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Sample records for corneal thickness measurements

  1. Corneal thickness: measurement and implications.

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    Ehlers, Niels; Hjortdal, Jesper

    2004-03-01

    The thickness of the cornea was reported in more than 100-year-old textbooks on physiological optics (Helmholtz, Gullstrand). Physiological interest was revived in the 1950s by David Maurice, and over the next 50 years, this 'simple' biological parameter has been studied extensively. Several techniques for its measurement have been described and physiological and clinical significance have been studied. In this review, the different methods and techniques of measurement are briefly presented (optical, ultrasound). While the corneal thickness of many animals are the same over a considerable part of the surface, in the human cornea anterior and posterior curvature are not concentric giving rise to a problem of definition. Based on this the precision and accuracy of determining the central corneal thickness are discussed. Changes in corneal thickness reflects changes in function of the boundary layers, in particular the endothelial barrier. The absolute value of thickness is of importance for the estimation of IOP but also in diagnosis of corneal and systemic disorders. Finally it is discussed to what extent the thickness is a biometric parameter of significance, e.g. in the progression of myopia or in the development of retinal detachment.

  2. Intraoperative corneal thickness measurements during corneal collagen cross-linking with isotonic riboflavin solution without dextran in corneal ectasia.

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    Cınar, Yasin; Cingü, Abdullah Kürşat; Sahin, Alparslan; Türkcü, Fatih Mehmet; Yüksel, Harun; Caca, Ihsan

    2014-03-01

    Abstract Objective: To monitor the changes in corneal thickness during the corneal collagen cross-linking procedure by using isotonic riboflavin solution without dextran in ectatic corneal diseases. The corneal thickness measurements were obtained before epithelial removal, after epithelial removal, following the instillation of isotonic riboflavin solution without dextran for 30 min, and after 10 min of ultraviolet A irradiation. Eleven eyes of eleven patients with progressive keratoconus (n = 10) and iatrogenic corneal ectasia (n = 1) were included in this study. The mean thinnest pachymetric measurements were 391.82 ± 30.34 µm (320-434 µm) after de-epithelialization of the cornea, 435 ± 21.17 µm (402-472 µm) following 30 min instillation of isotonic riboflavin solution without dextran and 431.73 ± 20.64 µm (387-461 µm) following 10 min of ultraviolet A irradiation to the cornea. Performing corneal cross-linking procedure with isotonic riboflavin solution without dextran might not induce corneal thinning but a little swelling throughout the procedure.

  3. Central Corneal Thickness Measurement by Ultrasound versus Orbscan II

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    Amir Faramarzi

    2008-12-01

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    PURPOSE: To compare Orbscan II and ultrasonic pachymetry for measurement of central corneal thickness (CCT in eyes scheduled for keratorefractive surgery. METHODS: CCT was measured using Orbscan II (Bausch & Lomb, USA and then by ultrasonic pachymetry (Tomey SP-3000, Tomey Ltd, Japan in 100 eyes of 100 patients with no history of ocular surgery scheduled for excimer laser refractive surgery. RESULTS: Mean CCT was 544.7±35.5 (range 453-637 µm by ultrasonic pachymetry versus 546.9±41.6 (range 435-648 µm measured by Orbscan II applying an acoustic factor of 0.92 (P=0.14. The standard deviation of measurements was greater with Orbscan pachymetry but the difference was not statistically significant. CONCLUSION: CCT measurements by Orbscan II (applying an acoustic factor and by ultrasonic pachymetry are not significantly different; however, when CCT readings by Orbscan II are in the lower range, it is advisable to recheck the measurements using ultrasonic pachymetry.

  1. Inter-instrument agreement and influence of central corneal thickness on measurements with Goldmann, pneumotonometer and noncontact tonometer in glaucomatous eyes.

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    Gupta, Viney; Sony, Parul; Agarwal, Harish C; Sihota, Ramanjit; Sharma, Ajay

    2006-12-01

    This study was conducted to compare the intraocular pressure (IOP) measurements by the Goldman applanation tonometer (GAT), non contact tonometer (NCT) and the ocular blood flow (OBF) pneumotonometer in different IOP ranges in glaucomatous eyes. The effect of central corneal thickness (CCT) on IOP measurement in chronic glaucomatous eyes using the three different tonometers was also evaluated. IOP measurements of 130 eyes of primary glaucoma patients were performed using GAT by an ophthalmologist while NCT and OBF-pneumotonometer measurements were performed by an experienced optometrist. The IOP values were compared amongst the three instruments in the three different IOP ranges (0-18 mmHg, > 18 to 25 mmHg, > 25 mmHg). CCT was also measured in all patients. The mean of paired difference between GAT and NCT was 0.9 +/- 3.1 mmHg while that between GAT and OBF-pneumotonometer was 0.3 +/- 3.4 mmHg. The OBF-pneumotonometer and NCT were more affected by corneal thickness (0.41 mmHg and 0.4 mmHg / 10 micro corneal thickness respectively) while GAT was the least affected by corneal thickness (0.3 mmHg / 10 micro corneal thickness) though the difference was not statistically significant ( P =0.42). With appropriate correction for corneal thickness the NCT and OBF-pneumotonometer can be used as reliably as GAT in following up glaucomatous patients.

  2. Inter-instrument agreement and influence of central corneal thickness on measurements with Goldmann, pneumotonometer and noncontact tonometer in glaucomatous eyes

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    Gupta Viney

    2006-01-01

    Full Text Available Purpose: This study was conducted to compare the intraocular pressure (IOP measurements by the Goldman applanation tonometer (GAT, non contact tonometer (NCT and the ocular blood flow (OBF pneumotonometer in different IOP ranges in glaucomatous eyes. The effect of central corneal thickness (CCT on IOP measurement in chronic glaucomatous eyes using the three different tonometers was also evaluated. Materials and Methods: IOP measurements of 130 eyes of primary glaucoma patients were performed using GAT by an ophthalmologist while NCT and OBF-pneumotonometer measurements were performed by an experienced optometrist. The IOP values were compared amongst the three instruments in the three different IOP ranges (0-18 mmHg,> 18 to 25 mmHg, > 25 mmHg. CCT was also measured in all patients. Results: The mean of paired difference between GAT and NCT was 0.9 ± 3.1 mmHg while that between GAT and OBF-pneumotonometer was 0.3 ± 3.4 mmHg. The OBF-pneumotonometer and NCT were more affected by corneal thickness (0.41 mmHg and 0.4 mmHg / 10 µ corneal thickness respectively while GAT was the least affected by corneal thickness (0.3 mmHg / 10 µ corneal thickness though the difference was not statistically significant ( P =0.42. Conclusion: With appropriate correction for corneal thickness the NCT and OBF-pneumotonometer can be used as reliably as GAT in following up glaucomatous patients.

  3. [The influence of corneal thickness and curvature on the difference between intraocular pressure measurements obtained with a non-contact tonometer and those with a Goldmann applanation tonometer].

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    Matsumoto, T; Makino, H; Uozato, H; Saishin, M; Miyamoto, S

    2000-05-01

    The influence of corneal thickness and curvature on the difference between intraocular pressure (IOP) measurements obtained with a non-contact tonometer (NCT) and those with a Goldmann applanation tonometer (GAT) was studied. The corneal thickness and curvature were obtained in 230 eyes of 115 subjects. The correlation between them and ratios of measurement with NCT to that with GAT ([NCT/GAT]) were examined. [NCT/GAT] and corneal thickness showed a significant positive correlation (r = 0.556, p < 0.01), but, the correlation between [NCT/GAT] and the radius of corneal curvature was not statistically significant (r = -0.035, p = 0.30). The thick cornea has more influence on the measurement with NCT than GAT, because IOP is measured with NCT over a wider applanation area. The corneas with steeper curvature also cause higher corneal rigidity and produce more overestimation of NCT measurement, while they have stronger capillary attraction of the precorneal tear film for the GAT tip and also produce overestimation of GAT measurement. As a result, [NCT/GAT] was believed to be not influenced by the corneal curvature.

  4. The Influence of Corneal Thickness and Curvature on the Difference Between Intraocular Pressure Measurements Obtained with a Non-contact Tonometer and Those with a Goldmann Applanation Tonometer.

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    Matsumoto; Makino; Uozato; Saishin; Miyamoto

    2000-11-01

    Purpose: The influence of corneal thickness and curvature on the difference between intraocular pressure (IOP) measurements obtained with a non-contact tonometer (NCT) and those with a Goldmann applanation tonometer (GAT) was studied.Methods: The corneal thickness and curvature were obtained in 230 eyes of 115 subjects. The correlation between them and ratios of measurement with NCT to that with GAT ([NCT/GAT]) were examined.Results: [NCT/GAT] and corneal thickness showed a significant positive correlation (r = 0.556, P <.01), but, the correlation between [NCT/GAT] and the radius of corneal curvature was not statistically significant (r = -0.035, P =.30).Conclusion: The thick cornea has more influence on the measurement with NCT than GAT, because IOP is measured with NCT over a wider applanation area. The corneas with steeper curvature also cause higher corneal rigidity and produce more overestimation of NCT measurement, while they have stronger capillary attraction of the precorneal tear film for the GAT tip and also produce overestimation of GAT measurement. As a result, [NCT/GAT] was believed to be not influenced by the corneal curvature.

  5. Reproducibility of Corneal Graft Thickness measurements with COLGATE in patients who have undergone DSAEK (Descemet Stripping Automated Endothelial Keratoplasty

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    Wong Melissa HY

    2012-08-01

    Full Text Available Abstract Background The CorneaL GrAft Thickness Evaluation (COLGATE system was recently developed to facilitate the evaluation of corneal graft thickness from OCT images. Graft thickness measurement can be a surrogate indicator for detecting graft failure or success. The purpose of this study was to determine the reproducibility of the COLGATE system in measuring DSAEK graft area between two observers. Methods This was a prospective case series in which 50 anterior segment OCT images of patients who had undergone DSAEK in either eye were analysed. Two observers (MW, AC independently obtained the image analysis for the graft area using both semi automated and automated method. One week later, each observer repeated the analysis for the same set of images. Bland-Altman analysis was performed to analyze inter and intra observer agreement. Results There was strong intraobserver correlation between the 2 semi automated readings obtained by both observers. (r = 0.936 and r = 0.962. Intraobserver ICC for observer 1 was 0.936 (95% CI 0.890 to 0.963 and 0.967 (95% CI 0.942 to 0.981 for observer 2. Likewise, there was also strong interobserver correlation (r = 0.913 and r = 0.969. The interobserver ICC for the first measurements was 0.911 (95% CI 0.849 to 0.949 and 0.968 (95% CI 0.945 to 0.982 for the second. There was statistical difference between the automatic and the semi automated readings for both observers (p = 0.006, p = 0.003. The automatic readings gave consistently higher values than the semi automated readings especially in thin grafts. Conclusion The analysis from the COLGATE programme can be reproducible between different observers. Care must be taken when interpreting the automated analysis as they tend to over estimate measurements.

  6. Effects of artificial tear treatment on corneal epithelial thickness and corneal topography findings in dry eye patients.

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    Çakır, B; Doğan, E; Çelik, E; Babashli, T; Uçak, T; Alagöz, G

    2018-05-01

    To investigate the effects of artificial tear treatment on central corneal epithelial thickness, and central, mid-peripheral and peripheral corneal thicknesses in patients with dry eye disease (DED). Patients with DED underwent ocular examinations, including Schirmer-2 test, slit lamp examination for tear break-up time (BUT), corneal topography (CT) for measuring mean central, mid-peripheral and peripheral corneal thickness values and anterior segment optic coherence tomography (AS-OCT) for obtaining central corneal epithelial thickness. After artificial tear treatment (carboxymethylcellulose and sodium hyaluronate formulations) for one month, patients were examined again at a second visit and the results were compared. Sixty-one eyes of 33 female dry eye patients (mean age: 38.3±5.7 years) were enrolled. The mean follow-up time was 36.4±3.3 days. The mean tear BUT and Schirmer-1 tests revealed significant improvement after treatment (P=0.000, P=0.000, respectively). Central corneal epithelium and mean mid-peripheral corneal thicknesses measured significantly higher after treatment (P=0.001, P=0.02). Changes in central and peripheral corneal thicknesses were not statistically significant. Artificial tear treatment in dry eye patients seems to increase central corneal epithelial and mid-peripheral corneal thicknesses. Measurement of corneal epithelial thickness can be a useful tool for evaluation of treatment response in dry eye patients. Further long-term prospective studies are needed to investigate this item. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

  7. Intraocular pressure, corneal thickness, and corneal hysteresis in Steinert's myotonic dystrophy

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    Carlos Alexandre de A. Garcia Filho

    2011-06-01

    Full Text Available PURPOSE: Low intraocular pressure (IOP measured by Goldmann applanation tonometry (GAT is one of the ocular manifestations of Steinert's myotonic dystrophy. The goal of this study was to evaluate the corneal-compensated IOP as well as corneal properties (central corneal thickness and corneal hysteresis in patients with myotonic dystrophy. METHODS: A total of 12 eyes of 6 patients with Steinert's myotonic dystrophy (dystrophy group and 12 eyes of 6 age-, race-, and gender-matched healthy volunteers (control group were included in the study. GAT, Dynamic Contour Tonometry (DCT-Pascal and Ocular Response Analyzer (ORA were used to assess the IOP. Central corneal thickness was obtained by ultrasound pachymetry, and corneal hysteresis was analyzed using the ORA device. In light of the multiplicity of tests performed, the significance level was set at 0.01 rather than 0.05. RESULTS: The mean (standard deviation [SD] GAT, DCT, and corneal-compensated ORA IOP in the dystrophy group were 5.4 (1.4 mmHg, 9.7 (1.5 mmHg, and 10.1 (2.6 mmHg, respectively. The mean (SD GAT, DCT, and corneal-compensated ORA IOP in the control group was 12.6 (2.9 mmHg, 15.5 (2.7 mmHg, and 15.8 (3.4 mmHg, respectively. There were significant differences in IOP values between dystrophy and control groups obtained by GAT (mean, -7.2 mmHg; 99% confidence interval [CI], -10.5 to -3.9 mmHg; P<0.001, DCT (mean, -5.9 mmHg; 99% CI, -8.9 to -2.8 mmHg; P<0.001, and corneal-compensated ORA measurements (mean, -5.7 mmHg; 99% CI, -10.4 to -1.0 mmHg; P=0.003. The mean (SD central corneal thickness was similar in the dystrophy (542 [31] µm and control (537 [11] µm groups (P=0.65. The mean (SD corneal hysteresis in the dystrophy and control groups were 11.2 (1.5 mmHg and 9.7 (1.2 mmHg, respectively (P=0.04. CONCLUSIONS: Patients with Steinert's myotonic dystrophy showed lower Goldmann and corneal-compensated IOP in comparison with healthy individuals. Since central corneal thickness and

  8. The applicability of correction factor for corneal thickness on non-contact tonometer measured intraocular pressure in LASIK treated eyes.

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    Jethani, Jitendra; Dave, Paaraj; Jethani, Monica; Desai, Yogesh; Patel, Purvi

    2016-01-01

    To determine the applicability of central corneal thickness (CCT) based correction factor for non-contact tonometer (NCT) measured intraocular pressure (IOP) readings. A prospective, non-randomized study involved 346 eyes of 173 consecutive patients with age ⩾21 years undergoing laser-assisted in situ keratomileusis (LASIK) for myopia and/or myopic astigmatism. The CCT and IOP were measured before and after the LASIK procedure. The IOP pre and post-LASIK was compared after applying the correction factor for CCT. Patients not completing the 3 month postoperative follow-up were excluded. The median spherical equivalent before undergoing LASIK was -4.25D (inter-quartile range, -3.25D). The mean preoperative CCT was 536.82 ± 33.71 μm which reduced to 477.55 ± 39.3 μm (p < 0.01) post-LASIK. The mean IOP reduced from a preoperative value of 14.6 ± 2.32 mmHg to 10.64 ± 2.45 mmHg postoperatively (p < 0.01). On applying correction for the corneal thickness, the pre and postoperative IOP was 15.14 ± 2.8 mmHg and 15.37 ± 2.65 mmHg (p = 0.06) respectively with a strong positive correlation (r = 0.7, p < 0.01). Three hundred eyes (86.7%) had an absolute difference in IOP of less than 3.0 mmHg post-CCT correction which is within the retest variability of NCT. Only 46 eyes (13.3%) had an absolute difference of more than 3.0 mmHg. The modified Ehler's correction algorithm used in this study can be effectively applied in the normal IOP range in a majority of patients.

  9. Analysis of the horizontal corneal diameter, central corneal thickness, and axial length in premature infants

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    Ozdemir Ozdemir

    2014-08-01

    Full Text Available Purpose: To determine the horizontal corneal diameter, central corneal thickness, and axial length in premature infants. Methods: Infants with a birth weight of less than 2,500 g or with a gestation period of less than 36 weeks were included in the study. Infants with retinopathy of prematurity (ROP were allocated to Group 1 (n=138, while those without ROP were allocated to Group 2 (n=236. All infants underwent a complete ophthalmologic examination, including corneal diameter measurements, pachymetry, biometry, and fundoscopy. Between-group comparisons of horizontal corneal diameter, central corneal thickness, and axial lengths were performed. Independent sample t-tests were used for statistical analysis. Results: Data was obtained from 374 eyes of 187 infants (102 female, 85 male. The mean gestational age at birth was 30.7 ± 2.7 weeks (range 25-36 weeks, the mean birth weight was 1,514 ± 533.3 g (range 750-1,970 g, and the mean postmenstrual age at examination was 40.0 ± 4.8 weeks. The mean gestational age and the mean birth weight of Group 1 were statistically lower than Group 2 (p0.05. Conclusions: The presence of ROP in premature infants does not alter the horizontal corneal diameter, central corneal thickness, or axial length.

  10. Comparison of central corneal thickness and endothelial cell measurements by Scheimpflug camera system and two noncontact specular microscopes.

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    Karaca, Irmak; Yilmaz, Suzan Guven; Palamar, Melis; Ates, Halil

    2017-07-03

    To investigate the correlation of Scheimpflug camera system and two noncontact specular microscopes in terms of central corneal thickness (CCT) and corneal endothelial cell morphology measurements. One hundred eyes of 50 healthy subjects were examined by Pentacam Scheimpflug Analyzer, CEM-530 (Nidek Co, Ltd, Gamagori, Japan) and CellChek XL (Konan Medical, California, USA) via fully automated image analysis with no corrections made. Measurement differences and agreement between instruments were determined by intraclass correlation analysis. The mean age of the subjects was 36.74 ± 8.59 (range 22-57). CCTs were well correlated among all devices, with having CEM-530 the thinnest and CellChek XL the thickest measurements (intraclass correlation coefficient (ICC) = 0.83; p < 0.001 and ICC = 0.78; p < 0.001, respectively). Mean endothelial cell density (ECD) given by CEM-530 was lower than CellChek XL (2613.17 ± 228.62 and 2862.72 ± 170.42 cells/mm 2 , respectively; ICC = 0.43; p < 0.001). Mean value for coefficient of variation (CV) was 28.57 ± 3.61 in CEM-530 and 30.30 ± 3.53 in CellChek XL. Cell hexagonality (HEX) with CEM-530 was higher than with CellChek XL (68.70 ± 4.16% and 45.19 ± 6.58%, respectively). ECDs with CellChek XL and CEM-530 have good correlation, but the values obtained by CellChek XL are higher than CEM-530. Measurements for HEX and CV differ significantly and show weak correlation. Thus, we do not recommend interchangeable use of CellChek XL and CEM-530. In terms of CCTs, Pentacam, CEM-530 and CellChek XL specular microscopy instruments are reliable devices.

  11. Comparación de los valores del espesor corneal central según los equipos Lenstar, Galilei y Pentacam Comparative study of the central corneal thickness measurements taken by Lenstar, Gallilei and Pentacam equipment

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    Iramis Miranda Hernández

    2012-06-01

    Full Text Available Objetivo: Comparar valores del espesor corneal central obtenidos mediante la paquimetría con el sistema de interferometria de coherencia parcial (Lenstar con los sistemas Scheimpflug (Pentacam; Oculus y Galilei (Ziemer, Suiza. Métodos: Se realizó un estudio prospectivo, comparativo en 120 ojos de 60 pacientes. Para la comparación se tomaron varias mediciones recomendadas por los fabricantes para probar la eficacia del equipo con el nuevo biómetro Lenstar LS 900 (Haag Streit AG y con los equipos Pentacam y Galilei. La comparación de los valores se realizó mediante el análisis de regresión lineal y correlación de Pearson. Resultados: El análisis reveló que existe una alta correspondencia en los valores del espesor corneal central entre Lenstar y los topógrafos Galilei y Pentacam. Conclusiones: Existe una alta correspondencia entre los valores del espesor corneal central obtenidos por los equipos Lenstar, Pentacam y Galilei. Por esto el equipo Lenstar es útil en la cirugía de catarata y la cirugía refractiva.Objective: To compare the central corneal thickness measurements taken by pachimetry with the partial coherence interferometry, Lenstar and with Scheimpflug systems (Pentacam; Oculus and Galilei (Ziemer, Switzerland. Methods: Comparative and prospective study of 120 eyes from 60 patients. Several recommended measurements were taken with the optical biometers LenstarLS 900 (Haag Streit AG and with Pentacam y Galilei topographers. The results were evaluated using the linear regresión analysis and Pearson´s correlation. Results: There is high correlation among the central corneal thickness measurements taken by the Lenstar equipment and topographers Pentacam and Galilei. Conclusion: The new biometer LENSTAR provided results that correlated very well with those of the Pentacam and Galilei systems. The Lenstar is a precise device that will be helpful for any cataract or refractive surgery.

