for the all-optical response. PMID:26975651

  10. An astigmatic corrected target-aligned solar concentrator

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    Lando, Mordechai; Kagan, Jacob; Linyekin, Boris; Sverdalov, Ludmila; Pecheny, Grigory; Achiam, Yaakov

    2000-06-01

    Highly concentrated solar energy is required for solar pumping of solid state lasers, and for other applications. High concentration may be obtained by a combination of a primary concentrator with f/ D>2 in addition to a non-imaging concentrator. We have designed and constructed a novel tower primary concentrator. A 3.4 m diameter primary mirror, composed of 61 segments, was mounted on a commercial two-axis positioner. Unlike the common zenith mounting, the positioner fixed axis is directed southwards, pointing at 32° above the horizon. With this novel mounting, the concentrator is the first implementation of the astigmatic corrected target aligned (ACTA) design which flattens the irradiation density variation during the day. The primary mirror segments are each mounted on a separate two-axis mount, and aligned to compensate for astigmatism. The segments are spherically curved with R=17 m radius of curvature, while their vertexes are placed on an R/2=8.5 m radius spherical cap. A four-segment plane mirror reflects the light towards a horizontal focal plane. We have measured the absorbed solar power into a 89×91 mm 2 rectangular aperture and found good agreement with optical design calculations. Peak solar concentration in the focal plane exceeded 400 suns.

  11. Alpins and thibos vectorial astigmatism analyses: proposal of a linear regression model between methods

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    Giuliano de Oliveira Freitas

    2013-10-01

    Full Text Available PURPOSE: To determine linear regression models between Alpins descriptive indices and Thibos astigmatic power vectors (APV, assessing the validity and strength of such correlations. METHODS: This case series prospectively assessed 62 eyes of 31 consecutive cataract patients with preoperative corneal astigmatism between 0.75 and 2.50 diopters in both eyes. Patients were randomly assorted among two phacoemulsification groups: one assigned to receive AcrySof®Toric intraocular lens (IOL in both eyes and another assigned to have AcrySof Natural IOL associated with limbal relaxing incisions, also in both eyes. All patients were reevaluated postoperatively at 6 months, when refractive astigmatism analysis was performed using both Alpins and Thibos methods. The ratio between Thibos postoperative APV and preoperative APV (APVratio and its linear regression to Alpins percentage of success of astigmatic surgery, percentage of astigmatism corrected and percentage of astigmatism reduction at the intended axis were assessed. RESULTS: Significant negative correlation between the ratio of post- and preoperative Thibos APVratio and Alpins percentage of success (%Success was found (Spearman's ρ=-0.93; linear regression is given by the following equation: %Success = (-APVratio + 1.00x100. CONCLUSION: The linear regression we found between APVratio and %Success permits a validated mathematical inference concerning the overall success of astigmatic surgery.

  12. Optical analysis for simplified astigmatic correction of non-imaging focusing heliostat

    Energy Technology Data Exchange (ETDEWEB)

    Chong, K.K. [Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Off Jalan Genting Kelang, Setapak, 53300 Kuala Lumpur (Malaysia)

    2010-08-15

    In the previous work, non-imaging focusing heliostat that consists of m x n facet mirrors can carry out continuous astigmatic correction during sun-tracking with the use of only (m + n - 2) controllers. For this paper, a simplified astigmatic correction of non-imaging focusing heliostat is proposed for reducing the number of controllers from (m + n - 2) to only two. Furthermore, a detailed optical analysis of the new proposal has been carried out and the simulated result has shown that the two-controller system can perform comparably well in astigmatic correction with a much simpler and more cost effective design. (author)

  13. The Comprehensive Control of Astigmatism during and Following Intraocular Lens Implantation.

    Institute of Scientific and Technical Information of China (English)

    1994-01-01

    The operating corneoloscope and Terry operative keratometer were used respectively in 29 and 34 eyes during the intraocular lens implantation to measure the corneal astigmatism qualitatively or quantitatively,so that the tension of incision closure could be adjusted. The surgically induced astigmatism in qualitative group two weeks after the operation was 3. 5 ± 1. 70 D and that in quantitative group was 2. 56±1. 60 D. There were 55.17% and 38. 24% of the eyes with over 2. 00 D corneal astigmatism in qu...

  14. Self-Compensation of Astigmatism in Mode-Cleaners for Advanced Interferometers

    Energy Technology Data Exchange (ETDEWEB)

    Barriga, P; Zhao Chunnong; Ju Li; Blair, David G [School of Physics, University of Western Australia, Crawley, WA6009 (Australia)

    2006-03-02

    Using a conventional mode-cleaner with the output beam taken through a diagonal mirror it is impossible to achieve a non-astigmatic output. The geometrical astigmatism of triangular mode-cleaners for gravitational wave detectors can be self-compensated by thermally induced astigmatism in the mirrors substrates. We present results from finite element modelling of the temperature distribution of the suspended mode-cleaner mirrors and the associated beam profiles. We use these results to demonstrate and present a self-compensated mode-cleaner design. We show that the total astigmatism of the output beam can be reduced to 5x10{sup -3} for {+-}10% variation of input power about a nominal value when using the end mirror of the cavity as output coupler.

  15. SURGICALLY INDUCED ASTIGMATISM AFTER 20G VS 23G PARS PLANA VITRECTOMY

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    Lokabhi Reddy

    2015-05-01

    Full Text Available Pars Plana Vitrectomy is done to clear the Vitreous cavity of the Eye. Trans conjunctival Sutureless Vitrectomy with 23G & 25G has become more popular over the Conventional 20G Vitrectomy in recent times. It has many advantages. Less amount of Surgically Induc ed Astigmatism is one of the Advantages with Sutureless Vitrectomy, which will have the Advantage of Early Visual rehabilitation with better Vision. An interventional comparative study was done between 20G & 23 G Pars Plana Vitrectomy in 2 Groups of 30 pat ients each to assess the amount of Post - Operative Astigmatism. The cases were followed up for 6 months to assess the long term effects. There was a significant difference in immediate Post - Operative Astigmatism. But after some time the difference is much l ess showing that the main advantage on Astigmatism with Trans conjunctival Sutureless Vitrectomy is noted mainly during the first few weeks after the Surgery.

  16. A novel color-LED corneal topographer to assess astigmatism in pseudophakic eyes

    Science.gov (United States)

    Ferreira, Tiago B; Ribeiro, Filomena J

    2016-01-01

    Purpose To assess the accuracy of corneal astigmatism evaluation measured by four techniques, Orbscan IIz®, Lenstar LS900®, Cassini®, and Total Cassini (anterior + posterior surface), in pseudophakic eyes. Patients and methods A total of 30 patients (46 eyes) who had undergone cataract surgery with the implantation of a monofocal intraocular lens (AcrySof IQ) were assessed after surgery. For each eye, subjective assessment of astigmatism and its axis was performed. Minimum, maximum, and mean keratometry and astigmatism and its axis were evaluated using the four measurement techniques. All measurements were compared with the subjective measurements. Agreement between each measurement technique and subjective assessment was evaluated using Bland–Altman plots. Linear regressions were performed and compared. Results Linear regression analysis of astigmatism axis showed very high R2 for all models, with Total Cassini showing the least difference to the unit slope (0.052) and the least difference to a null constant (3.790), although not statistically different from the other models. Regarding astigmatism value, the Cassini and Total Cassini models were similar and statistically better than the Lenstar model. Cassini and Total Cassini showed better J0 compared with Orbscan. Conclusion On linear regression models, Cassini and Total Cassini showed the best performance regarding astigmatism value. Cassini and Total Cassini also showed the least J0 deviation from the Cartesian origin compared with Orbscan, which had the lowest performance. Total corneal measurement with the color LED topographer seems to be a better technique for astigmatism assessment. PMID:27574391

  17. CORNEAL ASTIGMATISM AFTER ECCE: A COMPARATIVE STUDY BETWEEN SILK VERSUS NYLON SUTURE

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    Sunita

    2013-11-01

    Full Text Available ABSTRAC T: INTRODUCTION: Cataract as a potent cause of loss of vision in old age persons is probably known since the dawn of human civilization. Post operative astigmatism after cataract extraction remains a big problem for cataract surgeons since Jacques Daviel e ra. Astigmatism is that type of refractive anomaly in which no point focus is formed owing to the unequal refraction of the incident light by the diopteric system of the eye in different meridians. The goal of modern cataract surgery is to produce a pseudo phakic with the quality of vision of a normal phakic eye. Various studies to find out any effect of IOL on post operative astigmatism were carried out but results are controversial. MATERIAL AND METHODS: 60 patients suffering from cataract and fit for extr action were enlisted during the month of August 2008 to February 2009. The general, physical and local examination including preoperative Keratometry, vision and tension were recorded. RESULTS: In the present study, male patients were 38 (63% and female p atients were 22 (37%. Out of the total 60 cases studied, corneo - scleral section of 28 cases (47% were sutured with 10 - 0 nylon suture (Group A while sections of 32 cases were sutured with 8 - 0 black virgin silk suture (Group B.Out of 28 cases of Group A, interrupted sutures were applied in 14 cases (50% (Group A 1 . Cross interrupted sutures were applied in 9 cases (32% Group A 2 , while bootlace continuous sutures were applied in 5 cases (18% (Group A 3 . Out of 32 cases of Group B, interrupted sutures we re applied in 26 cases (80% (Group B 1 , cross interrupted were applied in 3 cases (10% (Group B 2 , while bootlace continuous suture were applied in 3 cases (Group B 3 . In the present series, 19 cases (31% showed with the rule astigmatism, 21 cases (36% showed astigmatism against the rule and 20 cases (33% showed no astigmatism preoperatively, 16 cases were in the range of 0.50D to 1.0D and 12 cases were in the range of 1

  18. Preoperative corneal astigmatism among adult patients with cataract in Northern Nigeria

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    Mohammed Isyaku

    2014-01-01

    Full Text Available The prevalence and nature of corneal astigmatism among patients with cataract has not been well-documented in the resident African population. This retrospective study was undertaken to investigate preexisting corneal astigmatism in adult patients with cataract. We analyzed keratometric readings acquired by manual Javal-Schiotz keratometry before surgery between January 1, 2011 and December 31, 2011. There were 3,169 patients (3286 eyes aged between 16 and 110 years involved with a Male to female ratio of 1.4:1. Mean keratometry in diopters was K1 = 43.99 and K2 = 43.80. Mean corneal astigmatism was 1.16 diopter and a majority (45.92% of eyes had astigmatism between 1.00 and 1.99 diopters. Two-thirds of the eyes (66.9% in this study had preoperative corneal astigmatism equal to or above 1.00 diopter. Findings will help local cataract surgeons to estimate the potential demand for toric intraocular lenses.

  19. Convergence Insufficiency, Accommodative Insufficiency, Visual Symptoms, and Astigmatism in Tohono O'odham Students

    Science.gov (United States)

    Twelker, J. Daniel; Miller, Joseph M.; Campus, Irene

    2016-01-01

    Purpose. To determine rate of convergence insufficiency (CI) and accommodative insufficiency (AI) and assess the relation between CI, AI, visual symptoms, and astigmatism in school-age children. Methods. 3rd–8th-grade students completed the Convergence Insufficiency Symptom Survey (CISS) and binocular vision testing with correction if prescribed. Students were categorized by astigmatism magnitude (no/low: AI, and presence of symptoms. Analyses determine rate of clinical CI and AI and symptomatic CI and AI and assessed the relation between CI, AI, visual symptoms, and astigmatism. Results. In the sample of 484 students (11.67 ± 1.81 years of age), rate of symptomatic CI was 6.2% and symptomatic AI 18.2%. AI was more common in students with CI than without CI. Students with AI only (p = 0.02) and with CI and AI (p = 0.001) had higher symptom scores than students with neither CI nor AI. Moderate and high astigmats were not at increased risk for CI or AI. Conclusions. With-the-rule astigmats are not at increased risk for CI or AI. High comorbidity rates of CI and AI and higher symptoms scores with AI suggest that research is needed to determine symptomatology specific to CI. PMID:27525112

  20. Toric intraocular lenses for correction of astigmatism in keratoconus and after corneal surgery

    Science.gov (United States)

    Mol, Ilse EMA; Van Dooren, Bart TH

    2016-01-01

    Purpose To describe the results of cataract extraction with toric intraocular lens (IOL) implantation in patients with preexisting astigmatism from three corneal conditions (keratoconus, postkeratoplasty, and postpterygium surgery). Methods Cataract patients with topographically stable, fairly regular (although sometimes very high) corneal astigmatism underwent phacoemulsification with implantation of a toric IOL (Zeiss AT TORBI 709, Alcon Acrysof IQ toric SN6AT, AMO Tecnis ZCT). Postoperative astigmatism and refractive outcomes, as well as visual acuities, vector reduction, and complications were recorded for all eyes. Results This study evaluated 17 eyes of 16 patients with a mean age of 60 years at the time of surgery. Mean follow-up in this study was 12 months. The corrected distance Snellen visual acuity (with spectacles or contact lenses) 12 months postoperatively was 20/32 or better in 82% of eyes. The mean corneal astigmatism was 6.7 diopters (D) preoperatively, and 1.5 D of refractive cylinder at 1-year follow-up. No vision-compromising intra- or postoperative complications occurred and decentration or off-axis alignment of toric IOLs were not observed. Conclusion Phacoemulsification with toric IOL implantation was a safe and effective procedure in the three mentioned corneal conditions. Patient selection, counseling, and IOL placement with optimal astigmatism correction are crucial. PMID:27382249

  1. Toric intraocular lenses for correction of astigmatism in keratoconus and after corneal surgery

    Directory of Open Access Journals (Sweden)

    Mol IEMA

    2016-06-01

    Full Text Available Ilse EMA Mol,1,2 Bart TH Van Dooren1,2 1Department of Ophthalmology, Amphia Hospital, Breda, 2Department of Ophthalmology, Erasmus Medical Center, Rotterdam, the Netherlands Purpose: To describe the results of cataract extraction with toric intraocular lens (IOL implantation in patients with preexisting astigmatism from three corneal conditions (keratoconus, postkeratoplasty, and postpterygium surgery.Methods: Cataract patients with topographically stable, fairly regular (although sometimes very high corneal astigmatism underwent phacoemulsification with implantation of a toric IOL (Zeiss AT TORBI 709, Alcon Acrysof IQ toric SN6AT, AMO Tecnis ZCT. Postoperative astigmatism and refractive outcomes, as well as visual acuities, vector reduction, and complications were recorded for all eyes.Results: This study evaluated 17 eyes of 16 patients with a mean age of 60 years at the time of surgery. Mean follow-up in this study was 12 months. The corrected distance Snellen visual acuity (with spectacles or contact lenses 12 months postoperatively was 20/32 or better in 82% of eyes. The mean corneal astigmatism was 6.7 diopters (D preoperatively, and 1.5 D of refractive cylinder at 1-year follow-up. No vision-compromising intra- or postoperative complications occurred and decentration or off-axis alignment of toric IOLs were not observed.Conclusion: Phacoemulsification with toric IOL implantation was a safe and effective procedure in the three mentioned corneal conditions. Patient selection, counseling, and IOL placement with optimal astigmatism correction are crucial. Keywords: toric intraocular lens, phacoemulsification, corneal astigmatism, keratoconus, postkeratoplasty, postpterygium surgery

  2. Astigmatism compensation in mode-cleaner cavities for the next generation of gravitational wave interferometric detectors

    Energy Technology Data Exchange (ETDEWEB)

    Barriga, Pablo J. [School of Physics, University of Western Australia, Crawley, WA 6009 (Australia)]. E-mail: pbarriga@cyllene.uwa.edu.au; Zhao Chunnong [School of Physics, University of Western Australia, Crawley, WA 6009 (Australia); Blair, David G. [School of Physics, University of Western Australia, Crawley, WA 6009 (Australia)

    2005-06-06

    Interferometric gravitational wave detectors use triangular ring cavities to filter spatial and frequency instabilities from the input laser beam. The next generation of interferometric detectors will use high laser power and greatly increased circulating power inside the cavities. The increased power inside the cavities increases thermal effects in their mirrors. The triangular configuration of conventional mode-cleaners creates an intrinsic astigmatism that can be corrected by using the thermal effects to advantage. In this Letter we show that an astigmatism free output beam can be created if the design parameters are correctly chosen.

  3. Off-Axis Astigmatic Gaussian Beam Combination Beyond the Paraxial Approximation

    Institute of Scientific and Technical Information of China (English)

    GAO Zeng-Hui; L(U) Bai-Da

    2007-01-01

    Taking the off-axis astigmatic Gaussian beam combination as an example, the beam-combination concept is extended to the nonparaxial regime. The closed-form propagation expressions for coherent and incoherent combinations of nonparaxial off-axis astigmatic Gaussian beams with rectangular geometry are derived and illustrated with numerical examples. It is shown that the intensity distributions of the resulting beam depend on the combination scheme and beam parameters in general, and in the paraxial approximation (i.e., for the small f-parameter)our results reduce to the paraxial ones.

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

    Directory of Open Access Journals (Sweden)

    Potvin R

    2016-09-01

    astigmatism as a result of misorientation. The Tecnis Toric IOL appears more likely to be misoriented in a counterclockwise direction; no such bias was observed with the AcrySof Toric, the Trulign® Toric, or the Staar Toric IOLs. Keywords: rotation, AcrySof, Tecnis, toric back-calculator, cylinder

  5. Observation of lasing modes with exotic localized wave patterns from astigmatic large-Fresnel-number cavities.

    Science.gov (United States)

    Lu, T H; Lin, Y C; Liang, H C; Huang, Y J; Chen, Y F; Huang, K F

    2010-02-01

    We investigate the lasing modes in large-Fresnel-number laser systems with astigmatism effects. Experimental results reveal that numerous lasing modes are concentrated on exotic patterns corresponding to intriguing geometries. We theoretically use the quantum operator algebra to construct the wave representation for manifesting the origin of the localized wave patterns. PMID:20125716

  6. Meridional lenticular astigmatism associated with bilateral concurrent uveal metastases in renal cell carcinoma

    Directory of Open Access Journals (Sweden)

    Priluck JC

    2012-11-01

    Full Text Available Joshua C Priluck, Sandeep Grover, KV ChalamDepartment of Ophthalmology, University of Florida College of Medicine, Jacksonville, FL, USAPurpose: To demonstrate a case illustrating meridional lenticular astigmatism as a result of renal cell carcinoma uveal metastases.Methods: Case report with images.Results: Clinical findings and diagnostic testing of a patient with acquired meridional lenticular astigmatism are described. The refraction revealed best-corrected visual acuity of 20/20–1 OD (−2.50 + 0.25 × 090 and 20/50 OS (−8.25 + 3.25 × 075. Bilateral concurrent renal cell carcinoma metastases to the choroid and ciliary body are demonstrated by utilizing ultrasonography, ultrawidefield fluorescein angiography, and unique spectral-domain optical coherence tomography.Conclusions: Metastatic disease should be included in the differential of acquired astigmatism. Spectral-domain optical coherence tomography, ultrawidefield fluorescein angiography, and ultrasonography have roles in delineating choroidal metastases.Keywords: astigmatism, metastasis, optical coherence tomography, renal cell carcinoma

  7. [Results of corneal and total astigmatism estimation by different methods in myopic patients wearing orthokeratology contact lenses].

    Science.gov (United States)

    Tarutta, E P; Aliaeva, O O; Verzhanskaia, T Iu; Milash, S V

    2013-01-01

    Reports have been made that corneal aberrations of all orders, including astigmatism, often significantly increase with the use of night orthokeratology lenses. In this study the dynamic changes of total and corneal astigmatism in myopes using orthokeratology lenses was evaluated by different methods. The study enrolled 38 patients (76 eyes) with low and medium myopia (28 and 48 eyes correspondingly) and initial astigmatism less than 2 diopters. The assessment was made before and in different terms after the patient started to wear orthokeratology lenses. Induced astigmatism (> or =1 diopter) was found in more than 50% of cases. The degree of astigmatism gradually increased from the centre to the periphery within the papillary zone. The maximum values were found within a 4-mm zone ("uptake zone") and minimal - within a 8-mm zone ("equalization zone"). In all patients, despite the presence of induced astigmatism and residual myopia (0.83+/-0.09 diopters in average), distance visual acuity was high enough without an additional correction (0.82+/-0.05 in average). Apparently, in these patients the aberrations (astigmatism in particular) exceed the focal depth. PMID:24137984

  8. Extended depth of focus intra-ocular lens: a solution for presbyopia and astigmatism

    Science.gov (United States)

    Zlotnik, Alex; Raveh, Ido; Ben Yaish, Shai; Yehezkel, Oren; Belkin, Michael; Zalevsky, Zeev

    2010-02-01

    Purpose: Subjects after cataract removal and intra-ocular lens (IOL) implantation lose their accommodation capability and are left with a monofocal visual system. The IOL refraction and the precision of the surgery determine the focal distance and amount of astigmatic aberrations. We present a design, simulations and experimental bench testing of a novel, non-diffractive, non-multifocal, extended depth of focus (EDOF) technology incorporated into an IOL that allows the subject to have astigmatic and chromatic aberrations-free continuous focusing ability from 35cm to infinity as well as increased tolerance to IOL decentration. Methods: The EDOF element was engraved on a surface of a monofocal rigid IOL as a series of shallow (less than one micron deep) concentric grooves around the optical axis. These grooves create an interference pattern extending the focus from a point to a length of about one mm providing a depth of focus of 3.00D (D stands for Diopters) with negligible loss of energy at any point of the focus while significantly reducing the astigmatic aberration of the eye and that generated during the IOL implantation. The EDOF IOL was tested on an optical bench simulating the eye model. In the experimental testing we have explored the characteristics of the obtained EDOF capability, the tolerance to astigmatic aberrations and decentration. Results: The performance of the proposed IOL was tested for pupil diameters of 2 to 5mm and for various spectral illuminations. The MTF charts demonstrate uniform performance of the lens for up to 3.00D at various illumination wavelengths and pupil diameters while preserving a continuous contrast of above 25% for spatial frequencies of up to 25 cycles/mm. Capability of correcting astigmatism of up to 1.00D was measured. Conclusions: The proposed EDOF IOL technology was tested by numerical simulations as well as experimentally characterized on an optical bench. The new lens is capable of solving presbyopia and astigmatism

  9. The approximate analysis of the electromagnetic characters of 3-D radome by complex astigmatic wave theory

    Science.gov (United States)

    Wang, Yueqing; Wu, Guisheng; Chen, Zhenyang

    The complex astigmatic wave, which imitates the 3-D beam in high-frequency, is an effective method to analyze the electromagnetic characters of the 3-D arbitrarily curved radome. A number of calculations for the ellipsoidal sandwich radome are performed, and the stereoscopic graphics of the results are constructed. Comparing with the experiments, it is shown that this method can be used to simplify analysis and optimization design for many kinds of 3-D radome.

  10. Clinical Efficacy of Toric Orthokeratology in Myopic Ado-lescent with Moderate to High Astigmatism

    Institute of Scientific and Technical Information of China (English)

    Ming Luo; Shengsheng Ma; Na Liang

    2014-01-01

    Purpose:.To observe the efficacy of toric design orthokera-tology.(ortho-k).for correcting myopia and astigmatism in my-opic adolescents with moderate to high astigmatism. Methods:.This was a self-controlled clinical study..Twenty-four subjects(42 eyes).aged 9 to 16 years with myopia of 2.50-6.00 D complicated with rule astigmatism of 1.50-3.50 D were fitted with Lucid Night Toric Ortho-k Lenses (LUCID,KO-REA)..The changes in uncorrected visual acuity (UCVA), spherical degree, refraction, axial length (AL),.and corneal status were assessed at baseline, 1 night, 1 week, 1 month, 3 months, 6 months, and 1 year after the commencement of or-tho-k lens wear. Results: The success rate of the first lens fit was 92.8%. The UCVA after ortho-k wearing was improved significantly com-pared to the baseline during each visit (all P0.05)..Grade 1 corneal staining was observed at 1 week (23.8%),.1 month (21.4%), and 1 year (16.7%) fol-lowing lens wear, and was improved by lens cleaning,.discon-tinuing lens wear, and moistening the cornea with eye drops. No severe adverse events were reported. Conclusion: The toric ortho-k lens was effective and safe for correction of low to moderate myopia in children with moder-ate to high astigmatism..The lens also effectively controlled axial length elongation during 1 year of observation..However, the long-term efficacy remains to be elucidated.

  11. Toric intraocular lenses for correction of astigmatism in keratoconus and after corneal surgery

    OpenAIRE

    Mol, Ilse

    2016-01-01

    Ilse EMA Mol,1,2 Bart TH Van Dooren1,2 1Department of Ophthalmology, Amphia Hospital, Breda, 2Department of Ophthalmology, Erasmus Medical Center, Rotterdam, the Netherlands Purpose: To describe the results of cataract extraction with toric intraocular lens (IOL) implantation in patients with preexisting astigmatism from three corneal conditions (keratoconus, postkeratoplasty, and postpterygium surgery).Methods: Cataract patients with topographically stable, fairly regular (although sometim...

  12. [Optimization of broad-band flat-field holographic concave grating without astigmatism].

    Science.gov (United States)

    Kong, Peng; Tang, Yu-guo; Bayanheshig; Li, Wen-hao; Cui, Jin-jiang

    2012-02-01

    The desirable imaging locations of the flat-field holographic concave gratings should be in a plane. And the object can be imaged perfectly by the grating when the tangential focal curve and sagittal focal curve both superpose the intersection of the image plane and dispersion plane. But actually, the defocus can not be eliminated over the entire wavelength range, while the astigmatism vanishes when the grating parameters satisfy some conditions. An optimization method for broad-band flat-field holographic concave gratings with absolute astigmatism correction was proposed. The ray tracing software ZEMAX was used for investigating the imaging properties of the grating. And we made a comparison between spectral performance of gratings designed by this new method and that by conventional method, respectively. The results indicated that the spectral performance of gratings designed by using the absolute astigmatism correction method can be as good as gratings designed with the conventional method. And the focusing performance in the sagittal direction is much better, so that the S/N ratio can be greatly improved.

  13. Toric Intraocular Lens Implantation for Correction of Astigmatism in Cataract Patients with Corneal Ectasia

    Directory of Open Access Journals (Sweden)

    Efstratios A. Parikakis

    2013-11-01

    Full Text Available Our purpose was to examine the long-term efficacy of toric intraocular lens (IOL implantation in cataract patients with high astigmatism due to corneal ectasia, who underwent phacoemulsification cataract surgery. Five eyes of 3 cataract patients with topographically stable keratoconus or pellucid macular degeneration (PMD, in which phacoemulsification with toric IOL implantation was used to correct high astigmatism, are reported. Objective and subjective refraction, visual acuity measurement and corneal topography were performed in all cases before and after cataract surgery. In all cases, there was a significant improvement in visual acuity, as well as refraction, which remained stable over time. Specifically, in subjective refraction, all patients achieved visual acuity from 7/10 to 9/10 with up to -2.50 cyl. Corneal topography also remained stable. Postoperative follow-up was 18-28 months. Cataract surgery with toric IOL implantation seems to be safe and effective in correcting astigmatism and improving visual function in cataract patients with topographically stable keratoconus or PMD.

  14. Customized toric intraocular lens implantation for correction of extreme corneal astigmatism due to corneal scarring

    Directory of Open Access Journals (Sweden)

    R Bassily

    2010-03-01

    Full Text Available R Bassily, J LuckOphthalmology Department, Royal United Hospital, Combe Park, Bath, UKAbstract: A 76-year-old woman presented with decreased visual function due to cataract formation. Twenty-five years prior she developed right sided corneal ulceration that left her with 10.8 diopters (D of irregular astigmatism at 71.8° (steep axis. Her uncorrected visual acuity was 6/24 and could only ever wear a balanced lens due to the high cylindrical error. Cataract surgery was planned with a custom designed toric intraocular lens (IOL with +16.0 D sphere inserted via a wound at the steep axis of corneal astigmatism. Postoperative refraction was -0.75/+1.50 × 177° with a visual acuity of 6/9 that has remained unchanged at six-week follow-up with no IOL rotation. This case demonstrates the value of high power toric IOLs for the correction of pathological corneal astigmatism.Keywords: intraocular lens, corneal ulceration, visual acuity, scarring

  15. Use of a Toric Intraocular Lens and a Limbal-Relaxing Incision for the Management of Astigmatism in Combined Glaucoma and Cataract Surgery

    Science.gov (United States)

    Gibbons, Allister

    2016-01-01

    Purpose We report the surgical management of a patient with glaucoma undergoing cataract surgery with high preexisting astigmatism. A combination of techniques was employed for her astigmatism management. Methods A 76-year-old female with 5.5 dpt of corneal astigmatism underwent surgery in her left eye consisting of one-site trabeculectomy, phacoemulsification, toric intraocular lens implantation and a single inferior limbal-relaxing incision. Results Intraocular pressure control was achieved with no medication at 11 mm Hg; before the filtering procedure, the pressure was 16 mm Hg on two topical drugs. Astigmatism was reduced to 0.75 dpt, and both corrected and uncorrected visual acuity improved. Conclusions Astigmatism management can have a good outcome in combined procedures. We encourage surgeons to address astigmatism in the preoperative planning of patients undergoing glaucoma surgery associated with phacoemulsification. PMID:27293408

  16. Assessment of corneal astigmatism following frown and straight incision forms in sutureless manual small incision cataract surgery

    Directory of Open Access Journals (Sweden)

    Amedo AO

    2016-04-01

    Full Text Available Angela Ofeibea Amedo, Kwadwo Amoah, Nana Yaa Koomson, David Ben Kumah, Eugene Appenteng Osae Department of Optometry and Visual Science, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana Abstract: To investigate which of two tunnel incision forms (frown versus straight in sutureless manual small incision cataract surgery creates more corneal astigmatism. Sixty eyes of 60 patients who had consented to undergo cataract surgery and to partake in this study were followed from baseline through >12-week postoperative period. Values of preoperative and postoperative corneal astigmatism for the 60 eyes, measured with a Bausch and Lomb keratometer, were extracted from the patients’ cataract surgery records. Residual astigmatism was computed as the difference between preoperative and postoperative keratometry readings. Visual acuity was assessed during the preoperative period and at each postoperative visit with a Snellen chart at 6 m. Fifty eyes of 50 patients were successfully followed-up on. Overall, the mean residual astigmatism was 0.75±0.12 diopters. The differences in mean residual astigmatism between the two different incision groups were statistically significant (t [48]=6.33, P<0.05; frown incision group recorded 1.00±0.12 diopters, whereas the straight incision group recorded 0.50±0.12 diopters. No significant difference was observed between male and female groups (t [48]=0.24, P>0.05. Residual corneal astigmatism in the frown incision group was significantly higher than in the straight incision group. Fisher’s exact test did not reveal a significant association between incision forms and visual acuity during the entire postoperative period (P>0.05. Keywords: cataract, residual corneal astigmatism, frown incision, straight incision

  17. A Michelson controlled-not gate with a single-lens astigmatic mode converter.

    Science.gov (United States)

    Souza, C E R; Khoury, A Z

    2010-04-26

    We propose and demonstrate experimentally a single lens design for an astigmatic mode converter that transforms the transverse mode of paraxial optical beams. As an application, we implement a controlled-not gate based on a Michelson interferometer in which the photon polarization is the control bit and the first order transverse mode is the target. As a further application, we also build a transverse mode parity sorter which can be useful for quantum information processing as a measurement device for the transverse mode qubit. PMID:20588767

  18. The construction of sutureless cataract incision and the management of corneal astigmatism.

    Science.gov (United States)

    Hall, G W; Krischer, C; Mobasher, B; Rajan, S D

    1993-02-01

    Extrapolating information from equations that govern fluid flow, a theoretical formula is developed for a sutureless cataract incision. This theoretical formula defines the resistance of aqueous outflow as a function of three variables: length of cataract incision, the length of the scleral tunnel, the tortuosity of the outflow channel, and one constant friction factor. The nonlinear relationship of corneal incisions to length, depth, and distance from the visual axis is also examined with respect to their effect on central corneal curvature and control of astigmatism. Finite element analysis of differential equations is discussed as the most plausible technique for predicting these incisional effects.

  19. SURGICALLY INDUCED ASTIGMATISM AFTER IMPLANTATION OF FOLDABLE AND NON - FOLDABLE LENSES IN CATARACT SURGERY BY PHACOEMULSIFICATION

    Directory of Open Access Journals (Sweden)

    Vikas

    2015-01-01

    Full Text Available This prospective comparative study included 300 matched patients of different grades of senile cataract. All of them willfully underwent phacoemulsification at the hands of a single experienced surgeon, performing with a single and individual technique {Woodcutter’s technique 1 }; half of them were implanted with a foldable intraocular lens and the other half with a non - foldable PMMA intraocular lens. All the patients undergoing phacoemulsification had an improvement in vision. There was no statistically significant difference in the surgically induced astigmatism after implanting foldable or non - foldable IOL

  20. Optimization of nonimaging focusing heliostat in dynamic correction of astigmatism for a wide range of incident angles.

    Science.gov (United States)

    Chong, Kok-Keong

    2010-05-15

    To overcome astigmatism has always been a great challenge in designing a heliostat capable of focusing the sunlight on a small receiver throughout the year. In this Letter, a nonimaging focusing heliostat with a dynamic adjustment of facet mirrors in a group manner has been analyzed for optimizing the astigmatic correction in a wide range of incident angles. This what is to the author's knowledge a new heliostat is not only designed to serve the purpose of concentrating sunlight to several hundreds of suns, but also to significantly reduce the variation of the solar flux distribution with the incident angle.

  1. FASTDEF: fast defocus and astigmatism estimation for high-throughput transmission electron microscopy.

    Science.gov (United States)

    Vargas, J; Otón, J; Marabini, R; Jonic, S; de la Rosa-Trevín, J M; Carazo, J M; Sorzano, C O S

    2013-02-01

    In this work we present a fast and automated algorithm for estimating the contrast transfer function (CTF) of a transmission electron microscope. The approach is very suitable for High Throughput work because: (a) it does not require any initial defocus estimation, (b) it is almost an order of magnitude faster than existing approaches, (c) it opens the way to well-defined extensions to the estimation of higher order aberrations, at the same time that provides defocus and astigmatism estimations comparable in accuracy to well established methods, such as Xmipp and CTFFIND3 approaches. The new algorithm is based on obtaining the wrapped modulating phase of the power spectra density pattern by the use of a quadrature filter. This phase is further unwrapped in order to obtain the continuous and smooth absolute phase map; then a Zernike polynomial fitting is performed and the defocus and astigmatism parameters are determined. While the method does not require an initial estimation of the defocus parameters or any non-linear optimization procedure, these approaches can be used if further refinement is desired. Results of the CTF estimation method are presented for standard negative stained images, cryo-electron microscopy images in the absence of carbon support, as well as micrographs with only ice. Additionally, we have also tested the proposed method with micrographs acquired from tilted and untilted samples, obtaining good results. The algorithm is freely available as a part of the Xmipp package [http://xmipp.cnb.csic.es].

  2. Astigmatism management in cataract surgery with Precizon® toric intraocular lens: a prospective study

    Science.gov (United States)

    Vale, Carolina; Menezes, Carlos; Firmino-Machado, J; Rodrigues, Pedro; Lume, Miguel; Tenedório, Paula; Menéres, Pedro; Brochado, Maria do Céu

    2016-01-01

    Purpose The purpose of this study was to evaluate the visual and refractive outcomes and rotational stability of the new aspheric Precizon® toric intraocular lens (IOL) for the correction of corneal astigmatism in cataract surgery. Setting Department of Ophthalmology, Hospital Geral de Santo António – Centro Hospitalar do Porto, EPE and Hospital de Pedro Hispano, Matosinhos, Portugal. Design This was a prospective clinical study. Patients and methods A total of 40 eyes of 27 patients with corneal astigmatism greater than 1.0 diopter (D) underwent cataract surgery with implantation of Precizon® toric IOL. IOL power calculation was performed using optical coherence biometry (IOLMaster®). Outcomes of uncorrected (UDVA) and best-spectacle corrected distance visual acuities (BCDVA), refraction, and IOL rotation were analyzed at the 1st week, 1st, 3rd, and 6th month’s evaluations. Results The median postoperative UDVA was better than preoperative best-spectacle corrected distance visual acuity (0.02 [0.06] logMAR vs 0.19 [0.20] logMAR, P<0.001). At 6 months, postoperative UDVA was 0.1 logMAR or better in 95% of the eyes. At last follow-up, the mean spherical equivalent was reduced from −3.35±3.10 D to −0.02±0.30 D (P<0.001) with 97.5% of the eyes within ±0.50 D of emmetropia. The mean preoperative keratometric cylinder was 2.34±0.95 D and the mean postoperative refractive cylinder was 0.24±0.27 D (P<0.001). The mean IOL rotation was 2.43°±1.55°. None of the IOLs required realignment. Conclusion Precizon® toric IOL revealed very good rotational stability and performance regarding predictability, efficacy, and safety in the correction of preexisting regular corneal astigmatism associated with cataract surgery. PMID:26855559

  3. Visual performance in cataract patients with low levels of postoperative astigmatism: full correction versus spherical equivalent correction

    Directory of Open Access Journals (Sweden)

    Lehmann RP

    2012-03-01

    Full Text Available Robert P Lehmann1, Diane M Houtman21Lehmann Eye Center, Nacogdoches, TX, 2Alcon Research Ltd, Fort Worth, TX, USAPurpose: To evaluate whether visual performance could be improved in pseudophakic subjects by correcting low levels of postoperative astigmatism.Methods: An exploratory, noninterventional study was conducted using subjects who had been implanted with an aspheric intraocular lens and had 0.5–0.75 diopter postoperative astigmatism. Monocular visual performance using full correction was compared with visual performance using spherical equivalent correction. Testing consisted of high- and low-contrast visual acuity, contrast sensitivity, and reading acuity and speed using the Radner Reading Charts.Results: Thirty-eight of 40 subjects completed testing. Visual acuities at three contrast levels (100%, 25%, and 9% were significantly better using full correction than when using spherical equivalent correction (all P < 0.001. For contrast sensitivity testing under photopic, mesopic, and mesopic with glare conditions, only one out of twelve outcomes demonstrated a significant improvement with full correction compared with spherical equivalent correction (at six cycles per degree under mesopic without glare conditions, P = 0.046. Mean reading speed was numerically faster with full correction across all print sizes, reaching statistical significance at logarithm of the reading acuity determination (logRAD 0.2, 0.7, and 1.1 (P , 0.05. Statistically significant differences also favored full correction in logRAD score (P = 0.0376, corrected maximum reading speed (P < 0.001, and logarithm of the minimum angle of resolution/logRAD ratio (P < 0.001.Conclusions: In this study of pseudophakic subjects with low levels of postoperative astigmatism, full correction yielded significantly better reading performance and high- and low-contrast visual acuity than spherical equivalent correction, suggesting that cataractous patients may benefit from surgical

  4. [Orthokeratology for the high myopia and high astigmatism is worth watching].

    Science.gov (United States)

    Xie, Peiying

    2015-01-01

    The prevalence of high myopia in teenagers is rising. Due to both genetic factors and environmental factors, most of myopia occurs in early age with rapid progress, and the prevention and control are very difficult. Orthokeratology is considered as one of the most effective ways of controlling myopia for children. It is proved effective through many years of clinical studies not only for low to moderate myopia, but also for high myopia with astigmatism. However, professional knowledge is lacking domestically. This paper introduces the local and overseas research results in recent years, and discusses the necessity and feasibility of high diopter orthokeratology correction, implementation methods and requirements, and safety and effectiveness evaluation standards for reference. PMID:25877704

  5. Relaxation in Thin Polymer Films Mapped across the Film Thickness by Astigmatic Single-Molecule Imaging

    KAUST Repository

    Oba, Tatsuya

    2012-06-19

    We have studied relaxation processes in thin supported films of poly(methyl acrylate) at the temperature corresponding to 13 K above the glass transition by monitoring the reorientation of single perylenediimide molecules doped into the films. The axial position of the dye molecules across the thickness of the film was determined with a resolution of 12 nm by analyzing astigmatic fluorescence images. The average relaxation times of the rotating molecules do not depend on the overall thickness of the film between 20 and 110 nm. The relaxation times also do not show any dependence on the axial position within the films for the film thickness between 70 and 110 nm. In addition to the rotating molecules we observed a fraction of spatially diffusing molecules and completely immobile molecules. These molecules indicate the presence of thin (<5 nm) high-mobility surface layer and low-mobility layer at the interface with the substrate. (Figure presented) © 2012 American Chemical Society.

  6. Extended wavelet transformation to digital holographic reconstruction: application to the elliptical, astigmatic Gaussian beams.

    Science.gov (United States)

    Remacha, Clément; Coëtmellec, Sébastien; Brunel, Marc; Lebrun, Denis

    2013-02-01

    Wavelet analysis provides an efficient tool in numerous signal processing problems and has been implemented in optical processing techniques, such as in-line holography. This paper proposes an improvement of this tool for the case of an elliptical, astigmatic Gaussian (AEG) beam. We show that this mathematical operator allows reconstructing an image of a spherical particle without compression of the reconstructed image, which increases the accuracy of the 3D location of particles and of their size measurement. To validate the performance of this operator we have studied the diffraction pattern produced by a particle illuminated by an AEG beam. This study used mutual intensity propagation, and the particle is defined as a chirped Gaussian sum. The proposed technique was applied and the experimental results are presented.

  7. Focal plane internal energy flows of singular beams in astigmatically aberrated low numerical aperture systems.

    Science.gov (United States)

    Bahl, Monika; Senthilkumaran, P

    2014-09-01

    Singular beams have circulating energy components. When such beams are focused by low numerical aperture systems suffering from astigmatic aberration, these circulating energy components get modified. The phase gradient introduced by this type of aberration splits the higher charge vortices. The dependence of the charge, the aberration coefficient, and the size of the aperture on the nature of the splitting process are reported in this paper. The transverse components of the Poynting vector fields that can be derived from the phase gradient vector field distributions are further decomposed into solenoidal and irrotational components using the Helmholtz-Hodge decomposition method. The solenoidal components relate to the orbital angular momentum of the beams, and the irrotational components are useful in the transport of intensity equations for phase retrieval.

  8. Analysis of familial aggregation in total, against-the-rule, with-the-rule, and oblique astigmatism by conditional and marginal models in the Tehran eye study

    Directory of Open Access Journals (Sweden)

    Mohammad H Rakhshani

    2012-01-01

    Full Text Available Purpose: The purpose was to determine the familial aggregation of the total, against-the-rule (ATR, with-the-rule (WTR, and oblique astigmatism by conditional and marginal models in the Tehran Eye Study. Materials and Methods: Total, ATR, WTR, and oblique astigmatism were studied in 3806 participants older than 5 years from August 2002 to December 2002 in the Tehran Eye Study. Astigmatism was defined as a cylinder worse than or equal to −0.5 D. WTR astigmatism was defined as 0 ± 19°, ATR astigmatism was defined as 90 ± 19°, and oblique when the axes were 20-70° and 110-160°. The familial aggregation was investigated with a conditional model (quadratic exponential and marginal model (alternating logistic regression after controlling for confounders. Results: Using the conditional model, the conditional familial aggregation odds ratios (OR (95% confidence interval for the total, WTR, ATRs, and oblique astigmatism were 1.49 (1.43-1.72, 1.91 (1.65-2.20, 2.00 (1.70-2.30, and 1.86 (1.37-2.54, respectively. In the marginal model, the marginal OR of the parent-offspring and sib-sib in the total astigmatism were 1.35 (1.13-1.63 and 1.54 (1.13-2.11, respectively; WTR 1.53 (1.06-2.20 and 1.94 (1.21-3.13 and; ATR 2.13 (1.01-4.50 and 2.23 (1.52-3.30. The model was statistically significant in sib-sib relationship only for oblique astigmatism with OR of 3.00 (1.25-7.20. Conclusion: The results indicate familial aggregation of astigmatism in the population in Tehran adjusted for age, gender, cataract, duration of education, and body mass index, so that the addition of a new family member affected with astigmatism, as well as having a sibling or parents with astigmatism, significantly increases the odds of exposure to the disease for all four phenotypes. This aggregation can be due to genetic and/or environmental factors. Dividing astigmatism into three phenotypes increased the odds ratios.

  9. Orbital angular moment of a partially coherent beam propagating through an astigmatic ABCD optical system with loss or gain.

    Science.gov (United States)

    Cai, Yangjian; Zhu, Shijun

    2014-04-01

    We derive the general expression for the orbital angular momentum (OAM) flux of an astigmatic partially coherent beam carrying twist phase [i.e., twisted anisotropic Gaussian-Schell model (TAGSM) beam] propagating through an astigmatic ABCD optical system with loss or gain. The evolution properties of the OAM flux of a TAGSM beam in a Gaussian cavity or propagating through a cylindrical thin lens are illustrated numerically with the help of the derived formula. It is found that we can modulate the OAM of a partially coherent beam by varying the parameters of the cavity or the orientation angle of the cylindrical thin lens, which will be useful in some applications, such as free-space optical communications and particle trapping.

  10. Toric Intraocular Lens vs. Peripheral Corneal Relaxing Inci-sions to Correct Astigmatism in Eyes Undergoing Cataract Surgery

    Institute of Scientific and Technical Information of China (English)

    Zhiping Liu; Xiangyin Sha; Xuanwei Liang; Zhonghao Wang; Jingbo Liu; Danping Huang

    2014-01-01

    Purpose:.To compare toric intraocular lens implantation (Toric-IOL).with peripheral corneal relaxing incisions (PCRIs) for astigmatism correction in patients undergoing cataract surgery. Methods: 54 patients (54 eyes) with more than 0.75 diopter (D).of preexisting corneal astigmatism were classified as group A (0.75-1.50D) or group B (1.75-2.50D). The patients were randomized to undergo Toric-IOL or PCRIs in the steep axis with spherical IOL implantation..LogMAR uncorrected visual acuity (LogMAR UCVA), LogMAR best corrected vi sual acuity.(LogMAR BCVA),.error of vector (|EV|), surgery induced refraction correction. (|SIRC|),.and correction rates (CR) were measured 1 month and 6 months postoperatively. Results: At 6 months postoperatively, all 54 eyes had Log-MAR BCVA≤0.2. Patients who underwent PCRIs and Toric-IOL with LogMAR BCVA≤0.1 showed no significant differ-ences in group A (P=1.00) or in group B (P=0.59). Group A showed no significant differences in LogMAR UCVA (P=0.70), |EV| (P=0.13), |SIRC| (P=0.71), and CR (P=0.56) in patients underwent PCRIs and Toric-IOL. However, group B showed significant differences in LogMAR UCVA (P Conclusion:.The efficacy and stability of Toric-IOL and PCRIs were equal in low astigmatic patients..Toric-IOL achieved an enhanced effect over PCRIs in higher astigmatic patients. PCRIs had the more refractive regression than Toric-IOL in 6 months.

  11. Surgically induced astigmatism after 3.0 mm temporal and nasal clear corneal incisions in bilateral cataract surgery

    Directory of Open Access Journals (Sweden)

    Je Hwan Yoon

    2013-01-01

    Full Text Available Aims: To compare the corneal refractive changes induced after 3.0 mm temporal and nasal corneal incisions in bilateral cataract surgery. Materials and Methods: This prospective study comprised a consecutive case series of 60 eyes from 30 patients with bilateral phacoemulsification that were implanted with a 6.0 mm foldable intraocular lens through a 3.0 mm horizontal clear corneal incision (temporal in the right eyes, nasal in the left eyes. The outcome measures were surgically induced astigmatism (SIA and uncorrected visual acuity (UCVA 1 and 3 months, post-operatively. Results: At 1 month, the mean SIA was 0.81 diopter (D for the temporal incisions and 0.92 D for nasal incisions (P = 0.139. At 3 months, the mean SIA were 0.53 D for temporal incisions and 0.62 D for nasal incisions (P = 0.309. The UCVA was similar in the 2 incision groups before surgery, and at 1 and 3 months post-operatively. Conclusion: After bilateral cataract surgery using 3.0 mm temporal and nasal horizontal corneal incisions, the induced corneal astigmatic change was similar in both incision groups. Especially in Asian eyes, both temporal and nasal incisions (3.0 mm or less would be favorable for astigmatism-neutral cataract surgery.

  12. Comparison of surgically induced astigmatism in patients with horizontal rectus muscle recession

    Institute of Scientific and Technical Information of China (English)

    Harun; akmak; Tolga; Kocatürk; Sema; Oru; Dündar

    2014-01-01

    ·AIM: To compare surgically induced astigmatism(SIA)following horizontal rectus muscle recession surgery between suspension recession with both the "hang-back" technique and conventional recession technique.·METHODS: Totally, 48 eyes of 24 patients who had undergone horizontal rectus muscle recession surgery were reviewed retrospectively. The patients were divided into two groups. Twelve patients were operated on by the hang-back technique(Group 1), and 12 by the conventional recession technique(Group 2). SIA was calculated on the 1stwk, 1stand in the 3rdmo after surgery using the SIA calculator.·RESULTS: SIA was statistically higher in the Group 1all postoperative follow-up. SIA was the highest in the 1st wk, and decreased gradually in both groups.·CONCLUSION: The suspension recession technique induced much more SIA than the conventional recession technique. This difference also continued in the following visits. Therefore, the refractive power should be checked postoperatively in order to avoid refractive amblyopia.Conventional recession surgery should be the preferred method so as to minimize the postoperative refractive changes in patients with amblyopia.

  13. Mild myopic astigmatism corrected by accidental flap complication: A case report

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    Fahed Daoud

    2009-01-01

    Full Text Available A 35-year-old female presented for laser in-situ keratomileusis (LASIK. Her preoperative eye exam was normal, with a preop refraction of OD -2.50 D Sph +1.25 D Cyl Χ175 and OS -2.75 D Sph +1.50 D Cyl Χ165 (cycloplegic and manifest, with 20/20 BCVA OU. The central pachymetry reading was 553 ΅m in the right eye. Preoperative topography was normal. At the start of the pendular microkeratome path, some resistance was felt, but the microkeratome continued along its path. Upon inspection of the flap, there was a central rectangle of intact epithelium with two mirror-image flaps on both sides. The flap was repositioned and LASIK was discontinued. The cornea healed with two faint thin linear vertical parallel scars at the edge of the pupil. Postoperative inspection of the blade revealed central blunting. One month postoperatively, the uncorrected visual acuity (UCVA was 20/20. Manifest and cycloplegic refractions were plano. This is an interesting case of accidental flap complication resulting in the correction of mild myopic astigmatism.

  14. Correção do astigmatismo na cirurgia da catarata Surgical correction of astigmatism during cataract surgery

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    Edison Ferreira e Silva

    2007-08-01

    Full Text Available OBJETIVOS: Avaliar a eficácia das incisões periféricas relaxantes limbares (IPRL na redução do astigmatismo pré-operatório durante a cirurgia de catarata. MÉTODOS: Foram estudados prospectivamente 103 olhos de 103 pacientes submetidos as IPRL, utilizando o nomograna de Nichamin durante a cirurgia de catarata pela facoemulsificação. Após o 1º e 6º mês foram avaliadas as mudanças no astigmatismo topográfico, na indução do astigmatismo e no índice de sucesso. Os pacientes foram separados em dois grupos segundo o tipo de astigmatismo no pré-operatório (a favor da regra e contra a regra e estudados separadamente. RESULTADOS: Ocorreram diferenças estatisticamente significativas entre os valores dos astigmatismos topográficos no pré e pós-operatório nos dois grupos. Verificou-se indução de 1,10 ± 0,9 dioptrias e 37% de índice de sucesso no grupo de astigmatismo a favor da regra e 1,70 ± 0,80 dioptrias e 51% de índice de sucesso no grupo de astigmatismo contra a regra após o 6º mês de seguimento. CONCLUSÃO: A incisão periférica relaxante limbar é efetiva na redução do astigmatismo pré-existente durante a cirurgia da catarata. O procedimento mostrou ser seguro e de fácil realização. O nomograma de Nichamim na nossa experiência hipocorrige o astigmatismo planejado em ambos os grupos estudados.PURPOSE: To evaluate the effect of peripheral limbar relaxing incisions (PLRI in the reduction of the astigmatism during cataract surgery. METHODS: We studied prospectively 103 eyes of 103 patients submitted to PLRI, using the Nichamim nomogram during cataract surgery by phacoemulsification. After the first and sixth month we analized the changes in astigmatism topography, induction of astigmatism and sucess rate. The patients were divided into two groups according to the astigmatism (with-the-rule and against-the-rule, and studied separately. RESULTS: There was a statistically significant change in the mean astigmatism

  15. Clinical analysis of myopia astigmatism of children aged 6-15%6-15岁儿童近视性散光的临床分析

    Institute of Scientific and Technical Information of China (English)

    段思琦; 李静姣; 钟华; 周华; 田琨; 魏嘉

    2015-01-01

    Objective To study the occurrence of astigmatism,astigmatism type,astigmatism power and astig-matism axis distrubution among 6-15 years old children,and analyzes its rule.Methods From 2012 to the first half of the 2014, 710 cases of 6-15 years old children with glasses admitted in the Ophtalmic Outpatient Clinic were enrolled in this study.In which the clinical data of 483 cases (749 eyes) with myopia astigmatism were statistically analyzed. Results Myopia astigmatism were 483 cases (749 eyes) and the detection rate was 68.03%. There were 247 cases of male and 236 cases of female,accounted for 51.14% and 48.86%. Astigmatism type has no significant difference in the age group (Χ2=3.418, P>0.05). In AWR, the 6-12 age group was 221 cases (63.14%), the 13-15 age group was 129 cases (36.86%). Astigmatism type has a significant difference in the myopic astigmatism power group (Χ2=28.878, P0.05).在顺规散光中6-12岁年龄组221例(63.14%),13-15岁年龄组129例(36.86%).各散光类型在不同近视性散光度组的发病率有明显统计学差异(Χ2=28.878, P<0.001);轻度散光组中,顺规散光315例(66.60%),逆规散光99例(20.93%),斜向散光59例(12.47%).顺规散光在轻度散光组315例(57.48%),中度散光组160例(29.20%),高度散光组73例(13.32%).各散光类型在不同屈光状态组的发病率有统计学差异(Χ2=612.598,P <0.05).顺规散光在复合近视散光组303例(86.57%),单纯近视散光组47例(13.43%).结论 近视性散光在6-15岁儿童中普遍存在,双眼较单眼发病率高,低度散光占大多数,复合近视散光较单纯近视散光更为常见.

  16. Transmissive liquid-crystal device correcting primary coma aberration and astigmatism in laser scanning microscopy

    Science.gov (United States)

    Tanabe, Ayano; Hibi, Terumasa; Ipponjima, Sari; Matsumoto, Kenji; Yokoyama, Masafumi; Kurihara, Makoto; Hashimoto, Nobuyuki; Nemoto, Tomomi

    2016-03-01

    Laser scanning microscopy allows 3D cross-sectional imaging inside biospecimens. However, certain aberrations produced can degrade the quality of the resulting images. We previously reported a transmissive liquid-crystal device that could compensate for the predominant spherical aberrations during the observations, particularly in deep regions of the samples. The device, inserted between the objective lens and the microscope revolver, improved the image quality of fixed-mouse-brain slices that were observed using two-photon excitation laser scanning microscopy, which was originally degraded by spherical aberration. In this study, we developed a transmissive device that corrects primary coma aberration and astigmatism, motivated by the fact that these asymmetric aberrations can also often considerably deteriorate image quality, even near the sample surface. The device's performance was evaluated by observing fluorescent beads using single-photon excitation laser scanning microscopy. The fluorescence intensity in the image of the bead under a cover slip tilted in the y-direction was increased by 1.5 times after correction by the device. Furthermore, the y- and z-widths of the imaged bead were reduced to 66% and 65%, respectively. On the other hand, for the imaged bead sucked into a glass capillary in the longitudinal x-direction, correction with the device increased the fluorescence intensity by 2.2 times compared to that of the aberrated image. In addition, the x-, y-, and z-widths of the bead image were reduced to 75%, 53%, and 40%, respectively. Our device successfully corrected several asymmetric aberrations to improve the fluorescent signal and spatial resolution, and might be useful for observing various biospecimens.

  17. Intraocular lens implantation for the treatment of astigmatism%人工晶状体植入术矫正散光

    Institute of Scientific and Technical Information of China (English)

    施俊廷; 徐雯

    2013-01-01

    Refractive intraocular lens surgery can be used for the treatment of moderate and high regular astigmatism.Refractive intraocular lens surgery includes aphakic intraocular lens surgery and phakic intraocular lens surgery.In phakic intraocular lens surgery two types of intraocular lenses are used:iris-claw intraocular lens and posterior chamber intraocular lens.The purpose of this article is to review current knowledge of surgical treatments of astigmatism with a particular focus on toric implantable collamer lenses.%人工晶状体(IOL)植入术能矫正中、高度规则散光.矫正散光的IOL植入术可分为无晶状体眼及有晶状体眼的环曲面IOL植入两类,其中有晶状体眼的环曲面IOL又可分为虹膜夹持型及后房型.本文旨在介绍IOL矫正散光的手术治疗方法,并着重介绍有晶状体眼植入后房型IOL矫正屈光不正合并散光的治疗技术.

  18. SURGICALLY INDUCED ASTIGMATISM AFTER 2.8 MM TEMPORAL AND NASAL CLEAR CORNEAL INCISIONS IN PHACOEMULSIFICATION CATARACT SURGERY OF SAME PATIENT

    Directory of Open Access Journals (Sweden)

    Preeti

    2015-04-01

    Full Text Available PURPOSE: To evaluate and compare the surgically induced astigmatism in phacoemulsification cataract surgery after 2.8 mm temporal and nasal clear corneal incision of same patient . MATERIAL AND METHOD : This prospective study comprised a consecutive case series of 60 eyes. Eyes from 30 patients with phacoemulsification those were implanted with a 6.00 mm foldable intraocular le ns through a 2.8 mm horizontal clear corneal incision (temporal in the right eye , nasal in the left eye. RESULTS : T he outcome measures were surgically induced astigmatism (SIA and uncorrected visual acuity (UCVA , at 1 and 3 months post - operatively. A 1 month the mean SIA was 0.81 D. for the temporal incision and 0.92 D for nasal incision (P = 0.139 at 3 months the mean SIA was 0.53 D for temporal incision and 0.62 D for nasal incision (P =0.309. The pre - operative parameters i.e. (UCVA , mean keratomet ry & keratometric cylinder between these groups were comparable. There was no statistically significant difference found between three groups pre - operatively . CONCLUSION : After cataract surgery using 2.8mm temporal and nasal horizontal corneal incision , t he induced corneal astigmatic changes was similar in both incision groups. Especially in Asian eyes , both temporal and nasal incisions (2.8 mm or less would be equally favourable for astigmatism neutral cataract surgery

  19. Surgical induced astigmatism correlated with corneal pachymetry and intraocular pressure: transconjunctival sutureless 23-gauge versus 20-gauge sutured vitrectomy in diabetes mellitus

    Institute of Scientific and Technical Information of China (English)

    Yan; Shao; Li-Jie; Dong; Yan; Zhang; Hui; Liu; Bo-Jie; Hu; Ju-Ping; Liu; Xiao-Rong; Li

    2015-01-01

    AIM: To determine the difference of surgical induced astigmatism between conventional 20-gauge sutured vitrectomy and 23-gauge transconjunctival sutureless vitrectomy, and the influence of corneal pachymetry and intraocular pressure(IOP) on surgical induced astigmatism in diabetic patients.METHODS: This retrospective, consecutive case series consisted of 40 eyes of 38 diabetic subjects who underwent either 20-gauge or 23-gauge vitrectomy. The corneal curvature and thickness were measured with Scheimpflug imaging before surgery and 1wk; 1, 3mo after surgery. We compared the surgical induced astigmatism(SIA) on the true net power in 23-gauge group with that in 20-gauge group. We determined the correlation between corneal thickness change ratio, IOP and SIA measured by Pentacam. RESULTS: The mean SIAs were 1.082 ±0.085 D( mean ± SEM), 0.689 ±0.070 D and 0.459 ±0.063 D at postoperative 1wk; 1, 3mo respectively in diabetic subjects. The vitrectomy induced astigmatisms were declined significantly with time(F2,36=33.629, P =0.000)postoperatively. The 23-gauge surgery group induced significantly less astigmatism than 20-gauge surgery group(F1,37=11.046, P =0.020). Corneal thickness in diabetes elevated after surgery(F3,78=10.532, P =0.000).The linear regression analysis at postoperatively 1wk went as: SIA =-4.519 +4.931 change ratio(Port3) +0.026IOP(R2=0.46, P =0.000), whereas the rate of cornealthickness change and IOP showed no correlation with the change of astigmatism at postoperatively 1 and 3mo.CONCLUSION: There are significant serial changes in both 20-gauge and 23-gauge group in diabetic subjects.23-gauge induce less astigmatism than 20-gauge and become stable more rapidly than 20-gauge. The elevation of corneal thickness and IOP was associated with increased astigmatim at the early postoperative stage both in 23-gauge and 20-gauge surgery group.

  20. Methods for calculating the vergence of an astigmatic ray bundle in an optical system that contains a freeform surface

    Science.gov (United States)

    Shirayanagi, Moriyasu

    2016-07-01

    A method using the generalized Coddington equations enables calculating the vergence of an astigmatic ray bundle in the vicinity of a skew ray in an optical system containing a freeform surface. Because this method requires time-consuming calculations, however, there is still room for increasing the calculation speed. In addition, this method cannot be applied to optical systems containing a medium with a gradient index. Therefore, we propose two new calculation methods in this paper. The first method, using differential ray tracing, enables us to shorten computation time by using simpler algorithms than those used by conventional methods. The second method, using proximate rays, employs only the ray data obtained from the rays exiting an optical system. Therefore, this method can be applied to an optical system that contains a medium with a gradient index. We show some sample applications of these methods in the field of ophthalmic optics.

  1. Successful toric intraocular lens implantation in a patient with induced cataract and astigmatism after posterior chamber toric phakic intraocular lens implantation: a case report

    Directory of Open Access Journals (Sweden)

    Kamiya Kazutaka

    2012-04-01

    Full Text Available Abstract Introduction We report the case of a patient in whom simultaneous toric phakic intraocular lens removal and phacoemulsification with toric intraocular lens implantation were beneficial for reducing pre-existing astigmatism and acquiring good visual outcomes in eyes with implantable collamer lens-induced cataract and astigmatism. Case presentation A 53-year-old woman had undergone toric implantable collamer lens implantation three years earlier. After informed consent was obtained, we performed simultaneous toric implantable collamer lens removal and phacoemulsification with toric intraocular lens implantation. Preoperatively, the manifest refraction was 0, -0.5 × 15, with an uncorrected visual acuity of 0.7 and a best spectacle-corrected visual acuity of 0.8. Postoperatively, the manifest refraction was improved to 0, -0.5 × 180, with an uncorrected visual acuity of 1.2 and a best spectacle-corrected visual acuity of 1.5. No vision-threatening complications were observed. Conclusion Toric intraocular lens implantation may be a good surgical option for the correction of spherical and cylindrical errors in eyes with implantable collamer lens-induced cataract and astigmatism.

  2. Surgically induced astigmatism after phacoemulsification with and without correction for posture-related ocular cyclotorsion: randomized controlled study.

    LENUS (Irish Health Repository)

    Dooley, Ian

    2012-02-01

    PURPOSE: To report the impact of posture-related ocular cyclotorsion on one surgeon\\'s surgically induced astigmatism (SIA) results and the variance in SIA. SETTING: Institute of Eye Surgery, Whitfield Clinic, Waterford, Ireland. METHODS: This prospective randomized controlled study included eyes that had phacoemulsification with intraocular lens implantation. Eyes were randomly assigned to have (intervention group) or not have (control group) correction for posture-related ocular cyclotorsion. In the intervention group, the clear corneal incision was placed precisely at the 120-degree meridian with instruments designed to correct posture-related ocular cyclotorsion. In the control group, the surgeon endeavored to place the incision at the 120-degree meridian, but without markings. RESULTS: The intervention group comprised 41 eyes and the control group, 61 eyes. The mean absolute SIA was 0.74 diopters (D) in the intervention group and 0.78 D in the control group; the difference between groups was not statistically significant (P>.5, unpaired 2-tailed Student t test). The variance in SIA was 0.29 D(2) and 0.31 D(2), respectively; the difference between groups was not statistically significant (P>.5, unpaired F test). CONCLUSIONS: Attempts to correct for posture-related ocular cyclotorsion did not influence SIA or its variance in a single-surgeon series. These results should be interpreted with full appreciation of the limitations of currently available techniques to correct for posture-related ocular cyclotorsion in the clinical setting.

  3. Topography-guided hyperopic and hyperopic astigmatism femtosecond laser-assisted LASIK: long-term experience with the 400 Hz eye-Q excimer platform

    Directory of Open Access Journals (Sweden)

    Kanellopoulos AJ

    2012-06-01

    Full Text Available Anastasios John KanellopoulosDepartment of Ophthalmology, New York University Medical School, New York, NY, and LaserVision.gr Eye Institute, Athens, GreeceBackground: The purpose of this study was to evaluate the safety and efficacy of topography-guided ablation using the WaveLight 400 Hz excimer laser in laser-assisted in situ keratomileusis (LASIK for hyperopia and/or hyperopic astigmatism.Methods: We prospectively evaluated 208 consecutive LASIK cases for hyperopia with or without astigmatism using the topography-guided platform of the 400 Hz Eye-Q excimer system. The mean preoperative sphere value was +3.04 ± 1.75 (range 0.75–7.25 diopters (D and the mean cylinder value was –1.24 ± 1.41 (–4.75–0 D. Flaps were created either with Intralase FS60 (AMO, Irvine, CA or FS200 (Alcon, Fort Worth, TX femtosecond lasers. Parameters evaluated included age, preoperative and postoperative refractive error, uncorrected distance visual acuity, corrected distance visual acuity, flap diameter and thickness, topographic changes, higher order aberration changes, and low contrast sensitivity. These measurements were repeated postoperatively at regular intervals for at least 24 months.Results: Two hundred and two eyes were available for follow-up at 24 months. Uncorrected distance visual acuity improved from 5.5/10 to 9.2/10. At 24 (8–37 months, 75.5% of the eyes were in the ±0.50 D range and 94.4% were in the ±1.00 D range of the refractive goal. Postoperatively, the mean sphere value was –0.39 ± 0.3 and the cylinder value was –0.35 ± 0.25. Topographic evidence showed that ablation was made in the visual axis and not in the center of the cornea, thus correlating with the angle kappa. No significant complications were encountered in this small group of patients.Conclusion: Hyperopic LASIK utilizing the topography-guided platform of the 400 Hz Eye-Q Allegretto excimer and a femtosecond laser flap appears to be safe and effective for

  4. Comparison of curative effects of visual perceptual learning and traditional treatment for the children under 8 years with astigmatism amblyopia with rule and astigmatism amblyopia against rule%8岁以下顺、逆规散光性弱视儿童视感知疗法与传统疗法疗效比较

    Institute of Scientific and Technical Information of China (English)

    孔旻; 刘伟民; 林泉; 赵武校

    2011-01-01

    目的:比较8岁以下患儿视感知学习疗法(perceptual learning)与传统疗法治疗顺、逆规散光性弱视的疗效.方法:将252例(504眼)8岁以下顺、逆规散光性弱视患儿,分别行视感知学习(154例,308眼)和传统疗法(98例,196眼)治疗,2年后对结果进行统计学分析.结果:8岁以下的顺、逆规散光性弱视患儿视感知学习疗法组的总有效率均高于传统疗法组,组间比较差异均有统计学意义(P<0.05).结论:8岁以下的顺、逆规散光性弱视患者在视感知学习疗法中的总有效率高于其在传统疗法的总有效率.%Objective: To compare the curative effects of visual perceptual learning and traditional treatment for the children under 8 years with astigmatism amblyopia with rule and astigmatism amblyopia against rule. Methods: 252 children (504 eyes) under 8 years with astigmatism amblyopia with rule and astigmatism amblyopia against rule were divided into visual perceptual learning group (154 children, 308 eyes) and traditional treatment group (98 children, 196 eyes), then the results were analyzed statistically after two years. Results; The total effective rate in visual perceptual learning group was significantly higher than that in traditional treatment group (P < 0. 05) . Conclusion;The total effective rate in the children under 8 years with astigmatism amblyopia with rule and astigmatism amblyopia against rule treated with visual perceptual learning is significantly higher than that treated with traditional treatment

  5. Effect of corneal biomechanical parameters in astigmatic keratotomy%角膜生物力学特性对散光性角膜切开术影响

    Institute of Scientific and Technical Information of China (English)

    邹湖涌; 王勤美; 俞阿勇; 郑志利; 芦群

    2012-01-01

    目的 探讨屈光性晶状体置换联合散光性角膜切开术术后角膜生物力学特性的改变及其对手术效果的影响.方法 收集角膜散光≥1.50D的患者,在屈光性晶状体置换术时联合行散光性角膜切开术.术前,术后1周、1、3、6个月用眼反应分析仪(Ocular response analyzer,Reichert,Depew,NY)测量角膜阻力因子(corneal resistance factor,CRF)、角膜滞后性(corneal hysteresis,CH)、Goldmann眼压(Goldmann correlated intraocular pressure,IOP);用角膜地形图仪(Pentacam ver.1.11;Oculus,Germany)观察角膜散光的变化.采用重复测量数据方差分析及Pearson相关分析进行统计分析.结果 共23例(32只眼).CRF、CH术后1周、1个月均低于术前水平(P<0.05),术后3个月、6个月与术前比较差异均无统计学意义(P>0.05).IOP术后各时间点与术前比较差异均无统计学意义(P>0.05).散光矢量分解后术后J0的变化与CRF、CH负相关(P<0.05),与IOP无相关(P>0.05).J45的变化与CRF、CH、IOP无相关(P>0.05).结论 屈光性晶状体置换术联合散光性角膜切开术不会引起角膜生物力学特性的长期改变,CRF、CH对散光性角膜切开术手术效果产生一定的影响.%Objective To study the changes of corneal biomechanical parameters and the correlations between surgical induced corneal astigmatism and corneal biomechanical parameters in Astigmatic Keratotomy (AK).Methods Patients with corneal astigmatism ≥1.50D underwent AK during refractive intraocular lens exchange.Corneal resistance factor (CRF),Corneal hysteresis (CH) and Goldmann-correlated intraocular pressure (IOP) measurements were obtained with the Ocular Response Analyzer (ORA,Reichert.,Depew,NY) before and 1 week,1 month,3 months and 6 months after surgery.Corneal astigmatism was also measured with Scheimpflug imaging (Pentacam ver.1.11; Oculus,Germany).Results Thirty-two eyes were included in this study.Both CRF and CH decreased briefly at 1 week and

  6. The influence of corneal astigmatism on retinal nerve fiber layer thickness and optic nerve head parameter measurements by spectral-domain optical coherence tomography

    OpenAIRE

    Liu Lin; Zou Jun; Huang Hui; Yang Jian-guo; Chen Shao-rong

    2012-01-01

    Abstract Background To evaluate the influence of corneal astigmatism (CA) on retinal nerve fiber layer (RNFL) thickness and optic nerve head(ONH) parameters measured with spectral-domain optical coherence tomography (OCT) in high myopes patients before refractive surgery. Methods Seventy eyes of 35 consecutive refractive surgery candidates were included in this study. The mean age of the subjects was 26.42 ± 6.95 years, the average CA was −1.17 diopters (D; SD 0.64; range −0.2 to-3.3D), All s...