  12. COMPARISON OF INTRAOCULAR PRESSURE MEASUREMENT WITH NON-CONTACT TONOMETRY AND APPLANATION TONOMETRY AMONG VARIOUS CENTRAL CORNEAL THICKNESS GROUPS

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    Radhakrishnan B

    2018-02-01

    Full Text Available BACKGROUND Glaucoma is the second leading cause of blindness worldwide. Intraocular Pressure (IOP is the only known modifiable risk factor that has been shown to delay progression in both ocular hypertension and glaucoma patients. Clinical measurement of IOP has undergone several technical advances from the initial digital tension measurements, through indentation tonometry, to applanation tonometry and non-contact tonometry. This study was done to compare the intraocular pressure (IOP measurements with Non Contact Tonometry (NCT and Goldmann Applanation tonometry (GAT and to compare NCT IOP and GAT IOP among various central corneal thickness (CCT groups. MATERIALS AND METHODS IOP measurements were done by NCT and then by GAT followed by CCT. All IOP readings were taken in the sitting position over fifteen minutes. NCT was performed before the GAT to avoid the known mild reduction of IOP by anterior chamber compression with GAT. RESULTS The study included 200 eyes of 100 patients. Mean age of the patients was 58.14 ± 11.7 years (range 35- 81 years. The study population consisted of 58 males and 42 females. The mean ± SD intraocular pressure measurements were 23.39 ± 4.6 mmHg and 22.41 ± 5.9 mmHg for NCT and GAT, respectively. The difference between the NCT and GAT IOP was 0.98 ± 4.7 mm Hg. Mean CCT of the study group was 545.74 ± 38.23 microns. The IOP measured with both GAT and NCT showed no significant change with increasing CCT. The difference between the means increases with increasing CCT upto 600 microns. At lower IOPs ≤ 20 mm Hg, GAT measures are higher than NCT and this relationship is reversed at high IOPs. CONCLUSION Intraocular pressure measurement by NCT was consistently higher than GAT. There was a tendency for NCT to underestimate IOP at lower ranges and overestimates IOP at higher ranges. By applying appropriate correction factor for CCT, Noncontact tonometry could be used as a good screening tool for glaucoma evaluation.

  13. Correlation between Corneal Thickness and Degree of Myopic Refractory Error

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    A Mortazavi

    2005-01-01

    Full Text Available Background: corneal thickness is an important factor in refractive surgeries such as Radial Keratotomy (RK, Photo Refractive Keratotomy (PRK and Laser Insitu Keratomileusis (LASIK. This study evaluated the correlation between this factor and the degree of myopic refractory error. Methods: In this cross-sectional study, 224 myopic eyes (112 patients which had undergone LASIK operation were assessed. These patients had referred to Aban Eye Clinic, Isfahan, Iran, during August and September 2002. Corneal thickness was measured by ORB SCAN Topoghraphy, and cycloplegic refraction was performed with autorefratometery and retinoscopy. Suspected keratoconus cases and hyperopic patients were excluded. Results: The patients' age was 27.2 ± 1.36 in men (N = 35 and 30.13 ± 1.04 in women (N = 77. Mean value of myopic refractory error in male patients was 5.1 ± 0.24D and in female patients was 3.8 ± 0.36D. Mean of corneal thickness was 540 ± 5.25 µM and 530 ± 5.88 µM in male and female patients respectively. There was no correlation between the degree of myopia and corneal thickness in any of the patients. Also in this research, no relations between the age and myopia were found. Right eye (P > 0.5, r = 0.124 Left eye (P > 0.5, r = 0.104. Conclusion: Based on our findings, corneal thickness and myopic refectory error do not seem to have any relations. (r = 0.039, p = 0.684. Keywords: Corneal Thickness, Cornea, Myopia, LASIK, Refractory Error

  14. Evaluation of intraocular pressure according to corneal thickness before and after excimer laser corneal ablation for myopia.

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    Hamed-Azzam, Shirin; Briscoe, Daniel; Tomkins, Oren; Shehedeh-Mashor, Raneen; Garzozi, Hanna

    2013-08-01

    Intraocular pressure is affected by corneal thickness and biomechanics. Following ablative corneal refractive surgery, corneal structural changes occur. The purpose of the study is to determine the relationship between the mean central corneal thickness (CCT) and the change in intraocular pressure measurements following various corneal ablation techniques, using different measurement methods. Two hundred myopic eyes undergoing laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) were enrolled into a prospective, non-randomized study. Corneal parameters examined included full ocular examination, measurement of CCT, corneal topography, corneal curvature and ocular refractivity. Intraocular pressure measurements were obtained using three different instruments-non-contact tonometer, Goldmann applanation tonometer and TonoPen XL (TonoPen-Central and TonoPen-Peripheral). All measurements were performed pre-operatively and 4 months post-operatively. Post-operative intraocular pressure was significantly lower than pre-operative values, with all instruments (p value tonometer and non-contact tonometer (p value < 0.001, ANOVA). Intraocular pressure readings are significantly reduced following corneal ablation surgery. We determined in our myopic patient cohort that the TonoPen XL intraocular pressure measurement method is the least affected following PRK and LASIK as compared to other techniques.

  15. Anatomical characterization of central, apical and minimal corneal thickness

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    Federico Saenz-Frances

    2014-08-01

    Full Text Available AIM: To anatomically locate the points of minimum corneal thickness and central corneal thickness (pupil center in relation to the corneal apex.METHODS: Observational, cross-sectional study, 299 healthy volunteers. Thickness at the corneal apex (AT, minimum corneal thickness (MT and corneal thickness at the pupil center (PT were determined using the pentacam. Distances from the corneal apex to MT (MD and PT (PD were calculated and their quadrant position (taking the corneal apex as the reference determined:point of minimum thickness (MC and point of central thickness (PC depending on the quadrant position. Two multivariate linear regression models were constructed to examine the influence of age, gender, power of the flattest and steepest corneal axes, position of the flattest axis, corneal volume (determined using the Pentacam and PT on MD and PD. The effects of these variables on MC and PC were also determined in two multinomial regression models.RESULTS: MT was located at a mean distance of 0.909 mm from the apex (79.4% in the inferior-temporal quadrant. PT was located at a mean distance of 0.156 mm from the apex. The linear regression model for MD indicated it was significantly influenced by corneal volume (B=-0.024; 95%CI:-0.043 to -0.004. No significant relations were identified in the linear regression model for PD or the multinomial logistic regressions for MC and PC.CONCLUSION: MT was typically located at the inferior-temporal quadrant of the cornea and its distance to the corneal apex tended to decrease with the increment of corneal volume.

  16. Reproducibility of the measurement of central corneal thickness in healthy subjects obtained with the optical low coherence reflectometry pachymeter and comparison with the ultrasonic pachymetry.

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    Garza-Leon, Manuel; Plancarte-Lozano, Eduardo; Valle-Penella, Agustín Del; Guzmán-Martínez, María de Lourdes; Villarreal-González, Andrés

    2018-01-01

    Corneal pachymetry is widely used for refractive surgery and follow up in keratoconus, accurate measurement is essential for a safe surgery. To assess intraobserver reliability of central corneal thickness (CCT) measurements using optical low-coherence reflectometry (OLCR) technology and its agreement with ultrasonic pachymeter (US). Randomized and prospective comparative evaluation of diagnostic technology. One randomly healthy eye of subjects was scanned three times with both devices. Intraobserver within-subject standard deviation (Sw), coefficient of variation (CVw) and intraclass correlation coefficient (ICC) were obtained for reliability analysis; for study agreement, data were analyzed using the paired-sample t test and the Bland-Altman LoA method. The mean of three scans of each equipment was used to assess the LoA. The study enrolled 30 eyes of 30 subjects with average age of 28.70 ± 8.06 years. For repeatability, the Sw were 3.41 and 5.96 µ, the intraobserver CVw was 2 and 4% and ICC 0.991 and 0.988, for OLCR and US respectively. The mean CCT difference between OLCR and US was 8.90 ± 9.03 µ (95% confidence interval: 5.52-2.27 µ), and the LoA was 35.40 µ. OLCR technology provided reliable intraobserver CCT measurements. Both pachymetry measurements may be used interchangeably with minimum calibration adjustment. Copyright: © 2018 Permanyer.

  17. Meta-analysis of Pentacam vs. ultrasound pachymetry in central corneal thickness measurement in normal, post-LASIK or PRK, and keratoconic or keratoconus-suspect eyes.

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    Wu, Wenjing; Wang, Yan; Xu, Lulu

    2014-01-01

    The aim of this meta-analysis is to evaluate the central corneal thickness (CCT) measurement differences between Pentacam (Oculus Inc., Germany) and Ultrasound Pachymetry (USP) in normal (unoperated eyes , myopic and astigmatic eyes without corneal disease or topographic irregularity), after laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK), and keratoconic or keratoconus suspected eyes. We assess whether Pentacam and USP have similar CCT differences in normal, thinner corneas after LASIK or PRK procedures, and kerotoconic or keratoconus suspected eyes. Data sources, including PubMed, Medline, EMBASE, and Cochrane Central Registry of Controlled Trials on the Cochrane Library, were searched to find the relevant studies. Primary outcome measures were CCT measurement between Pentacam and USP. Three groups of eyes were analyzed: normal; LASIK or PRK eyes; and keratoconus suspected or keratoconic eyes. Nineteen studies describing 1,908 eyes were enrolled in the normal group. Pentacam results were 1.47 μm ,95 % confidence interval (CI) -2.32 to 5.27, higher than USP without statistically significant difference (P = 0.45). Nine studies with total 539 eyes were included in the corneas after LASIK or PRK. The mean difference in the CCT measurement with Pentacam and ultrasound pachymetry was 1.03 μm, with the 95 % CI -3.36 to 5.42, there was no statistically difference (P = 0.64). Four studies with a total of 185 eyes were included in the keratoconic eyes or keratoconus-suspect group, however,the mean difference was -6.33 μm (95 % CI -9.17 to-3.49), which was statistically different between Pentacam and ultrasound pachymetry in the CCT measurement (P LASIK or PRK procedures. However, in keratoconic or keratoconus-suspect eyes, Pentacam slightly underestimates the central corneal thickness than does ultrasound pachymetry, which may result from the difficulty in fixation of keratoconic eyes, misalignment of Pentacam and the variation

  18. Thick keratoconic cornea associated with posterior polymorphous corneal dystrophy.

    Science.gov (United States)

    Zaarour, K; Slim, E; Antoun, J; Waked, N

    2017-03-01

    We herein report a case of bilateral unusually thick non-edematous keratoconic corneas with associated endothelial features of posterior polymorphous corneal dystrophy (PPCD). We report the case of a 27-year-old myopic woman who presented for refractive surgery. Slit lamp exam showed bilateral corneal protrusion with diffuse deep stromal and endothelial vesicular opacities and small paracentral bands. Topography showed generalized advanced corneal steepening in both eyes with increased anterior and posterior central corneal elevations in comparison to the best fit sphere. Ultrasound pachymetry showed central corneal thickness of 605μm (RE) and 612μm (LE). On specular biomicroscopy, cell density of 2503 cells/mm 2 RE and 1526 cells/mm 2 LE with significant cellular pleomorphism and polymegathism were noted. Clinical and paraclinical findings together suggest the presence of simultaneous keratoconus and PPCD. The literature has suggested an association between PPCD and steep cornea. Moreover, many reports have also described cases of associated PPCD and keratoconus with characteristic thinning and ectasia, in comparison to the unusual thick corneas noted in our patient, despite the absence of edema. Identification of genetics factors is further needed to clarify this association. This case describes a patient whose corneas present features of both keratoconus and PPCD and is unique due to the presence of increased corneal thickness despite the absence of edema. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  19. Comparison of Changes in Central Corneal Thickness During Corneal Collagen Cross-Linking, Using Isotonic Riboflavin Solutions With and Without Dextran, in the Treatment of Progressive Keratoconus.

    Science.gov (United States)

    Zaheer, Naima; Khan, Wajid Ali; Khan, Shama; Khan, M Abdul Moqeet

    2018-03-01

    To compare intraoperative changes in central corneal thickness (CCT) during corneal cross-linking, using 2 different isotonic riboflavin solutions either with dextran or with hydroxy propyl methylcellulose, in the treatment of progressive keratoconus. In this retrospective study, we analyzed records of corneal thickness measurements, taken during various steps of cross-linking. Cross-linking was performed using either isotonic riboflavin with dextran (group A) or isotonic riboflavin with hydroxy propyl methylcellulose (without dextran) (group B). CCT measurements were recorded before and after epithelial removal, after saturation with respective isotonic riboflavin solution, after use of hypotonic riboflavin in selected cases, and after ultraviolet A (UV-A) application. A mixed-way analysis of variance was conducted on CCT readings within each group and between both groups, and p dextran causes a significant decrease in corneal thickness, whereas dextran-free isotonic riboflavin causes a significant increase in corneal thickness, thus facilitating the procedure.

  20. The influence of central corneal thickness and age on intraocular pressure measured by pneumotonometry, non-contact tonometry, the Tono-Pen XL, and Goldmann applanation tonometry.

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    Tonnu, P-A; Ho, T; Newson, T; El Sheikh, A; Sharma, K; White, E; Bunce, C; Garway-Heath, D

    2005-07-01

    To evaluate the influence of central corneal thickness (CCT) on intraocular pressure (IOP) measurements made with the Goldmann applanation tonometer (GAT), Tono-Pen XL, ocular blood flow tonograph (OBF), and Canon TX-10 non-contact tonometer (NCT). CCT was recorded for either eye (randomly selected) of each of 105 untreated patients with ocular hypertension and glaucoma attending the glaucoma research unit at Moorfields Eye Hospital. For each of the selected eyes, IOP was measured with the GAT (two observers), Tono-Pen, OBF, and NCT in a randomised order. The relation of measured IOP and of inter-tonometer differences with CCT and subject age was explored by linear regression analysis. A significant association between measured IOP and CCT was found with each instrument. The change in measured IOP for a 10 mum increase in CCT was 0.28, 0.31, 0.38, and 0.46 for the GAT, Tono-Pen, OBF, and NCT, respectively (all p< or = 0.05). There was a significant association between the NCT/GAT differences and CCT, with a tendency of NCT to overestimate GAT in eyes with thicker corneas. There was a significant association between GAT/Tono-Pen and OBF/Tono-Pen differences and age, with a tendency of GAT and OBF to overestimate the Tono-Pen in eyes of older subjects. IOP measurement by all four methods is affected by CCT. The NCT is affected by CCT significantly more than the GAT. Subject age has a differential effect on the IOP measurements made by the GAT and OBF compared to the Tono-Pen.

  1. Central Corneal Thickness And Its Relationship To Intra-ocular And Epidemiological Determinants

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    Tayyab, A.; Masrur, A.

    2016-01-01

    Objective: To measure central corneal thickness in Pakistani population and determine its relationship to intra-ocular pressure, age, gender and ethnicity. Study Design: Cross-sectional observation study. Place and Duration of Study: Pakistan Institute of Medical Sciences, Islamabad, Pakistan, between December 2013 and February 2015. Methodology: The right eyes of 1000 cases (496 males and 504 females) were recruited for this study. Inclusion criteria were Pashtun or Punjabi ethnicity, intra-ocular pressure < 22 mmHg, gonioscopically open angles, cup-disk-ratio < 0.5, and age matched normal visual fields. Cases with prior ocular surgery, contact lens use, corneal pathologies, myopia or hypermetropia > ±3.0 diopters, astigmatism of > ±1.0 diopters were excluded. Central corneal thickness was measured using a TopCon non-contact specular microscope. Intra-ocular pressure was measured using Goldmann applanation tonometer. Frequency distribution, test of significance, and regression analysis was carried out using Statistical Package for Social Sciences version 20.0. Result: Mean age was 47.31 ±11.78 years. Ethnic composition was 51.6 percentage (n=516) Pashtun and 48.4 percentage (n=484) Punjabi. The mean central corneal thickness was 503.96 (±12.47) meu m, while the mean intra-ocular pressure was 15.61 (±2.68) mmHg. Regression analysis showed a significant association between central corneal thickness and intra-ocular pressure (p=0.00) and age (p=0.00). A ±100 μ change in central corneal thickness was associated with change in IOP of ±3.30 mmHg, whereas central corneal thickness decreased by 0.12 meu m per year. No significant association could be established between central corneal thickness and ethnicity (p=0.19). Conclusion: Central corneal thickness of the studied races was comparable to non-Caucasians which affects intra-ocular pressure measurements, and decreases with increasing age. No relationship was observed between central corneal thickness and

  2. Comparison between a New Optical Biometry Device and an Anterior Segment Optical Coherence Tomographer for Measuring Central Corneal Thickness and Anterior Chamber Depth

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    Jinhai Huang

    2016-01-01

    Full Text Available Purpose. To compare between a new optical biometer (AL-Scan, Nidek Co., Aichi, Japan and an anterior segment optical coherence tomographer (Visante AS-OCT, Carl Zeiss Meditec, Dublin, USA for measuring central corneal thickness (CCT, anterior chamber depth (ACD, and aqueous depth (AD. Methods. Sixty-three eyes of 63 normal subjects were examined with AL-Scan and Visante AS-OCT in this prospective study. One eye per subject was measured three times with both devices to record their CCT, ACD, and AD. All procedures were performed by the same operator. Agreement between the two devices was assessed using paired t-tests, Bland-Altman plots, and 95% limits of agreement (LoA. Results. The mean CCT, ACD, and AD measured by AL-Scan were 538.59±27.37 μm, 3.70±0.30 mm, and 3.16±0.30 mm, respectively. The mean values obtained by the Visante OCT were 536.14±26.61 μm for CCT, 3.71±0.29 mm for ACD, and 3.17±0.29 mm for AD. The mean CCT by the AL-Scan was higher than that obtained by the Visante AS-OCT (difference = 2.45±6.07 μm, P<0.05. The differences in ACD and AD measurements were not statistically significant. The 95% LoA of CCT, ACD, and AD were between −9.44 and 14.35 μm, −0.15 and 0.12 mm, and −0.15 and 0.12 mm, respectively. Conclusions. Since these two devices were comparable for measuring CCT, ACD, and AD, their results can be interchangeably used in the clinic.

  3. Evaluation of corneal thickness alterations during menstrual cycle in productive age women

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    Negar Amiri Ghahfarokhi

    2015-01-01

    Full Text Available Purpose: To determine the change in corneal thickness through different phases of menstrual cycle in women who are in their productive age. Materials and Methods: Fifty healthy women with normal past medical history were enrolled in this prospective study. Central corneal thickness was measured with ultrasound pachymeter three times during a menstrual cycle: Beginning of the cycle (days 1-3, ovulation time, and at the end of cycle (days 27-32. We confirmed ovulation time with determining a peak in luteinizing hormone in urine. To avoid the diurnal variation of the corneal thickness which is well recognized, we checked all our subjects at 10 in the morning. Results: In days 1 to 3 of menstruation, mean corneal thickness was 541.40±11.36 and 540.82±11.70 microns for left and right eyes respectively. At ovulation time the mean thickness changed to 556.50±7.11 and 555.98±7.26 microns for left and right eyes respectively, and at the end of the cycle, the corneal thickness turned in to 536.38±12.83 and 535.48±13.08 microns for left and right eyes respectively. The difference of corneal thickness was statistically significant relating to the different stages of menstrual cycle. Conclusion: The thickest cornea during the menstruation cycle is achieved at the ovulation time and the thinnest at the end of the cycle and this should be taken in to account whilst plan to do a corneal refractive surgery.

  4. Correlation between central corneal thickness and myopia in Taiwan

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    Yi-Chun Chen

    2014-01-01

    Full Text Available The aim of the study was to explore the correlation between central corneal thickness (CCT and the degree of myopia in Taiwanese adults. A total of 528 individuals were enrolled to undergo myopic laser refractive surgery from January 2004 to December 2006. Preoperative CCT was measured using the Orbscan corneal topography system and refractive status was determined by cycloplegic spherical equivalent. The relationship between CCT and refractive error was investigated by interindividual and intraindividual analyses. Participants had a mean age of 34.8 ± 7.3 years, and 79.9% were female. The mean refractive error was −7.27 ± 2.96 diopters and the mean CCT measurement was 560 ± 35 μm. CCT revealed that there was no association with age. However, CCT was significantly (p = 0.012 less in females than in males. The CCT also showed no significant association with refractive error (p = 0.49. Among the 67 participants with myopic anisometropia, the mean difference between both eyes was 3.09 ± 1.06 diopters. There was no association between the intereye CCT difference and refractive error (p = 0.57. The results remained the same after adjusting for age and sex. In conclusion, there was no correlation between CCT and the degree of myopia among adults in Taiwan. These data might contribute to the ongoing discussion about the role of CCT in the higher incidence of development and progression of glaucoma in myopic individuals.