  7. Combined special capsular tension ring and toric IOL implantation for management of post-DALK high regular astigmatism with subluxated traumatic cataract

    Directory of Open Access Journals (Sweden)

    Asim Kumar Kandar

    2014-01-01

    Full Text Available We report a case of 18-year-old male who has undergone phacoemulsification with implantation of toric IOL (AcrySof IQ SN6AT9 after fixation of lens capsule with Cionni′s capsular tension ring (CTR for subluxated traumatic cataract with high astigmatism after deep anterior lamellar keratoplasty (DALK. He underwent right eye DALK for advanced keratoconus four years earlier. He had history of trauma one year later with displaced clear crystalline lens into  anterior chamber and graft dehiscence, which was repaired successfully. The graft survived, but patient developed cataract with subluxated lens, for which phacoemulsification with implantation of toric IOL was done. Serial  topography showed regular corneal astigmatism of -5.50 diopter (K 1 42.75 D @130°, K 2 48.25 D @40°. At 10-month follow-up, the patient has BCVA 20/30 with + 0.75 DS/- 1.75 DC @ 110°. The capsular bag is quite stable with well-centered IOL. Combination of Cionni′s ring with toric IOL could be a good option to manage such complex cases.

  8. Pentacam与IOL Master测量角膜曲率与散光的比较%Comparison of keratometry and astigmatism measured by Pentacam and IOL Master

    Institute of Scientific and Technical Information of China (English)

    黄旺斌; 陈子林

    2016-01-01

    Objective To compare the difference of keratometry and astigmatism measured by Pentacam and IOL Master in age-related cataract operations. Methods The inspection of involved patients was taken by the same operator.The data of keratometry and corneal astigmatism were the average of three sets. Paired t tests ,A simple linear correlation analysis and the Bland-Altman method were used to evaluate the difference, correlation and agreement of keratometry respectively. Wilcoxon signed rank test and simple statistical analysis were performed to compare the difference of corneal astigmatism. Results The mean keratometry value were (44.14±1.49) D (male), (44.73±1.55) D (female) for Pentacam,and (44.27±1.50) D (male)、(44.86±1.56) D (female) for IOL Master. There was significant statistical difference in keratometry value both in the terms of instrument and sex.The correlation of keratometry was high(r=0.986). The absolute value of the maximum difference was 1.19 D in the 95%limits of agreement of Bland-Altman histogram. The astigmatism degree and axis were (0.77±0.52) D and (85.38 ±53.36)° for Pentacam, (0.90±0.61) D and (85.38 ±53.36)° for IOL Master.There was obivous statistical difference in astigmatism degree between the two instruments, while, no great difference in axis.The percent of astigmatism axis difference above 10° was 44.4%. Conclusions Both Pentacam and IOL Master can measure corneal curvature and astigmatism of cataract patients accurately.There are good correlation and poor consistency.%目的:比较Pentacam与IOL Master测量年龄相关性白内障患者角膜曲率、角膜散光的差异。方法选取2013年7至10月在惠州市中心人民医院接受手术治疗的年龄相关性白内障患者109例(共171眼),对入选患者由同一检查者检查,各收集3组数据并取其均值为对应测量值。角膜曲率的差异性、相关性、一致性分别采用配对样本t检验、线性相关分析、Bland-Altman法进行

  9. Academic and Workplace-related Visual Stresses Induce Detectable Deterioration Of Performance, Measured By Basketball Trajectories and Astigmatism Impacting Athletes Or Students In Military Pilot Training.

    Science.gov (United States)

    Mc Leod, Roger D.

    2004-03-01

    Separate military establishments across the globe can confirm that a high percentage of their prospective pilots-in-training are no longer visually fit to continue the flight training portion of their programs once their academic coursework is completed. I maintain that the visual stress induced by those intensive protocols can damage the visual feedback mechanism of any healthy and dynamic system beyond its usual and ordinary ability to self-correct minor visual loss of acuity. This deficiency seems to be detectable among collegiate and university athletes by direct observation of the height of the trajectory arc of a basketball's flight. As a particular athlete becomes increasingly stressed by academic constraints requiring long periods of concentrated reading under highly static angular convergence of the eyes, along with unfavorable illumination and viewing conditions, eyesight does deteriorate. I maintain that induced astigmatism is a primary culprit because of the evidence of that basketball's trajectory! See the next papers!

  10. 905例17至19岁青年人散光与近视度的相关性分析%Research on the epidemiology of astigmatism in 905 cases 17-19 year old youths

    Institute of Scientific and Technical Information of China (English)

    刘保松; 袁媛; 彭华琮

    2012-01-01

    Objective To determine the prevalence and development of astigmatism in 17-19 years of age young people and find out the relationship between the change in axis category and the amount of astigmatism with different amounts of myopia degree.Methods This was a cross-sectional study.Nine hundred and five 17-19 years of age young people were selected for the study using a random digital method to determine the refractive errors and axes of astigmatism.A chi-square test was used to analyze the data.Results Astigmatism degree in the -0.26-1.50 D with-the-role range accounts for the largest percentage.For males,with-the rule astigmatism was found in 71.7% who had high myopia,about 71.1% who had moderate myopia,and 69.2% who had low myopia.With-the-rule astigmatism was found in female group who had high myopia section about 74.6%,approximately 84.0% who had moderate myopia and low-degree myopia section approximately 92.0%.The most common amount of astigmatism was -0.25-1.00 D for all axes of myopia in both males and females in all myopic degrees.A higher proportion of males in the high myopia group had with-the-rule astigmatism (x2=4.619,P=0.032).A higher proportion of women had with-the-rule astigmatism in low-degree myopia group higher than that in the comparative male group (x2=8.705,P=0.003).A higher proportion of males in the low myopia group had ≤-2.00 diopters of astigmatism proportion than in the other two male groups (x2=6.635,4.256,P<0.05) and as the myopic degree is higher,the proportion of males with ≤-2.00 diopters decreased.The proportion of females in the high myopia group with ≤-2.00 diopters of astigmatism was lower than that in the moderate myopia group (x2=11.780,P=0.001).Conclusion Among youths 17-19 years of age,with-the-rule astigmatism accounted for the largest percentage.Males with low myopia had a higher proportion of ≤-2.00 diopters of astigmatism compared to males in the other two groups and,as myopic degree increased

  11. Wavefront-Guided Photorefractive Keratectomy with the Use of a New Hartmann-Shack Aberrometer in Patients with Myopia and Compound Myopic Astigmatism

    Directory of Open Access Journals (Sweden)

    Steven C. Schallhorn

    2015-01-01

    Full Text Available Purpose. To assess refractive and visual outcomes and patient satisfaction of wavefront-guided photorefractive keratectomy (PRK in eyes with myopia and compound myopic astigmatism, with the ablation profile derived from a new Hartmann-Shack aberrometer. Methods. In this retrospective study, 662 eyes that underwent wavefront-guided PRK with a treatment profile derived from a new generation Hartmann-Shack aberrometer (iDesign aberrometer, Abbott Medical Optics, Inc., Santa Ana, CA were analyzed. The preoperative manifest sphere ranged from −0.25 to −10.75 D, and preoperative manifest cylinder was between 0.00 and −5.25 D. Refractive and visual outcomes, vector analysis of the change in refractive cylinder, and patient satisfaction were evaluated. Results. At 3 months, 91.1% of eyes had manifest spherical equivalent within 0.50 D. The percentage of eyes achieving uncorrected distance visual acuity 20/20 or better was 89.4% monocularly and 96.5% binocularly. The mean correction ratio of refractive cylinder was 1.02 ± 0.43, and the mean error of angle was 0.00 ± 14.86° at 3 months postoperatively. Self-reported scores for optical side effects, such as starburst, glare, halo, ghosting, and double vision, were low. Conclusion. The use of a new Hartmann-Shack aberrometer for wavefront-guided photorefractive keratectomy resulted in high predictability, efficacy, and patient satisfaction.

  12. Observation of corneal astigmatism induced by 2.2mm micro-incision coaxial phacoemulsification%同轴微切口白内障超声乳化术后角膜散光的临床观察

    Institute of Scientific and Technical Information of China (English)

    林英杰; 梁先军; 何锦贤; 赵抒羽; 杨雪艳; 曾胜

    2013-01-01

    目的:评价2.2mm同轴微切口白内障超声乳化手术后角膜散光的变化.方法:老年性白内障患者56例78眼,将患者随机分为2组,2.2mm组38眼,3.0mm组40眼,分别行2.2mm同轴微切口白内障超声乳化联合人工晶状体(IOL)植入术及3.0mm常规白内障超声乳化联合IOL植入术,术后1,3mo评价术眼裸眼视力(uncorrected visual acuity,UCVA)、角膜散光、术源性角膜散光(surgically induced astigmatism,SIA).结果:术后1mo,2.2mm组角膜散光为0.85±0.42D,3.0mm组角膜散光为1.18±0.37D,两组角膜散光比较有统计学差异(P0.05).术后UCVA,在术后1mo和3mo,2.2mm组均优于3.0mm组.结论:2.2mm同轴微切口白内障超声乳化手术后能产生更小的SIA和更好的UCVA.%AIM: To evaluate the effect of 2. 2mm micro-incision coaxial phacoemulsification on corneal astigmatism and surgically induced astigmatism (SIA).METHODS: Fifty-six cataract patients (78 eyes) were randomized into two groups: 38 eyes in the 2. 2mm incision group and 40 eyes in the 3. Omm group. Torsional phacoemulsification was followed. Corneal astigmatism, SIA and uncorrected distance visual acuity (UCVA) were assessed at 30 and 90 days after cataract surgery.RESULTS: One month postoperatively, the corneal astigmatism of the 2.2mm group was 0.85±0.42D and the 3.0mm group was 1. 18 ± 0. 37D. Three months postoperatively, the corneal astigmatism of the 2. 2mm group was 0. 74 ± 0. 40D and the 3. Omm group was 1. 00 ± 0. 30D. One month and 3 months postoperatively, SIA of the 3. Omm group was greater than SIA of the 2. 2mm group ( P< 0. 05). In the 3. Omm group, mean SIA at 1 month was greater than SIA at 3 months ( P<0. 05), but SIA was similar. There was no statistical significance between the mean SIA between 1 month and 3 months. Postoperative UCVA was better in the 2. 2mm group at both 1 month and 3 months postoperatively.CONCLUSION; 2. 2mm micro - incision coaxial phacoemulsification contributed to postoperative corneal

  13. The influence of corneal astigmatism on retinal nerve fiber layer thickness and optic nerve head parameter measurements by spectral-domain optical coherence tomography

    Directory of Open Access Journals (Sweden)

    Liu Lin

    2012-05-01

    Full Text Available Abstract Background To evaluate the influence of corneal astigmatism (CA on retinal nerve fiber layer (RNFL thickness and optic nerve head(ONH parameters measured with spectral-domain optical coherence tomography (OCT in high myopes patients before refractive surgery. Methods Seventy eyes of 35 consecutive refractive surgery candidates were included in this study. The mean age of the subjects was 26.42 ± 6.95 years, the average CA was −1.17 diopters (D; SD 0.64; range −0.2 to-3.3D, All subjects in this study were WTR CA. 34 eyes were in the normal CA group with a mean CA was −0.67 ± 0.28D, 36 eyes were in the high CA group with an average CA of −1.65 ± 0.49D. All subjects underwent ophthalmic examination and imaging with the Cirrus HD OCT. Results No significant difference was noted in the average cup-to-disk ratio, vertical cup-to-disk ratio and cup volume (all P values > 0.05. Compared with the normal CA group, the high CA group had a larger disc area and rim area, thinner RNFL thickness in the temporal quadrant, and the superotemporal and inferotemporal peaks were farther to the temporal horizon (All P values P values > 0.05. Conclusions The degree of with-the-rule CA should be considered when interpreting ONH parameters and peripapillary RNFL thickness measured by the Cirrus HD OCT. Virtual slides The virtual slide(s for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1148475676881895

  14. Optical system design of broadband astigmatism-free czerny-turner spectrometer%宽谱段消像散Czerny-Turner光谱仪光学系统设计

    Institute of Scientific and Technical Information of China (English)

    赵意意; 杨建峰; 薛彬; 闫兴涛

    2014-01-01

    针对光谱仪小型化、高分辨率的发展趋势,设计了一种结构简单、宽谱段、消像散的小型光谱仪。具体分析了折叠光路Czerny-Turner光谱仪各种像差的原理和校正方法。推导了柱透镜宽谱段消像散的理论方程。作为实例,设计了一款谱段为300~900 nm、物方数值孔径0.08的小型光谱仪。该光谱仪采用折叠光路结构以减小尺寸,添加柱透镜以消除整个谱段的像散。结果表明:该光谱仪结构简单紧凑,体积小,实现了宽谱段的消像散,全谱段光谱分辨率优于0.5 nm。%For the development trend of miniaturization and high-resolution of spectrometer, an optical design with a simple structure, broadband, astigmatism-corrected micro spectrometer was designed. The principle and correction method of the aberration of crossed beam czerny-turner spectrometer were analyzed in detail. The broadband astigmatism-corrected theory equations using cylindrical lens were deduced. For example, a micro spectrometer operating in 300-900 nm with an object NA of 0.08 has been designed. This spectrometer adopted crossed beam structure to minish its volume and used a cylindrical lens to remove astigmatism over the full bandwidth. The analyzed results demonstrated that this spectrometer with compact configuration and small volume corrected the astigmatism in the wide spectral region. The resolution of the spectrometer was better than 0.5 nm in the whole spectral region.

  15. Epi-LASIK 和 LASIK 治疗近视散光的早期疗效对比观察%Comparative study of Epi -LASIK and LASIK for myopic astigmatism

    Institute of Scientific and Technical Information of China (English)

    罗栋强; 王华; 何书喜; 陈蛟

    2013-01-01

    AIM: To analyze the effects of epipolis laser in situ keratomileusis ( Epi - LASIK ) and laser in situ keratomileusis ( LASIK ) for treatment of myopic astigmatism. METHODS: For treatment of myopic astigmatism, 32 patients (64 eyes) treated by Epi-LASIK and 63 patients (126 eyes) received LASIK.By their degree of astigmatism, the eyes were divided into GroupⅠ(-0.25~-2.75) DC and GroupⅡ(-3.0~-5.0) DC.During the 6-month follow-up, the early effects of the two operations were observed and compared in terms of uncorrected visual acuity ( UCVA) , best corrected visual acuity ( BCVA ) , residual astigmatism, corneal healing, intraocular pressure ( IOP) , corneal topography. RESULTS: In Group Ⅱ, UCVA better than 20/20 was achieved in 87.5%of the eyes subjected to Epi-LASIK and in 63.3% of the eyes subjected to LASIK, with significant difference between them (χ2 =4.055, P<0.05); residual astigmatism was-0.41±0.30D for the Epi-LASIK eyes and-0.74 ±0.36D for the LASIK eyes, with significant difference between them ( t =2.672, P <0.05 );postoperative corneal astigmatism was 0.63±0.34D for the Epi-LASIK eyes and 0.81 ±0.52D for the LASIK eyes with significant difference between them (t=2.234, P<0.05). CONCLUSION: For treatment of high astigmatism (≥-3 .0 0 D ) , Epi-LASIK is more effective and predictive than LASIK.%目的:探讨分析角膜微型刀上皮瓣下准分子激光原位角膜磨镶术( epipolis laser in situ keratomileusis , Epi-LASIK)和准分子激光原位角膜磨镶术( laser in situ keratomileusis , LASIK)治疗近视散光的疗效。方法:近视散光行 Epi-LASIK 治疗的患者32例64眼, LASIK治疗的患者63例126眼,将患者根据柱镜度数分为2组:Ⅰ组(柱镜-0.25~-2.75D,Epi-LASIK 20例、LASIK 48例)、Ⅱ组(柱镜-3.00~-5.00D,Epi-LASIK 12例、LASIK 15例)。随访6 mo观察两种术式的疗效。对比两组患者的术后裸眼视力( uncorrected visual acuity , UCVA

  16. 应用Fourier分析法研究准分子激光治疗散光的准确性%Study on the accuracy of excimer laser for myopic astigmatism with fourier analysis

    Institute of Scientific and Technical Information of China (English)

    胡亮; 徐鹏; 崔贺; 谢文加; 王勤美

    2013-01-01

    关性有统计学意义(r=0.361,P< 0.01).飞秒LASIK术后中度近视组RJ0与CJ0 (r=0.393,P< 0.01),RJ0与TJ0(r=0.596,P< 0.01),RJ45与TJ0(r=0.396,P<0.01)相关性均有统计学意义.结论:①鹰视酷眼准分子激光行OUP-SBK或飞秒LASIK手术矫正中高度近视患者的顺规散光具有较高的准确性;②手术对顺规散光患者垂轴成分的矫正准确性高于对斜轴散光成分的矫正准确性;③手术矫正中高度近视患者的顺规散光准确性相近.%Objective:To evaluate the accuracy of Cool Excimer Laser System for myopic astigmatism in One Use-Plus Sub-Bowman's keratomileusis (OUP-SBK) and Femtosecond Laser In Situ Keratomileusis (FSLASIK) with Fourier Analysis and develop a customized nomogram for astigmatic patients.Methods:Retrospectively reviewed the charts of 542 eyes (OUP-SBK:318 eyes; FS-LASIK:224 eyes),who had excimer laser surgery in Eye Hospital of Wenzhou Medical College during Jan 2012 to March 2012,with an inclusion criteria as:WTR astigmatism ≥-0.5 D,myopia >-3 D.The moderate and high myopia groups were divided respectively according to baseline myopia.Preoperative and 3 to 6 months postoperative examinations included:refraction,corneal topography,pachymetry,best spectacles corrected visual acuity (BSCVA).Fourier Analysis was used to transform preoperative astigmatism to TJ0 and TJ45; preoperative corneal astigmatism to CJ0 and CJ45;postoperative residual astigmatism to RJ0 and RJ45.Group t test and Pearson test were used for statistical analysis.Results:① Residual Astigmatism.OUP-SBK moderate myopia group:RJ0=(0.012 ± 0.161)D,RJ45=-(0.012 ± 0.128)D; OUP-SBK high myopia group:RJ0=(0.026 ± 0.239)D,RJ45=(-0.029 ± 0.194)D,the difference between moderate and high myopia group was not statistically significant (P=0.697,0.402).Femtosecond LASIK moderate myopia group:RJ0=(0.053 ± 0.248)D,RJ45=(-0.039 ± 0.186)D; femtosecond LASIK high myopia group:RJ0=(0.042 ± 0.267)D,RJ45=(0.044 ± 0.261)D,the difference between

  17. Phakic posterior chamber intraocular lens implantation in high myopia with astigmatism%后房型有晶状体眼人工晶状体植入术治疗高度近视及散光

    Institute of Scientific and Technical Information of China (English)

    刘莉; 陈自新; 陈茂盛; 马金花; 陈荥培

    2011-01-01

    目的 探讨后房型有晶状体眼人工晶状体植入术治疗高度近视及散光的安全性和疗效性.方法 后房型有晶状体眼人工晶状体植人术治疗高度近视及散光22例39只眼.术前屈光度(等效球镜)为-7.0~-24.0D,平均(-14.50D±3.50)0;散光-0.50~-4.50D,平均(-2.25±1.32)D.术后检查视力、眼压、裂隙灯显微镜,前房角,前房深度,人工晶状体拱高,角膜内皮细胞计数.随访3-18个月.结果 术后3个月,38只眼视力达到或超过术前矫正视力.等效球境-0.50~-2.25D,平均(-0.75±0.38)D,散光度0.25~2.75D,平均(1.03±0.23)D,术后7只眼早期(2h后观察)眼压升高,经降眼压处理,24h内恢复正常.无一例出现青光眼、白内障、人工晶状体偏移及网脱等并发症.结论 后房型有晶状体眼人工晶状体植入术治疗高度近视及散光保留了生理性调节、并发症少、安全有效,是临床矫正高度近视散光比较理想的一种方法.%Objective To valuate the efficacy, safety stability and predictability of implanting a posterior chamber phakic intraocular lens to correct high myopia with astigmatism. Methods Thirty-nine eyes of 22 patients with high myopia were treated with ICL implantation. The range of preop-erative myopia diopters was -7.0 D to -24.0 D, mean -14.50 D±3.50 D, astigmatism ranges -0.50 D to -4.50 D, mean 2.25±1.32 D. All of 39 eyes were implanted ICL successful and had been followed up for 3 to 18 months. The follow up examination included visual acuity, refraction tonometer, slit lamp examination, chamber depth, chamber angle and space between crystal lens and IOL. Results One week after operation, the uncorrected visual acuity of 38 eyes were same or better than the pre-operative best corrected visual acuity (BCVA). The refractive diopters were from -0.50 to -2.25 D,mean -0.75±0.38 D. Astigmatism was 0.25 to 2.75 D, mean 1.03±0.23 D. Complications were seen in 7 eyes of 6 patients who had increased intraocular

  18. 人工晶体因素对白内障角膜散光患者术后获益的影响%Influence of different intraocular lenses on postoperative benefit of cataract patients with astigmatism

    Institute of Scientific and Technical Information of China (English)

    巨朝娟; 楚妙; 张骞; 林伟

    2015-01-01

    BACKGROUND:Monofocal and multifocal Toric intraocular lens that have been widely used in clinic exhibit xcelent biological and optical characteristics and have good safety and stability after implantation. OBJECTIVE:To compare the outcomes and rotation stability in patients with cataract and astigmatism after implantation of monofocal and multifocal intraocular lens. METHODS:A total of 210 patients with cataract and astigmatism who received phacoemulsification and intraocular lens implantation were included in this study. Of them, 105 patients were assigned to monofocal intraocular lens implantation and the other 105 patients to multifocal intraocular lens implantation. Uncorrected visual acuity, best corrected visual acuity, residual astigmatism were reexamined at 1, 3 weeks and 1 month after surgery. The rotation of Toric intraocular lens was determined. The incidence of complications and spectacles- independent rate were recorded. RESULTS AND CONCLUSION:Visual acuity and residual astigmatism in each group were significantly improved after 1 week of intraocular lens implantation (P < 0.05); furthermore, these two indicators became better over time. Improvement of visual acuity and residual astigmatism in multifocal intraocular lens group was more obvious than that in monofocal intraocular lens group. Postoperative intraocular lens rotation at < 5° occurred in both groups. The intraocular lens rotation degree in multifocal intraocular lens group was higher than that in monofocal intraocular lens group at different time points (P < 0.05). There were no significant differences in incidence of complications and spectacles-independent rates between two groups at 1 month after surgery. These results demonstrate that multifocal Toric intraocular lens provides better visual acuity and residual astigmatism improvement, while monofocal Toric intraocular lens provides better rotation stability.%背景:单焦点与多焦点Toric散光型人工晶体具有良好的生物

  19. Toric设计角膜塑形镜矫治青少年复合性近视散光的临床观察%Clinical observation of adolescent compound myopic astigmatism treated by toric design orthokeratology

    Institute of Scientific and Technical Information of China (English)

    郭雷; 张悦; 陆新; 周爽; 刘岩

    2016-01-01

    Objective To investigate the clinical effects and safety of Toric design orthokeratology on compound myopic astigmatism in adolescents.Methods Toric design orthokeratology were performed to correct 68 compound myopic astigmatism eyes of 36 (9-14 years old) cases,with myopic degree:-1.50~-5.00 D,and astigmatism:-1.50~-3.50 D.The naked vision,diopter,corneal topography,the survey of the health status in ocular anterior segment,and the wearing status of toric design orthokeratology,were measured and recorded at baseline,and 1 day,1 week,1 month,3 months,6 months,as well as 12 months post treatment.Results The naked vision (≥0.8) was larger than that of baseline significantly (P <0.05),from 1 week to 12 months.In addition,the diopters of naked eyes decreased in 1 week,1 month,3 months and 12 months significantly (P <0.05),compared with the baseline.Moreover,there was a significant difference in flat and steep K value of anterior 3mm surface (P <0.05),instead of posterior surface.Besides,the thickness of central 3-5mm cornea,as well as the height of posterior surface in corneal topography failed to show the significant difference (P >0.05).Finally,the satisfaction of subjective visual quality based on the good wearing status of toric design orthokeratology,non-infection of ocular anterior segment,and non-thinning of cornea post treatment.Conclusions Toric design orthokeratology can correct compound myopic astigmatism in adolescents to some degree,effectively and safely,in spite of the limited range of astigmatism correction.%目的 探讨Toric设计角膜塑形镜矫治青少年复合性近视散光的临床疗效及安全性.方法 对2014年1月至2015年12月在中国医科大学第一医院眼视光中心门诊就诊的9~14岁复合性近视散光(近视度-1.50~5.00 D,散光度-1.50~3.5 D)患者36例(68只眼)给予Toric设计角膜塑形镜进行矫正.分别测量戴镜前及戴镜后1d、1周、1个月、3个月、6个月、12个月的裸眼

  20. Application of improved orthokeratology for myopic adolescents with moderate-to-high astigmatism%常规角膜塑形术应用于较高度角膜散光患者的治疗效果

    Institute of Scientific and Technical Information of China (English)

    韦伟; 申笛; 薛亚林; 张长宁

    2015-01-01

    目的 观察常规角膜塑形术矫治较高度角膜散光患者的临床效果.方法 回顾性研究.近视度为-0.50~-6.25 D,顺规角膜散光为-1.76~-3.02 D,年龄为6~18岁的患者33例(60眼),观察戴角膜塑形镜1d、1周、1个月、3个月、6个月、1年后的视力改变情况,并结合角膜地形图改变情况对矫治效果进行分级.用logistic回归分析较高度角膜散光患者成功验配角膜塑形镜的影响因素.结果 配戴角膜塑形镜前,患者的裸眼视力(UCVA)为4.15±0.23,配戴后1d、1周、1个月、3个月、6个月、1年后的视力分别为4.59±0.23、4.90B±0.11、4.96±0.07、4.86±0.25、4.93±0.10、4.93±0.11,配戴后UCVA与戴镜前比较,差异有统计学意义(F=148.08,P<0.01).配戴角膜塑形镜1个月后矫治效果Ⅰ级35眼(58%),Ⅱ级15眼(25%),Ⅲ级8眼(13%),Ⅳ级2眼(3%).患者屈光度、角膜散光度、角膜下方与上方平均屈光度差值(I-S值)、角膜陡K(SK)值和角膜e值对矫治效果均无显著影响.结论 采用改良的验配方法,常规球面角膜塑形镜也可以选择性用于自身条件较好的1.50 D以上角膜散光近视患者,并取得良好的矫治效果.%Objective To investigate an improved orthokeratology fitting method for myopic adolescents with moderate-to-high astigmatism;to analyze successful fitting factors.Methods This was a retrospective analysis of 33 patients (60 eyes) ranging in age from 6 to 18 years with 0.5 to 6.25 diopters (D) of myopia and with-the-rule corneal astigmatism of 1.76 to 3.02 D who were fitted with orthokeratology lenses with a spherical design.Treatment outcomes were evaluated by comparing eyes before lens wear and after wearing the lenses for 1 day, 1 week, 1 month, 3 months, 6 months and 12 months.The results were graded on corneal topography and visual acuity.Orthokeratology central-fitting factors were analyzed in patients with moderate-to-high astigmatism using logistic regression.Results The

  1. 有晶体眼后房型人工晶体植入治疗高度近视及散光%Clinical research of the implantation of phakic posterior chamber intraocular lens (ICL) for high myopia with astigmatism

    Institute of Scientific and Technical Information of China (English)

    廖荣丰; 汪永; 周艳峰; 刘伦; 刘兴华; 封利霞

    2009-01-01

    目的 观察和探讨后房型有晶体眼人工晶体植入术治疗高度近视及散光的效果及安全性.方法 后房型有晶体眼人工晶体植入术治疗高度近视及散光28例56眼.术前屈光度(等效球镜)为-7.0~-22.50D,平均(-12.42±3.50)D.散光0.37~6.5D,平均(1.92±1.32)D.所有患者随访3~24个月.术后检查视力、眼压,裂隙灯检查眼前部情况.结果 术后3个月,所有病例术后达到或超过术前最佳矫正视力.等值球镜,0.25~1.50D,平均(0.534±0.408)D.散光度0.25~1.50D,平均(0.564±0.289)D.术后并发症:4例7眼术后早期眼压升高,经降眼甩治疗,3~4天后眼压正常.结论 后房型有晶体眼人工晶体植入术治疗高度近视及散光效果确切,预测性好,手术安全.高度近视,尤其是超高度近视以及角膜薄不适合准分子激光矫正的患者是理想的治疗对象.%Objective To observe and investigate the efficacy and safety of the implantation of phakic posterior chamber intraocular lens (ICL) for high myopia with or without astigmatism. Methods 56 eyes of 28 patients with high myopia were treated with ICL implanta-tion. The range of preoperative myopia diopters was-7.0 to-22. 5D, mean-12.42±3.50 D. Astigmatism ranges 0.37 to 6.5D, mean 1.92±1.32D. All of 56 eyes were implanted ICL successfully and have been followed up for 3 to 24 months. The follow up examination included visual acu-ity, refraction, tonometer, slit lamp examination ,and space between crystal lens and IOL. Results Three months after operation, the uncor-rected visual acuity of every eye was same or better than the pre-operative best corrected visual acuity (BCVA). The refractive diopters were from 0.25 to 1.50D, mean 0.534±0.408D. Astigmatism were 0.25 to 1.50D, mean 0.564±0.289D.complications were secondary glaucoma. 7 eyes of 4 patients had increased intraocular pressure shortly after surgery. After treatment, the intraocular pressure became normal in 3 to 4 days. Con

  2. Efficacy of phacoemulsification combined with intraocular lens implantation for senile cataract with corneal astigmatism%超声乳化联合人工晶状体植入治疗老年白内障合并角膜散光

    Institute of Scientific and Technical Information of China (English)

    董永孝; 黄立; 关小荣; 马艳; 韩文涛; 赵金; 吕菊迎

    2015-01-01

    目的:对老年性白内障合并角膜散光患者采用超声乳化白内障摘除术联合散光型人工晶状体( intraocular lens,IOL)植入的临床疗效进行评估。方法:采用随机数字表法将本院眼科中心收治的64例84眼老年性白内障合并散光患者分为散光型IOL组33例42眼和球面IOL组31例42眼,散光IOL组采用超声乳化白内障摘除术联合散光型人工晶状体植入术治疗,球面IOL组采用常规颞侧透明角膜切口超声乳化白内障摘除球面人工晶状体植入联合陡峭轴位上一对角膜缘松解切口治疗。观察两组手术前、术后3 mo 的视力分布、角膜散光度、球镜及柱镜指标(曲率、轴向、小瞳验光球镜、小瞳验光柱镜、散光轴向)的变化情况。结果:散光型IOL组和球面IOL组在术后第3 mo复查裸眼视力,与同组术前比较视力均提高(P0.05);术后3 mo散光型IOL组的小瞳验光球镜、小瞳验光柱镜值显著低于球面IOL组( P0. 05). Non-mydriatic refraction spherical and non - mydriatic refraction cylindrical of the astigmatism lOL group were significant lower than than in the spherical lOL group at 3mo post-operation(P<0. 05).• CONCLUSlON: Phacoemulsification combined with intraocular lens implantation for senile cataract with corneal astigmatism have a good clinical effect.

  3. Lente de contato de material híbrido em pacientes com ceratocone e astigmatismo miópico composto Hybrid material contact lens in keratoconus and myopic astigmatism patients

    Directory of Open Access Journals (Sweden)

    Fernando Leal

    2007-03-01

    óculos, exceto para a freqüência B (3 cpg, maior nos usuários de óculos. As aberrações de alta ordem analisadas apresentaram diminuição estatisticamente significante, quando comparados os pacientes sem e com uso de lentes de contato, com exceção da aberração esférica e do coma. CONCLUSÃO: A lente de contato de material híbrido, quando utilizada por portadores de ceratocone e astigmatismo miópico composto, propiciaram desempenho visual e conforto satisfatórios, em níveis que não diferiram, das lentes de contato rígidas-gás-permeáveis nos dois grupos de pacientes.PURPOSE: To evaluate comfort and visual performance in relation to two different used contact lens types: hybrid material (HM and rigid-gas-permeable (RGP, in patients with regular myopic astigmatism and with keratoconus. METHODS: A randomized, double masked, prospective study of 22 patients with the diagnosis of myopic astigmatism (8 with myopic astigmatism and 14 with keratoconus was conducted. Fifteen patients were female and 7 were male, and mean age was: 32.13 ± 8.12 years. In one of the eyes a rigid-gas-permeable contact lens was adapted (DK 30, and in the other a hybrid material contact lens was adapted (DK 23. All patients were submitted to the following tests: measurement of comfort level by means of the analogical visual scale, tear break-up time, best corrected visual acuity with the Bailey-Lovie scale adapted for 4 meters, functional acuity contrast test (FACT and wavefront analysis. RESULTS: In relation to comfort, there was no association with the evaluated contact lens type (p=0.350. There was a variation in comfort level during the first 7 days. The visual acuity increased between the 7th and the 15th day of adaptation. Visual acuity stabilized right after this period. The visual acuity did not show differences in relation to the studied lens type. It was verified that there was no difference in the tear break-up time (p=0.989 in relation to the studied lenses type and

  4. Posição viciosa de cabeça por astigmatismo mal corrigido: relato de caso Abnormal head position caused by incorrect prescription for astigmatism: case report

    Directory of Open Access Journals (Sweden)

    Flávia Augusta Attié de Castro

    2005-10-01

    Full Text Available A posição viciosa de cabeça é uma condição compensatória que visa proporcionar aos pacientes melhor rendimento visual. Pode ser causada por problemas oftalmológicos, como distúrbios oculomotores (nistagmos, estrabismos e altos astigmatismos. No entanto, compromete a estética e, a longo prazo, pode causar transtornos ortopédicos (coluna cervical e assimetrias faciais. Relatamos o caso de uma garota, JL, 8 anos, com cabeça inclinada para esquerda havia vários anos. Fazia uso de óculos prescritos em outro serviço para correção de astigmatismo misto: OD= +2,00 DE Ç -5,50 DC a 180º e OE= +2,25 DE Ç -5,75 DC a 180º. No exame oftálmico, a paciente apresentava cabeça inclinada para a esquerda e acuidade visual com correção de 0,5 no OD e 0,7 OE. Os testes de cobertura simples e alternado não evidenciaram desvio ocular. Rotações oculares, biomicroscopia e fundoscopia também não mostraram alterações. Na refratometria sob cicloplegia e teste de lentes foram encontrados: OD= +3,50 DE Ç -6,00 DC a 10º e OE= +3,50 DE Ç -6,00 DC a 170º, com acuidade visual igual a 1,0 nos olhos direito e esquerdo. Foram prescritas as lentes encontradas no exame e a paciente retornou com a correção nova sem a inclinação de cabeça. Erros refracionais mal corrigidos também podem gerar torcicolo e, muitas vezes, passam despercebidos. Refratometria sob cicloplegia e teste de lentes são fundamentais para um diagnóstico preciso.Abnormal head position is a compensatory condition which improves patients' vision. It can be caused by ophthalmological problems such as oculomotor imbalances (strabismus, nystagmus and high astigmatisms. However, it results in esthetic impairment, orthopedic trouble and facial asymmetries. We describe a case of a girl, JL, 8 years, with abnormal head position tilted to the left since the last glasses were prescribed. The correction used by the patient was: right eye = +2.00 sph à -5.5 cyl 180° and left eye = +2

  5. The expression of the correction of corneal astigmatism in the point spread function analysis system of human eyes%人眼角膜散光矫正的点扩散函数分析表达

    Institute of Scientific and Technical Information of China (English)

    姜珺; 毛欣杰; 金成鹏; 吕帆

    2008-01-01

    optical imaging quality among corneal astigmatism subjects under different corrections by using the Point Spread Function analysis system (PSF). Methods PSF 1000 analyzer was used to measure retinal image quality of eyes of 26 subjects with corneal astigmatism ( sphere ranged from - 3.00 to - 6.00 DS, cylinder ranged from - 0. 75 to - 3.00 DC), who were fully corrected with three different methods respectively: spectacles (SPE), rigid gas permeable contact lenses (RGPCL) and toric soft contact lenses (TSCL). The modulation transfer function (MTF) curve was recorded and evaluated. 12 points of the MTF curve (equivalent to the 12 points of Lag Mar VA chart) were chosen for analysis. Equivalent moderate myopia 26 subjects without astigmatism were set up as control group. Results The MTF curve of each eye is enantiomorphous symmetrical Compared with the control group ( < -0. 75D), with 3.0 mm pupil, there's no statistical difference under low spatial frequency, the difference between middle and high frequency is significant ( P < 0.05 ). With 6. 0 mm pupil, there is statistical difference in all frequencies (P < 0.01 ). With simulated 3.0 mm pupil and 6.0 mm pupil, MTF values of all these three methods are statistical different. With 3.0 mm pupil, the MTF value of eyes fitted with RGPCLs is higher than that fitted with TSCLs except in the following frequency 3.00 , 3.78,4. 78,different in all frequencies ( P < 0.05 ). In all these three methods, MTF values with simulated 3.0 mm pupil are significantly higher than that with simulated 6.0 nun pupil ( P < 0.01 ). Conclusions PSF analytical method is available for offering objective data of retina imaging quality. RGPCL and its induced tear film is improved not only correcting the corneal astigmatism, but also enhances the ocular optical quality by reducing diffraction, dispersion and other high order of aberration.

  6. Application study of rigid gas permeable contact lens in patients with traumatic corneal irregular astigmatism%硬性高透氧性角膜接触镜矫正外伤性角膜散光应用研究

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    郑斌; 陈岩; 周静; 徐朝霞; 沈丽君

    2012-01-01

    Objective To evaluate the clinical value of rigid gas permeable contact lens (RGP-CL) in patients with traumatic corneal irregular astigmatism. Methods Eighteen consecutive patients (18 eyes) with traumatic corneal irregular astigmatism were fitted RGPCL.All patients were followed up at least 6 months.Preoperative data included:age,sex,eye,interval between RGPCL fitting and complete sutures removal,status of lens,uncorrected visual acuity (UCVA),spectacle visual acuity (SVA),location and size of the corneal scar,corneal astigmatism.Post-contact lens fitting data included:RGPCL visual acuity (RGPCLVA),duration of contact lens wear,the reason for drop ping out of contact lens wear,contact lens-related complications,whether or not the patient was successful in wearing the contact lcns.RGPCL fitting was considered successful if the patient judged the wearing of RGPCL to be satisfactory enough at least 8 hours of daily wear throughout the follow-up period.Decimal acuity was converted to 5-logMAR value.Data analysis used SPSS 16.0 for the paired samples t-test,two independent sample t-test and analysis of covariance. Results The average age was 20.94±13.35 years (range 5-45 years),five eyes were pseudophakic,one was aphakic and other twelve were phakic.According to the location of the corneal scar,it was found that nine eyes were in zone 1 and other nine in zone 2.The average length of scar was 4.04±2.23 mm (range 1.50-8.33 mm).The difference in the length of scar between zone 1 and zone 2 was found to be not statistically significant (t =-0.967,P =0.348).The interval from complete sutures removal to contact lens fitting was averaged 5.67±5.52 months (range 3-22 months).Mean UCVA was 4.2±0.5 (range 3.0-4.9).Mean SVA was 4.6±0.3 (range 4.0-4.9).Mean RGPCLVA was 4.9±0.1 (range 4.4-5.1).The visual acuities with contact lens were significantly better than with spectacles (t=4.143,P <0.000).RGPCLVA was 1 line better in 7 eyes,2-4 lines in 6 eyes,more than 5 lines in 4

  7. Clinical study on the stability of high myopia cataract with intraocular lens implantation on corneal astigmatism Toric%高度近视并发白内障合并角膜散光植入Toric人工晶状体稳定性的临床研究

    Institute of Scientific and Technical Information of China (English)

    张晓城; 陈茂盛; 李嘉文

    2012-01-01

    Objective To evaluate the Acrysof Toric toric surface artificial lens in cataract with high myopia associated with regular corneal astigmatism in patients with clinical effect and rotational stability.Methods A randomly selected from 2009 June to 2011 August during the cataract and corneal astigmatism in patients,phacoemulsification and implantation of Acrysof Toric IOL operation.The experimental group of 40 patients(43 eyes) ,cataract with high myopia patients (axial length≥26mm,IOL≤15D) implantation degree;optometry mirror ball( - 5.50-10.25)D,average(- 6.25 ± - 0.25)D,column mirror( - 1.25 - 4.25)D,aver-age( - 2.75 + - 0.25)D.A control group of 39 cases (40 eyes) simple astigmatism in cataract patients (axial length≤24mm≥522mm) ,optometry mirror ball ( - 0.25-1.25) ,average( -0.75+ -0.25)D,column mirror (1.50 - 4.25)D,average( - 2.50 +- 0.25)D.Postoperative March fully after mydriasis slit - lamp photography,using Adobe Photoshop software artificial lens axis a-nalysis,were recorded during the preoperative,postoperative observation of uncorrected visual acuity(UCVA) ,best corrected visual acuity(BCVA) ,postoperative corneal astigmatism and whole-eye astigmatism astigmatism,expected and actual residual astigmatism,IOL degree of rotation.Results After March,UCVA>0.5 eyes had no significant difference between two groups(P>0.05).BCVA>0.8 eyes had no significant difference between two groups(P>0.05).Postoperative residual astigmatism in March,the experimental group for the(0.56 + 0.33)D,control group(0.54 ± 0.32)D,the difference was not statistically significant (P>0.05) ; March after intraocular lens degree of rotation,the experimental group was 3.79° + 2.33°,rotation range is( - 6.25°,+ 7.78°) ;the control group was 2.75°+l.38°,rotation range was( - 4.62°,+6.15°),two groups of rotating degree of the differences were statistically significant(P0.05).Conclusion Acrysof Toric IOL March observation indicated that the implant can efficiently and stably

  8. Comparison of curative effects between first time iris recognition guided LASIK and traditional LASIK for myopic astigmatism%实时虹膜识别引导LASIK与常规LASIK治疗近视性散光疗效对比研究

    Institute of Scientific and Technical Information of China (English)

    揭黎明; 王骞; 郑林

    2012-01-01

    目的 对比观察实时虹膜识别引导的LASIK与常规LASIK治疗近视性散光的临床疗效.方法 采用随机对照研究.接受实时虹膜识别引导LASIK手术的近视性散光患者105例(196只眼)作为试验组,接受常规LASIK手术的近视性散光患者104例(195只眼)作为对照组,对两组患者术后1个月、3个月、6个月的裸眼视力、最佳矫正视力、散光度、散光轴向等进行比较.结果 静态虹膜识别检测出眼球旋转偏移角度为(2.74±2.05)°,动态虹膜识别检测眼球旋转变化范围为0~6.5°.术后6个月两组裸眼视力均≥0.5,术后最佳矫正视力均未丢失;术后6个月时,试验组裸眼视力≥术前最佳矫正视力的患者(181只眼,92.3%)多于对照组(167只眼,85.6%);试验组的平均散光(-0.22±0.20)D低于对照组(-0.34±0.35)D,差异均有统计学意义(P<0.01).术后6个月,试验组无散光眼(79只眼,40.3%)多于对照组(55只眼,28.2%),差异有统计学意义(P<0.05);对照组斜轴散光明显增加.结论 实时虹膜识别引导的LASIK能够有效校正LASIK术前和术中的眼球旋转偏差,使散光度数和轴向的治疗更加精确.%Objective To compare the clinical effects between first time iris recognition guided LASIK and traditional LASIK for myopic astigmatism.Methods In this prospective contrast study,209 patients (391 eyes) with myopic astigmatism were randomly divided into two groups:the experimental group (105 cases,196 eyes) accepted first time iris recognize-guided LASIK,and the control group (104 cases,195 eyes) accepted traditional LASIK.The naked visual acuity,the best-corrected visual acuity,the degree and axis of astigmatism were compared between two groups at postoperative 1 month,3 months and 6 months.Results In experimental group,static iris recognition detected that eye cyclotorsional misalignment was 2.74°±2.05°,dynamic iris recognition detected that the intraoperative cyclotorsional misalignment

  9. Correção do astigmatismo irregular com lente intraocular tórica em um paciente com catarata e degeneração marginal pelúcida: relato de caso Toric intraocular lens implantation for cataract and irregular astigmatism related to pellucid marginal degeneration: case report

    Directory of Open Access Journals (Sweden)

    Ana Luiza Biancardi

    2012-12-01

    Full Text Available A degeneração marginal pelúcida (DMP é uma rara ectasia corneana cuja progressão resulta em astigmatismo irregular e baixa visual não corrigidos com óculos ou lentes de contato. O presente relato descreve um paciente com catarata e DMP que foi tratado com facoemulsificação e implante de lente intraocular tórica com recuperação da acuidade visual em ambos os olhos.Pellucid marginal degeneration (PMD is a rare corneal ectasia and its progression leads to irregular astigmatism and low vision that can not have spectacles or contact lens correction. This report describes a patient with low vision due to cataract and PMD that was treated with phacoemulsification and implantation of a toric intraocular lens with a satisfactory visual acuity outcome.

  10. 光学诱导散光对视觉信号传导及皮层反应的影响%Electrophysiological research on the effects of optic-induced astigmatism on transmission time and response intensity of visual signals in the visual cortex

    Institute of Scientific and Technical Information of China (English)

    解来青; 徐国旭; 赵堪兴

    2012-01-01

    Objective To evaluate the contribution of different degrees of astigmatism on the latency and amplitude of pattern visual evoked potentials (PVEPs).The effect of astigmatism on the transmission and response intensity of visual signals in the visual cortex was evaluated.Methods It was a random designed study.PVEPs were measured in subjects with normal or normal corrected visual acuity using a checkerboard pattern stimulus under varying conditions using different astigmatic trial lens powers in succession (0-5 D).Paired samples t test,analysis of variance and Pearson correlation was performed.Results When a lower spatial frequency (60' checkerboards stimulus) was used,there was little change in the latency of P100 (F=0.290,P>0.05).However,when a higher spatial frequency (15' checkerboards stimulus) was used,VEP latency increased with a greater degree of astigmatism (F=10.850,P<0.01; r=0.647,P<0.01).There was a gradual reduction of amplitudes of P100 as convex cylindrical lens power increased (when 60' checkerboards were used, F=3.947,P<0.01; r=-0.470,P<0.01; when 15' checkerboards were used,F=14.280,P<0.01; r=-0.699,P<0.01).Conclusion The transmission of visual signals depends on the quality of the visual image formed on the retina.Visual signal transmission time and response intensity in the visual cortex are affected not only by the defocus of the retinal image but also by the spatial frequency of the pattern stimulus.With a high spatial frequency,the transmission of visual signals is faster and the response intensity of the visual cortex is greater if the visual image formed on the retina is clear.%目的 研究光学诱导不同程度散光产生的视觉信号对皮层反应时间及强度的影响;研究散光是否可导致视觉信号传导时程异常,观察视觉信号传导时间及视皮层反应强度与散光程度的量化关系.方法 完全随机设计研究.对视力或矫正视力正常的被检者眼前依次放置0~5 D度数正

  11. 有晶状体眼后房型人工晶状体植入矫正高度近视及散光疗效观察%Preliminary observation of the effect of Posterior chamber phakic intraocular lens for high myopia with or without astigmatism

    Institute of Scientific and Technical Information of China (English)

    唐晓蕾; 王晓莉; 赵媛; 曾涛; 夏敏; 邱丹

    2015-01-01

    目的 探讨有晶状体眼后房型人工晶状体植入矫正高度近视及散光的临床应用价值.方法 纳入2010年3月至2013年1月间14例(25只眼)高度近视及散光患者,其中男6例,女8例,年龄18~42岁,平均26.7岁.所有患者接受有晶状体眼后房型人工晶状体植人治疗,术后随访3个月,检查裸眼视力、最佳矫正视力、屈光度、散光度,并在裂隙灯下检查拱高和轴向移位等.结果 所有患者术后裸眼视力较术前提高,术后3个月均达到或超过术前最佳矫正视力.术前等效球镜为-7.00~-22.0D,平均-(12.52±2.50)D,术后等效球镜为-0.25~-0.75 D,平均-(0.54±0.11)D,术后屈光度较术前明显降低,差异有统计学意义(P<0.05).散光由术前-(1.83±1.12)D下降至术后-(0.55±0.21)D,差异有统计学意义(P<0.05).手术前后眼压、角膜内皮细胞密度差异无统计学意义(P>0.05).术后无拱高偏大者,1只眼拱高偏低.术后93.75% (15/16)的TICL患者轴向偏转<10°.结论 有晶状体眼后房型人工晶状体植入术矫正高度近视及散光可以获得良好的裸眼视力,为高度近视患者提供一种新的选择,但其长期稳定性及远期并发症需要进一步观察.%Objective To investigate the efficacy and safety of the implantation of posterior chamber phakic intraocular lens (ICL) for high myopia with or without astigmatism.Methods From March 2010 to January 2013,14 high myopia patients (25 eyes) with or without astigmatism including 6 males and 8 females were admitted to our department.The average age of these patients was 26.7 years old,ranging from 18 to 42.All of them were treated by implantation of posterior chamber phakic ICL.Vision and diopter,as well as the results of slit lamp examination were used to evaluate the efficacy during the follow up.Results All patients were implanted ICL successfully and adhered to follow-up.The uncorrected visual acuity of every eye after surgery had improved,same or

  12. 虹膜定位波前引导的LASIK与标准LASIK比较治疗近视散光疗效的Meta分析%Iris-Registration in Wavefront-Guided LASIK versus Conventional LASIK for Correction of Myopia and Myopic Astigmatism: A Meta-Analysis

    Institute of Scientific and Technical Information of China (English)

    李岩; 成拾明; 周霞; 许玲

    2013-01-01

    Objective To systematically evaluate the efficacy and safety of iris-registration in wavefront-guided LASIK (IR+WG LASIK) versus conventional LASIK for correction of myopia accompanied with astigmatism. Methods Such databases as PubMed, EMbase, The Cochrane library (Issue 2, 2012), CBM, CNKI, VIP, and WangFang Data were searched to collect the randomized controlled trials (RCTs) and quasi-RCTs about IR+WG LASIK versus conventional LASIK for correction of myopia accompanied with astigmatism. The retrieval time was from inception to February 2012, and the language was in both Chinese and English. Two reviewers independently screened the literature, extracted the data and assessed the quality of the included studies. Then the meta-analysis was performed by using RevMan 5.1 software. Results A total of 9 studies involving 3 903 eyes were included. The results of meta-analysis showed that, compared with the conventional LASIK group, the IR+WG LASIK group had a higher ratio in patients with postoperative un-corrected visual acuity no less than 1.0 (RR=1.03, 95%CI 1.01 to 1.05, P=0.002), as well as in patients with best-corrected visual acuity gained over 1 line (RR=1.75, 95%CI 1.49 to 2.16, P<0.000 01); it was smaller in the postoperative high order aberration RMS (WMD=-0.16, 95%CI -0.21 to -0.11, P<0.000 01), coma-like RMS (WMD=-0.05, 95%CI -0.11 to 0.00, P=0.07), spherical-like RMS (WMD=-0.15, 95%CI -0.23 to -0.07, P=0.000 2), and residual astigmatism (WMD=0.14, 95%CI 0.10 to 0.18, P<0.000 01); moreover, it was lower in the incidence of postoperative glare (RR=0.27, 95%CI 0.15 to 0.50, P<0.000 1), and it was higher in the subjective satisfaction of patients (RR=1.08, 95%CI 1.04 to 1.13, P=0.000 3). Conclusion Compared with conventional LASIK, IR+WG LASIK can more effectively reduce astigmatism, postoperative high order aberration RMS and spherical-like RMS. It can also get visual function including uncorrected visual acuity and best-corrected visual acuity

  13. 经上皮准分子激光角膜切削术治疗不规则角膜散光的视觉质量观察%An evaluation of visual performance after trans-epithelial photorefractive keratectomy for correcting irregular corneal astigmatism

    Institute of Scientific and Technical Information of China (English)

    刘静; 陈世豪; 王一博; 张佳; 汪凌; 许琛琛; 王勤美

    2014-01-01

    Objective To evaluate visual performance pre-and postoperatively in patients with irregular corneal astigmatism who were treated with topography-guided trans-epithelial photorefractive keratectomy (TPRK).Methods This non-randomized prospective clinical study was comprised of 15 eyes of 12 patients with irregular corneal astigmatism who were treated with topography-guided TPRK.The data included UCVA,BCVA,pre-and postoperative refractive data,and contrast sensitivity before surgery and at 1 and 3 months after surgery,the corneal epithelial timeline for healing,pain scores at 3 and 7 days after surgery,the classification of haze when it appeared,and the safety and efficacy indexes.Repeated measures analysis of variance was used to compare the changes over time.Results Mean UCVA increased from 4.11±0.28 preoperatively to 4.88±0.16 3 months postoperatively (F=36.706,P<0.05).Mean BSCVA increased from 4.86±0.08 to 4.98±0.09 (F=5.075,P<0.05),with no visual acuity lines lost.Safety and efficacy indexes were 1.025 and 1.004,respectively.Mean spherical equivalent (SE) was reduced from-3.73±4.62 D to-0.03±0.09 D (F=-4.034,P<0.05),and the mean cylinder was reduced from-1.71±1.43 D to +0.38±1.14 D (F=-9.192,P<0.05).Tbere were significant differences in contrast sensitivity were found between patients at 3,6,12 c/d spatial frequencies before surgery and 1 month after surgery (P>0.05).But patients at 3 months after surgery showed better contrast sensitivity than patients before surgery (P<0.05).Haze appeared in 2 eyes at 1 month postoperatively but recovered by 3 months postoperatively.Conclusion Topography-guided TPRK appears to be an effective treatment for irregular corneal astigmatism.The operation improves contrast sensitivity and visual performance in patients with irregular corneal astigmatism.%目的 观察对不规则角膜散光患者施行角膜地形图引导的经上皮准分子激光角膜切削术后患者视觉质量的改善情况.方法 非

  14. 矢量分析法比较近视伴较高散光青少年配戴球面和环曲面角膜塑形镜后的临床疗效%The use of vector analysis to evaluate the changes in corneal astigmatism with general and toric orthokeratology lenses

    Institute of Scientific and Technical Information of China (English)

    常枫; 沈政伟; 陈云辉; 魏润菁; 李梅; 周萍; 周和政

    2016-01-01

    Objective To use vector analysis to evaluate the effectiveness of general and toric orthokeratology lenses for changes in corneal astigmatism in myopic children with moderate-to-high astigmatism.Methods This was a prospective study.Fourteen patients,27 eyes (Spherical group),were fitted with spherical orthokeratology lenses and 10 patients,20 eyes (Toric group),were fitted with toric orthokeratology lenses.Data collection was performed 1 day,1week,1 month,3 months after orthokeratology fitted and included visual acuity,corneal topography,axial length and biomicroscopy examinations.Changes in corneal toricity were evaluated using vector analysis.Data were compared between the two groups using independent t test.Results The median subjective myopia of Spherical group and Toric group at base line was-3.80±1.43 D and-3.98±1.53 D (P>0.05).The corneal J0 vector values were-1.11±0.23 D and-1.18±0.29 D (P>0.05) and the J45 vector values were 0.11± 0.21 D and 0.05±0.51 D (P>0.05),respectively.After wearing orthokeratology lenses for 1 day,1 week,1 month and 3 months,the UCVAs improved steadily in both groups,the differences between the two groups were insignificant in 1 day,1 week,1 month,but with significant difference in 3 months (4.93±0.05 vs.5.05±0.06).The differences of corneal J0 vector values between the two groups were significant for all the time ponits (t=-4.83,-1.56,-2.38,-1.03,P<0.05).The differences of corneal J45 vector values between the two groups were insignificant.There were 4 and zero patients in Spherical group and Toric group who reported visual disturbance symptoms.Conclusion Both spherical and toric orthokeratology lenses can improve UCVA in myopic children with moderate-to-high astigmatism.However,the toric design can be effective for improving contact lens fitting and enhancing the effect of corneal reshaping.%目的 矢量分析法比较近视伴较高散光的青少年儿童患者分别配戴球面角膜塑形镜和环曲面角膜

  15. 单眼角膜散光白内障患者不同人工晶状体组合植入的对比研究%Comparison of different combinations of intraocular lenses implantation in cataract patients with unilateral astigmatism

    Institute of Scientific and Technical Information of China (English)

    田芳; 张红; 胡尊霞

    2011-01-01

    Objective To assess binocular visual function after combined implantation of toric and multifocal or monofocal intraocular lenses in unilateral astigmatism cataract patients. Methods This was a prospective case control study. A total of thirty unilateral astigmatism patients undergoing phacoemulsification were recruited. AcrySof Toric IOL were implanted in the astigmatic eye of patients, with ReSTOR (15 eyes) or AcrySof IQ (15 eyes) in the contralateral eye. Six months postoperatively, patients were assessed for visual acuity (5.0 m, 60.0 cm, 40.0 cm), contrast sensitivity, amplitude of accommodation, and stereoacuity. Patients were surveyed for visual disturbances and lifestyle visual quality. Data were analyzed with a paired t test, an independent samples t test, or chi-square test. Results At 6 months postoperatively, for Toric-ReSTOR patients, uncorrected binocular logMAR visual acuity at 5.0 m, 60.0 cm, 40.0 cm was 0.05±0.05, 0.24±0.10, and 0.14±0.06, respectively. For Toric-AcrySof IQ patients, uncorrected binocular logMAR visual acuity was 0.06±0.07, 0.26±0.08, and 0.37 ±0.10, respectively. These values between the two group did not achieve significant differences except for near visual acuity (t=5.476, P=0.000). The contrast sensitivity for ReSTOR eyes was lower at 18 cpd under photopic and photopic glare circumstance than for the AcrySof IQ eyes (0.30 ± 0.37 versus 0.94 ±0.58, t=3.476, P=0.001; 0.34 ± 0.44 versus 0.88 ±0.52, t =2.975, P= 0.006). And was lower at 12 cpd under scotopic and scotopic glare circumstance than for the AcrySof IQ eyes (0.05±0.22 versus 0.50±0.61, t=3.057, P=0.005; 0.05±0.22 versus 0.59±0.75, t=3.154, P=0.004). The amplitude curve of accommodation in Toric-ReSTOR patients had two wave peak (0 and-2.5 D), but only one (0 D) in Toric-AcrySof IQ patients. The stereopsis of Toric-ReSTOR eyes decreased slightly (53% versus 73%, x2=1.262, P=0.263). Patient satisfaction for mean near vision was significantly different: 80

  16. Visual Performance in Moderate to Severe Astigmatism : Rigid Gas-permeable Contact Lenses versus Spectacles%透气性硬性接触镜和框架眼镜矫正中高度散光视觉质量的比较

    Institute of Scientific and Technical Information of China (English)

    王雪; 马薇; 杨必; 刘陇黔

    2012-01-01

    Objective To explore whether spectacles or rigid gas-permeable (RGP) contact lenses provide better visual performance for moderate to severe astigmatism. Methods Between June 2008 and May 2011, 20 individuals (40 eyes) were fitted with both RGP lenses and spectacles. They first underwent corneal topography and refractometry, then were fitted with RGP trial lenses and lastly fitted with RGP lenses. When regularly followed up, the corrected visual acuity, wearing condition and eye health were evaluated respectively. For each type of lens, contrast visual acuity was evaluated. Each subject was asked to select the lens type of choice and to rate quality of vision in day-to-day activities through a questionnaire. Results The corrected visual acuity with RGP lenses was better than that with spectacles. But there was no difference in contrast visual acuity in all spatial frequency. Subjectively, there was no difference in vision, but most of the subjects prefer the computer-visual acuity and reading-visual acuity corrected by spectacles. About 40% of patients choose RGP contact lens as the main corrected method, and 45% of patients preferred using RGP lenses and spectacles alternately. About 10% of patients only wear RGP lenses when it was necessary. Two patients dropped out. Conclusions Both RGP lenses and spectacles leads to good results in correcting moderate to severe astigmatism. Though spectacles get higher scores in near vision, because of the better visual performance and appearance offered by RGP contact lens, a majority of patients can insist on wearing it.%目的 比较中高度散光患者配戴框架眼镜和透气性硬性接触镜(RGPCL)的主客观视觉质量.方法 选取2008年6月-2011年5月中高度角膜散光20例共40只眼进行角膜地形图、综合验光仪验光等检查后,选择合适试戴片作配适评估并定制RGPCL.要求患者戴镜后1周、1个月、3个月和6个月复查,记录矫正视力、镜片配

  17. An Astigmatic Detection System for Polymeric Cantilever-based Sensors

    DEFF Research Database (Denmark)

    Hwu, En-Te; Liao, Hsien-Shun; Bosco, Filippo;

    2012-01-01

    fluctuation measurements on cantilever beams with a subnanometer resolution. Furthermore, an external excitation can intensify the resonance amplitude, enhancing the signal- to-noise ratio. The full width at half maximum (FWHM) of the laser spot is 568 nm, which facilitates read-out on potentially...... submicrometer-sized cantilevers. The resonant frequency of SU-8 microcantilevers is measured by both thermal fluctuation and excited vibration measurement modes of the ADS....

  18. 角膜塑形镜矫治青少年近视散光的疗效及对角膜内皮细胞的影响%Clinical effect of orthokeratology for juvenile with myopia astigmatism and its effects on corneal endothelial cells

    Institute of Scientific and Technical Information of China (English)

    周籽秀; 徐珊珊; 易省平

    2016-01-01

    Abstract?AIM:To investigate the clinical effect of orthokeratology for 400 juvenile with myopia astigmatism and its effects on corneal endothelial cells.?METHODS:Four hundred patients(800 eyes), of whom the average age was 11.5 ±2.3 years old, 239 male, 161 female, were divided into two groups: orthokeratology group and spectacles group. Parameters including efficacy data ( uncorrected visual acuity, corneal curvature, axial length and diopter ) and corneal endothelial cell data ( count of endothelial cell, endothelial cell density, fluorescein staining and central corneal thickness) were observed at 1d, 1, 6, 12 and 24mo after wearing.? RESULTS: The visual acuity of spectacles group recovered to normal after wearing, that of orthokeratology group recovered to normal at 1mo after wearing.At 2a after wearing, the corneal curvature, diopter of orthokeratology group decreased significantly (40.09 ±0.31D, 0.23 ±0.06D respectively); while those of spectacles group increased, the differences between the two groups were significant (P0.05 ) compared to those before wearing. At 2a after wearing, the axial length of the two groups were 23.96 ± 0.38mm, 26.49±0.88mm respectively (P0.05).The count of endothelial cell and endothelial cell density both decreased after wearing without significant differences (P>0.05).?CONCLUSION: Orthokeratology has less effect on the corneal endothelial cells, no obvious adverse reactions and can control the prognosis of myopia.%目的:探讨角膜塑形镜矫正青少年近视的临床效果及对角膜内皮细胞的影响。方法:随机在我院选择400例800眼明确诊断为近视的青少年患者,平均年龄为11.5±2.3岁,其中男239例,女161例,根据治疗方法随机分为角膜塑形组和框架眼镜组,分别为167例334眼和233例466眼,本试验所研究的数据包括:(1)疗效:裸眼视力、角膜曲率、眼轴长度、屈光度等;(2)角膜内皮细胞:角膜内皮细胞计数

  19. Comparative clinical study of wavefront-guided laser in situ keratomileusis with versus without iris recognition for myopia or myopic astigmatism%有和无虹膜识别波阵面像差引导的准分子激光原位角膜磨镶术治疗近视或近视散光眼临床对比研究

    Institute of Scientific and Technical Information of China (English)

    王卫群; 张金嵩; 赵晓金

    2011-01-01

    Objective To explore the postoperative visual acuity results of wavefront-guided LASIK with iris recognition for myopia or myopic astigmatism and the changes of higher-order aberrations and contrast sensitivity function (CSF).Methods Series of prospective case studies,158 eyes ( 85 cases) of myopia or myopic astigmatism were divided into two groups:one group underwent wavefront-guided LASIK with iris recognition ( iris recognition group) ; another group underwent wavefront-guided LASIK treatment without iris recognition through the limbus mating point ( non-iris recognition group).To comparative analyze the postoperative visual acuity,residual refraction,the RMS of higher-order aberrations and CSF of two groups.Results There was no statistical significance difference between two groups of the average uncorrected visual acuity( t =0.039,0.058,0.898; P =0.844,0.810,0.343 ),best corrected visual acuity ( t =0.320,0.440,1.515 ; P =0.572,0.507,0.218 ),and residual refraction [ spherical equivalent ( t =0.027,0.215,0.238; P =0.869,0.643,0.626),spherical (t =0.145,0.117,0.038; P =0.704,0.732,0.845) and cylinder( t =1.676,1.936,0.334; P =0.195,0.164,0.563 ) ] at postoperative 10 days,1 month and 3 month.The security index of iris recognition group at postoperative 3 month was 1.06 and non- iris recognition group was 1.03 ; the efficacy index of iris recognition group is 1.01 and non-iris recognition group was 1.00.Postoperative 3 month iris recognition group 93.83% eyes and non-iris recognition group of 90.91% eyes spherical equivalent within ± 0.50 D ( x2 =0.479,P =0.489 ),iris recognition group of 98.77% eyes and non-iris recognition group of 97.40% eyes spherical equivalent within ± 1.00 D( Fisher test,P =0.613).There was no significance difference between the two groups of security,efficacy and predictability.Non-iris recognition group postoperative 1 month and postoperative 3 months 3-order order aberrations root mean square value (RMS) higher than the iris

  20. Quantifying Assessments of Vision Improvements for Myopes, Hypermetropes, Presbyopes, and Astigmats, in Brazil and Elsewhere.

    Science.gov (United States)

    Lopes, Demetriou; D. M., D.; Niemi, Paul N.; D., O.; Mc Leod, Roger D.

    2007-10-01

    Vision can safely, rapidly, and significantly be improved among nearsighted, far-sighted, presbyopic, and astigmatatic individuals, using methods developed for Mc Leod's patent-pending Naturoptics. We hope to calibrate and apply the method in South America, particularly Brazil, using metric standards accessible from ordinary vision assessment charts as used there. This precursor for extension into Hispanic-speaking areas, especially Chile, Guatemala, Honduras, Mexico, Paraguay, Peru, and Puerto Rico, is to establish property-rights protected licensed teaching agreements. Initially, visually impaired potential students of to-be-established not-for-profit Naturopathic medical, surgical, dental, law, science, and arts schools, perhaps named Metocantins or Metaquaratinga University, if in Brazil, will learn to correct their vision; training and licensing them can provide earnings for the self-funding of all associated activities and expenses. We will publish established results that refute claims relating to vision. Mc Leod's spatial Fourier transform model for retinal focal surface electric field amplitude vision explains all phenomena and Land's two-wavelength interval color vision results.

  1. CLINICAL ANALYSIS OF EXCIMER LASER PHOTOREFRACTIVE KERATECTOMY FOR TREATMENT OF MYOPIA AND MYOPIC ASTIGMATISM

    Institute of Scientific and Technical Information of China (English)

    张华; 郭绒霞; 孙乃学; 王峰; 张道过; 王彤; 孙健; 杨振国

    1999-01-01

    In1983,Trokeletal〔1〕firstreportedthelaboratoryreasearchaboutexcimerlaser.Clinicalusingofexcimerlaserpho-torefractivekeratecto...

  2. Visual outcomes of conductive keratoplasty to treat hyperopia and astigmatism after laser in situ keratomileusis and photorefractive keratectomy

    Directory of Open Access Journals (Sweden)

    Alireza Habibollahi

    2011-01-01

    Conclusions : CK is a predictable and reliable method to correct hyperopia after LASIK and PRK, however cylinder correction may induce irregular and unpredictable outcomes and a modified nomogram is required for further studies.

  3. Three-dimensional super-resolution imaging of the midplane protein FtsZ in live Caulobacter crescentus cells using astigmatism.

    Science.gov (United States)

    Biteen, Julie S; Goley, Erin D; Shapiro, Lucy; Moerner, W E

    2012-03-01

    Single-molecule super-resolution imaging provides a non-invasive method for nanometer-scale imaging and is ideally suited to investigations of quasi-static structures within live cells. Here, we extend the ability to image subcellular features within bacteria cells to three dimensions based on the introduction of a cylindrical lens in the imaging pathway. We investigate the midplane protein FtsZ in Caulobacter crescentus with super-resolution imaging based on fluorescent-protein photoswitching and the natural polymerization/depolymerization dynamics of FtsZ associated with the Z-ring. We quantify these dynamics and determine the FtsZ depolymerization time to be divisional stage.

  4. Astigmatic mites from nests of birds of prey in the U.S.A. : IV. Description of the life-cycle of Acotyledon paradoxa Oudemans, 1903

    NARCIS (Netherlands)

    Fain, A.; Philips, J.R.

    1978-01-01

    INTRODUCTION In this paper we describe for the first time the life-cycle of Acotyledon paradoxα Oudemans, 1903. This species was known, so far, only from the hypopial stage and a protonymph. The discovery of the adults allows us to precise the systematic position of the genus Acotyledon and to throw

  5. Laser resonators with several mirrors and lenses with the bow-tie laser resonator with compensation for astigmatism and thermal lens enects as an example

    DEFF Research Database (Denmark)

    Abitan, Haim; Skettrup, Torben

    2005-01-01

    Laser resonators with several mirrors (lenses) have been investigated in a systematic fashion. They have been grouped into classes according to their number n of mirrors/lenses. Stability polynomials, beam waist radii and locations have been obtained for each group up to n = 4. The bow-tie laser...

  6. Phakic posterior chamber intraocular lens combined with astigmatic keratotomy for high myopia with astigmatism%有晶状体眼后房型人工晶状体植入联合AK术治疗高度近视及散光的临床疗效

    Institute of Scientific and Technical Information of China (English)

    朱双倩; 俞阿勇; 薛安全; 王树林; 包芳军; 王勤美

    2009-01-01

    目的 研究有晶状体眼后房型人工晶状体(ICL)联合角膜松解术(AK)治疗高度近视及散光的安全性、有效性、预测性.方法 对21例(34眼)高度近视患者行有晶状体眼ICL植入术,对其中20眼散光度数≥1.5D的联合AK术.观察术前及术后1、3、6个月的裸眼视力、最佳矫正视力、屈光度、眼压、内皮细胞密度等.结果 所有患者成功植入ICL,手术前后等效球镜分别为(-13.5±2.2)、(-0.30±0.84)、(-0.28±0.86)、(-0.28±0.84)D;术后裸眼视力分别为4.80±0.16、4.81±0.17、4.82±0.17;手术前后最佳矫正视力分别为4.74±0.26、4.86±0.17、4.87±0.17、4.9±0.18,差异有统计学意义(P<0.01);内皮细胞密度术前为(2871±256)个/mm2,术后为(2773±267)个/mm2,差异有统计学意义(P<0.01);行AK术眼术前后散光分别为(-2.31±0.64)、(-1.22±0.57)、(-1.02±0.40)、(-0.93±0.39)D,差异有统计学意义(P<0.01).结论 有晶状体眼ICL联合AK术治疗高度近视及散光有较好的安全性、有效性、预测性,长期疗效有待进一步观察.

  7. 新型人工晶体推送器对白内障术后角膜散光影响的临床研究%Clinical study on the effect of new type intraocular lens unfolder on postoperative astigmatism

    Institute of Scientific and Technical Information of China (English)

    汤欣; 杨瑞波; 孙慧敏

    2004-01-01

    目的:评价2.6mm口径的新型人工晶体推送器(Emerald T推送器)对白内障超声乳化人工晶体植入术后角膜散光的影响.方法:将160例(160眼)老年性白内障患者随机分为两组:A组为2.6mm口径的Emerald T人工晶体推送器组;B组为3.2mm口径的Sapphire人工晶体推送器组.所有患者均行经透明角膜超声乳化人工晶体植入术,术后1周、1月、3月采用角膜地形图仪比较两组角膜散光的变化情况.结果:A、B两组术后1周、1月、3月平均手术源性角膜散光(D)分别为:0.36 0.20、0.33 0.23、0.31 0.22;0.78 0.61、0.69 0.58、0.58 0.44;两组间差别有统计学意义(P<0.05).术后1周及1月,A、B两组裸眼视力≥0.5者分别为:74眼(92.50%)、77眼(96.25%);62眼(77.50%)、70眼(87.50%),两组间差别有统计学意义(P<0.05),术后3月两组裸眼视力≥0.5者分别为:77眼(96.25%)、73眼(91.25%),两组间差别无统计学意义(P>0.05).结论:2.6mm口径的Emerald T人工晶体推送器所需手术切口小、术后散光小、视力恢复快且稳定,是目前较为理想的小切口人工晶体植入装置.

  8. The experimental investigation of orbital angular momentum of complex astigmatic elliptical beams%复杂像散椭圆光束的轨道角动量的实验研究

    Institute of Scientific and Technical Information of China (English)

    董一鸣; 徐云飞; 张璋; 林强

    2006-01-01

    提出一种直接测量光束的轨道角动量的方法,其原理是把具有轨道角动量的光束照射到一个金属靶上,使其在光束的角动量作用下发生转动.通过测量靶转动的角度来计算光束的角动量值.对几种不同参数的光束的轨道角动量进行了测量,获得了轨道角动量与光束参数之间的关系,实验结果与理论分析较好地符合.

  9. Long-Term Comparison of Posterior Chamber Phakic Intraocular Lens With and Without a Central Hole (Hole ICL and Conventional ICL) Implantation for Moderate to High Myopia and Myopic Astigmatism

    Science.gov (United States)

    Shimizu, Kimiya; Kamiya, Kazutaka; Igarashi, Akihito; Kobashi, Hidenaga

    2016-01-01

    Abstract The study shows a promising next-generation surgical option for the correction of moderate to high ametropia. Hole implantable collamer lens (ICL), STAAR Surgical, is a posterior chamber phakic intraocular lens with a central artificial hole. As yet, however, no long-term comparison of the clinical results of the implantation of ICLs with and without such a hole has hitherto been conducted. A prospective, randomized, controlled trial was carried out in order to compare the long-term clinical outcomes of the implantation, in such eyes, of ICLs with and without a central artificial hole. Examinations were conducted of the 64 eyes of 32 consecutive patients with spherical equivalents of −7.53 ± 2.39 diopters (D) (mean ± standard deviation) in whom implantation of a Hole ICL was performed in 1 eye, and that of a conventional ICL was carried out in the other, by randomized assignment. Before 1, 3, and 6 months, and 1, 3, and 5 years after surgery, the safety, efficacy, predictability, stability, intraocular pressure, endothelial cell density, and adverse events of the 2 surgical techniques were assessed and compared over time. The measurements of LogMAR uncorrected and corrected distance visual acuity 5 years postoperatively were −0.17 ± 0.14 and −0.24 ± 0.08 in the Hole ICL group, and −0.16 ± 0.10 and −0.25 ± 0.08 in the conventional ICL group. In these 2 groups, 96% and 100% of eyes, respectively, were within 1.0 D of the targeted correction 5 years postoperatively. Manifest refraction changed by −0.17 ± 0.41 D and −0.10 ± 0.26 D occurred in from 1 month to 5 years in the Hole and conventional ICL groups, respectively. Only 1 eye (3.1%), which was in the conventional ICL group, developed an asymptomatic anterior subcapsular cataract. Both Hole and conventional ICLs corrected of ametropia successfully throughout the 5-year observation period. It appears likely that the presence of the central hole does not significantly affect these visual and refractive outcomes. Trial Registration: UMIN000018771. PMID:27057883

  10. 有晶状体眼前房型环曲面人工晶状体植入矫正散光%Artisan toric phakic intraocular lens for the correction of astigmatism

    Institute of Scientific and Technical Information of China (English)

    涂云海; 俞阿勇; 高潮

    2007-01-01

    散光的矫治一直是屈光手术的焦点,有晶状体眼前房型环曲面人工晶状体(Artisan toric phakic intraocular lens,TPIOL)矫正散光,以其矫治范围大、安全、有效,逐渐受到临床关注.本文就Artisan TPIOL的物理特征、手术患者的筛选、术前准备、手术方法,以及对其术后安全性、有效性、准确性、稳定性、最小损害等评价作一综述.

  11. Corneal relaxing incision combined with phacoemulsification and IOL implantation

    Institute of Scientific and Technical Information of China (English)

    沈晔; 童剑萍; 李毓敏

    2004-01-01

    Objective: To analyze the effectiveness and safety of corneal relaxing incisions (CRI) in correcting keratometric astigmatism during cataract surgery. Methods: A prospective study of two groups: control group and treatment group. A treatment group included 25 eyes of 25 patients who had combined clear corneal phacoemulsification, IOL implantation and CRI. A control group included 25 eyes of 25 patients who had clear corneal phacoemulsification and IOL implantation.Postoperative keratometric astigmatism was measured at 1 week, 1 month, 3 months and 6 months. Results: CRI significantly decreased keratometric astigmatism in patients with preexisting astigmatism compared with astigmatic changes in the control group. In eyes with CRI, the mean keratometric astigmatism was 0.29±0.17 D (range 0 to 0.5 D) at 1 week, 0.41±0.21 D (range 0 to 0.82 D) at 1 month, respectively reduced by 2.42 D and 2.30 D at 1 week and 1 month postoperatively (P=0.000, P=0.000), and postoperative astigmatism was stable until 6 months follow-up. The keratometric astigmatism of all patients decreased to less than 1.00 D postoperatively. Conclusions: CRI is a practical, simple, safe and effective method to reduce preexisting astigmatism during cataract surgery. A modified nomogram is proposed. The long-term effect of CRI should be investigated.

  12. Corneal relaxing incision combined with phacoemulsification and IOL implantation

    Institute of Scientific and Technical Information of China (English)

    沈晔; 童剑萍; 李毓敏

    2004-01-01

    Objective: To analyze the effectiveness and safety of corneal relaxing incisions (CRI) in correcting keratometric astigmatism during cataract surgery. Methods: A prospective study of two groups: control group and treatment group. A treatment group included 25 eyes of 25 patients who had combined clear corneal phacoemulsification, IOL implantation and CRI. A control group included 25 eyes of 25 patients who had clear corneal phacoemulsification and IOL implantation.Postoperative keratometric astigmatism was measured at 1 week, 1 month, 3 months and 6 months. Results: CRI signifi-cantly decreased keratometric astigmatism in patients with preexisting astigmatism compared with astigmatic changes in the control group. In eyes with CRI, the mean keratometric astigmatism was 0.29±0.17 D(range 0 to 0.5 D) at 1 week, 0.41±0.21 D (range 0 to 0.82 D) at 1 month, respectively reduced by 2.42 D and 2.30 D at 1 week and 1 month postoperatively (P=0.000, P=0.000), and postoperative astigmatism was stable until 6 months follow-up. The keratometric astigmatism of all patients decreased to less than 1.00 D postoperatively. Conclusions: CRI is a practical, simple, safe and effective method to reduce preexisting astigmatism during cataract surgery. A modified nomogram is proposed. The long-term effect of CRI should be investigated.

  13. Small-incision lenticule extraction (SMILE)

    DEFF Research Database (Denmark)

    Hansen, Rasmus Søgaard; Lyhne, Niels; Grauslund, Jakob;

    2016-01-01

    PURPOSE: To study the outcomes of small-incision lenticule extraction (SMILE) for treatment of myopia and myopic astigmatism. METHODS: Retrospective study of patients treated for myopia or myopic astigmatism with SMILE, using a VisuMax(®) femtosecond laser (Carl Zeiss Meditec, Jena, Germany......), at the Department of Ophthalmology, Odense University Hospital, Odense, Denmark. Inclusion criteria were corrected distance visual acuity (CDVA) of 20/25 or better before surgery and no ocular conditions other than myopia up to -10.00 diopters (D) with astigmatism up to 3.00 D. RESULTS: Of the 729 treatments, 722...... predictable, efficient, and safe for treatment of myopia and myopic astigmatism....

  14. 晶状体眼后房型人工晶状体/散光性后房型人工晶状体术矫正高度近视的临床观察%Clinical observation of implantation of posterior chamber intraocular lens/astigmatism posterior chamber intraocular lens for patients with high myopia

    Institute of Scientific and Technical Information of China (English)

    杨吟; 刘治容; 陈斌; 陈波; 杨萍; 吴峥峥

    2014-01-01

    目的 研究晶状体眼后房型人工晶状体(implantable contact lens,ICL)/散光性后房型人工晶状体(TICL)植入术矫正高度近视的有效性及安全性.方法 收集在我院行IC[/TICL植入术的患者77例(153只眼),在术后第1天、1周、1月、3月和6月时行视力、裂隙灯显微镜、眼底镜和眼压检查,术后1个月加做客观检影验光.对比术前最佳矫正视力及术后裸眼视力的差异.结果 153只眼均成功植入了ICL/TICL,术后144只眼(94.12%)未发现明显的并发症.术后1周时,153眼的裸眼视力为0.83±0.15,术前矫正视力与术后裸眼视力比较差异无统计学意义(P>0.05).结论 ICL/TICL植入手术治疗高度/超高度近视,是目前对于该类患者有效且安全的治疗方案.

  15. Comparison of the curative effect between IR-LASIK and LASIK in high astigmatism treatment%高度散光患者虹膜定位波前引导的LASIK与常规LASIK手术疗效的比较

    Institute of Scientific and Technical Information of China (English)

    李耀宇; 翟国光; 邱岩; 邸玉兰; 屈哲; 黄耀辉

    2008-01-01

    目的:比较高度散光患者虹膜定位波前引导的LASIK(IR-LASIK)手术与常规LASIK手术的临床效果.方法:≥2.0DC的高度散光患者分别使用VISX S4-IR准分子激光机进行IR-LASIK手术(204例338眼)和常规LASIK手术(180例335眼),对术后裸眼视力和残留散光度数进行比较,IR手术组检查了眼球旋转的角度.结果:IR-LASIK手术组术后2d裸眼视力(≥1.0者89.1%)明显优于常规LASIK手术组(≥1.0者83.6%,P<0.05),术后残留散光度数也明显小于常规LASIK手术组(0.56DC vs1.15DC,P<0.01).IR-LASIK手术组波前像差检查的散光度数和轴位均与显然验光结果有一定的差别,所有患眼手术时均发生了眼球旋转.这可能是IR手术后疗效较好的重要原因.结论:IR-LASIK手术能够明显改善高度散光患者术后裸眼视力,减轻术后的散光残留.

  16. Comparison of designs of off-axis Gregorian telescopes for millimeter-wave large focal-plane arrays.

    Science.gov (United States)

    Hanany, Shaul; Marrone, Daniel P

    2002-08-01

    We compare the diffraction-limited field of view (FOV) provided by four types of off-axis Gregorian telescopes: the classical Gregorian, the aplanatic Gregorian, and the designs that cancel astigmatism and both astigmatism and coma. The analysis is carried out with telescope parameters that are appropriate for satellite and balloonborne millimeter- and submillimeter-wave astrophysics. We find that the design that cancels both coma and astigmatism provides the largest flat FOV, approximately 21 square deg. We also find that the FOV can be increased by approximately 15% by means of optimizing the shape and location of the focal surface.

  17. A comparison of designs of off-axis Gregorian telescopes for mm-wave large focal plane arrays

    CERN Document Server

    Hanany, S; Hanany, Shaul; Marrone, Daniel P.

    2002-01-01

    We compare the diffraction-limited field of view (FOV) provided by four types of off-axis Gregorian telescopes: the classical Gregorian, the aplanatic Gregorian, and designs that cancel astigmatism and both astigmatism and coma. The analysis is carried out using telescope parameters that are appropriate for satellite and balloon-borne millimeter and sub-millimeter wave astrophysics. We find that the design that cancels both coma and astigmatism provides the largest flat FOV, about 21 square degrees. We also find that the FOV can be increased by about 15% by optimizing the shape and location of the focal surface.

  18. Comparison of designs of off-axis Gregorian telescopes for millimeter-wave large focal-plane arrays.

    Science.gov (United States)

    Hanany, Shaul; Marrone, Daniel P

    2002-08-01

    We compare the diffraction-limited field of view (FOV) provided by four types of off-axis Gregorian telescopes: the classical Gregorian, the aplanatic Gregorian, and the designs that cancel astigmatism and both astigmatism and coma. The analysis is carried out with telescope parameters that are appropriate for satellite and balloonborne millimeter- and submillimeter-wave astrophysics. We find that the design that cancels both coma and astigmatism provides the largest flat FOV, approximately 21 square deg. We also find that the FOV can be increased by approximately 15% by means of optimizing the shape and location of the focal surface. PMID:12153101

  19. Eyelid Problems

    Science.gov (United States)

    ... in Action Medical Editor & Editorial Advisory Board Sponsors Sponsorship Opporunities Spread the Word Shop AAP Find a ... irregular shape (astigmatism), it will threaten normal vision development and must be corrected as early as possible. ...

  20. Light with a twist : ray aspects in singular wave and quantum optics

    NARCIS (Netherlands)

    Habraken, Steven Johannes Martinus

    2010-01-01

    Light may have a very rich spatial and spectral structure. We theoretically study the structure and physical properties of coherent optical modes and quantum states of light, focusing on optical vortices, general astigmatism, orbital angular momentum and rotating light.

  1. Contact Lens Visual Rehabilitation in Keratoconus and Corneal Keratoplasty

    Directory of Open Access Journals (Sweden)

    Yelda Ozkurt

    2012-01-01

    Full Text Available Keratoconus is the most common corneal distrophy. It’s a noninflammatory progressive thinning process that leads to conical ectasia of the cornea, causing high myopia and astigmatism. Many treatment choices include spectacle correction and contact lens wear, collagen cross linking, intracorneal ring segments implantation and finally keratoplasty. Contact lenses are commonly used to reduce astigmatism and increase vision. There are various types of lenses are available. We reviewed soft contact lenses, rigid gas permeable contact lenses, piggyback contact lenses, hybrid contact lenses and scleral-semiscleral contact lenses in keratoconus management. The surgical option is keratoplasty, but even after sutur removal, high astigmatism may stil exists. Therefore, contact lens is an adequate treatment option to correct astigmatism after keratoplasty.

  2. Modified Scleral Flap Incision to Reduce Corneal Astigmatisn after Intraocular Lens Implantation

    Institute of Scientific and Technical Information of China (English)

    YizhiLiu; ShaozhenLi

    1995-01-01

    Purpose:To investigate a simple method during extracapsular cataract extraction with posteior chamber intraocular lens implantation in order to reduce surgically induced corneal astig-matism.Methods:A modified scleral flap incision was used in the extracapsular cataract extraction with intraocular lens implantation and the postoperative changes in conreal astigmatism was observed.Results:The peak value of postoperative corneal astigmatism was3.60D,and the corneal astigmatism regression was 2.11D,surgically induced astigmatism was less significant in modified scleral flap incision group than that in convention-al limbal incison group(P<0.05).Conclusions:The modified scleral flap inciston is an ideal incision for cataract ex-traction with intraocular lens implantation when phacoemulsifier is not avaliable.Eye Science1995;11:136-139.

  3. Functional outcomes and patient satisfaction after laser in situ keratomileusis for correction of myopia.

    NARCIS (Netherlands)

    Tahzib, N.G.; Bootsma, S.J.; Eggink, F.A.G.J.; Nabar, V.A.; Nuijts, R.M.M.A.

    2005-01-01

    PURPOSE: To determine subjective patient satisfaction and self-perceived quality of vision after laser in situ keratomileusis (LASIK) to correct myopia and myopic astigmatism. SETTING: Department of Ophthalmology, Academic Hospital Maastricht, Maastricht, The Netherlands. METHODS: A validated questi

  4. Contact lens visual rehabilitation in keratoconus and corneal keratoplasty.

    Science.gov (United States)

    Ozkurt, Yelda; Atakan, Mehmet; Gencaga, Tugba; Akkaya, Sezen

    2012-01-01

    Keratoconus is the most common corneal distrophy. It's a noninflammatory progressive thinning process that leads to conical ectasia of the cornea, causing high myopia and astigmatism. Many treatment choices include spectacle correction and contact lens wear, collagen cross linking, intracorneal ring segments implantation and finally keratoplasty. Contact lenses are commonly used to reduce astigmatism and increase vision. There are various types of lenses are available. We reviewed soft contact lenses, rigid gas permeable contact lenses, piggyback contact lenses, hybrid contact lenses and scleral-semiscleral contact lenses in keratoconus management. The surgical option is keratoplasty, but even after sutur removal, high astigmatism may stil exists. Therefore, contact lens is an adequate treatment option to correct astigmatism after keratoplasty. PMID:22292112

  5. Line focusing for soft x-ray laser-plasma lasing

    OpenAIRE

    Bleiner, Davide; Balmer, Jürg; Staub, Felix

    2011-01-01

    A computational study of line-focus generation was done using a self-written ray-tracing code and compared to experimental data. Two line-focusing geometries were compared, i.e., either exploiting the sagittal astigmatism of a tilted spherical mirror or using the spherical aberration of an off-axis- illuminated spherical mirror. Line focusing by means of astigmatism or spherical aberration showed identical results as expected for the equivalence of the two frames of reference. The variation o...

  6. Contact Lens Visual Rehabilitation in Keratoconus and Corneal Keratoplasty

    OpenAIRE

    Yelda Ozkurt; Mehmet Atakan; Tugba Gencaga; Sezen Akkaya

    2012-01-01

    Keratoconus is the most common corneal distrophy. It's a noninflammatory progressive thinning process that leads to conical ectasia of the cornea, causing high myopia and astigmatism. Many treatment choices include spectacle correction and contact lens wear, collagen cross linking, intracorneal ring segments implantation and finally keratoplasty. Contact lenses are commonly used to reduce astigmatism and increase vision. There are various types of lenses are available. We reviewed soft contac...

  7. Prospective study of toric IOL outcomes based on the Lenstar LS 900® dual zone automated keratometer

    Directory of Open Access Journals (Sweden)

    Gundersen Kjell

    2012-07-01

    Full Text Available Abstract Background To establish clinical expectations when using the Lenstar LS 900® dual-zone automated keratometer for surgery planning of toric intraocular lenses. Methods Fifty eyes were measured with the Lenstar LS 900® dual-zone automated keratometer . Surgical planning was performed with the data from this device and the known surgically induced astigmatism of the surgeon. Post-operative refractions and visual acuity were measured at 1 month and 3 months. Results Clinical outcomes from 43 uncomplicated surgeries showed an average post-operative refractive astigmatism of 0.44D ±0.25D. Over 70% of eyes had 0.50D or less of refractive astigmatism and no eye had more than 1.0D of refractive astigmatism. Uncorrected visual acuity was 20/32 or better in all eyes at 3 months, with 70% of eyes 20/20 or better. A significantly higher number of eyes had 0.75D or more of post-operative refractive astigmatism when the standard deviation of the pre-operative calculated corneal astigmatism angle, reported by the keratometer, was > 5 degrees. Conclusions In this single-site study investigating the use of the keratometry from the Lenstar LS 900® for toric IOL surgical planning, clinical outcomes appear equivalent to those reported in the literature for manual keratometry and somewhat better than has been reported for some previous automated instruments. A high standard deviation in the pre-operative calculated astigmatism angle, as reported by the keratometer, appears to increase the likelihood of higher post-operative refractive astigmatism.

  8. Factors Influencing Efficacy of Peripheral Corneal Relaxing Incisions during Cataract Surgery

    Directory of Open Access Journals (Sweden)

    Nino Hirnschall

    2015-01-01

    Full Text Available Purpose. To evaluate influencing factors on the residual astigmatism after performing peripheral corneal relaxing incisions (PCRIs during cataract surgery. Methods. This prospective study included patients who were scheduled for cataract surgery with PCRIs. Optical biometry (IOLMaster 500, Carl Zeiss Meditec AG, Germany was taken preoperatively, 1 week, 4 months, and 1 year postoperatively. Additionally, corneal topography (Atlas model 9000, Carl Zeiss Meditec AG, Germany, ORA (Ocular Response Analyzer, Reichert Ophthalmic Instruments, USA, and autorefraction (Autorefractometer RM 8800 Topcon were performed postoperatively. Results. Mean age of the study population n=74 was 73.5 years (±9.3; range: 53 to 90 and mean corneal astigmatism preoperatively was −1.82 D (±0.59; 1.00 to 4.50. Mean corneal astigmatism was reduced to 1.14 D (±0.67; 0.11 to 3.89 4 months postoperatively. A partial least squares regression showed that a high eccentricity of the cornea, a large deviation between keratometry and topography, and a high preoperative astigmatism resulted in a larger postoperative error concerning astigmatism. Conclusions. PCRI causes a reduction of preoperative astigmatism, though the prediction is difficult but several factors were found to be a relevant source of error.

  9. Keratometry device for surgical support

    Directory of Open Access Journals (Sweden)

    Saia Paula

    2009-12-01

    Full Text Available Abstract Background High astigmatisms are usually induced during corneal suturing subsequent to tissue transplantation or any other surgery which involves corneal suturing. One of the reasons is that the procedure is intimately dependent on the surgeon's skill for suturing identical stitches. In order to evaluate the influence of the irregularity on suturing for the residual astigmatism, a prototype for ophthalmic surgical support has been developed. The final intention of this prototype is to be an evaluation tool for guided suture and as an outcome diminish the postoperative astigmatism. Methods The system consists of hand held ring with 36 infrared LEDs, that is to be projected onto the lachrymal film of the cornea. The image is reflected back through the optics of the ocular microscope and its distortion from the original circular shape is evaluated by developed software. It provides keratometric and circularity measurements during surgery in order to guide the surgeon for uniformity in suturing. Results The system is able to provide up to 23D of astigmatism (32D - 55D range and is ± 0.25D accurate. It has been tested in 14 volunteer patients intraoperative and has been compared to a commercial keratometer Nidek Oculus Hand-held corneal topographer. The correlation factors are 0.92 for the astigmatism and 0.97 for the associated axis. Conclusion The system is potentially efficient for guiding the surgeon on uniformity of suturing, presenting preliminary data indicating an important decrease on the residual astigmatism, from an average of 8D - for patients not submitted to the prototype guidance - to 1.4D - for patients who have actually been submitted to the prototype guidance - after the first 24 hours post-surgery and in the subsequent weeks. It also indicates that the surgeon should achieve circularity greater or equal to 98% in order to avoid postoperative astigmatisms over 1D. Trial Registration Trial registration number: CAAE - 0212.0.004.000-09.

  10. Observation of lens aberrations for high resolution electron microscopy II: Simple expressions for optimal estimates

    Energy Technology Data Exchange (ETDEWEB)

    Saxton, W. Owen, E-mail: wos1@cam.ac.uk

    2015-04-15

    This paper lists simple closed-form expressions estimating aberration coefficients (defocus, astigmatism, three-fold astigmatism, coma / misalignment, spherical aberration) on the basis of image shift or diffractogram shape measurements as a function of injected beam tilt. Simple estimators are given for a large number of injected tilt configurations, optimal in the sense of least-squares fitting of all the measurements, and so better than most reported previously. Standard errors are given for most, allowing different approaches to be compared. Special attention is given to the measurement of the spherical aberration, for which several simple procedures are given, and the effect of foreknowledge of this on other aberration estimates is noted. Details and optimal expressions are also given for a new and simple method of analysis, requiring measurements of the diffractogram mirror axis direction only, which are simpler to make than the focus and astigmatism measurements otherwise required. - Highlights: • Optimal estimators for CTEM lens aberrations are more accurate and/or use fewer observations. • Estimators have been found for defocus, astigmatism, three-fold astigmatism, coma and spherical aberration. • Estimators have been found relying on diffractogram shape, image shift and diffractogram orientation only, for a variety of beam tilts. • The standard error for each estimator has been found.

  11. 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

  12. In vivo and in vitro analysis of topographic changes secondary to DSAEK venting incisions

    Directory of Open Access Journals (Sweden)

    Church D

    2011-08-01

    Full Text Available Majid Moshirfar, Monette T Lependu, Dane Church, Marcus C Neuffer John A Moran Eye Center, University of Utah, Salt Lake City, UT, USA Introduction: Descemet’s stripping automated endothelial keratoplasty (DSAEK venting incisions may induce irregular corneal astigmatism. The study examines in vivo and in vitro astigmatic effects of venting incisions. Patients and methods: In vivo analysis examined eleven eyes of eleven patients who had received DSAEK with venting incisions. A chart review of the eleven eyes including assessment of pre and postoperative refraction and topography was performed. In vitro analysis examined three cadaver eyes which received topographic imaging followed by venting incisions at 4 mm, 6 mm, and 7 mm optical zones. Topographic imaging was then performed again after the incisions. Results: Postoperative topographies of eleven eyes demonstrated localized flattening at incision sites and cloverleaf pattern astigmatism. There was a significant difference in corneal irregularity measurement (P = 0.03, but no significant difference in shape factor or change of topographic cylinder. The cloverleaf pattern was found in cadaver eyes with incisions placed at 4 mm and 6 mm optical zones but not at the 7 mm zone. Conclusion: DSAEK venting incisions can cause irregular corneal astigmatism that may affect visual outcomes. The authors recommend placement of venting incisions near the 7 mm optical zone. Keywords: DSAEK, venting incisions, endothelial keratoplasty, astigmatism, endothelium, endothelial transplant

  13. Resolution of electro-holographic image

    Science.gov (United States)

    Son, Jung-Young; Chernyshov, Oleksii; Lee, Hyoung; Lee, Beom-Ryeol; Park, Min-Chul

    2016-06-01

    The resolution of the reconstructed image from a hologram displayed on a DMD is measured with the light field images along the propagation direction of the reconstructed image. The light field images reveal that a point and line image suffers a strong astigmatism but the line focusing distance differences for lines with different directions. This will be astigmatism too. The focusing distance of the reconstructed image is shorter than that of the object. The two lines in transverse direction are resolved when the gap between them is around 16 pixels of the DMD's in use. However, the depth direction is difficult to estimate due to the depth of focus of each line. Due to the astigmatism, the reconstructed image of a square appears as a rectangle or a rhombus.

  14. Cyclopentolate as a cycloplegic drug in determination of refractive error

    Directory of Open Access Journals (Sweden)

    Bolinovska Sofija

    2008-01-01

    Full Text Available Cycloplegia is loss of the power of accommodation with inhibition of a ciliary muscle. We obtain in this way the smallest refraction of the lens and make it possible to determine the presence and size of the particular refractive error in cycloplegia by using cyclopentolate. Cyclopentolate is a synthetic anticholinergic drug and antagonist of the muscarine receptors. If applied in the eye, it blocks the effect of cholinergic stimulation on the sphincter pupillae muscle and ciliary muscle. It provokes severe mydriasis (dilation of the pupil and cycloplegia (paralysis of the accommodation. Cyclopentolate has been used occasionaly in diagnostic purposes: defining ocular refraction and in ophthalmoscopy. This is the prospective study which included 200 children (400 eyes aged 3-18 years, carried out in one ambulatory ophthalmological examination. The results were analysed using standard statistical methods. The most often refractive error in the examined group of children is hyperopia with hyperopic astigmatism, then myopia with myopic astigmatism and mixtus astigmatism are the most often in the oldest group of children. The mean value of corneal astigmatism on the right eye was 1.24 D, on the left eye 1.23 D. Anisometropy was found in 40% children. The presence of myopia, myopic and astigmatism mixtus tended to increase, and hyperopia and hyperopic astigmatism tended to decrease toward older groups of children. Refractive error could result in a poor development of visual acuity, causing amblyopia and strabismus, and because of that represents an important public health problem. As one of amblyogenic risk factors in children, it can be prevented with screening program and appropriate treatment, thus providing prevention of amblyopia as one form of blindness.

  15. Unveiling orbital angular momentum and acceleration of light beams and electron beams

    Science.gov (United States)

    Arie, Ady

    Special beams, such as the vortex beams that carry orbital angular momentum (OAM) and the Airy beam that preserves its shape while propagating along parabolic trajectory, have drawn significant attention recently both in light optics and in electron optics experiments. In order to utilize these beams, simple methods are needed that enable to easily quantify their defining properties, namely the OAM for the vortex beams and the nodal trajectory acceleration coefficient for the Airy beam. Here we demonstrate a straightforward method to determine these quantities by astigmatic Fourier transform of the beam. For electron beams in a transmission electron microscope, this transformation is easily realized using the condenser and objective stigmators, whereas for light beam this can be achieved using a cylindrical lens. In the case of Laguerre-Gauss vortex beams, it is already well known that applying the astigmatic Fourier transformation converts them to Hermite-Gauss beams. The topological charge (and hence the OAM) can be determined by simply counting the number of dark stripes of the Hermite-Gauss beam. We generated a series of electron vortex beams and managed to determine the topological charge up to a value of 10. The same concept of astigmatic transformation was then used to unveil the acceleration of an electron Airy beam. The shape of astigmatic-transformed depends only on the astigmatic measure and on the acceleration coefficient. This method was experimentally verified by generating electron Airy beams with different known acceleration parameters, enabling direct comparison to the deduced values from the astigmatic transformation measurements. The method can be extended to other types of waves. Specifically, we have recently used it to determine the acceleration of an optical Airy beams and the topological charge of so-called Airy-vortex light beam, i.e. an Airy light beam with an embedded vortex. This work was supported by DIP and the Israel Science

  16. Unique reflector arrangement within very wide field of view for multibeam antennas

    Science.gov (United States)

    Dragone, C.

    1983-12-01

    It is pointed out that Cassegrainian and Gregorian reflector arrangements are needed for multibeam ground station and satellite antennas. A Cassegrainian arrangement is considered, taking into account aberrations. Dragone (1982) has presented a requirement for the minimization of astigmatism. In the present investigation a formula is presented for describing the deformation coefficients needed to eliminate coma on the basis of a slight deformation of the reflectors. The importance of residual astigmatism due to a derived equation is examined, and attention is given to a compact reflector arrangement which is the result of three optimizations with respect to aberration minimization.

  17. Symbolic algebra approach to the calculation of intraocular lens power following cataract surgery

    Science.gov (United States)

    Hjelmstad, David P.; Sayegh, Samir I.

    2013-03-01

    We present a symbolic approach based on matrix methods that allows for the analysis and computation of intraocular lens power following cataract surgery. We extend the basic matrix approach corresponding to paraxial optics to include astigmatism and other aberrations. The symbolic approach allows for a refined analysis of the potential sources of errors ("refractive surprises"). We demonstrate the computation of lens powers including toric lenses that correct for both defocus (myopia, hyperopia) and astigmatism. A specific implementation in Mathematica allows an elegant and powerful method for the design and analysis of these intraocular lenses.

  18. Wound construction in manual small incision cataract surgery

    Directory of Open Access Journals (Sweden)

    Haldipurkar S

    2009-01-01

    Full Text Available The basis of manual small incision cataract surgery is the tunnel construction for entry to the anterior chamber. The parameters important for the structural integrity of the tunnel are the self-sealing property of the tunnel, the location of the wound on the sclera with respect to the limbus, and the shape of the wound. Cataract surgery has gone beyond just being a means to get the lens out of the eye. Postoperative astigmatism plays an important role in the evaluation of final outcome of surgery. Astigmatic consideration, hence, forms an integral part of incisional considerations prior to surgery.

  19. The refractive outcome of Toric Lentis Mplus implant in cataract surgery

    Science.gov (United States)

    Chiam, Patrick J; Quah, Say A

    2016-01-01

    AIM To evaluate the refractive outcome of Toric Lentis Mplus intraocular lens (IOL) implant. METHODS This is a retrospective case series. Consecutive patients with corneal astigmatism of at least 1.5 D had Toric Lentis Mplus IOL implant during cataract surgery. The exclusion criteria included irregular astigmatism on corneal topography, large scotopic pupil diameter (>6 mm), poor visual potential and significant ocular comorbidity. Postoperative manifest refraction, uncorrected distance visual acuity (UDVA), best-corrected distance visual acuity (BCVA), uncorrected intermediate visual acuity (UIVA) at 3/4 m and uncorrected near visual acuity (UNVA) were obtained. RESULTS There were 70 eyes from 49 patients in this study. Patients were refracted at a median of 8.9wk (range 4.0 to 15.5) from the operation date. Sixty-five percent of eyes had 6/7.5 (0.10 logMAR) or better, and 99% 6/12 (0.30 logMAR) or better postoperative UDVA. Eighty-nine percent could read Jaeger (J) 3 (0.28 logMAR) and 95% J5 (0.37 logMAR) at 40 cm. The median magnitude of astigmatism decreased from 1.91 D to 0.49 D (Wilcoxon, PLentis Mplus IOL has good predictability in reducing preexisting corneal astigmatism. PMID:27275424

  20. Effect of iris registration on outcomes of LASIK for myopia with the VISX CustomVue platform

    DEFF Research Database (Denmark)

    Moshirfar, Majid; Chen, Michael C; Espandar, Ladan;

    2009-01-01

    PURPOSE: To compare visual outcomes after LASIK using the VISX STAR S4 CustomVue, with and without Iris Registration technology. METHODS: In this retrospective study, LASIK was performed on 239 myopic eyes, with or without astigmatism, of 142 patients. Iris registration LASIK was performed on 121...

  1. Ultrasound-induced acoustophoretic motion of microparticles in three dimensions

    DEFF Research Database (Denmark)

    Muller, Peter Barkholt; Rossi, M.; Marín, Á. G.;

    2013-01-01

    D particle motion was recorded using astigmatism particle tracking velocimetry under controlled thermal and acoustic conditions in a long, straight, rectangular microchannel actuated in one of its transverse standing ultrasound-wave resonance modes with one or two half-wavelengths. The acoustic...

  2. Creation, doubling, and splitting, of vortices in intracavity second harmonic generation

    CERN Document Server

    Lim, O K; Saffman, M; Królikowski, W

    2003-01-01

    We demonstrate generation and frequency doubling of unit charge vortices in a linear astigmatic resonator. Topological instability of the double charge harmonic vortices leads to well separated vortex cores that are shown to rotate, and become anisotropic, as the resonator is tuned across resonance.

  3. Ptosis - infants and children

    Science.gov (United States)

    Blepharoptosis-children; Congenital ptosis; Eyelid drooping-children; Eyelid drooping-amblyopia; Eyelid drooping-astigmatism ... Ptosis in infants and children is often due to a problem with the muscle that raises the eyelid. A nerve problem in the eyelid can ...

  4. Multifocal Toric Intraocular Lens for Traumatic Cataract in a Child

    Directory of Open Access Journals (Sweden)

    Yanfeng Zeng

    2016-10-01

    Full Text Available A child suffering from traumatic cataract and corneal astigmatism of 2.14 D had a phacoemulsification operation and implantation of a ReSTOR Toric intraocular lens (IOL to correct the astigmatism. The primary outcome measurements were the uncorrected distance visual acuity (UDVA, uncorrected near vision at 40 cm, intraocular pressure, spherical equivalent refraction, residual astigmatism, corneal astigmatism, presence of unusual optical phenomena, and use of spectacles. At 7 months postoperatively, UDVA was maintained between 16/20 and 24/20, near vision was between J1 and J3, residual spherical refraction was 0–0.37 D, and residual refractive cylinder was between 0 and 0.67 D. A multifocal toric IOL can provide the possibility of satisfactory vision for both distant and near conditions without the use of spectacles to meet children’s needs when studying and doing sports. Additionally, binocular vision can be reconstructed. This intervention, therefore, seems to be a satisfactory alternative.

  5. Change in corneal curvature induced by surgery

    NARCIS (Netherlands)

    G. van Rij (Gabriel)

    1987-01-01

    textabstractThe first section deals with the mechanisms by which sutures, incisions and intracorneal contact lenses produce a change in corneal curvature. To clarify the mechanisms by which incisions and sutures produce astigmatism, we made incisions and placed sutures in the corneoscleral limbus of

  6. Meta-analysis to compare the safety and efficacy of manual small incision cataract surgery and phacoemulsification

    Directory of Open Access Journals (Sweden)

    Parikshit Gogate

    2015-01-01

    Conclusion: The outcome of this meta-analysis indicated there is no difference between phacoemulsification and SICS for BCVA and UCVA of 6/18 and 6/60. Endothelial cell loss and intraoperative and postoperative complications were similar between procedures. SICS resulted in statistically greater astigmatism and UCVA of 6/9 or worse, however, near UCVA was better.

  7. Visual outcomes and optical quality after implantation of a diffractive multifocal toric intraocular lens

    Science.gov (United States)

    Chen, Xiangfei; Zhao, Ming; Shi, Yuhua; Yang, Liping; Lu, Yan; Huang, Zhenping

    2016-01-01

    Background: This study evaluated the visual function after implantation of a multifocal toric intraocular lenses (IOLs). Materials and Methods: This study involved 10 eyes from eight cataract patients with corneal astigmatism of 1.0 diopter (D) or higher who had received phacoemulsification with implantation of an AcrySof IQ ReSTOR Toric IOL. Six-month evaluations included visual acuity, spherical equivalent (SE), defocus curve, residual astigmatism, IOL rotation, contrast sensitivity (CS), wavefront aberrations, modulation transfer function (MTF), and patient satisfaction assessments. Results: At 6 months postoperatively, uncorrected distance visual acuity (logarithm of the minimum angle of resolution) was 0.09 ± 0.04, corrected distance visual acuity was 0.02 ± 0.11, and uncorrected near visual acuity was 0.12 ± 0.07. The mean SE was −0.095 ± 0.394 D (±0.50 D in 90%). Refractive astigmatism at the 6-month follow-up visit was significantly reduced to 0.35 ± 0.32 D from 1.50 ± 0.41 D presurgery (P 0.05). There was an increase in MTF results between preoperative and postoperative evaluations at all spatial frequencies. Conclusions: The diffractive multifocal toric IOL is able to provide a predictable astigmatic correction with apparently outstanding levels of optical quality after implantation. PMID:27221680

  8. Design of high power solid-state pulsed laser resonators

    International Nuclear Information System (INIS)

    Methods and configurations for the design of high power solid-state pulsed laser resonators, operating in free running, are presented. For fundamental mode high power resonators, a method is proposed for the design of a resonator with joined stability zones. In the case of multimode resonators, two configurations are introduced for maximizing the laser overall efficiency due to the compensation of the astigmatism induced by the excitation. The first configuration consists in a triangular ring resonator. The results for this configuration are discussed theoretically, showing that it is possible to compensate the astigmatism of the thermal lens virtually in a 100%; however this is only possible for a specific pumping power. The second configuration proposes a dual-active medium resonator, rotated 90 degree one from the other around the optical axis, where each active medium acts as an astigmatic lens of the same dioptric power. The reliability of this configuration is corroborated experimentally using a Nd:YAG dual-active medium resonator. It is found that in the pumping power range where the astigmatism compensation is possible, the overall efficiency is constant, even when increasing the excitation power with the consequent increase of the thermal lens dioptric power. (Author)

  9. Expressions for third-order aberration theory for holographic images

    Indian Academy of Sciences (India)

    S K Tripathy; S Ananda Rao

    2003-01-01

    Expressions for third-order aberration in the reconstructed wave front of point objects are established by Meier. But Smith, Neil Mohon, Sweatt independently reported that their results differ from that of Meier. We found that coefficients for spherical aberration, astigmatism, tally with Meier’s while coefficients for distortion and coma differ.

  10. Anterior segment study with the pentacam scheimpflug camera in refractive surgery candidates

    Directory of Open Access Journals (Sweden)

    Masih Hashemi

    2013-01-01

    Conclusions: Myopic eyes had steeper corneas than hyperopic eyes and anterior chamber measurements were significantly higher in the myopic eyes. In myopic eyes, AE max and PE max and K max measurements were higher, and ACD measurements were lower in the astigmatic groups.

  11. The correlation between variation of visual acuity and the anterior chamber depth in the early period after phacoemulsification

    Directory of Open Access Journals (Sweden)

    Kai-jian CHEN

    2011-04-01

    Full Text Available Objective To investigate the correlation between the visual acuity variation and the anterior chamber depth in the early period after phacoemulsification.Methods Thirty-six eyes of 32 patients with age-related cataract underwent 3.2mm clear corneal incision phacoemulsification and intraocular lens(IOL implantation.The visual acuity was examined and horizontal curvature(K1,vertical curvature(K2,corneal astigmatism,and anterior chamber depth were measured with IOL-master preoperatively and also on 1,3,7 and 15 postoperative days.The changes in parameters were compared,and the correlations among visual acuity,corneal astigmatism and anterior chamber depth were analyzed.Results Before operation and 1d,3d,7d and 15d after operation,the corneal astigmatism was-0.87±0.40D,-1.92±1.38D,-1.69±1.13D,-1.45±0.79D and-1.36±0.74D;the anterior chamber depth was 3.08±0.35mm,4.04±0.38mm,4.28±0.29mm,4.22±0.17mm and 4.22±0.16mm;the visual acuity was 0.18±0.10,0.44±0.14,0.59±0.12,0.61±0.11 and 0.62±0.14.Significant difference was found between pre-operative and postoperative visual acuity,corneal astigmatism and anterior chamber depth,and it was also found in corneal astigmatism between 1d and 15d post operation(P < 0.05,as well as in anterior chamber depth and visual acuity between 1d and 3d post operation(P < 0.05.A positive correlation was found between visual acuity and corneal astigmatism on 1d(r=0.42,P < 0.05,3d(r=0.35,P < 0.05 and 7d(r=0.35,P < 0.05 post operation;and a negative correlation was found between visual acuity and anterior chamber depth on 3d(r=-0.29,P < 0.05,7d(r=-0.43,P < 0.01 and 15d(r=-0.37,P < 0.05 post operation.Conclusion Both the corneal astigmatism and the anterior chamber depth are correlated with the visual acuity variation in the early period after phacoemulsification.

  12. 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

  13. SURGICAL AND VISUAL OUTCOME OF PHACOEMULSIFICATION SURGERY (ROUTINE AND MICRO - PHACO (BIMANUAL PHACO: A COMPARATIVE STUDY

    Directory of Open Access Journals (Sweden)

    Sudha

    2015-03-01

    Full Text Available Cataract surgery has evolved over the past few decades with progressive decrease in the size of the incision. Originally from 12 mm intracapsular incision to bimanual phacoemulsification (Micro - Phaco that has incision size of just 700 microns. In the pres ent comparative PROSPECTIVE study best corrected visual acuity postoperatively and surgically induced astigmatism were compared in routine Phacoemulsification technique and bimanual phaco (Micro - Phaco 60 eyes were studied. There was no statistically signi ficant difference in postoperative best corrected visual acuity (BCVA of patients operated with Micro - Phaco or routine Phacoemulsification. There was difference in surgically induced astigmatism (SIA ; average SIA in microphaco was 0.5972 as against 0.832 8 in routine Phacoemulsification.

  14. Line focusing for soft x-ray laser-plasma lasing.

    Science.gov (United States)

    Bleiner, Davide; Balmer, Jürg E; Staub, Felix

    2011-12-20

    A computational study of line-focus generation was done using a self-written ray-tracing code and compared to experimental data. Two line-focusing geometries were compared, i.e., either exploiting the sagittal astigmatism of a tilted spherical mirror or using the spherical aberration of an off-axis-illuminated spherical mirror. Line focusing by means of astigmatism or spherical aberration showed identical results as expected for the equivalence of the two frames of reference. The variation of the incidence angle on the target affects the line-focus length, which affects the amplification length such that as long as the irradiance is above the amplification threshold, it is advantageous to have a longer line focus. The amplification threshold is physically dependent on operating parameters and plasma-column conditions and in the present study addresses four possible cases. PMID:22193201

  15. Topography-guided custom ablation treatment for treatment of keratoconus

    Directory of Open Access Journals (Sweden)

    Rohit Shetty

    2013-01-01

    Full Text Available Keratoconus is a progressive ectatic disorder of the cornea which often presents with fluctuating refraction and high irregular astigmatism. Correcting the vision of these patients is often a challenge because glasses are unable to correct the irregular astigmatism and regular contact lenses may not fit them very well. Topography-guided custom ablation treatment (T-CAT is a procedure of limited ablation of the cornea using excimer laser with the aim of regularizing the cornea, improving the quality of vision and possibly contact lens fit. The aim of the procedure is not to give a complete refractive correction. It has been tried with a lot of success by various groups of refractive surgeons around the world but a meticulous and methodical planning of the procedure is essential to ensure optimum results. In this paper, we attempt to elucidate the planning for a T-CAT procedure for various types of cones and asphericities.

  16. Coma-free alignment of high resolution electron microscopes with the aid of optical diffractograms

    International Nuclear Information System (INIS)

    Alignment by means of current commutating and defocusing of the objective does not yield the desired rotational symmetry of the imaging pencils. This was found while aligning a transmission electron microscope with a single field condenser objective. A series of optical diffractograms of micrographs taken under the same tilted illumination yet under various azimuths have been arranged in a tableau, wherein strong asymmetry is exhibited. Quantitative evaluation yields the most important asymmetric aberration to be the axial coma, which becomes critical when a resolution better than 5 A0 is obtained. The tableau also allows an assessment of the three-fold astigmatism. A procedure has been developed which aligns the microscope onto the coma-free and dispersion-free pencil axis and does not rely on current communication. The procedure demands equal appearance of astigmatic carbon film images produced under the same tilt yet diametrical azimuth. (Auth.)

  17. Optical design of Kirkpatrick-Baez microscope for ICF

    International Nuclear Information System (INIS)

    A new flux-resolution optical design method of Kirkpatrick-Baez microscope (KB microscope) is proposed. In X-ray imaging diagnostics of inertial confinement fusion(ICF), spatial resolution and flux are always the key parameters. While the traditional optical design of KB microscope is to correct on-axis spherical aberration and astigmatic aberration, flux-resolution method is based on lateral aberration of full field and astigmatic aberration. Thus the spatial resolution related to field dimension and light flux can be estimated. By the expressions of spatial resolution and actual limits in ICF, rules of how to set original structure and optical design flow are summarized. An instance is presented and it shows that the design has met the original targets and overcome the shortcomings of image characterization in compressed core by traditional spherical aberration correction. (authors)

  18. Imaging with Spherically Bent Crystals or Reflectors

    Energy Technology Data Exchange (ETDEWEB)

    Bitter, M; Hill, K W; Scott, S; Ince-Cushman, A; Reinke, M; Podpaly, Y; Rice, J E; Beiersdorfer, P

    2010-06-01

    This paper consists of two parts: Part I describes the working principle of a recently developed x-ray imaging crystal spectrometer, where the astigmatism of spherically bent crystals is being used with advantage to record spatially resolved spectra of highly charged ions for Doppler measurements of the ion-temperature and toroidal plasmarotation- velocity profiles in tokamak plasmas. This type of spectrometer was thoroughly tested on NSTX and Alcator C-Mod, and its concept was recently adopted for the design of the ITER crystal spectrometers. Part II describes imaging schemes, where the astigmatism has been eliminated by the use of matched pairs of spherically bent crystals or reflectors. These imaging schemes are applicable over a wide range of the electromagnetic radiation, which includes microwaves, visible light, EUV radiation, and x-rays. Potential applications with EUV radiation and x-rays are the diagnosis of laserproduced plasmas, imaging of biological samples with synchrotron radiation, and lithography.

  19. Transport of a high brightness proton beam through the Munich tandem accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Moser, M., E-mail: marcus.moser@unibw.de [Universität der Bundeswehr München, Institut für Angewandte Physik und Messtechnik LRT2, Department für Luft- und Raumfahrttechnik, 85577 Neubiberg (Germany); Greubel, C. [Universität der Bundeswehr München, Institut für Angewandte Physik und Messtechnik LRT2, Department für Luft- und Raumfahrttechnik, 85577 Neubiberg (Germany); Carli, W. [Beschleunigerlabor MLL, 85478 Garching (Germany); Peeper, K.; Reichart, P.; Urban, B.; Vallentin, T. [Universität der Bundeswehr München, Institut für Angewandte Physik und Messtechnik LRT2, Department für Luft- und Raumfahrttechnik, 85577 Neubiberg (Germany); Dollinger, G., E-mail: guenther.dollinger@unibw.de [Universität der Bundeswehr München, Institut für Angewandte Physik und Messtechnik LRT2, Department für Luft- und Raumfahrttechnik, 85577 Neubiberg (Germany)

    2015-04-01

    Basic requirement for ion microprobes with sub-μm beam focus is a high brightness beam to fill the small phase space usually accepted by the ion microprobe with enough ion current for the desired application. We performed beam transport simulations to optimize beam brightness transported through the Munich tandem accelerator. This was done under the constraint of a maximum ion current of 10 μA that is allowed to be injected due to radiation safety regulations and beam power constrains. The main influence of the stripper foil in conjunction with intrinsic astigmatism in the beam transport on beam brightness is discussed. The calculations show possibilities for brightness enhancement by using astigmatism corrections and asymmetric filling of the phase space volume in the x- and y-direction.

  20. [Keratoconus, the most common corneal dystrophy. Can keratoplasty be avoided?].

    Science.gov (United States)

    Arne, Jean Louis; Fournié, Pierre

    2011-01-01

    Keratoconus is the most common form of corneal dystrophy. It consists of a non inflammatory progressive thinning process that leads to conical ectasia of the cornea, causing high myopia and astigmatism. In more advanced cases, opacities can be seen at the apex of the cone. Traditional conservative management of keratoconus begins with spectacle correction and contact lenses. Surgery is recommended when a stable contact lens fit fails to provide adequate vision. Keratoplasty was long the only surgical treatment, but recent years have seen the introduction of new surgical options:--Collagen cross-linking stiffens the cornea and can halt disease progression;--Intrastromal corneal rings can reduce astigmatism and improve visual acuity;--Intraocular lenses are valuable additional options for the correction of refractive errors. Currently, keratoplasty is mainly restricted to patients with opacities of the central cornea. PMID:22039707

  1. Topography-guided custom ablation treatment for treatment of keratoconus.

    Science.gov (United States)

    Shetty, Rohit; D'Souza, Sharon; Srivastava, Samaresh; Ashwini, R

    2013-08-01

    Keratoconus is a progressive ectatic disorder of the cornea which often presents with fluctuating refraction and high irregular astigmatism. Correcting the vision of these patients is often a challenge because glasses are unable to correct the irregular astigmatism and regular contact lenses may not fit them very well. Topography-guided custom ablation treatment (T-CAT) is a procedure of limited ablation of the cornea using excimer laser with the aim of regularizing the cornea, improving the quality of vision and possibly contact lens fit. The aim of the procedure is not to give a complete refractive correction. It has been tried with a lot of success by various groups of refractive surgeons around the world but a meticulous and methodical planning of the procedure is essential to ensure optimum results. In this paper, we attempt to elucidate the planning for a T-CAT procedure for various types of cones and asphericities. PMID:23925335

  2. Optical path length and trajectory stability in rotationally asymmetric multipass cells.

    Science.gov (United States)

    Harden, Galen H; Cortes-Herrera, Luis E; Hoffman, Anthony J

    2016-08-22

    We describe the behavior of optical trajectories in multipass rotationally asymmetric cavities (RACs) using a phase-space motivated approach. Emphasis is placed on generating long optical paths. A trajectory with an optical path length of 18 m is generated within a 68 cm3 volume. This path length to volume ratio (26.6 cm-2) is large compared to current state of the art multipass cells such as the cylindrical multipass cell (6.6 cm-2) and astigmatic Herriott cell (9 cm-2). Additionally, the effect of small changes to the input conditions on the path length is studied and compared to the astigmatic Herriott cell. This work simplifies the process of designing RACs with long optical path lengths and could lead to broader implementation of these multipass cells.

  3. Plenoptic microscope based on laser optical feedback imaging (LOFI)

    CERN Document Server

    Glastre, W; Jacquin, O; de Chatellus, H Guillet; Lacot, E

    2015-01-01

    We present an overview of the performances of a plenoptic microscope which combines the high sensitivity of a laser optical feedback imaging setup , the high resolution of optical synthetic aperture and a shot noise limited signal to noise ratio by using acoustic photon tagging. By using an adapted phase filtering, this microscope allows phase drift correction and numerical aberration compensation (defocusing, coma, astigmatism ...). This new kind of microscope seems to be well adapted to make deep imaging through scattering and heterogeneous media.

  4. Asymmetric wavelet reconstruction of particle hologram with an elliptical Gaussian beam illumination.

    Science.gov (United States)

    Wu, Xuecheng; Wu, Yingchun; Zhou, Binwu; Wang, Zhihua; Gao, Xiang; Gréhan, Gérard; Cen, Kefa

    2013-07-20

    We propose an asymmetric wavelet method to reconstruct a particle from a hologram illuminated by an elliptical, astigmatic Gaussian beam. The particle can be reconstructed by a convolution of the asymmetric wavelet and hologram. The reconstructed images have the same size and resolution as the recorded hologram; therefore, the reconstructed 3D field is convenient for automatic particle locating and sizing. The asymmetric wavelet method is validated by both simulated holograms of spherical particles and experimental holograms of opaque, nonspherical coal particles.

  5. Fibrin-glue assisted multilayered amniotic membrane transplantation in surgical management of pediatric corneal limbal dermoid: a novel approach

    OpenAIRE

    Pirouzian, Amir; Ly, Hang; Holz, Huck; Sudesh, Rattehalli S.; Chuck, Roy S.

    2010-01-01

    Purpose To report a new surgical technique for excising pediatric corneal limbal dermoid and the post-resection ocular surface reconstruction. Methods We describe a method of deep lamellar excision followed by sutureless multilayered amniotic membrane transplantation in surgical management of corneal limbal dermoid. Result This technique achieves a rapid corneal re-epithelization, reduces post-operative pain, and will diminish post-operative scarring. Preoperative corneal astigmatism will per...

  6. Intraocular correction of high-degree ametropia using individual multifocal LentisMPlus IOL

    OpenAIRE

    Fedorova, I. S.; S.Y. Kopayev; T.S. Kuznetsova,; D.G. Uzunyan

    2013-01-01

    ABSTRACT Background. For surgical correction of high-degree ametropia aggravated with astigmatism the following options are available: excimer laser correction; phakic lens implantation; bioptika – a combination of ablating the transparent crystalline lens (ATL) with implantation of multifocal toric diopter IOL of standard series and LASIK for the correction of a residual refractive error, ATL using 2 IOLs according to the Technology «Piggy Back»; additional meniscus IOL implantation «Ad...

  7. Changes in Corneal Topography after 25-Gauge Transconjunctival Sutureless Vitrectomy versus after 20-Gauge Standard Vitrectomy

    OpenAIRE

    Okamoto, F; Okamoto, C.; Sakata, N.; Hiratsuka, K; Yamane, N; Hiraoka, T.; Kaji, Y; Oshika, T.

    2007-01-01

    PurposeTo evaluate the changes in regular and irregular corneal astigmatism after 25-gauge transconjunctival sutureless vitrectomy and 20-gauge standard vitrectomy.DesignProspective observational comparative case series.ParticipantsThirty-two eyes of 32 patients undergoing 25-gauge transconjunctival sutureless vitrectomy and 25 eyes of 24 patients undergoing 20-gauge standard vitrectomy.MethodsCorneal topography was obtained preoperatively and at 2 weeks and 1 month postoperatively.Main Outco...

  8. Velocity map imaging of a slow beam of ammonia molecules inside a quadrupole guide

    OpenAIRE

    Quintero-Pérez, Marina; Jansen, Paul; Bethlem, Hendrick L.

    2012-01-01

    Velocity map imaging inside an electrostatic quadrupole guide is demonstrated. By switching the voltages that are applied to the rods, the quadrupole can be used for guiding Stark decelerated molecules and for extracting the ions. The extraction field is homogeneous along the axis of the quadrupole while it defocuses the ions in the direction perpendicular to both the axis of the quadrupole and the axis of the ion optics. To compensate for this astigmatism, a series of planar electrodes with ...

  9. Comparison of Anterior Segment Measurements with Scheimpflug/Placido Photography-Based Topography System and IOLMaster Partial Coherence Interferometry in Patients with Cataracts

    OpenAIRE

    Jinhai Huang; Na Liao; Giacomo Savini; Fangjun Bao; Ye Yu; Weicong Lu; Qingjie Hu; Qinmei Wang

    2014-01-01

    Purpose. To assess the consistency of anterior segment measurements obtained using a Sirius Scheimpflug/Placido photography-based topography system (CSO, Italy) and IOLMaster partial coherence interferometry (Carl Zeiss Meditec, Germany) in eyes with cataracts. Methods. A total of 90 eyes of 90 patients were included in this prospective study. The anterior chamber depth (ACD), keratometry (K), corneal astigmatism axis, and white to white (WTW) values were randomly measured three times with Si...

  10. Compact adaptive optic-optical coherence tomography system

    Energy Technology Data Exchange (ETDEWEB)

    Olivier, Scot S. (Livermore, CA); Chen, Diana C. (Fremont, CA); Jones, Steven M. (Danville, CA); McNary, Sean M. (Stockton, CA)

    2012-02-28

    Badal Optometer and rotating cylinders are inserted in the AO-OCT to correct large spectacle aberrations such as myopia, hyperopic and astigmatism for ease of clinical use and reduction. Spherical mirrors in the sets of the telescope are rotated orthogonally to reduce aberrations and beam displacement caused by the scanners. This produces greatly reduced AO registration errors and improved AO performance to enable high order aberration correction in a patient eyes.

  11. Aberration influenced generation of rotating two-lobe light fields

    Science.gov (United States)

    Kotova, S. P.; Losevsky, N. N.; Prokopova, D. V.; Samagin, S. A.; Volostnikov, V. G.; Vorontsov, E. N.

    2016-08-01

    The influence of aberrations on light fields with a rotating intensity distribution is considered. Light fields were generated with the phase masks developed using the theory of spiral beam optics. The effects of basic aberrations, such as spherical aberration, astigmatism and coma are studied. The experimental implementation of the fields was achieved with the assistance of a liquid crystal spatial light modulator HOLOEYE HEO-1080P, operating in reflection mode. The results of mathematical modelling and experiments have been qualitatively compared.

  12. Management of visual disturbances in albinism: a case report

    OpenAIRE

    Omar Rokiah; Idris Siti; Meng Chung; Knight Victor

    2012-01-01

    Abstract Introduction A number of vision defects have been reported in association with albinism, such as photophobia, nystagmus and astigmatism. In many cases only prescription sunglasses are prescribed. In this report, the effectiveness of low-vision rehabilitation in albinism, which included prescription of multiple visual aids, is discussed. Case presentation We present the case of a 21-year-old Asian woman with albinism and associated vision defects. Her problems were blurring of distant...

  13. [Heterotopic fundus (author's transl)].

    Science.gov (United States)

    Denden, A

    1976-07-01

    Fundus heterotopicus is the term used to describe a rare, non-hereditary curvature anomaly of the fundus in the non-myopic eye, which is characterized: 1. functionally, by a slowly increasing myopic-astigmatic refractive error, 2. by correctable bitemporal or binasal refractionscomata and 3. ophthalmoscopically by a posterior out-pouching of the nasal or temporal fundus portions, and including the optic disc and macula in the obliquely descending wall of the extasis.

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

    Directory of Open Access Journals (Sweden)

    Hassan HASHEMI

    2016-02-01

    Full Text Available 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. Keyword: Refractive errors, Cross-sectional study, Iran

  15. Diode-pumped dye laser

    Science.gov (United States)

    Burdukova, O. A.; Gorbunkov, M. V.; Petukhov, V. A.; Semenov, M. A.

    2016-10-01

    This letter reports diode pumping for dye lasers. We offer a pulsed dye laser with an astigmatism-compensated three-mirror cavity and side pumping by blue laser diodes with 200 ns pulse duration. Eight dyes were tested. Four dyes provided a slope efficiency of more than 10% and the highest slope efficiency (18%) was obtained for laser dye Coumarin 540A in benzyl alcohol.

  16. Topical timolol maleate 0.5% solution for the management of deep periocular infantile hemangiomas.

    Science.gov (United States)

    Painter, Sally L; Hildebrand, Göran Darius

    2016-04-01

    This retrospective, consecutive, clinical case series examined the use of topical timolol in the treatment of 5 children with deep, periocular infantile hemangiomas that caused astigmatism, change in head posture, or ptosis. All patients were treated with timolol maleate solution 0.5% twice daily until the lesions had regressed. All 5 children showed regression of the lesion and improvement in amblyogenic risk factors within 2 weeks.

  17. Toric and toric multifocal IOLs in meridional amblyopia

    Institute of Scientific and Technical Information of China (English)

    Kirithika; Muthusamy; Charles; Claoué

    2015-01-01

    <正>Dear Sir,M eridional amblyopia is sometimes put forward as a reason for not implanting Toric intraocular lenses(IOLs).It has been noted that patients with high levels of childhood astigmatism(>3 DC)can develop persistent orientation-dependent visual deficits despite optical correction.Studies by Mitchell et al[1]demonstrated that meridional visual deprivation during the critical period of visual development results in permanently reduced response to stimuli in those orientations.This phenomenon was termed

  18. Compact adaptive optic-optical coherence tomography system

    Energy Technology Data Exchange (ETDEWEB)

    Olivier, Scot S. (Livermore, CA); Chen, Diana C. (Fremont, CA); Jones, Steven M. (Danville, CA); McNary, Sean M. (Stockton, CA)

    2011-05-17

    Badal Optometer and rotating cylinders are inserted in the AO-OCT to correct large spectacle aberrations such as myopia, hyperopic and astigmatism for ease of clinical use and reduction. Spherical mirrors in the sets of the telescope are rotated orthogonally to reduce aberrations and beam displacement caused by the scanners. This produces greatly reduced AO registration errors and improved AO performance to enable high order aberration correction in a patient eyes.

  19. Exploded representation of a refracting surface

    Directory of Open Access Journals (Sweden)

    W.H. Heath

    2005-01-01

    Full Text Available The concept of the exploded refracting sur-face is useful in the optics of contact lenses and vision underwater. The purpose of this paper is to show how to represent a refracting surface as an exploded pair of surfaces separated by a gap of zero width.  The analysis is in terms of linear optics and allows for astigmatic and non-coaxial cases.

  20. Foci in ray pencils of general divergency

    OpenAIRE

    W. F. Harris; R. D. van Gool

    2009-01-01

    In generalized optical systems, that is, in systems which may contain thin refracting elements of asymmetric dioptric power, pencils of rays may exhibit phenomena that cannot occur in conventional optical systems.  In conventional optical systems astigmatic pencils have two principal meridians that are necessarily orthogonal; in generalized systems the principal meridians can be at any angle.  In fact in generalized systems a pencil may have only one principal meridian or even none at all.  I...

  1. Spatial shaping for generating arbitrary optical dipoles traps for ultracold degenerate gases

    OpenAIRE

    Jeffrey G. Lee; Hill III, W. T.

    2014-01-01

    We present two spatial-shaping approaches -- phase and amplitude -- for creating two-dimensional optical dipole potentials for ultracold neutral atoms. When combined with an attractive or repulsive Gaussian sheet formed by an astigmatically focused beam, atoms are trapped in three dimensions resulting in planar confinement with an arbitrary network of potentials -- a free-space atom chip. The first approach utilizes an adaptation of the generalized phase-contrast technique to convert a phase ...

  2. Geographical prevalence and risk factors for pterygium: a systematic review and meta-analysis

    OpenAIRE

    Liu, Lei; Wu, Jingyang; Geng, Jin; Yuan, Zhe; Huang, Desheng

    2013-01-01

    Objective Pterygium is considered to be a proliferative overgrowth of bulbar conjunctiva that can induce significant astigmatism and cause visual impairment; this is the first meta-analysis to investigate the pooled prevalence and risk factors for pterygium in the global world. Design A systematic review and meta-analysis of population-based studies. Setting International. Participants A total of 20 studies with 900 545 samples were included. Primary outcome measure The pooled prevalence and ...

  3. Adaptation to interocular differences in blur

    OpenAIRE

    Kompaniez, E.; Sawides, L.; Marcos, S.; Webster, M A

    2013-01-01

    Adaptation to a blurred image causes a physically focused image to appear too sharp, and shifts the point of subjective focus toward the adapting blur, consistent with a renormalization of perceived focus. We examined whether and how this adaptation normalizes to differences in blur between the two eyes, which can routinely arise from differences in refractive errors. Observers adapted to images filtered to simulate optical defocus or different axes of astigmatism, as well as to images that w...

  4. Orbital angular momentum exchange in an optical parametric oscillator

    OpenAIRE

    Martinelli, M.; Huguenin, J. A. O.; Nussenzveig, P.; Khoury, A. Z.

    2004-01-01

    We present a study of orbital angular momentum transfer from pump to down-converted beams in a type-II Optical Parametric Oscillator. Cavity and anisotropy effects are investigated and demostrated to play a central role in the transverse mode dynamics. While the idler beam can oscillate in a Laguerre-Gauss mode, the crystal birefringence induces an astigmatic effect in the signal beam that prevents the resonance of such mode.

  5. Non-paraxial Elliptical Gaussian Beam

    Institute of Scientific and Technical Information of China (English)

    WANG Zhaoying; LIN Qiang; NI Jie

    2001-01-01

    By using the methods of Hertz vector and angular spectrum transormation, the exact solution of non-paraxial elliptical Gaussion beam with general astigmatism based on Maxwell′s equations is obtained. We discussed its propagation characteristics. The results show that the orientation of the elliptical beam spot changes continuously as the beam propagates through isotropic media. Splitting or coupling of beam spots may occur for different initial spot size. This is very different from that of paraxial elliptical Gaussian beam.

  6. Visual outcomes after implantation of a novel refractive toric multifocal intraocular lens

    Directory of Open Access Journals (Sweden)

    Talita Shimoda

    2014-04-01

    Full Text Available Purpose: To assess the postoperative outcomes of a novel toric multifocal in traocular lens (IOL in patients with cataract and corneal astigmatism. Methods: This prospective nonrandomized study included patients with cataract, corneal astigmatism, and a motivation for spectacle independence. In all patients, a Rayner M-flex® T toric IOL was implanted in the capsular bag. Three months after surgery, the distance, intermediate, and near visual acuities; spherical equivalent; residual refractive astigmatism; defocus curve; and contrast sensitivity were evaluated. A patient satisfaction and visual phenomena questionnaire was administered to all patients. Results: Thirty-four eyes of 18 patients were included in this study. Three months after surgery, the mean corrected distance visual acuity (logMAR was 0.00 ± 0.08 at 6 m, 0.20 ± 0.09 at 70 cm, and 0.08 ± 0.11 at 40 cm. Uncorrected distance vision acuity was 20/40 or better in 100% eyes. The preoperative mean refractive cylinder (RC was -2.19 (SD: ± 0.53. After a 3-month follow-up, the average RC was -0.44 D (SD: ± 0.27; p<0.001. Contrast sensitivity levels were high. At the last follow-up, 87.5% patients were spectacle-independent for near, intermediate, and distance vision, and approximately 44% patients reported halos and glare. Conclusion: Toric multifocal IOL implantation in patients with cataract and corneal astigmatism using the Rayner M-flex® T toric IOL was a simple, safe, and accurate option. This technology provides surgeons with a feasible option for meeting patient expectations of an enhanced lifestyle resulting from decreased spectacle dependence.

  7. Is Noncycloplegic Photorefraction Applicable for Screening Refractive Amblyopia Risk Factors?

    Directory of Open Access Journals (Sweden)

    Zhale Rajavi

    2012-01-01

    Full Text Available Purpose: To compare the accuracy of noncycloplegic photorefraction (NCP with that of cycloplegic refraction (CR for detecting refractive amblyopia risk factors (RARFs and to determine cutoff points. Methods: In this diagnostic test study, right eyes of 185 children (aged 1 to 14 years first underwent NCP using the PlusoptiX SO4 photoscreener followed by CR. Based on CR results, hyperopia (≥ +3.5 D, myopia (≥ -3 D, astigmatism (≥ 1.5 D, and anisometropia (≥ 1.5 D were set as diagnostic criteria based on AAPOS guidelines. The difference in the detection of RARFs by the two methods was the main outcome measure. Results: RARFs were present in 57 (30.8% and 52 (28.1% of cases by CR and NCP, respectively, with an 89.7% agreement. In contrast to myopia and astigmatism, mean spherical power in hyperopic eyes was significantly different based on the two methods (P < 0.001, being higher with CR (+5.96 ± 2.13 D as compared to NCP (+2.37 ± 1.36 D. Considering CR as the gold standard, specificities for NCP exceeded 93% and sensitivities were also acceptable (≥ 83% for myopia and astigmatism. Nevertheless, sensitivity of NCP for detecting hyperopia was only 45.4%. Using a cutoff point of +1.87 D, instead of +3.5 D, for hyperopia, sensitivity of NCP was increased to 81.8% with specificity of 84%. Conclusion: NCP is a relatively accurate method for detecting RARFs in myopia and astigmatism. Using an alternative cutoff point in this study, NCP may be considered an acceptable device for detecting hyperopia as well.

  8. Comparison of Anterior Segment Measurements with Scheimpflug/Placido Photography-Based Topography System and IOLMaster Partial Coherence Interferometry in Patients with Cataracts.