  5. Confiabilidade das medidas de espessura central da córnea com Orbscan II e paquímetro ultra-sônico Reliability of corneal thickness measurements by Orbscan II and ultrasound pachymeter

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    Adamo Lui Netto

    2005-02-01

    Full Text Available OBJETIVO: Avaliar a confiabilidade das medidas de espessura central de córnea comparando o Orbscan II com o paquímetro ultra-sônico. MÉTODOS: Foi realizado estudo retrospectivo de 134 olhos, por meio do levantamento de prontuários de 67 pacientes avaliados entre o período de janeiro a junho de 2001. Foram avaliados o sexo, idade, acuidade visual com a melhor correção, refração e medidas de espessura central corneal pelo paquímetro ultra-sônico e Orbscan II. Os dados paquimétricos foram submetidos à análise do teste t pareado e as diferenças consideradas significativas se pPURPOSE: To access the reliability of corneal thickness measurements by Orbscan II and ultrasound pachymeter. METHODS: A retrospective study of 134 eyes from 67 normal subjects between January and June 2001 was obtained. Sex, age, visual acuity, refractive error and corneal thickness measurements by Orbscan II and ultrasound pachymetry were evaluated. All results were analyzed by the paired t test (p<0.05. RESULTS: Sixty-seven subjects, 34 (50.7% female and 33 (49.3% male, with a mean age of 32.44±9.98 were evaluated. The mean of spherical equivalent was -2.68±2.62. The mean corneal thickness was 534.81±34.45 with the Orbscan II system and 535.00±29.53 with the ultrasound pachymeter, values that were not significantly different (p=0.8922. The correlation coefficient between both instruments was 0.8774, and it is effective. CONCLUSIONS: Both methods are similar showing good correlation. In this study, the Orbscan II showed reliability, and this tool is extremely useful to evaluate subjects regarding refractive surgery.

  6. Assessment of corneal epithelial thickness in dry eye patients.

    Science.gov (United States)

    Cui, Xinhan; Hong, Jiaxu; Wang, Fei; Deng, Sophie X; Yang, Yujing; Zhu, Xiaoyu; Wu, Dan; Zhao, Yujin; Xu, Jianjiang

    2014-12-01

    To investigate the features of corneal epithelial thickness topography with Fourier-domain optical coherence tomography (OCT) in dry eye patients. In this cross-sectional study, 100 symptomatic dry eye patients and 35 normal subjects were enrolled. All participants answered the ocular surface disease index questionnaire and were subjected to OCT, corneal fluorescein staining, tear breakup time, Schirmer 1 test without anesthetic (S1t), and meibomian morphology. Several epithelium statistics for each eye, including central, superior, inferior, minimum, maximum, minimum - maximum, and map standard deviation, were averaged. Correlations of epithelial thickness with the symptoms of dry eye were calculated. The mean (±SD) central, superior, and inferior corneal epithelial thickness was 53.57 (±3.31) μm, 52.00 (±3.39) μm, and 53.03 (±3.67) μm in normal eyes and 52.71 (±2.83) μm, 50.58 (±3.44) μm, and 52.53 (±3.36) μm in dry eyes, respectively. The superior corneal epithelium was thinner in dry eye patients compared with normal subjects (p = 0.037), whereas central and inferior epithelium were not statistically different. In the dry eye group, patients with higher severity grades had thinner superior (p = 0.017) and minimum (p dry eye corneal epithelium was thinner than normal eyes in the superior region. In more severe dry eye disease patients, the superior and minimum epithelium was much thinner, with a greater range of map standard deviation.

  7. Biomechanical corneal changes induced by different flap thickness created by femtosecond laser

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    Fabricio W. Medeiros

    2011-01-01

    Full Text Available OBJECTIVE: To evaluate the impact of the creation of corneal flaps at different thicknesses on the biomechanical properties of swine corneas. METHOD: Twelve swine eyes were obtained to form two groups: 100 μm flap thickness and 300 μm flap thickness. Each eye was submitted to the following examinations: raster topography to investigate corneal curvature alterations, ocular response analyzer to investigate corneal hysteresis change, optical coherence tomography to measure central corneal and flap thickness and sonic wave propagation velocity as a measure of stiffness, before and immediately after flap creation. After flap amputation, surface wave velocity measurements were repeated. RESULTS: Measured flap thicknesses were statistically different for thin and thick flap groups, with an average of 108.5 + 6.9 and 307.8 + 11.5 μm respectively. Hysteresis and corneal resistance factor did not change significantly after flap creation in the thin flap group. With thicker flaps, both parameters decreased significantly from 8.0 +1.0 to 5.1 +1.5 mmHg and from 8.2 + 1.6 to 4.1 +2.5 mmHg respectively. Simulated keratometry values increased in the thick flap group (from 39.5 + 1 D to 45.9+1.2 D after flap creation but not in the thin flap group (from 40.6 + 0.6 D to 41.4+ 1.0 D. Regarding surface wave velocity analysis, the surgical procedures induced statistically lower results in some positions. CONCLUSION: In the experimental conditions established by this model, thicker flaps presented a greater biomechanical impact on the cornea.

  8. Corneal Biomechanical Properties after FS-LASIK with Residual Bed Thickness Less Than 50% of the Original Corneal Thickness

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    Haixia Zhang

    2018-01-01

    Full Text Available Background. The changes in corneal biomechanical properties after LASIK remain an unknown but important topic for surgical design and prognostic evaluation. This study aims to observe the postoperative corneal biomechanical properties one month after LASIK with amount of corneal cutting (ACC greater than 50% of the central corneal thickness (CCT. Methods. FS-LASIK was performed in 10 left rabbit eyes with ACC being 60% (L60 and 65% (L65 of the CCT, while the right eyes (R were the control. After 4 weeks, rabbits were executed and corneal strip samples were prepared for uniaxial tensile tests. Results. At the same strain, the stresses of L65 and L60 were larger than those of R. The elastic moduli of L60 and L65 were larger than those of R when the stress was 0.02 MPa, while they began to be less than those of R when stress exceeds the low-stress region. After 10 s relaxation, the stress of specimens L65, L60, and R increased in turn. Conclusion. The elastic moduli of the cornea after FS-LASIK with ACC greater than 50% of the CCT do not become less under normal rabbit IOP. The limit stress grows with the rise of ACC when relaxation becomes stable.

  9. Corneal power, thickness, and stiffness: results of a prospective randomized controlled trial of PRK and LASIK for myopia.

    Science.gov (United States)

    Hjortdal, Jesper Ø; Møller-Pedersen, Torben; Ivarsen, Anders; Ehlers, Niels

    2005-01-01

    To compare the short-, medium-, and long-term changes in corneal optical power and corneal aberrations, central corneal thickness, and corneal "stiffness" assessed by pneumotonometry readings in patients having laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) for myopia. Department of Ophthalmology, Arhus University Hospital, Arhus, Denmark. One eye of each of 45 patients with myopia ranging from -6.00 to -8.00 diopters (D) (spherical equivalent spectacle refraction [SER]) was randomized to LASIK (n=25; mean SER -7.12 D +/- 0.57 [SD]) or PRK (n=20; mean SER -6.91 +/- 0.57 D). Data were collected prospectively before and 1, 3, 6, 12, and 36 months after surgery. Measurements included corneal topography (TMS-1, Tomey), corneal thickness (ultrasound pachymetry), and apparent intraocular pressure (IOP) (pneumotonometry). Retreatments were not performed during the first year, and retreated eyes were excluded from the 3-year follow-up. Changes in corneal power and aberrations, thickness, and apparent IOP were calculated in a pair-wise manner for 3 time periods: short term (preoperative to 1 month after surgery), medium term (1 to 12 months after surgery), and long term (1 to 3 years after surgery). In the short term, corneal power decreased equally in LASIK and PRK eyes. Spherical aberrations and coma-like aberrations increased equally, while corneal thickness decreased significantly less in LASIK eyes than in PRK eyes. The apparent IOP decreased more in LASIK eyes than in PRK eyes. In the medium term, corneal power increased significantly in both groups. Spherical aberrations decreased significantly in PRK eyes but not in LASIK eyes. From 1 to 12 months, corneal thickness increased more in PRK eyes than in LASIK eyes. During this period, the apparent IOP increased significantly in LASIK eyes. In the long term, corneal power and corneal aberrations did not change significantly in either group. Corneal thickness increased slightly but

  10. Relationships between central and peripheral corneal thickness in different degrees of myopia.

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    Ortiz, Sara; Mena, Laura; Rio-San Cristobal, Ana; Martin, Raul

    2014-01-01

    To analyze the relationship between the central corneal thickness (CCT) and mid-peripheral corneal thickness (PCT) with the degree of myopia [axial length (AL) and spherical equivalent refractive error (SE)]. 175 right myopic eyes from 175 patients were divided according to the degree of SE: group #1 (n=76, 12.00 D). The CCT and PCT (3mm from the apex to the superior, inferior, nasal and temporal locations) were measured with the Orbscan-II. Relative peripheral index (RPI) was calculated by dividing the PCT by the CCT. The AL was measured with the IOL Master, and the SE was obtained with subjective refraction. AL was 25.18±1.16 mm, 26.59±1.26 mm and 29.45±2.58 mm and SE was -3.31±1.40 D, -8.32±1.64 D and -16.44±4.48 D for groups #1, #2 and #3, respectively. Non-statistically significant differences in central and peripheral corneal thickness were found between groups (P>0.05 ANOVA). Non-significant relationship was found between central and peripheral corneal thickness with the AL and SE in the three study groups and in the total sample (r0.05). The RPI values were similar between groups without significant difference between groups (P>0.05 ANOVA). Linear relationship was found between RPI superior location in group #2 (r=-0.23; P=0.04) and RPI nasal location in group #3 with the EE (r=0.41; P=0.03). There are no significant differences among low, moderate and extremely myopic eyes related to the CCT and PCT. Corneal thickness is very similar in myopic eyes with small differences that are not clinically relevant to myopic patient management. Copyright © 2012 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

  11. A review of corneal diameter, curvature and thickness values and influencing factors*

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    K. P. Mashige

    2013-12-01

    Full Text Available The cornea is an important ocular structure involved in the mediation of visual perception. It is the principal refractive surface of the eye and vision can be significantly affected by relatively small changes in its structure and parameters. Measurement of corneal parameters is important in the diagnosis and management of ocular diseasessuch as keratoconus and glaucoma, and also in the fitting of contact lenses or with refractive surgery such as Laser-Assisted in situ Keratomileusis(LASIK and photorefractive keratectomy (PRK. The human corneal diameter, anterior curvature and centre thickness as well as factors influencing them are reviewed in this article. This review will be useful to eye care professionals who routinely measure these parameters when fitting contact lenses and assessing, diagnosing as well as managing corneal and other ocular conditions. (S Afr Optom 2013 72(4 185-194

  12. Analysis of central corneal thickness in different degrees of diabetic retinopathy

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    Shan Hua

    2014-06-01

    Full Text Available AIM: To study central corneal thickness(CCTand correlation in different degrees of diabetic retinopathy(DR.METHODS: A total of 65 cases(130 eyeswith different degrees of DR and 35 normal cases(70 eyesas the age-and gender-matched control group were examined by corneal endothelial microscope, to measure CCT and statistics RESULTS: Compared to control group, there were no significant difference of CCT both mild and medium nonproliferative diabetic retinopathy(NPDRgroups(P>0.05. While the CCT of severe NPDR group and proliferative diabetic retinopathy(PDRgroup were thicker than control group, and the differences were statistically significant(PPPr=0.173, PCONCLUSION: The CCT increases with severity of DR. Taking care of protecting corneal endothelium is very important in the time of therapeutic measure, especially intraocular operation, to decrease complication.

  13. [Correlation between Goldmann and non-contact tonometry based on corneal thickness].

    Science.gov (United States)

    Schepens, G; Urier, N; Bechetoille, A; De Potter, P

    2001-01-01

    In this transversal study, we measure the intra ocular pressure by means of the Goldmann tonometer and a Non-Contact tonometer along with the central cornea thickness in 136 eyes of 73 patients. The statistical analysis of the collected data doesn't allow us to establish a correlation between the variation of the corneal thickness and the difference between the Goldmann tonometer and Non-Contact tonometer measures. The relative precision of the Non-Contact tonometer compared with the Goldmann tonometer doesn't seem influenced by the central cornea thickness.

  14. Intraocular pressure in a cohort of healthy eastern European schoolchildren: variations in method and corneal thickness

    Science.gov (United States)

    2012-01-01

    Background Intraocular pressure (IOP) in the developing eye of a child is not always easy to measure and there is no technique that is known to be the most accurate for the young eye. Measurements are needed on many cohorts of children with different tonometers to determine how the values correlate between instruments, whether corneal parameters affect readings and whether correlations between age and IOP values can be discerned. The aim of this study was to undertake a comparative analysis of three different tonometers on a group of healthy children to see whether differences exist and whether these may be related to central corneal thickness and/or radius of curvature. In addition, the study adds to the relatively small body of literature on IOP in the growing eye which will collectively allow trends to be identified and ultimately norms to be established. Methods IOP was measured on 115 eyes in a group of Polish children, aged between 5–17 years (mean ± standard deviation [SD] 11.3 ± 3.0 years) using three different tonometers: non-contact (NCT), the ICare and Goldmann applanation (GAT). Readings obtained were compared between instruments and with central corneal thickness and radius of curvature. Results The ICare tonometer provided statistically higher IOP values (16.9 ± 3.4 mmHg) than the GAT (14.7 ± 2.9 mmHg) regardless of corneal thickness and whether or not a correction factor was applied. A correlation was found between central corneal thickness (CCT) and IOP values obtained with all three tonometers but only the IOP values detected with the ICare tonometer showed a statistically significant correlation with radius of curvature (p < 0.004). No correlations with age or gender were found for IOP values measured with any of the instruments. Conclusions IOP measurements on children vary significantly between instruments and correlations are affected by the corneal thickness. Further studies on children are needed to determine which

  15. Intraocular pressure in a cohort of healthy eastern European schoolchildren: variations in method and corneal thickness

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    Krzyżanowska-Berkowska Patrycja

    2012-12-01

    Full Text Available Abstract Background Intraocular pressure (IOP in the developing eye of a child is not always easy to measure and there is no technique that is known to be the most accurate for the young eye. Measurements are needed on many cohorts of children with different tonometers to determine how the values correlate between instruments, whether corneal parameters affect readings and whether correlations between age and IOP values can be discerned. The aim of this study was to undertake a comparative analysis of three different tonometers on a group of healthy children to see whether differences exist and whether these may be related to central corneal thickness and/or radius of curvature. In addition, the study adds to the relatively small body of literature on IOP in the growing eye which will collectively allow trends to be identified and ultimately norms to be established. Methods IOP was measured on 115 eyes in a group of Polish children, aged between 5–17 years (mean ± standard deviation [SD] 11.3 ± 3.0 years using three different tonometers: non-contact (NCT, the ICare and Goldmann applanation (GAT. Readings obtained were compared between instruments and with central corneal thickness and radius of curvature. Results The ICare tonometer provided statistically higher IOP values (16.9 ± 3.4 mmHg than the GAT (14.7 ± 2.9 mmHg regardless of corneal thickness and whether or not a correction factor was applied. A correlation was found between central corneal thickness (CCT and IOP values obtained with all three tonometers but only the IOP values detected with the ICare tonometer showed a statistically significant correlation with radius of curvature (p  Conclusions IOP measurements on children vary significantly between instruments and correlations are affected by the corneal thickness. Further studies on children are needed to determine which instrument is most appropriate and to derive a normative IOP scale for the growing eye.

  16. Explore the full thick layer of corneal transplantation in the treatment of pseudomonas aeruginosa corneal ulcer infection

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    Xin Wang

    2015-02-01

    Full Text Available AIM: To explore the feasibility, safety and effect of the full-thickness lamellar keratoplasty for the treatment of pseudomonas aeruginosa corneal ulcer. METHODS: Based on a retrospective non-controlled study, 25 patients were given the full-thickness lamellar keratoplasty for clinical diagnosis of pseudomonas aeruginosa infection and corneal ulcer medication conventional anti-gram-negative bacteria. Routine follow-up were carried out at postoperative 1wk; 1, 3, 6, 12, 18mo to observe the situation of corneal epithelial healing, recurrent infection, immune rejection, graft transparency and best corrected visual acuity, etc. At the 6 and 12mo postoperative, corneal endothelial cell density was reexamined.RESULTS: No patients because of Descemet's membrane rupture underwent penetrating keratoplasty surgery: One only in cases of bacterial infection after 1mo, once again did not cultivate a culture of bacteria pseudomonas aeruginosa, and the remaining 24 cases average follow-up 14±6mo, corneal graft were transparent, the cure rate was 96%. At the sixth month after surgery, there were 16 cases of eye surgery best corrected visual acuity ≥4.5, of which 3 cases ≥4.8. At the sixth month after surgery, the average corneal endothelial cell density 2 425±278/mm2; At 12mo postoperatively, it was 2 257± 326/mm2.CONCLUSION: Full-thickness lamellar keratoplasty is an effective method of pseudomonas aeruginosa infection in the treatment of corneal ulcers, corneal drying material glycerol can be achieved by visual effects.

  17. Lead Thickness Measurements

    International Nuclear Information System (INIS)

    Rucinski, R.

    1998-01-01

    The preshower lead thickness applied to the outside of D-Zero's superconducting solenoid vacuum shell was measured at the time of application. This engineering documents those thickness measurements. The lead was ordered in sheets 0.09375-inch and 0.0625-inch thick. The tolerance on thickness was specified to be +/- 0.003-inch. The sheets all were within that thickness tolerance. The nomenclature for each sheet was designated 1T, 1B, 2T, 2B where the numeral designates it's location in the wrap and 'T' or 'B' is short for 'top' or 'bottom' half of the solenoid. Micrometer measurements were taken at six locations around the perimeter of each sheet. The width,length, and weight of each piece was then measured. Using an assumed pure lead density of 0.40974 lb/in 3 , an average sheet thickness was calculated and compared to the perimeter thickness measurements. In every case, the calculated average thickness was a few mils thinner than the perimeter measurements. The ratio was constant, 0.98. This discrepancy is likely due to the assumed pure lead density. It is not felt that the perimeter is thicker than the center regions. The data suggests that the physical thickness of the sheets is uniform to +/- 0.0015-inch.

  18. Hypobaric Hypoxia: Effects on Intraocular Pressure and Corneal Thickness

    Directory of Open Access Journals (Sweden)

    Marcella Nebbioso

    2014-01-01

    Full Text Available Objective. The purpose of this study focused on understanding the mechanisms underlying ocular hydrodynamics and the changes which occur in the eyes of subjects exposed to hypobaric hypoxia (HH to permit the achievement of more detailed knowledge in glaucomatous disease. Methods. Twenty male subjects, aged 32±5 years, attending the Italian Air Force, were enrolled for this study. The research derived from hypobaric chamber, using helmet and mask supplied to jet pilotes connected to oxygen cylinder and equipped with a preset automatic mixer. Results. The baseline values of intraocular pressure (IOP, recorded at T1, showed a mean of 16±2.23 mmHg, while climbing up to 18,000 feet the mean value was 13.7±4.17 mmHg, recorded at T2. The last assessment was performed returning to sea level (T4 where the mean IOP value was 12.8±2.57 mmHg, with a significant change (P<0.05 compared to T1. Pachymetry values related to corneal thickness in conditions of hypobarism revealed a statistically significant increase (P<0.05. Conclusions. The data collected in this research seem to confirm the increasing outflow of aqueous humor (AH in the trabecular meshwork (TM under conditions of HH.

  19. Relationships between central and peripheral corneal thickness in different degrees of myopia

    Directory of Open Access Journals (Sweden)

    Sara Ortiz

    2014-01-01

    Conclusion: There are no significant differences among low, moderate and extremely myopic eyes related to the CCT and PCT. Corneal thickness is very similar in myopic eyes with small differences that are not clinically relevant to myopic patient management.