    Science.gov (United States)

    Huang, Jinhai; Liao, Na; Savini, Giacomo; Bao, Fangjun; Yu, Ye; Lu, Weicong; Hu, Qingjie; Wang, Qinmei

    2014-01-01

    Purpose. To assess the consistency of anterior segment measurements obtained using a Sirius Scheimpflug/Placido photography-based topography system (CSO, Italy) and IOLMaster partial coherence interferometry (Carl Zeiss Meditec, Germany) in eyes with cataracts. Methods. A total of 90 eyes of 90 patients were included in this prospective study. The anterior chamber depth (ACD), keratometry (K), corneal astigmatism axis, and white to white (WTW) values were randomly measured three times with Sirius and IOLMaster. Concordance between them was assessed by calculating 95% limits of agreement (LoA). Results. The ACD and K taken with the Sirius were statistically significantly higher than that taken with the IOLMaster; however, the Sirius significantly underestimated the WTW values compared with the IOLMaster. Good agreement was found for Km and ACD measurements, with 95% LoA of -0.20 to 0.54 mm and -0.16 to 0.34 mm, respectively. Poor agreement was observed for astigmatism axis and WTW measurements, as the 95% LoA was -23.96 to 23.36° and -1.15 to 0.37 mm, respectively. Conclusion. With the exception of astigmatism axis and WTW, anterior segment measurements taken by Sirius and IOLMaster devices showed good agreement and may be used interchangeably in patients with cataracts. PMID:25400939

  9. Comparison of Anterior Segment Measurements with Scheimpflug/Placido Photography-Based Topography System and IOLMaster Partial Coherence Interferometry in Patients with Cataracts

    Directory of Open Access Journals (Sweden)

    Jinhai Huang

    2014-01-01

    Full Text Available Purpose. To assess the consistency of anterior segment measurements obtained using a Sirius Scheimpflug/Placido photography-based topography system (CSO, Italy and IOLMaster partial coherence interferometry (Carl Zeiss Meditec, Germany in eyes with cataracts. Methods. A total of 90 eyes of 90 patients were included in this prospective study. The anterior chamber depth (ACD, keratometry (K, corneal astigmatism axis, and white to white (WTW values were randomly measured three times with Sirius and IOLMaster. Concordance between them was assessed by calculating 95% limits of agreement (LoA. Results. The ACD and K taken with the Sirius were statistically significantly higher than that taken with the IOLMaster; however, the Sirius significantly underestimated the WTW values compared with the IOLMaster. Good agreement was found for Km and ACD measurements, with 95% LoA of −0.20 to 0.54 mm and −0.16 to 0.34 mm, respectively. Poor agreement was observed for astigmatism axis and WTW measurements, as the 95% LoA was −23.96 to 23.36° and −1.15 to 0.37 mm, respectively. Conclusion. With the exception of astigmatism axis and WTW, anterior segment measurements taken by Sirius and IOLMaster devices showed good agreement and may be used interchangeably in patients with cataracts.

  10. Chirped microlens arrays for diode laser circularization and beam expansion

    Science.gov (United States)

    Schreiber, Peter; Dannberg, Peter; Hoefer, Bernd; Beckert, Erik

    2005-08-01

    Single-mode diode lasers are well-established light sources for a huge number of applications but suffer from astigmatism, beam ellipticity and large manufacturing tolerances of beam parameters. To compensate for these shortcomings, various approaches like anamorphic prism pairs and cylindrical telescopes for circularization as well as variable beam expanders based on zoomed telescopes for precise adjustment of output beam parameters have been employed in the past. The presented new approach for both beam circularization and expansion is based on the use of microlens arrays with chirped focal length: Selection of lenslets of crossed cylindrical microlens arrays as part of an anamorphic telescope enables circularization, astigmatism correction and divergence tolerance compensation of diode lasers simultaneously. Another promising application of chirped spherical lens array telescopes is stepwise variable beam expansion for circular laser beams of fiber or solid-state lasers. In this article we describe design and manufacturing of beam shaping systems with chirped microlens arrays fabricated by polymer-on-glass replication of reflow lenses. A miniaturized diode laser module with beam circularization and astigmatism correction assembled on a structured ceramics motherboard and a modulated RGB laser-source for photofinishing applications equipped with both cylindrical and spherical chirped lens arrays demonstrate the feasibility of the proposed system design approach.

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

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    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.

  12. First-order design of off-axis reflective ophthalmic adaptive optics systems using afocal telescopes

    Science.gov (United States)

    Gómez-Vieyra, Armando; Dubra, Alfredo; Williams, David R.; Malacara-Hernández, Daniel

    2009-09-01

    Scanning laser ophthalmoscopes (SLOs) and optical coherence tomographs are the state-of-the-art retinal imaging instruments, and are essential for early and reliable diagnosis of eye disease. Recently, with the incorporation of adaptive optics (AO), these instruments have started to deliver near diffraction-limited performance in both humans and animal models, enabling the resolution of the retinal ganglion cell bodies, their processes, the cone photoreceptor and the retinal pigment epithelial cells mosaics. Unfortunately, these novel instruments have not delivered consistent performance across human subjects and animal models. One of the limitations of current instruments is the astigmatism in the pupil and imaging planes, which degrades image quality, by preventing the wavefront sensor from measuring aberrations with high spatial content. This astigmatism is introduced by the sequence of off-axis reflective elements, typically spherical mirrors, used for relaying pupil and imaging planes. Expressions for minimal astigmatism on the image and pupil planes in off-axis reflective afocal telescopes formed by pairs of spherical mirrors are presented. The formulas, derived from the marginal ray fans equation, are valid for small angles of incidence (systems. An example related to this last application is discussed.

  13. Refractive errors in Cameroonians diagnosed with complete oculocutaneous albinism

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    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

  14. Visual and Refractive Outcomes after Cataract Surgery with Implantation of a New Toric Intraocular Lens

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    Cinzia Mazzini

    2013-06-01

    Full Text Available Purpose: The aim of this study was to evaluate and report the visual, refractive and aberrometric outcomes of cataract surgery with implantation of the new aspheric Tecnis ZCT toric intraocular lens (IOL in eyes with low to moderate corneal astigmatism. Methods: We conducted a prospective study of 19 consecutive eyes of 17 patients (mean age: 78 years with a visually significant cataract and moderate corneal astigmatism [higher than 1 diopter (D] undergoing cataract surgery with implantation of the aspheric Tecnis ZCT toric IOL (Abbott Medical Optics. Visual, refractive and aberrometric changes were evaluated during a 6-month follow-up. Ocular aberrations as well as IOL rotation were evaluated by means of the OPD-Station II (Nidek. Results: The six-month postoperative spherical equivalent and power vector components of the refractive cylinder were within ±0.50 D in all eyes (100%. Postoperative logMAR uncorrected and corrected distance visual acuities (UDVA/CDVA were 0.1 (about 20/25 or better in almost all eyes (94.74%. The mean logMAR CDVA improved significantly from 0.41 ± 0.23 to 0.02 ± 0.05 (p Conclusion: Cataract surgery with implantation of the aspheric Tecnis ZCT IOL is a predictable and effective procedure for visual rehabilitation in eyes with cataract and low to moderate corneal astigmatism, providing an excellent postoperative ocular optical quality.

  15. A STUDY ON PREVALENCE OF REFRACTIVE ERRORS AMONG 5-16 YEARS RURAL CHILDREN IN CHANDRAGIRI, CHITTOOR DISTRICT, ANDHRA PRADESH

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    Krishna Murthy

    2014-09-01

    Full Text Available BACKGROUND: Uncorrected refractive errors are a major cause of low vision and even blindness. The refractive errors can be easily diagnosed and corrected by effective screening programmes. The uncorrected refractive errors in children have a definite impact in adversely affecting the learning capacity and scholastic performance. MATERIAL & METHODS: This Cross sectional was conducted from July to December 2013 among 1412 children aged 5-16 years residing in Chandragiri rural area, Chittoor District, Andhra Pradesh. Visual acuity was assessed using Snellen’s chart under standard illumination while detailed eye examination among the suspected cases was done by an ophthalmologist including detailed anterior segment evaluation, ocular motility, radioscopy and auto refraction under 2% homatropine cycloplegic refraction. RESULTS: The prevalence of refractive errors was found to be 7.4% among the study children (out of which 6.1% undiagnosed. Simple myopia was found in 2.4% children while astigmatism (both simple and compound combined was found in around 2.7% children. It was found that the proportion of myopia increased with age being lowest in 5-7 years (0.0% and highest in 14-16 age group (4.0%. The proportion of astigmatism also was found to be lowest in 5-7 age group (0.0% and higher in 11-13 age group and 14-16 age group (4.0% each However, the differences were not statistically significant (P=0.32; NS. The prevalence of myopia was found to be slightly higher in males (2.7% than in females (2.1% while that of astigmatism was found to be higher in females (3.1% than in males (2.3%. However the differences were not statistically significant (P=0.43; NS. A similar prevalence of refractive errors was found in Bangalore and New Delhi while lower and higher prevalence was reported elsewhere. Myopia and astigmatism are the common disorders in several Indian studies including the present study while African studies found myopia to be less common

  16. Small Incision Cataract Surgery (SICS with Clear Corneal Incision and SICS with Scleral Incision – A Comparative Study

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    Md Shafiqul Alam

    2014-01-01

    Full Text Available Background: Age related cataract is the leading cause of blindness and visual impairment throughout the world. With the advent of microsurgical facilities simple cataract extraction surgery has been replaced by small incision cataract surgery (SICS with posterior chamber intra ocular lens implant, which can be done either with clear corneal incision or scleral incision. Objective: To compare the post operative visual outcome in these two procedures of cataract surgery. Materials and method: This comparative study was carried out in the department of Ophthalmology, Delta Medical College & Hospital, Dhaka, Bangladesh, during the period of January 2010 to December 2012. Total 60 subjects indicated for age related cataract surgery irrespective of sex with the age range of 40-80 years with predefined inclusion and exclusion criteria were enrolled in the study. Subjects were randomly and equally distributed in 2 groups; Group A for SICS with clear corneal incision and group B for SICS with scleral incision. Post operative visual out come was evaluated by determining visual acuity and astigmatism in different occasions and was compared between groups. Statistical analysis was done by SPSS for windows version12. Results: The highest age incidence (43.3% was found between 61 to 70 years of age group. Among study subjects 40 were male and 20 were female. Preoperative visual acuity and astigmatism were evenly distributed between groups. Regarding postoperative unaided visual outcome, 6/12 or better visual acuity was found in 19.98% cases in group A and 39.6% cases in group B at 1st week. At 6th week 6/6 vision was found in 36.3% in Group A and 56.1% in Group B and 46.2% in group A and 66% in group B without and with correction respectively. With refractive correction, 6/6 vision was attained in 60% subjects of group A and 86.67% of group B at 8th week. Post operative visual acuity was statistically significant in all occasions. Postoperative astigmatism of

  17. Refractive status of primary school children in Mopani district, Limpopo Province, South Africa

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    R.G. Mabaso

    2006-01-01

    Full Text Available This article reports part of the findings of a study carried out to determine the causes, prevalence,  and  distribution  of  ocular  dis-orders  among  rural  primary  school  children in  Mopani  district  of  Limpopo  Province, South Africa. Three hundred and eighty eight children  aged  8  to  15  years  were  randomly selected from five randomly selected schools. Non-cycloplegic retinoscopy and auto-refrac-tion were performed on each child. The preva-lence of hyperopia, myopia, and astigmatism was  73.1%,  2.5%  and  31.3%  respective-ly.  Hyperopia  (Nearest  spherical  equivalent power (FNSE ranged from +0.75 to +3.50 D for the right and left eyes with means of +1.05 ±  0.35  D  and  +1.08  ±  0.34  D  respectively. Myopia (FNSE ranged from –0.50 to –1.75 D for the right eye and –0.50 to –2.25 D for the left eye with means of –0.75 ± 0.55 D and –0.93 ± 0.55 D respectively. Regression model for myopia, shows that age had an odds ratio of  1.94  (1.15  to  3.26,  indicating  a  signifi-cant increased risk of myopia with increasing age.  Correcting  cylinders  for  the  right  eyes ranged from –0.25 to –4.50 D (mean = −0.67 ± 0.47 D and for the left eyes from –0.25 to –2.50 D (mean = −0.60 ± 0.30 D. With-the-rule  (WTR  astigmatism  (66.5%  was  more common, followed by against-the-rule (ATR astigmatism (28.1% and oblique (OBL astig-matism  (5.4%.  With-the-rule  astigmatism was  more  common  in  females  than  males; ATR astigmatism and OBL astigmatism were common in males. Regular vision screening programmes,  appropriate  referral  and  vision correction  in  primary  schools  in  Mopani district  are  recommended  in  order  to  elimi-nate  refractive  errors  among  the  children.

  18. Design of modified Czerny-Turner spectral imaging system with wide spectral region%改进的宽谱段车尔尼-特纳光谱成像系统设计

    Institute of Scientific and Technical Information of China (English)

    薛庆生; 陈伟

    2012-01-01

    A modified Czerny-Turner spectral imaging system was developed based on aberration theory to minimize the large astigmatism in classical Czerny-Turner spectrometers. The astigmatism from a plane grating placed in the divergent light beam was used to compensate the astigmatism from an objective lens. The broadband astigmatism corrected simultaneously conditions were deduced, and the a-stigmatism was corrected in a wide spectral region. The principle and method of astigmatism correction were analyzed in detail, and the initial parameter computing was programed. As an example,a Czerny-Turner imaging spectral system operating in 540 - 780 nm was designed. The ray tracing and optimization for the spectral imaging system were performed with ZEMAX-EE software. The analyzed results demonstrate that the total field-of-view modulation transfer function is higher than 0. 52 in the whole working spectra. The system shows good imaging quality due to the astigmatism to be corrected in the wide spectral region synchronously. Obtained results prove the feasibility of the modified method.%针对传统的车尔尼-特纳光谱仪像散较大的缺点,基于像差理论,提出了一种改进的车尔尼-特纳光谱成像系统.将平面光栅置于发散光中,利用平面光栅产生的像散来补偿物镜产生的像散.推导出了宽谱段像散同时校正条件,实现了宽谱段像散的同时校正.具体分析了像差校正的原理和方法,编制了初始结构快速计算程序.作为实例,设计了一个谱段为540~780 nm的宽谱段像散同时校正车尔尼-特纳光谱成像系统,利用光学设计软件ZEMAX-EE对该光谱成像系统进行了光线追迹和优化设计,并对设计结果进行了分析.结果表明,全视场调制传递函数在整个工作波段均达到0.52以上,实现了宽谱段像散的同时校正,并获得了良好的成像质量,满足了设计指标要求,结果也证实了所提出的改进方法是可行的.

  19. Single-segment and double-segment INTACS for post-LASIK ectasia.

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    Hassan Hashemi

    2014-09-01

    Full Text Available The objective of the present study was to compare single segment and double segment INTACS rings in the treatment of post-LASIK ectasia. In this interventional study, 26 eyes with post-LASIK ectasia were assessed. Ectasia was defined as progressive myopia regardless of astigmatism, along with topographic evidence of inferior steepening of the cornea after LASIK. We excluded those with a history of intraocular surgery, certain eye conditions, and immune disorders, as well as monocular, pregnant and lactating patients. A total of 11 eyes had double ring and 15 eyes had single ring implantation. Visual and refractive outcomes were compared with preoperative values based on the number of implanted INTACS rings. Pre and postoperative spherical equivalent were -3.92 and -2.29 diopter (P=0.007. The spherical equivalent decreased by 1 ± 3.2 diopter in the single-segment group and 2.56 ± 1.58 diopter in the double-segment group (P=0.165. Mean preoperative astigmatism was 2.38 ± 1.93 diopter which decreased to 2.14 ± 1.1 diopter after surgery (P=0.508; 0.87 ± 1.98 diopter decrease in the single-segment group and 0.67 ± 1.2 diopter increase in the double-segment group (P=0.025. Nineteen patients (75% gained one or two lines, and only three, who were all in the double-segment group, lost one or two lines of best corrected visual acuity. The spherical equivalent and vision significantly decreased in all patients. In these post-LASIK ectasia patients, the spherical equivalent was corrected better with two segments compared to single segment implantation; nonetheless, the level of astigmatism in the single-segment group was significantly better than that in the double-segment group.

  20. Ring-field TMA for PRISMA: theory, optical design, and performance measurements

    Science.gov (United States)

    Calamai, Luciano; Barsotti, Stefano; Fossati, Enrico; Formaro, Roberto; Thompson, Kevin P.

    2015-09-01

    PRISMA (PRecursore IperSpettrale della Missione Applicativa) Hyperspectral Payload is an Electro-Optical instrument developed in Selex ES for the dedicated ASI (Italian Space Agency) mission for Earth observation. The performance requirements for this mission are stringent and have led to an instrument design that is based on a Ring-Field Three Mirror Anastigmat (Ring-Field TMA), a two channel prism dispersion based spectrometer (VNIR and SWIR), and a Panchromatic Camera. The Ring-Field TMA contains three mirrors (two conics and one conic with some higher order correction). Exceptional performance has been achieved by not only introducing 3rd order astigmatism to balance the 5th astigmatism at the ring field zone as is traditional in an Offner-type design but, additionally, 3rd order coma has been controlled to align the balance of the linear and field cubic coma terms at the same ring field zone. The predicted wavefront performance of the design over the field of view will be highlighted. An assembly and alignment procedure for the Ring-Field TMA has been developed from the results of the sensitivity and tolerances analysis. The tilt and decenter sensitivity of the design form is nearly exclusively determined by 3rd order binodal astigmatism. The nodal position is linear with perturbation, which greatly simplifies the decisions on alignment compensators. The manufactured mirrors of the Ring-Field TMA have been aligned at Selex ES and as will be reported the preliminary results in terms of optical quality are in good agreement with the predicted as-built performance, both on-axis and in the field.

  1. The effect of treatment on different refractive amblyopia children%不同屈光状态弱视儿童治疗效果的临床分析

    Institute of Scientific and Technical Information of China (English)

    孙鹏飞; 肖瑛; 陈国玲; 侯静; 马广凤

    2014-01-01

    目的:探讨不同屈光状态儿童弱视治疗的临床效果。方法回顾弱视儿童86例(150眼),其中远视性弱视77眼,近视性弱视38眼,混合散光性弱视35眼,比较评价三组治疗效果。结果远视性弱视组治愈68眼(88.3%),近视性弱视治愈24眼(63.2%),混合散光性弱视治愈11眼(31.5%),三组治愈率有明显差异,P<0.05。结论远视性弱视治疗效果明显好于近视性和混合散光性弱视。%Objective To evaluate the efficacy of treatment on amblyopia children with different refractive states. Methods Total of 86 cases (150eyes) of amblyopia children, 77eyes with hyperopic amblyopia, 38 eyes with my-opic amblyopia and 35 eyes with mixed astigmatism amblyopia were treated and the effect were analyzed. Results 68 eyes (88.3%) of hyperopic amblyopia were cured, 24 eyes (63.2%) of myopic amblyopia were cured, 11 eyes (31.5%) of mixed astigmatism amblyopica were cured. There were significant difference of cured ratio among 3 groups, P<0.05. Conclusions The efficiency of treatment on hyperemia amblyopic is better than myopic amblyopia and mixed astigma-tism amblyopia.

  2. Congenital glaucoma in siblings

    OpenAIRE

    Cont, M; Fontijn, J; Michels, R; Arlettaz, R.

    2011-01-01

    We report on a full term female neonate delivered by cesarean section at 37 2/7 weeks of gestation. The mother, a 28-year-old G2/P2, had a history of autoimmune thrombocytopenia and diabetes mellitus type I. She also has astigmatism and the father is myopic. There is no history of consanguinity. The first child, a son, was born at term and discharged home considered to be healthy. However, the parents noticed corneal clouding, and brought their baby to the pediatrician who confirmed cornea...

  3. General analysis of aplanatic cassegrain, gregorian, and schwarzschild telescopes.

    Science.gov (United States)

    Wetherell, W B; Rimmer, M P

    1972-12-01

    The properties of two-conic reflecting aplanats are analyzed and discussed on the basis of third order aberration theory. Techniques for designing infinite conjugate two mirror aplanats and computing their image properties are developed. The secondary mirror alignment characteristics of Ritchey-Chrétien and aplanatic Gregorian telescopes are examined and neutral point locations defined. Design configurations corrected for a third Seidel aberration (astigmatism, image curvature, or distortion) are identified and their properties discussed. The properties of Ritchey-Chrétien and aplanatic Gregorian telescopes are compared.

  4. ENGLISH ABSTRACTS OF CURRENT CHINESE MEDICAL LITERATURE

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@Excimer laser in situ keratomileusis for severe ametropia after penetrating keratoplasty LU Wenxiu, LI Zhihui, QI Ying, et al.Department of Ophthalmology, Beijing Tongren Hospital,Beijiing 100730, ChinaChin J Ophthalmol 2001; 37: 94-97. Objective To evaluate the effects of excimer laser in situ keratomileusis in correcting severe myopia and astigmatism after penetrating keratoplasty.Methods Excimer laser in situ keratomileusis was performed on ten eyes of ten patients to correct high ametropia in cases having previously undergone penetrating

  5. Optical modeling and physical performances evaluations for the JT-60SA ECRF antenna

    Energy Technology Data Exchange (ETDEWEB)

    Platania, P., E-mail: platania@ifp.cnr.it; Figini, L.; Farina, D.; Micheletti, D.; Moro, A.; Sozzi, C. [Istituto di Fisica del Plasma “P. Caldirola”, Consiglio Nazionale delle Ricerche, Via R. Cozzi 53, 20125, Milano (Italy); Isayama, A.; Kobayashi, T.; Moriyama, S. [Japan Atomic Energy Agency, 801-1 Mukoyama, Naka, Ibaraki 311-0193 (Japan)

    2015-12-10

    The purpose of this work is the optical modeling and physical performances evaluations of the JT-60SA ECRF launcher system. The beams have been simulated with the electromagnetic code GRASP® and used as input for ECCD calculations performed with the beam tracing code GRAY, capable of modeling propagation, absorption and current drive of an EC Gaussion beam with general astigmatism. Full details of the optical analysis has been taken into account to model the launched beams. Inductive and advanced reference scenarios has been analysed for physical evaluations in the full poloidal and toroidal steering ranges for two slightly different layouts of the launcher system.

  6. Inflammatory Biomarkers Profile as Microenvironmental Expression in Keratoconus

    Science.gov (United States)

    Jonescu-Cuypers, Christian; Nicula, Cristina; Voinea, Liliana-Mary

    2016-01-01

    Keratoconus is a degenerative disorder with progressive stromal thinning and transformation of the normal corneal architecture towards ectasia that results in decreased vision due to irregular astigmatism and irreversible tissue scarring. The pathogenesis of keratoconus still remains unclear. Hypotheses that this condition has an inflammatory etiopathogenetic component apart from the genetic and environmental factors are beginning to escalate in the research domain. This paper covers the most relevant and recent published papers regarding the biomarkers of inflammation, their signaling pathway, and the potentially new therapeutic options in keratoconus. PMID:27563164

  7. [Wave front aberrations -- practical conclusions in eye with Restor 3+ difractive multifocal lens].

    Science.gov (United States)

    Staicu, Corina; Moraru, Ozana; Moraru, Cristian

    2014-01-01

    Implantation of multifocal intraocular lenses has become a rutine nowadays, but achieving good visual results requires a perfect intraoperative technique and also an adequate preoperative selection of the patients. We analysed the wave front aberrations (spherical aberations, coma and astigmatism) in the eyes implanted with ReStor + 3 IOL, and we realized some clinical correlations of these aberations with the pupil diameter in scotopic and fotopic conditions, kappa angle, IOL centration, residual refraction errors postoperatively. Taking into account the causes of postoperative high order aberration will allow the surgeon to make a good selection of the patiens and to a higher degree of satisfaction of both sides.

  8. 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.

  9. Wavefront aberration statistics in normal eye populations: are they well described by the Kolmogorov model?

    Science.gov (United States)

    Pailos, Eliseo; Bará, Salvador

    2014-06-01

    This Letter studies the statistics of wavefront aberrations in a sample of eyes with normal vision. Methods relying on the statistics of the measured wavefront slopes are used, not including the aberration estimation stage. Power-law aberration models, an extension of the Kolmogorov one, are rejected by χ2-tests performed on fits to the slope structure function data. This is due to the large weight of defocus and astigmatism variations in normal eyes. Models of only second-order changes are not ruled out. The results are compared with previous works in the area.

  10. 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

  11. Double-phase-conjugate mirror in CdTe:V with elimination of conical diffraction at 1.54 microm.

    Science.gov (United States)

    Martel, G; Wolffer, N; Moisan, J Y; Gravey, P

    1995-04-15

    We have fabricated a double-phase-conjugate mirror (DPCM) in a single crystal of vanadium-doped cadmium telluride. Because of the high gain in the near-infrared region, a DPCM is possible at a telecommunication wavelength of 1.54 microm in this material. Experimental and theoretical thresholds for the DPCM are compared, and an experimental diffraction efficiency of 7.4% is reported. Conical diffraction has been eliminated by the method of cylindrical lenses. We propose to use this astigmatic configuration to enhance the capacity of interconnections between fibers with a single crystal in a vector-matrix architecture. PMID:19859380

  12. New Gapless COS G140L Mode Proposed for Background-Limited Far-UV Observations

    CERN Document Server

    Redwine, Keith; Fleming, Brian; France, Kevin; Zheng, Wei; Osterman, Steven; Howk, J Christopher; Anderson, Scott F; Gaensicke, Boris T

    2016-01-01

    Here we describe the observation and calibration procedure for a new G140L observing mode for the Cosmic Origins Spectrograph (COS) aboard the Hubble Space Telescope (HST). This mode, CENWAV = 800, is designed to move the far-UV band fully onto the Segment A detector, allowing for more e cient ob- servation and analysis by simplifying calibration management between the two channels, and reducing the astigmatism in this wavelength region. We also de- scribe some of the areas of scientific interest for which this new mode will be especially suited.

  13. Using aberration test patterns to optimize the performance of EUV aerial imaging microscopes

    Energy Technology Data Exchange (ETDEWEB)

    Mochi, Iacopo; Goldberg, Kenneth A.; Miyakawa, Ryan; Naulleau, Patrick; Han, Hak-Seung; Huh, Sungmin

    2009-06-16

    The SEMATECH Berkeley Actinic Inspection Tool (AIT) is a prototype EUV-wavelength zoneplate microscope that provides high quality aerial image measurements of EUV reticles. To simplify and improve the alignment procedure we have created and tested arrays of aberration-sensitive patterns on EUV reticles and we have compared their images collected with the AIT to the expected shapes obtained by simulating the theoretical wavefront of the system. We obtained a consistent measure of coma and astigmatism in the center of the field of view using two different patterns, revealing a misalignment condition in the optics.

  14. Adaptive compensation of lower order thermal aberrations in concave-convex power oscillators under variable pump conditions

    Science.gov (United States)

    Jackel, Steven M.; Moshe, Inon

    2000-09-01

    A Nd:Cr:GSGG concave-convex power oscillator was developed that utilized both an adaptive mirror comprised of spherical and cylindrical optical elements together with a Faraday rotator to dynamically eliminate lower order aberrations (thermal focusing, astigmatism, and bipolar focusing). An adaptively controlled collimating lens corrected for shifts in the mode-waist position. The addition of a polarizer and a reentrant mirror totally eliminated thermal birefringence losses. The techniques developed are attractive in any solid state laser that must work under changing pump power conditions.

  15. GANAS: A HYBRID ANASTIGMATIC ASPHERICAL PRIME-FOCUS CORRECTOR

    Directory of Open Access Journals (Sweden)

    F. Della Prugna

    2009-01-01

    Full Text Available The Cassegrain-Coud 1 meter Car to the focal plane of the primary f/5 l Zeiss telescope at the Venezuelan National Astronomical Observatory uses six optical elements. Removal of the secondary convex mirror gives accessspheroidal mirror, but spherical aberration, coma, astigmatism and eld curvature severely hamper its imaging capabilities. In order to carry out prime-focus imaging, we designed and manufactured a corrector group, called GAnAs, to minimize these aberrations over a circular eld of 300. The corrector group is a hybrid con guration with two thin aspherical 4th-order plates and a meniscus lens.

  16. Orbital angular momentum of the laser beam and the second order intensity moments

    Institute of Scientific and Technical Information of China (English)

    高春清[1; 魏光辉[2; HorstWeber[3

    2000-01-01

    From the wave equation of a generalized beam the orbital angular momentum is studied. It is shown that the orbital angular momentum exists not only in the Laguerre-Gaussian beam, but in any beam with an angular-dependent structure. By calculating the second order intensity moments of the beam the relation between the orbital angular momentum and the second order moments 〈xθy〉, 〈yθx〉 is given. As an example the orbital angular momentum of the general astigmatic Gaussian beam is studied.

  17. Orbital angular momentum of the laser beam and the second order intensity moments

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    From the wave equation of a generalized beam the orbital angular momentum is studied. It is shown that the orbital angular momentum exists not only in the Laguerre_Gaussian beam,but in any beam with an angular_dependent structure. By calculating the second order intensity moments of the beam the relation between the orbital angular momentum and the second order moments 〈xθy〉, 〈yθx〉 is given. As an example the orbital angular momentum of the general astigmatic Gaussian beam is studied.

  18. Optical Aberrations and Wavefront

    Directory of Open Access Journals (Sweden)

    Nihat Polat

    2014-08-01

    Full Text Available The deviation of light to create normal retinal image in the optical system is called aberration. Aberrations are divided two subgroup: low-order aberrations (defocus: spherical and cylindrical refractive errors and high-order aberrations (coma, spherical, trefoil, tetrafoil, quadrifoil, pentafoil, secondary astigmatism. Aberrations increase with aging. Spherical aberrations are compensated by positive corneal and negative lenticular spherical aberrations in youth. Total aberrations are elevated by positive corneal and positive lenticular spherical aberrations in elderly. In this study, we aimed to analyze the basic terms regarding optic aberrations which have gained significance recently. (Turk J Ophthalmol 2014; 44: 306-11

  19. General analysis of aplanatic cassegrain, gregorian, and schwarzschild telescopes.

    Science.gov (United States)

    Wetherell, W B; Rimmer, M P

    1972-12-01

    The properties of two-conic reflecting aplanats are analyzed and discussed on the basis of third order aberration theory. Techniques for designing infinite conjugate two mirror aplanats and computing their image properties are developed. The secondary mirror alignment characteristics of Ritchey-Chrétien and aplanatic Gregorian telescopes are examined and neutral point locations defined. Design configurations corrected for a third Seidel aberration (astigmatism, image curvature, or distortion) are identified and their properties discussed. The properties of Ritchey-Chrétien and aplanatic Gregorian telescopes are compared. PMID:20119413

  20. A first-order treatment of aberrations in Cassegrainian and Gregorian antennas

    Science.gov (United States)

    Dragone, C.

    1982-05-01

    The decrease in aperture efficiency caused by small aberrations in a reflector antenna is determined. The important case of a Cassegrainian (or Gregorian) antenna with a feed placed in the vicinity of the focal point is treated in detail. For this case the various aberration components due to astigmatism, coma, etc., are derived explicitly, their effect on aperture efficiency is shown, and the conditions that optimize performance are given. The results are useful for the design of multibeam antennas in ground stations and satellites.

  1. A high performance laser diode transmitter for optical free space communication

    Science.gov (United States)

    Hildbebrand, U.; Ohm, G.; Wiesmann, Th.; Hildebrand, K.; Voit, E.

    1990-07-01

    For the ESA Semiconductor Intersatellite Link Experiment (SILEX), elements of the communication chain have been breadboarded. The electrooptical converter, called the laser diode transmitter package (LDTP), is described here. The requirements on the LDTP optical quality are deduced from the overall system requirements. The tolerable wavefront errors (WFE) and the stability of beam direction are most critical. Four breadboards have been assembled and tested. The very stringent requirements on WFE were surpassed, with a resulting rms value of 1/40 waves. In order to achieve this wavefront quality, the typical astigmatism of index-guided laser diodes (1-10 microns) had to be compensated by adjustable cylindrical lenses.

  2. Investigation of communication laser diodes for the SILEX project

    Science.gov (United States)

    Menke, Bodo; Loeffler, Roland

    1989-10-01

    The Semiconductor Intersatellite Laser Experiment (SILEX) will construct an optical communications link over a range of 45,000 km, using 0.8-micron AlGaAs laser diodes capable of transmitting 65 Mbit/s. Numerous single-stripe diode types were furnished by manufacturers and subjected to measurements to establish conformity with the required far-field pattern spectrum spread under QPPM-modulation, mode-hopping, astigmatism, and rms wavefront error (WFE); WFE is demonstrated to be strongly affected by the laser window's introduction of strong spherical aberration. Three laser types have been chosen for breadboarding and accelerated life tests.

  3. Selection strategy and reliability assessment for SILEX-communication laser diodes

    Science.gov (United States)

    Loeffler, Roland; Menke, Bodo

    1991-03-01

    Steps involved in the search for suitable laser diodes for Semiconductor laser Intersatellite Link EXperiment (SILEX) and evaluation of their capabilities in meeting qualification requirements are discussed. A baseline of the laser diode functional specifications is identified by synthesizing the SILEX system requirements and thereby predicting the desired diode characteristics. Samples of approximately 20 different laser diode types are submitted to comprehensive measurements of their characteristics, spectral widths, mode hopping behavior, far field patterns, wave front errors and astigmatisms under modulation. An evaluation program consisting of a conventional three temperature aging test and sensitivity and environmental tests is defined.

  4. Transferences of Purkinje systems

    Directory of Open Access Journals (Sweden)

    W. F. Harris

    2011-12-01

    Full Text Available The transferences of heterocentric astigmatic Purkinje systems are special: submatrices B and C, that is, the disjugacy and the divergence of the system, are symmetric and submatrix D (the divarication is the transpose of submatrix A (the dilation.  It is the primary purpose of this paper to provide a proof.  The paper also derives other relationships among the fundamental properties and compact expressions for the transference and optical axis locator of a Purkinje system. (S Afr Optom 2011 70(2 57-60

  5. Optical Design of Spaceborne Broadband Limb Sounder for Detecting Atmospheric Trace Gas%星载宽波段大气痕量气体临边探测仪光学设计

    Institute of Scientific and Technical Information of China (English)

    薛庆生

    2012-01-01

    In order to meet the urgent requirements of delecting atmospheric trace gas in limb observation geometry, an optical system of spaceborne broadband limb sounder for detecting atmospheric trace gas is designed. The system is an imaging spectrometer with the working wavelength band from 0. 3 μm to 0. 7 μm, and its full field of view is 2. 4% focal length is 120 mm, and the relative aperture is 1 : 6. To avoid the problems of the classical Czerny-Truncr spectrometer, such as low spatial resolution caused by large astigmatism, a modified Czerny-Turner spectrometer is designed, in which astigmatism can be corrected simultaneously in a wide band. By matching the modified Czerny-Turner spectrometer with a off-axis parabolic telescope,an examplc of limb sounder optical system is designed. Ray tracing, optimization and analysing are performed by ZEMAX software. The analyzed results demonstrate that the astigmatism is substantially corrected, and the MTF for different spectral band is more than 0. 69 which satisfies the pre-designed requirement and proves the feasibility of the astigmatism-correction method.%为满足大气痕量气体临边探测的迫切需求,克服传统Czerny-Turner光谱仪由于像散大导致空间分辨率低的缺点,设计了一种可以在宽波段内同时校正像散的改进型Czerny-Turner光谱仪,光谱范围为0.3~0.7μm,全视场角为2.4°,焦距为120 mm,相对孔径为1∶6.将离轴抛物面镜与改进型Czerny-Turner光谱仪匹配设计了一个临边探测仪光学系统并运用光学设计软件ZEMAX对临边探测仪光学系统进行了光线追迹和优化并对设计结果进行了分析,结果表明该系统的像散得到充分校正,光学系统在各个谱段的光学传递函数均达到0.69以上,完全满足设计指标要求,也证明了所提出的在宽波段内同时像散校正方法是可行的.

  6. Intraocular correction of high-degree ametropia using individual multifocal LentisMPlus IOL

    Directory of Open Access Journals (Sweden)

    I.S. Fedorova

    2013-03-01

    Full Text Available ABSTRACT Background. For surgical correction of high-degree ametropia aggravated with astigmatism the following options are available: excimer laser correction; phakic lens implantation; bioptika – a combination of ablating the transparent crystalline lens (ATL with implantation of multifocal toric diopter IOL of standard series and LASIK for the correction of a residual refractive error, ATL using 2 IOLs according to the Technology «Piggy Back»; additional meniscus IOL implantation «Add-On»; ATL with implantation of an individual multifocal toric IOL. Purpose. To show a possibility of intraocular correction of high ametropia aggravated with astigmatism using toric multifocal custom IOLs. Material and methods. We observed two patients: the first female patient, 39 years old with a diagnosis of OU: high myopia, compound myopic astigmatism, initial complicated cataract, moderate amblyopia, peripheral chorioretinal degeneration (PCRD. On admission the distance visual acuity was vis OD=0.01 sph (- 15.5 D cyl (- 2.5 D ax 0°=0.6; vis OS=0.01 sph (- 18.0 D cyl (- 2.5 D ax 0°=0.5. The second patient was a 35-year woman with a diagnosis of OU: high hyperopia, compound hyperopic astigmatism, moderate amblyopia. Distance visual acuity on admission was OD=0.03 sph (+ 8.0 D cyl (+ 1.5 D ax 95°=0.5; OS=0.03 sph (+ 8.0 D cyl (+ 0.75 D ax 75°=0.6. Individual multifocal toric IOLs were implanted in both patents after the removal of the lens phacoemulsification. All standard ophthalmic examinations were used as well as the ultrasound biomicroscopy (UBM. Results. In the follow-up: 6 months after the surgery in the first patient the uncorrected visual acuity (UCVA was far vis OD=0.6, vis OS=0.5, near vis OD=0.4, vis OS=0.5, middle distance vis OD=0.4, vis OS=0.4. The second patient 3 months after surgery had the UCVA far vis OD=0.5, vis OS=0.6, near vis OD=0.4, vis OS=0.5, middle distance vis OD=0.2, vis OS=0.3. The maximum possible distance visual acuity

  7. Fibrinous anterior uveitis following laser in situ keratomileusis

    Directory of Open Access Journals (Sweden)

    Parmar Pragya

    2009-01-01

    Full Text Available A 29-year-old woman who underwent laser in situ keratomileusis (LASIK for myopic astigmatism in both eyes presented with severe pain, photophobia and decreased visual acuity in the left eye eight days after surgery. Examination revealed severe anterior uveitis with fibrinous exudates in the anterior chamber, flap edema and epithelial bullae. Laboratory investigations for uveitis were negative and the patient required systemic and intensive topical steroids with cycloplegics to control the inflammation. This case demonstrates that severe anterior uveitis may develop after LASIK and needs prompt and vigorous management for resolution.

  8. Management of advanced corneal ectasias.

    Science.gov (United States)

    Maharana, Prafulla K; Dubey, Aditi; Jhanji, Vishal; Sharma, Namrata; Das, Sujata; Vajpayee, Rasik B

    2016-01-01

    Corneal ectasias include a group of disorders characterised by progressive thinning, bulging and distortion of the cornea. Keratoconus is the most common disease in this group. Other manifestations include pellucid marginal degeneration, Terrien's marginal degeneration, keratoglobus and ectasias following surgery. Advanced ectasias usually present with loss of vision due to high irregular astigmatism. Management of these disorders is difficult due to the peripheral location of ectasia and associated severe corneal thinning. Newer contact lenses such as scleral lenses are helpful in a selected group of patients. A majority of these cases requires surgical intervention. This review provides an update on the current treatment modalities available for management of advanced corneal ectasias. PMID:26294106

  9. Measuring the Orbital Angular Momentum of Electron Beams

    CERN Document Server

    Guzzinati, Giulio; Béché, Armand; Verbeeck, Jo

    2014-01-01

    The recent demonstration of electron vortex beams has opened up the new possibility of studying orbital angular momentum (OAM) in the interaction between electron beams and matter. To this aim, methods to analyze the OAM of an electron beam are fundamentally important and a necessary next step. We demonstrate the measurement of electron beam OAM through a variety of techniques. The use of forked holographic masks, diffraction from geometric apertures, diffraction from a knife-edge and the application of an astigmatic lens are all experimentally demonstrated. The viability and limitations of each are discussed with supporting numerical simulations.

  10. Generalised Hermite-Gaussian beams and mode transformations

    CERN Document Server

    Wang, Yi; Zhang, Yanfeng; Chen, Hui; Yu, Siyuan

    2016-01-01

    Generalised Hermite-Gaussian modes (gHG modes), an extended notion of Hermite-Gaussian modes (HG modes), are formed by the summation of normal HG modes with a characteristic function $\\alpha$, which can be used to unite conventional HG modes and Laguerre-Gaussian modes (LG modes). An infinite number of normalised orthogonal modes can thus be obtained by modulation of the function $\\alpha$. The gHG mode notion provides a useful tool in analysis of the deformation and transformation phenomena occurring in propagation of HG and LG modes with astigmatic perturbation.

  11. White light interferometry in amblyopic children--a pilot study.

    Science.gov (United States)

    Vernon, S A; Hardman-Lea, S; Rubinstein, M P; Snead, M P

    1990-01-01

    Interferometric acuity using the IRAS white light interferometer was compared with Snellen acuity in nine amblyopic children between the ages of five and nine years, and nine aged matched controls. All of the amblyopic eyes achieved better grating acuities than Snellen acuities. Fifty-seven per cent of the amblyopes with a best corrected Snellen acuity of 6/18 or less in their amblyopic eye, achieved grating acuities indistinguishable from normal. The hand held white light interferometer may have a role in the assessment of meridional amblyopia and in children with high astigmatic errors.

  12. Development of a universal toric intraocular lens calculator

    Science.gov (United States)

    Hjelmstad, David; Sayegh, Samir I.

    2014-02-01

    We present a method for calculating the ideal toric lens to implant in astigmatic patients following cataract surgery. We show that the online calculators provided by major toric IOL manufacturers are insufficient for both theoretical and practical reasons. We reveal important theoretical shortcomings in their approach, illustrated by a number of cases which demonstrate how the approach can lead to errors in lens selection. Our approach combines the spherical and cylindrical power calculations into one, and allows for lens data from any manufacturer to be used, eliminating the reliance on multiple programs.

  13. Phase and group velocity of focused, pulsed Gaussian beams in the presence and absence of primary aberrations

    International Nuclear Information System (INIS)

    This work presents a study on the phase- and group-velocity variations of focused, pulsed Gaussian beams during the propagation through the focal region along the optical axis. In the aberration-free case, it is discussed how the wavelength dependence of beam properties alters the group velocity, and how a chromatic aberration-like effect can arise even when focusing is performed with an element that does not have chromatic aberration. It is also examined what effects primary spherical aberration, astigmatism, coma, curvature of field and distortion, along with chromatic aberration, have on the phase- and group-velocity changes occurring during propagation through focus. (paper)

  14. Nano-Structuring of Solid Surface by EUV Ar8+ Laser

    International Nuclear Information System (INIS)

    The paper demonstrates our first attempt for “direct (i.e. ablation) patterning” of PMMA by pulse, high-current, capillary-discharge-pumped Ar8+ ion laser (λ = 46.9 nm). For focusing a long-focal spherical mirror (R = 2100 mm) covered by 14 double-layer Sc-Si coating was used. The ablated focal spots demonstrate not only that the energy of our laser is sufficient for such experiments, but also that the design of focusing optics must be more sophisticated: severe aberrations have been revealed - an irregular spot shape and strong astigmatism with astigmatic deference as large as 16 mm. In some cases, on the bottom of ablated spots a laser-induced periodic surface structure (LIPSS) has appeared. Finally, an illumination of the sample through quadratic hole 7.5x7.5 μm, standing in contact with PMMA substrate, has ablated from the surface a strongly developed 2D diffraction pattern (period in the centre ⁓125 nm). (author)

  15. A Handheld Open-Field Infant Keratometer (An American Ophthalmological Society Thesis)

    Science.gov (United States)

    Miller, Joseph M.

    2010-01-01

    Purpose: To design and evaluate a new infant keratometer that incorporates an unobstructed view of the infant with both eyes (open-field design). Methods: The design of the open-field infant keratometer is presented, and details of its construction are given. The design incorporates a single-ring keratoscope for measurement of corneal astigmatism over a 4-mm region of the cornea and includes a rectangular grid target concentric within the ring to allow for the study of higher-order aberrations of the eye. In order to calibrate the lens and imaging system, a novel telecentric test object was constructed and used. The system was bench calibrated against steel ball bearings of known dimensions and evaluated for accuracy while being used in handheld mode in a group of 16 adult cooperative subjects. It was then evaluated for testability in a group of 10 infants and toddlers. Results: Results indicate that while the device achieved the goal of creating an open-field instrument containing a single-ring keratoscope with a concentric grid array for the study of higher-order aberrations, additional work is required to establish better control of the vertex distance. Conclusion: The handheld open-field infant keratometer demonstrates testability suitable for the study of infant corneal astigmatism. Use of collimated light sources in future iterations of the design must be incorporated in order to achieve the accuracy required for clinical investigation. PMID:21212850

  16. Refractive status of medical students of mymensingh medical college.

    Science.gov (United States)

    Akhanda, A H; Quayum, M A; Siddiqui, N I; Hossain, M M

    2010-10-01

    This study is done to find out the refractive status of medical students of Mymensingh Medical College (MMC), Mymensingh, Bangladesh. They are of the age of 17-19 years. This is a nonrandom purposive cross sectional study done at late part of the November 2008. Visual acuity estimation, automated refraction, streak retinoscopy, fundoscopy using +78D volk lens were done according to the need of the cases. Out of 175 students 53.14% are emmetropic and 46.86% are ametropic, ametropia is nearly equal in both sexes (male 51.22%, female 48.78%). About all students are of highest academic attainment (GPA 5). About one quarter of the ametropic students (21.61%) are not using spectacles. Simple myopia (81.70%) and myopic astigmatism (18.30%) are the types of ametropia. Out of 67 simple myopic students 56 are of bilateral involvement and 11 are of unilateral involvement. There is similarity in the distribution of sex & refractive status in between general population & medical students of Bangladesh. Myopia and myopic astigmatism are prevalent among medical students. PMID:20956887

  17. Femtosecond laser-assisted deep anterior lamellar keratoplasty for keratoconus and keratectasia

    Institute of Scientific and Technical Information of China (English)

    Yan; Lu; Yu-Hua; Shi; Li-Ping; Yang; Yi-Rui; Ge; Xiang-Fei; Chen; Yan; Wu; Zhen-Ping; Huang

    2014-01-01

    ·AIM: To describe the initial outcomes and safety of femtosecond laser-assisted deep anterior lamellar keratoplasty(DALK) for keratoconus and post-LASIK keratectasia.·METHODS: In this non-comparative case series, 10 eyes of 9 patients underwent DALK procedures with a femtosecond laser(Carl Zeiss Meditec AG, Jena,Germany). Of the 9 patients, 7 had keratoconus and 2had post-LASIK keratectasia. A 500 kHz VisuMax femtosecond laser was used to perform corneal cuts on both donor and recipient corneas. The outcome measures were the uncorrected visual acuity(UCVA),best-corrected visual acuity(BCVA), corneal thickness,astigmatism, endothelial density count(EDC), and corneal power.·RESULTS: All eyes were successfully treated. Early postoperative evaluation showed a clear graft in all cases. Intraoperative complications included one case of a small Descemet’s membrane perforation.Postoperatively, there was one case of stromal rejection,one of loosened sutures, and one of wound dehiscence.A normal corneal pattern topography and transparency were restored, UCVA and BCVA improved significantly,and astigmatism improved slightly. There was no statistically significant decrease in EDC.· CONCLUSION: Our early results indicate that femtosecond laser-assisted deep anterior lamellar keratoplasty could improve UCVA and BCVA in patients with anterior corneal pathology. This approach shows promise as a safe and effective surgical choice in the treatment of keratoconus and post-LASIK keratectasia.

  18. Z(eff) profile measurement system with an optimized Czerny-Turner visible spectrometer in large helical device.

    Science.gov (United States)

    Zhou, H Y; Morita, S; Goto, M; Chowdhuri, M B

    2008-10-01

    Z(eff) measurement system using a visible spectrometer has been newly designed and constructed instead of an old interference filter system to eliminate line emissions from the signal and to measure the Z(eff) value in low-density plasmas. The system consists of the Czerny-Turner-type spectrometer with a charge-coupled device camera and 44 optical fibers vertical array. The spectrometer is equipped with an additional toroidal mirror for further reduction in the astigmatism in addition to a flat and two spherical mirrors and three gratings (110, 120, and 1200 grooves/mm) with 30 cm focal length. The images from 44 optical fibers can be detected without astigmatism in a wavelength range of 200-900 nm. Combination of the optical fiber (core diameter: 100 microm) with the lens (focal length: 30 mm) provides spatial resolution of 30 mm at the plasma center. Results clearly indicate a very good focus image of the fiber and suggest the absence of the cross-talk between adjacent fiber images. Absolute intensity calibration has been done using a standard tungsten lamp to analyze the Z(eff) value. The bremsstrahlung profile and resultant Z(eff) profile have been obtained after Abel inversion of the signals observed in large helical device plasmas with elliptical poloidal cross section. PMID:19044678

  19. Microscopy system of atomic force based on a digital optical reading unit and a buzzer-scanner

    International Nuclear Information System (INIS)

    An astigmatic detection system (Ads) based on a compact disk/digital-versatile-disk (Cd-DVD) astigmatic optical pickup unit is presented. It can achieve a resolution better than 0.3 nm in detection of the vertical displacement and is able to detect the two-dimensional angular tilt of the object surface. Furthermore, a novel scanner design actuated by piezoelectric disk buzzers is presented. The scanner is composed of a quad-rod actuation structure and several piezoelectric disks. It can be driven directly with low-voltage and low-current sources, such as analogue outputs of a data acquisition card and enables a sufficient scanning range of up to μm. In addition, an economic, high-performance streamlined atomic force microscopy (AFM) was constructed, using the buzzer-scanner to move the sample relative to the probe, and using a Cd/DVD optical pickup unit to detect the mechanical resonance of a micro fabricated cantilever. The performance of the AFM is evaluated. The high sensitivity and high bandwidth of the detection system makes the equipment suitable for characterizing nano scale elements. An AFM using our detection system for detecting the deflection of micro fabricated cantilevers can resolve individual atomic steps on graphite surfaces. (Author)

  20. Scleral Fixation of Posteriorly Dislocated Intraocular Lenses by 23-Gauge Vitrectomy without Anterior Segment Approach.

    Science.gov (United States)

    Nadal, Jeroni; Kudsieh, Bachar; Casaroli-Marano, Ricardo P

    2015-01-01

    Background. To evaluate visual outcomes, corneal changes, intraocular lens (IOL) stability, and complications after repositioning posteriorly dislocated IOLs and sulcus fixation with polyester sutures. Design. Prospective consecutive case series. Setting. Institut Universitari Barraquer. Participants. 25 eyes of 25 patients with posteriorly dislocated IOL. Methods. The patients underwent 23-gauge vitrectomy via the sulcus to rescue dislocated IOLs and fix them to the scleral wall with a previously looped nonabsorbable polyester suture. Main Outcome Measures. Best corrected visual acuity (BCVA) LogMAR, corneal astigmatism, endothelial cell count, IOL stability, and postoperative complications. Results. Mean follow-up time was 18.8 ± 10.9 months. Mean surgery time was 33 ± 2 minutes. Mean BCVA improved from 0.30 ± 0.48 before surgery to 0.18 ± 0.60 (p = 0.015) at 1 month, which persisted to 12 months (0.18 ± 0.60). Neither corneal astigmatism nor endothelial cell count showed alterations 1 year after surgery. Complications included IOL subluxation in 1 eye (4%), vitreous hemorrhage in 2 eyes (8%), transient hypotony in 2 eyes (8%), and cystic macular edema in 1 eye (4%). No patients presented retinal detachment. Conclusion. This surgical technique proved successful in the management of dislocated IOL. Functional results were good and the complications were easily resolved. PMID:26294964

  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. Repeatability and Comparison of Keratometry Values Measured with Potec PRK-6000 Autorefractometer, IOLMaster, and Pentacam

    Directory of Open Access Journals (Sweden)

    Adem Türk

    2014-05-01

    Full Text Available Objectives: To research the repeatability and intercompatibility of keratometry values measured with Potec PRK-6000 autorefractometer, IOL Master, and Pentacam. Materials and Methods: In this prospective study, consecutive measurements were performed in two different sessions with the mentioned three devices on 110 eyes of 55 subjects who had no additional ocular pathology except for refraction error. The consistency of flat and steep keratometry, average keratometry, and corneal astigmatism values obtained in both sessions was compared by using intraclass correlation coefficient (ICC. The measurement differences between the devices were statistically compared as well. Results: The mean age of the study subjects was 23.05±3.01 (18-30 years. ICC values of average keratometry measurements obtained in the sessions were 0.996 for Potec PRK-6000 autorefractometer, 0.997 for IOL Master, and 0.999 for Pentacam. There was high compatibility between the three devices in terms of average keratometry values in Bland-Altman analysis. However, there were statistically significant differences between the devices in terms of parameters other than corneal astigmatism. Conclusion: The repeatability of the three devices was found considerably high in keratometry measurements. However, it is not appropriate for these devices to be substituted for each other in keratometry measurements. (Turk J Ophthalmol 2014; 44: 179-83

  3. Incisões relaxantes limbares durante a cirurgia de catarata: resultados após seguimento de um ano Limbal relaxing incisions during cataract surgery: one-year follow-up

    Directory of Open Access Journals (Sweden)

    João Carlos Arraes

    2006-06-01

    ções pós-operatórias significativas.PURPOSE: To evaluate astigmatism variation between preoperative, 1st and 12th postoperative month of patients who underwent cataract surgery with limbal relaxing incisions (LRI aiming to reduce the preoperative astigmatism. METHODS: Sixteen patients who underwent cataract surgery by the phacoemulsification technique with a 5.5 mm escleral incision, at the Altino Ventura Foudation, between April and July of 2002. The limbal relaxing incisions were performed according to Gills' modified nomogram (1D - 1 LRI of 6 mm; 1-2D - 2 LRI of 6 mm; 2-3D - 2 LRI of 8 mm. They were done in the most curved meridians, determined by preoperative corneal topography. RESULTS: Significant reduction in preoperative astigmatism was observed in the 1st postoperative month in 2 limbal relaxing incisions of the 6 mm group (57% topographic astigmatism and 87% refractional and in 2 limbal relaxing incisions of the 8 mm group (50% topographic astigmatism and 65% refractional, maintaining the reduction with no significant alteration until the 12th postoperative month. The 1 limbal relaxing incision of the 6 mm group did not yield significant astigmatism reduction, but there was no significant alteration until de 12th postoperative month. There were also no complications such as postoperative discomfort, glare, aniseiconia, diplopia, incision infection and corneal thinning or ectasia. CONCLUSION: Two limbal relaxing incisions of 8 and 6 mm aiming to correct preoperative astigmatism of 2 to 3D and 1 to 2D, respectively, were safe and effective with a stable effect in the first postoperative follow-up year. The 1 limbal relaxing incision of 6 mm aiming to reduce 1 diopter of preoperative astigmatism was not effective, but it did not induce any significant postoperative complications.

  4. Determination of injection molding process windows for optical lenses using response surface methodology.

    Science.gov (United States)

    Tsai, Kuo-Ming; Wang, He-Yi

    2014-08-20

    This study focuses on injection molding process window determination for obtaining optimal imaging optical properties, astigmatism, coma, and spherical aberration using plastic lenses. The Taguchi experimental method was first used to identify the optimized combination of parameters and significant factors affecting the imaging optical properties of the lens. Full factorial experiments were then implemented based on the significant factors to build the response surface models. The injection molding process windows for lenses with optimized optical properties were determined based on the surface models, and confirmation experiments were performed to verify their validity. The results indicated that the significant factors affecting the optical properties of lenses are mold temperature, melt temperature, and cooling time. According to experimental data for the significant factors, the oblique ovals for different optical properties on the injection molding process windows based on melt temperature and cooling time can be obtained using the curve fitting approach. The confirmation experiments revealed that the average errors for astigmatism, coma, and spherical aberration are 3.44%, 5.62%, and 5.69%, respectively. The results indicated that the process windows proposed are highly reliable. PMID:25321095

  5. Microscopy system of atomic force based on a digital optical reading unit and a buzzer-scanner; Sistema de microscopia de fuerza atomica basada en una unidad de lectura optica digital y un escaner-zumbador

    Energy Technology Data Exchange (ETDEWEB)

    Dabirian, R.; Loza M, D. [Universidad de las Fuerzas Armadas-ESPE, Departamento de Ciencias de la Energia y Mecanica, Sangolqui (Ecuador); Wang, W. M.; Hwu, E. T., E-mail: whoand@gmail.com [Academia Sinica, Institute of Physics, Taipei, 11529 Taiwan (China)

    2015-07-01

    An astigmatic detection system (Ads) based on a compact disk/digital-versatile-disk (Cd-DVD) astigmatic optical pickup unit is presented. It can achieve a resolution better than 0.3 nm in detection of the vertical displacement and is able to detect the two-dimensional angular tilt of the object surface. Furthermore, a novel scanner design actuated by piezoelectric disk buzzers is presented. The scanner is composed of a quad-rod actuation structure and several piezoelectric disks. It can be driven directly with low-voltage and low-current sources, such as analogue outputs of a data acquisition card and enables a sufficient scanning range of up to μm. In addition, an economic, high-performance streamlined atomic force microscopy (AFM) was constructed, using the buzzer-scanner to move the sample relative to the probe, and using a Cd/DVD optical pickup unit to detect the mechanical resonance of a micro fabricated cantilever. The performance of the AFM is evaluated. The high sensitivity and high bandwidth of the detection system makes the equipment suitable for characterizing nano scale elements. An AFM using our detection system for detecting the deflection of micro fabricated cantilevers can resolve individual atomic steps on graphite surfaces. (Author)

  6. High-performance oscillators employing adaptive optics comprised of discrete elements

    Science.gov (United States)

    Jackel, Steven M.; Moshe, Inon; Lavi, Raphael

    1999-05-01

    Flashlamp pumped oscillators utilizing Nd:Cr:GSGG or Nd:YAG rods were stabilized against varying levels of thermal focusing by use of a Variable Radius Mirror (VRM). In its simplest form, the VRM consisted of a lens followed by a concave mirror. Separation of the two elements controlled the radius of curvature of the reflected phase front. Addition of a concave-convex variable-separation cylindrical lens pair, allowed astigmatism to be corrected. These distributed optical elements together with a computer controlled servo system formed an adaptive optic capable of correcting the varying thermal focusing and astigmatism encountered in a Nd:YAG confocal unstable resonator (0 - 30 W) and in Nd:Cr:GSGG stable (hemispherical or concave- convex) resonators so that high beam quality could be maintained over the entire operating range. By utilizing resonators designed to eliminate birefringence losses, high efficiency could also be maintained. The ability to eliminate thermally induced losses in GSGG allows operating power to be increased into the range where thermal fracture is a factor. We present some results on the effect of surface finish (fine grind, grooves, chemical etch strengthening) on fracture limit and high gain operation.

  7. Analysis of the robustness of the lens GRIN profile in a schematic model eye

    Science.gov (United States)

    Díaz, J. A.; Blazejewski, N.; Fernández-Dorado, J.; Arasa, J.; Sorroche, F.; Pizarro, C.

    2011-11-01

    In this work, an improvement of a previously-published human eye model with aging is presented. The previous eye model showed the overestimated performance of an averaged MTF at low spatial frequencies at all ages. Since that model had rotationally symmetrical corneal surfaces, these have been modeled to resemble an astigmatic element according to the recent experimental published data and have been included to produce a more accurate eye model. The gradient refractive index (GRIN) profile proposed for the crystalline lens has not been modified to test its robustness. Further, a tilt and decentration of the lens, and only a decentration for the iris, have been permitted in order to fit the average performance of the new eye model with aging. The results demonstrate that the GRIN profile for the crystalline lens fits the model well, since the decentration and/or tilt of the lens and the iris are sufficient free parameters to simulate the performance of the retinal image quality of an emmetropic human eye with aging, having an average astigmatic cornea.

  8. Scleral Fixation of Posteriorly Dislocated Intraocular Lenses by 23-Gauge Vitrectomy without Anterior Segment Approach

    Directory of Open Access Journals (Sweden)

    Jeroni Nadal

    2015-01-01

    Full Text Available Background. To evaluate visual outcomes, corneal changes, intraocular lens (IOL stability, and complications after repositioning posteriorly dislocated IOLs and sulcus fixation with polyester sutures. Design. Prospective consecutive case series. Setting. Institut Universitari Barraquer. Participants. 25 eyes of 25 patients with posteriorly dislocated IOL. Methods. The patients underwent 23-gauge vitrectomy via the sulcus to rescue dislocated IOLs and fix them to the scleral wall with a previously looped nonabsorbable polyester suture. Main Outcome Measures. Best corrected visual acuity (BCVA LogMAR, corneal astigmatism, endothelial cell count, IOL stability, and postoperative complications. Results. Mean follow-up time was 18.8 ± 10.9 months. Mean surgery time was 33 ± 2 minutes. Mean BCVA improved from 0.30 ± 0.48 before surgery to 0.18 ± 0.60 (p=0.015 at 1 month, which persisted to 12 months (0.18 ± 0.60. Neither corneal astigmatism nor endothelial cell count showed alterations 1 year after surgery. Complications included IOL subluxation in 1 eye (4%, vitreous hemorrhage in 2 eyes (8%, transient hypotony in 2 eyes (8%, and cystic macular edema in 1 eye (4%. No patients presented retinal detachment. Conclusion. This surgical technique proved successful in the management of dislocated IOL. Functional results were good and the complications were easily resolved.

  9. Analysis of nodal aberration properties in off-axis freeform system design.

    Science.gov (United States)

    Shi, Haodong; Jiang, Huilin; Zhang, Xin; Wang, Chao; Liu, Tao

    2016-08-20

    Freeform surfaces have the advantage of balancing off-axis aberration. In this paper, based on the framework of nodal aberration theory (NAT) applied to the coaxial system, the third-order astigmatism and coma wave aberration expressions of an off-axis system with Zernike polynomial surfaces are derived. The relationship between the off-axis and surface shape acting on the nodal distributions is revealed. The nodal aberration properties of the off-axis freeform system are analyzed and validated by using full-field displays (FFDs). It has been demonstrated that adding Zernike terms, up to nine, to the off-axis system modifies the nodal locations, but the field dependence of the third-order aberration does not change. On this basis, an off-axis two-mirror freeform system with 500 mm effective focal length (EFL) and 300 mm entrance pupil diameter (EPD) working in long-wave infrared is designed. The field constant aberrations induced by surface tilting are corrected by selecting specific Zernike terms. The design results show that the nodes of third-order astigmatism and coma move back into the field of view (FOV). The modulation transfer function (MTF) curves are above 0.4 at 20 line pairs per millimeter (lp/mm) which meets the infrared reconnaissance requirement. This work provides essential insight and guidance for aberration correction in off-axis freeform system design. PMID:27557003

  10. Aperture referral in dioptric systems with stigmatic elements

    Directory of Open Access Journals (Sweden)

    W. F. Harris

    2012-12-01

    Full Text Available A previous paper develops the general theory of aperture referral in linear optics and shows how several ostensibly distinct concepts, including the blur patch on the retina, the effective cornealpatch, the projective field and the field of view, are now unified as particular applications of the general theory.  The theory allows for astigmatism and heterocentricity.  Symplecticity and the generality of the approach, however, make it difficult to gain insight and mean that the material is not accessible to readers unfamiliar with matrices and linear algebra. The purpose of this paper is to examine whatis, perhaps, the most important special case, that in which astigmatism is ignored.  Symplecticity and, hence, the mathematics become greatly simplified. The mathematics reduces largely to elementary vector algebra and, in some places, simple scalar algebra and yet retains the mathematical form of the general approach.  As a result the paper allows insight into and provides a stepping stone to the general theory.  Under referral an aperture under-goes simple scalar magnification and transverse translation.  The paper pays particular attention to referral to transverse planes in the neighbourhood of a focal point where the magnification may be positive, zero or negative.  Circular apertures are treated as special cases of elliptical apertures and the meaning of referred apertures of negative radius is explained briefly. (S Afr Optom 2012 71(1 3-11

  11. Effects of Silicone Hydrogel Contact Lens Application on Corneal High-order Aberration and Visual Guality in Patients with Corneal Opacities

    Directory of Open Access Journals (Sweden)

    Sevda Aydın Kurna

    2012-03-01

    Full Text Available Pur po se: Evaluation of the corneal high-order aberrations and visual quality changes after application of silicone hydrogel contact lenses in patients with corneal opacities due to various etiologies. Ma te ri al and Met hod: Fifteen eyes of 13 patients with corneal opacities were included in the study. During the ophthalmologic examination before and after contact lens application, visual acuity was measured with Snellen acuity chart and contrast sensitivity - with Bailey-Lowie Charts in letters. Aberrations were measured with corneal aberrometer (NIDEK Magellan Mapper under a naturally dilated pupil. Spherical aberration, coma, trefoil, irregular astigmatism and total high-order root mean square (RMS values were recorded. Measurements were repeated with balafilcon A lenses (PureVision 2 HD, B&L on all patients. Re sults: Patient age varied between 23 and 50 years. Two eyes had subepithelial infiltrates due to adenoviral keratitis, 1 had nebulae due to previous infections or trauma, and 2 had Salzmann’s nodular degeneration. We observed a mean increase of 1 line in visual acuity and 5 letters in contrast sensitivity with contact lenses versus glasses in the patients. Mean RMS values of spherical aberration, irregular astigmatism and total high-order aberrations decreased significantly with contact lenses. Dis cus si on: Silicone hydrogel soft contact lenses may improve visual quality by decreasing the corneal aberrations in patients with corneal opacities. (Turk J Ophthalmol 2012; 42: 97-102

  12. Fiber Grating Coupled Light Source Capable of Tunable, Single Frequency Operation

    Science.gov (United States)

    Krainak, Michael A. (Inventor); Duerksen, Gary L. (Inventor)

    2001-01-01

    Fiber Bragg grating coupled light sources can achieve tunable single-frequency (single axial and lateral spatial mode) operation by correcting for a quadratic phase variation in the lateral dimension using an aperture stop. The output of a quasi-monochromatic light source such as a Fabry Perot laser diode is astigmatic. As a consequence of the astigmatism, coupling geometries that accommodate the transverse numerical aperture of the laser are defocused in the lateral dimension, even for apsherical optics. The mismatch produces the quadratic phase variation in the feedback along the lateral axis at the facet of the laser that excites lateral modes of higher order than the TM(sub 00). Because the instability entails excitation of higher order lateral submodes, single frequency operation also is accomplished by using fiber Bragg gratings whose bandwidth is narrower than the submode spacing. This technique is particularly pertinent to the use of lensed fiber gratings in lieu of discrete coupling optics. Stable device operation requires overall phase match between the fed-back signal and the laser output. The fiber Bragg grating acts as a phase-preserving mirror when the Bragg condition is met precisely. The phase-match condition is maintained throughout the fiber tuning range by matching the Fabry-Perot axial mode wavelength to the passband center wavelength of the Bragg grating.

  13. Progress of Toric intraocular lenses%散光人工晶状体的应用进展

    Institute of Scientific and Technical Information of China (English)

    张劲松

    2010-01-01

    Astigmatism can affect visual quality and visual acuity, and it can be corrected by different methods. Toric intraocular lens (Toric IOL) which combined astigmatism correction and spherical correction together is a newest kind of functional intraocular lens. Using Toric IOL is a reliable, predictable and stable refractive correction choice. With Toric IOL popularized, more and more technical experience were accumulated. The patients selection, insert techniques and complications prevention were improved greatly.%散光会造成视觉质量和视力的下降,可以通过多种方法矫正.散光人工晶状体(Toric IOL)是将散光矫正与人工晶状体的球镜度数相结合的一种新型功能性人工晶状体.利用这种人工晶状体矫正角膜散光是一种合理的、预测性强、术后效果更加稳定的屈光矫正方式.随着Toric IOL在临床应用的推广,这一技术的应用经验得到不断的积累,Toric IOL的适应证选择、植入技术、并发症的预防等方面日趋完善.

  14. Generalized magnification in visual optics. Part 2: Magnification as affine transformation

    Directory of Open Access Journals (Sweden)

    W. F. Harris

    2010-12-01

    Full Text Available In astigmatic systems magnification may be different in different directions.  It may also be accompanied by rotation or reflection.  These changes from object to image are examples of generalized magnification.  They are represented by  2 2×  matrices.  Because they are linear transformations they can be called linear magnifications.  Linear magnifications account for a change in appearance without regard to position.  Mathematical structure suggests a natural further generalization to a magnification that is complete in the sense that it accountsfor change in appearance and position.  It is represented by a  3 3×  matrix with a dummy third row. The transformation is called affine in linear algebra which suggests that these generalized magnifica-tions be called affine magnifications.  The purpose of the paper is to define affine magnification in the context of astigmatic optics.  Several examples are presented and illustrated graphically. (S Afr Optom 2010 69(4 166-172

  15. Advances in very lightweight composite mirror technology

    Science.gov (United States)

    Chen, Peter C.; Bowers, Charles W.; Content, David A.; Marzouk, Marzouk; Romeo, Robert C.

    2000-09-01

    We report progress in the development of very lightweight (roll off and several waves (rms optical) of astigmatism, coma, and third-order spherical aberration. These are indications of thermal contraction in an inhomogeneous medium. This inhomogeneity is due to a systematic radial variation in density and fiber/resin ratio induced in composite plies when draped around a small and highly curved mandrel. The figure accuracy is expected to improve with larger size optics and in mirrors with longer radii of curvature. Nevertheless, the present accuracy figure is sufficient for using postfiguring techniques such as ion milling to achieve diffraction-limited performances at optical and UV wavelengths. We demonstrate active figure control using a simple apparatus of low-mass, low-force actuators to correct astigmatism. The optimized replication technique is applied to the fabrication of a 0.6-m-diam mirror with an areal density of 3.2 kg/m2. Our result demonstrates that the very lightweight, large-aperture construction used in radio telescopes can now be applied to optical telescopes.

  16. An omnidirectional 3D sensor with line laser scanning

    Science.gov (United States)

    Xu, Jing; Gao, Bingtuan; Liu, Chuande; Wang, Peng; Gao, Shuanglei

    2016-09-01

    An active omnidirectional vision owns the advantages of the wide field of view (FOV) imaging, resulting in an entire 3D environment scene, which is promising in the field of robot navigation. However, the existing omnidirectional vision sensors based on line laser can measure points only located on the optical plane of the line laser beam, resulting in the low-resolution reconstruction. Whereas, to improve resolution, some other omnidirectional vision sensors with the capability of projecting 2D encode pattern from projector and curved mirror. However, the astigmatism property of curve mirror causes the low-accuracy reconstruction. To solve the above problems, a rotating polygon scanning mirror is used to scan the object in the vertical direction so that an entire profile of the observed scene can be obtained at high accuracy, without of astigmatism phenomenon. Then, the proposed method is calibrated by a conventional 2D checkerboard plate. The experimental results show that the measurement error of the 3D omnidirectional sensor is approximately 1 mm. Moreover, the reconstruction of objects with different shapes based on the developed sensor is also verified.

  17. Toric人工晶状体临床应用的研究进展%Clinical applications of Toric intraocular lens

    Institute of Scientific and Technical Information of China (English)

    肖显文; 张红; 田芳

    2014-01-01

    Toric intraocular lens (IOL),known as IOL with composite surface,is a new refractive IOL to correct astigmatism by cylindrical lens combined with spherical IOL.Toric IOL has become a reasonable,effective and stable refractive method to correct preoperative astigmatism of cataract patients following the continuous development of materials and technical improvements since it was applied clinically first in 1994.The new multifocal Toric IOL provides good distance,intermediate and near functional vision and enables the complete spectacle independence for cataract patients.%散光型人工晶状体(Toric intraocular lens,Toric IOL)也称复合曲面IOL,是将矫正散光的圆柱镜与IOL的球镜相结合的一种新型屈光性IOL.自1994年第一枚Toric IOL用于临床以来,Toric IOL的材料和设计得到不断改进,现已成为矫正白内障患者术前角膜散光的一种合理、有效并且稳定的屈光矫正方式.多焦点Toric IOL的出现则为白内障患者提供良好的远中近视力,真正满足白内障患者的脱镜需求.

  18. Zeff profile measurement system with an optimized Czerny-Turner visible spectrometer in large helical device

    International Nuclear Information System (INIS)

    Zeff measurement system using a visible spectrometer has been newly designed and constructed instead of an old interference filter system to eliminate line emissions from the signal and to measure the Zeff value in low-density plasmas. The system consists of the Czerny-Turner-type spectrometer with a charge-coupled device camera and 44 optical fibers vertical array. The spectrometer is equipped with an additional toroidal mirror for further reduction in the astigmatism in addition to a flat and two spherical mirrors and three gratings (110, 120, and 1200 grooves/mm) with 30 cm focal length. The images from 44 optical fibers can be detected without astigmatism in a wavelength range of 200-900 nm. Combination of the optical fiber (core diameter: 100 μm) with the lens (focal length: 30 mm) provides spatial resolution of 30 mm at the plasma center. Results clearly indicate a very good focus image of the fiber and suggest the absence of the cross-talk between adjacent fiber images. Absolute intensity calibration has been done using a standard tungsten lamp to analyze the Zeff value. The bremsstrahlung profile and resultant Zeff profile have been obtained after Abel inversion of the signals observed in large helical device plasmas with elliptical poloidal cross section.

  19. DEVICE FOR MEASURING OF THERMAL LENS PARAMETERS IN LASER ACTIVE ELEMENTS WITH A PROBE BEAM METHOD

    Directory of Open Access Journals (Sweden)

    A. N. Zakharova

    2015-01-01

    Full Text Available We have developed a device for measuring of parameters of thermal lens (TL in laser active elements under longitudinal diode pumping. The measurements are based on the probe beam method. This device allows one to determine sign and optical power of the lens in the principal meridional planes, its sensitivity factor with respect to the absorbed pump power and astigmatism degree, fractional heat loading which make it possible to estimate integral impact of the photoelastic effect to the formation of TL in the laser element. The measurements are performed in a linearly polarized light at the wavelength of 532 nm. Pumping of the laser element is performed at 960 nm that makes it possible to study laser materials doped with Yb3+ and (Er3+, Yb3+ ions. The precision of measurements: for sensitivity factor of TL – 0,1 m-1/W, for astigmatism degree – 0,2 m-1/W, for fractional heat loading – 5 %, for the impact of the photoelastic effect – 0,5 × 10-6 K-1. This device is used for characterization of thermal lens in the laser active element from an yttrium vanadate crystal, Er3+,Yb3+:YVO .

  20. Toric设计角膜塑形镜与视觉质量%Toric design orthokeratology contact lenses and visual quality

    Institute of Scientific and Technical Information of China (English)

    杨丽娜; 周建兰; 谢培英

    2013-01-01

    Objective To observe the changes in corneal astigmatism after patients are fitted with different ortho-k contact lens (CL) designs and the influence of these lenses on visual quality.Methods In a case-control study,corneal astigmatism,corneal topography,wavefront aberrations (Pentacam),visual acuity and visual disturbance symptoms were observed in three groups (groups A,B,C) before and after CL wear.Group A (30 eyes) had lower corneal astigmatism and wore a general ortho-k contact lens design that fit quite well; group B (30 eyes) had lower corneal astigmatism and wore a general ortho-k contact lens design that did not fit well and was obviously decentered; group C (31 eyes) had higher corneal astigmatism and wore toric ortho-k contact lenses with an acceptable fit.SPSS 16.0 statistical software was used to analyze the data.Results Changes in corneal astigmatism after fitting with the ortho-k CL:astigmatism increased in group B but was lower in groups A and C.Fourier analysis from corneal topography:increases in asymmetry for all three groups at 3 mm were (-0.393±0.329)D,(-4.050±2.084)D,and (-0.494±0.522)D,respectively,all at P<0.001.Higher order aberrations in the three groups increased at 3 mm and were (-0.011±0.055)D (P>0.05),(-0.635±0.441)D (P<0.001) and (-0.055±0.082)D (P<0.01).The three groups at 3 mm regular:differences in the comparison of astigmatism,asymmetry and higher order aberrations were statistically significant,F=79.862,F=83.882,F=54.265,respectively,all at P<0.01.After fitting with ortho-k CLs,the total aberrations and total higher order aberrations for the three groups increased in varying degrees,with group B as the most significant.A comparison of the difference in aberrations:only the anterior surface of the spherical aberration had a statistically significant difference (F=18.048,P<0.01).After the CLs were removed:in group A 36.7 % achieved a UVA of 1.2,50.0% achieved 1.0 and 13.3% achieved 0.8; in group B 36.7

  1. Long-term outcomes of limbal relaxing incisions during cataract surgery: aberrometric analysis

    Directory of Open Access Journals (Sweden)

    Monaco G

    2015-08-01

    Full Text Available Gaspare Monaco, Antonio ScialdoneDepartment of Ophthalmology, Ospedale Fatebenefratelli e Oftalmico, Milan, ItalyPurpose: To compare the final changes in corneal wavefront aberration by limbal relaxing incisions (LRIs after cataract surgery.Methods: This prospective cumulative interventional nonrandomized case study included cataract and astigmatic patients undergoing LRIs and phaco with intraocular lens implantation. LRIs were planned using Donnenfeld nomogram. The root mean square of corneal wave aberration for total Z(n,i(1≤n≤8, astigmatism Z(2,±1, coma Z(3–5–7,±1, trefoil Z(3–5–7,±2, spherical Z(4–6–8,0, and higher-order aberration (HOA Z(3≤n≤8 was examined before and 3 years after surgery (optical path difference-Scan II [OPD-Scan II]. Uncorrected distance visual acuity and best-corrected distance visual acuity (CDVA for distance, keratometric cylinder, and variations in average corneal power were also analyzed.Results: Sixty-four eyes of 48 patients were included in the study. Age ranged from 42 to 92 years (70.6±8.4 years. After LRIs, uncorrected distance visual acuity and best-corrected distance visual acuity improved statistically (P<0.01. The keratometric cylinder value decreased by 40.1%, but analysis of KP90 and KP135 polar values did not show any decrease that could be statistically confirmed (P=0.22 and P=0.24. No significant changes were detected in root mean square of total (P=0.61 and HOAs (P=0.13 aberrations. LRIs did not induce alteration in central corneal power confirming a 1:1 coupling ratio.Conclusion: LRIs determined a nonsignificant alteration of corneal HOA. Therefore, LRIs can be still considered a qualitatively viable mean in those cases where toric intraocular lenses are contraindicated or not available. Yet, the authors raise the question of nonpersonalized nomograms, as in the present study, LRIs did not reach the preset target cylinder. Keywords: astigmatism, ocular wavefront, intraocular

  2. Comparação entre os resultados pós-operatórios de pacientes submetidos ao procedimento tríplice e transplante de córnea combinado a fixação secundária de lente intra-ocular Comparison between the postoperative results of triple procedure and combined penetrating keratoplasty/ transsclerally sutured posterior chamber lens implantation

    Directory of Open Access Journals (Sweden)

    Daniela Maggioni Pereira Leão

    2006-08-01

    Full Text Available OBJETIVO: Comparar os resultados pós-operatórios de 2 grupos de pacientes submetidos a transplante de córnea com técnicas e tempo cirúrgico diferentes, em relação à abordagem do cristalino e/ou lente intra-ocular. MÉTODOS: Neste estudo retrospectivo foram analisados 37 olhos de pacientes divididos em 2 grupos: extração de catarata, implante de lentes intra-oculares (LIO e transplante de córnea no mesmo tempo cirúrgico - grupo 1 (G1 e extração de catarata sem implante de lentes intra-oculares no primeiro tempo cirúrgico e fixação secundária de lentes intra-oculares associada a transplante de córnea no segundo tempo cirúrgico - grupo 2 (G2. As variáveis estudadas foram: acuidade visual, pressão intra-ocular (PIO, astigmatismo refracional, astigmatismo ceratométrico e complicações pós-operatórias. RESULTADOS: Foi observado melhora da acuidade visual nos 2 grupos (G1 pPURPOSE: To compare the outcomes of two surgical techniques of penetrating keratoplasty with different surgical time, regarding the crystalline and the intraocular lens. METHODS: This retrospective study included 37 patients' eyes divided into 2 groups: extracapsular cataract extraction, posterior chamber intraocular lens implantation and penetrating keratoplasty (Group 1, G1 and transscleral fixation of posterior chamber lens and penetrating keratoplasty (Group 2, G2. The following parameters were recorded: visual acuity, intraocular pressure, refractive astigmatism, complication and keratometric astigmatism. RESULTS: Visual acuity improved in the two groups (G1 p<0.001 and G2 p=0.008. In G2 a significant change for the worse of intraocular pressure outcome was observed when compared with the other group (p=0.014. Regarding refractive and keratometric astigmatism no significant differences between the groups were found. The follow-up was 11 months. CONCLUSION: The most important negative prognostic factor affecting visual acuity was the postkeratoplasty

  3. 渐进多焦点镜片的逐点定向曲率补偿优化设计%Optimization Design for Progressive Addition Lenses by Pointwise Directional Curvature Compensation

    Institute of Scientific and Technical Information of China (English)

    秦琳玲; 钱霖; 余景池

    2012-01-01

    提出一种利用逐点定向曲率补偿法对渐进多焦点镜片初始模型进行整体优化以减小周边散光区(俗称盲区)的优化设计方法.推导出自由曲面任意方向法曲率的计算公式、确定主曲率和主方向的方法,求出镜片初始模型上各点的曲率差和最大曲率方向、最小曲率方向,通过迭加由不同曲率、不同轴向微小柱面构成的自由曲面,来实现逐点定向曲率补偿,使镜片各点的曲率差适当减小,从而减小散光.给出具体优化步骤和一个优化设计实例,并进行实际加工制作与检测.对比优化前后的光焦度和散光度的面形分布图.结果表明,逐点定向曲率补偿法能有效减小渐进多焦点镜片初始模型的最大散光并明显扩大视远区清晰视觉范围.%A global optimizing method using pointwise directional curvature compensation which can reduce the undesirable astigmatism is proposed. The calculation formula of normal curvature at arbitrary direction is deducted and the method is proposed to determine the principal curvature and principal direction. The principal curvature difference and the directions of the maximum and minimum curvature of the initial progressive addition lens are calculated. The optimizaiton method can reduce the astigmatism by adding the freeform surface consisting of micro cylinders with different curvatures and different directions. The optimization algorithm and an example are given. An initial progressive addition lens and an optimized lens by this method are manufactured and tested. Compared with the initial lens, the optimized lens has smaller maximum astigmatism value and larger clear region in the distance-vision zone.

  4. 渐进多焦点眼用镜片的平均曲率流优化设计%Optimizing Design for Progressive Addition Lenses by Mean Curvature Flow

    Institute of Scientific and Technical Information of China (English)

    唐运海; 吴泉英; 钱霖; 刘琳

    2011-01-01

    The principle of mean curvature flow is illustrated. An optimizing method using mean curvature flow is proposed which can reduce the undesirable astigmatism in some regions of the progressive addition lens surface while retaining desirable optical features of the progressive lenses. It is presented that the more the surface of the progressive lens becomes closer to spherical by the process of mean curvature flow, the more the astigmatism is smaller. The optimizing algorithm and an example are given out. An initial designed progressive addition lens and an optimized lens by this method are manufactured and tested. Compared with the original lens, the optimized lens has smaller maximum astigmatism value and larger clear region on the intermediate zone and the distance-vision zone.%阐述平均曲率流原理,提出一种利用平均曲率流对初始设计的渐进多焦点眼用镜片进行局部优化以减小指定区域像散的优化设计方法.采用平均曲率流方法使镜片渐进表面上符合设定条件的区域更加趋近于球面,从而减小镜片表面该区域处的像散.给出具体算法步骤和一个优化设计实例,并进行实际加工制作与检测.对比优化前后的光焦度、像散和通道宽度等参数,结果表明:平均曲率流优化方法能够在保证镜片光焦度不变的情况下,有效减小初始设计渐进多焦点眼用镜片的最大像散并适当增加渐变通道宽度和扩大视远区清晰视觉范围.

  5. Topographical Evaluation of the Decentration of Orthokeratology Lenses

    Institute of Scientific and Technical Information of China (English)

    Xiao Yang; Xingwu Zhong; Xiangming Gong; Junwen Zeng

    2005-01-01

    Purpose: To evaluate the amount of lens decentration and various factors affecting decentration after orthokeratology lens wear and to observe the effect of decentration on the visual functions.Methods: Two kinds of orthokeratology lenses were fitted to 270 eyes of 135 patients [initial mean refractive error: (-3.98±1.51)D]. Humphery Instruments ATLAS 990 was used for the computer-assisted analysis of corneal topographical maps. The examination of corneal topography was performed on patients before and after 6 months of wearing orthokeratology lenses. The amount of decentration of orthokeratology lenses was measured by finding the distance between center of optic zone and the pupil center. The factors influencing the amount of decentration were analyzed, including the initial refraction error, astigmatism, keratometry values, corneal eccentricity, and the diameter of lens.Visual symptoms including monocular diplopia, glare around lights were recorded to evaluate the effects of decentration on visual functions.Results: The mean amount of decentration was (0.49±0.34) mm after one night's wear.The mean amount of decentration after 1 month, 3 months and 6 months was (0.57±0.41) mm, (0.55±0.48) mm and (0.59±0.39) mm, respectively. After one month, the amount of decentration was less than 0.50 mm in 51.1% eyes, 0.50~1.0 mm in 35.6% eyes and more than 1.00 mm in 13.3% eyes. The direction of decentration of more than 0.50 mm was mainly in the temporal quadrant (48.5%). Patients with greater initial astigmatism and smaller lenses showed greater decentration (P<0.05). There was no statistically significant difference in decentration between the two groups with different corneal eccentricities and keratometry values (P>0.05). The amount of decentration was greater in patients who complained of monocular diplopia and glare.Conclusions: The amount of decentration of orthokeratology depends on the initial refractive error, astigmatism and the design of orthokeratology

  6. Efficacy and safety of deep anterior lamellar keratoplasty vs. penetrating keratoplasty for keratoconus: a meta-analysis.

    Directory of Open Access Journals (Sweden)

    Hao Liu

    Full Text Available To evaluate difference in therapeutic outcomes between deep anterior lamellar keratoplasty (DALK and penetrating keratoplasty (PKP for the clinical treatment of keratoconus.A comprehensive search was conducted in Pubmed, EMBASE, Cochrane Library, and Web of science. Eligible studies should include at least one of the following factors: best corrected visual acuity (BCVA, postoperative spherical equivalent (SE, postoperative astigmatism and endothelial cell count (ECC, central corneal thickness (CCT, graft rejection and graft failure, of which BCVA, graft rejection and graft failure were used as the primary outcome measures, and postoperative SE, astigmatism, CCT and ECC as the secondary outcome measures. Given the lack of randomized clinical trials (RCTs, cohort studies and prospective studies were considered eligible.Sixteen clinical trials involving 6625 eyes were included in this review, including 1185 eyes in DALK group, and 5440 eyes in PKP group. The outcomes were analyzed using Cochrane Review Manager (RevMan version 5.0 software. The postoperative BCVA in DALK group was significantly better than that in PKP group (OR = 0.48; 95%CI 0.39 to 0.60; p<0.001. There were fewer cases of graft rejection in DALK group than those in PKP group (OR = 0.28; 95%CI 0.15 to 0.50; p<0.001. Nevertheless the rate of graft failure was similar between DALK and PKP groups (OR = 1.05; 95%CI 0.81 to 1.36; p = 0.73. There were no significant differences in the secondary outcomes of SE (p = 0.70, astigmatism (p = 0.14 and CCT (p = 0.58 between DALK and PKP groups. And ECC in DALK group was significantly higher than PKP group (p<0.001. The postoperative complications, high intraocular pressure (high-IOP and cataract were analyzed, fewer cases of complications occurred in DALK group than those in PKP group (high-IOP, OR 0.22, 95% CI 0.11-0.44, P<0.001 (cataract, OR 0.22; 95% CI 0.08-0.61, P = 0.004. And no cases of expulsive hemorrhage and endophthalmitis were

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

    Institute of Scientific and Technical Information of China (English)

    Ejup Mahmudi; Vilma Mema; Nora Burda; Brikena Selimi; Sulejman Zhugli

    2013-01-01

    Objective: To determine the incidence of refractive errors at children 3 to 9 years of age in the area of Tetovo, Macedonia in rural and urban population. Methods: Population-based cross-sectional samples of children 3 to 9 years in rural and urban population were obtained through full ophthalmologic examination, and they underwent slit-lamp examination, ocular motility and refraction. They were presenting uncorrected and best-corrected visual acuity, along with refractive error under topical cycloplegia. Children 3 to 6 years of age with a visual acuity of 20/40 or worse and those 6 to 9 years of age with a visual acuity of 20/30 or worse underwent a complete ophthalmic examination to determine the cause of visual impairment. A spherical equivalent of-0.5 diopter (D) or worse was defined as myopia, +2.50 D or more was defined as hyperopia and a cylinder refraction greater than 0.75 D was considered astigmatism plus or minus. Results:The uncorrected visual acuity was 20/45 or worse in the better eye of 119 children, 59 male / 60 female (5.1% of participants). According to results of cycloplegic refraction, 1.6% of the children were myopic, 7.3% were hyperopic and the incidence rate of astigmatism was approximately 0.7%. In the multivariate logistic regression myopia and hyperopia were correlated with age (P = 0.040 and P < 0.002, respectively). 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

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

    Directory of Open Access Journals (Sweden)

    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

  9. Fast and precise 3D fluorophore localization by gradient fitting

    Science.gov (United States)

    Ma, Hongqiang; Xu, Jianquan; Jin, Jingyi; Gao, Ying; Lan, Li; Liu, Yang

    2016-02-01

    Astigmatism imaging is widely used to encode the 3D position of fluorophore in single-particle tracking and super-resolution localization microscopy. Here, we present a fast and precise localization algorithm based on gradient fitting to decode the 3D subpixel position of the fluorophore. This algorithm determines the center of the emitter by finding the position with the best-fit gradient direction distribution to the measured point spread function (PSF), and can retrieve the 3D subpixel position of the emitter in a single iteration. Through numerical simulation and experiments with mammalian cells, we demonstrate that our algorithm yields comparable localization precision to the traditional iterative Gaussian function fitting (GF) based method, while exhibits over two orders-of-magnitude faster execution speed. Our algorithm is a promising online reconstruction method for 3D super-resolution microscopy.

  10. A polycarbonate ophthalmic-prescription lens series.

    Science.gov (United States)

    Davis, J K

    1978-08-01

    Improvements in polycarbonate material, production techniques, and scratch-resistant coatings, combined with a process-oriented design, have resulted in a precision lens series. Surface quality is comparable to that of untreated glass ophthalmic lenses. The repeatability of the process results in closely controlled axial power and off-axis performance. For most lens prescriptions, the ANSI Z80.1 optical-center specifications for prescription accuracy are maintained through a total field of view of 40 deg for an 8-mm range of center-of-rotation distances. Off-axis astigmatism is controlled for near-point seeing. The lenses are both lighter and thinner than those of crown glass. A scratch-resistant coating reduces the reflections normally associated with high-index (1.586) materials. Impact resistance exceeds that required by ANSI Z80.7 and is many times that required by ANSI Z80.1.

  11. Fator de correção para indivíduos com capacidade acomodativa baseado no uso do refrator automático Correction factor for individuals with accommodative capacity based on automated refractor

    Directory of Open Access Journals (Sweden)

    Rodrigo Ueno Takahagi

    2009-12-01

    values with and without cycloplegy effect according to age. RESULTS: The correlation between the astigmatism diopter values with and without cicloplegy ranged from 81.52% to 92.27%. Analyzing the spherical diopter values, the correlation was lower (53.57% to 87.78%. The astigmatism axis also revealed low correlation values (28.86% to 58.80%. The multiple regression model according to age demonstrated multiple determination coefficient with high values for myopia (86.38% and astigmatism (79.79%. The lowest multiple determination coefficient was observed for astigmatism axis (17.70%. CONCLUSION: It was possible to demonstrate a high correlation in refractive errors with and without cycloplegy effect on the cylindrical ametropies. Mathematical formules, for cylindrical and spherical ametropies, were presented as a correction factor for refraction of the patients not submitted to cycloplegy.

  12. Alternative optical concept for electron cyclotron emission imaging

    Energy Technology Data Exchange (ETDEWEB)

    Liu, J. X., E-mail: jsliu9@berkeley.edu [Department of Physics, University of California Berkeley, Berkeley, California 94720 (United States); Milbourne, T. [Department of Physics, College of William and Mary, Williamsburg, Virginia 23185 (United States); Bitter, M.; Delgado-Aparicio, L.; Dominguez, A.; Efthimion, P. C.; Hill, K. W.; Kramer, G. J.; Kung, C.; Pablant, N. A.; Tobias, B. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540 (United States); Kubota, S. [Department of Physics, University of California Los Angeles, Los Angeles, California 90095 (United States); Kasparek, W. [Department of Electrical Engineering, University of Stuttgart, Stuttgart (Germany); Lu, J. [Department of Physics, Chongqing University, Chongqing 400044 (China); Park, H. [Ulsan National Institute of Science and Technology, Ulsan 689-798 (Korea, Republic of)

    2014-11-15

    The implementation of advanced electron cyclotron emission imaging (ECEI) systems on tokamak experiments has revolutionized the diagnosis of magnetohydrodynamic (MHD) activities and improved our understanding of instabilities, which lead to disruptions. It is therefore desirable to have an ECEI system on the ITER tokamak. However, the large size of optical components in presently used ECEI systems have, up to now, precluded the implementation of an ECEI system on ITER. This paper describes a new optical ECEI concept that employs a single spherical mirror as the only optical component and exploits the astigmatism of such a mirror to produce an image with one-dimensional spatial resolution on the detector. Since this alternative approach would only require a thin slit as the viewing port to the plasma, it would make the implementation of an ECEI system on ITER feasible. The results obtained from proof-of-principle experiments with a 125 GHz microwave system are presented.

  13. Modified convolution method to reconstruct particle hologram with an elliptical Gaussian beam illumination.

    Science.gov (United States)

    Wu, Xuecheng; Wu, Yingchun; Yang, Jing; Wang, Zhihua; Zhou, Binwu; Gréhan, Gérard; Cen, Kefa

    2013-05-20

    Application of the modified convolution method to reconstruct digital inline holography of particle illuminated by an elliptical Gaussian beam is investigated. Based on the analysis on the formation of particle hologram using the Collins formula, the convolution method is modified to compensate the astigmatism by adding two scaling factors. Both simulated and experimental holograms of transparent droplets and opaque particles are used to test the algorithm, and the reconstructed images are compared with that using FRFT reconstruction. Results show that the modified convolution method can accurately reconstruct the particle image. This method has an advantage that the reconstructed images in different depth positions have the same size and resolution with the hologram. This work shows that digital inline holography has great potential in particle diagnostics in curvature containers.

  14. A study on refractive errors among school children in Kolkata.

    Science.gov (United States)

    Das, Angshuman; Dutta, Himadri; Bhaduri, Gautam; De Sarkar, Ajay; Sarkar, Krishnendu; Bannerjee, Manas

    2007-04-01

    Childhood visual impairment due to refractive errors is a significant problem in school children and has a considerable impact on public health. To assess the magnitude of the problem the present study was undertaken among the school children aged 5 to 10 years in Kolkata. Detailed ophthalmological examination was carried out in the schools as well as in the Regional Institute of Ophthalmology, Kolkata. Among 2317 students examined, 582 (25.11%) were suffering from refractive errors, myopia being the commonest (n = 325; 14.02%). Astigmatism affected 91 children (3.93%). There is an increase of prevalence of refractive errors with increase of age, but it is not statistically significant (p > 0.05). There is also no significant difference of refractive errors between boys and girls. PMID:17822183

  15. The Risk of Contact Lens Wear and the Avoidance of Complications

    Directory of Open Access Journals (Sweden)

    Farihah Tariq

    2013-11-01

    Full Text Available Contact lenses are lenses placed on the surface of the cornea to correct refractive errors such as myopia (short-sightedness, hypermetropia (far-sightedness and astigmatism. Lens-related complications are becoming a greater health concern as increasing number of individuals are using them as an alternative to spectacles. Contact lenses alter the natural ocular environment and reduce the efficacy of the innate defences. Although many complications are minor, microbial keratitis is potentially blinding and suspected cases should be rapidly diagnosed and referred to an ophthalmologist for treatment. Several risk factors have been identified with extended wear, poor hand hygiene, inadequate lens and lens-case care being the most significant. Promotion of good contact lens hygiene and practices are essential to reduce the adverse effects of contact lens wear.

  16. Distinguishing nonlinear processes in atomic media via orbital angular momentum transfer

    CERN Document Server

    Akulshin, Alexander M; Mikhailov, Eugeniy E; Novikova, Irina

    2014-01-01

    We suggest a technique based on the transfer of topological charge from applied laser radiation to directional and coherent optical fields generated in ladder-type excited atomic media to identify the major processes responsible for their appearance. As an illustration, in Rb vapours we analyse transverse intensity and phase profiles of the forward-directed collimated blue and near-IR light using self-interference and astigmatic transformation techniques when either or both of two resonant laser beams carry orbital angular momentum. Our observations unambiguously demonstrate that emission at 1.37 {\\mu}m is the result of a parametric four-wave mixing process involving only one of the two applied laser fields.

  17. Spatial shaping for generating arbitrary optical dipoles traps for ultracold degenerate gases

    CERN Document Server

    Lee, Jeffrey G

    2014-01-01

    We present two spatial-shaping approaches -- phase and amplitude -- for creating two-dimensional optical dipole potentials for ultracold neutral atoms. When combined with an attractive or repulsive Gaussian sheet formed by an astigmatically focused beam, atoms are trapped in three dimensions resulting in planar confinement with an arbitrary network of potentials -- a free-space atom chip. The first approach utilizes an adaptation of the generalized phase-contrast technique to convert a phase structure embedded in a beam after traversing a phase mask, to an identical intensity profile in the image plane. Phase masks, and a requisite phase-contrast filter, can be chemically etched into optical material (e.g., fused silica) or implemented with spatial light modulators; etching provides the highest quality while spatial light modulators enable prototyping and realtime structure modification. This approach was demonstrated on an ensemble of thermal atoms. Amplitude shaping is possible when the potential structure ...

  18. Contact lens fitting in a patient with Alport syndrome and posterior polymorphous corneal dystrophy: a case report

    Directory of Open Access Journals (Sweden)

    Juliana Maria da Silva Rosa

    2016-02-01

    Full Text Available ABSTRACT Alport Syndrome is a hereditary disease that is caused by a gene mutation and affects the production of collagen in basement membranes; this condition causes hemorrhagic nephritis associated with deafness and ocular changes. The X-linked form of this disease is the most common and mainly affects males. Typical ocular findings are dot-and-fleck retinopathy, anterior lenticonus, and posterior polymorphous corneal dystrophy. Some cases involving polymorphous corneal dystrophy and corneal ectasia have been previously described. Here we present a case report of a 33-year-old female with Alport syndrome, posterior polymorphous corneal dystrophy, and irregular astigmatism, whose visual acuity improved with a rigid gas permeable contact lens.

  19. Corneal topographic changes after 20-gauge pars plana vitrectomy associated with scleral buckling for the treatment of rhegmatogenous retinal detachment

    Directory of Open Access Journals (Sweden)

    Alexandre Achille Grandinetti

    2013-04-01

    Full Text Available PURPOSE: To evaluate the changes in corneal topography after 20-gauge pars plana vitrectomy associated with scleral buckling for the repair of rhegmatogenous retinal detachment. METHODS: Twenty-five eyes of 25 patients with rhegmatogenous retinal detachment were included in this study. 20-gauge pars plana vitrectomy associated with scleral buckling was performed in all patients. The corneal topography of each was measured before surgery and one week, one month, and three months after surgery by computer-assisted videokeratoscopy. RESULTS: A statistically significant central corneal steepening (average, 0,9 D , p<0,001 was noted one week after surgery. The total corneal astigmatism had a significant increase in the first postoperative month (p=0,007. All these topographic changes persisted for the first month but returned to preoperative values three months after the surgery. CONCLUSION: Pars plana vitrectomy with scleral buckling was found to induce transient changes in corneal topography.

  20. KERATOCONUS AND EPI-OFF CORNEAL CROSS-LINKING BY RIBOFLAVIN-ULTRAVIOLET TYPE A: INDICATIONS AND RATIONAL OF EMPLOYMENT

    Directory of Open Access Journals (Sweden)

    A. Caporossi

    2010-11-01

    Full Text Available Keratoconus is the most common dystrophic corneal ectasia, characterized by the presence of irregular astigmatism associated with a reduction of corneal thickness. It is the leading cause of corneal transplant in Italy and Europe. Recently a new therapeutic opportunity is offered by Riboflavin + UV A Corneal Cross-linking, first introduced in Italy in 2004 by Professor Aldo Caporossi at the Department of Ophthalmology of Siena. This treatment requires early diagnosis to prevent corneal ectatic modifications related to pathology. The modern treatment of keratoconus is directed into three "directories": 1 prevention of its progression; 2 reduction of the related refractive defect and induced corneal aberrations; 3 replacement of ectatic corneal in advanced phase not subjected to conservative approach and HRGP lens intolerance. Riboflavin + UV A Collagen Cross-linking is mostly indicated in patients between 10 and 26 years old with progressive keratoconus (stage 1 and 2 with strict adherence to the recommended inclusion thickness (thinnest point > 400 microns.

  1. Velocity map imaging of a slow beam of ammonia molecules inside a quadrupole guide

    CERN Document Server

    Pérez, Marina Quintero; Bethlem, Hendrick L

    2012-01-01

    Velocity map imaging inside an electrostatic quadrupole guide is demonstrated. By switching the voltages that are applied to the rods, the quadrupole can be used for guiding Stark decelerated molecules and for extracting the ions. The extraction field is homogeneous along the axis of the quadrupole while it defocuses the ions in the direction perpendicular to both the axis of the quadrupole and the axis of the ion optics. To compensate for this astigmatism, a series of planar electrodes with horizontal and vertical slits is used. A velocity resolution of 35 m/s is obtained. It is shown that signal due to thermal background can be eliminated, resulting in the detection of slow molecules with an increased signal-to-noise ratio. As an illustration of the resolving power, we have used the velocity map imaging system to characterize the phase-space distribution of a Stark decelerated ammonia beam.

  2. Velocity map imaging of a slow beam of ammonia molecules inside a quadrupole guide.

    Science.gov (United States)

    Quintero-Pérez, Marina; Jansen, Paul; Bethlem, Hendrick L

    2012-07-21

    Velocity map imaging inside an electrostatic quadrupole guide is demonstrated. By switching the voltages that are applied to the rods, the quadrupole can be used for guiding Stark decelerated molecules and for extracting the ions. The extraction field is homogeneous along the axis of the quadrupole, while it defocuses the ions in the direction perpendicular to both the axis of the quadrupole and the axis of the ion optics. To compensate for this astigmatism, a series of planar electrodes with horizontal and vertical slits is used. A velocity resolution of 35 m s(-1) is obtained. It is shown that signal due to thermal background can be eliminated, resulting in the detection of slow molecules with an increased signal-to-noise ratio. As an illustration of the resolving power we have used the velocity map imaging system to characterize the phase-space distribution of a Stark decelerated ammonia beam. PMID:22652864

  3. Polyplanar optic display

    Energy Technology Data Exchange (ETDEWEB)

    Veligdan, J.; Biscardi, C.; Brewster, C.; DeSanto, L. [Brookhaven National Lab., Upton, NY (United States). Dept. of Advanced Technology; Beiser, L. [Leo Beiser Inc., Flushing, NY (United States)

    1997-07-01

    The Polyplanar Optical Display (POD) is a unique display screen which can be used with any projection source. This display screen is 2 inches thick and has a matte black face which allows for high contrast images. The prototype being developed is a form, fit and functional replacement display for the B-52 aircraft which uses a monochrome ten-inch display. The new display uses a 100 milliwatt green solid state laser (532 nm) as its optical source. In order to produce real-time video, the laser light is being modulated by a Digital Light Processing (DLP{trademark}) chip manufactured by Texas Instruments, Inc. A variable astigmatic focusing system is used to produce a stigmatic image on the viewing face of the POD. In addition to the optical design, the authors discuss the electronic interfacing to the DLP{trademark} chip, the opto-mechanical design and viewing angle characteristics.

  4. Laser-driven polyplanar optic display

    Energy Technology Data Exchange (ETDEWEB)

    Veligdan, J.T.; Biscardi, C.; Brewster, C.; DeSanto, L. [Brookhaven National Lab., Upton, NY (United States). Dept. of Advanced Technology; Beiser, L. [Leo Beiser Inc., Flushing, NY (United States)

    1998-01-01

    The Polyplanar Optical Display (POD) is a unique display screen which can be used with any projection source. This display screen is 2 inches thick and has a matte-black face which allows for high contrast images. The prototype being developed is a form, fit and functional replacement display for the B-52 aircraft which uses a monochrome ten-inch display. The new display uses a 200 milliwatt green solid-state laser (532 nm) as its optical source. In order to produce real-time video, the laser light is being modulated by a Digital Light Processing (DLP) chip manufactured by Texas Instruments, Inc. A variable astigmatic focusing system is used to produce a stigmatic image on the viewing face of the POD. In addition to the optical design, the authors discuss the DLP chip, the optomechanical design and viewing angle characteristics.

  5. Kabuki make-up (Niikawa-Kuroki) syndrome in five Spanish children

    Energy Technology Data Exchange (ETDEWEB)

    Galan-Gomez, E.; Cardesa-Garcia, J.J. Campo-Sampedro, F.M. [Universidad de Extremadura, Badajos (Spain)] [and others

    1995-11-20

    We describe 5 Spanish children with Kabuki make-up syndrome (KMS) - 3 females and 2 males - identified in Badajoz, Spain, between 1988 and 1990. All had the characteristic clinical and radiological manifestations of the syndrome. Psychomotor/mental retardation, postnatal growth deficiency, distinctive facial appearance, sagittal vertebral clefts, and dermatoglyphic abnormalities were present in all 5. Congenital heart defects were present in 4 patients. In addition, one had myopia, astigmatism, and bilateral paralysis of the VI cranial nerve. Another had apparent fusion of the hamate and capitate. An additional patient, as well as his mother, had an apparently balanced 15/17 translocation. The fact that these patients were ascertained in a catchment area of approximately 250,000 inhabitants and in a relatively limited period of time suggests that the prevalence of the KMS may be higher than previously recognized. 30 refs., 6 figs., 2 tabs.

  6. Impact of primary aberrations on coherent lidar performance

    DEFF Research Database (Denmark)

    Hu, Qi; Rodrigo, Peter John; Iversen, Theis Faber Quist;

    2014-01-01

    In this work we investigate the performance of a monostatic coherent lidar system in which the transmit beam is under the influence of primary phase aberrations: spherical aberration (SA) and astigmatism. The experimental investigation is realized by probing the spatial weighting function...... of the lidar system using different optical transceiver configurations. A rotating belt is used as a hard target. Our study shows that the lidar weighting function suffers from both spatial broadening and shift in peak position in the presence of aberration. It is to our knowledge the first experimental...... effciency, the optimum truncation of the transmit beam and the spatial sensitivity of a CW coherent lidar system. Under strong degree of aberration, the spatial confinement is significantly degraded. However for SA, the degradation of the spatial confinement can be reduced by tuning the truncation...

  7. The Possible Role of Peripheral Refraction in Development of Myopia.

    Science.gov (United States)

    Atchison, David A; Rosén, Robert

    2016-09-01

    Recent longitudinal studies do not support the current theory of relative peripheral hyperopia causing myopia. The theory is based on misunderstanding of the Hoogerheide et al. article of 1971, which actually found relative peripheral hyperopia to be present after, rather than before, myopia development. The authors present two alternative theories of the role of peripheral refraction in the development and progression of myopia. The one for which most detail is given is based on cessation of ocular growth when the periphery is at an emmetropic stage as determined by equivalent blur of the two line foci caused by oblique astigmatism. This paper is based on an invited commentary on the role of lens treatments in myopia from the 15th International Myopia Conference in Wenzhou, China in September 2015. PMID:27560691

  8. Compact MEMS-based Adaptive Optics Optical Coherence Tomography for Clinical Use

    Energy Technology Data Exchange (ETDEWEB)

    Chen, D; Olivier, S; Jones, S; Zawadzki, R; Evans, J; Choi, S; Werner, J

    2008-02-04

    We describe a compact MEMS-based adaptive optics (AO) optical coherence tomography system with improved AO performance and ease of clinical use. A typical AO system consists of a Shack-Hartmann wavefront sensor and a deformable mirror that measures and corrects the ocular and system aberrations. Because of the limitation on the current deformable mirror technologies, the amount of real-time ocular-aberration compensation is restricted and small in the previous AO-OCT instruments. In this instrument, we proposed to add an optical apparatus to correct the spectacle aberrations of the patients such as myopia, hyperopia and astigmatism. This eliminated the tedious process of the trial lenses in clinical imaging. Different amount of spectacle aberration compensation was achieved by motorized stages and automated with the AO computer for ease of clinical use. In addition, the compact AO-OCT was optimized to have minimum system aberrations to reduce AO registration errors and improve AO performance.

  9. Laser in ophthalmology. Laser i oftalmologien

    Energy Technology Data Exchange (ETDEWEB)

    Syrdalen, P. (Rikshospitalet, Oslo (Norway))

    1991-09-01

    The article presents a brief history of the use of laser in ophthalmology in Norway, from the introduction of the first argon-photocoalulator in 1972 to the excimer laser in 1990. The argon-photocoagulator is in daily us in all Eye Departments in Norway and the main group of patients treated are those with diabetic retionopathy. Glaucoma has been treated with argon-laser with good results for the last ten years. YAG-laser, introduced in Norway in 1985, is used to treat secondary cataracts which occur after extracapsular cataract extractions and implantation of artificial lenses. In 1990, the excimer laser was introduced for refractive surgery (myopia, astigmatism). 4 refs., 6 figs., 1 tab.

  10. Phototherapeutic Keratectomy Combined with Photorefractive Keratectomy for Treatment of Myopia with Corneal Scars

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    To evaluate the effect of phototherapeutic keratectomy combined with photorefractive keratectomy in the treatment of myopia with corneal scars, corneal epithelium was removed with laser plus scraping. Corneal scars were removed with PTK, followed by PRK for myopia. Healon was used to make corneal surface smoother during operation. 30 eyes of 24 cases of myopia with corneal scars were followed up for one year. Mean corrected vision was 0. 51 and myopic degree was -6.42D ?4.26D before operation. After operation, corneal scars of 21 eyes (70.0?) were removed in operative zone. The vision of 27 operated eyes (90. 0 %) was equal to or better than best corrected vision. Mean postoperative visual acuity was 0. 72. Corneal surface was smoother and astigmatism was reduced after the surgery. Our study showed that PTK combined with PRK is a safe and effective treatment for myopia with corneal scars.

  11. Paediatric nasal polyps in cystic fibrosis.

    Science.gov (United States)

    Mohd Slim, Mohd Afiq; Dick, David; Trimble, Keith; McKee, Gary

    2016-01-01

    Patients with cystic fibrosis (CF) are at increased risk of nasal polyps. We present the case of a 17-month-old Caucasian patient with CF who presented with hypertelorism causing cycloplegic astigmatism, right-sided mucoid discharge, snoring and noisy breathing. Imaging suggested bilateral mucoceles in the ethmoid sinuses. Intraoperatively, bilateral soft tissue masses were noted, and both posterior choanae were patent. Polypectomy and bilateral mega-antrostomies were performed. Histological examination revealed inflammatory nasal polyposis typical of CF. The role of early functional endoscopic sinus surgery (FESS) in children with CF nasal polyposis remains questionable as the recurrence rate is higher, and no improvement in pulmonary function has been shown. Our case, however, clearly demonstrates the beneficial upper airway symptom relief and normalisation of facial appearance following FESS in a child with this condition. PMID:27329094

  12. Comparative Study of Refractive Errors, Strabismus, Microsaccades, and Visual Perception Between Preterm and Full-Term Children With Infantile Cerebral Palsy.

    Science.gov (United States)

    Kozeis, Nikolaos; Panos, Georgios D; Zafeiriou, Dimitrios I; de Gottrau, Philippe; Gatzioufas, Zisis

    2015-07-01

    The purpose of this study was to examine the refractive status, orthoptic status and visual perception in a group of preterm and another of full-term children with cerebral palsy, in order to investigate whether prematurity has an effect on the development of refractive errors and binocular disorders. A hundred school-aged children, 70 preterm and 30 full-term, with congenital cerebral palsy were examined. Differences for hypermetropia, myopia, and emmetropia were not statistically significant between the 2 groups. Astigmatism was significantly increased in the preterm group. The orthoptic status was similar for both groups. Visual perception was markedly reduced in both groups, but the differences were not significant. In conclusion, children with cerebral palsy have impaired visual skills, leading to reading difficulties. The presence of prematurity does not appear to represent an additional risk factor for the development of refractive errors and binocular disorders. PMID:25296927

  13. Genetic and environmental factors in orientation anisotropy: a field study in the British Isles.

    Science.gov (United States)

    Ross, H E; Woodhouse, J M

    1979-01-01

    Visual acuity for the detection of gratings at four orientations was measured for groups of ten boys and ten girls aged five to seven years, from the following four populations: Scots in Glasgow, Pakistanis in Glasgow, Gaels in Stornoway (Outer Hebrides) and East Anglians in Littleport (Cambridgeshire fenlands). The Glaswegians, both Scottish and Pakistani, showed the normal pattern of anisotropy, with poorest acuity for oblique orientations; the East Anglians showed no significant anisotropy; while the Gaels were unusual in showing poorest horizontal acuity. A group of fourteen Pakistani children in Stornoway differed slightly from a matched group of Gaels. The group differences bore little relation to the visual environments, and were probably due to genetic or cultural factors. The relatively poor horizontal acuity of the Gaels was not correlated with astigmatism. Sex differences were also found, with the boys showing higher mean acuity and a higher ratio between vertical and oblique acuity. PMID:503780

  14. Toric implantable collamer lens for keratoconus

    Directory of Open Access Journals (Sweden)

    Mathew Kurian Kummelil

    2013-01-01

    Full Text Available Keratoconus is a progressive non-inflammatory thinning of the cornea that induces myopia and irregular astigmatism and decreases the quality of vision due to monocular diplopia, halos, or ghost images. Keratoconus patients unfit for corneal procedures and intolerant to refractive correction by spectacles or contact lenses have been implanted toric posterior chamber phakic intraocular lenses (PC pIOLs alone or combined with other surgical procedures to correct the refractive errors associated with keratoconus as an off label procedure with special informed consent from the patients. Several reports attest to the safety and efficacy of the procedure, though the associated corneal higher order aberrations would have an impact on the final visual quality.

  15. Femtosecond laser enabled keratoplasty for advanced keratoconus

    Directory of Open Access Journals (Sweden)

    Yathish Shivanna

    2013-01-01

    Full Text Available Purpose : To assess the efficacy and advantages of femtosecond laser enabled keratoplasty (FLEK over conventional penetrating keratoplasty (PKP in advanced keratoconus. Materials and Methods: Detailed review of literature of published randomized controlled trials of operative techniques in PKP and FLEK. Results: Fifteen studies were identified, analyzed, and compared with our outcome. FLEK was found to have better outcome in view of better and earlier stabilization uncorrected visual acuity (UCVA, best corrected visual acuity (BCVA, and better refractive outcomes with low astigmatism as compared with conventional PKP. Wound healing also was noticed to be earlier, enabling early suture removal in FLEK. Conclusions: Studies relating to FLEK have shown better results than conventional PKP, however further studies are needed to assess the safety and intraoperative complications of the procedure.

  16. Evaluation of stereopsis in different type of ametropic amblyopia children%不同类型屈光不正性弱视儿童的立体视觉

    Institute of Scientific and Technical Information of China (English)

    李珊珊; 黄馨慧; 邱斌; 叶晗; 戴锦晖

    2010-01-01

    目的 了解屈光不正性弱视儿童立体视觉的状况.方法 对4~8岁,平均(5.2±1.8)岁,205例屈光不正性弱视儿童(其中散光性弱视65例、近视性30例、远视性110例),应用颜少明等随机立体检查图及同视机,检测不同类型屈光不正性弱视儿童远融合范围、远近立体视、近零视差、交叉视差、非交叉视差立体感知度.结果 轻、中度屈光不正性弱视三种类型近零视差差异有统计学意义,远视性弱视较小,近视性次之,散光性最差(P均<0.05);远立体视有显著差异,远视性较好散光性较差(P均<0.05);重度弱视3型近零视差和远立体视均差异无统计学意义(P>0.05);远融合范围3型差异无统计学意义(P>0.05).弱视程度对弱视患者三级视功能有明显影响(P<0.05),程度越重影响越大.结论 弱视影响儿童期立体视觉建立,散光性弱视对立体视觉的影响大于近视性、远视性弱视儿童.%Objective To evaluate the stereopsis in different types of ametropic amblyopic children.Methods A total of 205 children between 4-8 years old with recovered ametropic amblyopia, including 65 of astigmatic amblyopia and 30 of myopic and 110 of hypermetropic, were involved in the subject. Using Yan's stereogram random dot synptophore stereogram and synoptophore, the distance fusion range, distance stereoacuity, approximationg zero disparity of these children were observed separately. Results In mild and moderate amblyopia there was significant difference in approximationg zero disparity and distance stereoacuity among astigmatic amblyopia and myopic and hypermetropic, within which astigmatic amblyopia the worst and hypermetropic amblyopia the best (P<0.05). No significant difference was found in the distance fusion range (P>0.05). Different type of ametropic amblyopic led no significant difference in severe amblyopia (P>0.05) which caused worse influence to the stereopsis than mild and moderate degree (P

  17. Working Beyond the Static Limits of Laser Stability by Use of Adaptive and Polarization-Conjugation Optics

    Science.gov (United States)

    Moshe, Inon; Jackel, Steven; Lallouz, Raphael

    1998-09-01

    Strong thermo-optical aberrations in flash lamp-pumped Nd:Cr:GSGG rods were corrected to yield TEM 00 output at twice the efficiency of Nd:YAG. A hemispherical resonator operating at the limit of stability was employed. As much as 3 W of average power in a Gaussian beam ( M 2 1 ) was generated. Unique features were zero warm-up time and the ability to vary the repetition rate without varying energy, near- and far-field profiles, or polarization purity. Thermal focusing and astigmatism were corrected with a microprocessor-controlled adaptive-optics backmirror composed of discrete elements (variable-radius mirror). A reentrant resonator coupled polarizer losses back into the laser rod and corrected depolarization.

  18. Dynamic compensation of thermal lensing and birefringence in a high-brightness Nd:Cr:GSGG oscillator

    Science.gov (United States)

    Moshe, Inon; Jackel, Steven M.; Lallouz, Raphael; Tzuk, I.

    1997-09-01

    In this work, five fundamental concepts were combined to a low development of high efficiency, low divergence, narrow bandwidth, flashlamp pumped oscillators capable of operation over a broad operating range. These concepts were: flashlamp pumped Nd:Cr:GSGG to achieve high efficiency, a 'Reentrant Cavity' to eliminate birefringence losses, a variable radius back mirror in a hemispherical cavity to achieve maximum Gaussian beam fill factor, a very high damage threshold, spectrum narrowing output coupler fabricated using a stack of uncoated etalons to form a resonant reflector, a cylindrical zoom lens to completely eliminate astigmatism. The results were successful, and yielded an oscillator that produced 10 mJ, TEM00 300 MHz bandwidth, 75 ns pulses, over a repetition rate of 1-20 Hz, and at a slope efficiency of 2 percent. These techniques were also successfully applied to a YLF oscillator. They may, in part, be adapted for use to unstable resonators.

  19. Comparison of Adaptive Optics and Phase-Conjugate Mirrors for Correction of Aberrations in Double-Pass Amplifiers

    Science.gov (United States)

    Jackel, Steven; Moshe, Inon; Lavi, Raphy

    2003-02-01

    Correction of birefringence-induced effects (depolarization and bipolar focusing) were achieved in double-pass amplifiers by use of a Faraday rotator between the laser rod and the retroreflecting optic. A necessary condition was ray retrace. Retrace was limited by imperfect conjugate-beam fidelity and by nonreciprocal refractive indices. We compared various retroreflectors: stimulated-Brillouin-scatter phase-conjugate mirrors (PCMs), PCMs with rod-to-PCM relay imaging (IPCM), IPCMs with astigmatism-correcting adaptive optics, and all-adaptive-optics imaging variable-radius mirrors. Results with flash-lamp-pumped, Nd:Cr:GSGG double-pass amplifiers showed the superiority of adaptive optics over nonlinear optics retroreflectors in terms of maximum average power, improved beam quality, and broader oscillator pulse duration /bandwidth operating range. Hybrid PCM-adaptive optics retroreflectors yielded intermediate power /beam-quality results.

  20. THERMAL LENSING MEASUREMENTS IN THE ANISOTROPIC LASER CRYSTALS UNDER DIODE PUMPING

    Directory of Open Access Journals (Sweden)

    P. A. Loiko

    2012-01-01

    Full Text Available An experimental setup was developed for thermal lensing measurements in the anisotropic diode-pumped laser crystals. The studied crystal is placed into the stable two-mirror laser cavity operating at the fundamental transversal mode. The output beam radius is measured with respect to the pump intensity for different meridional planes (all these planes contain the light propagation direction. These dependencies are fitted using the ABCD matrix method in order to obtain the sensitivity factors showing the change of the optical power of thermal lens due to variation of the pump intensity. The difference of the sensitivity factors for two mutually orthogonal principal meridional planes describes the thermal lens astigmatism degree. By means of this approach, thermal lensing was characterized in the diode-pumped monoclinic Np-cut Nd:KGd(WO42 laser crystal at the wavelength of 1.067 μm for light polarization E || Nm.

  1. Assessment of diagnostic value of age for meridional amblyopia with Logistic regression and receiver operating characteristic curve%应用Logistic回归和ROC曲线评价患者年龄对儿童子午线性弱视诊断的影响

    Institute of Scientific and Technical Information of China (English)

    李辉; 许江涛; 蒋晓明; 周莹

    2013-01-01

    目的:应用Logistic多元回归分析和ROC曲线探讨年龄因素对诊断儿童子午线弱视有无影响.方法:研究对象为2008/2011年间在我院眼科门诊就诊,以散光为主要屈光异常并排除屈光参差及斜视的4~8岁儿童共1 005例1 910眼.采用Logistic多元回归分析年龄、性别、柱镜绝对值程度、球镜绝对值程度、散光类型对诊断子午线性弱视的影响,通过ROC曲线下面积(area under the ROC curve,AUC)分析进一步明确患者年龄因素对诊断子午线弱视的影响.结果:分别建立Logistic 回归模型1(包括性别、柱镜绝对值程度、球镜绝对值程度、散光类型四个变量)和模型2(前四个变量再加上年龄).两个模型的Logistic 回归分析都提示柱镜绝对值程度是诊断子午线性弱视的影响因素,模型2 的Logistic 回归分析同时提示年龄是诊断子午线性弱视的影响因素.模型1的AUC为0.64,模型2的AUC为0.74,两者比较有统计学差异(Por = 1. 00D and sphere < or = 3. 00D were present in one or both eyes. The difference of sphere between both eyes was less 1. 50D. The difference of astigmatism between both eyes was less 1. 00D. All astigmatism was calculated by the absolute value. By analyzing age, sex, astigmatism type, diopter of cylinder and diopter of sphere with Logistic regression, two mathematical models were established. Then the diagnostic efficacy of the model was assessed using the ROC curve.RESULTS: The model 1 included 4 parameters (sex, astigmatism type, diopter of cylinder and diopter of sphere). The model 2 included 5 parameters (the 4 parameters of the model 1 adding age). Using Logistic regression, the diopter of cylinder had an influence on the diagnosis of meridional amblyopia in two models. In model 2, age was another influencing factor on the diagnosis of meridional amblyopia. The model 1 area under ROC curve (AUC) was 0. 64, and the model 2 was 0.74. The area of model 2 was greater than the model 1

  2. Research on the Human Visual Indicators of Computer-Controlled Intelligence Acquisition System%人体视力指标计算机智能采集系统研究

    Institute of Scientific and Technical Information of China (English)

    邢紫阳; 李明东; 彭鼎

    2010-01-01

    依据视力采集标准,结合计算机自动控制的特点,研究并分析了计算机智能采集系统的可行性及其测法推算.该系统可以采集到较真实、可靠的近视力值,能对色盲、色弱、散光进行鉴定,采集效率极高.%Based on the national standard about visual and the characteristics of computer automatic control , research and analysis of the human visual indicators of computer-controlled intelligence acquisition system and its measurement method have been studied. We can get a more realistic and reliable values of near sight and also can identify the color-blind and astigmatism with a high efficiency.

  3. Influence of wave-front aberrations on bit error rate in inter-satellite laser communications

    Science.gov (United States)

    Yang, Yuqiang; Han, Qiqi; Tan, Liying; Ma, Jing; Yu, Siyuan; Yan, Zhibin; Yu, Jianjie; Zhao, Sheng

    2011-06-01

    We derive the bit error rate (BER) of inter-satellite laser communication (lasercom) links with on-off-keying systems in the presence of both wave-front aberrations and pointing error, but without considering the noise of the detector. Wave-front aberrations induced by receiver terminal have no influence on the BER, while wave-front aberrations induced by transmitter terminal will increase the BER. The BER depends on the area S which is truncated out by the threshold intensity of the detector (such as APD) on the intensity function in the receiver plane, and changes with root mean square (RMS) of wave-front aberrations. Numerical results show that the BER rises with the increasing of RMS value. The influences of Astigmatism, Coma, Curvature and Spherical aberration on the BER are compared. This work can benefit the design of lasercom system.

  4. Effects of Turbulent Aberrations on Probability Distribution of Orbital Angular Momentum for Optical Communication

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yi-Xin; CANG Ji

    2009-01-01

    Effects of atmospheric turbulence tilt, defocus, astigmatism and coma aberrations on the orbital angular mo-mentum measurement probability of photons propagating in weak turbulent regime are modeled with Rytov approximation. By considering the resulting wave as a superposition of angular momentum eigenstates, the or-bital angular momentum measurement probabilities of the transmitted digit axe presented. Our results show that the effect of turbulent tilt aberration on the orbital angular momentum measurement probabilities of photons is the maximum among these four kinds of aberrations. As the aberration order increases, the effects of turbulence aberrations on the measurement probabilities of orbital angular momentum generally decrease, whereas the effect of turbulence defoens can be ignored. For tilt aberration, as the difference between the measured orbital angular momentum and the original orbital angular momentum increases, the orbital angular momentum measurement probabifity decreases.

  5. Corneal Topographical Changes Flollowing Strabismus Surgery

    Institute of Scientific and Technical Information of China (English)

    MaiGH; WangZ

    1999-01-01

    Purpose:To study corneal topographical changes after strabismus surgery.Methods:Computer-aided corneal topography was used in 43 strabismus patients(45 eyes)one or two days prior to and six or seven ays after strabismus surgery.The spherical and cylindrical equivalents were calculated based on the simulated keratometry.Results:After the surgery,only the changes at 3mm in the inferior quadrant were statistically significant.The changes at 3mm in the rest quadrants and the changes at 7mm were no significant.Significant changes in spherical equivalent were found post-operatively.neither the horizontal nor the verical meridional equivalent showed significant changes after surgery.Conclusions:The results of corneal topographical changes following strabismus surgery in our preliminary study indicated the little effect of strabismus surgery on corneal curvature and corneal astigmatism.

  6. Study of X-ray Kirkpatrick-Baez imaging with single layer

    Institute of Scientific and Technical Information of China (English)

    Baozhong Mu; Zhanshan Wang; Shengzhen Yi; Xin Wang; Shengling Huang; Jingtao Zhu; Chengchao Huang

    2009-01-01

    The X-ray Kirkpatrick-Baez(KB)imaging experiment with single layer is implemented.Based on the astigmatism aberration and residual geometric aberration of a single mirror.a KB system with 16x mean magnification and approxinlately 0.45° grazing incidence angle is designed.The mirrors are deposited with an Ir layer of 20-nm thickness.Au grids backlit by X-ray tube of 8 keV are imaged via the KB system on scintillator charge-coupled device(CCD).In the ±80 μm field,resolutions of less than 5 μm are measured.The result is in good agreenmnt with the simulated imaging.

  7. Retinal optical coherence tomography study on children with anisometropia monocular amblyopia%屈光参差性弱视儿童视网膜光学相干断层成像研究

    Institute of Scientific and Technical Information of China (English)

    初翠英; 代春华; 宋修芬; 纪芳; 蒋广伟; 姜善好

    2014-01-01

    目的:应用视网膜光学相干断层成像方法(OCT)研究屈光参差性弱视儿童视网膜神经纤维层(RNFL)和黄斑中心凹厚度,探讨弱视的发病机制。方法对屈光参差性单眼弱视儿童38例进行OCT检查,据弱视眼屈光状态分为远视散光弱视组18例,单纯远视弱视组20例,对侧健眼为正常对照组。分析比较三组视盘周围RNFL厚度和黄斑中心凹厚度的差异。结果远视散光弱视组、单纯远视弱视组和正常对照组视盘周围RNFL厚度分别为115.77±13.42μm、111.34±10.30μm 和103.05±11.10μm,黄斑中心凹厚度分别为198.86±28.30μm、191.98±27.81μm,181.18±29.06μm。两弱视组分别与正常对照组、两弱视组组间比较视盘周围RNFL厚度及黄斑中心凹厚度,差异均有统计学意义,P<0.05。结论屈光参差性弱视其弱视眼视盘周围RNFL厚度及黄斑中心凹厚度较对侧正常眼增厚,且远视散光弱视眼厚于单纯远视弱视眼。%Objective To assess retinal nerve fiber layer and the fovea in children with anisometropic am-blyopia by optical coherence tomography(OCT). Methods OCT was performed on 38 children with anisometropic am-blyopia. 18 children were astigmatic amblyopia and 20 children were hypermetropic amblyopia. The thickness of peri-papillary region retinal nerve fiber layer and the fovea were recorded and analyzed among amblyopia eyes and normal eyes. Results The thickness of mean peripapillary region RNFL and fovea were 115.77±13.42μm, 111.34±10.30μm, 103.05±11.10μm and 198.86±28.30μm, 191.98±27.81μm, 181.18±29.06μm respectively in the astigmatic amblyopia, hypermetropic amblyopia and normal eyes. The RNFL and fovea thickness in amblyopic eyes were thicker than those in normal eyes, and the RNFL and fovea thickness in astigmatic amblyopia were thicker than that in hypermetropic amblyopia, P < 0.05. Conclusions The thickness of RNFL and fovea in anisometropic amblyopia eyes were

  8. A Case of Congenital Retinal Macrovessel Crossing the Foveola

    Directory of Open Access Journals (Sweden)

    Cem Özgönül

    2014-03-01

    Full Text Available Congenital retinal macrovessel is generally the presence of unilateral aberrant vessel crossing over the horizontal raphe through the macula. Typically, visual acuity is unaffected, although in rare cases, macular hemorrhage, foveolar cysts, foveal contour impairment, and the presence of anomalous vessel in the foveola can affect the vision. In our case, visual acuity of the right eye was counting fingers at 3 meters. He had four diopter oblique astigmatism, esotropia, and dissociated vertical deviation. Fundoscopy revealed a aberrant vein crossing the foveola. Spectral OCT examination showed hiperreflectivity of the vessel and fluorescein angiography showed no leakage of the vessel. Although in the literature it is specified that the aberrant vein crossing the fovea is a factor of lowering visual acuity, in our case we thought, low visual acuity is due to deep amblyopia. (Turk J Ophthalmol 2014; 44: 154-5

  9. Cost-effective solar furnace system using fixed geometry Non-Imaging Focusing Heliostat and secondary parabolic concentrator

    Energy Technology Data Exchange (ETDEWEB)

    Chong, K.K.; Lim, C.Y.; Hiew, C.W. [Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Off Jalan Genting Kelang, Setapak, Kuala Lumpur 53300 (Malaysia)

    2011-05-15

    A novel cost-effective solar furnace system is proposed to be consisted of a Non-Imaging Focusing Heliostat (NIFH) and a much smaller parabolic concentrator. In order to simplify the design and hence leading to the cost reduction, a fixed geometry of the NIFH heliostat is adopted in the novel solar furnace system by omitting the requirement of continuous astigmatic correction throughout the year with the use of local controllers. The performance of this novel solar furnace configuration can be optimized when the heliostat's spinning-axis is orientated in such a way that the annual variations of incident angle and therefore the annual variations of aberrant image size are the least. To verify the new configuration, a prototype solar furnace has been constructed at Universiti Tunku Abdul Rahman. (author)

  10. AO-OCT for in vivo mouse retinal imaging: Application of adaptive lens in wavefornt sensorless aberration correction

    Science.gov (United States)

    Bonora, Stefano; Jian, Yifan; Pugh, Edward N.; Sarunic, Marinko V.; Zawadzki, Robert J.

    2014-03-01

    We demonstrate Adaptive optics - Optical Coherence Tomography (OCT) with modal sensorless Adaptive Optics correction with the use of novel Adaptive Lens (AL) applied for in-vivo imaging of mouse retinas. The AL can generate low order aberrations: defocus, astigmatism, coma and spherical aberration that were used in an adaptive search algorithm. Accelerated processing of the OCT data with a Graphic Processing Unit (GPU) permitted real time extraction of image projection total intensity for arbitrarily selected retinal depth plane to be optimized. Wavefront sensorless control is a viable option for imaging biological structures for which AOOCT cannot establish a reliable wavefront that could be corrected by wavefront corrector. Image quality improvements offered by adaptive lens with sensorless AO-OCT was evaluated on in vitro samples followed by mouse retina data acquired in vivo.

  11. Intraocular lens design for treating high myopia based on individual eye model

    Science.gov (United States)

    Wang, Yang; Wang, Zhaoqi; Wang, Yan; Zuo, Tong

    2007-02-01

    In this research, we firstly design the phakic intraocular lens (PIOL) based on individual eye model with optical design software ZEMAX. The individual PIOL is designed to correct the defocus and astigmatism, and then we compare the PIOL power calculated from the individual eye model with that from the experiential formula. Close values of PIOL power are obtained between the individual eye model and the formula, but the suggested method has more accuracy with more functions. The impact of PIOL decentration on human eye is evaluated, including rotation decentration, flat axis decentration, steep axis decentration and axial movement of PIOL, which is impossible with traditional method. To control the PIOL decentration errors, we give the limit values of PIOL decentration for the specific eye in this study.

  12. High-resolution, flat-field, plane-grating, f/10 spectrograph with off-axis parabolic mirrors.

    Science.gov (United States)

    Schieffer, Stephanie L; Rimington, Nathan W; Nayyar, Ved P; Schroeder, W Andreas; Longworth, James W

    2007-06-01

    A high-resolution, flat-field, plane-grating, f/10 spectrometer based on the novel design proposed by Gil and Simon [Appl. Opt. 22, 152 (1983)] is demonstrated. The spectrometer design employs off-axis parabolic collimation and camera mirrors in a configuration that eliminates spherical aberrations and minimizes astigmatism, coma, and field curvature in the image plane. In accordance with theoretical analysis, the performance of this spectrometer achieves a high spatial resolution over the large detection area, which is shown to be limited only by the quality of its optics and their proper alignment within the spatial resolution of a 13 microm x 13 microm pixelated CCD detector. With a 1500 lines/mm grating in first order, the measured spectral resolving power of lambda/Dlambda = 2.5(+/-0.5) x 10(4) allows the clear resolution of the violet Ar(I) doublet at 419.07 and 419.10 nm.

  13. Microchip laser operation of Tm,Ho:KLu(WO₄)₂ crystal.

    Science.gov (United States)

    Loiko, Pavel; Serres, Josep Maria; Mateos, Xavier; Yumashev, Konstantin; Kuleshov, Nikolai; Petrov, Valentin; Griebner, Uwe; Aguiló, Magdalena; Díaz, Francesc

    2014-11-17

    A microchip laser is realized on the basis of a monoclinic Tm,Ho-codoped KLu(WO₄)₂crystal cut for light propagation along the Ng optical indicatrix axis. This crystal cut provides positive thermal lens with extremely weak astigmatism, S/M = 4%. High sensitivity factors, M = dD/dP(abs), of 24.9 and 24.1 m(-1)/W for the mg- and pg- tangential planes are calculated with respect to the absorbed pump power. Such thermo-optic behavior is responsible for mode stabilization in the plano-plano microchip laser cavity, as well as the demonstrated perfect circular beam profile (M(2) laser performance attributed to the increased up-conversion losses. PMID:25402038

  14. Comparative life test of 0.8-micron-laser diodes for SILEX under NRZ and QPPM modulation

    Science.gov (United States)

    Menke, Bodo; Loeffler, Roland

    1991-06-01

    The procedures and preliminary results of accelerated life tests performed within the framework of an evaluation program under the ESA contract are described. In order to calculate the activation energy and median lifetime and to investigate the drift behavior of optical parameters, a conventional three-temperature aging test at 30, 50, and 70 C is performed on 80 laser diodes in total, split into two subgroups operating under quaternary pulse position modulation (QPPM) and nonreturn-to-zero (NRZ) modulation at 16 Mbit/s with a PN-code length of (2 exp 7)-1. Measurements before and upon completion of the aging tests consist of P0/I curves, V/I characteristics, photo diode tracking ratios, spectra, mode hopping behaviors, far-field patterns, wave-front errors and astigmatisms, and linear polarization ratios.

  15. Vision improvement by correcting higher-order aberrations with customized soft contact lenses in keratoconic eyes

    Science.gov (United States)

    Sabesan, Ramkumar; Jeong, Tae Moon; Carvalho, Luis; Cox, Ian G.; Williams, David R.; Yoon, Geunyoung

    2007-04-01

    Higher-order aberration correction in abnormal eyes can result in significant vision improvement, especially in eyes with abnormal corneas. Customized optics such as phase plates and customized contact lenses are one of the most practical, nonsurgical ways to correct these ocular higher-order aberrations. We demonstrate the feasibility of correcting higher-order aberrations and improving visual performance with customized soft contact lenses in keratoconic eyes while compensating for the static decentration and rotation of the lens. A reduction of higher-order aberrations by a factor of 3 on average was obtained in these eyes. The higher-order aberration correction resulted in an average improvement of 2.1 lines in visual acuity over the conventional correction of defocus and astigmatism alone.

  16. Three-dimensional phenomena in microbubble acoustic streaming

    CERN Document Server

    Marin, Alvaro; Rallabandi, Bhargav; Wang, Cheng; Hilgenfeldt, Sascha; Kähler, Christian J

    2015-01-01

    Ultrasound-driven oscillating micro-bubbles have been used as active actuators in microfluidic devices to perform manifold tasks such as mixing, sorting and manipulation of microparticles. A common configuration consists on side-bubbles, created by trapping air pockets in blind channels perpendicular to the main channel direction. This configuration consists of acoustically excited bubbles with a semi-cylindrical shape that generate significant streaming flow. Due to the geometry of the channels, such flows have been generally considered as quasi two-dimensional. Similar assumptions are often made in many other microfluidic systems based on \\emph{flat} micro-channels. However, in this paper we show that microparticle trajectories actually present a much richer behavior, with particularly strong out-of-plane dynamics in regions close to the microbubble interface. Using Astigmatism Particle Tracking Velocimetry, we reveal that the apparent planar streamlines are actually projections of a \\emph{streamsurface} wi...

  17. Quality descriptors of optical beams based on centred reduced moments I spot analysis

    CERN Document Server

    Castaneda, R; García-Sucerquia, J

    2003-01-01

    A method for analyzing beam spots is discussed. It is based on the central reduced moments of the spot and its associated density functions. These functions allow us to separately analyze specific spot fractions, in such a way that specific combinations of higher order moments can be interpreted as coordinates of their centre of mass and the length and orientations of their principal axis. So, the descriptors of the associated density functions deal with the quantitative estimation of spot features, such as coma-like and astigmatism-like distortions. To assure high accuracy, background noise suppression and an optimal match of the spot support onto the region [-1,1]x[- 1,1] are performed prior to the calculation of the moments. Simulations were performed for illustrating the method.

  18. Aberration measurement from specific photolithographic images: a different approach.

    Science.gov (United States)

    Nomura, H; Tawarayama, K; Kohno, T

    2000-03-01

    Techniques for measurement of higher-order aberrations of a projection optical system in photolithographic exposure tools have been established. Even-type and odd-type aberrations are independently obtained from printed grating patterns on a wafer by three-beam interference under highly coherent illumination. Even-type aberrations, i.e., spherical aberration and astigmatism, are derived from the best focus positions of vertical, horizontal, and oblique grating patterns by an optical microscope. Odd-type aberrations, i.e., coma and three-foil, are obtained by detection of relative shifts of a fine grating pattern to a large pattern by an overlay inspection tool. Quantitative diagnosis of lens aberrations with a krypton fluoride (KrF) excimer laser scanner is demonstrated.

  19. Corneal injection track: an unusual complication of intraocular lens implantation and review

    Institute of Scientific and Technical Information of China (English)

    Julie; Y.C.Lok; Alvin; L.Young

    2015-01-01

    Phacoemulsification is the main gold standard for cataract operation in the developed world together with foldable intraocular lens(IOL) implantation by injection,allowing for stable wound construction and less postoperative astigmatism. It is a safe procedure with high success rate with the advancement in machines,improvement of IOL injection systems and further maturation of surgeons’ techniques. Despite the large number of operations performed every day, foldable IOL injection leading to an intra-stromal corneal track is a very rare complication. We report a case of this unusual finding in a 70-year-old gentleman who has undergone cataract operation in November 2011 in our hospital and will review on the complications related to foldable IOL injection.

  20. Schwarzschild-Couder two-mirror telescope for ground-based gamma-ray astronomy

    CERN Document Server

    Vasilev, V V

    2007-01-01

    Schwarzschild-type aplanatic telescopes with two aspheric mirrors, configured to correct spherical and coma aberrations, are considered for application in gamma-ray astronomy utilizing the ground-based atmospheric Cherenkov technique. We use analytical descriptions for the figures of primary and secondary mirrors and, by means of numerical ray-tracing, we find telescope configurations which minimize astigmatism and maximize effective light collecting area. It is shown that unlike the traditional prime-focus Davies-Cotton design, such telescopes provide a solution for wide field of view gamma-ray observations. The designs are isochronous, can be optimized to have no vignetting across the field, and allow for significant reduction of the plate scale, making them compatible with finely-pixilated cameras, which can be constructed from modern, cost-effective image sensors such as multi-anode PMTs, SiPMs, or image intensifiers.

  1. [Keratoconus].