  20. Postoperative influences of the torsional phacoemulsification on foveal thickness and corneal edema

    Directory of Open Access Journals (Sweden)

    Lei Li

    2014-05-01

    Full Text Available AIM: To report the influences onfoveal thickness and corneal edema after torsional phacoemulsification.METHODS: Totally 52 patients(52 eyeswith age-related cataract were randomly assigned to phacoemulsification using torsional mode(26 eyesor conventional ultrasound mode(26 eyes. The foveal thickness examined by optical coherence tomography(OCTafter surgery at 1, 4 and 12wk and corneal edema was examined by slit lamp after surgery at 1d.RESULTS: The postoperative averagefoveal thickness datas of the two groups, comparing with corresponding preoperative datas, were significantly augmented at 1, 4 and 12wk(PPP>0.05. The effects of corneal edema in torsional group were slighter(PCONCLUSION: The postoperative influences onfoveal thickness and corneal edema with torsional mode are slighter than that with ultrasound mode, and the postoperative reactions with torsional mode are efficiently reduced.

  1. Corneal topography measurements for biometric applications

    Science.gov (United States)

    Lewis, Nathan D.

    The term biometrics is used to describe the process of analyzing biological and behavioral traits that are unique to an individual in order to confirm or determine his or her identity. Many biometric modalities are currently being researched and implemented including, fingerprints, hand and facial geometry, iris recognition, vein structure recognition, gait, voice recognition, etc... This project explores the possibility of using corneal topography measurements as a trait for biometric identification. Two new corneal topographers were developed for this study. The first was designed to function as an operator-free device that will allow a user to approach the device and have his or her corneal topography measured. Human subject topography data were collected with this device and compared to measurements made with the commercially available Keratron Piccolo topographer (Optikon, Rome, Italy). A third topographer that departs from the standard Placido disk technology allows for arbitrary pattern illumination through the use of LCD monitors. This topographer was built and tested to be used in future research studies. Topography data was collected from 59 subjects and modeled using Zernike polynomials, which provide for a simple method of compressing topography data and comparing one topographical measurement with a database for biometric identification. The data were analyzed to determine the biometric error rates associated with corneal topography measurements. Reasonably accurate results, between three to eight percent simultaneous false match and false non-match rates, were achieved.

  2. Does Dry Eye Affect Repeatability of Corneal Topography Measurements?

    Science.gov (United States)

    Doğan, Aysun Şanal; Gürdal, Canan; Köylü, Mehmet Talay

    2018-04-01

    The purpose of this study was to assess the repeatability of corneal topography measurements in dry eye patients and healthy controls. Participants underwent consecutive corneal topography measurements (Sirius; Costruzione Strumenti Oftalmici, Florence, Italy). Two images with acquisition quality higher than 90% were accepted. The following parameters were evaluated: minimum and central corneal thickness, aqueous depth, apex curvature, anterior chamber volume, horizontal anterior chamber diameter, iridocorneal angle, cornea volume, and average simulated keratometry. Repeatability was assessed by calculating intra-class correlation coefficient. Thirty-three patients with dry eye syndrome and 40 healthy controls were enrolled to the study. The groups were similar in terms of age (39 [18-65] vs. 30.5 [18-65] years, p=0.198) and gender (M/F: 4/29 vs. 8/32, p=0.366). Intra-class correlation coefficients among all topography parameters within both groups showed excellent repeatability (>0.90). The anterior segment measurements provided by the Sirius corneal topography system were highly repeatable for dry eye patients and are sufficiently reliable for clinical practice and research.

  3. Does Dry Eye Affect Repeatability of Corneal Topography Measurements?

    Directory of Open Access Journals (Sweden)

    Aysun Şanal Doğan

    2018-04-01

    Full Text Available Objectives: The purpose of this study was to assess the repeatability of corneal topography measurements in dry eye patients and healthy controls. Materials and Methods: Participants underwent consecutive corneal topography measurements (Sirius; Costruzione Strumenti Oftalmici, Florence, Italy. Two images with acquisition quality higher than 90% were accepted. The following parameters were evaluated: minimum and central corneal thickness, aqueous depth, apex curvature, anterior chamber volume, horizontal anterior chamber diameter, iridocorneal angle, cornea volume, and average simulated keratometry. Repeatability was assessed by calculating intra-class correlation coefficient. Results: Thirty-three patients with dry eye syndrome and 40 healthy controls were enrolled to the study. The groups were similar in terms of age (39 [18-65] vs. 30.5 [18-65] years, p=0.198 and gender (M/F: 4/29 vs. 8/32, p=0.366. Intra-class correlation coefficients among all topography parameters within both groups showed excellent repeatability (>0.90. Conclusion: The anterior segment measurements provided by the Sirius corneal topography system were highly repeatable for dry eye patients and are sufficiently reliable for clinical practice and research.

  4. Central corneal thickness and related factors in an elderly American Chinese population.

    Science.gov (United States)

    Wang, Dandan; Singh, Kuldev; Weinreb, Robert; Kempen, John; He, Mingguang; Lin, Shan

    2011-07-01

    To assess central corneal thickness and related factors in an elderly American Chinese population residing in San Francisco. Cross-sectional community based study. American Chinese aged 40 years and older were enrolled using random cluster sampling and volunteer screening in the Chinatown district of San Francisco. The following data were obtained: central corneal thickness by ultrasound pachymetry, intraocular pressure by Goldmann applanation tonometry, axial length by A-scan biometry, refractive status and corneal curvature by autorefractor. History of systemic and ocular diseases was collected via standard questionnaire. Central corneal thickness. Of 311 eligible subjects, 274 consented to study participation, and 228 phakic eyes were analyzed. Mean corneal thickness was 524.1 ± 31.1 µm, 545.5 ± 30.9 µm and 538.9 ± 31.8 µm in the sampling cluster, volunteer group and all subjects, respectively. A multiple linear regression model showed corneal thickness to be negatively associated with age (standardized regression coefficient [SRC] = -0.21; P = 0.016) and corneal curvature (SRC = -0.19; P = 0.018) but positively correlated with intraocular pressure (SRC = 0.20; P = 0.023). The distribution of central corneal thickness among this American Chinese population is similar to that reported in studies from East Asia. The independent factors associated with thinner corneas included older age, lower intraocular pressure and greater corneal curvature. While descendents of Chinese immigrants in America have, on average, thicker corneas than their ancestors, this phenomenon is potentially impacted by the level of intraocular pressure. © 2011 The Authors. Clinical and Experimental Ophthalmology © 2011 Royal Australian and New Zealand College of Ophthalmologists.

  5. Modalities of Tonometry and their Accuracy with Respect to Corneal Thickness and Irregularities

    OpenAIRE

    Carlos Gustavo V. De Moraes; Tiago S. Prata; Jeffrey Liebmann; Robert Ritch

    2008-01-01

    Recent advances in tonometry have led to the development of a number of devices with differing clinical applications. Their role in cases of abnormal corneal thickness and surface irregularities is particularly important, as inaccurate estimation of the true intraocular pressure (IOP) in such cases may lead to suboptimal evaluation. The purpose of the present review was to evaluate the accuracy of the most widely used devices in cases of corneal thickness and surface irregularities, based ...

  6. Dynamic contour tonometry vs. non-contact tonometry and their relation with corneal thickness

    OpenAIRE

    Briceño, Adriana; Mas, David; Domenech, Begoña

    2016-01-01

    The purpose of this study is to evaluate the concordance between intraocular pressure (IOP) values obtained with a dynamic contour tonometer (DCT) and a non-contact tonometer (NCT) in healthy patients and to investigate the effect of central corneal thickness (CCT) on IOP readings for each of the two measuring systems. The mean IOP yielded by DCT, NCT and corrected non-contact tonometer (CNCT) was 17.1 mmHg, 15.5 mmHg and 12.2 mmHg, respectively. The average CCT was 563.6 μm and the ocular pu...

  7. Central corneal thickness of Caucasians, Chinese, Hispanics, Filipinos, African Americans, and Japanese in a glaucoma clinic.

    Science.gov (United States)

    Aghaian, Elsa; Choe, Joyce E; Lin, Shan; Stamper, Robert L

    2004-12-01

    To characterize the central corneal thickness (CCT) of Asian (Chinese, Japanese, and Filipino), Caucasian, Hispanic, and African American patients in a multiethnic glaucoma practice. Retrospective study (chart review). Glaucomatous (n = 600) and nonglaucomatous (n = 201) eyes of 801 patients examined in a San Francisco glaucoma clinic from June 2002 to April 2004 who met inclusion criteria were included in the study. The 6 racial (ethnic) groups represented in the study were Caucasian (n = 186, 23.2%), Chinese (n = 157, 19.6%), Japanese (n = 121, 15.1%), Hispanic (n = 116, 14.5%), Filipino (n = 114, 14.2%), and African American (n = 107, 13.4%). Central corneal thickness was measured by means of ultrasound pachymetry in Asian (Chinese, Japanese, and Filipino), Caucasian, Hispanic, and African American participants with glaucomatous and normal eyes. The relationship between CCT and race was investigated using multivariate regression analyses, controlling for confounders. One eye of each of 801 participants was included for analysis. Correlation of mean CCT with race, glaucoma diagnosis, age, spherical equivalent, gender, and history of ocular surgery. The mean CCT of all participants was 542.9 mum. Central corneal thicknesses of Chinese (555.6 microm), Caucasian (550.4 microm), Filipino (550.6 microm), and Hispanic (548.1 microm) participants did not significantly differ. The CCT of Japanese participants (531.7 microm) was significantly less than that of Caucasians, Chinese, Filipinos, and Hispanics (all, Pvalues of CCT were significantly related to older age (PFilipinos. Caucasians, Chinese, Hispanics, and Filipinos have comparable CCT measurements, whereas the corneas of African Americans are significantly thinner. Additionally, older individuals; glaucoma suspects; and participants with NTG, POAG, PEX, and CACG have thinner corneas. Ocular hypertensives, however, have thicker corneas.

  8. Clinical observation of cutting fluctuations on central corneal thickness after laser subepithelial keratomileusis

    Directory of Open Access Journals (Sweden)

    Wei Cheng

    2017-09-01

    Full Text Available AIM:To evaluate the percentage of cutting fluctuations of central corneal thickness(CCTintraoperative used low concentration(0.02%mitomycin C(MMCafter laser-assisted subepithelial keratomileusis(LASEK. METHODS: In this prospective study, low and medium myopia group(spherical equivalent≤6.0DShas 138 patients(276 eyes. Low concentration MMC used topically in 69 patients(138 eyesrandomized after excimer laser ablation; the another traditional LASEK as control. High myopia group(6.0DSt test and their repeatability was assessed using the coefficient of variation(CV.RESULTS: At 3mo after operation, the difference of central corneal thickness and cutting value between different treatment groups was statistically significant(PPPPCONCLUSION: The study on percentage of cutting fluctuations of central corneal thickness, further confirmed low concentrations MMC in reducing postoperative corneal stromal proliferation reaction, inhibition of haze production.

  9. Coating thickness measurement

    International Nuclear Information System (INIS)

    1976-12-01

    The standard specifies measurements of the coating thickness, which make use of beta backscattering and/or x-ray fluorescence. For commonly used combinations of coating material and base material the appropriate measuring ranges and radionuclides to be used are given for continuous as well as for discontinuous measurements

  10. Evaluation of central and peripheral corneal thicknesses in patients with rheumatoid arthritis

    Directory of Open Access Journals (Sweden)

    Alime Gunes

    2015-08-01

    Full Text Available ABSTRACTPurpose:To evaluate central corneal thickness (CCT and peripheral corneal thickness (PCT in patients with rheumatoid arthritis (RA and to assess the relationships among the corneal parameters, dry eye disease, and clinical variables of RA.Methods:A total of 58 RA patients and 58 control subjects participated in this study. A detailed ophthalmological examination was performed on each subject. Dry eye evaluation was performed using Schirmer’s test, tear break-up time (TBUT, corneal fluorescein staining, and Ocular Surface Disease Index (OSDI. Corneal thickness at the apex point, the center of the pupil, the thinnest point, and PCT (3 mm from the apex to the superior, inferior, nasal, and temporal locations were evaluated using Scheimpflug imaging (Pentacam®. Additionally, the relative peripheral index (RPI was calculated by dividing the PCT by the CCT. The disease severity and quality of life were evaluated with DAS28 and HAQ, respectively. The laboratory evaluation comprised ESR and CRP.Results:The mean corneal thicknesses at the apex point, the center of the pupil, the thinnest point, and the superior, inferior, nasal, and temporal points were significantly thinner in RA patients than controls. Schirmer’s test scores and TBUT were significantly lower, and corneal staining and OSDI scores were significantly higher in RA patients. There were no significant correlations between the corneal parameters and the clinical variables of RA or dry eye tests.Conclusion:The CCT and PCT were thinner in RA patients compared to those in control subjects. However, there were no significant correlations between the corneal parameters and the clinical variables of RA or dry eye tests.

  11. No differences in central corneal thickness between open-angle and pseudoexfoliation glaucoma patients

    Directory of Open Access Journals (Sweden)

    Ayala M

    2017-04-01

    Full Text Available Marcelo Ayala,1 Johanna Karlsson2 1Eye Department, Skaraborg Hospital, Skövde, Sahlgrenska Academy, Gothenburg University and Karolinska Institute, 2Faculty of Medicine, Örebro University, Örebro, Sweden Introduction: Measurements of intraocular pressure (IOP with Goldmann applanation tonometry are affected by central corneal thickness (CCT, as thinner corneas underestimate and thicker corneas overestimate the true IOP value. The literature is controversial regarding CCT values in patients with primary open-angle glaucoma (POAG and exfoliation glaucoma (XFG. The aim of this study was to evaluate CCT in patients with XFG and POAG.Methods: CCT was evaluated with optical coherence tomography (OCT. All participants who were previously diagnosed with either POAG or XFG underwent ophthalmological examinations. Contact lens users and patients with corneal diseases were excluded.Results: Totally, 145 patients were enrolled in this study. The mean CCT was 535±30.4 µm in patients with POAG and was 536±33.7 µm in patients with XFG. The result was not statistically significant (P=0.98. The mean age for all participants was 73.8±7.7 years. The study included totally 61 women and 84 men. The two groups were similar in their demographic data, and mean deviation was the only parameter that differed statistically when comparing POAG with XFG (P=0.02.Conclusion: Our data indicate that patients with XFG do not have thinner corneas than those with POAG, and therefore, CCT can not explain why they progress differently. Keywords: primary open-angle glaucoma, exfoliative glaucoma, central corneal thickness, optical coherence tomography

  12. Comparison of central corneal thickness with four noncontact devices: An agreement analysis of swept-source technology

    OpenAIRE

    Erhan Ozyol; Pelin Özyol

    2017-01-01

    Purpose: The purpose of this study was to compare the central corneal thickness (CCT) measurements of four noncontact devices in healthy eyes. Materials and Methods: In a sample of 45 healthy controls, CCT was measured using an optical biometer (IOLMaster 700) based on swept-source optical coherence tomography (SS-OCT), high-resolution rotating Scheimpflug camera system (Pentacam HR), spectral-domain OCT (SD-OCT) device with an anterior segment module (Spectralis), and noncontact pachymetry (...

  13. Corneal thickness in dry eyes in an Iraqi population

    OpenAIRE

    Ali,Noora Mauwafak; Hamied,Furkaan M; Farhood,Qasim K

    2017-01-01

    Noora Mauwafak Ali,1 Furkaan M Hamied,1 Qasim K Farhood2 1Department of Surgery, College of Medicine, Al-Qadisiya University, Diwaniyah, 2Department of Surgery, College of Medicine, University of Babylon, Hillah, Iraq Background: Dry eye disorder is a multifactorial disease of the tears and ocular surface that results in discomfort and visual disturbance. Corneal pachymetry becomes increasingly important in refractive surgery, for the accurate assessment of intraocular pressure, and in the ...

  14. Coating thickness measuring device

    International Nuclear Information System (INIS)

    Joffe, B.B.; Sawyer, B.E.; Spongr, J.J.

    1984-01-01

    A device especially adapted for measuring the thickness of coatings on small, complexly-shaped parts, such as, for example, electronic connectors, electronic contacts, or the like. The device includes a source of beta radiation and a radiation detector whereby backscatter of the radiation from the coated part can be detected and the thickness of the coating ascertained. The radiation source and detector are positioned in overlying relationship to the coated part and a microscope is provided to accurately position the device with respect to the part. Means are provided to control the rate of descent of the radiation source and radiation detector from its suspended position to its operating position and the resulting impact it makes with the coated part to thereby promote uniformity of readings from operator to operator, and also to avoid excessive impact with the part, thereby improving accuracy of measurement and eliminating damage to the parts

  15. Ethnic Variations in Central Corneal Thickness in a Rural Population in China: The Yunnan Minority Eye Studies

    OpenAIRE

    Pan, Chen-Wei; Li, Jun; Zhong, Hua; Shen, Wei; Niu, Zhiqiang; Yuan, Yuansheng; Chen, Qin

    2015-01-01

    Purpose To describe the ethnic differences in central corneal thickness (CCT) in population-based samples of ethnic Bai, Yi and Han people living in rural China. Methods 6504 adults (2119 ethnic Bai, 2202 ethnic Yi and 2183 ethnic Han) aged 50 years or older participated in the study. Each subject underwent standardized ocular examinations and interviewer-administered questionnaires for risk factor assessment. CCT was measured for both eyes using an ultrasound pachymeter. Regression and princ...

  16. Non-invasive measurement of corneal hydration.

    Science.gov (United States)

    March, W F; Bauer, N J

    2001-01-01

    To investigate the feasibility of a confocal Raman spectroscopic technique for the noncontact assessment of corneal hydration in vivo in two legally blind subjects. A laser beam (632.8 nm; 15 mJ) was maintained on the cornea using a microscope objective lens (25x magnification, NA=0.5, f=10 mm) both for focusing the incident light as well as collecting the Raman backscattered light, in a 180 degrees backscatter configuration. An optical fiber, acting as the confocal pinhole for elimination of light from out-of-focus places, was coupled to a spectrometer that dispersed the collected light onto a sensitive array-detector for rapid spectral data acquisition over a range from 2,890 to 3,590 cm(-1). Raman spectra were recorded from the anterior 100 to 150 microm of the cornea over a period of time before and after topical application of a mild dehydrating solution. The ratio between the amplitudes of the signals at 3,400 cm(-1) (OH-vibrational mode of water) and 2,940 cm(-1) (CH-vibrational mode of proteins) was used as a measure of corneal hydration. High signal-to-noise ratio (SNR 25) Raman spectra were obtained from the human corneas using 15 mJ of laser light energy. Qualitative changes in the hydration of the anterior-most part of the corneas could be observed as a result of the dehydrating agent. Confocal Raman spectroscopy could potentially be applied clinically as a noncontact tool for the assessment of corneal hydration in vivo.

  17. Modalities of Tonometry and their Accuracy with Respect to Corneal Thickness and Irregularities

    Science.gov (United States)

    De Moraes, Carlos Gustavo V.; Prata, Tiago S.; Liebmann, Jeffrey; Ritch, Robert

    2010-01-01

    Recent advances in tonometry have led to the development of a number of devices with differing clinical applications. Their role in cases of abnormal corneal thickness and surface irregularities is particularly important, as inaccurate estimation of the true intraocular pressure (IOP) in such cases may lead to suboptimal evaluation. The purpose of the present review was to evaluate the accuracy of the most widely used devices in cases of corneal thickness and surface irregularities, based on a survey of the published literature. The analysis was based on a Medline search focusing mainly on papers that have evaluated the devices’ accuracy with respect to corneal thickness and irregularities. Nine device types (Goldmann tonometer, Tono-Pen, Perkins tonometer, Ocular Response Analyzer, non-contact tonometer, pneumatonometer, I-Care rebound tonometer, Pascal dynamic contour tonometer (DCT) and Phosphene tonometer) were described in detail. Moreover, the physical principles and major utility of each tonometer were compared. Each of the many different commercially available tonometers has specific advantages and disadvantages. New non-invasive technologies are getting closer to a precise estimation of the true IOP. However, among all tonometers, none is highly accurate when both corneal thickness and surface irregularities are present. Fifty years after its development, Goldmann tonometry remains the gold standard to which all other devices are compared.

  18. Modalities of Tonometry and their Accuracy with Respect to Corneal Thickness and Irregularities

    Directory of Open Access Journals (Sweden)

    Carlos Gustavo V. De Moraes

    2008-01-01

    Each of the many different commercially available tonometers has specific advantages and disadvantages. New non-invasive technologies are getting closer to a precise estimation of the true IOP. However, among all tonometers, none is highly accurate when both corneal thickness and surface irregularities are present. Fifty years after its development, Goldmann tonometry remains the gold standard to which all other devices are compared.

  19. Accuracy of Corneal Thickness by Swept-Source Optical Coherence Tomography and Scheimpflug Camera in Virgin and Treated Fuchs Endothelial Dystrophy.