    Science.gov (United States)

    Fournié, P; Touboul, D; Arné, J-L; Colin, J; Malecaze, F

    2013-09-01

    Keratoconus is a slowly progressive, non-inflammatory disorder of the eye characterized by thinning and protrusion of the cornea. Typically diagnosed in the patient's adolescent years, keratoconus may lead to substantial distortion of vision primarily from irregular astigmatism and myopia, and secondarily from corneal scarring. The classic histopathologic features include breaks in Bowman's layer and thinning of the corneal stroma. The etiology of keratoconus remains unclear. Form fruste keratoconus shows little progression, and has become known due to videotopographic analysis; it is very important to rule out in refractive surgery candidates. Treatment begins first and foremost with contact lenses, progressing to surgery as contact lens intolerance develops, with the goal of stabilization, including: cross-linking, intrastromal corneal ring segments and corneal transplantation. PMID:23911067

  2. [Riboflavin UVA cross-linking for keratoconus].

    Science.gov (United States)

    Maier, P; Reinhard, T

    2013-09-01

    Keratoconus is a progressive, ectatic disease of the cornea leading to thinning and highly irregular astigmatism. Until recently all treatment options, such as prescription of glasses or contact lenses were symptomatic and neither keratoplasty nor the implantation of intracorneal rings can heal the disease. Riboflavin ultraviolet A (UVA) collagen cross-linking (CXL) cannot heal keratoconus either but promises to halt the progression. The therapeutic principle is a photochemical reaction of riboflavin and UVA light leading to free oxygen radicals in the corneal stroma that induce covalent linking of the collagen fibrils. This stiffening effect should stop the progression. After the first reports at the end of the 1990s the treatment was widely used and many case series show that CXL can be effective in stopping disease progression in some patients. However, randomized, controlled multicenter trials showing high evidence of the treatment effectiveness are rare. This report includes a review of the literature regarding treatment effectiveness, indications and new developments. PMID:23760423

  3. [Iatrogenic Keratectasia: A Review].

    Science.gov (United States)

    Kohlhaas, M

    2015-06-01

    Iatrogenic corneal ectasia is a rare complication but also one of the most feared situations that can occur after uneventful corneal laser surgery. Ectatic changes can occur as early as 1 week or can be delayed up to several years after LASIK. The actual incidence of ectasia is undetermined, an incidence rate of 0.04 to almost 2.8 % has been reported. Ectasia is most common following LASIK; however, cases have been reported following PRK and other corneal refractive procedures. Keratectasia shows progressive myopia, irregular astigmatism, ghosting, fluctuating vision and problems with scotopic vision. The progression leads to severe loss of corrected visual acuity. Risk factors are thin corneas  8 D, young (female) age lenses. In severe cases a penetrating or a deep anterior lamellar graft is necessary. PMID:25853948

  4. Toric implantable collamer lens for keratoconus.

    Science.gov (United States)

    Kummelil, Mathew Kurian; Hemamalini, M S; Bhagali, Ridhima; Sargod, Koushik; Nagappa, Somshekar; Shetty, Rohit; Shetty, Bhujang K

    2013-08-01

    Keratoconus is a progressive non-inflammatory thinning of the cornea that induces myopia and irregular astigmatism and decreases the quality of vision due to monocular diplopia, halos, or ghost images. Keratoconus patients unfit for corneal procedures and intolerant to refractive correction by spectacles or contact lenses have been implanted toric posterior chamber phakic intraocular lenses (PC pIOLs) alone or combined with other surgical procedures to correct the refractive errors associated with keratoconus as an off label procedure with special informed consent from the patients. Several reports attest to the safety and efficacy of the procedure, though the associated corneal higher order aberrations would have an impact on the final visual quality. PMID:23925337

  5. Keratoconus: current perspectives.

    Science.gov (United States)

    Vazirani, Jayesh; Basu, Sayan

    2013-01-01

    Keratoconus is characterized by progressive corneal protrusion and thinning, leading to irregular astigmatism and impairment in visual function. The etiology and pathogenesis of the condition are not fully understood. However, significant strides have been made in early clinical detection of the disease, as well as towards providing optimal optical and surgical correction for improving the quality of vision in affected patients. The past two decades, in particular, have seen exciting new developments promising to alter the natural history of keratoconus in a favorable way for the first time. This comprehensive review focuses on analyzing the role of advanced imaging techniques in the diagnosis and treatment of keratoconus and evaluating the evidence supporting or refuting the efficacy of therapeutic advances for keratoconus, such as newer contact lens designs, collagen crosslinking, deep anterior lamellar keratoplasty, intracorneal ring segments, photorefractive keratectomy, and phakic intraocular lenses. PMID:24143069

  6. Main factors influencing postoperative visual function after refractive cataract surgery%屈光性白内障手术术后影响视觉质量的主要因素

    Institute of Scientific and Technical Information of China (English)

    龚敏; 刘谊

    2014-01-01

    人工晶状体( intraocular lens ,IOL)屈光力计算误差,角膜散光,前房深度以及IOL的位置等因素能导致术眼屈光状态的改变,影响白内障术后的整体视觉质量。我们将对手术过程顺利的屈光性白内障手术术后影响视觉质量的主要因素进行综述。%Factors including intraocular lens power calculation error, corneal astigmatism, anterior chamber depth and lens position can lead to the change of refractive status, they also influence the overall postoperative visual quality.This article provides a comprehensive review of the main factors affecting postoperative visual function after uneventful refractive cataract surgery.

  7. Wavefront aberration function in terms of R. V. Shack's vector product and Zernike polynomial vectors.

    Science.gov (United States)

    Gray, Robert W; Rolland, Jannick P

    2015-10-01

    Previous papers have shown how, for rotationally symmetric optical imaging systems, nodes in the field dependence of the wavefront aberration function develop when a rotationally symmetric optical surface within an imaging optical system is decentered and/or tilted. In this paper, we show how Shack's vector product (SVP) can be used to express the wavefront aberration function and to define vectors in terms of the Zernike polynomials. The wavefront aberration function is then expressed in terms of the Zernike vectors. It is further shown that SVP fits within the framework of two-dimensional geometric algebra (GA). Within the GA framework, an equation for the third-order node locations for the binodal astigmatism term that emerge in the presence of tilts and decenters is then demonstrated. A computer model of a three-mirror telescope system is used to demonstrate the validity of the mathematical development. PMID:26479937

  8. Optical tweezers absolute calibration

    CERN Document Server

    Dutra, R S; Neto, P A Maia; Nussenzveig, H M

    2014-01-01

    Optical tweezers are highly versatile laser traps for neutral microparticles, with fundamental applications in physics and in single molecule cell biology. Force measurements are performed by converting the stiffness response to displacement of trapped transparent microspheres, employed as force transducers. Usually, calibration is indirect, by comparison with fluid drag forces. This can lead to discrepancies by sizable factors. Progress achieved in a program aiming at absolute calibration, conducted over the past fifteen years, is briefly reviewed. Here we overcome its last major obstacle, a theoretical overestimation of the peak stiffness, within the most employed range for applications, and we perform experimental validation. The discrepancy is traced to the effect of primary aberrations of the optical system, which are now included in the theory. All required experimental parameters are readily accessible. Astigmatism, the dominant effect, is measured by analyzing reflected images of the focused laser spo...

  9. The Genetic and Environmental Factors for Keratoconus

    Directory of Open Access Journals (Sweden)

    Ariela Gordon-Shaag

    2015-01-01

    Full Text Available Keratoconus (KC is the most common cornea ectatic disorder. It is characterized by a cone-shaped thin cornea leading to myopia, irregular astigmatism, and vision impairment. It affects all ethnic groups and both genders. Both environmental and genetic factors may contribute to its pathogenesis. This review is to summarize the current research development in KC epidemiology and genetic etiology. Environmental factors include but are not limited to eye rubbing, atopy, sun exposure, and geography. Genetic discoveries have been reviewed with evidence from family-based linkage analysis and fine mapping in linkage region, genome-wide association studies, and candidate genes analyses. A number of genes have been discovered at a relatively rapid pace. The detailed molecular mechanism underlying KC pathogenesis will significantly advance our understanding of KC and promote the development of potential therapies.

  10. Endothelial keratoplasty: evolution and horizons

    Directory of Open Access Journals (Sweden)

    Gustavo Teixeira Grottone

    2012-12-01

    Full Text Available Endothelial keratoplasty has been adopted by corneal surgeons worldwide as an alternative to penetrating keratoplasty (PK in the treatment of corneal endothelial disorders. Since the first surgeries in 1998, different surgical techniques have been used to replace the diseased endothelium. Compared with penetrating keratoplasty, all these techniques may provide faster and better visual rehabilitation with minimal change in refractive power of the transplanted cornea, minimal induced astigmatism, elimination of suture-induced complications and late wound dehiscence, and a reduced demand for postoperative care. Translational research involving cell-based therapy is the next step in work on endothelial keratoplasty. The present review updates information on comparisons among different techniques and predicts the direction of future treatment.

  11. Collagen cross-linking in the treatment of pellucid marginal degeneration

    Directory of Open Access Journals (Sweden)

    Ziad Hassan

    2014-01-01

    Full Text Available Pellucid marginal degeneration (PMD is an uncommon cause of inferior peripheral corneal thinning disorder, characterized by irregular astigmatism. We analyzed a case of bilateral PMD patient and treated one eye with corneal collagen cross-linking (CXL therapy. Corneal topography was characteristic for PMD. Visual acuity, slitlamp examinations, tonometry, and corneal thickness were observed. Simulated keratometric and topographic index values were detected with corneal topography. Uncorrected, LogMAR visual acuity has improved from +0.8 to +0.55 during the 6 months and +0.3 during the 8 months follow-up after CXL. Pachymetry values and intraocular pressure showed no changes. Keratometric values and topografic indexes disclosed no progression of the disease. CXL may postpone or eliminate the need of corneal transplantation in cases with PMD.

  12. Effects of Different Zernike Terms on Optical Quality and Vision of Human Eyes

    Institute of Scientific and Technical Information of China (English)

    ZHAO Hao-Xin; XU Bing; LI Jing; DAI Yun; YU Xiang; ZHANG Yu-Dong; JIANG Wen-Han

    2009-01-01

    The visual quality of human eyes is much restricted by high-order aberrations as well as low-order aberrations (defocus and astigmatism), but each term of high-order aberrations contributes differently. The visual acuity and contrast of the image on the retina can be gained by inducing aberrations to each term of high orders. Based on an adaptive optics system, the visual acuity of four subjects is tested by inducing aberrations to each Zernike term after correcting all the aberrations of the subjects. Zernike terms near the center of the Zernike tree affect visual quality more than those near the edge both theoretically and experimentally, and 0.1-μm aberration of these terms can clearly degrade the optical quality and vision. The results suggest that correcting the terms near the center of Zernike tree can improve the visual quality effectively in practice.

  13. Infantile nystagmus and visual deprivation

    DEFF Research Database (Denmark)

    Fledelius, Hans C; Jensen, Hanne

    2014-01-01

    PURPOSE: To evaluate whether effects of early foveal motor instability due to infantile nystagmus might compare to those of experimental visual deprivation on refraction in a childhood series. METHODS: This was a retrospective analysis of data from the Danish Register for Blind and Weaksighted...... Children with infantile nystagmus recorded as prime diagnosis. We perused 90 records of children now aged 10-17 years, some of whom eventually exceeded the register borderline of 0.3 as best-corrected visual acuity. Spherical equivalent refraction was the primary outcome parameter, but visual acuity......, astigmatism, and age were further considered. The series comprised 48 children with nystagmus as single diagnosis, whereas 42 had clinical colabels (Down syndrome [13], dysmaturity [9], and mental retardation, encephalopathy [20]). RESULTS: Median binocular visual acuity was 0.3 in the full series, and median...

  14. 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.

  15. Visual acuity and refraction by age for children of three different ethnic groups in Paraguay

    Directory of Open Access Journals (Sweden)

    Marissa Janine Carter

    2013-04-01

    Full Text Available PURPOSE: To characterize refractive errors in Paraguayan children aged 5-16 years and investigate effect of age, gender, and ethnicity. METHODS:The study was conducted at 3 schools that catered to Mennonite, indigenous, and mixed race children. Children were examined for presenting visual acuity, autorefraction with and without cycloplegia, and retinoscopy. Data were analyzed for myopia and hyperopia (SE ≤-1 D or -0.5 D and ≥2 D or ≥3 D and astigmatism (cylinder ≥1 D. Spherical equivalent (SE values were calculated from right eye cycloplegic autorefraction data and analyzed using general linear modelling. RESULTS: There were 190, 118, and 168 children of Mennonite, indigenous and mixed race ethnicity, respectively. SE values between right/left eyes were nonsignificant. Mean visual acuity (VA without correction was better for Mennonites compared to indigenous or mixed race children (right eyes: 0.031, 0.090, and 0.102 logMAR units, respectively; P<0.000001. There were 2 cases of myopia in the Mennonite group (1.2% and 2 cases in the mixed race group (1.4% (SE ≤-0.5 D. The prevalence of hyperopia (SE ≥2 D was 40.6%, 34.2%, and 46.3% for Mennonite, indigenous and mixed race children. Corresponding astigmatism rates were 3.2%, 9.5%, and 12.7%. Females were slightly more hyperopic than males, and the 9-11 years age group was the most hyperopic. Mennonite and mixed race children were more hyperopic than indigenous children. CONCLUSIONS: Paraguayan children were remarkably hyperopic and relatively free of myopia. Differences with regard to gender, age, and ethnicity were small.

  16. Prevalence of refractive errors in Villa Maria, Córdoba, Argentina

    Institute of Scientific and Technical Information of China (English)

    Victoria M Snchez; Claudio P Juarez; Rafael Iribarren; Santiago G Latino; Victor E Torres; Ana L Gramajo; Mara N Artal; Mara B Yadarola; Patricia R Garay; Jos D Luna

    2016-01-01

    Background: Refractive errors are among the most frequent reasons for demand of eye-care services. Publications on refractive errors prevalence in our country are few. This study has the purpose to assess the prevalence of refractive errors in an adult population of Villa Maria, Córdoba, Argentina. Methods: The Villa Maria Eye Study is a population-based cross-sectional study conducted in the city of Villa Maria, Córdoba, Argentina from May 2008 to November 2009. Subject’s aged 40+ received a demographic interview and complete ophthalmological exam. Visual acuity was obtained with an ETDRS chart. Cycloplegic auto refraction was performed. The spherical equivalent was highly correlated between right and left eyes, so only data of right eyes are presented. Myopia and hyperopia were defined with a ±0.50 diopters (D) criterion and astigmatism >1 D. Results: This study included 646 subjects, aged 40 to 90 (mean age: 59.6±10.3 years old). Four hundred and sixty two (71.5%) were females. The mean spherical equivalent was +0.714±2.41 D (range, −22.00 to+8.25 D) and the power of the cylinder was, on average, −0.869±0.91 D (range, 0 to −6.50 D). In this sample, 61.6% subjects were hyperopic, and 13.5% were myopic. Myopia prevalence was lower in men (9.8% versus 14.9%) but this difference among genders was not statistically signiifcant. There were 141 subjects (21.8%) with anisometropia greater than 1 D, and 168 subjects (26.0%) with astigmatism greater than 1 D. Conclusions: The present study shows the prevalence of cycloplegic refractive errors in an adult population of Argentina. The prevalence of hyperopia was high, while myopia prevalence was very low.

  17. Visual and refractive outcome of one-site phacotrabeculectomy compared with temporal approach phacoemulsification

    Directory of Open Access Journals (Sweden)

    Daniela Vaideanu

    2008-10-01

    Full Text Available Daniela Vaideanu, Kaveri Mandal, Anthony Hildreth, Scott G Fraser, Peter S PhelanGlaucoma Unit, Sunderland Eye Infirmary, Sunderland, UKBackground: We aimed to compare visual and refractive outcome following phacoemulsification and intraocular lens implant (IOL and combined one-site phacotrabeculectomy.Method: We performed a retrospective study of case records of patients who had temporal incision phacoemulsification with IOL or one-site phacotrabeculectomy, between June 1997 and June 2001. The patients were matched for age group, operating list and IOL type. All patients were operated on under local anesthesia by the same surgeon. Each arm of the study had 90 patients, age range 60 to 75 years. We collected pre- and postoperative visual acuity, pre- and postoperative refraction within six months after surgery, and intended refraction. The intraocular pressure control was not recorded, as it was not the aim of our study.Results: In the phacotrabeculectomy group, 76.6% of patients achieved aimed spherical equivalent, 15.5% of patients had against-the-rule (ATR astigmatism induced by the surgery, and 90% of the patients had best corrected visual acuity (BCVA more than 6/12. In the temporal incision phacoemulsification group, 81.1% of patients achieved aimed spherical equivalent, 10% of the patients had induced ATR by the surgery and 95.55% of patients achieved BCVA more than 6/12.Conclusion: In this study the visual outcome of the phacotrabeculectomy group did not differ significantly from the visual outcome of temporal approach phacoemulsification.Keywords: refractive outcome, phacoemulsifi cation, phacotrabeculectomy, astigmatism

  18. Outcome of Corneal Collagen Crosslinking for Progressive Keratoconus in Paediatric Patients

    Directory of Open Access Journals (Sweden)

    Deepa Viswanathan

    2014-01-01

    Full Text Available Purpose. To evaluate the efficacy of corneal collagen crosslinking for progressive keratoconus in paediatric patients. Methods. This prospective study included 25 eyes of 18 patients (aged 18 years or younger who underwent collagen crosslinking performed using riboflavin and ultraviolet-A irradiation (370 nm, 3 mW/cm2, 30 min. Results. The mean patient age was 14.3 ± 2.4 years (range 8–17 and mean followup duration was 20.1 ± 14.25 months (range 6–48. Crosslinked eyes demonstrated a significant reduction of keratometry values. The mean baseline simulated keratometry values were 46.34 dioptres (D in the flattest meridian and 50.06 D in the steepest meridian. At 20 months after crosslinking, the values were 45.67 D (P=0.03 and 49.34 D (P=0.005, respectively. The best spectacle corrected visual acuity (BSCVA and topometric astigmatism improved after crosslinking. Mean logarithm of the minimum angle of resolution (logMAR BSCVA decreased from 0.24 to 0.21 (P=0.89 and topometric astigmatism reduced from mean 3.50 D to 3.25 D (P=0.51. Conclusions. Collagen crosslinking using riboflavin and ultraviolet-A is an effective treatment option for progressive keratoconus in paediatric patients. Crosslinking stabilises the condition and, thus, reduces the need for corneal grafting in these young patients.

  19. Refractive Errors in Northern China Between the Residents with Drinking Water Containing Excessive Fluorine and Normal Drinking Water.

    Science.gov (United States)

    Bin, Ge; Liu, Haifeng; Zhao, Chunyuan; Zhou, Guangkai; Ding, Xuchen; Zhang, Na; Xu, Yongfang; Qi, Yanhua

    2016-10-01

    The purpose of this study was to evaluate the refractive errors and the demographic associations between drinking water with excessive fluoride and normal drinking water among residents in Northern China. Of the 1843 residents, 1415 (aged ≥40 years) were divided into drinking-water-excessive fluoride (DWEF) group (>1.20 mg/L) and control group (≤1.20 mg/L) on the basis of the fluoride concentrations in drinking water. Of the 221 subjects in the DWEF group, with 1.47 ± 0.25 mg/L (fluoride concentrations in drinking water), the prevalence rates of myopia, hyperopia, and astigmatism were 38.5 % (95 % confidence interval [CI] = 32.1-45.3), 19.9 % (95 % CI = 15-26), and 41.6 % (95 % CI = 35.1-48.4), respectively. Of the 1194 subjects in the control group with 0.20 ± 0.18 mg/L, the prevalence of myopia, hyperopia, and astigmatism were 31.5 % (95 % CI = 28.9-34.2), 27.6 % (95 % CI = 25.1-30.3), and 45.6 % (95 % CI = 42.8-48.5), respectively. A statistically significant difference was not observed in the association of spherical equivalent and fluoride concentrations in drinking water (P = 0.84 > 0.05). This report provides the data of the refractive state of the residents consuming drinking water with excess amounts of fluoride in northern China. The refractive errors did not result from ingestion of mild excess amounts of fluoride in the drinking water.

  20. Aladin transmit-receive optics (TRO): the optical interface between laser, telescope and spectrometers

    Science.gov (United States)

    Mosebach, Herbert; Erhard, Markus; Camus, Fabrice

    2005-09-01

    This paper presents the design and key technologies of the Transmit-Receive Optics (TRO) for the Aladin lidar instrument. The TRO as the central optical interface on the Aladin instrument leading the optical signals from the laser source to the emitting/receiving telescope, and vice versa, the received back scattered signals from the telescope to the spectrometers for Doppler shift evaluation. Additionally, the TRO contains a calibration branch bypassing the telescope and aims at levelling out the received signals in terms of wavelength and signal height changes due to wavelength and intensity variations of the laser. The opto-mechanical concept of the TRO consists of afocal optical groups, which are connected by parallel beams. Extreme requirements have been defined for the TRO on the end-to-end transmission (>=73 %) with an associated effective bandwidth of less than 1 nm over the 200 - 1100 nm spectral range. The achieved solution is presented in this paper. A further feature of the TRO is the use of two so-called aberration generators on the emitting and calibration branch, with which an artificial astigmatism can be realised for eye safety reasons. Its effect on astigmatism is presented. This article also addresses the effort on stray light suppression, which is of extreme importance for the TRO. Special ion plated (IP) optical coatings have been used with superior performance for the TRO, particulary on laser energy resistance and air/vacuum stability. The development of special mounting technologies of optical elements to meet the stringent WFE, stability, and stray light requirements for the TRO are described. Key words : Aeolus Satellite, ALADIN instrument, Lidar, optical design, UV optics manufacturing technologies

  1. Measuring higher order optical aberrations of the human eye: techniques and applications

    Directory of Open Access Journals (Sweden)

    L. Alberto V. Carvalho

    2002-11-01

    Full Text Available In the present paper we discuss the development of "wave-front", an instrument for determining the lower and higher optical aberrations of the human eye. We also discuss the advantages that such instrumentation and techniques might bring to the ophthalmology professional of the 21st century. By shining a small light spot on the retina of subjects and observing the light that is reflected back from within the eye, we are able to quantitatively determine the amount of lower order aberrations (astigmatism, myopia, hyperopia and higher order aberrations (coma, spherical aberration, etc.. We have measured artificial eyes with calibrated ametropia ranging from +5 to -5 D, with and without 2 D astigmatism with axis at 45º and 90º. We used a device known as the Hartmann-Shack (HS sensor, originally developed for measuring the optical aberrations of optical instruments and general refracting surfaces in astronomical telescopes. The HS sensor sends information to a computer software for decomposition of wave-front aberrations into a set of Zernike polynomials. These polynomials have special mathematical properties and are more suitable in this case than the traditional Seidel polynomials. We have demonstrated that this technique is more precise than conventional autorefraction, with a root mean square error (RMSE of less than 0.1 µm for a 4-mm diameter pupil. In terms of dioptric power this represents an RMSE error of less than 0.04 D and 5º for the axis. This precision is sufficient for customized corneal ablations, among other applications.

  2. Anterior iris-claw lens implantation with single paracentesis

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    Ahmet Özer

    2011-11-01

    Full Text Available In this study, the technique and results of iris-claw intraocular lens (IOL implantation with corneal incision and single paracentesis were presented. Eighteen eyes of 18 patients who underwent iris-claw implantation surgery with a single paracentesis were included in this prospective study. Iris-claw lens was grasped by its forceps and placed into the anterior chamber through superior corneal opening. While IOL was held by forceps, a blunt enclavation spatula was introduced through inferior paracentesis. Then the spatula was directed toward underneath of iris through pupil and toward sides where iris was entrapped into the claw by gentle push of iris through the slotted center of the lens haptics. Mean age of patients was 54.28±25.21 years (7-76 years. Mean anterior chamber depth was 4.07±0.32 mm and mean keratometric power was 43.01±2.73 D. Preoperative BCVA was 20/63 or better in 8 (44.4% patients. At the first postoperative month BCVA was 20/63 or better in 14 (77.8% patients. Preoperative mean spherical refraction was +11.05±2.62 D, preoperative astigmatism was 2.15±0.85. Postoperative mean spherical refraction was - 0.58±0.25 D and mean astigmatism was - 1.92±0.67 D. The most frequent postoperative complication was mild corneal edema seen in three patients that resolved completely during the first week with medical treatment. Irisclaw IOL implantation can be performed easily with corneal incision and single paracentesis. Single paracentesis does not increase surgical time or cause inconvenience during the procedure.

  3. Efficacy and safety of iris-supported phakic lenses (Verisyse for treating moderately high myopia

    Directory of Open Access Journals (Sweden)

    Melisa Ahmedbegović Pjano

    2016-02-01

    Full Text Available Aim To evaluate efficacy and safety of iris-supported phakic lenses (Verisyse for treating moderately high myopia. Methods This prospective clinical study included 40 eyes from 29 patients, who underwent implantation of Verisyse for correction of myopia from -6.00 to -14.50 diopters (D in the Eye Clinic ‘’Svjetlost’’, Sarajevo, from January 2011 to January 2014. Uncorrected distance visual acuity (UDVA, manifest residual spherical equivalent (MRSE, postoperative astigmatism, intraocular pressure (IOP, endothelial cell (EC density were evaluated at one, three, six and twelve months. Corrected visual acuity (CDVA, index of safety and efficacy were evaluated after 12 months. Results Out of 29 patients 15 were males and 14 females, with mean age of 27.9 ± 5.0. After 12 months 77.5% eyes had UDVA ≥ 0.5 and 32.5% had UDVA ≥ 0.8. Mean MRSE was 0.55D ± 0.57D and mean postoperative astigmatism -0.86D ± 0.47D. Efficacy index was 1.09 ± 0.19 and safety index 1.18 ± 0.21. One eye (2.5% lost two Snellen lines and three eyes (7.5% one line, 11 eyes (27.5% gained one line, and five eyes (15.5% gained two lines. EC loss after 12 months was 7.59 ± 3.05%. There was no significant change of IOP after one year follow up. Conclusion Implantation of iris-supported phakic lenses (Verisyse for treating moderately high myopia is an efficient and safe procedure.

  4. Nano-Structuring of Solid Surface by EUV Ar8+ Laser

    International Nuclear Information System (INIS)

    Requirement of increased resolution is at present most loudly pronounced in microelectronics, which, following Moore´s law (doubling every two years the transistorcount that can be placed inexpensively on integrated circuit), commands a continuous upgrade of micro-/nano-lithography. Such upgrade indirectly influences processing speed, memory capacity, number and size of pixels in sensors, etc. The submitted paper demonstrates our first attempt for “direct (i.e. ablation) patterning” of PMMA by pulse, high-current, capillary-discharge-pumped Ar8+ ion laser (λ = 46,9 nm). For focusing a long-focal spherical mirror (R = 2100 mm) covered by 14 double-layer Sc-Si coating was used. The ablated focal spots demonstrate not only that the energy of our laser is sufficient for such experiments, but also that the design of focusing optics must be more sophisticated: severe aberrations have been revealed – an irregular spot shape and strong astigmatism with astigmatic difference as large as 16 mm. Moreover, on the bottom of ablated spots a laserinduced periodic surface structure (LIPSS) has appeared. Finally, a direct patterning of quadratic hole 7,5x7,5 µm, standing in contact with PMMA substrate, has shown a strongly developed 2D diffraction pattern (period in the centre ∼125 nm). In conclusion there will be shown the design of a new (grazing incidence) focusing optics, and a new “nano-patterning” tool – grazing incidence interferometer, which enable to ablate a regular, in advance defined pattern. It is believed that this is the first step to application of this technique not only to nanolithography,but also e.g. to study of electron dynamics in superlattices. (author)

  5. Comparison of Keratometric Values Using Javal Keratometer, Oculus Pentacam, and Orbscan II

    Directory of Open Access Journals (Sweden)

    Hassan Hashemi

    2014-05-01

    Full Text Available Purpose: To compare Orbscan II and Pentacam keratometry readings in terms of their agreement with a manual Javal type keratometer Methods: In this retrospective study, records of patients who had refractive surgery were reviewed. We extracted data of 765 eyes which had keratometry with the Javal keratometer; of these, 577 had Orbscan II and 200 eyes had Pentacam acquisitions. Minimum (min-K and maximum (max-K keratometry readings and keratometric astigmatism with the latter two devices were compared with Javal. Results: Correlation coefficients for Javal and Orbscan II in measuring min-K and max-K were r=0.916 and r=0.913, respectively (p<0.001. The 95% limits of agreement (LoA between Javal and Orbscan II was 1.17-1.20 D for min-K and 1.22-1.24 D for max-K. The coefficients for Pentacam and Javal min-K and max-K readings were very high (r=0.943 and r=0.962. The 95% LoA between Pentacam and Javal in measuring min-K and max-K were 0.51-0.99D and 0.72-0.99D, respectively. The correlation between Pentacam and Javal measurements of keratometric astigmatism was stronger than that for Orbscan II and Javal (r=0.973 and r=0.800; the 95% LoA was 0.55-0.76D for Pentacam and Javal, and 1.14-1.19D for Orbscan II and Javal. Conclusion: According to this research, Orbscan II and Pentacam had high correlation and agreement with Javal-keratometer in determining keratometric values. Nevertheless, the results obtained from Pentacam showed better agreement and stronger correlation with Javal as compared with Orbscan II. It seems that Pentacam is a suitable substitute for Javal to perform keratometry in normal eyes.

  6. The Evaluation of the Effects of Differently-Designed Toric Soft Contact Lenses on Visual Quality

    Directory of Open Access Journals (Sweden)

    Sevda Aydın Kurna

    2013-08-01

    Full Text Available Purpose: The purpose of this study was to evaluate the effects of aspheric Balafilcon A and spherical Senofilcon A toric soft contact lenses, which have two different stabilization systems, on visual quality. Material and Method: Forty eyes of 20 patients who were followed up in our contact lens section were included in this study. Refractive errors of the patients were between -0.50 and -6.0 diopters of myopia and >0.75 diopter of astigmatism. The patients were randomly assigned to wear Balafilcon A (Purevision Toric, Baush&Lomb with prism balast toric system or spherical designed Senofilcon A (Acuvue Oasys for astigmatism, Johnson&Johnson with accelerated stabilization toric system. We recorded and compared the visual acuity with Snellen chart, contrast sensitivity with Bailey-Lovie chart in letters, mean root mean square (RMS of corneal aberration with by Nidek Magellan Mapper for all eyes with and without glasses and while wearing Balafilcon A or Senofilcon A toric soft contact lenses. Results: We did not observe any difference in visual acuity between contact lenses. Contrast sensitivity was increased approximately 4.8-5.4 letters with contact lenses. Total higher order aberrations of mean RMS values were 0.42±0.14 µm without contact lens, 0.37±0.23 µm with Balafilcon A lens, 0.43±0.15 µm with Senofilcon A (p=0.507. Trefoil values were significantly higher with Senofilcon A lenses when compared to Balafilcon A lenses. There was no statistically significant difference for other measured higher order aberrations. Discussion: High and low contrast vision values were adequate in both contact lens groups. There was a non-significant decrease in total higher order aberration values with aspheric design contact lenses when compared to spherical designs. Although there were differences in aberrations related to lens designs, they did not have significant effect on visual quality. (Turk J Ophthalmol 2013; 43: 253-7

  7. Results of endocapsular phacofracture debulking of hard cataracts

    Directory of Open Access Journals (Sweden)

    Davison JA

    2015-07-01

    Full Text Available James A Davison Wolfe Eye Clinic, Marshalltown, IA, USA Purpose/aim of the study: To present a phacoemulsification technique for hard cataracts and compare postoperative results using two different ultrasonic tip motions during quadrant removal.Materials and methods: A phacoemulsification technique which employs in situ fracture and endocapsular debulking for hard cataracts is presented. The prospective study included 56 consecutive cases of hard cataract (LOCS III NC [Lens Opacification Classification System III, nuclear color], average 4.26, which were operated using the Infiniti machine and the Partial Kelman tip. Longitudinal tip movement was used for sculpting for all cases which were randomized to receive longitudinal or torsional/interjected longitudinal (Intelligent Phaco [IP] strategies for quadrant removal. Measurements included cumulative dissipated energy (CDE, 3 months postoperative surgically induced astigmatism (SIA, and corneal endothelial cell density (ECD losses.Results: No complications were recorded in any of the cases. Respective overall and longitudinal vs IP means were as follows: CDE, 51.6±15.6 and 55.7±15.5 vs 48.6±15.1; SIA, 0.36±0.2 D and 0.4±0.2 D vs 0.3±0.2 D; and mean ECD loss, 4.1%±10.8% and 5.9%±13.4% vs 2.7%±7.8%. The differences between longitudinal and IP were not significant for any of the three categories.Conclusion: The endocapsular phacofracture debulking technique is safe and effective for phacoemulsification of hard cataracts using longitudinal or torsional IP strategies for quadrant removal with the Infiniti machine and Partial Kelman tip. Keywords: astigmatism, cataract, corneal endothelium, phacoemulsification, viscoelastic

  8. Prevalence and profile of ophthalmic disorders in oculocutaneous albinism: a field report from South-Eastern Nigeria.

    Science.gov (United States)

    Udeh, N N; Eze, B I; Onwubiko, S N; Arinze, O C; Onwasigwe, E N; Umeh, R E

    2014-12-01

    To assess the burden and spectrum of refractive and non-refractive ophthalmic disorders in south-eastern Nigerians with oculocutaneous albinism. In a population-based survey in Enugu state, between August, 2011 and January, 2012, albinos were identified using the database of the Enugu state's Albino Foundation, and mass media-based mobilisation. The participants were enrolled at the Eye Clinics of the University of Nigeria Teaching Hospital and Enugu State University of Science and Technology Teaching Hospital using a defined protocol. Relevant socio-demographic and clinical data were obtained from each participant. Descriptive and comparative statistics were performed. Statistical significance was indicated by p < 0.05. The participants (n = 153; males, 70) were aged 23.5 + 10.4 SD years (range 6-60 years). Both refractive and non-refractive disorders were present in all participants. Non-refractive disorders comprised nystagmus, foveal hypoplasia, hypopigmented fundi and prominent choroidal vessels in 100.0% participants; and strabismus in 16.3% participants. Refractive disorders comprised astigmatism -73.2% eyes, myopia -23.9% and hypermetropia 2.9%. Spherical refractive errors ranged from -14.00 DS to +8.00 DS while astigmatic errors ranged from -6.00 DC to +6 DC. Mixed refractive and non-refractive disorder i.e. presenting visual impairment was present in 100.0% participants. Overall, refractive error was associated with non-possession of tertiary education (OR 0.61; 95% CI 0.38-0.96; p = 0.0374). There is high prevalence of refractive, non-refractive and mixed ophthalmic disorders among albinos in south-eastern Nigeria. This underscores the need for tailored provision of resources to address their eye care needs, and creation of needs awareness amongst them.

  9. Common complications of deep lamellar keratoplasty in the early phase of the learning curve

    Directory of Open Access Journals (Sweden)

    Hosny M

    2011-06-01

    Full Text Available Mohamed HosnyOphthalmology Department, Faculty of Medicine, Cairo University, Cairo, EgyptPurpose: To evaluate and record the common complications that face surgeons when they perform their first few series of deep lamellar keratoplasty and measures to avoid these.Setting: Dar El Oyoun Hospital, Cairo, Egypt.Methods: Retrospective study of the first 40 eyes of 40 patients carried out by two corneal surgeons working in the same center. All patients were planned to undergo a deep anterior lamellar keratoplasty using the big bubble technique. Twelve patients suffered from keratoconus while 28 patients had anterior corneal pathologies. Recorded complications were classified as either intraoperative or postoperative.Results: Perforation of Descemet's membrane was the most common intraoperative complication. It occurred in nine eyes (22.5%: five eyes (12.5% had microperforations while four eyes (10% had macroperforations, three eyes (7.5% had central perforations, and six eyes (15% had peripheral perforations. Other complications included incomplete separation of Descemet's membrane and remnants of peripheral stromal tissue. Postoperative complications included double anterior chamber which occurred in four eyes (10% and Descemet's membrane corrugations. Postoperative astigmatism ranged from 1.25 to 4.5 diopters with a mean of 2.86 diopters in the whole series, but in the six cases with identified residual stroma in the periphery of the host bed, the astigmatism ranged from 2.75 to 4.5 diopters with a mean of 3.62 diopters.Conclusion: Deep lamellar keratoplasty is sensitive to procedural details. Learning the common complications and how to avoid them helps novice surgeons to learn the procedure faster.Keywords: deep lamellar keratoplasty, complications, big bubble technique

  10. simEye: Computer-based simulation of visual perception under various eye defects using Zernike polynomials.

    Science.gov (United States)

    Fink, Wolfgang; Micol, Daniel

    2006-01-01

    We describe a computer eye model that allows for aspheric surfaces and a three-dimensional computer-based ray-tracing technique to simulate optical properties of the human eye and visual perception under various eye defects. Eye surfaces, such as the cornea, eye lens, and retina, are modeled or approximated by a set of Zernike polynomials that are fitted to input data for the respective surfaces. A ray-tracing procedure propagates light rays using Snell's law of refraction from an input object (e.g., digital image) through the eye under investigation (i.e., eye with defects to be modeled) to form a retinal image that is upside down and left-right inverted. To obtain a first-order realistic visual perception without having to model or simulate the retina and the visual cortex, this retinal image is then back-propagated through an emmetropic eye (e.g., Gullstrand exact schematic eye model with no additional eye defects) to an output screen of the same dimensions and at the same distance from the eye as the input object. Visual perception under instances of emmetropia, regular astigmatism, irregular astigmatism, and (central symmetric) keratoconus is simulated and depicted. In addition to still images, the computer ray-tracing tool presented here (simEye) permits the production of animated movies. These developments may have scientific and educational value. This tool may facilitate the education and training of both the public, for example, patients before undergoing eye surgery, and those in the medical field, such as students and professionals. Moreover, simEye may be used as a scientific research tool to investigate optical lens systems in general and the visual perception under a variety of eye conditions and surgical procedures such as cataract surgery and laser assisted in situ keratomileusis (LASIK) in particular. PMID:17092160

  11. Clinical Outcomes after Uncomplicated Cataract Surgery with Implantation of the Tecnis Toric Intraocular Lens

    Science.gov (United States)

    Lubiński, Wojciech; Kaźmierczak, Beata; Gronkowska-Serafin, Jolanta; Podborączyńska-Jodko, Karolina

    2016-01-01

    Purpose. To evaluate the clinical outcomes after uncomplicated cataract surgery with implantation of an aspheric toric intraocular lens (IOL) during a 6-month follow-up. Methods. Prospective study including 27 consecutive eyes of 18 patients (mean age: 66.1 ± 11.4 years) with a visually significant cataract and corneal astigmatism ≥ 0.75 D and undergoing uncomplicated cataract surgery with implantation of the Tecnis ZCT toric IOL (Abbott Medical Optics). Visual, refractive, and keratometric outcomes as well as IOL rotation were evaluated during a 6-month follow-up. At the end of the follow-up, patient satisfaction and perception of optical/visual disturbances were also evaluated using a subjective questionnaire. Results. At 6 months after surgery, mean LogMAR uncorrected (UDVA) and corrected distance visual acuity (CDVA) were 0.19 ± 0.12 and 0.14 ± 0.10, respectively. Postoperative UDVA of 20/40 or better was achieved in 92.6% of eyes. Mean refractive cylinder decreased significantly from −3.73 ± 1.96 to −1.42 ± 0.88 D (p < 0.001), while keratometric cylinder did not change significantly (p = 0.44). Mean absolute IOL rotation was 1.1 ± 2.4°, with values of more than 5° in only 2 eyes (6.9%). Mean patient satisfaction score was 9.70 ± 0.46, using a scale from 0 (not at all satisfied) to 10 (very satisfied). No postoperative optical/visual disturbances were reported. Conclusion. Cataract surgery with implantation of the Tecnis toric IOL is an effective method of refractive correction in eyes with corneal astigmatism due to the good IOL positional stability, providing high levels of patient's satisfaction. PMID:27022478

  12. Retreatments after multifocal intraocular lens implantation: an analysis

    Science.gov (United States)

    Gundersen, Kjell Gunnar; Makari, Sarah; Ostenstad, Steffen; Potvin, Rick

    2016-01-01

    Purpose To determine the incidence and etiology of required retreatment after multifocal intraocular lens (IOL) implantation and to evaluate the methods and clinical outcomes of retreatment. Patients and methods A retrospective chart review of 416 eyes of 209 patients from one site that underwent uncomplicated cataract surgery with multifocal IOL implantation. Biometry, the IOL, and refractive data were recorded after the original implantation, with the same data recorded after retreatment. Comments related to vision were obtained both before and after retreatment for retreated patients. Results The multifocal retreatment rate was 10.8% (45/416 eyes). The eyes that required retreatment had significantly higher residual refractive astigmatism compared with those who did not require retreatment (1.21±0.51 D vs 0.51±0.39 D, P<0.01). The retreatment rate for the two most commonly implanted primary IOLs, blended bifocal (10.5%, 16/152) and bilateral trifocal (6.9%, 14/202) IOLs, was not statistically significantly different (P=0.12). In those requiring retreatment, refractive-related complaints were most common. Retreatment with refractive corneal surgery, in 11% of the eyes, and piggyback IOLs, in 89% of the eyes, was similarly successful, improving patient complaints 78% of the time. Conclusion Complaints related to ametropia were the main reasons for retreatment. Residual astigmatism appears to be an important determinant of retreatment rate after multifocal IOL implantation. Retreatment can improve symptoms for a high percentage of patients; a piggyback IOL is a viable retreatment option. PMID:27041983

  13. 硬性透气性角膜接触镜矫正圆锥角膜疗效分析%Clinical analysis of rigid gas permeable contact lens for keratoconus

    Institute of Scientific and Technical Information of China (English)

    张福生; 田晓丹; 徐艳春; 范春雷; 秦洁; 李艳; 巴秀凤

    2011-01-01

    Objective To evaluate the clinical efficacy and safety of RGP for keratoconus.Methods RGP corrected 63 cases of keratoconus in outpatient clinic from 2004 to 2010 were included in this study.Among them 41 males and 22 females,16-35 years old with mean aged (24.6± 7.81),Binoculus in 57 cases,ocellus in 6 cases.The patients who had significantly increased astigmatism and decreased visual acuity with glasses were detected with computer refractometer,corneal topographer and corneal endothelial microscopy for screening keratoconus.For the diagnosed or suspected keratoconus,based on the degree of corneal curvature,use a specially designed or seneral RGP to correct.The corrected visual acuity was measure with RGP and optometry with RGP.All the measured results were analyzed with correlation analysis with SPSS13.0 software,P <0.05 was significant differences.Results (1)The mean visual acuity with glasses:0.56+ 0.29,the mean visual acuity with RGP:0.93± 0.20,(t =-14.627,P =0.000).The corrected visual acuity with RGP was significantly better than with glasses.(2)The mean astigmatism before wearing RGP:(-4.16± 2.19)DC,the mean astigmatism with RGP:(-0.77+ 1.2)DC (t =-14.585,P =0.000).There was an obvious decrease of astigmatism with RGP.(3)In average 3.5 years' observation in 22 eyes,only 1 eye appeared corneal increased turbid,implemented lamellar corneal transplantation.There was a significant decreased astigmatism in the other 21 patients.Corneal thickness and corneal curvature were no significant difference.Conclusions RGP for irregular astigmatism of keratoconus can significantly improve the visual acuity to a certain extent and slow down the progress of keratoconus disease.%目的 探讨硬性透气性角膜接触镜(RGP)矫正圆锥角膜的临床疗效及安全性.方法 对2004~2010年视光门诊应用RGP矫正的63例圆锥角膜患者,男41例,女22例.年龄16-35岁,平均年龄(24.6±7.81)岁.双眼57例,单眼6例.对散光度明显增大,框架眼镜

  14. Analysis of the reasons for decentration after orthokeratology%配戴角膜塑形镜后光学区偏中心原因分析

    Institute of Scientific and Technical Information of China (English)

    付心怡; 张晓峰; 夏静; 杨牧

    2016-01-01

    ten myopes (213 eyes,age range,6.5~17.0 years) were fitted with overnight orthokeratology lenses.Patients were divided among 3 groups based on age:6.5-10.0 years,group A;11.0-13.0 years,group B;and 14.0-17.0 years,group C.Patients were divided into 2 groups based on their initial spherical diopter <-3.00 D group and-3.00--6.00 D group.Patients were divided into 3 groups based on initial astigmatism:<0.50 D astigmatism group,0.50-1.00 D astigmatism group,and ≥l.00 D astigmatism group.Based on the distance of decentration at 3 months after orthokeratology,patients were divided into 3 groups:<0.5 mm decentration group,0.5-1.0 mm decentration group,and ≥ 1.0 mm decentration group.Corneal topography was measured before and 3 months after orthokeratology.The decentration (distance and angle) of the optical zone center after orthokeratology was calculated relative to the pupil center.Data were collected on the relevant factors affecting decentration after orthokeratology and the initial age,initial sperical diopter,initial astigmatism and initial corneal parameter.The data were analyzed with a t test,ANOVA test and Pearson correlation test.Results The mean distance for decentration 3 months after orthokeratology was 0.53±0.33 mm.The decentration was mainly located in the inferior temporal quadrant.After 3 months,a decentration distance of less than 0.5 mm was observed in 111 eyes (52.1%),0.5-1.0 mm in 81 eyes (38.0%) and more than 1.0 mm in 21 eyes (9.9%).There was no statistically significant difference in the decentration distance between the three age groups.Patients with a higher initial sperical diopter (t=1.76,P<0.05) and astigmatism (F=9.254,P<0.05) showed a greater decentmtion distance.The initial corneal keratometry value evaluated with the topographic map showed that the nasal side of the cornea was flatter than the temporal side.The initial corneal keratometry value was greater in patients with severe decentration (P<0.05).The correlation

  15. 脑瘫患儿伴发视觉障碍的临床研究%Clinical research on visual impairment of children with cerebral palsy

    Institute of Scientific and Technical Information of China (English)

    罗瑜琳; 唐璟; 谭艺兰; 邓姿峰; 肖志刚; 陶利娟

    2014-01-01

    AIM: To understand the common conditions of visual impairment in cerebral palsy children, and to provide the basis for early screening of eyes, early diagnosis and treatment, and promote the visual rehabilitation for children with cerebral palsy. METHODS:Two hundred and twenty-three children with cerebral palsy underwent routine ophthalmologic examination, including the position of eye and eyeball movement, indirect ophthalmoscopy or Retcam II fundus examination, mydriasis optometry check and flash-visual evoked potential ( F-VEP ) examination, and the results were recorded and analyzed. RESULTS: Strabismus, ametropia and changes of F-VEP were the mainly impairments in 223 children with cerebral palsy, and some children also were associated with ocular fundus disease.There were 174 children with different types of strabismus, including 121 children with esotropia, 36 children with exotropia, 15 children with vertical strabismus, and 2 children with nystagmus.There were 129 children ( 247 eyes ) with refractive errors, including 118 eyes with compound hyperopic astigmatism, 51 eyes with simple hyperopia, 33 eyes with mixed astigmatism, 19 eyes with compound myopic astigmatism, 21 eyes with simple hyperopia astigmatism, 4 eyes with simple myopia astigmatism, only 1 eye with simple myopia.The F-VEP of 194 children ( 381 eyes ) were abnormal, and performed as delayed latency and reduced amplitude of P2 wave.In addition, there were 51 children with different types of ocular fundus changes, in which optic nerve atrophy and retinal hemorrhage were the most common. CONCLUSION: Children with cerebral palsy often are associated with different types of visual dysfunction, which seriously affect the visual quality and systemic rehabilitation. Routine eye examination and visual training should be paid attention, which play an important role in the normal development of the visual system and comprehensive rehabilitation of children with cerebral palsy.%目的:了解脑瘫患

  16. Color light-emitting diode reflection topography: validation of keratometric repeatability in a large sample of wide cylindrical-range corneas

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    Kanellopoulos AJ

    2015-02-01

    Full Text Available Anastasios John Kanellopoulos,1,2 George Asimellis11LaserVision.gr Clinical and Research Eye Institute, Athens, Greece; 2New York University Medical School, New York, NY, USAPurpose: To investigate repeatability of steep and flat keratometry measurements, as well as astigmatism axis in cohorts with normal range and regular astigmatic such as: eyes following laser-assisted in situ keratomileusis (LASIK and normal population, as well as cohorts of high and irregular astigmatism such as keratoconic eyes, and keratoconic eyes following corneal collagen cross-linking, employing a novel corneal reflection topography device.Methods: Steep and flat keratometry and astigmatism axis measurement repeatability was investigated employing a novel multicolored-spot reflection topographer (Cassini in four study groups, namely a post myopic LASIK-treated Group A, a keratoconus Group B, a post-CXL keratoconus Group C, and a control Group D of routine healthy patients. Three separate, maps were obtained employing the Cassini, enabling investigation of the intra-individual repeatability by standard deviation. Additionally we investigated in all groups,the Klyce surface irregularity indices for keratoconus, the SAI (surface asymmetry index and the SRI (surface regularity index.Results: Flat keratometry repeatability was 0.74±0.89 (0.03 to 5.26 diopters (D in the LASIK Group A, 0.88±1.45 (range minimum to maximum, 0.00 to 7.84 D in the keratoconic Group B, and 0.71±0.94 (0.02 to 6.23 D in the cross-linked Group C. The control Group D had flat keratometry repeatability 0.36±0.46 (0.00 to 2.71 D. Steep keratometry repeatability was 0.64±0.82 (0.01 to 4.81 D in the LASIK Group A, 0.89±1.22 (0.02 to 7.85 D in the keratoconic Group B, and 0.93±1.12 (0.04 to 5.93 D in the cross-linked Group C. The control Group D had steep keratometry repeatability 0.41±0.50 (0.00 to 3.51 D. Axis repeatability was 3.45±1.62° (0.38 to 7.78° for the LASIK Group A, 4.12±3.17

  17. Análise comparativa da refração automática objetiva e refração clínica Automatic objective refraction and clinical refraction - a comparative analysis

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    Ricardo Uras

    2001-02-01

    automated objective refraction was performed using the automatic keratorefractor TOPCON 3000. Results: 1,001 eyes of 504 patients were studied. 45.2% were male patients and the mean age was 36.6 years. There was an overall concordance between clinical refraction and the automated objective refraction in 66.7% of the patients. The concordance of a spherical value, not considering variations of -0.50 to +0.50 SD was, approximately 90%. In simple hyperopic/myopic astigmatic eyes the concordance was 27.6%, in eyes with compound hyperopic/myopic astigmatism the concordance was 97.7%. Cycloplegia did not significantly affect this concordance. There was no significant difference regarding the axis of astigmatic eyes when using both techniques. Conclusion: Automated objective refraction is an useful tool in clinical refraction but clinical data should also be considered and the final lens prescription should never be based solely on the automated examination.

  18. Prevalência das ametropias e oftalmopatias em crianças pré-escolares e escolares em favelas do Alto da Boa Vista, Rio de Janeiro, Brasil Prevalence of the ametropias and eye diseases in preschool and school children of Alto da Boa Vista favelas, Rio de Janeiro, Brazil

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    Abelardo de Souza Couto Júnior

    2007-10-01

    prevalence was 3.50% (hyperopia and astigmatism hyperopic were 1.78%, myopia and astigmatism myopic 1.06%, mixed astigmatism 0.67%.The eyes diseases prevalence was 3.50% (amblyopia was 2.00%, manifest strabismus was 1.72% and others causes was 1.11%. CONCLUSION: It was shown the prevalence of the main ophthalmologic children disorders. It also points out the need of ocular health campaigns thus achieve remarkably the development of the children visual acuity.

  19. Relationship between Best Corrected Visual Acuity and Refraction Parameters in Myopia%近视者最佳矫正视力与屈光参数间的相关性

    Institute of Scientific and Technical Information of China (English)

    吕雅平; 夏文涛; 褚仁远; 周行涛; 戴锦晖; 周浩

    2011-01-01

    目的 探究近视者最佳矫正视力(best corrected visual acuity,BCVA)与屈光参数等相关指标之间的相关性.方法 选取2274例(4245眼)不同程度近视者,检测近视者的BCVA和球镜屈光度(diopter ofspherical,DS)、柱镜屈光度(diopter of cylinder,DC)、柱镜轴位、眼轴长度(axial length,AL)、角膜厚度等屈光参数,分析上述因素对BCVA的影响,并建立了BCVA与上述屈光参数以及年龄、性别等指标的相关性数学模型.结果 logistic回归分析显示BCVA(y)与DS(x1)、DC(x2)、性别(x3)、AL(x4)、角膜厚度(x5)、柱镜轴位(x6)、年龄(x7)之间有相关性(P<0.05):y0.5806-0.0340x1-0.0468x2+0.0565x3+0.0165x4+0.0007x5+0.0002x6-0.0058x7.结论 近视者的年龄、性别和角膜厚度对BCVA存在微弱的影响,DS、DC、AL及柱镜轴位对BCVA有着明显的影响.随着DS和DC的增加,AL的延长,BCVA呈现明显的下降趋势.综合分析屈光参数可以帮助评估近视者的视力状况.%Objective To explore the relationship between best corrected visual acuity(BCVA) and refraction parameters in myopia. Methods Two thousand two hundred and seventy-four patients (4245 eyes)with different degrees of myopia were collected. Their BCVA, diopter of spherical (DS), diopter of cylinder (DC), astigmatism axis, axial length (AL) and corneal thickness were detected. The influence of those parameters on BCVA was studied and the mathematical model of the relationship between BCVA and other parameters including the age and gender of patients was established. Results The logistic regression analysis showed that there were correlations between the BCVA(y) and DS(x1, DC(x2), gender(x3), AL(x4), corneal thickness (x5), astigmatism axis (x6) and age (x7) (Pastigmatism axis have significant

  20. Exploration on the indexes of taking off glasses after recovery in children with amblyopia%儿童弱视愈后脱镜指标的探讨

    Institute of Scientific and Technical Information of China (English)

    王洪峰; 王恩荣; 廖美婷; 邢玉琴

    2011-01-01

    目的:探讨儿童弱视治愈后脱镜指标.方法:儿章弱视治愈后必须符合4项指标才能脱镜,脱镜后要继续追踪观察3年.结果:368例678眼的弱视儿童治愈后,经3~7年的治疗,有205例364眼脱镜,占治愈眼数的53.69%.其中轻度弱视脱镜244眼,高于中度(114眼)和重度(6眼);屈光不正性弱视脱镜305眼,屈光参差性29眼,斜视性30眼;单纯远视性弱视脱镜316眼,高于单纯远散(11眼)和复性远散(37眼);而单纯近视性弱视和单纯近散、复性近散性弱视均没能脱镜.弱视儿童初戴眼镜属低屈光度脱镜289眼,中度58眼,高度17眼.从就诊时的年龄上看3~8周岁者脱镜率高.结论:儿童弱视治愈后按照4项脱镜指标摘掉眼镜是可行的.在脱镜前一定要坚持治疗复诊,即使脱镜后也要坚持追踪观察,最好观察超过视力发育敏感期12周岁之后.%Objective: To explore the indexes of taking off glasses after recovery in children with amblyopia. Methods: The children with amblyopia could take off their glasses after recovery when they accorded with four indexes, and all the children were followed up for three years after taking off glasses. Results: 368 children (678 eyes) with amblyopia were selected, after treatment for 3 ~ 7 years, 205 children (364 eyes) took off glasses, accounting for 53.69%, including 244 eyes of mild amblyopia, the proportion was higher than those of middle amblyopia (114 eyes) and severe amblyopia (6 eyes) ; 305 eyes had ametropic amblyopia, 29 eyes had anisometropic amblyopia and 30 eyes had strabismic amblyopia; 316 eyes had simple hypermetropic amblyopia, the proportion was higher than those of simple hypermetropic astignatism ( 11 eyes) and complex astigmatism (37 eyes) ; the children with simple myopic amblyopia, simple myopic astigmatism and complex myopic astigmatism did not take off glasses; 289 eyes were low diopter, 58 eyes were middle diopter and 17 eyes were high diopter; the rate of taking

  1. Estudo prospectivo comparativo de duas técnicas cirúrgicas de extração extra-capsular planejada de catarata com implante de lente intra-ocular: incisão limbar e incisão escleral tunelizada Prospective comparative study of two techniques of planned extracapsular cataract extraction: limbal incision and scleral tunnel incision

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    Lincoln Lemes Freitas

    2001-06-01

    extraction (ECCE with posterior chamber intraocular lens implantation. This study aims to compare limbal incision and scleral tunnel incision in planned ECCE. Methods: Fifty-four consecutive patients (59 eyes with follow-up of 6 months were studied prospectively. ECCE with limbal incision was performed in 30 patients (Group I, and with scleral tunnel incision in 29 patients (Group II. Corrected visual acuity, intraocular inflammation (cells and flare, surgical time, specular microscopy, induced astigmatism and pachymetry were assessed. Results: Surgical time, endothelial cells loss and induced astigmatism were statistically greater in group I than in group II. No significant differences were found between groups when comparing the corrected visual acuity, intraocular inflammation and pachymetry. Conclusions: ECCE with scleral tunnel incision technique offers advantages regarding surgical time, endothelial cells loss and induced astigmatism if compared with limbal incision technique. Surgical steps used in this technique help in transition for phacoemulsification with low cost and a safer way.

  2. Accurate test of optical wave front for optical imaging system%光学成像系统光学波前的高精度测试

    Institute of Scientific and Technical Information of China (English)

    邵晶; 马冬梅; 聂真威

    2011-01-01

    Based on the Extended Nijboer-Zernike theory, the effect of different amplitudes for exit pupils on the image intensity in the focal plane was analyzed. A novel approach was applied to testing the wavefront according to the actual condition of the amplitude in the exit pupil, which can help eliminating the error caused by the nonuniformity illuminated pupil and the Fast Fourier Transform in the o-riginal phase retrieval algorithms. A testing experiment was performed on an imaging optical system, and obtained results show that the tested wave fronts in the exit pupil of a camera lens are 0. 196 5X in PV and 0. 022 4X in RMS (the testing wavelength X is 632. 8 nm). The aberrations in the wavefront are mainly astigmatism, coma and high order astigmatism. Furthermore, the approach can also be used to analyze the amplitude in the exit pupil of a camera lens and calculate the light intensity distribution on other focal planes. The experiment proves this approach available.%基于扩展奈波尔-泽尼克理论,分析了不同出瞳振幅分布情况对光学系统焦面处光强分布的影响.针对光学成像系统出瞳振幅实际分布状态,提出了一种新的测试光学波前的方法,解决了相位恢复算法中出瞳振幅分布不均匀和快速傅里叶变换引入计算误差的问题.通过测评实验,对一光学系统进行了测试,获得的光学系统出瞳波前(PV)值为0.196 5λ,RMS值为0.022 4λ(测试波长λ=632.8 nm),此波前中主要含有像散、彗差和高阶像散等像差.该方法亦可用于分析光学系统出瞳振幅分布,数值计算其他焦面处的光强分布.测评实验证明了此方法的有效性.

  3. 小切口非超声乳化白内障联合青光眼的围手术期护理%Small Incision Phacoemulsification Cataract and Glaucoma on the Perioperative Period Nursing

    Institute of Scientific and Technical Information of China (English)

    张建红

    2014-01-01

    Objective To approach peri operation period nursing of combined cataract and glaucoma by small incision phacoemulsification. Method To analyze 48 cases (60 eyes) clinical data of combined cataract and glaucoma in our hospital ophthalmology from October 2010 to August 2013, which was to be divided into routine nursing group (24 cases, 30 eyes) and special nursing group (24 cases, 30 eyes). Result The postoperative visual acuity, intraocular pressure and the degree of astigmatism of combined cataract and glaucoma of special nursing group were better than routine nursing group, P<0.05, the difference were statistical significance. Conclusion The postoperative visual acuity, intraocular pressure and the degree of astigmatism were obviously increased of combined cataract and glaucoma by special nursing, reduced the postoperative complications, which was to be used.%目的:探讨小切口非超声乳化白内障联合青光眼的围手术期护理情况。方法分析我院2010年10月至2013年8月眼科收治的青光眼并白内障患者48例(60眼)临床资料,依据护理措施不同进行分组,常规护理组(24例、30眼)和特殊护理组(24例、30眼)。结果特殊护理组青光眼并白内障患者术后视力、眼压和散光度数明显优于常规护理组P<0.05,差异均有统计学意义。结论特殊护理措施在小切口非超声乳化白内障联合青光眼围手术期应用可以明显提高术后视力、眼压和散光度数,值得临床推广应用。

  4. Visual performance and aberration associated with contact lens wear in patients with keratoconus: a pilot study

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    Abdu M

    2014-08-01

    Full Text Available Mustafa Abdu, Norhani Mohidin, Bariah Mohd-Ali Optometry and Vision Science Program, School of Healthcare Sciences, Faculty of Health Science, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, Kuala Lumpur, Malaysia Background: Rigid gas permeable (RGP and silicone hydrogel (SH contact lenses with specific designs are currently being used to improve visual function in patients with keratoconus. However, there are minimal data available comparing the effects of these lenses on visual function in patients with keratoconus. The objectives of this study were to compare visual acuity and contrast sensitivity using spectacles, RGP lenses, and SH lenses, and to evaluate the effects of RGP and SH lenses on higher-order aberrations and visual quality in eyes with keratoconus. The relationship between visual outcomes, aberration, and visual quality were also examined. Methods: This was a pilot study involving 13 eyes from nine subjects with keratoconus. Subjects were fitted with RGP and SH contact lenses. Visual acuity and contrast sensitivity were measured using Snellen and Pelli-Robson charts, respectively. Ocular aberrations and visual quality were measured using an OPD-Scan II device. All measurements were conducted before and after contact lens wear. Results: Significantly better visual acuity was obtained with RGP lenses than with spectacles or SH lenses (P<0.001. No significant difference in contrast sensitivity values was detected between RGP and SH lenses (P=0.06. Both SH and RGP lenses significantly reduced total ocular and higher-order aberrations (P<0.001 when compared with spectacles, but RGP lenses reduced trefoil, coma, and spherical aberrations more than SH lenses. No significant difference in astigmatic aberrations was found between RGP and SH lenses (P=0.12. Negative correlations were found between visual acuity and coma aberration and contrast sensitivity with higher-order aberrations and coma, trefoil, and astigmatic

  5. Microfocusing at the PG1 beamline at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Dziarzhytski, Siarhei, E-mail: siarhei.dziarzhytski@desy.de [DESY, Notkestrasse 85, 22067 Hamburg (Germany); Gerasimova, Natalia [European XFEL GmbH, Albert-Einstein-Ring 19, 22761 Hamburg (Germany); Goderich, Rene [University of South Florida (United States); Mey, Tobias [Laser Laboratorium Göttingen eV, Hans-Adolf-Krebs-Weg 1, 37077 Göttingen (Germany); Reininger, Ruben [Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439 (United States); Rübhausen, Michael [University of Hamburg and Center for Free-Electron Laser Science, Notkestrasse 85, 22607 Hamburg (Germany); Siewert, Frank [Institute for Nanometre Optics and Technology at Helmholtz Zentrum Berlin/BESSY II, Albert-Einstein-Strasse 15, 12489 Berlin (Germany); Weigelt, Holger; Brenner, Günter [DESY, Notkestrasse 85, 22067 Hamburg (Germany)

    2016-01-01

    The Kirkpatrick–Baez (KB) refocusing mirrors unit at the PG1 beamline at FLASH has been newly designed, developed and fully commissioned. The vertical focal size of the KB optics is measured to be 5.8 ± 1 µm FWHM and the horizontal 6 ± 2 µm FWHM; astigmatism has been minimized to below 1 mm between waist positions. Such a tight focus is essential for the VUV double Raman spectrometer as it serves as an entrance slit for the first monochromator and defines its resolution to a very large extent. The Raman spectrometer is a permanent end-station at the PG1 beamline, dedicated to inelastic soft X-ray scattering experiments. The Kirkpatrick–Baez (KB) refocusing mirror system installed at the PG1 branch of the plane-grating monochromator beamline at the soft X-ray/XUV free-electron laser in Hamburg (FLASH) is designed to provide tight aberration-free focusing down to 4 µm × 6 µm full width at half-maximum (FWHM) on the sample. Such a focal spot size is mandatory to achieve ultimate resolution and to guarantee best performance of the vacuum-ultraviolet (VUV) off-axis parabolic double-monochromator Raman spectrometer permanently installed at the PG1 beamline as an experimental end-station. The vertical beam size on the sample of the Raman spectrometer, which operates without entrance slit, defines and limits the energy resolution of the instrument which has an unprecedented design value of 2 meV for photon energies below 70 eV and about 15 meV for higher energies up to 200 eV. In order to reach the designed focal spot size of 4 µm FWHM (vertically) and to hold the highest spectrometer resolution, special fully motorized in-vacuum manipulators for the KB mirror holders have been developed and the optics have been aligned employing wavefront-sensing techniques as well as ablative imprints analysis. Aberrations like astigmatism were minimized. In this article the design and layout of the KB mirror manipulators, the alignment procedure as well as microfocus

  6. Effect of sutureless small incision cataract surgery plus intraocular lens implantation on Africans with cataract: a report of 1 730 cases%小切口无缝线白内障摘除加人工晶体植入术1730例临床疗效观察

    Institute of Scientific and Technical Information of China (English)

    庞永明; 李辉

    2011-01-01

    Objective To investigate the effect of suture less small incision cataract surgery (SICS) plus intraocular lens (IOL) implantation for Africans with cataract. Methods Sutureless SICS plus IOL implantation was conducted on 1 730 African patients with cataract, a total of 2 207 eyes. The clinical effect was evaluated. Results One week after the surgery, 1 403 eyes were found with vision ≥0.5 (63.6%), and 112 were found with vision ≥1.0 (5.1%), with astigmatism of (1.96±0.72) D. Three months after the surgery, 2 094 eyes were found with vision ≥0.5 (94.9%), and 136 were found with vision ≥ 1.0 (6.2%), with astigmatism of (0.87±0.54) D. Conclusion Sutureless SICS plus IOL implantation leads to a smaller chance of injury and provides ideal vision recovery, which is worthy to be extended in African.%目的 探讨小切口无缝线白内障囊外摘除加人工晶体植入术治疗非洲黑人白内障的临床疗效.方法对1 730例(2 207眼)黑人白内障患者行小切口无缝线白内障囊外摘除及人工晶体植入术,评估疗效.结果术后1周视力≥0.5者占63.6%(1 403眼),视力≥1.0者占5.1%(112眼),散光为(1.96±0.72)D.3个月后视力≥0.5者占94.9%(2094眼).视力≥1.0 (136眼)占6.2%,散光为(0.87±0.54)D.结论小切口无缝线白内障囊外摘除及人工晶体植入术损伤小、术后视力恢复好,在非洲地区有推广运用价值.

  7. One-site versus two-site phacotrabeculectomy: a prospective randomized study

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    Moschos MM

    2015-08-01

    Full Text Available Marilita M Moschos,1 Irini P Chatziralli,2 Michael Tsatsos3 1First Department of Ophthalmology, University of Athens, 2Second Department of Ophthalmology, Ophthalmiatrion Athinon, Athens, Greece; 3Department of Ophthalmology, Cambridge University Hospital NHS, Cambridge, UK Purpose: The purpose of this study is to compare the efficacy and safety of one-site and two-site combined phacotrabeculectomy with foldable posterior chamber intraocular lens implantation.Methods: Thirty-four patients (41 eyes with glaucoma and cataract were randomly assigned to undergo either a one-site (22 eyes or a two-site (19 eyes combined procedure. One-site approach consisted of a standard superior phacotrabeculectomy with a limbus-based conjunctival flap, while two-site approach consisted of a clear cornea phacoemulsification and a separate superior trabeculectomy with a limbus-based conjunctival flap.Results: Mean follow-up period was 54 months (standard deviation [SD] 2.3. Mean preoperative intraocular pressure (IOP in the one-site group was 21.3 mmHg (SD 2.8 and in the two-site group was 21.8 mmHg (SD 3.0 (P>0.1. Mean postoperative IOP significantly decreased in both groups compared to the preoperative level and was 15.6 mmHg (SD 3.5 in the one-site group and 14.9 mmHg (SD 2.7 in the two-site group. Three months later, the difference between the two groups was not statistically significant (P=0.058. The one-site group required significantly more medications than the two-site group (P=0.03. Best-corrected visual acuity (BCVA improved similarly in both groups, but there was less postoperative (induced astigmatism in the two-site group in a marginal statistical level (P=0.058. Intra- and postoperative complications were comparable in the two groups.Conclusion: Both techniques yielded similar results concerning final BCVA and IOP reduction. However, the two-site group had less induced astigmatism and a better postoperative IOP control with less required

  8. EARLY DETECTION OF LAW VISION WITH PRE-SCHOOL CHILDREN TRHOUG SYSTEMATIC CHECK-UPS AT THE AGE OF 3 AND 5 IN BITOLA

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    M. SOTIROVSKA-SIRVINI

    1997-12-01

    Full Text Available The early detection of the law vision of pre-school children has been carried out through systematic check-ups by an ophthalmologist sent by the Department for preventive protection-Advisory Division at the Medical Center since 1977.The children are invited by the Advisory Center and during the systematic check-ups they are sent to the Cabinet for orthoptics and pleoptics for the ophthamologic check-up.The parents are motivated for the check-up and are explained how to prepare the child for cooperation during the examination. The findings are recorded in the child record card in the Advisory Center together with the findings of the psychologist, blood test, urine, faecal test of parasites and some other necessary tests.The records of the examination were obtained from the evidence on systematic check-ups at the Cabinet for orthoptics and pleoptics.From 1987 till August this year, 5.414 children-3.609 at the age of 3 and 1.805 at the age of 5 came for systematic check-ups at the Cabinet.Among the examined children, 5.7% were with echophobia, 2.3% were with astigmatism, 1.6% with amblyopia, 1.4% with hypermetropia, 0.9% with strabismus and 0.2% with miopia.Among the children with sight problems, the echophobia is present with 47.3%, astigmatism with 18.8%, amblyopia with 13.2%, hypermetropia with 11.9%, strabism with 7.2% and miopia with 1.8%.Children whose parents, brothers and sisters wear glasses were sent for check-ups at the age of 18 to 3 years. The earliest findings of sight difficulties are obtained with children who cooperate during the check-ups.As soon as the low vision is discovered, the defectologist-orthoptic therapist starts the necessary exercises and the sight is corrected with the glasses.At this age, children easily adapt to wearing glasses and they do not oppose them as the children whose sight correction started at the school age.