    Science.gov (United States)

    Arnalich-Montiel, Francisco; Ortiz-Toquero, Sara; Auladell, Clara; Couceiro, Ana

    2018-06-01

    To assess intraobserver repeatability, intersession reproducibility, and agreement of swept-source Fourier-domain optical coherence tomography (SS-OCT) and the Scheimpflug camera in measuring corneal thickness in virgin and grafted eyes with Fuchs endothelial corneal dystrophy (FECD). Thirty-six control eyes, 35 FECD eyes, 30 FECD with corneal edema eyes, 25 Descemet stripping automated endothelial keratoplasty (DSAEK) eyes, and 29 Descemet membrane endothelial keratoplasty (DMEK) eyes were included. The apical center, pupillary center, and thinnest corneal thickness were determined in 3 consecutive images and repeated 2 weeks later. Repeatability and reproducibility coefficients, intraclass correlation coefficients, and 95% limits of agreement (LOA) between measurements were calculated. Agreement between devices was assessed using Bland-Altman analysis. Corneal thickness measurements were highly reproducible and repeatable with both systems. SS-OCT showed better repeatability in all corneal locations in the normal, FECD, FECD with edema, DSAEK, and DMEK groups (coefficient of variation ≤0.60%, ≤0.36%, ≤0.43%, ≤1.09%, and ≤0.48%, respectively) than the Scheimpflug (coefficient of variation ≤1.15%, ≤0.92%, ≤1.10%, ≤1.25%, and ≤1.14%, respectively). Between-session 95% LOA for SS-OCT was less than 3% for all groups except for the FECD with edema group, being almost double using the Scheimpflug camera. Differences between instruments were statistically significant in all groups and locations (P group (P ≤ 0.51); however, SS-OCT underestimated all measurements. SS-OCT provides better reproducible and repeatable measurements of corneal thickness than those obtained with the Scheimpflug camera in patients with FECD or an endothelial transplant. Variations between examinations higher than the 95% LOA observed in our study should raise awareness of changes in the endothelial function.

  20. Variation of central corneal thickness in patients with diabetic retinopathy as detected by ultrasonic pachymetry in patients presenting to a tertiary care hospital

    International Nuclear Information System (INIS)

    Khan, S.A.

    2017-01-01

    To compare the central corneal thickness between patients with diabetic retinopathy and non diabetics. Study Design: A cross sectional study. Place and Duration of Study: Lahore General Hospital Lahore, from 1st Dec 2015 to 31st May 2016. Material and Methods: A cross-sectional study was conducted in the ophthalmology outpatient department of Lahore General Hospital. A total of one hundred and fifty subjects from different age groups were selected for the study. An ultrasound pachymeter was used to measure CCT. There were two groups for sample, 75 were patients with diabetic retinopathy and 75 of them were non-diabetic subjects. Results: The diabetic patients had average central corneal thickness of value 554.93 +- 33.73 microns. The average central corneal thickness found in non-diabetic patients was 520.41 +- 26.06 microns. The diabetic patients showed an increased central corneal thickness as compared to non-diabetics. The result of this study was statistically significant (p=0.001). Conclusion: The diabetic patients showed an increased central corneal thickness as compared to non-diabetic patients. (author)

  1. Correlating Corneal Biomechanics and Ocular Biometric Properties with Lamina Cribrosa Measurements in Healthy Subjects.

    Science.gov (United States)

    Pérez Bartolomé, Francisco; Martínez de la Casa, Jose María; Camacho Bosca, Irene; Sáenz-Francés, Federico; Aguilar Munoa, Soledad; Martín Juan, Alberto; Garcia-Feijoo, Julian

    2018-01-01

    To examine interrelations between corneal biomechanics, ocular biometric variables and optic disc size (ODS), lamina cribosa depth (LCD) or thickness (LCT) in a healthy population. In a cross-sectional case-control study, the following measurements were made in 81 eyes of 81 participants: axial length, anterior chamber depth, lens thickness, and central corneal thickness using the optical biometer Lenstar LS900; and corneal hysteresis (CH), corneal resistance factor (CRF), Goldman-correlated intraocular pressure (IOPg), and corneal-compensated IOP (IOPcc) using the Ocular Response Analyzer. Serial horizontal enhanced depth imaging optical coherence tomography (EDI OCT) B-scans of the optic nerve head were obtained in each participant. Mean ODS, mean LCD, and mean LCT were measured in 11 equally spaced horizontal B-scans, excluding the LC insertion area under Bruch's membrane and scleral rim. LCD was measured in 74 of 81 eyes (91.36%); LCT in 60/81 (75.3%); ODS in 81/81 (100%). CRF was poorly, but significantly, correlated with LCT (Pearson's R = 0.264; P = 0.045). IOPcc, IOPg, CH, and ocular biometrics variables were poorly (non-significantly) correlated with LCD, LCT, and ODS. CRF was poorly but directly correlated with LCT. No association was detected between CH or ocular biometric variables and ODS, LCD, or LCT.

  2. 21 CFR 886.1450 - Corneal radius measuring device.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Corneal radius measuring device. 886.1450 Section 886.1450 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... corneal size by superimposing the image of the cornea on a scale at the focal length of the lens of a...

  3. The effect of flap thickness on corneal biomechanics after myopic laser in situ keratomileusis using the M-2 microkeratome

    Directory of Open Access Journals (Sweden)

    Goussous IA

    2017-11-01

    Full Text Available Iyad A Goussous,1 Mohamed-Sameh El-Agha,1 Ahmed Awadein,1 Mohamed H Hosny,1 Alaa A Ghaith,2 Ahmed L Khattab2 1Department of Ophthalmology, Faculty of Medicine, Cairo University, Cairo, 2Faculty of Medicine, Alexandria University, Alexandria, Egypt Purpose: The purpose of this study was to determine the effect of flap thickness on corneal biomechanics after myopic laser in situ keratomileusis (LASIK.Methods: This is a prospective controlled non-randomized, institutional study. Patients underwent either epi-LASIK with mitomycin (advanced surface ablation [ASA], thin-flap LASIK (90 µm head, or thick-flap LASIK (130 µm head. In ASA, the Moria Epi-K hydroseparator was used. LASIK flaps were created using the Moria M-2 mechanical microkeratome. The corneal hysteresis (CH and corneal resistance factor (CRF were measured preoperatively and 3 months after surgery, using the Ocular Response Analyzer®.Results: Ten patients (19 eyes underwent ASA, 11 patients (16 eyes underwent thin-flap LASIK, and 11 patients (16 eyes underwent thick-flap LASIK. The mean preoperative CH was 10.47±0.88, 10.52±1.4, and 11.28±1.4 mmHg (p=0.043, respectively, decreasing after surgery by 1.75±1.02, 1.66±1.00, and 2.62±1.03 mmHg (p=0.017. The mean reduction of CH per micron of central corneal ablation was 0.031, 0.023, and 0.049 mmHg/µm (p=0.005. Mean preoperative CRF was 10.11±1.28, 10.34±1.87, and 10.62±1.76 mmHg (p=0.66, decreasing after surgery by 2.33±1.35, 2.77±1.03, and 2.92±1.10 mmHg (p=0.308. The mean reduction of CRF per micron of central corneal ablation was 0.039, 0.040, and 0.051 mmHg/µm (p=0.112.Conclusion: Thick-flap LASIK caused a greater reduction of CH and CRF than thin-flap LASIK and ASA, although this was statistically significant only for CH. ASA and thin-flap LASIK were found to be biomechanically similar. Keywords: flap thickness ectasia, hysteresis, LASIK, surface ablation

  4. Evaluation of Human Corneal Lenticule Quality After SMILE With Different Cap Thicknesses Using Scanning Electron Microscopy.

    Science.gov (United States)

    Weng, Shengbei; Liu, Manli; Yang, Xiaonan; Liu, Fang; Zhou, Yugui; Lin, Haiqin; Liu, Quan

    2018-01-01

    To evaluate the surface characteristics of lenticules created by small-incision lenticule extraction (SMILE) with different cap thicknesses. This prospective study included 20 consecutive patients who underwent bilateral SMILE. Surface regularity of the extracted corneal lenticule was analyzed using scanning electron microscopy (SEM) combined with 2 methods: qualitative and quantitative regularity. Qualitative regularity of SEM images was graded by masked observers using an established scoring system. Quantitative regularity of SEM images was assessed by counting the total number and areas of tissue bridges using Image-Pro Plus software. Four different cap thickness of 120, 130, 140, and 150 μm were compared. Refractive outcomes of patients were measured at baseline and 1 month after surgery. As 10 specimens were not analyzable, only 30 eyes were included. Postoperatively, all eyes had postoperative uncorrected distance visual acuity of 20/20 or better; 43% had an unchanged corrected distance visual acuity; 43% gained 1 line; 10% lost 1 line. Ultrastructurally, surface irregularity was primarily caused by tissue bridges. The average surface regularity score obtained was 10.87 ± 2.40 for 120 μm, 10.78 ± 2.60 for 130 μm, 8.76 ± 2.16 for 140 μm, and 8.70 ± 2.66 for 150 μm (P < 0.001). The total number and areas of tissue bridges of 120 to 130 μm were significantly less than 140 to 150 μm (P < 0.05). Surface regularity decreased as cap thickness increased (P < 0.05). There is smoother appearance of the lenticular surface as seen through SEM when a thin cap is created compared with a thick cap qualitatively and quantitatively.

  5. Ethnic differences of intraocular pressure and central corneal thickness: the Singapore Epidemiology of Eye Diseases study.

    Science.gov (United States)

    Chua, Jacqueline; Tham, Yih Chung; Liao, Jiemin; Zheng, Yingfeng; Aung, Tin; Wong, Tien Yin; Cheng, Ching-Yu

    2014-10-01

    To determine the ethnic differences in the distribution of intraocular pressure (IOP) and central corneal thickness (CCT) in a multi-ethnic Asian population by self-reported ethnicity and genetic ancestry. Population-based, cross-sectional study. A total of 10 033 adults (3353 Chinese, 3280 Malays, and 3400 Indians) aged >40 years. Participants underwent standardized systemic and ocular examinations and interviewer-administered questionnaires for risk factor assessment. The IOP readings were obtained by Goldmann applanation tonometry (Haag-Streit, Konig, Switzerland) before pupil dilation. The CCT was measured with ultrasound pachymetry. Genetic ancestry was derived using principal component (PC) analysis. Regression models were used to investigate the association of IOP and CCT with potential risk factors and genetic ancestry. Intraocular pressure and CCT. After excluding participants with a history of glaucoma surgery or medication, refractive surgery, corneal edema, or corneal dystrophy, IOP and CCT readings were available for 3251 Chinese, 3232 Malays, and 3317 Indians. The mean IOP readings in the Chinese, Malay, and Indian participants were 14.3±3.1, 15.3±3.7, and 15.8±2.9 mmHg, respectively (P Chinese, 6.2% in Malays, and 4% in Indians (P Malay and Indian participants on average had 0.81 and 1.43 mmHg higher IOP levels, respectively, than Chinese (P Chinese, 540.9±33.6 μm in Malays, and 540.4±33.6 μm in Indians (P Chinese, 68.5% in Malays, and 66.2% in Indians (P Chinese have the thickest CCT but lowest IOP among the 3 major ethnic groups. In addition, there is a higher proportion of Malays with IOP ≥21 mmHg and CCT Chinese or Indians. This disparity across ethnic groups should be taken into account by future studies investigating IOP and CCT as risk factors or diagnostic tests for glaucoma in Asian populations. Copyright © 2014 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

  6. Corneal biomechanical changes in diabetes mellitus and their influence on intraocular pressure measurements.

    Science.gov (United States)

    Sahin, Afsun; Bayer, Atilla; Ozge, Gökhan; Mumcuoğlu, Tarkan

    2009-10-01

    To investigate possible corneal biomechanical changes in patients with diabetes mellitus and understand the influence of such changes on intraocular pressure measurements. The study group was composed of 120 eyes from 61 healthy control subjects and 81 eyes from 43 diabetic subjects. IOP was measured first with an ocular response analyzer (ORA) and subsequently with a Goldmann applanation tonometer (GAT). Central corneal thickness (CCT) was measured with an ultrasonic pachymeter attached to the ORA. Axial length (AL), anterior chamber depth (ACD), and keratometry readings were acquired with partial coherence laser interferometry during the same visit before all IOP and CCT determinations were made. Corneal hysteresis (CH) was found to be significantly lower in diabetic patients when compared with healthy control subjects (9.51 +/- 1.82 mm Hg vs. 10.41 +/- 1.66 mm Hg, P < 0.0001). There was no significant difference in terms of corneal resistance factor (CRF; P = 0.8). Mean CCT, GAT IOP, Goldmann-correlated IOP (IOPg), and corneal-compensated IOP (IOPcc) were significantly higher in diabetic patients than in healthy control subjects (P = 0.01 for CCT, P < 0.0001 for GAT IOP, IOPg, and IOPcc). Diabetes affects corneal biomechanics and results in lower CH values than those in healthy control subjects, which may cause clinically relevant high IOP measurements independent of CCT.

  7. The effect of flap thickness on corneal biomechanics after myopic laser in situ keratomileusis using the M-2 microkeratome.

    Science.gov (United States)

    Goussous, Iyad A; El-Agha, Mohamed-Sameh; Awadein, Ahmed; Hosny, Mohamed H; Ghaith, Alaa A; Khattab, Ahmed L

    2017-01-01

    The purpose of this study was to determine the effect of flap thickness on corneal biomechanics after myopic laser in situ keratomileusis (LASIK). This is a prospective controlled non-randomized, institutional study. Patients underwent either epi-LASIK with mitomycin (advanced surface ablation [ASA]), thin-flap LASIK (90 µm head), or thick-flap LASIK (130 µm head). In ASA, the Moria Epi-K hydroseparator was used. LASIK flaps were created using the Moria M-2 mechanical microkeratome. The corneal hysteresis (CH) and corneal resistance factor (CRF) were measured preoperatively and 3 months after surgery, using the Ocular Response Analyzer ® . Ten patients (19 eyes) underwent ASA, 11 patients (16 eyes) underwent thin-flap LASIK, and 11 patients (16 eyes) underwent thick-flap LASIK. The mean preoperative CH was 10.47±0.88, 10.52±1.4, and 11.28±1.4 mmHg ( p =0.043), respectively, decreasing after surgery by 1.75±1.02, 1.66±1.00, and 2.62±1.03 mmHg ( p =0.017). The mean reduction of CH per micron of central corneal ablation was 0.031, 0.023, and 0.049 mmHg/µm ( p =0.005). Mean preoperative CRF was 10.11±1.28, 10.34±1.87, and 10.62±1.76 mmHg ( p =0.66), decreasing after surgery by 2.33±1.35, 2.77±1.03, and 2.92±1.10 mmHg ( p =0.308). The mean reduction of CRF per micron of central corneal ablation was 0.039, 0.040, and 0.051 mmHg/µm ( p =0.112). Thick-flap LASIK caused a greater reduction of CH and CRF than thin-flap LASIK and ASA, although this was statistically significant only for CH. ASA and thin-flap LASIK were found to be biomechanically similar.

  8. Comparison of Pre-operative Central Corneal Thickness in Pediatric Cataract Cases versus Normal

    International Nuclear Information System (INIS)

    Khan, S.; Ali, M.; Zaheer, N.

    2014-01-01

    Objective: To compare the pre-operative central corneal thickness (CCT) in paediatric cataract patients with reference to normal control group. Study Design: A case control study. Place and Duration of Study: Paediatric Ophthalmology Clinic of Al-Shifa Trust Eye Hospital (ASTEH), Rawalpindi, from November 2009 to May 2010. Methodology: The study included 116 subjects with equal number of cases and controls. Demographic profile of all the subjects was noted followed by history and detailed ophthalmic examination. CCT was measured using an ultrasonic pachymeter (model Pac Scan 300). The mean of three measurements from the central cornea were recorded in microns. Results were analyzed using SPSS version 17.0. Results: Mean CCT values of the cases was 566.83 +- 37.646 microns while the control group had a mean CCT of 535.81 +- 24.466 microns. Difference between the CCT values of the two groups was highly significant (p < 0.001). Conclusion: Eyes with congenital cataracts have greater CCT values as compared to normal paediatric population. This factor must be kept in mind while interpreting intra-ocular pressure in such patients. (author)

  9. Corneal thickness changes during corneal collagen cross-linking with UV-A irradiation and hypo-osmolar riboflavin in thin corneas

    Directory of Open Access Journals (Sweden)

    Belquiz Amaral Nassaralla

    2013-06-01

    Full Text Available PURPOSE: To evaluate the thinnest corneal thickness changes during and after corneal collagen cross-linking treatment with ultraviolet-A irradiation, using hypo-osmolar riboflavin solution in thin corneas. METHODS: Eighteen eyes of 18 patients were included in this study. After epithelium removal, iso-osmolar 0.1% riboflavin solution was instilled to the cornea every 3 minutes for 30 minutes. Hypo-osmolar 0.1% riboflavin solution was then applied every 20 seconds for 5 minutes or until the thinnest corneal thickness reached 400 µm. Ultraviolet-A irradiation was performed for 30 minutes. During irradiation, iso-osmolar 0.1% riboflavin drops were applied every 5 minutes. Ultrasound pachymetry was performed at approximately the thinnest point of the cornea preoperatively, after epithelial removal, after iso-osmolar riboflavin instillation, after hypo-osmolar riboflavin instillation, after ultraviolet-A irradiation, and at 1, 6 and 12 months after treatment. RESULTS: Mean preoperative thinnest corneal thickness was 380 ± 11 µm. After epithelial removal it decreased to 341 ± 11 µm, and after 30 minutes of iso-osmolar 0.1% riboflavin drops, to 330 ± 7.6 µm. After hypo-osmolar 0.1% riboflavin drops, mean thinnest corneal thickness increased to 418 ± 11 µm. After UVA irradiation, it was 384 ± 10 µm. At 1, 6 and 12 months after treatment, it was 372 ± 10 µm, 381 ± 12.7, and 379 ± 15 µm, respectively. No intraoperative, early postoperative, or late postoperative complications were noted. CONCLUSIONS: Hypo-osmolar 0.1% riboflavin solution seems to be effective for swelling thin corneas. The swelling effect is transient and short acting. Corneal thickness should be monitored throughout the procedure. Larger sample sizes and longer follow-up are required in order to make meaningful conclusions regarding safety.

  10. Corneal endothelial morphology and central thickness in patients with type II diabetes mellitus

    DEFF Research Database (Denmark)

    Storr-Paulsen, Allan; Singh, Amardeep; Jeppesen, Helene

    2014-01-01

    size was based on a power calculation (power = 0.90; p = 0.05). The diabetic patients had on average more than four HbA1c tests performed (mean 4.1; range 2-14) with intervals of at least 3 months as a reflection of the long-term glycaemic status. The controls had no diabetes confirmed by two causal......PURPOSE: To investigate corneal endothelial cell density and morphology in type II diabetic and non-diabetic patients and to relate potential differences to the glycaemic status. METHODS: A prospective clinical study including 107 patients with type II diabetes and 128 non-diabetic patients. Sample...... blood tests. The endothelial cell density, the variation in endothelial cell size (CV), the percentage of hexagonal cells, and the central corneal thickness (CCT) were recorded. RESULTS: Type II diabetic subjects did not differ from the non-diabetic control subjects with regards to endothelial cell...

  11. Intra-Ocular Pressure Measurement in a Patient with a Thin, Thick or Abnormal Cornea.

    Science.gov (United States)

    Clement, Colin I; Parker, Douglas G A; Goldberg, Ivan

    2016-01-01

    Accurate measurement of intra-ocular pressure is a fundamental component of the ocular examination. The most common method of measuring IOP is by Goldmann applanation tonometry, the accuracy of which is influenced by the thickness and biomechanical properties of the cornea. Algorithms devised to correct for corneal thickness to estimate IOP oversimplify the effects of corneal biomechanics. The viscous and elastic properties of the cornea influence IOP measurements in unpredictable ways, a finding borne out in studies of patients with inherently abnormal and surgically altered corneal biomechanics. Dynamic contour tonometry, rebound tonometry and the ocular response analyzer provide useful alternatives to GAT in patients with abnormal corneas, such as those who have undergone laser vision correction or keratoplasty. This article reviews the various methods of intra-ocular pressure measurement available to the clinician and the ways in which their utility is influenced by variations in corneal thickness and biomechanics.

  12. Reliability of Entire Corneal Thickness Mapping in Normal Post-Laser in situ Keratomileusis and Keratoconus Eyes Using Long Scan Depth Spectral Domain Optical Coherence Tomography.

    Science.gov (United States)

    Xu, Zhe; Chen, Sisi; Yang, Chun; Huang, Shenghai; Shen, Meixiao; Wang, Yuanyuan

    2018-01-01

    To investigate the repeatability and reproducibility of mapping the entire corneal thickness using spectral domain optical coherence tomography (SD-OCT). Thirty normal eyes, 30 post-laser in situ keratomileusis (LASIK) surgery eyes, and 30 keratoconus eyes were analyzed. A custom-built long scan depth SD-OCT device was used to obtain entire corneal images. Ten-millimeter-diameter corneal thickness maps were generated by an automated segmentation algorithm. Intraclass correlation coefficients of repeatability (ICC1) and reproducibility (ICC2), and coefficients of repeatability (CoR1) and reproducibility (CoR2), were calculated to quantify the precision and accuracy of corneal pachymetry measurements using the Bland-Altman method. For SD-OCT measurements in healthy subjects, CoR1 and CoR2 were less than 5.00 and 5.53 μm. ICC1 and ICC2 were more than 0.997 and 0.996. For SD-OCT measurements in LASIK patients, CoR1 and CoR2 were less than 5.09 and 5.34 μm. ICC1 and ICC2 were more than 0.997 and 0.996. For SD-OCT measurements in keratoconus patients, CoR1 and CoR2 were less than 11.57 and 10.92 μm. ICC1 and ICC2 were more than 0.995 and 0.996. The measurements of corneal pachymetric mapping by long scan depth SD-OCT can be assessed over the entire corneal area with good repeatability and reproducibility. © 2017 S. Karger AG, Basel.

  13. Measurement of Angle Kappa Using Ultrasound Biomicroscopy and Corneal Topography.

    Science.gov (United States)

    Yeo, Joon Hyung; Moon, Nam Ju; Lee, Jeong Kyu

    2017-06-01

    To introduce a new convenient and accurate method to measure the angle kappa using ultrasound biomicroscopy (UBM) and corneal topography. Data from 42 eyes (13 males and 29 females) were analyzed in this study. The angle kappa was measured using Orbscan II and calculated with UBM and corneal topography. The angle kappa of the dominant eye was compared with measurements by Orbscan II. The mean patient age was 36.4 ± 13.8 years. The average angle kappa measured by Orbscan II was 3.98° ± 1.12°, while the average angle kappa calculated with UBM and corneal topography was 3.19° ± 1.15°. The difference in angle kappa measured by the two methods was statistically significant (p topography to calculate the angle kappa. This method is convenient to use and allows for measurement of the angle kappa without an expensive device. © 2017 The Korean Ophthalmological Society

  14. Assessment of Corneal Epithelial Thickness in Asymmetric Keratoconic Eyes and Normal Eyes Using Fourier Domain Optical Coherence Tomography

    Directory of Open Access Journals (Sweden)

    S. Catalan

    2016-01-01

    Full Text Available Purpose. To compare the characteristics of asymmetric keratoconic eyes and normal eyes by Fourier domain optical coherence tomography (OCT corneal mapping. Methods. Retrospective corneal and epithelial thickness OCT data for 74 patients were compared in three groups of eyes: keratoconic (n=22 and normal fellow eyes (n=22 in patients with asymmetric keratoconus and normal eyes (n=104 in healthy subjects. Areas under the curve (AUC of receiver operator characteristic (ROC curves for each variable were compared across groups to indicate their discrimination capacity. Results. Three variables were found to differ significantly between fellow eyes and normal eyes (all p<0.05: minimum corneal thickness, thinnest corneal point, and central corneal thickness. These variables combined showed a high discrimination power to differentiate fellow eyes from normal eyes indicated by an AUC of 0.840 (95% CI: 0.762–0.918. Conclusions. Our findings indicate that topographically normal fellow eyes in patients with very asymmetric keratoconus differ from the eyes of healthy individuals in terms of their corneal epithelial and pachymetry maps. This type of information could be useful for an early diagnosis of keratoconus in topographically normal eyes.

  15. Corneal biomechanical properties in healthy children measured by corneal visualization scheimpflug technology.

    Science.gov (United States)

    He, Miao; Ding, Hui; He, Hong; Zhang, Chi; Liu, Liangping; Zhong, Xingwu

    2017-05-17

    The aim of this study was to evaluate corneal biomechanical properties in a population of healthy children in China using corneal visualization Scheimpflug technology (CST). All children underwent complete bi-ocular examinations. CST provided intraocular pressure (IOP) and corneal biomechanical parameters, including time, velocity, length and deformation amplitude at first applanation (A1T, A1V, A1L, A1DA), at second applanation (A2T, A2V, A2L, A2DA), highest concavity time (HCT), maximum deformation amplitude (MDA), peak distance (PD), and radius of curvature (RoC). Pearson correlation analysis was used to assess the impacts of demographic factors, central corneal thickness (CCT), spherical equivalent (SE), and IOP on corneal biomechanics. One hundred eight subjects (32 girls and 76 boys) with the mean age of 10.80 ± 4.13 years (range 4 to18 years) were included in the final analyses. The right and left eyes were highly symmetrical in SE (p = 0.082), IOP (p = 0.235), or CCT (p = 0.210). Mean A1T of the right eyes was 7.424 ± 0.340 ms; the left eyes 7.451 ± 0.365 ms. MDA was 0.993 ± 0.102 mm in the right eyes and 0.982 ± 0.100 mm in the left eyes. Mean HCT of the right eyes was 16.675 ± 0.502 ms; the left eyes 16.735 ± 0.555 ms. All CST parameters of both eye were remarkably symmetrical with the exception of A2L (p = 0.006), A1DA (p = 0.025). The majority of CST parameters of both eyes were significantly correlated with CCT and IOP (p children eyes. Several CST biomechanical parameters in children are modified by CCT and IOP.

  16. Applanation optical coherence elastography: noncontact measurement of intraocular pressure, corneal biomechanical properties, and corneal geometry with a single instrument

    Science.gov (United States)

    Singh, Manmohan; Han, Zhaolong; Nair, Achuth; Schill, Alexander; Twa, Michael D.; Larin, Kirill V.

    2017-02-01

    Current clinical tools provide critical information about ocular health such as intraocular pressure (IOP). However, they lack the ability to quantify tissue material properties, which are potent markers for ocular tissue health and integrity. We describe a single instrument to measure the eye-globe IOP, quantify corneal biomechanical properties, and measure corneal geometry with a technique termed applanation optical coherence elastography (Appl-OCE). An ultrafast OCT system enabled visualization of corneal dynamics during noncontact applanation tonometry and direct measurement of micro air-pulse induced elastic wave propagation. Our preliminary results show that the proposed Appl-OCE system can be used to quantify IOP, corneal biomechanical properties, and corneal geometry, which builds a solid foundation for a unique device that can provide a more complete picture of ocular health.

  17. Corneal densitometry and its correlation with age, pachymetry, corneal curvature, and refraction.

    Science.gov (United States)

    Garzón, Nuria; Poyales, Francisco; Illarramendi, Igor; Mendicute, Javier; Jáñez, Óscar; Caro, Pedro; López, Alfredo; Argüeso, Francisco

    2017-12-01

    To determine normative corneal densitometry values in relation to age, sex, refractive error, corneal thickness, and keratometry, measured using the Oculus Pentacam system. Three hundred and thirty-eight healthy subjects (185 men; 153 women) with no corneal disease underwent an exhaustive ocular examination. Corneal densitometry was expressed in standardized grayscale units (GSU). The mean corneal densitometry over the total area was 16.46 ± 1.85 GSU. The Pearson correlation coefficient for total densitometry was r = 0.542 (p  0.05). This is the first report of normative corneal densitometry values in relation to keratometry, corneal thickness, and spherical equivalent measured with the latest Oculus Pentacam software. Corneal densitometry increases with age, but corneal keratometry and refractive parameters do not affect light scattering in the human cornea.

  18. Cross-ancestry genome-wide association analysis of corneal thickness strengthens link between complex and Mendelian eye diseases

    NARCIS (Netherlands)

    Iglesias, A.I. (Adriana I.); A. Mishra (Aniket); V. Vitart (Veronique); Y. Bykhovskaya (Yelena); R. Höhn (René); H. Springelkamp (Henriët); G. Cuellar-Partida (Gabriel); P. Gharahkhani (Puya); Bailey, J.N.C. (Jessica N. Cooke); Willoughby, C.E. (Colin E.); X. Li (Xiaohui); S. Yazar (Seyhan); A. Nag (Abhishek); A.P. Khawaja (Anthony); O. Polasek (Ozren); D.S. Siscovick (David); Mitchell, P. (Paul); Y.C. Tham (Yih Chung); J.L. Haines (Jonathan); L.S. Kearns (Lisa S.); C. Hayward (Caroline); Shi, Y. (Yuan); Van Leeuwen, E.M. (Elisabeth M.); K.D. Taylor (Kent); Wang, J.J. (Jie Jin); E. Rochtchina (Elena); J. Attia (John); Scott, R. (Rodney); E.G. Holliday (Elizabeth); P.N. Baird (Paul); Xie, J. (Jing); Inouye, M. (Michael); Viswanathan, A. (Ananth); X. Sim (Xueling); P.W.M. Bonnemaijer (Pieter); J.I. Rotter (Jerome I.); Martin, N.G. (Nicholas G.); T. Zeller (Tanja); R.A. Mills (Richard); S.E. Staffieri (Sandra E.); Jonas, J.B. (Jost B.); Schmidtmann, I. (Irene); T. Boutin (Thibaud); Kang, J.H. (Jae H.); S.E.M. Lucas (Sionne E.M.); Wong, T.Y. (Tien Yin); Beutel, M.E. (Manfred E.); Wilson, J.F. (James F.); R.R. Allingham (R Rand); M.H. Brilliant (Murray H.); D.L. Budenz (Donald L.); W.G. Christen (William G.); J. Fingert (John); D.S. Friedman (David); Gaasterland, D. (Douglas); T. Gaasterland (Terry); M.A. Hauser (Michael); P. Kraft (Peter); Lee, R.K. (Richard K.); P.A. Lichter (Paul A.); Liu, Y. (Yutao); S.J. Loomis (Stephanie J.); S.E. Moroi (Sayoko); M.A. Pericak-Vance (Margaret); A. Realini (Anthony); Richards, J.E. (Julia E.); J.S. Schuman (Joel S.); W.K. Scott (William); K. Singh (Kuldev); A.J. Sit (Arthur J.); D. Vollrath (Douglas); R.N. Weinreb (Robert N.); G. Wollstein (Gadi); D.J. Zack (Donald); K. Zhang (Kang); Donnelly, P. (Peter); I.E. Barroso (Inês); Blackwell, J.M. (Jenefer M.); E. Bramon (Elvira); M.A. Brown (Matthew); J.P. Casas (Juan); A. Corvin (Aiden); Deloukas, P. (Panos); A. Duncanson (Audrey); Jankowski, J. (Janusz); H.S. Markus (Hugh); J. Mathew (Joseph); C.N.A. Palmer (Colin); R. Plomin (Robert); A. Rautanen (Anna); S.J. Sawcer (Stephen); R.C. Trembath (Richard); Wood, N.W. (Nicholas W.); C.C.A. Spencer (Chris C.); G. Band (Gavin); C. Bellenguez (Céline); Freeman, C. (Colin); F.A. Hellenthal; E. Giannoulatou (Eleni); M. Pirinen (Matti); R. Pearson (Ruth); A. Strange (Amy); Z. Su (Zhan); D. Vukcevic (Damjan); Langford, C. (Cordelia); Hunt, S.E. (Sarah E.); T. Edkins (Ted); R. Gwilliam (Rhian); H. Blackburn (Hannah); S. Bumpstead (Suzannah); S. Dronov (Serge); M. Gillman (Matthew); E. Gray (Emma); N. Hammond (Naomi); A. Jayakumar (Alagurevathi); O.T. McCann (Owen); J. Liddle (Jennifer); S.C. Potter (Simon); Ravindrarajah, R. (Radhi); Ricketts, M. (Michelle); P. Waller (Patrick); P. Weston (Paul); S. Widaa (Sara); Whittaker, P. (Pamela); A.G. Uitterlinden (André); E.N. Vithana (Eranga); P.J. Foster (Paul); P.G. Hysi (Pirro); Hewitt, A.W. (Alex W.); C.C. Khor; L.R. Pasquale (Louis); Montgomery, G.W. (Grant W.); C.C.W. Klaver (Caroline); T. Aung (Tin); A.F.H. Pfeiffer (Andreas); D.A. Mackey (David); C.J. Hammond (Christopher); Cheng, C.-Y. (Ching-Yu); J.E. Craig (Jamie); Y.S. Rabinowitz (Yaron); J.L. Wiggs (Janey L.); K.P. Burdon (Kathryn); C.M. van Duijn (Cornelia); MacGregor, S. (Stuart)

    2018-01-01

    textabstractCentral corneal thickness (CCT) is a highly heritable trait associated with complex eye diseases such as keratoconus and glaucoma. We perform a genome-wide association meta-analysis of CCT and identify 19 novel regions. In addition to adding support for known connective tissue-related

  19. The evaluation of central corneal thickness and intraocular pressure in conjunction with tear IGF-1 levels in patients with acromegaly.

    Science.gov (United States)

    Kan, Emrah; Kan, Elif K; Okuyucu, Ali

    2017-08-30

    To compare the central corneal thickness (CCT), intraocular pressure (IOP), and tear insulin-like growth factor 1 (IGF-1) levels between patients with acromegaly and a control group and to evaluate the possible effect of tear IGF-1 and duration of the disease on CCT and IOP. We included 31 patients with acromegaly (study group) and 40 age- and sex-matched controls in the study. Patients with acromegaly were divided into 2 subgroups based on disease status (active/inactive). All participants underwent complete ophthalmologic evaluation including CCT and IOP values. Basal tear samples were collected from both groups and tear IGF-1 levels were measured. The CCT, IOP, and tear IGF-1 levels were compared between groups and subgroups and the association between tear IGF-I levels and ocular parameters (CCT, IOP) and disease duration were also evaluated. Central corneal thickness, IOP, and tear IGF-1 levels did not show a significant difference between study and control groups. We also did not find a significant difference in terms of CCT, IOP, or tear IGF-1 levels between subgroups of patients. Correlation analysis did not show an association between the duration of disease and tear IGF-1 levels with CCT or IOP. There was no significant difference in tear IGF-1 levels between patients with acromegaly and controls. Additionally, there was no correlation between disease duration and tear IGF-1 levels with CCT or IOP levels. This lack of association may suggest that tear IGF-1 levels might not have an effect on CCT or IOP findings in patients with acromegaly.

  20. Accurate thickness measurement of graphene

    International Nuclear Information System (INIS)

    Shearer, Cameron J; Slattery, Ashley D; Stapleton, Andrew J; Shapter, Joseph G; Gibson, Christopher T

    2016-01-01

    Graphene has emerged as a material with a vast variety of applications. The electronic, optical and mechanical properties of graphene are strongly influenced by the number of layers present in a sample. As a result, the dimensional characterization of graphene films is crucial, especially with the continued development of new synthesis methods and applications. A number of techniques exist to determine the thickness of graphene films including optical contrast, Raman scattering and scanning probe microscopy techniques. Atomic force microscopy (AFM), in particular, is used extensively since it provides three-dimensional images that enable the measurement of the lateral dimensions of graphene films as well as the thickness, and by extension the number of layers present. However, in the literature AFM has proven to be inaccurate with a wide range of measured values for single layer graphene thickness reported (between 0.4 and 1.7 nm). This discrepancy has been attributed to tip-surface interactions, image feedback settings and surface chemistry. In this work, we use standard and carbon nanotube modified AFM probes and a relatively new AFM imaging mode known as PeakForce tapping mode to establish a protocol that will allow users to accurately determine the thickness of graphene films. In particular, the error in measuring the first layer is reduced from 0.1–1.3 nm to 0.1–0.3 nm. Furthermore, in the process we establish that the graphene-substrate adsorbate layer and imaging force, in particular the pressure the tip exerts on the surface, are crucial components in the accurate measurement of graphene using AFM. These findings can be applied to other 2D materials. (paper)

  1. The Effect of Pseudoexfoliation and Pseudoexfoliation Induced Dry Eye on Central Corneal Thickness.

    Science.gov (United States)

    Akdemir, M Orcun; Kirgiz, Ahmet; Ayar, Orhan; Kaldirim, Havva; Mert, Metin; Cabuk, Kubra Serefoglu; Taskapili, Muhittin

    2016-01-01

    The aim of this study is to investigate the effect of pseudoexfoliation (PEX) and PEX-induced dry eye on central corneal thickness (CCT). This cross-sectional study consists of total 270 eyes of 135 patients (67 females, 68 males) in total. After excluding the PEX (-) 32 eyes with PEX in the other eye, totally 130 eyes in PEX (-) group and 108 eyes in the PEX (+) group were included in the study. The PEX (+) group was regrouped as PEX syndrome (80 eyes of 50 patients) and PEX glaucoma (28 eyes of 20 patients). In the PEX (-) group, the mean Schirmer test result was 12 ± 4 mm (4-25 mm), in the PEX syndrome group 10 ± 4 mm (4-22 mm), in the PEX glaucoma group 9 ± 3 mm (4-15 mm). The difference among the PEX (-) group, the PEX syndrome and the PEX glaucoma groups was statistically significant (p eyes with PEX (r = 0.307, p = 0.001). However, there was no statistically significant correlation between CCT, Schirmer and tear break up time tests in the eyes with PEX. PEX material can cause decrease in tear film secretion and disturb tear film stability. There is no effect of PEX-induced dry eye on CCT. Lower CCT values in the eyes with PEX material may be a result of decrease in corneal stromal cell density. Moreover, higher CCT values may be because of decreased endothelial cells in PEX glaucoma patients.

  2. Quantitative assessment of rat corneal thickness and morphology during stem cell therapy by high-speed optical coherence tomography

    Science.gov (United States)

    Lal, Cerine; McGrath, James; Subhash, Hrebesh; Rani, Sweta; Ritter, Thomas; Leahy, Martin

    2016-03-01

    Optical Coherence Tomography (OCT) is a non-invasive 3 dimensional optical imaging modality that enables high resolution cross sectional imaging in biological tissues and materials. Its high axial and lateral resolution combined with high sensitivity, imaging depth and wide field of view makes it suitable for wide variety of high resolution medical imaging applications at clinically relevant speed. With the advent of swept source lasers, the imaging speed of OCT has increased considerably in recent years. OCT has been used in ophthalmology to study dynamic changes occurring in the cornea and iris, thereby providing physiological and pathological changes that occur within the anterior segment structures such as in glaucoma, during refractive surgery, lamellar keratoplasty and corneal diseases. In this study, we assess the changes in corneal thickness in the anterior segment of the eye during wound healing process in a rat corneal burn model following stem cell therapy using high speed swept source OCT.

  3. Changes in central corneal thickness and endothelial cell count pediatric cataract surgery

    International Nuclear Information System (INIS)

    Memon, M.N.

    2015-01-01

    To evaluate the mean changes in Central Corneal Thickness (CCT) and Endothelial Cell Count (ECC) in eyes after pediatric cataract surgery with foldable intraocular lens using scleral tunnel incision micro-surgical technique. Study Design: Qausi experimental study. Place and Duration of Study: Department of Pediatric Ophthalmology and Strabismus, Al-Shifa Trust Eye Hospital, Rawalpindi, from May 2011 to March 2012. Methodology: Fifty-two eyes of 37 children with pediatric cataract were included in the study. Extracapsular Cataract Extraction (ECE) with foldable Intra Ocular Lens (IOL) implantation using sclera tunnel incision was performed in all children. Endothelial Cell Count (ECC) and Central Corneal Thickness (CCT) were recorded before surgery and 1 month, 3 months and 6 months after surgery and the effect of currently practiced surgical technique on ECC and CCTwas evaluated. Results: The mean age at the time of surgery was 8.8 ± 2.7 years (range: 4 to 15 years). The postoperative ECC and CCT were significantly different from the pre-operative values. Mean pre-operative ECC was 3175.3 ± 218.4 cell/mm2 and in first postoperative month the mean ECC was 3113.4 ± 210.8 cell/mm2 (p<0.0001). In the 3rd and 6th month postoperative means ECC were 3052 ± 202.5 cell/mm2 (p<0.0001) and 3015 ±190.6 cell/mm2 (p<0.0001), respectively. The mean cell loss at first postoperative month was 1.95% and at 3rd and 6th postoperative month were 3.9% and 5.05%, respectively. Mean pre-operative CCT was 514 ± 49.9 micro m and first postoperative mean CCT after 1 month was 524.1 ± 25 micro m (p = 0.084). After the 3rd and 6th months postoperative, mean CCT were 527.3 ± 24.6 micro m, and 530 ± 24.5 micro m, respectively. Third and 6th months postoperative means were significantly higher than baseline CCT, p = 0.024 and 0.007, respectively. Conclusion: Endothelial cell loss with closed chamber micro-surgical technique using scleral tunnel incision is within acceptable limits and

  4. Ethnic Variations in Central Corneal Thickness in a Rural Population in China: The Yunnan Minority Eye Studies.

    Directory of Open Access Journals (Sweden)

    Chen-Wei Pan

    Full Text Available To describe the ethnic differences in central corneal thickness (CCT in population-based samples of ethnic Bai, Yi and Han people living in rural China.6504 adults (2119 ethnic Bai, 2202 ethnic Yi and 2183 ethnic Han aged 50 years or older participated in the study. Each subject underwent standardized ocular examinations and interviewer-administered questionnaires for risk factor assessment. CCT was measured for both eyes using an ultrasound pachymeter. Regression and principal component analysis were performed to examine the relationship of ethnicity and other factors with CCT.The mean CCT readings were 536.4 ± 34.2 μm in ethnic Bai, 532.1 ± 32.1 μm in ethnic Yi and 529.6 ± 32.7 μm in ethnic Han adults (P<0.001, respectively. There was a decreasing trend of mean CCT with increasing age across all ethnic groups. In multivariate linear regression models, increasing CCT was associated with younger age (P<0.001, male gender (P<0.001, Bai (P<0.001 or Yi (P<0.001 ethnicity, greater body mass index (P<0.001, higher systolic blood pressure (P<0.001, greater corneal curvature (P<0.001, deeper anterior chamber (P < 0.001, and thicker lens (P<0.001. Ethnicity contributed significantly to presence of thin cornea (60%; P< 0.001 compared with other factors. CCT had similar impact on intraocular pressure readings across all ethnic groups.This study of more than 6500 multiethnic participants demonstrates significant ethnic variations in CCT, with Han ethnicity having the thinnest cornea compared with ethnic minorities. These data are essential to guide future multiethnic clinical trials on CCT-related ocular conditions such as glaucoma.