  9. Optical quality of toric intraocular lens implantation in cataract surgery

    Institute of Scientific and Technical Information of China (English)

    Xian-Wen; Xiao; Jing; Hao; Hong; Zhang; Fang; Tian

    2015-01-01

    AIM: To analyze the optical quality after implantation of toric intraocular lens with optical quality analysis system.METHODS: Fifty-two eyes of forty-four patients with regular corneal astigmatism of at least 1.00 D underwent implantation of Acry Sof toric intraocular lens, including T3 group 19 eyes, T4 group 18 eyes, T5 group 10 eyes,T6 group 5 eyes. Main outcomes evaluated at 3mo of follow-up, included uncorrected distance visual acuity(UDVA), corrected distance visual acuity(CDVA), residual refractive cylinder and intraocular lens(IOL) axis rotation.Objective optical quality were measured using optical quality analysis system(OQAS Ⅱ, Visiometrics, Spain),included the cutoff frequency of modulation transfer function(MTFcutoff), objective scattering index(OSI),Strehl ratio, optical quality analysis system value(OV)100%, OV 20% and OV 9% [the optical quality analysis system(OQAS) values at contrasts of 100%, 20%, and 9%].RESULTS: At 3mo postoperative, the mean UDVA and CDVA was 0.18 ±0.11 and 0.07 ±0.08 log MAR; the mean residual refractive cylinder was 0.50 ±0.29 D; the mean toric IOL axis rotation was 3.62 ±1.76 degrees, the mean MTFcutoff, OSI, Strehl ratio, OV 100%, OV 20% and OV9% were 22.862 ±5.584, 1.80 ±0.84, 0.155 ±0.038, 0.76 ±0.18,0.77±0.19 and 0.78±0.21. The values of UDVA, CDVA, IOL axis rotation, MTFcutoff, OSI, Strehl ratio, OV100%,OV20% and OV9% depending on the power of the cylinder of the implantation were not significantly different(P >0.05), except the residual refractive cylinder(P <0.05).CONCLUSION: The optical quality analysis system was useful for characterizing the optical quality of Acry Sof toric IOL implantation. Implantation of an Acry Sof toric IOL is an effective and safe method to correct corneal astigmatism during cataract surgery.

  10. Gendered Disparities in Quality of Cataract Surgery in a Marginalised Population in Pakistan: The Karachi Marine Fishing Communities Eye and General Health Survey.

    Directory of Open Access Journals (Sweden)

    Khabir Ahmad

    Full Text Available Marine fishing communities are among the most marginalised and hard-to-reach groups and have been largely neglected in health research. We examined the quality of cataract surgery and its determinants, with an emphasis on gender, in marine fishing communities in Karachi, Pakistan, using multiple indicators of performance.The Karachi Marine Fishing Communities Eye and General Health Survey was a door-to-door, cross-sectional study conducted between March 2009 and April 2010 in fishing communities living on 7 islands and in coastal areas in Keamari, Karachi, located on the Arabian Sea. A population-based sample of 638 adults, aged ≥ 50 years, was studied. A total of 145 eyes (of 97 persons had undergone cataract surgery in this sample. Cataract surgical outcomes assessed included vision (presenting and best-corrected with a reduced logMAR chart, satisfaction with surgery, astigmatism, and pupil shape. Overall, 65.5% of the operated eyes had some form of visual loss (presenting visual acuity [PVA] < 6/12. 55.2%, 29.0%, and 15.9% of these had good, borderline, and poor visual outcomes based on presenting vision; with best correction, these values were: 68.3 %, 18.6%, and 13.1%, respectively. Of 7 covariates evaluated in the multivariable generalized estimating equations (GEE analyses, gender was the only significant independent predictor of visual outcome. Women's eyes were nearly 4.38 times more likely to have suboptimal visual outcome (PVA<6/18 compared with men's eyes (adjusted odds ratio 4.38, 95% CI 1.96-9.79; P<0.001 after adjusting for the effect of household financial status. A higher proportion of women's than men's eyes had an irregular pupil (26.5% vs. 14.8% or severe/very severe astigmatism (27.5% vs. 18.2%. However, these differences did not reach statistical significance. Overall, more than one fourth (44/144 of cataract surgeries resulted in dissatisfaction. The only significant predictor of satisfaction was visual outcome (P <0

  11. A method to design aspheric spectacles for correction of high-order aberrations of human eye

    Institute of Scientific and Technical Information of China (English)

    LI Rui; WANG ZhaoQi; LIU YongJi; MU GuoGuang

    2012-01-01

    Aiming at the correction of high-order aberrations of human eye with spectacles,a design method of aspheric spectacles is proposed based on the eye's wavefront aberrations data.Regarding the eyeball and the spectacles as a whole system-the lens-eye system-the surface profiles of the spectacles are achieved by optimization procedure of lens design.Different from the conventional optometry,in which the refraction prescription is acquired with a visual chart,the design takes into account the two aspects of actual human viewing,eyeball rolling and certain distinct viewing field.The rotation angle of eyeball is set to be ±20° as wearing spectacles,and the field of view is set to be ∧7° which is especially important as watching screen display.The individual eye model is constructed as the main part of the lens-eye system.The Liou eye model is modified by sticking a thin meniscus lens to the crystalline lens.Then the defocus of the individual eye is transferred to the front surface of the meniscus lens,and the astigmatism and high-order aberrations are transferred to the front surface of the cornea.50 eyes are involved in this research,among which 36 eyes have good enough visual performance already after sphero-cylindrical correction.10 eyes have distinct improvement in vision and 4 eyes have no visual improvement by further aspheric correction.6 typical subject eyes are selected for the aberrations analysis and the spectacles design in this paper.It is shown that the validity of visual correction of aspheric lens depends on the characteristics of the eye's wavefront aberrations,and it is effective for the eye with larger astigmatism or spherical aberration.Compared with sphero-cylindrical correction only,the superiority taken by the aspheric correction is mainly on the improvement of MTF at a larger field of view.For the best aspheric correction,the MTF values increase by 18.87%,38.34%,44.36%,51.29% and 57.32% at the spatial frequencies of 40

  12. Descemet stripping automated endothelial keratoplasty (DSAEK with thin grafts in patients suffered bullous keratophaty with low preoperative visual acuity

    Directory of Open Access Journals (Sweden)

    S. V. Trufanov

    2014-07-01

    Full Text Available Purpose: To evaluate the results of DSAEK with thin grafts in patients suffered bullous keratophaty with low preoperative visual acuity.Methods: DSAEK with thin grafts the thickness of which was 150‑70 μm was fulfilled in 47 patients (47 eyes suffered bullous keratophaty without visible leukomas in the corneal stroma. Visual acuity prior to the operation with a maximum spectacle correction accounted for an average of 0.05±0.04. Tear film osmolarity of 20 patients (20 eyes who participated in the research was measured. Results: In follow-up period graft kept transparency in 39 patients. Visual acuity in 3 months after the operation, on average, without correction was 0.38±0.16, with a maximum of spectacle correction is 0.51± 0.18. The spherical component varied in the range from 0 to 3.75 D, with an average of 1.63 per±1.1 D. Corneal astigmatism was from 0.5 to 4.0 D, an average of 1.8±0.98 D. At preoperative osmolarity indicators were within the normal reference for both operated and non-operated eyes — 292.3±10.4 и 279.3±3.51. In a first postoperative week osmolarity was not detected while on a non-operated eye it was 278.4±1.4. After 1, 3 and 6 months osmolarity indicators on both eyes were within normal reference. Spherical component ranged from 0 to 3.75 D, averaging 1.1±1.63 D. Corneal astigmatism ranged from 0.5 to 4.0 (D, with an average of 1.8±0.98 D 1.63 per±1.1 D.Conclusion: DSAEK with thin grafts is an effective modern methods of surgical treatment of bullous keratophaty. For old patients with severe ocular pathology — concomitant eye diseases, repeated surgery of the eye, the developed stage of the keratophaty — we have not noted the apparent correlation between the thickness of the transplant, visual acuity and the time of recovery of visual functions after keratoplasty. Osmolarity in an early postoperative period is a non-informative method of diagnostics. Restoration of osmolarity level to preoperative

  13. Descemet stripping automated endothelial keratoplasty (DSAEK with thin grafts in patients suffered bullous keratophaty with low preoperative visual acuity

    Directory of Open Access Journals (Sweden)

    S. V. Trufanov

    2013-01-01

    Full Text Available Purpose: To evaluate the results of DSAEK with thin grafts in patients suffered bullous keratophaty with low preoperative visual acuity.Methods: DSAEK with thin grafts the thickness of which was 150‑70 μm was fulfilled in 47 patients (47 eyes suffered bullous keratophaty without visible leukomas in the corneal stroma. Visual acuity prior to the operation with a maximum spectacle correction accounted for an average of 0.05±0.04. Tear film osmolarity of 20 patients (20 eyes who participated in the research was measured. Results: In follow-up period graft kept transparency in 39 patients. Visual acuity in 3 months after the operation, on average, without correction was 0.38±0.16, with a maximum of spectacle correction is 0.51± 0.18. The spherical component varied in the range from 0 to 3.75 D, with an average of 1.63 per±1.1 D. Corneal astigmatism was from 0.5 to 4.0 D, an average of 1.8±0.98 D. At preoperative osmolarity indicators were within the normal reference for both operated and non-operated eyes — 292.3±10.4 и 279.3±3.51. In a first postoperative week osmolarity was not detected while on a non-operated eye it was 278.4±1.4. After 1, 3 and 6 months osmolarity indicators on both eyes were within normal reference. Spherical component ranged from 0 to 3.75 D, averaging 1.1±1.63 D. Corneal astigmatism ranged from 0.5 to 4.0 (D, with an average of 1.8±0.98 D 1.63 per±1.1 D.Conclusion: DSAEK with thin grafts is an effective modern methods of surgical treatment of bullous keratophaty. For old patients with severe ocular pathology — concomitant eye diseases, repeated surgery of the eye, the developed stage of the keratophaty — we have not noted the apparent correlation between the thickness of the transplant, visual acuity and the time of recovery of visual functions after keratoplasty. Osmolarity in an early postoperative period is a non-informative method of diagnostics. Restoration of osmolarity level to preoperative

  14. Development of a solid state laser of Nd:YLF

    International Nuclear Information System (INIS)

    The CW laser action was obtained at room temperature of a Nd:YLF crystal in an astigmatically compensated cavity, pumped by an argon laser. This laser was completely projected, constructed and characterized in our laboratories, thus having a high degree of nationalization. It initiates a broader project on lasers development that will have several applications like nuclear fusion, industry, medicine, telemetry, etc.... Throught the study of the optical properties of the Nd:YLF crystal, laser operation was predicted using a small volume gain medium on the mentioned cavity, pumped by an Ar 514,5 nm laser line. To obtain the laser action at polarizations σ (1,053 μm) and π (1,047 μm) an active medium was prepared which was a cristalline plate with a convenient crystalographic orientation. The laser characterization is in reasonable agreement with the initial predictions. For a 3.5% output mirror transmission, the oscillation threshold is about 0.15 W incident on the crystal, depending upon the sample used. For 1 W of incident pump light, the output power is estimated to be 12 mW, which corresponds to almost 1.5% slope efficiency. The versatile arrangement is applicable to almost all optically pumped solid state laser materials. (Author)

  15. Graphical user interfaces for teaching and design of GRIN lenses in optical interconnections

    International Nuclear Information System (INIS)

    The use of graphical user interfaces (GUIs) enables the implementation of practical teaching methodologies to make the comprehension of a given subject easier. GUIs have become common tools in science and engineering education, where very often, the practical implementation of experiences in a laboratory involves much equipment and many people; they are an efficient and inexpensive solution to the lack of resources. The aim of this work is to provide primarily physics and engineering students with a series of GUIs to teach some configurations in optical communications using gradient-index (GRIN) lenses. The reported GUIs are intended to perform a complementary role in education as part of a ‘virtual lab’ to supplement theoretical and practical sessions and to reinforce the knowledge acquired by the students. In this regard, a series of GUIs to teach and research the implementation of GRIN lenses in optical communications applications (including a GRIN light deflector and a beam-size controller, a GRIN fibre lens for fibre-coupling purposes, planar interconnectors, and an anamorphic self-focusing lens to correct astigmatism in laser diodes) was designed using the environment GUIDE developed by MATLAB. Numerical examples using available commercial GRIN lens parameter values are presented. (paper)

  16. Impact of capillarity forces on the steady-state self-organization in the thin chromium film on glass under laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Gedvilas, Mindaugas, E-mail: mgedvilas@ftmc.lt; Voisiat, Bogdan; Regelskis, Kęstutis; Račiukaitis, Gediminas

    2014-11-28

    Metal films on transparent substrates are widely used for mask production in lithography, and lasers are frequently applied for their patterning. Steady self-organization of a chromium thin film on the glass substrate to parallel metal lines under irradiation with partially overlapping highly astigmatic nanosecond laser pulses above the ablation threshold has been observed. Transformations in a chromium film were investigated experimentally and numerically. The theoretical model of the steady self-organization is presented and discussed. It was demonstrated that the capillarity convection force was responsible for the transformation process in the molten metal. It was shown that the thermo-capillarity (Marangoni) shear stress and the stress originating from a variation in the radius of curvature along the structure were equally important in the case of the steady self-organization process. - Highlights: • The model of steady-state self-organization in molten metal was developed. • The Marangoni convection pushes liquid metal from the hotter to cooler area. • The capillarity force pushes liquid metal because of gradient in curvature radius. • Shear stresses of thermal and radius of curvature gradients are equally important.

  17. Large binocular telescope interferometer adaptive optics: on-sky performance and lessons learned

    Science.gov (United States)

    Bailey, Vanessa P.; Hinz, Philip M.; Puglisi, Alfio T.; Esposito, Simone; Vaitheeswaran, Vidhya; Skemer, Andrew J.; Defrère, Denis; Vaz, Amali; Leisenring, Jarron M.

    2014-07-01

    The Large Binocular Telescope Interferometer is a high contrast imager and interferometer that sits at the combined bent Gregorian focus of the LBT's dual 8.4 m apertures. The interferometric science drivers dictate 0.1" resolution with 103 - 104 contrast at 10 μm, while the 4 μm imaging science drivers require even greater contrasts, but at scales <0.2". In imaging mode, LBTI's Adaptive Optics system is already delivering 4 μm contrast of 104 - 105 at 0.3" - 0.75" in good conditions. Even in poor seeing, it can deliver up to 90% Strehl Ratio at this wavelength. However, the performance could be further improved by mitigating Non-Common Path Aberrations. Any NCPA remedy must be feasible using only the current hardware: the science camera, the wavefront sensor, and the adaptive secondary mirror. In preliminary testing, we have implemented an "eye doctor" grid search approach for astigmatism and trefoil, achieving 5% improvement in Strehl Ratio at 4 μm, with future plans to test at shorter wavelengths and with more modes. We find evidence of NCPA variability on short timescales and discuss possible upgrades to ameliorate time-variable effects.

  18. Challenges and approaches in modern biometry and IOL calculation.

    Science.gov (United States)

    Haigis, Wolfgang

    2012-01-01

    The introduction of new intraocular lenses (IOLs), industry marketing to the public and patient expectations has warranted increased accuracy of IOL power calculations. Toric IOLs, multifocal IOLs, aspheric IOLs, phakic lenses, accommodative lenses, cases of refractive lens exchange and eyes that have undergone previous refractive surgery all require improved clinical measurements and IOL prediction formulas. Hence, measurement techniques and IOL calculation formulas are essential factors that affect the refractive outcome. Measurement with ultrasound has been the historic standard for measurement of ocular parameters for IOL calculation. However the introduction of optical biometry using partial coherence interferometry (PCI) has steadily established itself as the new standard. Additionally, modern optical instruments such as Scheimpflug cameras and optical coherence tomographers are being used to determine corneal power that was normally the purview of manual keratometry and topography. A number of methods are available to determine the IOL power including the empirical, analytical, numerical or combined methods. Ray tracing techniques or paraxial approximation by matrix methods or classical analytical 'IOL formulas' are actively used in for the prediction of IOL power. There is no universal formula for all cases - phakic and pseudophakic cases require different approaches, as do short eyes, long eyes, astigmatic eyes or post-refractive surgery eyes. Invariably, IOLs are characterized by different methods and lens constants, which require individual optimization. This review describes the current methods for biometry and IOL calculation. PMID:23960962

  19. Comparative investigation of nonparaxial mode propagation along the axis of uniaxial crystal

    Science.gov (United States)

    Khonina, S. N.; Kharitonov, S. I.

    2015-01-01

    We compare nonparaxial propagation of Bessel and Laguerre-Gaussian modes along the axis of anisotropic media. It is analytically and numerically shown that the nonparaxial laser modes propagating along the crystal axis are periodically oscillating owing to polarization conversion. The oscillation period for Bessel beams is inversely proportional to the square of the spatial frequency of the laser mode and the difference between the dielectric constants of an anisotropic crystal. So, for higher spatial frequency of Bessel beams, we will get shorter period of oscillations. For a linearly polarized light, there is a periodic redistribution of the energy between the two transverse components, and for a beam with the circular polarization, the energy is transferred from the initial beam to a vortex beam and backward. Similar periodic behavior is observed for the high-order in radial index Laguerre-Gaussian beams. However, it is true only at short distances. As the distance increases, the frequency of periodicity slows down and the beam is astigmatically distorted. We show that high-spatial-frequency nonparaxial beams can provide spin-orbit conversion efficiency close to 100% on small distances (tens of microns) of propagation along the axis of uniaxial crystals. It provides an opportunity of miniaturization of mode optical converters.

  20. NGS WFSs module for MAORY at E-ELT

    Science.gov (United States)

    Esposito, S.; Agapito, G.; Antichi, J.; Bonanno, A.; Carbonaro, L.; Giordano, C.; Spanò, P.

    We report on the natural guide star (NGS) wavefront sensors (WFS) module for MAORY, the multi-cojugate adaptive optics (MCAO) system for the ESO E-ELT. Three low-order, near-infrared (H-band), Shack-Hartmann sensors provide fast acquisition of the first 5 modes (tip, tilt, focus, astigmatism) on 3 natural guide stars over a 160 arcsec field of view. Three moderate-order (20x20), visible (600-800 nm), pyramid WFSs provide the slow Truth sensing to correct LGS wavefront estimates of low-order modes. These sensors are mounted onto three R-theta stages to patrol the field of view. The module is also equipped with a retractable, on-axis, high-order (80x80), visible, pyramid WFS for the single-conjugate AO (SCAO) mode of MAORY and MICADO. The visible WFSs share the same 80x80 pyramid WFS design. This choice enables also a MCAO NGS capability. Simulations show that Strehl ratios (SR) over 40% are reached with MCAO and three, 2x2 sub-apertures, NIR low-order WFSs working with H-mag=20 reference stars. In SCAO mode, 90% SR for a 8mag stars with a contrast down to 10-5, and 45% SR for a 16mag star, are achieved.

  1. Frequency of Color Vision Defect in Students of Mashhad Dental School and Evaluation of Related Factors

    Directory of Open Access Journals (Sweden)

    Mohammad Daryaeian

    Full Text Available Introduction: In esthetic dentistry, color matching ability is one of the influencing factors in treatment. To achieve this goal, matching the color of restoration with natural teeth is essential. The objective of this study was to determine the frequency of color vision defect in students of Mashhad Dental School and evaluation of related factors.Materials & Methods: In this descriptive analytical study, 356 students of Mashhad Dental School were evaluated. Demographic data including age, gender, color vision defect in relatives, use of glasses and contact lenses, refractive errors (myopia, hypermetropia and astigmatism were documented in the designed questionnaire. To determine the impaired color vision, Ishihara diagnostic test was used. Statistical analysis of SPSS version 19 was performed using Chi-Square and Logistic Regression tests at the significance level of 0.05%.Results: Color vision defect was found in 6% (12 persons of male students while none of the females were affected. All affected persons were red-green color blind and strong deutan. There was a significant relationship between color vision deficiency and history of color vision defect in relatives (P= 0.03, so that 25% (3 persons of affected persons had a positive family history of color vision defect. Conclusion: Considering the frequency of color vision defect in the present study as well as the importance of color matching in dental treatments and because most affected persons are unaware of this defect, color vision tests seem necessary.

  2. Photo-elastic effect, thermal lensing and depolarization in a-cut tetragonal laser crystals

    Science.gov (United States)

    Yumashev, K. V.; Zakharova, A. N.; Loiko, P. A.

    2016-06-01

    We report on analytical description of thermal lensing effect in tetragonal crystals cut along the [1 0 0] crystallographic axis, for the two principal light polarizations, E ┴ c and E || c, under diode-pumping (plane stress approximation). Within this approach, we take into account anisotropy of elastic, photo-elastic, thermal and optical properties of the material. Expressions for the ‘generalized’ thermo-optic coefficient χ are presented. It is shown that astigmatism of thermal lens is determined both by the photo-elastic and end-bulging effects. The sign of the photo-elastic term χ″ can be either positive or negative affecting significantly the sign of the thermal lens. Depolarization loss in a-cut tetragonal crystals is few orders of magnitude lower than that in cubic crystals. Calculations are performed for a-cut tetragonal molybdates, Nd:CaMoO4, Nd:PbMoO4 and Nd:NaBi(MoO4)2.

  3. Adaptive optics system for fast automatic control of laser beam jitters in air

    Science.gov (United States)

    Grasso, Salvatore; Acernese, Fausto; Romano, Rocco; Barone, Fabrizio

    2010-04-01

    Adaptive Optics (AO) Systems can operate fast automatic control of laser beam jitters for several applications of basic research as well as for the improvement of industrial and medical devices. We here present our theoretical and experimental research showing the opportunity of suppressing laser beam geometrical fluctuations of higher order Hermite Gauss modes in interferometric Gravitational Waves (GW) antennas. This in turn allows to significantly reduce the noise that originates from the coupling of the laser source oscillations with the interferometer asymmetries and introduces the concrete possibility of overcoming the sensitivity limit of the GW antennas actually set at 10-23 1 Hz value. We have carried out the feasibility study of a novel AO System which performs effective laser jitters suppression in the 200 Hz bandwidth. It extracts the wavefront error signals in terms of Hermite Gauss (HG) coefficients and performs the wavefront correction using the Zernike polynomials. An experimental Prototype of the AO System has been implemented and tested in our laboratory at the University of Salerno and the results we have achieved fully confirm effectiveness and robustness of the control upon first and second order laser beam geometrical fluctuations, in good accordance with GW antennas requirements. Above all, we have measured 60 dB reduction of astigmatism and defocus modes at low frequency below 1 Hz and 20 dB reduction in the 200 Hz bandwidth.

  4. [Health status of journalists and organization of work in a national daily newspaper].

    Science.gov (United States)

    Boscolo, P; Tulli, F; Fattorini, E; De Stefano, A; Rapinese, M; Carlesi, G; Castagnoli, A; Messineo, A

    1988-05-01

    A multidisciplinary investigation was performed on 173 reporters (53 men and 20 women) of a newspaper. The microclimate and illumination conditions of the main seat, in which the use of VDT was beginning, were satisfactory, although not all the instruments were correctly adjusted. A very low percentage of reporters working in the main center was suffering from arterial hypertension indicating the presence of the "healthy worker effect". The values of plasma cortisol and arterial blood pressure of 10 reporters of the main seat, except two cases, changed normally during the evening hours. It is to point out that among the reporters there was significant correlation between spondylosis and astigmatism. The psychological investigation evidenced that the reporters were aggressive, eager of success and with constant attention. The EMG biofeedback demonstrated in the reporters with a more prolonged period of employment nervous tension and difficulty in relaxing. Particularly, in the reporters of the main center, the Stait-Trait Anxiety Inventory was more altered than in those of the peripheral seats. PMID:3154751

  5. Formation of plasma channels in air under filamentation of focused ultrashort laser pulses

    Science.gov (United States)

    Ionin, A. A.; Seleznev, L. V.; Sunchugasheva, E. S.

    2015-03-01

    The formation of plasma channels in air under filamentation of focused ultrashort laser pulses was experimentally and theoretically studied together with theoreticians of the Moscow State University and the Institute of Atmospheric Optics. The influence of various characteristics of ultrashort laser pulses on these plasma channels is discussed. Plasma channels formed under filamentation of focused laser beams with a wavefront distorted by spherical aberration (introduced by adaptive optics) and by astigmatism, with cross-section spatially formed by various diaphragms and with different UV and IR wavelengths, were experimentally and numerically studied. The influence of plasma channels created by a filament of a focused UV or IR femtosecond laser pulse (λ = 248 nm or 740 nm) on characteristics of other plasma channels formed by a femtosecond pulse at the same wavelength following the first one with varied nanosecond time delay was also experimentally studied. An application of plasma channels formed due to the filamentation of focused UV ultrashort laser pulses including a train of such pulses and a combination of ultrashort and long (~100 ns) laser pulses for triggering and guiding long (~1 m) electric discharges is discussed.

  6. X-ray tests of a two-dimensional stigmatic imaging scheme with variable magnifications

    Science.gov (United States)

    Lu, J.; Bitter, M.; Hill, K. W.; Delgado-Aparicio, L. F.; Efthimion, P. C.; Pablant, N. A.; Beiersdorfer, P.; Caughey, T. A.; Brunner, J.

    2014-11-01

    A two-dimensional stigmatic x-ray imaging scheme, consisting of two spherically bent crystals, one concave and one convex, was recently proposed [M. Bitter et al., Rev. Sci. Instrum. 83, 10E527 (2012)]. The Bragg angles and the radii of curvature of the two crystals of this imaging scheme are matched to eliminate the astigmatism and to satisfy the Bragg condition across both crystal surfaces for a given x-ray energy. In this paper, we consider more general configurations of this imaging scheme, which allow us to vary the magnification for a given pair of crystals and x-ray energy. The stigmatic imaging scheme has been validated for the first time by imaging x-rays generated by a micro-focus x-ray source with source size of 8.4 μm validated by knife-edge measurements. Results are presented from imaging the tungsten Lα1 emission at 8.3976 keV, using a convex Si-422 crystal and a concave Si-533 crystal with 2d-spacings of 2.21707 Å and 1.65635 Å and radii of curvature of 500 ± 1 mm and 823 ± 1 mm, respectively, showing a spatial resolution of 54.9 μm. This imaging scheme is expected to be of interest for the two-dimensional imaging of laser produced plasmas.

  7. Optical design of a stigmatic extreme-ultraviolet spectroscopic system for emission and absorption studies of laser-produced plasmas

    International Nuclear Information System (INIS)

    The design of a stigmatic spectroscopic system for diagnostics of laser-produced plasmas in the 2.5-40-nm region is presented. The system consists of a grazing-incidence toroidal mirror that focuses the radiation emitted by a laser-produced plasma onto the entrance slit of a spectrograph. The latter has a grazing-incidence spherical variable-line-spaced grating with flat-field properties coupled to a spherical focusing mirror that compensates for the astigmatism. The mirror is crossed with respect to the grating; i.e., it is mounted with its tangential plane coincident with the equatorial plane of the grating. The spectrum is acquired by an extreme-UV- (EUV-) enhanced CCD detector with high quantum efficiency. This stigmatic design also has spectral and spatial resolution capability for extended sources: The spectral resolution is also preserved for off-plane points, whereas the spatial resolution decreases for points far from the optical axis. The expected performance is presented and compared with that of a stigmatic design with a plane variable-line-spaced grating illuminated in converging light

  8. Refractive Errors Affect the Vividness of Visual Mental Images

    Science.gov (United States)

    Palermo, Liana; Nori, Raffaella; Piccardi, Laura; Zeri, Fabrizio; Babino, Antonio; Giusberti, Fiorella; Guariglia, Cecilia

    2013-01-01

    The hypothesis that visual perception and mental imagery are equivalent has never been explored in individuals with vision defects not preventing the visual perception of the world, such as refractive errors. Refractive error (i.e., myopia, hyperopia or astigmatism) is a condition where the refracting system of the eye fails to focus objects sharply on the retina. As a consequence refractive errors cause blurred vision. We subdivided 84 individuals according to their spherical equivalent refraction into Emmetropes (control individuals without refractive errors) and Ametropes (individuals with refractive errors). Participants performed a vividness task and completed a questionnaire that explored their cognitive style of thinking before their vision was checked by an ophthalmologist. Although results showed that Ametropes had less vivid mental images than Emmetropes this did not affect the development of their cognitive style of thinking; in fact, Ametropes were able to use both verbal and visual strategies to acquire and retrieve information. Present data are consistent with the hypothesis of equivalence between imagery and perception. PMID:23755186

  9. E-beam column monitoring for improved CD SEM stability and tool matching

    Science.gov (United States)

    Hayes, Timothy S.; Henninger, Randall S.

    2000-06-01

    Tool matching is an important metric for in-line semiconductor metrology systems. The ability to obtain the same measurement results on two or more systems allows a semiconductor fabrication facility (fab) to deploy product in an efficient manner improving overall equipment efficiency (OEE). Many parameters on the critical dimension scanning electron microscopes (CDSEMs) can affect the long-term precision component to the tool-matching metric. One such class of parameters is related to the electron beam column stability. The alignment and condition of the gun and apertures, as well as astigmatism correction, have all been found to affect the overall measurements of the CDSEM. These effects are now becoming dominant factors in sub-3nm tool-matching criteria. This paper discusses the methodologies of column parameter monitoring and actions and controls for improving overall stability. Results have shown that column instabilities caused by contamination, gun fluctuations, component failures, detector efficiency, and external issues can be identified through parameter monitoring. The Applied Materials (AMAT) 7830 Series CDSEMs evaluated at IBM's Burlington, Vermont manufacturing facility have demonstrated 5 nm tool matching across 11 systems, which has resulted in non-dedicated product deployment and has significantly reduced cost of ownership.

  10. Development of an imaging VUV monochromator in normal incidence region

    International Nuclear Information System (INIS)

    This paper describes a development of the two-dimensional imaging monochromator system. A commercial normal incidence monochromator working on off-Rowland circle mounting is used for this purpose. The imaging is achieved with utilizing the pinhole camera effect created by an entrance slit of limited height. The astigmatism in the normal incidence mounting is small compared with a grazing incidence mount, but has a finite value. The point is that for near normal incidence, the vertical focusing with a concave grating is produced at outside across the exit slit. Therefore, by putting a 2-D detector at the position away from the exit slit (∼30 cm), a one-to-one correspondence between the position of a point on the detector and where it originated in the source is accomplished. This paper consists of 1) the principle and development of the imaging monochromator using the off-Rowland mounting, including the 2-D detector system, 2) a computer simulation by ray tracing for investigations of the imaging properties of imaging system, and aberration from the spherical concave grating on the exit slit, 3) the plasma light source (TPD-S) for the test experiments, 4) Performances of the imaging monochromator system on the spatial resolution and sensitivity, and 5) the use of this system for diagnostic studies on the JIPP T-IIU tokamak. (J.P.N.)

  11. Cuba on our minds

    Directory of Open Access Journals (Sweden)

    Charles Rutheiser

    2002-07-01

    Full Text Available [First paragraph] Conversatons with Cuba. C. PETER RIPLEY. Athens: University of Georgia Press, 1999. xxvi + 243 pp. (Cloth US$ 24.95 Real Life in Castro's Cuba. CATHERINE MOSES. Wilmington DE: Scholarly Resources, 2000. xi + 184 pp. (Paper US$ 18.95 The Cuban Way: Capitalism, Communism, and Confrontation. ANA JULIA JATAR-HAUSMANN. West Hartford CT: Kumarian Press, 1999. xvii + 161 pp. (Paper US$21.95 Castro and the Cuban Revolution. THOMAS M. LEONARD. Westport CT: Greenwood Press, 1999. xxv + 188 pp. (Cloth US$ 45.00 Cuba has attracted a great deal of attention from both scholarly and popular authors since 1959. The literature that they have produced has generated much heat, but has shed a considerably smaller amount of light. Most accounts have been situated at the polar extremes of ideology, either condemning or celebrating the island's revolutionary experiment and its maximum leader (for the former is often virtually totally collapsed into the personage of Fidel Castro with the same degrees of vociferous, simplistic certitude. However, neither the fulminating diatribes of the anti-Castro Right nor the fulsome paeans of the Euro-American Left have done much justice to making sense of the complex, confounding, and contradictory realities of Cuban society before, during, and after the Revolution. Indeed, contemporary developments have only magnified the distortions rendered by the astigmatic lenses of cold war intellectualism.

  12. Characterization and Operation of Liquid Crystal Adaptive Optics Phoropter

    Energy Technology Data Exchange (ETDEWEB)

    Awwal, A; Bauman, B; Gavel, D; Olivier, S; Jones, S; Hardy, J L; Barnes, T; Werner, J S

    2003-02-05

    Adaptive optics (AO), a mature technology developed for astronomy to compensate for the effects of atmospheric turbulence, can also be used to correct the aberrations of the eye. The classic phoropter is used by ophthalmologists and optometrists to estimate and correct the lower-order aberrations of the eye, defocus and astigmatism, in order to derive a vision correction prescription for their patients. An adaptive optics phoropter measures and corrects the aberrations in the human eye using adaptive optics techniques, which are capable of dealing with both the standard low-order aberrations and higher-order aberrations, including coma and spherical aberration. High-order aberrations have been shown to degrade visual performance for clinical subjects in initial investigations. An adaptive optics phoropter has been designed and constructed based on a Shack-Hartmann sensor to measure the aberrations of the eye, and a liquid crystal spatial light modulator to compensate for them. This system should produce near diffraction-limited optical image quality at the retina, which will enable investigation of the psychophysical limits of human vision. This paper describes the characterization and operation of the AO phoropter with results from human subject testing.

  13. OPTICAL analysis of solar facility heliostats

    Energy Technology Data Exchange (ETDEWEB)

    Igel, E.; Hughes, R.L.

    1977-05-01

    An experimentally verified simple analytical model, based on classical optical aberrations, is derived and predicts the power reception of a central receiver solar facility. A laboratory simulation was made of a typical heliostat, and its images were photographed and measured at several angles of incidence. The analytically predicted image size is in agreement with experiment to within less than 10% over an incident angle range of 60 degrees. Image size for several of the heliostats in the Sandia-ERDA Solar Thermal Test Facility array were calculated throughout a day and compared with ideal images and the size of the receiver. The optical parameters of the system and the motion of the sun were found to severely affect the design and optimization of any solar thermal facility. This analysis shows that it is the aberration astigmatism which governs the solar image size at the receiver. Image growth is minimal when heliostats are used at small angles of incidence, which usually corresponds to a limited operating time of two to three hours. However, image size is markedly increased at large angles of incidence. The principal result is that the predominant sources of image enlargement are identified and measures for minimizing these enlargements are presented. This analysis considers only the idealized optical problem and does not consider the pragmatic errors associated with implementation and operation of a heliostat array.

  14. Late onset post-LASIK keratectasia with reversal and stabilization after use of latanoprost and corneal collagen cross-linking

    Directory of Open Access Journals (Sweden)

    Tor Paaske Utheim

    2012-01-01

    Full Text Available We report a case of late onset keratectasia after laser in situ keratomileusis (LASIK and its quick reversal and stabilization after use of latanoprost and riboflavin/ultraviolet-A corneal collagen cross-linking (CXL. A 39-year-old man with normal intraocular pressure developed a rapid deterioration of vision in his left eye 6 years after LASIK-retreatment for high myopic astigmatism. Keratectasia was diagnosed by corneal topography and ultrasound pachymetry. After two months of treatment with latanoprost and a minor intraocular pressure reduction, uncorrected distance visual acuity improved from 20/100 to 20/20 and corneal topography showed reversal of keratectasia. CXL was performed after the reversal to achieve long-term stabilization. At 1, 3, 6, 13 and 39 months followup exams after the CXL, stable vision, refraction, and topography were registered. This case shows that keratectasia may rapidly occur several years after LASIK and that a quick reversal and stabilization may be achieved by use of latanoprost followed by CXL.

  15. [Excessive medical problems in the treatment of common eye diseases in children].

    Science.gov (United States)

    Wang, L H

    2016-08-01

    In this paper, some typical excessive medical problems in the treatment of common eye diseases in children were listed as follows: unnecessary examinations carried out for children with little or no corresponding complaints; prescription for spectacles for physiological hyperopia or astigmatism in children; over-diagnosis, over-or nonstandard-treatment for amblyopia; strabismus surgeries performed in children with esotropia but without full optical correction of hyperopic refractive error, in children with monocular strabismus and amblyopia but without standard cover therapy, in children with intermittent exotropia but without optical correction of myopic refractive errors and myopic anisometropia, and without evaluation of their fusional control ability; exaggerated the harm of myopia and the curative effect of Orthokeratology contact lenses without considering the patient's compliance; cataract surgery performed in infants with partial opacity of the lens that has little effect on the vision. Every ophthalmologist should work based on evidence-based preferred practice pattern, professional standards and expert consensus to promote the standardization of the diagnosis and treatment of children's common eye diseases in China. (Chin J Ophthalmol, 2016, 52: 561-564). PMID:27562274

  16. Large Binocular Telescope Interferometer Adaptive Optics: On-sky performance and lessons learned

    CERN Document Server

    Bailey, Vanessa P; Puglisi, Alfio T; Esposito, Simone; Vaitheeswaran, Vidhya; Skemer, Andrew J; Defrere, Denis; Vaz, Amali; Leisenring, Jarron M

    2014-01-01

    The Large Binocular Telescope Interferometer is a high contrast imager and interferometer that sits at the combined bent Gregorian focus of the LBT's dual 8.4~m apertures. The interferometric science drivers dictate 0.1'' resolution with $10^3-10^4$ contrast at $10~\\mu m$, while the $4~\\mu m$ imaging science drivers require even greater contrasts, but at scales $>$0.2''. In imaging mode, LBTI's Adaptive Optics system is already delivering $4~\\mu m$ contrast of $10^4-10^5$ at $0.3''-0.75''$ in good conditions. Even in poor seeing, it can deliver up to 90\\% Strehl Ratio at this wavelength. However, the performance could be further improved by mitigating Non-Common Path Aberrations. Any NCPA remedy must be feasible using only the current hardware: the science camera, the wavefront sensor, and the adaptive secondary mirror. In preliminary testing, we have implemented an ``eye doctor'' grid search approach for astigmatism and trefoil, achieving 5\\% improvement in Strehl Ratio at $4~\\mu m$, with future plans to tes...

  17. [Design of Dual-Beam Spectrometer in Spectrophotometer for Colorimetry].

    Science.gov (United States)

    Liu, Yi-xuan; Yan, Chang-xiang

    2015-07-01

    Spectrophotometers for colorimetry are usually composed of two independent and identical spectrometers. In order to reduce the volume of spectrophotometer for colorimetry, a design method of double-beam spectrometer is put forward. A traditional spectrometer is modified so that a new spectrometer can realize the function of double spectrometers, which is especially suitable for portable instruments. One slit is replaced by the double-slit, than two beams of spectrum can be detected. The working principle and design requirement of double-beam spectrometer are described. A spectrometer of portable spectrophotometer is designed by this method. A toroidal imaging mirror is used for the Czerny-Turner double-beam spectrometer in this paper, which can better correct astigmatism, and prevent the dual-beam spectral crosstalk. The results demonstrate that the double-beam spectrometer designed by this method meets the design specifications, with the spectral resolution less than 10 nm, the spectral length of 9.12 mm, and the volume of 57 mm x 54 mm x 23 mm, and without the dual-beam spectral overlap in the detector either. Comparing with a traditional spectrophotometer, the modified spectrophotometer uses a set of double-beam spectrometer instead of two sets of spectrometers, which can greatly reduce the volume. This design method can be specially applied in portable spectrophotometers, also can be widely applied in other double-beam spectrophotometers, which offers a new idea for the design of dual-beam spectrophotometers. PMID:26717779

  18. Multi-pass gas cell designed for VOCs analysis by infrared spectroscopy system

    Science.gov (United States)

    Wang, Junbo; Wang, Xin; Wei, Haoyun

    2015-10-01

    Volatile Organic Compounds (VOCs) emitted from chemical, petrochemical, and other industries are the most common air pollutants leading to various environmental hazards. Regulations to control the VOCs emissions have been more and more important in China, which requires specific VOCs measurement systems to take measures. Multi-components analysis system, with an infrared spectrometer, a gas handling module and a multi-pass gas cell, is one of the most effective air pollution monitoring facilities. In the VOCs analysis system, the optical multi-pass cell is required to heat to higher than 150 degree Celsius to prevent the condensation of the component gas. Besides that, the gas cell needs to be designed to have an optical path length that matches the detection sensitivity requirement with a compact geometry. In this article, a multi-pass White cell was designed for the high temperature absorption measurements in a specified geometry requirement. The Aberration theory is used to establish the model to accurately calculate the astigmatism for the reflector system. In consideration of getting the optimum output energy, the dimensions of cell geometry, object mirrors and field mirror are optimized by the ray-tracing visible simulation. Then finite element analysis was used to calculate the thermal analysis for the structure of the external and internal elements for high stability. According to the simulation, the cell designed in this paper has an optical path length of 10 meters with an internal volume of 3 liters, and has good stability between room temperature to 227 degree Celsius.

  19. Generation and application of the soft X-ray laser beam based on capillary discharge

    International Nuclear Information System (INIS)

    In this work we report on the generation and characterization of a focused soft X-ray laser beam with intensity and energy density that exceed the threshold for the ablation of PMMA. We demonstrate a feasibility of direct ablation of holes using a focused soft X-ray laser beam. Ablated craters in PMMA/gold-covered-PMMA samples were obtained by focusing the soft X-ray Ar8+ laser pulses generated by a 46.9 nm tabletop capillary-discharge-pumped driver with a spherical Si/Sc multilayer mirror. It was found that the focused beam is capable by one shot to ablate PMMA, even if the focus is significantly influenced by astigmatism. Analysis of the laser beam footprints by atomic force microscope shows that ablated holes have periodic surface structure (similarly as Laser-Induced Periodic Surface Structure) with period ∼2,8 μm and with peak-to-peak depth ∼5-10 nm.

  20. Small Incision Lenticule Extraction (SMILE) vs. Femtosecond Laser in Situ Keratomileusis (FS-LASIK) for treatment of myopia

    DEFF Research Database (Denmark)

    Hansen, Rasmus Søgaard; Justesen, Birgitte; Lyhne, Niels;

    ), and safety at 1 day, 1 week and 3 months after SMILE and FS-LASIK for all degrees of myopia, but in particular high myopia. Setting: Department of Ophthalmology, Odense University Hospital, Odense, Denmark Methods: Retrospective study of results after SMILE and FS-LASIK for all degrees of myopia. All...... treatments were performed at the Department of Ophthalmology, Odense University Hospital from April 2011 to December 2013. Inclusion criteria: CDVA ≤ 0.10 (logMAR) before surgery and no other ocular conditions than myopia with or without astigmatism of maximum 3 D. Exclusion criteria: Eyes having undergone...... diameter ranged from 6.00 to 6.60 mm, whereas the FS-LASIK optical zone ranged from 6.00 to 6.25 mm. Maximum attempted spherical correction was -10.00 D in both procedures. Clinical examinations were performed pre-operatively and at 1 day, 1 week and 3 months post-operatively. For analysis, high myopia...

  1. Small Incision Lenticule Extraction (SMILE) vs. Femtosecond Laser in Situ Keratomileusis (FS-LASIK) for treatment of myopia

    DEFF Research Database (Denmark)

    Hansen, Rasmus Søgaard; Lyhne, Niels; Justesen, Birgitte;

    and CDVA), and safety at 1 day, 1 week and 3 months after SMILE and FS-LASIK for all degrees of myopia, but in particular high myopia. Setting: Department of Ophthalmology, Odense University Hospital, Odense, Denmark Methods: - 157 ord Retrospective study of results after SMILE and FS-LASIK for all degrees...... of myopia. All treatments were performed at the Department of Ophthalmology, Odense University Hospital from April 2011 to December 2013. Inclusion criteria: CDVA ≤ 0.10 (logMAR) before surgery and no other ocular conditions than myopia with or without astigmatism of maximum 3 D. Exclusion criteria: Eyes...... myopia was defined as a spherical equivalent (SE) refraction of -6.00 D or worse. Results: - 186 ord In total, 612 SMILE eyes and 306 FS-LASIK eyes were included and analyzed. Before surgery, 88% of SMILE eyes and 85% of FS-LASIK eyes were highly myopic and SE refraction averaged -7.26±1.75 D (range: -0...

  2. Factors Influencing Intraocular Pressure Changes after Laser In Situ Keratomileusis with Flaps Created by Femtosecond Laser or Mechanical Microkeratome.

    Directory of Open Access Journals (Sweden)

    Meng-Yin Lin

    Full Text Available The aim of this study is to describe factors that influence the measured intraocular pressure (IOP change and to develop a predictive model after myopic laser in situ keratomileusis (LASIK with a femtosecond (FS laser or a microkeratome (MK. We retrospectively reviewed preoperative, intraoperative, and 12-month postoperative medical records in 2485 eyes of 1309 patients who underwent LASIK with an FS laser or an MK for myopia and myopic astigmatism. Data were extracted, such as preoperative age, sex, IOP, manifest spherical equivalent (MSE, central corneal keratometry (CCK, central corneal thickness (CCT, and intended flap thickness and postoperative IOP (postIOP at 1, 6 and 12 months. Linear mixed model (LMM and multivariate linear regression (MLR method were used for data analysis. In both models, the preoperative CCT and ablation depth had significant effects on predicting IOP changes in the FS and MK groups. The intended flap thickness was a significant predictor only in the FS laser group (P < .0001 in both models. In the FS group, LMM and MLR could respectively explain 47.00% and 18.91% of the variation of postoperative IOP underestimation (R2 = 0.47 and R(2 = 0.1891. In the MK group, LMM and MLR could explain 37.79% and 19.13% of the variation of IOP underestimation (R(2 = 0.3779 and 0.1913 respectively. The best-fit model for prediction of IOP changes was the LMM in LASIK with an FS laser.

  3. The effect of retinal defocus on golf putting.

    Science.gov (United States)

    Bulson, Ryan C; Ciuffreda, Kenneth J; Hung, George K

    2008-07-01

    The purpose of this experiment was to determine the effect of type and magnitude of retinal defocus on golf putting accuracy, and on the related eye, head, and putter movements. Eye, head, and putter movements were assessed objectively along with putting accuracy in 16 young adult, visually normal inexperienced golfers during a fixed 9-foot golf putt. Convex spherical (+0.50 D, +1.00 D, +1.50 D, +2.00 D, +10.00 D) and cylindrical (+1.00 D x 90, +2.00 D x 90) lenses were added binocularly to create various types and magnitudes of retinal defocus. Putting accuracy was significantly reduced only under the highest spherical blur lens condition (+10.00 D). No significant differences were found between any other lens conditions for eye, head or putter movements. Small amounts of spherical and astigmatic retinal defocus had a minimal impact on overall golf putting performance, except for putting accuracy under the highest blur condition. This is consistent with the findings of related studies. For a fixed putting distance, factors other than quality of the retinal image, such as blur adaptation and motor learning, appeared to be sufficient to maintain a high level of motor performance. PMID:18565089

  4. Sparse aperture mask wavefront sensor testbed results

    Science.gov (United States)

    Subedi, Hari; Zimmerman, Neil T.; Kasdin, N. Jeremy; Riggs, A. J. E.

    2016-07-01

    Coronagraphic exoplanet detection at very high contrast requires the estimation and control of low-order wave- front aberrations. At Princeton High Contrast Imaging Lab (PHCIL), we are working on a new technique that integrates a sparse-aperture mask (SAM) with a shaped pupil coronagraph (SPC) to make precise estimates of these low-order aberrations. We collect the starlight rejected from the coronagraphic image plane and interfere it using a sparse aperture mask (SAM) at the relay pupil to estimate the low-order aberrations. In our previous work we numerically demonstrated the efficacy of the technique, and proposed a method to sense and control these differential aberrations in broadband light. We also presented early testbed results in which the SAM was used to sense pointing errors. In this paper, we will briefly overview the SAM wavefront sensor technique, explain the design of the completed testbed, and report the experimental estimation results of the dominant low-order aberrations such as tip/tit, astigmatism and focus.

  5. Why are freeform telescopes less alignment sensitive than a traditional unobscured TMA?

    Science.gov (United States)

    Thompson, Kevin P.; Schiesser, Eric; Rolland, Jannick P.

    2015-10-01

    As freeform optical systems emerge as interesting and innovative solutions for imaging in 3D packages there is an assumption they are going to be more sensitive particularly at assembly. While it is true that the clocking of the component becomes a relatively weak new tolerance, for the most effective new class of freeform systems the alignment sensitivity is actually lower in most cases than for a comparable traditional unobscured three mirror anastigmatic (TMA) telescope. Traditional unobscured TMA telescopes, whose designs emerged in the mid-70s and which begin to appear as hardware in the literature in the early 90s, are based on using increasingly offset apertures with otherwise coaxial rotationally symmetric mirrors. The mirrors (typically 3 to correct spherical, coma, and astigmatism) have evolved to contain more high order terms as the designs are pushed to more compact and wider field packages - the NIRCAM camera for the JWST is an excellent example of this [1]. As the higher order terms are added, the mirrors become increasingly sensitive to decenters and tilts. An emerging class of freeform telescopes that provide wider field of view and/or faster f/numbers than the traditional TMA are based on a strategy where the surface shape remains a low order Zernike-type surface even in compact, unobscured packages. This optical design strategy results in an optical form that is not only higher performance but simultaneously less sensitive to alignment.

  6. [Soft contactlenses in general practice (author's transl)].

    Science.gov (United States)

    Miller, B

    1975-07-01

    In contrast to the hard lenses the soft lens has enough permeability for oxygen and water-soluble substances, whereas high molecular substances, bacteria and virus cannot penetrate the soft lenses, so long as their surfaces are intact. The two principal production methods, the spin cast method and the lathe-turned method are compared. The duration of wearing of the soft lens depends on the deposits of proteins from the tears on the surface of the lens and the desinfection method. The daily boiling of the lenses shortens their useful life, while chemical desinfection causes besides bacteriolysis, damage of the corneal cell protein. The new cleaners on the base of proteolytic plant enzymes promise good results. For the optical correction of astigmatism with more than 1 cyl, soft lenses with conic outer surface are used or combinations of a soft and a hard lens (Duosystem). The therapeutic use of soft lenses has as aim: protection of the cornea against mechanical irritation, release of pain, protracted administration output of medicaments. Further indications for use: aseptic corneal inflammation and corneal defects.

  7. Beam shaping characteristics of an unstable-waveguide hybrid resonator.

    Science.gov (United States)

    Xiao, Longsheng; Qin, Yingxiong; Tang, Xiahui; Wan, Chenhao; Li, Gen; Zhong, Lijing

    2014-04-01

    The unstable-waveguide hybrid resonator emits a rectangular, simple astigmatic beam with a large number of high-spatial-frequency oscillations in the unstable direction. To equalize the beam quality, in this paper, a beam shaping system with a spatial filter for the hybrid resonator was investigated by numerical simulation and experimental method. The high-frequency components and fundamental mode of the output beam of the hybrid resonator in the unstable direction are separated by a focus lens. The high-frequency components of the beam are eliminated by the following spatial filter. A nearly Gaussian-shaped beam with approximately equal beam propagation factor M² in the two orthogonal directions was obtained. The effects of the width of the spatial filter on the beam quality, power loss, and intensity distribution of the shaped beam were investigated. The M² factor in the unstable direction is changed from 1.6 to 1.1 by optimum design. The power loss is only 9.5%. The simulation results are in good agreement with the experimental results.

  8. Method and apparatus for ophthalmological surgery

    International Nuclear Information System (INIS)

    The invention contemplates use of a scanning laser characterized by ultraviolet radiation to achieve controlled ablative photodecomposition of one or more selected regions of a cornea. Irradiated flux density and exposure time are so controlled as to achieve desired depth of the ablation, which is a local sculpturing step, and the scanning action is coordinated to achieve desired ultimate surface change in the cornea. The scanning may be so controlled as to change the front surface of the cornea from a greater to a lesser spherical curvature, or from a lesser to a greater spherical curvature, thus effecting reduction in a myopic or in a hyperopic condition, without resort to a contact or other corrective auxiliary lens technique, in that the cornea becomes the corrective lens. The scanning may also be so controlled as to reduce astigmatism and to perform the precise incisions of a keratotomy. Still further, the scanning may be so controlled as to excise corneal tissue uniformly over a precisely controlled area of the cornea for precision accommodation of a corneal transplant

  9. A practical guide to handling laser diode beams

    CERN Document Server

    Sun, Haiyin

    2015-01-01

    This book offers the reader a practical guide to the control and characterization of laser diode beams.  Laser diodes are the most widely used lasers, accounting for 50% of the global laser market.  Correct handling of laser diode beams is the key to the successful use of laser diodes, and this requires an in-depth understanding of their unique properties. Following a short introduction to the working principles of laser diodes, the book describes the basics of laser diode beams and beam propagation, including Zemax modeling of a Gaussian beam propagating through a lens.  The core of the book is concerned with laser diode beam manipulations: collimating and focusing, circularization and astigmatism correction, coupling into a single mode optical fiber, diffractive optics and beam shaping, and manipulation of multi transverse mode beams.  The final chapter of the book covers beam characterization methods, describing the measurement of spatial and spectral properties, including wavelength and linewidth meas...

  10. NO and NO2 emission ratios measured from in-use commercial aircraft during taxi and takeoff.

    Science.gov (United States)

    Herndon, Scott C; Shorter, Joanne H; Zahniser, Mark S; Nelson, David D; Jayne, John; Brown, Robert C; Miake-Lye, Richard C; Waitz, Ian; Silva, Phillip; Lanni, Thomas; Demerjian, Ken; Kolb, Charles E

    2004-11-15

    In August 2001, the Aerodyne Mobile Laboratory simultaneously measured NO, NO2, and CO2 within 350 m of a taxiway and 550 m of a runway at John F. Kennedy Airport. The meteorological conditions were such that taxi and takeoff plumes from individual aircraft were clearly resolved against background levels. NO and NO2 concentrations were measured with 1 s time resolution using a dual tunable infrared laser differential absorption spectroscopy instrument, utilizing an astigmatic multipass Herriott cell. The CO2 measurements were also obtained at 1 s time resolution using a commercial non-dispersive infrared absorption instrument. Plumes were measured from over 30 individual planes, ranging from turbo props to jumbo jets. NOx emission indices were determined by examining the correlation between NOx (NO + NO2) and CO2 during the plume measurements. Several aircraft tail numbers were unambiguously identified, allowing those specific airframe/engine combinations to be determined. The resulting NOx emission indices from positively identified in-service operating airplanes are compared with the published International Civil Aviation Organization engine certification test database collected on new engines in certification test cells.

  11. Design of a Compact, Bimorph Deformable Mirror-Based Adaptive Optics Scanning Laser Ophthalmoscope.

    Science.gov (United States)

    He, Yi; Deng, Guohua; Wei, Ling; Li, Xiqi; Yang, Jinsheng; Shi, Guohua; Zhang, Yudong

    2016-01-01

    We have designed, constructed and tested an adaptive optics scanning laser ophthalmoscope (AOSLO) using a bimorph mirror. The simulated AOSLO system achieves diffraction-limited criterion through all the raster scanning fields (6.4 mm pupil, 3° × 3° on pupil). The bimorph mirror-based AOSLO corrected ocular aberrations in model eyes to less than 0.1 μm RMS wavefront error with a closed-loop bandwidth of a few Hz. Facilitated with a bimorph mirror at a stroke of ±15 μm with 35 elements and an aperture of 20 mm, the new AOSLO system has a size only half that of the first-generation AOSLO system. The significant increase in stroke allows for large ocular aberrations such as defocus in the range of ±600° and astigmatism in the range of ±200°, thereby fully exploiting the AO correcting capabilities for diseased human eyes in the future.

  12. Optical characterization of solar furnace system using fixed geometry nonimaging focusing heliostat and secondary parabolic concentrator

    Science.gov (United States)

    Chong, Kok-Keong; Lim, Chuan-Yang; Keh, Wee-Liang; Fan, Jian-Hau; Rahman, Faidz Abdul

    2011-10-01

    A novel solar furnace system has been proposed to be consisted of a Nonimaging Focusing Heliostat and a smaller parabolic concentrator. In this configuration, the primary heliostat consists of 11×11 array of concave mirrors with a total reflective area of 121 m2 while the secondary parabolic concentrator has a focal length of 30 cm. To simplify the design and reduce the cost, fixed geometry of the primary heliostat is adopted to omit the requirement of continuous astigmatic correction throughout a year. The overall performance of the novel solar furnace configuration can be optimized if the heliostat's spinning-axis is fixed in the orientation dependent on the latitude angle so that the annual variation of incidence angle is the least, which ranges from 33° to 57°. Case study of the novel solar furnace system has been performed with the use of ray-tracing method to simulate solar flux distribution profile for two different target distances, i.e. 50 m and 100 m. The simulated results have revealed that the maximum solar concentration ratio ranges from 20,530 suns to 26,074 suns for the target distance of 50 m, and ranges from 40,366 suns to 43,297 suns for the target distance of 100 m.

  13. Optical characterization of nonimaging focusing heliostat

    Science.gov (United States)

    Chong, Kok-Keong

    2011-10-01

    A novel nonimaging focusing heliostat consisted of many small movable element mirrors that can be dynamically maneuvered in a line-tilting manner has been proposed for the astigmatic correction in a wide range of incident angle from 0° to 70°. In this article, a comprehensive optical characterization of the new heliostat with total reflective area of 25 m2 and slant range of 25 m using ray-tracing method has been carried to analyze the performance including solar concentration ratio, ratio of aberrated-to-ideal image area, intercept efficiency and spillage loss. The optical characterization of the heliostat in the application of solar power tower system has embraced the cases of 1×1, 9×9, 11×11, 13×13, 15×15, 17×17 and 19×19 arrays of concave mirrors provided that the total reflective area remains the same. The simulated result has shown that the maximum solar concentration ratio at a high incident angle of 65° can be improved from 1.76 suns (single mirror) to 104.99 suns (9×9 mirrors), to 155.93 suns (11×11 mirrors), to 210.44 suns (13×13 mirrors), to 246.21 suns (15×15 mirrors), to 259.80 suns (17×17 mirrors) and to 264.73 suns (19×19 mirrors).

  14. Preliminary results of a high-resolution refractometer using the Hartmann-Shack wave-front sensor: part I

    Directory of Open Access Journals (Sweden)

    Carvalho Luis Alberto

    2003-01-01

    Full Text Available In this project we are developing an instrument for measuring the wave-front aberrations of the human eye using the Hartmann-Shack sensor. A laser source is directed towards the eye and its diffuse reflection at the retina generates an approximately spherical wave-front inside the eye. This wave-front travels through the different components of the eye (vitreous humor, lens, aqueous humor, and cornea and then leaves the eye carrying information about the aberrations caused by these components. Outside the eye there is an optical system composed of an array of microlenses and a CCD camera. The wave-front hits the microlens array and forms a pattern of spots at the CCD plane. Image processing algorithms detect the center of mass of each spot and this information is used to calculate the exact wave-front surface using least squares approximation by Zernike polynomials. We describe here the details of the first phase of this project, i. e., the construction of the first generation of prototype instruments and preliminary results for an artificial eye calibrated with different ametropias, i. e., myopia, hyperopia and astigmatism.

  15. Adaptive optics ophthalmologic systems using dual deformable mirrors

    Energy Technology Data Exchange (ETDEWEB)

    Jones, S; Olivier, S; Chen, D; Sadda, S; Joeres, S; Zawadzki, R; Werner, J S; Miller, D

    2007-02-01

    Adaptive Optics (AO) have been increasingly combined with a variety of ophthalmic instruments over the last decade to provide cellular-level, in-vivo images of the eye. The use of MEMS deformable mirrors in these instruments has recently been demonstrated to reduce system size and cost while improving performance. However, currently available MEMS mirrors lack the required range of motion for correcting large ocular aberrations, such as defocus and astigmatism. In order to address this problem, we have developed an AO system architecture that uses two deformable mirrors, in a woofer/tweeter arrangement, with a bimorph mirror as the woofer and a MEMS mirror as the tweeter. This setup provides several advantages, including extended aberration correction range, due to the large stroke of the bimorph mirror, high order aberration correction using the MEMS mirror, and additionally, the ability to ''focus'' through the retina. This AO system architecture is currently being used in four instruments, including an Optical Coherence Tomography (OCT) system and a retinal flood-illuminated imaging system at the UC Davis Medical Center, a Scanning Laser Ophthalmoscope (SLO) at the Doheny Eye Institute, and an OCT system at Indiana University. The design, operation and evaluation of this type of AO system architecture will be presented.

  16. Effects of short-term wear of silicone hydrogel contact lenses on refractive behaviour

    Directory of Open Access Journals (Sweden)

    W. D. H. Gillan

    2012-12-01

    Full Text Available Contact lens wear is known to induce change in both the cornea and refractive state. Often a shift towards increased myopia is noted. Historically investigations into the effects of contact lenses onrefractive state have often been incomplete in terms of statistical analysis whereby nearest equivalent sphere is used or the spherical, cylindrical and axis components are analyzed in isolation. The aim ofthis study was to investigate the short-term effects of silicone hydrogel contact lenses on refractive behaviour. Seven volunteers agreed to wear a silicone hydrogel lens on one eye for a period of thirty minutes. Prior to lens wear, after ten minutes of lens wear and after thirty minutes of lens wear 50 autorefractor measurements were taken of refractive state from each subject. Data were analyzed using multivariate statistical methods. Scatter plots and other multivariate statistics are used to show how lens wear influences refractive behaviour. The results of this study show that silicone hydrogel contact lenses do influence refractive behaviour in both a spherical as well as an antistigmatic (astigmatism fashion. (S Afr Optom 2012 71(2 78-85 

  17. Transconjunctival sutureless intrascleral intraocular lens fixation using intrascleral tunnels guided with catheter and 30-gauge needles.

    Science.gov (United States)

    Takayama, Kohei; Akimoto, Masayuki; Taguchi, Hogara; Nakagawa, Satoko; Hiroi, Kano

    2015-11-01

    We invented a new method for fixing an intraocular lens (IOL) in the scleral tunnel without using a wide conjunctival incision. Modified bent catheter needles were used to penetrate the IOL haptics through the sclerotomy sites. The IOL haptics were inserted into 30-guage (G) scleral tunnels guided by double 30-G needles piercing the sclera. All procedures were performed through the conjunctiva without wide incision. The procedure does not require special forceps, trocars or fibrin glue, only catheter and 30-G needles. The aid of an assistant was not required to support the IOL haptic. The procedures were easily learnt based on our previous method. As with other transconjunctival sutureless surgeries, patients feel less discomfort and the conjunctiva can be conserved for future glaucoma surgery. Complications included two cases of vitreous haemorrhage (16.7%), and one case each of postoperative hypotony, and iris capture (8.3%). Astigmatism induced by intraocular aberration was the same as we reported previously. Our method for fixing the IOL into the scleral tunnel is innovative, less expensive, less invasive and quick. This modified method is a good alternative for fixing IOL haptics into the sclera.

  18. Aberration correction in double-pass amplifiers through the use of phase-conjugate mirrors and/or adaptive optics

    Science.gov (United States)

    Jackel, Steven M.; Moshe, Inon; Lavi, Raphael

    2001-04-01

    Corrrection of birefringence induced effects (depolarization and bipolar focusing) was achieved in double-pass amplifiers using a Faraday rotator placed between the laser rod and the retroreflecting optic. A necessary condition was that each ray in the beam retraced its path through the amplifying medium. Retrace was limited by imperfect conjugate-beam fidelity and by nonreciprocal double-pass indices of refraction. We compare various retroreflectors: stimulated Brillouin scatter phase-conjugate-mirrors (PCMs), PCMs with relay lenses to image the rod principal plane onto the PCM entrance aperture (IPCMs), IPCMs with external, adaptively-adjusted, astigmatism-correcting cylindrical doublets, and all adaptive optics imaging variable-radius-mirrors (IVRMs). Results with flashlamp pumped, Nd:Cr:GSGG double-pass amplifiers show that average output power increased fivefold with a Faraday rotator plus complete nonlinear optics retroreflector package (IPCM+cylindrical zoom), and that this represents an 80% increase over the power achieved using just a PCM. Far better results are, however, achieved with an IVRM.

  19. Long term refractive and structural outcome following laser treatment for zone 1 aggressive posterior retinopathy of prematurity

    Directory of Open Access Journals (Sweden)

    Parag K Shah

    2014-01-01

    Full Text Available Aim: To report the long term refractive, visual and structural outcome post-laser for zone 1 aggressive posterior retinopathy of prematurity (AP-ROP. Materials and Methods: A retrospective analysis was performed of refractive status of premature infants with zone 1 AP-ROP who underwent laser photocoagulation from 2002 to 2007 and followed up till 2013. Once the disease regressed, children were followed up six monthly with detailed examination regarding fixation pattern, ocular motility, nystagmus, detailed anterior segment and posterior segment examination, and refractive status including best corrected visual acuity. Results: Forty-eight eyes of 25 infants were included in the study. Average follow-up was 6.91 years (range, 3.8-9.5years after laser treatment. Astigmatism was noted in 43 out of 48 eyes (89.6%. Two eyes had simple myopia whereas three eyes had no refractive error. Conclusion: After successful laser treatment for zone 1 retinopathy of prematurity (ROP, 94% of our cases developed refractive error. Although most had a favorable anatomical and visual outcome, long-term follow-up even after a successful laser treatment in ROP was necessary.

  20. A diffraction-limited scanning system providing broad spectral range for laser scanning microscopy

    Science.gov (United States)

    Yu, Jiun-Yann; Liao, Chien-Sheng; Zhuo, Zong-Yan; Huang, Chen-Han; Chui, Hsiang-Chen; Chu, Shi-Wei

    2009-11-01

    Diversified research interests in scanning laser microscopy nowadays require broadband capability of the optical system. Although an all-mirror-based optical design with a suitable metallic coating is appropriate for broad-spectrum applications from ultraviolet to terahertz, most researchers prefer lens-based scanning systems despite the drawbacks of a limited spectral range, ghost reflection, and chromatic aberration. One of the main concerns is that the geometrical aberration induced by off-axis incidence on spherical mirrors significantly deteriorates image resolution. Here, we demonstrate a novel geometrical design of a spherical-mirror-based scanning system in which off-axis aberrations, both astigmatism and coma, are compensated to reach diffraction-limited performance. We have numerically simulated and experimentally verified that this scanning system meets the Marechà l condition and provides high Strehl ratio within a 3°×3° scanning area. Moreover, we demonstrate second-harmonic-generation imaging from starch with our new design. A greatly improved resolution compared to the conventional mirror-based system is confirmed. This scanning system will be ideal for high-resolution linear/nonlinear laser scanning microscopy, ophthalmoscopic applications, and precision fabrications.

  1. Thin-disk laser multi-pass amplifier

    CERN Document Server

    Schuhmann, K; Graf, T; Hänsch, T W; Kirch, K; Kottmann, F; Pohl, R; Taqqu, D; Voß, A; Weichelt, B; Antognini, A

    2015-01-01

    In the context of the Lamb shift measurement in muonic helium we developed a thin-disk laser composed of a Q-switched oscillator and a multi-pass amplifier delivering pulses of 150 mJ at a pulse duration of 100 ns. Its peculiar requirements are stochastic trigger and short delay time (< 500 ns) between trigger and optical output. The concept of the thin-disk laser allows for energy and power scaling with high efficiency. However the single pass gain is small (about 1.2). Hence a multi-pass scheme with precise mode matching for large beam waists (w = 2 mm) is required. Instead of using the standard 4f design, we have developed a multi-pass amplifier with a beam propagation insensitive to thermal lens effects and misalignments. The beam propagation is equivalent to multiple roundtrips in an optically stable resonator. To support the propagation we used an array of 2 x 8 individually adjustable plane mirrors. Astigmatism has been minimized by a compact mirror placement. Precise alignment of the kinematic arra...

  2. OPHTHALMOLOGIC ABNORMALITIES IN CHILDREN WITH IMPAIRED HEARING

    Directory of Open Access Journals (Sweden)

    Inderjit

    2014-02-01

    Full Text Available AIM: To determine the nature of ophthalmologic abnormalities in severe and profound grades of hearing impaired children and to treat visual impairment if any at the earliest . MATERIAL AND METHODS: Study was conducted on100 children in the age group of 5 - 14 years with severe and profound hearing loss visiting outpatient department of Ram Lal Eye and ENT hospital Govt. Medical College Amritsar and subjected to detailed ophthalmological examination. RESULTS: 100 children in the age group 5 - 14 years with hearing impairment were enrolled for t he study , 68 had profound and 32 had severe hearing loss . Visual disorders were found to be as high as 71%. Highest percentage was seen in children aged 7 years. Majority of them (50% had refractive error. Out of these 50 children , 28(56% had myopia , 10 (20% hypermetropia and 12(24% had astigmatism . The other ophthalmic abnormalities in our study were conjunctivitis 14(19.71% , fundus abnormalities and squint 11(15.49% , blepharitis 5 (7.04% , vitamin A deficiency 6 (8.04% , amblyopia 8 (11.26% , pupil disorder 3 (4.22% , cataract 3 (4.22% and heterochromia iridis 7 (9.85%. CONCLUSION : The high prevalence of ophthalmic abnormalities in deaf children mandate screening them for possible ophthalmic abnormalities. Early diagnosis and correction of visual d isturbances would go a long way in social and professional performance of these children.

  3. Higher order aberrations in amblyopic children and their role in refractory amblyopia

    Directory of Open Access Journals (Sweden)

    Arnaldo Dias-Santos

    2014-12-01

    Full Text Available Objective: Some studies have hypothesized that an unfavourable higher order aberrometric profile could act as an amblyogenic mechanism and may be responsible for some amblyopic cases that are refractory to conventional treatment or cases of “idiopathic” amblyopia. This study compared the aberrometric profile in amblyopic children to that of children with normal visual development and compared the aberrometric profile in corrected amblyopic eyes and refractory amblyopic eyes with that of healthy eyes. Methods: Cross-sectional study with three groups of children – the CA group (22 eyes of 11 children with unilateral corrected amblyopia, the RA group (24 eyes of 13 children with unilateral refractory amblyopia and the C group (28 eyes of 14 children with normal visual development. Higher order aberrations were evaluated using an OPD-Scan III (NIDEK. Comparisons of the aberrometric profile were made between these groups as well as between the amblyopic and healthy eyes within the CA and RA groups. Results: Higher order aberrations with greater impact in visual quality were not significantly higher in the CA and RA groups when compared with the C group. Moreover, there were no statistically significant differences in the higher order aberrometric profile between the amblyopic and healthy eyes within the CA and RA groups. Conclusions: Contrary to lower order aberrations (e.g., myopia, hyperopia, primary astigmatism, higher order aberrations do not seem to be involved in the etiopathogenesis of amblyopia. Therefore, these are likely not the cause of most cases of refractory amblyopia.

  4. Microfocusing at the PG1 beamline at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Dziarzhytski, Siarhei; Gerasimova, Natalia; Goderich, Rene; Mey, Tobias; Reininger, Ruben; Rübhausen, Michael; Siewert, Frank; Weigelt, Holger; Brenner, Günter

    2016-01-01

    The Kirkpatrick–Baez (KB) refocusing mirror system installed at the PG1 branch of the plane-grating monochromator beamline at the soft X-ray/XUV free-electron laser in Hamburg (FLASH) is designed to provide tight aberration-free focusing down to 4 µm x 6 µm full width at half-maximum (FWHM) on the sample. Such a focal spot size is mandatory to achieve ultimate resolution and to guarantee best performance of the vacuum-ultraviolet (VUV) off-axis parabolic double-monochromator Raman spectrometer permanently installed at the PG1 beamline as an experimental end-station. The vertical beam size on the sample of the Raman spectrometer, which operates without entrance slit, defines and limits the energy resolution of the instrument which has an unprecedented design value of 2 meV for photon energies below 70 eV and about 15 meV for higher energies up to 200 eV. In order to reach the designed focal spot size of 4 µm FWHM (vertically) and to hold the highest spectrometer resolution, special fully motorized in-vacuum manipulators for the KB mirror holders have been developed and the optics have been aligned employing wavefront-sensing techniques as well as ablative imprints analysis. Aberrations like astigmatism were minimized. In this article the design and layout of the KB mirror manipulators, the alignment procedure as well as microfocus optimization results are presented.