  5. Cross-ancestry genome-wide association analysis of corneal thickness strengthens link between complex and Mendelian eye diseases

    OpenAIRE

    Iglesias, Adriana I; Mishra, Aniket; Vitart, Veronique; Bykhovskaya, Yelena; Höhn, René; Springelkamp, Henriët; Cuellar-Partida, Gabriel; Gharahkhani, Puya; Bailey, Jessica N Cooke; Willoughby, Colin E; Li, Xiaohui; Yazar, Seyhan; Nag, Abhishek; Khawaja, Anthony P.; Polasek, Ozren

    2018-01-01

    Central corneal thickness (CCT) is a highly heritable trait associated with complex eye diseases such as keratoconus and glaucoma. We perform a genome-wide association meta-analysis of CCT and identify 19 novel regions. Pathway analyses uncover new, as well as supported the role of connective tissue-related, pathways. Remarkably, >20% of the CCT-loci are near or within Mendelian disorder genes. These included FBN1, ADAMTS2 and TGFB2 which associate with connective tissue disorders (Marfan,...

  6. The retinal nerve fibre layer thickness in glaucomatous hydrophthalmic eyes assessed by scanning laser polarimetry with variable corneal compensation in comparison with age-matched healthy children.

    Science.gov (United States)

    Hložánek, Martin; Ošmera, Jakub; Ležatková, Pavlína; Sedláčková, Petra; Filouš, Aleš

    2012-12-01

    To compare the thickness of the retinal nerve fibre layer (RNFL) in hydrophthalmic glaucomatous eyes in children with age-matched healthy controls using scanning laser polarimetry with variable corneal compensation (GDxVCC). Twenty hydrophthalmic eyes of 20 patients with the mean age of 10.64 ± 3.02 years being treated for congenital or infantile glaucoma were included in the analysis. Evaluation of RNFL thickness measured by GDxVCC in standard Temporal-Superior-Nasal-Inferior-Temporal (TSNIT) parameters was performed. The results were compared to TSNIT values of an age-matched control group of 120 healthy children published recently as referential values. The correlation between horizontal corneal diameter and RNFL thickness in hydrophthalmic eyes was also investigated. The mean ± SD values in TSNIT Average, Superior Average, Inferior Average and TSNIT SD in hydrophthalmic eyes were 52.3 ± 11.4, 59.7 ± 17.1, 62.0 ± 15.6 and 20.0 ± 7.8 μm, respectively. All these values were significantly lower compared to referential TSNIT parameters of age-matched healthy eyes (p = 0.021, p = 0.001, p = 0.003 and p = 0.018, respectively). A substantial number of hydrophthalmic eyes laid below the level of 5% probability of normality in respective TSNIT parameters: 30% of the eyes in TSNIT average, 50% of the eyes in superior average, 30% of the eyes in inferior average and 45% of the eyes in TSNIT SD. No significant correlation between enlarged corneal diameter and RNFL thickness was found. The mean values of all standard TSNIT parameters assessed using GDxVCC in hydrophthalmic glaucomatous eyes in children were significantly lower in comparison with referential values of healthy age-matched children. © 2011 The Authors. Acta Ophthalmologica © 2011 Acta Ophthalmologica Scandinavica Foundation.

  7. A comparative study of central corneal thickness (CCT) and intraocular pressure (IOP) in University of KwaZulu-Natal students of Black and Indian ethnicity*

    OpenAIRE

    Z. Sardiwalla; D. Moodley; T. Ndawonde; A. Madikizela; N. Ngobese; N. Thobela

    2012-01-01

    Thisstudy compared central corneal thickness (CCT) and intraocular pressure (IOP) of Black and Indian students from the University of Kwa-Zulu-Natal. Two hundred (100 Black and 100 Indi- an) participants of both genders aged 18-25 years (mean and standard deviation; 20.1±1.6 years) participated in this study. CCT and IOP were measured for the right eye of each participant using a Tono-Pachymeter (NT530P) and a Goldmann applanation tonometer (GAT) respectively. Data was analyzed with descr...

  8. Ethnic Variations in Central Corneal Thickness in a Rural Population in China: The Yunnan Minority Eye Studies.

    Science.gov (United States)

    Pan, Chen-Wei; Li, Jun; Zhong, Hua; Shen, Wei; Niu, Zhiqiang; Yuan, Yuansheng; Chen, Qin

    2015-01-01

    To describe the ethnic differences in central corneal thickness (CCT) in population-based samples of ethnic Bai, Yi and Han people living in rural China. 6504 adults (2119 ethnic Bai, 2202 ethnic Yi and 2183 ethnic Han) aged 50 years or older participated in the study. Each subject underwent standardized ocular examinations and interviewer-administered questionnaires for risk factor assessment. CCT was measured for both eyes using an ultrasound pachymeter. Regression and principal component analysis were performed to examine the relationship of ethnicity and other factors with CCT. The mean CCT readings were 536.4 ± 34.2 μm in ethnic Bai, 532.1 ± 32.1 μm in ethnic Yi and 529.6 ± 32.7 μm in ethnic Han adults (Pethnic groups. In multivariate linear regression models, increasing CCT was associated with younger age (Pethnicity, greater body mass index (PEthnicity contributed significantly to presence of thin cornea (60%; Pethnic groups. This study of more than 6500 multiethnic participants demonstrates significant ethnic variations in CCT, with Han ethnicity having the thinnest cornea compared with ethnic minorities. These data are essential to guide future multiethnic clinical trials on CCT-related ocular conditions such as glaucoma.

  9. Evaluation of the Endothelial Cell Density and the Central Corneal Thickness in Pseudoexfoliation Syndrome and Pseudoexfoliation Glaucoma

    Directory of Open Access Journals (Sweden)

    Bożydar T. Tomaszewski

    2014-01-01

    Full Text Available Purpose. Evaluation of central corneal thickness (CCT and endothelial cell density (ECD in patients with senile cataract and coexisting pseudoexfoliation (PEX syndrome with glaucoma (PEXG and without glaucoma using specular microscopy. Participants and Methods. The study included 122 patients (217 eyes. In this group of patients we identified 133 eyes with PEX syndrome (65 with glaucoma, 68 without glaucoma and 84 eyes without PEX syndrome. ECD and CCT were measured in each eye by specular microscopy. Results. ECD in eyes with PEX syndrome without glaucoma (2297 ± 359 cell/mm2 and in eyes with PEXG (2241 ± 363 cell/mm2 was lower than in the control group (2503 ± 262 cell/mm2 (P<0.001. CCT in eyes with PEXG (508.2 ± 32.6 μm was thinner than in eyes with PEX syndrome without glaucoma (529.7 ± 30.3 μm and control group (527.7 ± 29.4 μm (P<0.001. Conclusions. This research shows that in eyes with PEX syndrome, both with and without glaucoma, ECD was statistically significantly lower than in the control group. In patients with PEXG, CCT was statistically significantly thinner than in the PEX syndrome and control group.

  10. A portable device for measuring donor corneal transparency in eye banks.

    Science.gov (United States)

    Parekh, Mohit; Ferrari, Stefano; Ruzza, Alessandro; Pugliese, Mariarosaria; Ponzin, Diego; Salvalaio, Gianni

    2014-03-01

    To develop a portable device for measuring the donor corneal transparency and validate its efficacy for corneal evaluation in the eye-banks and for research. The transparency device (TD) has a light source, a detachable system for corneal insertion and a base for light transmission. The probe detects the transmitted light which is measured by a lux-meter. A contact lens was set as 'control' to reduce the light scattering concern, an empty petri-plate as 'blank' and the cornea as 'sample'. Two experts and non-experts (masked) observed the corneas for subjective analysis which was then compared using the TD. The parameters observed were scars, foreign-body, stromal-deformities, folds, thickness and opacity which were then converted to a relative overall percentage by the observer. Twenty corneas were evaluated for correlation, five tissues to obtain standard-deviation and twenty-four pairs for a comparative study. Experts mimicked the eye-banks with long-term experience while non-experts mimicked the emerging eye-banks. Subjective values by the experts closely resembled the measurements by TD. The average correlation between the experts and the non-experts to TD was 0.985 and 0.960 respectively. TD showed higher reproducibility than experts followed by the non-experts. The comparative study showed that increase in thickness reduces the transparency. TD is portable, easy, efficient, maintains sterility and less expensive hence the emerging eye-banks and researchers can use to raise their standards and evaluate the transparency for in vitro tests and comparative studies. The suitable transparency for the cornea deemed for clinical applications was found to be >75 %.

  11. Correlation between central corneal thickness and visual field defects, cup to disc ratio and retinal nerve fiber layer thickness in primary open angle glaucoma patients.

    Science.gov (United States)

    Sarfraz, Muhammad Haroon; Mehboob, Mohammad Asim; Haq, Rana Intisar Ul

    2017-01-01

    To evaluate the correlation between Central Corneal Thickness (CCT) and Visual Field (VF) defect parameters like Mean Deviation (MD) and Pattern Standard Deviation (PSD), Cup-to-Disc Ratio (CDR) and Retinal Nerve Fibre Layer Thickness (RNFL-T) in Primary Open-Angle Glaucoma (POAG) patients. This cross sectional study was conducted at Armed Forces Institute of Ophthalmology (AFIO), Rawalpindi from September 2015 to September 2016. Sixty eyes of 30 patients with diagnosed POAG were analysed. Correlation of CCT with other variables was studied. Mean age of study population was 43.13±7.54 years. Out of 30 patients, 19 (63.33%) were males and 11 (36.67%) were females. Mean CCT, MD, PSD, CDR and RNFL-T of study population was 528.57±25.47µm, -9.11±3.07, 6.93±2.73, 0.63±0.13 and 77.79±10.44µm respectively. There was significant correlation of CCT with MD, PSD and CDR (r=-0.52, pfield parameters like mean deviation and pattern standard deviation, as well as with cup-to-disc ratio. However, central corneal thickness had no significant relationship with retinal nerve fibre layer thickness.

  12. Scanning laser polarimetry retinal nerve fiber layer thickness measurements after LASIK.

    Science.gov (United States)

    Zangwill, Linda M; Abunto, Teresa; Bowd, Christopher; Angeles, Raymund; Schanzlin, David J; Weinreb, Robert N

    2005-02-01

    To compare retinal nerve fiber layer (RNFL) thickness measurements before and after LASIK. Cohort study. Twenty participants undergoing LASIK and 14 normal controls. Retinal nerve fiber layer thickness was measured before LASIK and approximately 3 months after surgery in one eye each of 20 patients using a scanning laser polarimeter (GDx Nerve Fiber Analyzer) with fixed corneal compensation (FCC), one with variable corneal compensation (GDx VCC), and optical coherence tomography (OCT). Fourteen normal controls also were tested at baseline and approximately 3 months later. Retinal nerve fiber layer thicknesses measured with the GDx FCC, GDx VCC, and OCT. At baseline, mean (95% confidence interval [CI]) RNFL thicknesses for the GDx FCC, GDx VCC, and OCT were 78.1 microm (72.2-83.9), 54.3 microm (52.7-56.0), and 96.8 microm (93.2-100.5), respectively. In both LASIK and control groups, there were no significant changes between baseline and follow-up examinations in GDx VCC and OCT RNFL thickness measurements globally or in the superior and inferior quadrants (mean change, FCC measurements between baseline and follow-up. In LASIK patients, significant reductions were observed in GDx FCC RNFL measurements. Average absolute values of the mean (95% CI) change in thickness were 12.4 microm (7.7-17.2), 15.3 microm (9.6-20.9), and 12.9 microm (7.6-18.1) for GDx FCC RNFL measurements superiorly, inferiorly, and globally, respectively (all Ps FCC RNFL thickness measurements after LASIK is a measurement artifact and is most likely due to erroneous compensation for corneal birefringence. With scanning laser polarimetry, it is mandatory to compensate individually for change in corneal birefringence after LASIK to ensure accurate RNFL assessment.

  13. Repeatability and interobserver reproducibility of Artemis-2 high-frequency ultrasound in determination of human corneal thickness

    Directory of Open Access Journals (Sweden)

    Ogbuehi KC

    2012-05-01

    Full Text Available Kelechi C Ogbuehi, Uchechukwu L OsuagwuOutpatient Clinic, Department of Optometry, King Saud University, Riyadh, Kingdom of Saudi ArabiaBackground: The purpose of this study was to assess the repeatability and limits of agreement of corneal thickness values measured by a high-frequency ultrasound (Artemis-2, hand-held ultrasound pachymeter (DGH-500 and a specular microscope (SP-3000P.Methods: Central corneal thickness (CCT was analyzed in this prospective randomized study that included 32 patients (18 men and 14 women aged 21–24 years. Measurements were obtained in two sessions, one week apart, by two examiners with three devices in a randomized order. Nine measurements were taken (three with each device on one randomly selected eye of each patient in each measurement session. The coefficient of repeatability and interobserver reproducibility for the values of each method were calculated. The limits of agreement between techniques were also evaluated.Results: There were no significant differences in CCT values between sessions for each of the three devices (P > 0.05. The repeatability coefficients for the Artemis-2 (±8 µm/±9 µm were superior to those of the SP-3000P (±9 µm/±11 µm and DGH 500 (±12 µm/±12 µm in session 1/session 2 respectively, while the interobserver reproducibility index (differences between session 1 and session 2 was superior for the SP-3000P (±17 µm with respect to DHG-500 (±29 µm and the Artemis-2 (±31 µm. In session 1 and session 2, the limits of agreement between the techniques were 35 µm to -31 µm and 34 to -20 µm, respectively, for DGH-500 versus Artemis-2, 73 µm to 3 µm and 60 µm to 9 µm for Artemis-2 versus SP-3000P, and 58 µm to 22 µm and 72 µm to 10 µm for DGH-500 versus SP-3000P comparisons. The DGH-500 and Artemis-2 gave similar values (P > 0.05 in both sessions, but both (Artemis-2 and DGH-500 values were significantly greater than that of the SP-3000P (P < 0.05 in both sessions

  14. Radiation transmission pipe thickness measurement system

    International Nuclear Information System (INIS)

    Higashi, Yasuhiko

    2010-01-01

    Fuji Electric Systems can be measured from the outer insulation of the transmission Characteristics and radiation detection equipment had been developed that can measure pipe wall thinning in plant and running, the recruitment of another three-beam calculation method by pipe thickness measurement system was developed to measure the thickness of the pipe side. This equipment has been possible to measure the thickness of the circumferential profile of the pipe attachment by adopting automatic rotation. (author)

  15. Reliability of corneal dynamic scheimpflug analyser measurements in virgin and post-PRK eyes.

    Science.gov (United States)

    Chen, Xiangjun; Stojanovic, Aleksandar; Hua, Yanjun; Eidet, Jon Roger; Hu, Di; Wang, Jingting; Utheim, Tor Paaske

    2014-01-01

    To determine the measurement reliability of CorVis ST, a dynamic Scheimpflug analyser, in virgin and post-photorefractive keratectomy (PRK) eyes and compare the results between these two groups. Forty virgin eyes and 42 post-PRK eyes underwent CorVis ST measurements performed by two technicians. Repeatability was evaluated by comparing three consecutive measurements by technician A. Reproducibility was determined by comparing the first measurement by technician A with one performed by technician B. Intraobserver and interobserver intraclass correlation coefficients (ICCs) were calculated. Univariate analysis of covariance (ANCOVA) was used to compare measured parameters between virgin and post-PRK eyes. The intraocular pressure (IOP), central corneal thickness (CCT) and 1st applanation time demonstrated good intraobserver repeatability and interobserver reproducibility (ICC ≧ 0.90) in virgin and post-PRK eyes. The deformation amplitude showed a good or close to good repeatability and reproducibility in both groups (ICC ≧ 0.88). The CCT correlated positively with 1st applanation time (r = 0.437 and 0.483, respectively, pPRK eyes, virgin eyes showed longer 1st applanation time (7.29 ± 0.21 vs. 6.96 ± 0.17 ms, pPRK eyes. There were differences in 1st applanation time and deformation amplitude between virgin and post-PRK eyes, which may reflect corneal biomechanical changes occurring after the surgery in the latter.

  16. Espesor corneal y variables epidemiológicas y fisiológicas en población de riesgo de glaucoma Corneal thickness and the epidemiological and physiological variables seen in the glaucoma risk population

    Directory of Open Access Journals (Sweden)

    Idalia Triana Casado

    2012-12-01

    Full Text Available Objetivo: caracterizar el espesor corneal central en pacientes con factores de riesgo de glaucoma crónico simple. Métodos: se realizó un estudio epidemiológico, observacional, descriptivo y longitudinal prospectivo, en el Servicio de Glaucoma del Hospital "Dr. Salvador Allende" durante el año 2010. El universo estuvo constituido por 1 238 pacientes que acudieron a la consulta de oftalmología por síntomas astenópicos. La muestra, aplicados los criterios de inclusión y exclusión, quedó conformada por 656 pacientes con factores de riesgo de la enfermedad, de estos se desecharon 19 por una diferencia entre los ojos de 10 µm o más de espesor corneal. Las variables analizadas fueron: espesor corneal, edad, sexo, color de la piel y presión intraocular. Resultados: de los pacientes con factores de riesgo de glaucoma, predominaron aquellos entre 50 y 59 años de edad (22,76 %, masculinos (60,28 % y de piel no blanca (57,29 %. El espesor corneal estuvo disminuido (61,85 % y la presión intraocular aumentada (55,41 %, aún con ajuste (46,93 %. Conclusiones: la disminución del espesor corneal estuvo relacionada con la edad, el sexo femenino, la piel no blanca y el aumento de la presión intraocular en aquellos pacientes sospechosos de glaucoma.Objective: to characterize the central corneal thickness seen in patients with simple chronic glaucoma risk factors. Methods: a prospective longitudinal, descriptive, observational, and epidemiological study was conducted in the Glaucoma Service of “Dr. Salvador Allende” hospital during 2010. The universe of study was made up of 1 238 patients that went to the ophthalmological service due to asthenopic symptoms. Taking the inclusion and exclusion criteria into account, the final sample was composed by 656 patients with glaucoma risk factors, 19 of whom were excluded because of 10 µm and over difference in the corneal thickness between the eyes. The analyzed variables were corneal thickness, age

  17. Modification of the laser triangulation method for measuring the thickness of optical layers

    Science.gov (United States)

    Khramov, V. N.; Adamov, A. A.

    2018-04-01

    The problem of determining the thickness of thin films by the method of laser triangulation is considered. An expression is derived for the film thickness and the distance between the focused beams on the photo detector. The possibility of applying the chosen method for measuring thickness is in the range [0.1; 1] mm. We could resolve 2 individual light marks for a minimum film thickness of 0.23 mm. We resolved with the help of computer processing of photos with a resolution of 0.10 mm. The obtained results can be used in ophthalmology for express diagnostics during surgical operations on the corneal layer.

  18. Corneal Laceration

    Medline Plus

    Full Text Available ... by something sharp flying into the eye. It can also be caused by something striking the eye ... If the corneal laceration is deep enough it can cause a full thickness laceration. This is when ...

  19. Comparison of corneal measurements in keratoconic eyes using rotating Scheimpflug camera and scanning-slit topography

    Directory of Open Access Journals (Sweden)

    Mohammad Naderan

    2015-04-01

    Full Text Available AIM: To compare the anterior segment measurements obtained by rotating Scheimpflug camera (Pentacam and Scanning-slit topography (Orbscan IIz in keratoconic eyes. METHODS: A total of 121 patients, 71 males (58.7% and 50 females (41.3% (214 eyes with the diagnosis of keratoconus (KC were enrolled in this study. Following diagnosis of KC by slit-lamp biomicroscopic examination, central corneal thickness (CCT, thinnest corneal thickness (TCT, anterior chamber depth (ACD, and pupil diameter (PD were measured by a single examiner using successive instrumentation by Pentacam and Orbscan. RESULTS: There was no significant difference between the two instruments for the measurement of CCT and TCT. In contrast, scanning-slit topography measured ACD (3.46±0.40 mm vs. 3.38±0.33 mm, P=0.019 and PD (4.97±1.26 mm vs 4.08±1.19 mm, P<0.001 significantly larger than rotating Scheimpflug camera. The two devices made similar measurements for CCT (95% CI: -2.94 to 5.06, P=0.602. However, the mean difference for TCT was -6.28 (95% CI: -10.51 to -2.06, P=0.004 showing a thinner measurement by Orbscan than by Pentacam. In terms of the ACD, the mean difference was 0.08 mm (95% CI: 0.04 to 0.12, P<0.001 with Orbscan giving a slightly larger value than Pentacam. Similarly, Orbscan measurement for PD was longer than Pentacam (95% CI: 0.68 to 1.08, P<0.001. CONCLUSION: A good agreement was found between Pentacam and Orbscan concerning CCT measurement while comparing scanning-slit topography and rotating Scheimpflug camera there was an underestimation for TCT and overestimation for ACD and PD.