  5. How surfactants influence evaporation-driven flows

    Science.gov (United States)

    Liepelt, Robert; Marin, Alvaro; Rossi, Massimiliano; Kähler, Christian J.

    2014-11-01

    Capillary flows appear spontaneously in sessile evaporating drops and give rise to particle accumulation around the contact lines, commonly known as coffee-stain effect (Deegan et al., Nature, 1997). On the other hand, out-of-equilibrium thermal effects may induce Marangoni flows in the droplet's surface that play an important role in the flow patterns and in the deposits left on the substrate. Some authors have argued that contamination or the presence of surfactants might reduce or eventually totally annul the Marangoni flow (Hu & Larson, J. Phys. Chem. B, 2006). On the contrary, others have shown an enhancement of the reverse surface flow (Sempels et al., Nat. Commun., 2012). In this work, we employ Astigmatic Particle Tracking Velocimetry (APTV) to obtain the 3D3C evaporation-driven flow in both bulk and droplet's surface, using surfactants of different ionic characters and solubility. Our conclusions lead to a complex scenario in which different surfactants and concentrations yield very different surface-flow patterns, which eventually might influence the colloidal deposition patterns.

  6. James Webb Space Telescope Optical Simulation Testbed II. Design of a Three-Lens Anastigmat Telescope Simulator

    CERN Document Server

    Choquet, Élodie; N'Diaye, Mamadou; Perrin, Marshall D; Soummer, Rémi

    2014-01-01

    The James Webb Space Telescope (JWST) Optical Simulation Testbed (JOST) is a tabletop experiment designed to reproduce the main aspects of wavefront sensing and control (WFSC) for JWST. To replicate the key optical physics of JWST's three-mirror anastigmat (TMA) design at optical wavelengths we have developed a three-lens anastigmat optical system. This design uses custom lenses (plano-convex, plano-concave, and bi-convex) with fourth-order aspheric terms on powered surfaces to deliver the equivalent image quality and sampling of JWST NIRCam at the WFSC wavelength (633~nm, versus JWST's 2.12~micron). For active control, in addition to the segmented primary mirror simulator, JOST reproduces the secondary mirror alignment modes with five degrees of freedom. We present the testbed requirements and its optical and optomechanical design. We study the linearity of the main aberration modes (focus, astigmatism, coma) both as a function of field point and level of misalignments of the secondary mirror. We find that t...

  7. New data postprocessing for e-beam projection lithography

    Science.gov (United States)

    Okamoto, Kazuya; Kamijo, Koichi; Kojima, Shinichi; Minami, Hideyuki; Okino, Teruaki

    2001-08-01

    In electron beam projection lithography (EPL), one of the most crucial tasks is to develop a data post-processing system, namely, a specific tool to expose a faithful pattern for every subfield on the wafer based on the pattern layout data. This system includes two basic flows. The 1st flow is common for reticle fabrication, and the 2nd flow is unique for EPL. During the 2nd flow, based on the LSI pattern data, electron optics space-charge effect correction will be automatically and rapidly executed and output to the EPL system in order to adjust parameters such as focus, magnification, rotation and astigmatism. In addition, this system should perform such tasks as segmentations of subfields (including complementary division), arrangement of stripes and reticlets, and alignment mark insertion. For proximity effect correction, we will first use a pattern shape modulation first. Shape modification at stitching boundaries is also investigated. In summary, to achieve conformable EPL delivery to customers, a new data post- processing system is developed in collaboration with some suppliers.

  8. Recurrent duplications of 17q12 associated with variable phenotypes.

    Science.gov (United States)

    Mitchell, Elyse; Douglas, Andrew; Kjaegaard, Susanne; Callewaert, Bert; Vanlander, Arnaud; Janssens, Sandra; Yuen, Amy Lawson; Skinner, Cindy; Failla, Pinella; Alberti, Antonino; Avola, Emanuela; Fichera, Marco; Kibaek, Maria; Digilio, Maria C; Hannibal, Mark C; den Hollander, Nicolette S; Bizzarri, Veronica; Renieri, Alessandra; Mencarelli, Maria Antonietta; Fitzgerald, Tomas; Piazzolla, Serena; van Oudenhove, Elke; Romano, Corrado; Schwartz, Charles; Eichler, Evan E; Slavotinek, Anne; Escobar, Luis; Rajan, Diana; Crolla, John; Carter, Nigel; Hodge, Jennelle C; Mefford, Heather C

    2015-12-01

    The ability to identify the clinical nature of the recurrent duplication of chromosome 17q12 has been limited by its rarity and the diverse range of phenotypes associated with this genomic change. In order to further define the clinical features of affected patients, detailed clinical information was collected in the largest series to date (30 patients and 2 of their siblings) through a multi-institutional collaborative effort. The majority of patients presented with developmental delays varying from mild to severe. Though dysmorphic features were commonly reported, patients do not have consistent and recognizable features. Cardiac, ophthalmologic, growth, behavioral, and other abnormalities were each present in a subset of patients. The newly associated features potentially resulting from 17q12 duplication include height and weight above the 95th percentile, cataracts, microphthalmia, coloboma, astigmatism, tracheomalacia, cutaneous mosaicism, pectus excavatum, scoliosis, hypermobility, hypospadias, diverticulum of Kommerell, pyloric stenosis, and pseudohypoparathryoidism. The majority of duplications were inherited with some carrier parents reporting learning disabilities or microcephaly. We identified additional, potentially contributory copy number changes in a subset of patients, including one patient each with 16p11.2 deletion and 15q13.3 deletion. Our data further define and expand the clinical spectrum associated with duplications of 17q12 and provide support for the role of genomic modifiers contributing to phenotypic variability. PMID:26420380

  9. Analytic PSF Correction for Gravitational Flexion Studies

    CERN Document Server

    Levinson, Rebecca Sobel

    2013-01-01

    Given a galaxy image, one cannot simply measure its flexion. An image's spin one and three shape properties, typically associated with F- and G-flexion, are actually complicated functions of the galaxy's intrinsic shape and the telescope's PSF, in addition to the lensing properties. The same is true for shear. In this work we create a completely analytic mapping from apparent measured galaxy flexions to gravitational flexions by (1) creating simple models for a lensed galaxy and for a PSF whose distortions are dominated by atmospheric smearing and optical aberrations, (2) convolving the two models, and (3) comparing the pre- and post-convolved flexion-like shape variations of the final image. For completeness, we do the same for shear. As expected, telescope astigmatism, coma, and trefoil can corrupt measurements of shear, F- flexion, and G-flexion, especially for small galaxies. We additionally find that PSF size dilutes the flexion signal more rapidly than the shear signal. Moreover, mixing between shears, ...

  10. Optimized SESAMs for kilowatt-level ultrafast lasers.

    Science.gov (United States)

    Diebold, A; Zengerle, T; Alfieri, C G E; Schriber, C; Emaury, F; Mangold, M; Hoffmann, M; Saraceno, C J; Golling, M; Follman, D; Cole, G D; Aspelmeyer, M; Südmeyer, T; Keller, U

    2016-05-16

    We present a thorough investigation of surface deformation and thermal properties of high-damage threshold large-area semiconductor saturable absorber mirrors (SESAMs) designed for kilowatt average power laser oscillators. We compare temperature rise, thermal lensing, and surface deformation of standard SESAM samples and substrate-removed SESAMs contacted using different techniques. We demonstrate that for all cases the thermal effects scale linearly with the absorbed power, but the contacting technique critically affects the strength of the temperature rise and the thermal lens of the SESAMs (i.e. the slope of the linear change). Our best SESAMs are fabricated using a novel substrate-transfer direct bonding technique and show excellent surface flatness (with non-measureable radii of curvature (ROC), compared to astigmatic ROCs of up to 10 m for standard SESAMs), order-of-magnitude improved heat removal, and negligible deformation with absorbed power. This is achieved without altering the saturation behavior or the recovery parameters of the samples. These SESAMs will be a key enabling component for the next generation of kilowatt-level ultrafast oscillators. PMID:27409874

  11. Optical control of the Advanced Technology Solar Telescope.

    Science.gov (United States)

    Upton, Robert

    2006-08-10

    The Advanced Technology Solar Telescope (ATST) is an off-axis Gregorian astronomical telescope design. The ATST is expected to be subject to thermal and gravitational effects that result in misalignments of its mirrors and warping of its primary mirror. These effects require active, closed-loop correction to maintain its as-designed diffraction-limited optical performance. The simulation and modeling of the ATST with a closed-loop correction strategy are presented. The correction strategy is derived from the linear mathematical properties of two Jacobian, or influence, matrices that map the ATST rigid-body (RB) misalignments and primary mirror figure errors to wavefront sensor (WFS) measurements. The two Jacobian matrices also quantify the sensitivities of the ATST to RB and primary mirror figure perturbations. The modeled active correction strategy results in a decrease of the rms wavefront error averaged over the field of view (FOV) from 500 to 19 nm, subject to 10 nm rms WFS noise. This result is obtained utilizing nine WFSs distributed in the FOV with a 300 nm rms astigmatism figure error on the primary mirror. Correction of the ATST RB perturbations is demonstrated for an optimum subset of three WFSs with corrections improving the ATST rms wavefront error from 340 to 17.8 nm. In addition to the active correction of the ATST, an analytically robust sensitivity analysis that can be generally extended to a wider class of optical systems is presented. PMID:16926876

  12. Impact of capillarity forces on the steady-state self-organization in the thin chromium film on glass under laser irradiation

    International Nuclear Information System (INIS)

    Metal films on transparent substrates are widely used for mask production in lithography, and lasers are frequently applied for their patterning. Steady self-organization of a chromium thin film on the glass substrate to parallel metal lines under irradiation with partially overlapping highly astigmatic nanosecond laser pulses above the ablation threshold has been observed. Transformations in a chromium film were investigated experimentally and numerically. The theoretical model of the steady self-organization is presented and discussed. It was demonstrated that the capillarity convection force was responsible for the transformation process in the molten metal. It was shown that the thermo-capillarity (Marangoni) shear stress and the stress originating from a variation in the radius of curvature along the structure were equally important in the case of the steady self-organization process. - Highlights: • The model of steady-state self-organization in molten metal was developed. • The Marangoni convection pushes liquid metal from the hotter to cooler area. • The capillarity force pushes liquid metal because of gradient in curvature radius. • Shear stresses of thermal and radius of curvature gradients are equally important

  13. Canopy induced aberration correction in airborne electro-optical imaging systems

    Science.gov (United States)

    Harder, James A.; Sprague, Michaelene W.

    2011-11-01

    An increasing number of electro-optical systems are being used by pilots in tactical aircraft. This means that the afore mentioned systems must operate through the aircrafts canopy, unfortunately the canopy functions as a less than ideal lens element in the electro-optical sensor optical path. The canopy serves first and foremost as an aircraft structural component, considerations like minimizing the drag co-efficient and the ability to survive bird strikes take precedence over achieving optimal optical characteristics. This paper describes how the authors characterized the optical characteristics of an aircraft canopy. Families of modulation transfer functions were generated, for various viewing geometries through the canopy and for various electro-optical system entrance pupil diameters. These functions provided us with the means to significantly reduce the effect of the canopy "lens" on the performance of a representative electro-optical system, using an Astigmatic Corrector Lens. A comparison of the electro-optical system performance with and without correction is also presented.

  14. Active Optics for high contrast imaging:Super smooth off-axis parabolas for ELTs XAO instruments

    Science.gov (United States)

    Hugot, Emmanuel; Laslandes, Marie; Ferrari, Marc; Dohlen, Kjetil; El hadi, Kacem

    2011-09-01

    In the context of direct imaging of exoplanets using XAO, the main limitations in images are due to residual quasi-static speckles induced by atmospheric phase residuals and instrumental static and quasi-static aberrations not corrected by AO: the post-coronagraphic image quality is directly linked to the power spectral density (PSD) of the optical train before the coronagraph. In this context, the potential of Stress Polishing has been demonstrated at LAM after the delivery of the three toric mirrors (TMs) for the VLT-SPHERE instrument. The extreme optical quality of such aspherical optics is obtained thanks to the spherical polishing of warped mirrors using full sized tools, avoiding the generation of high spatial frequency ripples due to classical sub-aperture tool marks. Furthermore, sub-nanometric roughnesses have been obtained thanks to a super smoothing method. Work is ongoing at LAM in order to improve this manufacturing method to cover a wide range of off-axis aspherics, with a reduction of the manufacturing time and cost. Smart warping structures are designed in order to bend the mirrors with a combination of focus, astigmatism and coma. This development will allow the stress polishing of supersmooth OAP for XAO optical relays improving the wavefront quality and in this way the high contrast level of future exoplanet imagers.

  15. Features of propagation of the high-intensity femtosecond laser pulses in magnesium and sodium fluoride crystals

    International Nuclear Information System (INIS)

    The periodic filamentation patterns across and along laser channel tracks, induced by high-intensity femtosecond laser pulses in magnesium and sodium fluoride crystals, have been disclosed. The patterns are rationalized by deterministic vectorial effect, difference in propagations of linearly- and circularly-polarized laser pulses, and appearances of the orbital angular momentum of the light beams due to optical astigmatism. - Highlights: • The periodic pattern of multiple filamentation in the cross-section of the femtosecond laser channel in ionic crystals is shown and explained for the first time. • When the femtosecond laser beam is perpendicular to optical axis of the anisotropic MgF2 crystal, the single filaments have strictly periodic structure due to inducing change of pulse polarization by the crystal. • The lower efficiency of multiphoton ionization and CCs luminescence in the case of irradiation by circularly polarized femtosecond laser pulses of MgF2 take place. • In our paper, it is reported for the first time on twisting of the femtosecond laser beam in ionic crystal that can have useful application

  16. Visual acuity assessment in schoolchildren in the municipality of Herval d’Oeste, Santa Catarina state, Brazil

    Directory of Open Access Journals (Sweden)

    Rafaela Santini de Oliveira

    2013-07-01

    Full Text Available Objectives: To evaluate visual acuity through the application of a screening test; identify the prevalence of low vision; and provide proper management to it. Methods: A cross-sectional and quantitative study in which first-to-fifth grade students of two elementary schools in the municipality of Herval d’Oeste were evaluated in the second half of 2011, by means of a questionnaire with the following variables: gender, age, previous use of glasses, perception of their own vision, and application of the Snellen Test to assess visual acuity (VA. Students presenting VA<0.7 and signs and symptoms of ocular disorders were referred to an ophthalmologist. Results: The sample comprised 318 students: 158 (49.6% males and 160 (50.3% females, between 5 and 15 years old. Thirty of these students showed low visual acuity and were referred to eye care, and 24 children attended ophthalmic examinations - 19 (79.16% needed optical correction. The most prevalent diagnoses were astigmatism, hyperopia, and myopia. Conclusion: The detection of low vision among schoolchildren through screening tests is an important task of health promotion and an effective strategy to prevent visual disorders, which can interfere with intellectual, psychological and social development. The effective implementation of programs and actions to promote health through the integration of health, education and community should be considered.

  17. Outcomes of Sutureless Iris-Claw Lens Implantation

    Science.gov (United States)

    Nowomiejska, Katarzyna; Moneta-Wielgoś, Joanna; Jünemann, Anselm G. M.

    2016-01-01

    Purpose. To evaluate the indications, refraction, and visual and safety outcomes of iris-claw intraocular lens implanted retropupillary with sutureless technique during primary or secondary operation. Methods. Retrospective study of case series. The Haigis formula was used to calculate intraocular lens power. In all cases the wound was closed without suturing. Results. The study comprised 47 eyes. The mean follow-up time was 15.9 months (SD 12.2). The mean preoperative CDVA was 0.25 (SD 0.21). The final mean CDVA was 0.46 (SD 0.27). No hypotony or need for wound suturing was observed postoperatively. Mean postoperative refractive error was −0.27 Dsph (−3.87 Dsph to +2.85 Dsph; median 0.0, SD 1.28). The mean postoperative astigmatism was −1.82 Dcyl (min −0.25, max −5.5; median −1.25, SD 1.07). Postoperative complications were observed in 10 eyes. The most common complication was ovalization of the iris, which was observed in 8 eyes. The mean operation time was 35.9 min (min 11 min, max 79 min; median 34, SD 15.4). Conclusion. Retropupilary iris-claw intraocular lens (IOL) implantation with sutureless wound closing is an easy and fast method, ensuring good refractive outcome and a low risk of complication. The Haigis formula proved to be predictable in postoperative refraction. PMID:27642519

  18. Scleral lens for keratoconus: technology update

    Directory of Open Access Journals (Sweden)

    Rathi VM

    2015-10-01

    Full Text Available Varsha M Rathi,1 Preeji S Mandathara,2 Mukesh Taneja,1 Srikanth Dumpati,1 Virender S Sangwan1 1L V Prasad Eye Institute, Hyderabad, India; 2School of Optometry and Vision Science, University of New South Wales, Kensington, NSW, Australia Abstract: Scleral lenses are large diameter lenses which rest over the sclera, unlike the conventional contact lenses which rest on the cornea. These lenses are fitted to not touch the cornea and there is a space created between the cornea and the lens. These lenses are inserted in the eyes after filling with sterile isotonic fluid. Generally, scleral contact lenses are used for high irregular astigmatism as seen in various corneal ectatic diseases such as keratoconus, pellucid marginal degeneration, or/and as liquid bandage in ocular surface disorders. In this article, we review the new developments, that have taken place over the years, in the field of scleral contact lenses as regard to new designs, materials, manufacturing technologies, and fitting strategies particularly for keratoconus. Keywords: keratoconus, scleral lens, technology update, PROSE

  19. Bifocal contact lenses: History, types, characteristics, and actual state and problems

    Directory of Open Access Journals (Sweden)

    Hiroshi Toshida

    2008-07-01

    Full Text Available Hiroshi Toshida, Kozo Takahashi, Kazushige Sado, Atsushi Kanai, Akira MurakamiDepartment of Ophthalmology, Juntendo University School of Medicine, Tokyo, JapanAbstract: Since people who wear contact lenses (CL often continue using CL even when they develop presbyopia, there are growing expectations for bifocal CL. To understand actual state and problems, history, types, and their characteristics are summarized in this review. Bifocal CL have a long history over 70 years. Recently, bifocal CL have achieved remarkable progress. However, there still is an impression that prescription of bifocal CL is not easy. It should also be remembered that bifocal CL have limits, including limited addition for near vision, as well as the effects of aging and eye diseases in the aged, such as dry eye, astigmatism, cataract, etc. Analysis of the long-term users of bifocal CL among our patients has revealed the disappearance of bifocal CL that achieved unsatisfactory vision and poor contrast compared with those provided by other types of CL. Changing the prescription up to 3 times for lenses of the same brand may be appropriate. Lenses that provide poor contrast sensitivity, suffer from glare, or give unsatisfactory vision have been weeded out. The repeated replacement of products due to the emergence of improved or new products will be guessed.Keywords: bifocal contact lens, presbyopia, accommodation

  20. Keratoconus: current perspectives

    Directory of Open Access Journals (Sweden)

    Vazirani J

    2013-10-01

    Full Text Available Jayesh Vazirani, Sayan BasuCornea and Anterior Segment Services, LV Prasad Eye Institute, Hyderabad, IndiaAbstract: Keratoconus is characterized by progressive corneal protrusion and thinning, leading to irregular astigmatism and impairment in visual function. The etiology and pathogenesis of the condition are not fully understood. However, significant strides have been made in early clinical detection of the disease, as well as towards providing optimal optical and surgical correction for improving the quality of vision in affected patients. The past two decades, in particular, have seen exciting new developments promising to alter the natural history of keratoconus in a favorable way for the first time. This comprehensive review focuses on analyzing the role of advanced imaging techniques in the diagnosis and treatment of keratoconus and evaluating the evidence supporting or refuting the efficacy of therapeutic advances for keratoconus, such as newer contact lens designs, collagen crosslinking, deep anterior lamellar keratoplasty, intracorneal ring segments, photorefractive keratectomy, and phakic intraocular lenses.Keywords: keratoconus, corneal topography, hydrops, collagen cross-linking, keratoplasty, contact lenses

  1. Low-volume, fast response-time hollow silica waveguide gas cells for mid-IR spectroscopy.

    Science.gov (United States)

    Francis, Daniel; Hodgkinson, Jane; Livingstone, Beth; Black, Paul; Tatam, Ralph P

    2016-09-01

    Hollow silica waveguides (HSWs) are used to produce long path length, low-volume gas cells, and are demonstrated with quantum cascade laser spectroscopy. Absorption measurements are made using the intrapulse technique, which allows measurements to be made across a single laser pulse. Simultaneous laser light and gas coupling is achieved through the modification of commercially available gas fittings with low dead volume. Three HSW gas cell configurations with different path lengths and internal diameters are analyzed and compared with a 30 m path length astigmatic Herriott cell. Limit of detection measurements are made for the gas cells using methane at a wavelength 7.82 μm. The lowest limit of detection was provided by HSW with a bore diameter of 1000 μm and a path length of 5 m and was measured to be 0.26 ppm, with a noise equivalent absorbance of 4.1×10-4. The long-term stability of the HSW and Herriott cells is compared through analysis of the Allan-Werle variance of data collected over a 24 h period. The response times of the HSW and Herriott cells are measured to be 0.8 s and 36 s, respectively. PMID:27607251

  2. Spatial shaping for generating arbitrary optical dipole traps for ultracold degenerate gases

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jeffrey G., E-mail: jglee@umd.edu [Joint Quantum Institute, University of Maryland, College Park, Maryland 20742 (United States); Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States); Hill, W. T., E-mail: wth@umd.edu [Joint Quantum Institute, University of Maryland, College Park, Maryland 20742 (United States); Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States); Department of Physics, University of Maryland, College Park, Maryland 20742 (United States)

    2014-10-15

    We present two spatial-shaping approaches – phase and amplitude – for creating two-dimensional optical dipole potentials for ultracold neutral atoms. When combined with an attractive or repulsive Gaussian sheet formed by an astigmatically focused beam, atoms are trapped in three dimensions resulting in planar confinement with an arbitrary network of potentials – a free-space atom chip. The first approach utilizes an adaptation of the generalized phase-contrast technique to convert a phase structure embedded in a beam after traversing a phase mask, to an identical intensity profile in the image plane. Phase masks, and a requisite phase-contrast filter, can be chemically etched into optical material (e.g., fused silica) or implemented with spatial light modulators; etching provides the highest quality while spatial light modulators enable prototyping and realtime structure modification. This approach was demonstrated on an ensemble of thermal atoms. Amplitude shaping is possible when the potential structure is made as an opaque mask in the path of a dipole trap beam, followed by imaging the shadow onto the plane of the atoms. While much more lossy, this very simple and inexpensive approach can produce dipole potentials suitable for containing degenerate gases. High-quality amplitude masks can be produced with standard photolithography techniques. Amplitude shaping was demonstrated on a Bose-Einstein condensate.

  3. Spatial shaping for generating arbitrary optical dipole traps for ultracold degenerate gases

    Science.gov (United States)

    Lee, Jeffrey G.; Hill, W. T.

    2014-10-01

    We present two spatial-shaping approaches - phase and amplitude - for creating two-dimensional optical dipole potentials for ultracold neutral atoms. When combined with an attractive or repulsive Gaussian sheet formed by an astigmatically focused beam, atoms are trapped in three dimensions resulting in planar confinement with an arbitrary network of potentials - a free-space atom chip. The first approach utilizes an adaptation of the generalized phase-contrast technique to convert a phase structure embedded in a beam after traversing a phase mask, to an identical intensity profile in the image plane. Phase masks, and a requisite phase-contrast filter, can be chemically etched into optical material (e.g., fused silica) or implemented with spatial light modulators; etching provides the highest quality while spatial light modulators enable prototyping and realtime structure modification. This approach was demonstrated on an ensemble of thermal atoms. Amplitude shaping is possible when the potential structure is made as an opaque mask in the path of a dipole trap beam, followed by imaging the shadow onto the plane of the atoms. While much more lossy, this very simple and inexpensive approach can produce dipole potentials suitable for containing degenerate gases. High-quality amplitude masks can be produced with standard photolithography techniques. Amplitude shaping was demonstrated on a Bose-Einstein condensate.

  4. Prevalence of Vitamin-A deficiency AND refractive errors in primary school-going children

    Directory of Open Access Journals (Sweden)

    Rupali Darpan Maheshgauri

    2016-03-01

    To assess refractive errors in primary school-going children. To critically analyze the need for supplementation of Vitamin A, to children of low socioeconomic strata. Methods: Students were examined from 2 primary schools. Visual acuity was tested using Snellen's chart, Pictogram and Landolt C chart. Detailed anterior and posterior segment examination using Binocular loop, Ophthalmoscope and Streak retinoscope. RESULTS: Total no of 560 children of age 3 to 13yr were screened from 2 primary schools.Statistically significant difference was found in the age of the study subject and presence of refractive errors. Percentage of students having Refractive error: myopia (29.64% is the major cause of refractive error, followed by astigmatism (4.28% hypermetropia (3.25% and amblyopia (1.25%. Conclusion: It was observed that many children had high refractive error and were undiagnosed. The possible reason could be ignorance on the part of teachers and parents, even when the children have vision related complains. Also the children in the younger age-group lack the acumen to judge whether they can see clearly or not. Prevalence of Vitamin A deficiency appears reduced in urban areas. [Natl J Med Res 2016; 6(1.000: 23-27

  5. Tearing of thin spherical shells adhered to equally curved rigid substrates

    Science.gov (United States)

    McMahan, Connor; Lee, Anna; Marthelot, Joel; Reis, Pedro

    Lasik (Laser-Assisted in Situ Keratomileusis) eye surgery involves the tearing of the corneal epithelium to remodel the corneal stroma for corrections such as myopia, hyperopia and astigmatism. One issue with this procedure is that during the tearing of the corneal epithelium, if the two propagating cracks coalesce, a flap detaches which could cause significant complications in the recovery of the patient. We seek to gain a predictive physical understanding of this process by performing precision desktop experiments on an analogue model system. First, thin spherical shells of nearly uniform thickness are fabricated by the coating of hemispherical molds with a polymer solution, which upon curing yields an elastic and brittle structure. We then create two notches near the equator of the shell and tear a flap by pulling tangentially to the spherical substrate, towards its pole. The resulting fracture paths are characterized by high-resolution 3D digital scanning. Our primary focus is on establishing how the positive Gaussian curvature of the system affects the path of the crack tip. Our results are directly contrasted against previous studies on systems with zero Gaussian curvature, where films were torn from planar and cylindrical substrates.

  6. Data processing for fabrication of GMT primary segments: raw data to final surface maps

    Science.gov (United States)

    Tuell, Michael T.; Hubler, William; Martin, Hubert M.; West, Steven C.; Zhou, Ping

    2014-07-01

    The Giant Magellan Telescope (GMT) primary mirror is a 25 meter f/0.7 surface composed of seven 8.4 meter circular segments, six of which are identical off-axis segments. The fabrication and testing challenges with these severely aspheric segments (about 14 mm of aspheric departure, mostly astigmatism) are well documented. Converting the raw phase data to useful surface maps involves many steps and compensations. They include large corrections for: image distortion from the off-axis null test; misalignment of the null test; departure from the ideal support forces; and temperature gradients in the mirror. The final correction simulates the active-optics correction that will be made at the telescope. Data are collected and phase maps are computed in 4D Technology's 4SightTM software. The data are saved to a .h5 (HDF5) file and imported into MATLAB® for further analysis. A semi-automated data pipeline has been developed to reduce the analysis time as well as reducing the potential for error. As each operation is performed, results and analysis parameters are appended to a data file, so in the end, the history of data processing is embedded in the file. A report and a spreadsheet are automatically generated to display the final statistics as well as how each compensation term varied during the data acquisition. This gives us valuable statistics and provides a quick starting point for investigating atypical results.

  7. Evaluation of corneal biomechanical properties following penetrating keratoplasty using ocular response analyzer

    Directory of Open Access Journals (Sweden)

    Vanathi Murugesan

    2014-01-01

    Full Text Available Purpose: To evaluate corneal biomechanical properties in eyes that has undergone penetrating keratoplasty (PK. Materials and Methods: Retrospective observational study in a tertiary care centre. Data recorded included ocular response analyzer (ORA values of normal and post-keratoplasty eyes [corneal hysteresis (CH, corneal resistance factor (CRF, Goldmann-correlated intraocular pressure (IOPg, and cornea-compensated intraocular pressure (IOPcc], corneal topography, and central corneal thickness (CCT. Wilcoxon signed rank test was used to analyze the difference in ORA parameter between post-PK eyes and normal eyes. Correlation between parameters was evaluated with Spearman′s rho correlation. Results: The ORA study of 100 eyes of 50 normal subjects and 54 post-keratoplasty eyes of 51 patients showed CH of 8.340 ± 1.85 and 9.923 ± 1.558, CRF of 8.846 ± 2.39 and 9.577 ± 1.631 in post-PK eyes and normal eyes, respectively. CH and CRF did not correlate with post-keratoplasty astigmatism (P = 0.311 and 0.276, respectively while a significant correlation was observed with IOPg (P = 0.004 and IOPcc (P < 0.001. Conclusion: Biomechanical profiles were significantly decreased in post-keratoplasty eyes with significant correlation with higher IOP as compared with that in normal eyes.

  8. Keratoconus: Overview and update on treatment

    Directory of Open Access Journals (Sweden)

    Espandar Ladan

    2010-01-01

    Full Text Available Keratoconus is a non-inflammatory, progressive thinning process of the cornea. It is a relatively common disorder of unknown etiology that can involve each layer of the cornea and often leads to high myopia and astigmatism. Computer-assisted corneal topography devices are valuable diagnostic tools for the diagnosis of subclinical keratoconus and for tracking the progression of the disease. The traditional conservative management of keratoconus begins with spectacle correction and contact lenses. Several newer, more invasive, treatments are currently available, especially for contact lens-intolerant patients. Intrastromal corneal ring segments can be used to reshape the abnormal cornea to improve the topographic abnormalities and visual acuity. Phakic intraocular lenses such as iris-fixated, angle-supported, posterior chamber implantable collamer and toric lenses are additional valuable options for the correction of refractive error. Corneal cross-linking is a relatively new method of stiffening the cornea to halt the progression of the disease. The future management of keratoconus will most likely incorporate multiple treatment modalities, both simultaneous and sequential, for the prevention and treatment of this disease.

  9. Theoretical and experimental investigation of design for multioptical-axis freeform progressive addition lenses

    Science.gov (United States)

    Xiang, HuaZhong; Chen, JiaBi; Zhu, TianFen; Wei, YeFei; Fu, DongXiang

    2015-11-01

    A freeform progressive addition lens (PAL) provides a good solution to correct presbyopia and prevent juvenile myopia by distributing pupils' optical powers of distance zone, near zone, and intermediate zone and is more widely adopted in the present optometric study. However, there is still a lack of a single-optical-axis system for the design of a PAL. This paper focuses on the research for an approach for designing a freeform PAL. A multioptical-axis system based on real viewing conditions using the eyes is employed for the representation of the freeform surface. We filled small pupils in the intermediate zone as a progressive corridor and the distance- and near-vision portions were defined as the standard spherical surfaces delimited by quadratic curves. Three freeform PALs with a spherical surface as the front side and a freeform surface as the backside were designed. We demonstrate the fabrication and measurement technologies for the PAL surface using computer numerical control machine tools from Schneider Smart and a Visionix VM-2000 Lens Power Mapper. Surface power and astigmatic values were obtained. Preliminary results showed that the approach for the design and fabrication is helpful to advance the design procedure optimization and mass production of PALs in optometry.

  10. Deep anterior lamellar keratoplasty in keratoconus

    Directory of Open Access Journals (Sweden)

    Nikolić Ljubiša

    2011-01-01

    Full Text Available Introduction. Deep anterior lamellar keratoplasty (DALK is intended for the surgical treatment of corneal pathology without the involvement of the endothelium. Sparing of the healthy host endothelium for lifetime is of utmost importance in young patients. Therefore, keratoconus is among the main indications for DALK. Outline of Cases. Two men, 22 and 28 years of age, underwent DALK for the treatment of progressive keratoconus, with low visual acuity, impossible to be corrected with gas-permeable contact lenses, due to the extreme conical protrusion of the cornea. Baring of Descemet’s membrane was achieved with lamellar dissection and peeling off the stroma. An 8.5 mm graft without the endothelium was sutured into an 8.0 mm bed. Both grafts remained clear and attached, without either ocular surface pathology or problems arising from sutures. The best corrected visual acuity was 20/25 and 20/40, with the astigmatism of 2.5 and 3.0 diopters, respectively. The follow-up was one year. Conclusion. This is the first presentation of DALK in our literature. The restoration of corneal transparency and stability, with sparing of the host endothelium, has put DALK among successful corneal tranplantation procedures. Together with Descemet stripping endothelial keratoplasty, which already accounts for almost a half of all our keratoplasties, it offers an alternative to penetrating keratoplasty.

  11. Influence of Misalignment on High-Order Aberration Correction for Normal Human Eyes

    Institute of Scientific and Technical Information of China (English)

    ZHAO Hao-Xin; XU Bing; XUE Li-Xia; DAI Yun; LIU Qian; RAO Xue-Jun

    2008-01-01

    @@ Although a compensation device can correct aberrations of human eyes, the effect will be degraded by its misalignment, especially for high-order aberration correction. We caJculate the positioning tolerance of correction device for high-order aberrations, and within what degree the correcting effect is better than low-order aberration (defocus and astigmatism) correction. With fixed certain misalignment within the positioning tolerance, we calculate the residual wavefront rms aberration of the first-6 to first-35 terms along with the 3rd-5th terms of aberrations corrected, and the combined first-13 terms of aberrations are also studied under the same quantity of misalignment. However, the correction effect of high-order aberrations does not meliorate along with the increase of the high-order terms under some misalignment, moreover, some simple combined terms correction can achieve similar result as complex combinations. These results suggest that it is unnecessary to correct too much the terms of high-order aberrations which are diffcult to accomplish in practice, and gives confdence to correct high-order aberrations out of the laboratory.

  12. Management of visual disturbances in albinism: a case report

    Directory of Open Access Journals (Sweden)

    Omar Rokiah

    2012-09-01

    Full Text Available Abstract Introduction A number of vision defects have been reported in association with albinism, such as photophobia, nystagmus and astigmatism. In many cases only prescription sunglasses are prescribed. In this report, the effectiveness of low-vision rehabilitation in albinism, which included prescription of multiple visual aids, is discussed. Case presentation We present the case of a 21-year-old Asian woman with albinism and associated vision defects. Her problems were blurring of distant vision, glare and her dissatisfaction with her current auto-focus spectacle-mounted telescope device, which she reported as being heavy as well as cosmetically unacceptable. We describe how low-vision rehabilitation using multiple visual aids, namely spectacles, special iris-tinted contact lenses with clear pupils, and bi-level telemicroscopic apparatus devices improved her quality of life. Subsequent to rehabilitation our patient is happier and continues to use the visual aids. Conclusions Contact lenses with a special iris tint and clear pupil area are useful aids to reduce the glare experienced by albinos. Bi-level telemicroscopic apparatus telemicroscopes fitted onto our patient’s prescription spectacles were cosmetically acceptable and able to improve her distance vision. As a result these low-vision rehabilitation approaches improved the quality of life of our albino patient.

  13. Seven year follow-up after advanced surface ablation with excimer laser for treatment of myopia: Long-term outcomes of cooling PRK and LASEK

    DEFF Research Database (Denmark)

    Hansen, Rasmus Søgaard; Lyhne, Niels; Grauslund, Jakob;

    Purpose: To evaluate and compare refractive predictability, uncorrected and corrected distance visual acuity (UDVA and CDVA), corneal haze, corneal densitometry and patient satisfaction up to 7 years after Photorefractive Keratectomy with cooling (cPRK) and Laser-Assisted Sub-epithelial Keratectomy......, no cPRK eyes, and 2 LASEK eyes (3.6%) had lost 2 or more lines of CDVA. At final follow-up the mean corneal densitometry was 12.31±0.80 in cPRK eyes and 12.30±0.84 in LASEK eyes (P=0.74), and trace haze was found in 4 cPRK eyes (6%) and 6 LASEK eyes (11%) (P=0.51). Ninetyfive percent of all patients...... were satisfied or very satisfied with the surgery 5 to 7 years after surgery. Conclusions: Both cPRK and LASEK seemed safe up to 7 years after surgery for treatment of myopia and low degrees of astigmatism. Results were comparable concerning refractive predictability, visual acuity, corneal haze...

  14. Individual Differences in Scotopic Visual Acuity and Contrast Sensitivity: Genetic and Non-Genetic Influences.

    Science.gov (United States)

    Bartholomew, Alex J; Lad, Eleonora M; Cao, Dingcai; Bach, Michael; Cirulli, Elizabeth T

    2016-01-01

    Despite the large amount of variation found in the night (scotopic) vision capabilities of healthy volunteers, little effort has been made to characterize this variation and factors, genetic and non-genetic, that influence it. In the largest population of healthy observers measured for scotopic visual acuity (VA) and contrast sensitivity (CS) to date, we quantified the effect of a range of variables on visual performance. We found that young volunteers with excellent photopic vision exhibit great variation in their scotopic VA and CS, and this variation is reliable from one testing session to the next. We additionally identified that factors such as Circadian preference, iris color, astigmatism, depression, sex and education have no significant impact on scotopic visual function. We confirmed previous work showing that the amount of time spent on the vision test influences performance and that laser eye surgery results in worse scotopic vision. We also showed a significant effect of intelligence and photopic visual performance on scotopic VA and CS, but all of these variables collectively explain obvious non-genetic factors suggests a strong genetic component. Our preliminary genome-wide association study (GWAS) of 106 participants ruled out any common genetic variants of very large effect and paves the way for future, larger genetic studies of scotopic vision. PMID:26886100

  15. Individual Differences in Scotopic Visual Acuity and Contrast Sensitivity: Genetic and Non-Genetic Influences.

    Directory of Open Access Journals (Sweden)

    Alex J Bartholomew

    Full Text Available Despite the large amount of variation found in the night (scotopic vision capabilities of healthy volunteers, little effort has been made to characterize this variation and factors, genetic and non-genetic, that influence it. In the largest population of healthy observers measured for scotopic visual acuity (VA and contrast sensitivity (CS to date, we quantified the effect of a range of variables on visual performance. We found that young volunteers with excellent photopic vision exhibit great variation in their scotopic VA and CS, and this variation is reliable from one testing session to the next. We additionally identified that factors such as Circadian preference, iris color, astigmatism, depression, sex and education have no significant impact on scotopic visual function. We confirmed previous work showing that the amount of time spent on the vision test influences performance and that laser eye surgery results in worse scotopic vision. We also showed a significant effect of intelligence and photopic visual performance on scotopic VA and CS, but all of these variables collectively explain <30% of the variation in scotopic vision. The wide variation seen in young healthy volunteers with excellent photopic vision, the high test-retest agreement, and the vast majority of the variation in scotopic vision remaining unexplained by obvious non-genetic factors suggests a strong genetic component. Our preliminary genome-wide association study (GWAS of 106 participants ruled out any common genetic variants of very large effect and paves the way for future, larger genetic studies of scotopic vision.

  16. Autokeratomileusis Laser

    Science.gov (United States)

    Kern, Seymour P.

    1987-03-01

    Refractive defects such as myopia, hyperopia, and astigmatism may be corrected by laser milling of the cornea. An apparatus combining automatic refraction/keratometry and an excimer type laser for precision reshaping of corneal surfaces has been developed for testing. When electronically linked to a refractometer or keratometer or holographic imaging device, the laser is capable of rapidly milling or ablating corneal surfaces to preselected dioptric power shapes without the surgical errors characteristic of radial keratotomy, cryokeratomileusis or epikeratophakia. The excimer laser simultaneously generates a synthetic Bowman's like layer or corneal condensate which appears to support re-epithelialization of the corneal surface. An electronic feedback arrangement between the measuring instrument and the laser enables real time control of the ablative milling process for precise refractive changes in the low to very high dioptric ranges. One of numerous options is the use of a rotating aperture wheel with reflective portions providing rapid alternate ablation/measurement interfaced to both laser and measurement instrumentation. The need for the eye to be fixated is eliminated or minimized. In addition to reshaping corneal surfaces, the laser milling apparatus may also be used in the process of milling both synthetic and natural corneal inlays for lamellar transplants.

  17. Structured light-matter interactions in optical nanostructures (Presentation Recording)

    Science.gov (United States)

    Litchinitser, Natalia M.; Sun, Jingbo; Shalaev, Mikhail I.; Xu, Tianboyu; Xu, Yun; Pandey, Apra

    2015-09-01

    We show that unique optical properties of metamaterials open unlimited prospects to "engineer" light itself. For example, we demonstrate a novel way of complex light manipulation in few-mode optical fibers using metamaterials highlighting how unique properties of metamaterials, namely the ability to manipulate both electric and magnetic field components, open new degrees of freedom in engineering complex polarization states of light. We discuss several approaches to ultra-compact structured light generation, including a nanoscale beam converter based on an ultra-compact array of nano-waveguides with a circular graded distribution of channel diameters that coverts a conventional laser beam into a vortex with configurable orbital angular momentum and a novel, miniaturized astigmatic optical element based on a single biaxial hyperbolic metamaterial that enables the conversion of Hermite-Gaussian beams into vortex beams carrying an orbital angular momentum and vice versa. Such beam converters is likely to enable a new generation of on-chip or all-fiber structured light applications. We also present our initial theoretical studies predicting that vortex-based nonlinear optical processes, such as second harmonic generation or parametric amplification that rely on phase matching, will also be strongly modified in negative index materials. These studies may find applications for multidimensional information encoding, secure communications, and quantum cryptography as both spin and orbital angular momentum could be used to encode information; dispersion engineering for spontaneous parametric down-conversion; and on-chip optoelectronic signal processing.

  18. Thermal stability test and analysis of a 20-actuator bimorph deformable mirror

    Institute of Scientific and Technical Information of China (English)

    Ning Yu; Zhou Hong; Yu Hao; Rao Chang-Hui; Jiang Wen-Han

    2009-01-01

    One of the important characteristic of adaptive mirrors is the thermal stability of surface flatness. In this paper, the thermal stability from 13℃ to 25℃ of a 20-actuator bimorph deformable mirror is tested by a Shack-Hartmann wavefront sensor. Experimental results show that, the surface P-V of bimorph increases nearly linearly with ambient temperature. The ratio is 0.11 μm/℃ and the major component of surface displacement is defocused, compared with which, astigmatism, coma and spherical aberration contribute very small. Besides, a finite element model is built up to analyse the influence of thickness, thermal expansion coefficient and Young's modulus of materials on thermal stability. Calculated results show that bimorph has the best thermal stability when the materials have the same thermal expansion coefficient. And when the thickness ratio of glass to PZT is 3 and Young's modulus ratio is approximately 0.4, the surface instability behaviour of the bimorph manifests itself most severely.

  19. Deep stroma investigation by confocal microscopy

    Science.gov (United States)

    Rossi, Francesca; Tatini, Francesca; Pini, Roberto; Valente, Paola; Ardia, Roberta; Buzzonetti, Luca; Canovetti, Annalisa; Malandrini, Alex; Lenzetti, Ivo; Menabuoni, Luca

    2015-03-01

    Laser assisted keratoplasty is nowadays largely used to perform minimally invasive surgery and partial thickness keratoplasty [1-3]. The use of the femtosecond laser enables to perform a customized surgery, solving the specific problem of the single patient, designing new graft profiles and partial thickness keratoplasty (PTK). The common characteristics of the PTKs and that make them eligible respect to the standard penetrating keratoplasty, are: the preservation of eyeball integrity, a reduced risk of graft rejection, a controlled postoperative astigmatism. On the other hand, the optimal surgical results after these PTKs are related to a correct comprehension of the deep stroma layers morphology, which can help in the identification of the correct cleavage plane during surgeries. In the last years some studies were published, giving new insights about the posterior stroma morphology in adult subjects [4,5]. In this work we present a study performed on two groups of tissues: one group is from 20 adult subjects aged 59 +/- 18 y.o., and the other group is from 15 young subjects, aged 12+/-5 y.o.. The samples were from tissues not suitable for transplant in patients. Confocal microscopy and Environmental Scanning Electron Microscopy (ESEM) were used for the analysis of the deep stroma. The preliminary results of this analysis show the main differences in between young and adult tissues, enabling to improve the knowledge of the morphology and of the biomechanical properties of human cornea, in order to improve the surgical results in partial thickness keratoplasty.

  20. Vision, eye disease, and art: 2015 Keeler Lecture.

    Science.gov (United States)

    Marmor, M F

    2016-02-01

    The purpose of this study was to examine normal vision and eye disease in relation to art. Ophthalmology cannot explain art, but vision is a tool for artists and its normal and abnormal characteristics may influence what an artist can do. The retina codes for contrast, and the impact of this is evident throughout art history from Asian brush painting, to Renaissance chiaroscuro, to Op Art. Art exists, and can portray day or night, only because of the way retina adjusts to light. Color processing is complex, but artists have exploited it to create shimmer (Seurat, Op Art), or to disconnect color from form (fauvists, expressionists, Andy Warhol). It is hazardous to diagnose eye disease from an artist's work, because artists have license to create as they wish. El Greco was not astigmatic; Monet was not myopic; Turner did not have cataracts. But when eye disease is documented, the effects can be analyzed. Color-blind artists limit their palette to ambers and blues, and avoid greens. Dense brown cataracts destroy color distinctions, and Monet's late canvases (before surgery) showed strange and intense uses of color. Degas had failing vision for 40 years, and his pastels grew coarser and coarser. He may have continued working because his blurred vision smoothed over the rough work. This paper can barely touch upon the complexity of either vision or art. However, it demonstrates some ways in which understanding vision and eye disease give insight into art, and thereby an appreciation of both art and ophthalmology. PMID:26563659

  1. Refractive ocular conditions and reasons for spectacles renewal in a resource-limited economy

    Directory of Open Access Journals (Sweden)

    Folorunso Francisca N

    2010-05-01

    Full Text Available Abstract Background Although a leading cause of visual impairment and a treatable cause of blindness globally, the pattern of refractive errors in many populations is unknown. This study determined the pattern of refractive ocular conditions, reasons for spectacles renewal and the effect of correction on refractive errors in a resource-limited community. Methods A retrospective review of case records of 1,413 consecutive patients seen in a private optometry practice, Nigeria between January 2006 and July 2007. Results A total number of 1,216 (86.1% patients comprising of (486, 40% males and (730, 60% females with a mean age of 41.02 years SD 14.19 were analyzed. The age distribution peaked at peri-adolescent and the middle age years. The main ocular complaints were spectacles loss and discomfort (412, 33.9%, blurred near vision (399, 32.8% and asthenopia (255, 20.9%. The mean duration of ocular symptoms before consultation was 2.05 years SD 1.92. The most common refractive errors include presbyopia (431, 35.3%, hyperopic astigmatism (240, 19.7% and presbyopia with hyperopia (276, 22.7%. Only (59, 4.9% had myopia. Following correction, there were reductions in magnitudes of the blind (VA Conclusions Adequate correction of refractive errors reduces visual impairment and avoidable blindness and to achieve optimal control of refractive errors in the community, services should be targeted at individuals in the peri-adolescent and the middle age years.

  2. Soft x-ray backlighting of cryogenic implosions using a narrowband crystal imaging system (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Stoeckl, C., E-mail: csto@lle.rochester.edu; Bedzyk, M.; Brent, G.; Epstein, R.; Fiksel, G.; Guy, D.; Goncharov, V. N.; Hu, S. X.; Ingraham, S.; Jacobs-Perkins, D. W.; Jungquist, R. K.; Marshall, F. J.; Mileham, C.; Nilson, P. M.; Sangster, T. C.; Shoup, M. J.; Theobald, W. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)

    2014-11-15

    A high-performance cryogenic DT inertial confinement fusion implosion experiment is an especially challenging backlighting configuration because of the high self-emission of the core at stagnation and the low opacity of the DT shell. High-energy petawatt lasers such as OMEGA EP promise significantly improved backlighting capabilities by generating high x-ray intensities and short emission times. A narrowband x-ray imager with an astigmatism-corrected bent quartz crystal for the Si He{sub α} line at ∼1.86 keV was developed to record backlit images of cryogenic direct-drive implosions. A time-gated recording system minimized the self-emission of the imploding target. A fast target-insertion system capable of moving the backlighter target ∼7 cm in ∼100 ms was developed to avoid interference with the cryogenic shroud system. With backlighter laser energies of ∼1.25 kJ at a 10-ps pulse duration, the radiographic images show a high signal-to-background ratio of >100:1 and a spatial resolution of the order of 10 μm. The backlit images can be used to assess the symmetry of the implosions close to stagnation and the mix of ablator material into the dense shell.

  3. Effect of refractive error on temperament and character properties

    Institute of Scientific and Technical Information of China (English)

    Emine; Kalkan; Akcay; Fatih; Canan; Huseyin; Simavli; Derya; Dal; Hacer; Yalniz; Nagihan; Ugurlu; Omer; Gecici; Nurullah; Cagil

    2015-01-01

    AIM: To determine the effect of refractive error on temperament and character properties using Cloninger’s psychobiological model of personality.METHODS: Using the Temperament and Character Inventory(TCI), the temperament and character profiles of 41 participants with refractive errors(17 with myopia,12 with hyperopia, and 12 with myopic astigmatism) were compared to those of 30 healthy control participants.Here, temperament comprised the traits of novelty seeking, harm-avoidance, and reward dependence, while character comprised traits of self-directedness,cooperativeness, and self-transcendence.RESULTS: Participants with refractive error showed significantly lower scores on purposefulness,cooperativeness, empathy, helpfulness, and compassion(P <0.05, P <0.01, P <0.05, P <0.05, and P <0.01,respectively).CONCLUSION: Refractive error might have a negative influence on some character traits, and different types of refractive error might have different temperament and character properties. These personality traits may be implicated in the onset and/or perpetuation of refractive errors and may be a productive focus for psychotherapy.

  4. A Comparison of Clinical Outcomes of Dislocated Intraocular Lens Fixation between In Situ Refixation and Conventional Exchange Technique Combined with Vitrectomy

    Science.gov (United States)

    Eum, Sun Jung; Kim, Myung Jun; Kim, Hong Kyun

    2016-01-01

    Purpose. To evaluate surgical efficacy of in situ refixation technique for dislocated posterior chamber intraocular lens (PCIOL). Methods. This was a single-center retrospective case series. 34 patients (34 eyes) who underwent sclera fixation for dislocated IOLs combined with vitrectomy were studied. Of 34 eyes, 17 eyes underwent IOL exchange and the other 17 eyes underwent in situ refixation. Results. Mean follow-up period was 6 months. Mean logMAR best corrected visual acuity (BCVA) was not significantly different between the groups 6 months after surgery (0.10 ± 0.03 in the IOL exchange group and 0.10 ± 0.05 in the refixation group; p = 0.065). Surgically induced astigmatism (SIA) was significantly lower in the refixation group (0.79 ± 0.41) than in the IOL exchange group (1.29 ± 0.46) (p = 0.004) at 3 months, which persisted to 6 months (1.13 ± 0.18 in the IOL exchange group and 0.74 ± 0.11 in the refixation group; p = 0.006). Postoperative complications occurred in 3 eyes in the IOL exchange group (17.6%) and 2 eyes in the refixation group (11.8%). However, all of the patients were well managed without additional surgery. Conclusion. The in situ refixation technique should be preferentially considered if surgery is indicated since it seemed to produce a sustained less SIA compared to IOL exchange. PMID:27119019

  5. A Comparison of Clinical Outcomes of Dislocated Intraocular Lens Fixation between In Situ Refixation and Conventional Exchange Technique Combined with Vitrectomy

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    Sun Jung Eum

    2016-01-01

    Full Text Available Purpose. To evaluate surgical efficacy of in situ refixation technique for dislocated posterior chamber intraocular lens (PCIOL. Methods. This was a single-center retrospective case series. 34 patients (34 eyes who underwent sclera fixation for dislocated IOLs combined with vitrectomy were studied. Of 34 eyes, 17 eyes underwent IOL exchange and the other 17 eyes underwent in situ refixation. Results. Mean follow-up period was 6 months. Mean logMAR best corrected visual acuity (BCVA was not significantly different between the groups 6 months after surgery (0.10±0.03 in the IOL exchange group and 0.10±0.05 in the refixation group; p=0.065. Surgically induced astigmatism (SIA was significantly lower in the refixation group (0.79±0.41 than in the IOL exchange group (1.29±0.46 (p=0.004 at 3 months, which persisted to 6 months (1.13±0.18 in the IOL exchange group and 0.74±0.11 in the refixation group; p=0.006. Postoperative complications occurred in 3 eyes in the IOL exchange group (17.6% and 2 eyes in the refixation group (11.8%. However, all of the patients were well managed without additional surgery. Conclusion. The in situ refixation technique should be preferentially considered if surgery is indicated since it seemed to produce a sustained less SIA compared to IOL exchange.

  6. Aspherical Lens Design Using Genetic Algorithm for Reducing Aberrations in Multifocal Artificial Intraocular Lens

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    Chih-Ta Yen

    2015-09-01

    Full Text Available A complex intraocular lens (IOL design involving numerous uncertain variables is proposed. We integrated a genetic algorithm (GA with the commercial optical design software of (CODE V to design a multifocal IOL for the human eye. We mainly used an aspherical lens in the initial state to the crystalline type; therefore, we used the internal human eye model in the software. The proposed optimized algorithm employs a GA method for optimally simulating the focusing function of the human eye; in this method, the thickness and curvature of the anterior lens and the posterior part of the IOL were varied. A comparison of the proposed GA-designed IOLs and those designed using a CODE V built-in optimal algorithm for 550 degrees myopia and 175 degrees astigmatism conditions of the human eye for pupil size 6 mm showed that the proposed IOL design improved the spot size of root mean square (RMS, tangential coma (TCO and modulation transfer function (MTF at a spatial frequency of 30 with a pupil size of 6 mm by approximately 17%, 43% and 35%, respectively. However, the worst performance of spherical aberration (SA was lower than 46%, because the optical design involves a tradeoff between all aberrations. Compared with the traditional CODE V built-in optimal scheme, the proposed IOL design can efficiently improve the critical parameters, namely TCO, RMS, and MTF.

  7. Intraocular lens iris fixation. Clinical and macular OCT outcomes

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    Garcia-Rojas Leonardo

    2012-10-01

    Full Text Available Abstract Background To assess the efficacy, clinical outcomes, visual acuity (VA, incidence of adverse effects, and complications of peripheral iris fixation of 3-piece acrylic IOLs in eyes lacking capsular support. Thirteen patients who underwent implantation and peripheral iris fixation of a 3-piece foldable acrylic PC IOL for aphakia in the absence of capsular support were followed after surgery. Clinical outcomes and macular SD-OCT (Cirrus OCT; Carl Zeiss Meditec, Germany were analyzed. Findings The final CDVA was 20/40 or better in 8 eyes (62%, 20/60 or better in 12 eyes (92%, and one case of 20/80 due to corneal astigmatism and mild persistent edema. No intraoperative complications were reported. There were seven cases of medically controlled ocular hypertension after surgery due to the presence of viscoelastic in the AC. There were no cases of cystoid macular edema, chronic iridocyclitis, IOL subluxation, pigment dispersion, or glaucoma. Macular edema did not develop in any case by means of SD-OCT. Conclusions We think that this technique for iris suture fixation provides safe and effective results. Patients had substantial improvements in UDVA and CDVA. This surgical strategy may be individualized however; age, cornea status, angle structures, iris anatomy, and glaucoma are important considerations in selecting candidates for an appropriate IOL fixation method.

  8. Visual and Refractive Outcomes of a Toric Presbyopia-Correcting Intraocular Lens

    Science.gov (United States)

    Epitropoulos, Alice T.

    2016-01-01

    Purpose. To evaluate outcomes in astigmatic patients implanted with the Trulign (Bausch + Lomb) toric presbyopia-correcting intraocular lens (IOL) during cataract surgery in a clinical practice setting. Methods. Retrospective study in 40 eyes (31 patients) that underwent cataract extraction and IOL implantation in a procedure using intraoperative wavefront aberrometry guidance (ORA system). Endpoints included uncorrected visual acuity (VA), reduction in refractive cylinder, accuracy to target, axis orientation, and safety. Results. At postoperative month 1, refractive cylinder was ≤0.50 D in 97.5% of eyes (≤1.00 D in 100%), uncorrected distance VA was 20/25 or better in 95%, uncorrected intermediate VA was 20/25 or better in 95%, and uncorrected near VA was 20/40 (J3 equivalent) or better in 92.5%. Manifest refraction spherical equivalent was within 1.00 D of target in 95% of eyes and within 0.50 D in 82.5%. Lens rotation was <5° and best-corrected VA was 20/25 or better in all eyes. Conclusion. The IOL effectively reduced refractive cylinder and provided excellent uncorrected distance and intermediate vision and functional near vision. Refractive predictability and rotational stability were exceptional. Implantation of this toric presbyopia-correcting IOL using ORA intraoperative aberrometry provides excellent refractive and visual outcomes in a standard of care setting. PMID:26885382

  9. Clinical Trial of Manual Small Incision Surgery and Standard Extracapsular Surgery

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    Parikshit Gogate

    2003-01-01

    Full Text Available Introduction. Manual small incision cataract surgery (MSICS is used increasingly for cataract extraction and intraocular lens implantation. It is thought that the small wound heals faster than a conventional incision, leading to less astigmatism and a better uncorrected visual acuity. This is important as many patients do not wear or cannot afford spectacles after surgery, which means that their uncorrected visual acuity is what they rely on to carry out their every day functions. Often this is less than 6/18 on the Snellen’s chart, which would fall below the WHO ‘good outcome’ category for post-operative visual impairment. A post-operative vision of 6/18 or better without spectacles is a goal which appears to be within the reach of small incision techniques for cataract surgery. However, there are concerns that the method used to remove the nucleus in MSICS may be more traumatic to the corneal endothelium than conventional ECCE surgery.

  10. Excimer Laser Phototherapeutic Keratectomy for the Treatment of Clinically Presumed Fungal Keratitis

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    Liang-Mao Li

    2014-01-01

    Full Text Available This retrospective study was to evaluate treatment outcomes of excimer laser phototherapeutic keratectomy (PTK for clinically presumed fungal keratitis. Forty-seven eyes of 47 consecutive patients underwent manual superficial debridement and PTK. All corneal lesions were located in the anterior stroma and were resistant to medication therapy for at least one week. Data were collected by a retrospective chart review with at least six months of follow-up data available. After PTK, infected corneal lesions were completely removed and the clinical symptoms resolved in 41 cases (87.2%. The mean ablation depth was 114.39±45.51 μm and diameter of ablation was 4.06±1.07 mm. The mean time for healing of the epithelial defect was 8.8±5.6 days. Thirty-four eyes (82.9% showed an improvement in best spectacle-corrected visual acuity of two or more lines. PTK complications included mild to moderate corneal haze, hyperopic shift, irregular astigmatism, and thinning cornea. Six eyes (12.8% still showed progressed infection, and conjunctival flap covering, amniotic membrane transplantation, or penetrating keratoplasty were given. PTK is a valuable therapeutic alternative for superficial infectious keratitis. It can effectively eradicate lesions, hasten reepithelialization, and restore and preserve useful visual function. However, the selection of surgery candidates should be conducted carefully.

  11. Space and time resolving spectrograph for fusion plasma diagnostics

    International Nuclear Information System (INIS)

    This paper discusses construction of an EUV (60-350 angstrom) space and time resolving, grazing incidence spectrograph (STRS). The simultaneous spectral coverage of the instrument ranges from 20 to 60 angstrom, depending on the wavelength region. The spectral resolution is about 1 angstrom. The spectral resolution, accomplished by using the pinhole camera effect and the inherent astigmatism of a concave grating in grazing incidence, is about 2 m, with a total field of view of 60 cm at a distance of 2 cm from the plasma. The detector consists of a 75 mm MCP image intensifier optically coupled to three CCD area array detectors. Time resolution of up to 2 ms is achieved with high speed read-out electronics. A PDP 11.73 minicomputer controls the spectrograph and collects and reduces 3.0 MB of data per shot. The complete design of the STRS and the results of initial tests of the detector system, spectrograph, and data handling software are presented

  12. Time-resolving multispatial grazing incidence spectrograph for plasma fusion diagnostics

    International Nuclear Information System (INIS)

    A grazing incidence spectrograph which operates in the EUV (40 to 350 A) that has multispectral, temporal, and spatial resolving capabilities is being constructed for plasma fusion diagnostics. The spectrograph achieves a simultaneous spectral coverage of 20 and 60 A when centered on 40 and 350 A, respectively, with ∼ 1-A resolution. The detector consists of an image intensifier fiber optically coupled to 3 area array detectors (CCDS), which can be read out in 5 ms, thereby determining the time resolution of the instrument. The spatial resolution is accomplished by using the astigmatism inherent to a concave grating in grazing incidence, coupled with the pinhole camera effect produced by an entrance slit of limited height. The spectrograph can view ∼ 54 cm of plasma which is 2 m away from the entrance slit with 4- and 8-cm resolution at 350 and 40 A, respectively. The authors will present the results of a feasibility study, the spectrograph design, and the results of the data reduction and interpretation codes which are under development

  13. Accounting for the phase, spatial frequency and orientation demands of the task improves metrics based on the visual Strehl ratio.

    Science.gov (United States)

    Young, Laura K; Love, Gordon D; Smithson, Hannah E

    2013-09-20

    Advances in ophthalmic instrumentation have allowed high order aberrations to be measured in vivo. These measurements describe the distortions to a plane wavefront entering the eye, but not the effect they have on visual performance. One metric for predicting visual performance from a wavefront measurement uses the visual Strehl ratio, calculated in the optical transfer function (OTF) domain (VSOTF) (Thibos et al., 2004). We considered how well such a metric captures empirical measurements of the effects of defocus, coma and secondary astigmatism on letter identification and on reading. We show that predictions using the visual Strehl ratio can be significantly improved by weighting the OTF by the spatial frequency band that mediates letter identification and further improved by considering the orientation of phase and contrast changes imposed by the aberration. We additionally showed that these altered metrics compare well to a cross-correlation-based metric. We suggest a version of the visual Strehl ratio, VScombined, that incorporates primarily those phase disruptions and contrast changes that have been shown independently to affect object recognition processes. This metric compared well to VSOTF for letter identification and was the best predictor of reading performance, having a higher correlation with the data than either the VSOTF or cross-correlation-based metric.

  14. Numerical implementation of generalized Coddington equations for ophthalmic lens design

    Science.gov (United States)

    Rojo, P.; Royo, S.; Ramírez, J.; Madariaga, I.

    2014-02-01

    A method for general implementation in any software platform of the generalized Coddington equations is presented, developed, and validated within a Matlab environment. The ophthalmic lens design strategy is presented thoroughly, and the basic concepts of generalized ray tracing are introduced. The methodology for ray tracing is shown to include two inter-related processes. Firstly, finite ray tracing is used to provide the main direction of propagation of the considered ray at the incidence point of interest. Afterwards, generalized ray tracing provides the principal curvatures of the local wavefront at that point, and its orientation after being refracted by the lens. The curvature values of the local wavefront are interpreted as the sagital and tangential powers of the lens at the point of interest. The proposed approach is validated using a double-check of the calculated lens performance in the spherical lens case: while finite ray tracing is validated using a commercial ray tracing software, generalized ray tracing is validated using a software application for ophthalmic lens design based on the classical version of Coddington equations. Equations of the complete tracing process are developed in detail for the case of generic astigmatic ophthalmic lenses as an example. Three-dimensional representation of the sagital and tangential powers of the ophthalmic lens at all directions of gaze then becomes possible, and results are presented for lenses with different geometries.

  15. Programmable diffractive lens for ophthalmic application

    Science.gov (United States)

    Millán, María S.; Pérez-Cabré, Elisabet; Romero, Lenny A.; Ramírez, Natalia

    2014-06-01

    Pixelated liquid crystal displays have been widely used as spatial light modulators to implement programmable diffractive optical elements, particularly diffractive lenses. Many different applications of such components have been developed in information optics and optical processors that take advantage of their properties of great flexibility, easy and fast refreshment, and multiplexing capability in comparison with equivalent conventional refractive lenses. We explore the application of programmable diffractive lenses displayed on the pixelated screen of a liquid crystal on silicon spatial light modulator to ophthalmic optics. In particular, we consider the use of programmable diffractive lenses for the visual compensation of refractive errors (myopia, hypermetropia, astigmatism) and presbyopia. The principles of compensation are described and sketched using geometrical optics and paraxial ray tracing. For the proof of concept, a series of experiments with artificial eye in optical bench are conducted. We analyze the compensation precision in terms of optical power and compare the results with those obtained by means of conventional ophthalmic lenses. Practical considerations oriented to feasible applications are provided.

  16. RESEARCH OF THERMO-OPTICAL INHOMOGENEITIES IN Yb-Er GLASS AT DIODE PUMPING

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    V. Khramov

    2016-03-01

    Full Text Available Subject of Research. Investigation method of thermo-optical distortions in solid-state lasers was developed and presented. The method can be easily used for research of small diameter (approximately 2 mm active elements. Method. The experimental method described in this paper is based on the registration of deviation of the energy center of the probe beam passing through the thermally stressed active element. Main Results. We have presented experimental results of the thermal lens optical power research in the active element made of Yb-Er glass pumped transversely by a laser diode in the following modes: without generating, free-running and Q-switching. We have submitted obtained dependences of the optical power on the pumping energy. The measurements have been performed for the two polarization components at two wavelengths (632.8 nm and 1550 nm showing the absence of explicit astigmatism of the thermal lens. Practical Relevance. Knowledge of the thermal regime of such lasers gives the possibility for more precise calculation of the resonator parameters in terms of the thermal lens occurrence.

  17. The Preliminary Clinical Observation of Array Multifocal lntraocular Lens Implantation

    Institute of Scientific and Technical Information of China (English)

    Zhende Lin; Bo Feng; Yizhi Liu; Bing Cheng

    2001-01-01

    Purpose: To evaluate the clinical effects of implantation of Array multifocal intraocular lenses. Methods: Thirty-one cases (37 eyes) of cataract patients, including 15 males( 19 eyes)and 16 females( 18 eyes), were involved in this study. All patients underwent standard phacoemulsification with Array multifocal intraocular lens implantation. The complications during operation, postoperative distant visual acuity, near visual acuity,corneal curvature and visual symptoms were observed. Results: the mean value of best postoperative visual acuity was recorded as follows:uncorrected distant visual acuity was 0.8, the best-corrected distant visual acuity was 0.9, uncorrected near visual acuity was 0.5, near visual acuity with distant-corrected was 0.6, the best-corrected near visual acuity wss 0.9. The astigmatism of cornea was less than 1.5 D pre-operatively and post-operatively. One patient complained of glare. Conclusion: Array multifocal intraocular lens can provide good distant and near visual acuity. With observation of more cases and follow-up of longer time, we can draw a further conclusion. Eye Science 2001; 17: 57 ~ 60.

  18. Analysis of incidence of keratoconus in relatives of patients who underwent corneal transplant due to advanced keratoconus using the Orbscan II topographic graphs

    Science.gov (United States)

    López Olazagasti, Estela; Hernández y del Callejo, César E.; Ibarra-Galitzia, Jorge; Ramírez-Zavaleta, Gustavo; Tepichín, Eduardo

    2011-10-01

    Keratoconus is a corneal disease in which the cornea assumes a conical shape due to an irregular alteration of the internal structure of the corneal tissue and sometimes is progressive, especially in young people. Anatomically, the main signs of keratoconus are thinning of the cornea in its central or paracentral region, usually accompanied by an increase in this part of a high irregular astigmatism, with a consequent loss of vision. Its diagnosis requires a thorough study including the family history, a complete ophthalmologic examination and imaging studies. This diagnosis allows classifying the type of keratoconus, which allow determining options of management, with what it is possible to establish a visual prognosis of each eye. One of the indicators that help in the diagnosis of keratoconus is an inherited familiar propensity. The literature reports an incidence of keratoconus of 11%1 in first-degree relatives of patients with keratoconus. Results suggest an ethnic dependence, which implies that the knowledge of the tendency of keratoconus in the Mexican population is important. In this work, we present the preliminary results of the study realized to a group of relatives of patients who underwent corneal transplant by advanced keratoconus using Orbscan II topographic diagnosis, to determine the predisposition to Keratoconus in this group.e

  19. Simultaneous phacoemulsification, lens implantation and endothelial keratoplasty: Triple procedure

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    Nikolić Ljubiša

    2011-01-01

    Full Text Available Introduction. Simultaneous Descemet stripping endothelial keratoplasty, phacoemulsification, and intraocular lens implantation are indicated in Fuchs’ dystrophy with associated cataract. Compared to the standard method of the triple procedure which includes penetrating keratoplasty, this new method has the advantages of sutureless surgery, small limbal incision, faster recovery, less surface problems, less astigmatism, stronger tensile strength and more predictable calculation of the intraocular lens power. This is the first report of such a combination of procedures in our literature. Case report. A 76-year-old woman suffered from a gradual bilateral visual loss. The best corrected visual acuity was 20/60 (right eye and finger counting at 1m (left eye. Corneal thickness was 590 μm and 603 μm, respectively. A marked cornea guttata and nuclear cataract were present in both eyes. Phacoemulsification, lens implantation, and Descemet stripping were done in the left eye. The posterior lamellar corneal graft, 8.0 mm in diameter and about 150 μm thick, was bent and inserted through the limbal incision. The air was injected into the anterior chamber to attach the graft to the recipient stroma. The cornea remained clear, and the transplant was attached during a two-year follow-up. Visual acuity was 20/40 after two months, and 20/25 after one year. Conclusion. The new technique proved itself as a good choice for the treatment of a mild Fuchs’ dystrophy associated with cataract.

  20. Spontaneous Rotation of a Toric Implantable Collamer Lens

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    Alejandro Navas

    2010-11-01

    Full Text Available We present a case of toric implantable collamer lens (TICL spontaneous rotation in a patient with myopic astigmatism. A 23-year-old female underwent TICL implantation. Preoperative uncorrected visual acuity (UCVA was 20/800 and 20/1200, respectively, with –7.75 –4.25 × 0° and –8.25 –5.25 × 180°. The left eye achieved an UCVA of 20/30. After 3 months of successful implantation of TICL in the left eye, the patient presented with a sudden decrease in visual acuity in the left eye. UCVA was 20/100 with a refraction of +2.50 –4.50 × 165°. We observed the toric marks with a 30° rotation from the original position and decided to reposition the TICL, obtaining a final UCVA of 20/25, which remained stable at 6 months’ follow-up. TICL can present a considerable rotation that compromises visual acuity. The relocation of TICL is a safe and effective procedure to recover visual acuity due to significant spontaneous TICL rotation.