  20. Comparison of central corneal thickness with four noncontact devices: An agreement analysis of swept-source technology

    Directory of Open Access Journals (Sweden)

    Erhan Ozyol

    2017-01-01

    Full Text Available Purpose: The purpose of this study was to compare the central corneal thickness (CCT measurements of four noncontact devices in healthy eyes. Materials and Methods: In a sample of 45 healthy controls, CCT was measured using an optical biometer (IOLMaster 700 based on swept-source optical coherence tomography (SS-OCT, high-resolution rotating Scheimpflug camera system (Pentacam HR, spectral-domain OCT (SD-OCT device with an anterior segment module (Spectralis, and noncontact pachymetry (NCP device (Topcon TRK-2P. Agreement among the devices was analyzed using mean differences (i.e., bias and Bland–Altman analysis with 95% limits of agreement (LoA. Results: Mean CCT measurements were 537.5 ± 47.5 μm for SS-OCT optical biometer, 532.3 ± 43.8 μm for Scheimpflug system, 521.3 ± 44.7 μm for SD-OCT device, and 518.0 ± 43.1 μm for NCP (P < 0.001. The SD-OCT device and NCP showed the closest agreement, with a bias of 2.6 μm (95% LoA, −3.6–8.8 μm, whereas the SS-OCT optical biometer and NCP showed the least agreement, with a bias of 18.7 μm (95% LoA, −2.1–39.5 μm. Bias was 16.1 μm (95% LoA, −3.1–35.3 μm for SS-OCT optical biometer and SD-OCT, 5.1 μm (95% LoA, −6.8–17.0 μm for SS-OCT optical biometer and Scheimpflug system, 10.9 μm (95% LoA, −15.1–36.9 μm for SD-OCT device and Scheimpflug system, and 13.6 μm (95% LoA, −5–32.2 μm for Scheimpflug system and NCP. Conclusions: SS-OCT optical biometer overestimates CCT measurements compared to Scheimpflug system, SD-OCT device, and NCP. Given mean differences and range variations in CCT measurements between devices, SS-OCT optical biometer and Scheimpflug system are interchangeable as are SD-OCT and NCP.

  1. Comparison of central corneal thickness with four noncontact devices: An agreement analysis of swept-source technology.

    Science.gov (United States)

    Ozyol, Erhan; Özyol, Pelin

    2017-06-01

    The purpose of this study was to compare the central corneal thickness (CCT) measurements of four noncontact devices in healthy eyes. In a sample of 45 healthy controls, CCT was measured using an optical biometer (IOLMaster 700) based on swept-source optical coherence tomography (SS-OCT), high-resolution rotating Scheimpflug camera system (Pentacam HR), spectral-domain OCT (SD-OCT) device with an anterior segment module (Spectralis), and noncontact pachymetry (NCP) device (Topcon TRK-2P). Agreement among the devices was analyzed using mean differences (i.e., bias) and Bland-Altman analysis with 95% limits of agreement (LoA). Mean CCT measurements were 537.5 ± 47.5 μm for SS-OCT optical biometer, 532.3 ± 43.8 μm for Scheimpflug system, 521.3 ± 44.7 μm for SD-OCT device, and 518.0 ± 43.1 μm for NCP (P < 0.001). The SD-OCT device and NCP showed the closest agreement, with a bias of 2.6 μm (95% LoA, -3.6-8.8 μm), whereas the SS-OCT optical biometer and NCP showed the least agreement, with a bias of 18.7 μm (95% LoA, -2.1-39.5 μm). Bias was 16.1 μm (95% LoA, -3.1-35.3 μm) for SS-OCT optical biometer and SD-OCT, 5.1 μm (95% LoA, -6.8-17.0 μm) for SS-OCT optical biometer and Scheimpflug system, 10.9 μm (95% LoA, -15.1-36.9 μm) for SD-OCT device and Scheimpflug system, and 13.6 μm (95% LoA, -5-32.2 μm) for Scheimpflug system and NCP. SS-OCT optical biometer overestimates CCT measurements compared to Scheimpflug system, SD-OCT device, and NCP. Given mean differences and range variations in CCT measurements between devices, SS-OCT optical biometer and Scheimpflug system are interchangeable as are SD-OCT and NCP.

  2. Dry eyes and corneal sensation after laser in situ keratomileusis with femtosecond laser flap creation Effect of hinge position, hinge angle, and flap thickness.

    Science.gov (United States)

    Mian, Shahzad I; Li, Amy Y; Dutta, Satavisha; Musch, David C; Shtein, Roni M

    2009-12-01

    To determine whether corneal sensation and dry-eye signs and symptoms after myopic laser in situ keratomileusis (LASIK) surgery with a femtosecond laser are affected by varying hinge position, hinge angle, or flap thickness. University-based academic practice, Ann Arbor, Michigan, USA. This prospective randomized contralateral-eye study evaluated eyes after bilateral myopic LASIK with a femtosecond laser (IntraLase). Superior and temporal hinge positions, 45-degree and 90-degree hinge angles, and 100 microm and 130 microm corneal flap thicknesses were compared. Postoperative follow-up at 1 week and 1, 3, 6, and 12 months included central Cochet-Bonnet esthesiometry, the Ocular Surface Disease Index questionnaire, a Schirmer test with anesthesia, tear breakup time (TBUT), corneal fluorescein staining, and conjunctival lissamine green staining. The study evaluated 190 consecutive eyes (95 patients). Corneal sensation was reduced at all postoperative visits, with improvement over 12 months (P<.001). There was no difference in corneal sensation between the different hinge positions, angles, or flap thicknesses at any time point. The overall ocular surface disease index score was increased at 1 week, 1 month, and 3 months (P<.0001, P<.0001, and P = .046, respectively). The percentage of patients with a TBUT longer than 10 seconds was significantly lower at 1 week and 1 month (P<.0001). Dry-eye syndrome after myopic LASIK with a femtosecond laser was mild and improved after 3 months. Corneal flap hinge position, hinge angle, and thickness had no effect on corneal sensation or dry-eye syndrome.

  3. Card controlled beta backscatter thickness measuring instrument

    International Nuclear Information System (INIS)

    Schlesinger, J.

    1978-01-01

    An improved beta backscatter instrument for the nondestructive measurement of the thickness of thin coatings on a substrate is described. Included therein is the utilization of a bank of memory stored data representative of isotope, substrate, coating material and thickness range characteristics in association with a control card having predetermined indicia thereon selectively representative of a particular isotope, substrate material, coating material and thickness range for conditioning electronic circuit means by memory stored data selected in accord with the predetermined indicia on a control card for converting backscattered beta particle counts into indicia of coating thickness

  4. Ocular biometry and central corneal thickness in children: a hospital-based study

    Directory of Open Access Journals (Sweden)

    Adem Gul

    2014-06-01

    Full Text Available Objetivo: Investigar a distribuição do comprimento axial, profundidade da câmara anterior, espessura do cristalino, profundidade da câmara vítrea e espessura corneal central em crianças em diferentes faixas etárias. Métodos: Foram estudados 364 olhos de 182 crianças entre 1 e 12 anos de idade. O comprimento axial, a profundidade da câmara anterior , a espessura do cristalino e a profundidade da câmara vítrea foram medidos por biometria ultrassônica. A espessura corneal central foi medida por paquimetria ultrassônica em todas as crianças. Resultados: A idade média foi de 6,54 ± 3,42 anos. O comprimento axial foi 20,95 mm no grupo de 1-2 anos de idade e 22,95 mm no grupo de 11-12 anos de idade. A espessura corneal central foi 556 µm no grupo de 1-2 anos de idade e 555 µm no grupo de 11-12 anos de idade. A profundidade da câmara anterior média e profundidade da câmara vítrea aumentou com a idade (3,06 mm a 3,44 mm de profundidade da câmara anterior, 13,75 mm a 15,99 mm de profundidade da câmara vítrea e da espessura do cristalino diminuiu com o aumento da idade (3,67 mm a 3,51 mm. Conclusões: Em nosso estudo, os valores do comprimento axial aumentou com a idade e atingiu os níveis adultos aos 9-10 anos de idade. A espessura do cristalino diminuiu gradualmente até os 12 anos de idade. As medições de espessura corneal central não seguiu um algoritmo linear.

  5. Reliability of corneal dynamic scheimpflug analyser measurements in virgin and post-PRK eyes.

    Directory of Open Access Journals (Sweden)

    Xiangjun Chen

    Full Text Available PURPOSE: To determine the measurement reliability of CorVis ST, a dynamic Scheimpflug analyser, in virgin and post-photorefractive keratectomy (PRK eyes and compare the results between these two groups. METHODS: Forty virgin eyes and 42 post-PRK eyes underwent CorVis ST measurements performed by two technicians. Repeatability was evaluated by comparing three consecutive measurements by technician A. Reproducibility was determined by comparing the first measurement by technician A with one performed by technician B. Intraobserver and interobserver intraclass correlation coefficients (ICCs were calculated. Univariate analysis of covariance (ANCOVA was used to compare measured parameters between virgin and post-PRK eyes. RESULTS: The intraocular pressure (IOP, central corneal thickness (CCT and 1st applanation time demonstrated good intraobserver repeatability and interobserver reproducibility (ICC ≧ 0.90 in virgin and post-PRK eyes. The deformation amplitude showed a good or close to good repeatability and reproducibility in both groups (ICC ≧ 0.88. The CCT correlated positively with 1st applanation time (r = 0.437 and 0.483, respectively, p<0.05 and negatively with deformation amplitude (r = -0.384 and -0.375, respectively, p<0.05 in both groups. Compared to post-PRK eyes, virgin eyes showed longer 1st applanation time (7.29 ± 0.21 vs. 6.96 ± 0.17 ms, p<0.05 and lower deformation amplitude (1.06 ± 0.07 vs. 1.17 ± 0.08 mm, p < 0.05. CONCLUSIONS: CorVis ST demonstrated reliable measurements for CCT, IOP, and 1st applanation time, as well as relatively reliable measurement for deformation amplitude in both virgin and post-PRK eyes. There were differences in 1st applanation time and deformation amplitude between virgin and post-PRK eyes, which may reflect corneal biomechanical changes occurring after the surgery in the latter.

  6. Genomic locus modulating corneal thickness in the mouse identifies POU6F2 as a potential risk of developing glaucoma.

    Directory of Open Access Journals (Sweden)

    Rebecca King

    2018-01-01

    Full Text Available Central corneal thickness (CCT is one of the most heritable ocular traits and it is also a phenotypic risk factor for primary open angle glaucoma (POAG. The present study uses the BXD Recombinant Inbred (RI strains to identify novel quantitative trait loci (QTLs modulating CCT in the mouse with the potential of identifying a molecular link between CCT and risk of developing POAG. The BXD RI strain set was used to define mammalian genomic loci modulating CCT, with a total of 818 corneas measured from 61 BXD RI strains (between 60-100 days of age. The mice were anesthetized and the eyes were positioned in front of the lens of the Phoenix Micron IV Image-Guided OCT system or the Bioptigen OCT system. CCT data for each strain was averaged and used to QTLs modulating this phenotype using the bioinformatics tools on GeneNetwork (www.genenetwork.org. The candidate genes and genomic loci identified in the mouse were then directly compared with the summary data from a human POAG genome wide association study (NEIGHBORHOOD to determine if any genomic elements modulating mouse CCT are also risk factors for POAG.This analysis revealed one significant QTL on Chr 13 and a suggestive QTL on Chr 7. The significant locus on Chr 13 (13 to 19 Mb was examined further to define candidate genes modulating this eye phenotype. For the Chr 13 QTL in the mouse, only one gene in the region (Pou6f2 contained nonsynonymous SNPs. Of these five nonsynonymous SNPs in Pou6f2, two resulted in changes in the amino acid proline which could result in altered secondary structure affecting protein function. The 7 Mb region under the mouse Chr 13 peak distributes over 2 chromosomes in the human: Chr 1 and Chr 7. These genomic loci were examined in the NEIGHBORHOOD database to determine if they are potential risk factors for human glaucoma identified using meta-data from human GWAS. The top 50 hits all resided within one gene (POU6F2, with the highest significance level of p = 10-6 for

  7. Model SH intelligent instrument for thickness measuring

    International Nuclear Information System (INIS)

    Liu Juntao; Jia Weizhuang; Zhao Yunlong

    1995-01-01

    The authors introduce Model SH Intelligent Instrument for thickness measuring by using principle of beta back-scattering and its application range, features, principle of operation, system design, calibration and specifications

  8. Greenland Radar Ice Sheet Thickness Measurements

    Data.gov (United States)

    National Aeronautics and Space Administration — Two 150-MHz coherent radar depth sounders were developed and flown over the Greenland ice sheet to obtain ice thickness measurements in support of PARCA...

  9. Distribution of central corneal thickness and its association with ocular parameters in a large central European cohort: the Gutenberg health study.

    Directory of Open Access Journals (Sweden)

    Esther M Hoffmann

    Full Text Available MAIN OBJECTIVE: To evaluate the distribution of central corneal thickness (CCT in a large German cohort and to analyse its relationship with intraocular pressure and further ocular factors. DESIGN: Population-based, prospective, cohort study. METHODS: The Gutenberg Health Study (GHS cohort included 4,698 eligible enrollees of 5,000 subjects (age range 35-74 years who participated in the survey from 2007 to 2008. All participants underwent an ophthalmological examination including slitlamp biomicroscopy, intraocular pressure measurement, central corneal thickness measurement, fundus examination, and were given a questionnaire regarding glaucoma history. Furthermore, all subjects underwent fundus photography and visual field testing using frequency doubling perimetry. RESULTS: Mean CCT was 557.3 ± 34.3 µm (male and 551.6±35.2 µm in female subjects (Mean CCT from right and left eyes. Younger male participants (35-44 years presented slightly thicker CCT than those older. We noted a significant CCT difference of 4 µm between right and left eyes, but a high correlation between eyes (Wilcoxon test for related samples: p<0.0001. Univariable linear regression stratified by gender showed that IOP was correlated with CCT (p<0.0001. A 10 µm increase in CCT led to an increase in IOP between 0.35-0.38 mm Hg, depending on the eye and gender. Multivariable linear regression analysis revealed correlations between gender, spherical equivalent (right eyes, and CCT (p<.0001 and p=0.03, respectively. CONCLUSIONS: We observed positive correlations between CCT and IOP and gender. CCT was not correlated with age, contact lens wear, positive family history for glaucoma, lens status, or iris colour.

  10. Uncertainty estimation of ultrasonic thickness measurement

    International Nuclear Information System (INIS)

    Yassir Yassen, Abdul Razak Daud; Mohammad Pauzi Ismail; Abdul Aziz Jemain

    2009-01-01

    The most important factor that should be taken into consideration when selecting ultrasonic thickness measurement technique is its reliability. Only when the uncertainty of a measurement results is known, it may be judged if the result is adequate for intended purpose. The objective of this study is to model the ultrasonic thickness measurement function, to identify the most contributing input uncertainty components, and to estimate the uncertainty of the ultrasonic thickness measurement results. We assumed that there are five error sources significantly contribute to the final error, these sources are calibration velocity, transit time, zero offset, measurement repeatability and resolution, by applying the propagation of uncertainty law to the model function, a combined uncertainty of the ultrasonic thickness measurement was obtained. In this study the modeling function of ultrasonic thickness measurement was derived. By using this model the estimation of the uncertainty of the final output result was found to be reliable. It was also found that the most contributing input uncertainty components are calibration velocity, transit time linearity and zero offset. (author)

  11. Glue Film Thickness Measurements by Spectral Reflectance

    International Nuclear Information System (INIS)

    Marshall, B.R.

    2010-01-01

    Spectral reflectance was used to determine the thickness of thin glue layers in a study of the effect of the glue on radiance and reflectance measurements of shocked-tin substrates attached to lithium fluoride windows. Measurements based on profilometry of the components were found to be inaccurate due to flatness variations and deformation of the tin substrate under pressure during the gluing process. The accuracy of the spectral reflectance measurements were estimated to be ±0.5 (micro)m, which was sufficient to demonstrate a convincing correlation between glue thickness and shock-generated light.

  12. Glue Film Thickness Measurements by Spectral Reflectance

    Energy Technology Data Exchange (ETDEWEB)

    B. R. Marshall

    2010-09-20

    Spectral reflectance was used to determine the thickness of thin glue layers in a study of the effect of the glue on radiance and reflectance measurements of shocked-tin substrates attached to lithium fluoride windows. Measurements based on profilometry of the components were found to be inaccurate due to flatness variations and deformation of the tin substrate under pressure during the gluing process. The accuracy of the spectral reflectance measurements were estimated to be ±0.5 μm, which was sufficient to demonstrate a convincing correlation between glue thickness and shock-generated light.

  13. Rapid Measurement of Nanoparticle Thickness Profiles

    International Nuclear Information System (INIS)

    Katz-Boon, Hadas; Rossouw, Chris J.; Dwyer, Christian; Etheridge, Joanne

    2013-01-01

    A method to measure the thickness of a single-crystal nanoparticle in the direction parallel to the incident beam from annular dark field scanning transmission electron microscope (ADF-STEM) images is reported, providing a map of thickness versus position across the nanoparticle—a ‘thickness profile’ image. The method is rapid and hence suitable for surveying large numbers of nanoparticles. The method measures the intensity scattered to a characterised ADF detector and compares this to the incident beam intensity, to obtain a normalized ADF image. The normalised intensity is then converted to thickness via dynamical ADF image simulations. The method is accurate within 10% and the precision is dominated primarily by ‘shot noise’. Merits and limitations of this method are discussed. A method to calibrate the response function of the ADF detector without external equipment is also described, which is applicable to the entire range of gain and background settings. -- Highlights: ► A method is developed to convert ADF-STEM images to ‘thickness profile’ images. ► It is applicable in particles survey, facets determination and discrete tomography. ► A method to calibrate the response of the ADF detector is described. ► The response in analysed across a range of conditions. ► Dynamical ADF image simulations are presented, demonstrating intensity vs. thickness dependence.

  14. Study on the ionization chamber for thickness measurement

    International Nuclear Information System (INIS)

    Xue Shili; Miao Qiangwen

    1988-01-01

    The principle, construction and performances of ionization chambers for measuring the thickness of metal and nonmetal materials are introduced. With them the thickness of thin materials (thickness ranging from 10 to 6000 g/m 2 ), the surface layer thickness of composed materials and the thickness of steel plate (thickness ranging from 0 to 32 kg/m 2 ) are measured effectively

  15. Influence of corneal power on circumpapillary retinal nerve fiber layer and optic nerve head measurements by spectral-domain optical coherence tomography

    Directory of Open Access Journals (Sweden)

    Kazunori Hirasawa

    2017-09-01

    Full Text Available AIM: To evaluate the influence of corneal power on circumpapillary retinal nerve fiber layer (cpRNFL and optic nerve head (ONH measurements by spectral-domain optical coherence tomography (SD-OCT. METHODS: Twenty-five eyes of 25 healthy participants (mean age 23.6±3.6y were imaged by SD-OCT using horizontal raster scans. Disposable soft contact lenses of different powers (from −11 to +5 diopters including 0 diopter were worn to induce 2-diopter changes in corneal power. Differences in the cpRNFL and ONH measurements per diopter of change in corneal power were analyzed. RESULTS: As corneal power increased by 1 diopter, total and quadrant cpRNFL thicknesses, except for the nasal sector, decreased by −0.19 to −0.32 μm (P<0.01. Furthermore, the disc, cup, and rim areas decreased by −0.017, −0.007, and −0.015 mm2, respectively (P<0.001; the cup and rim volumes decreased by −0.0013 and −0.006 mm3, respectively (P<0.01; and the vertical and horizontal disc diameters decreased by −0.006 and −0.007 mm, respectively (P<0.001. CONCLUSION: For more precise OCT imaging, the ocular magnification should be corrected by considering both the axial length and corneal power. However, the effect of corneal power changes on cpRNFL thickness and ONH topography are small when compare with those of the axial length.

  16. Precision of anterior and posterior corneal curvature measurements taken with the Oculus Pentacam

    Directory of Open Access Journals (Sweden)

    Elizabeth Chetty

    2016-06-01

    Full Text Available In the era of rapid advances in technology, new ophthalmic instruments are constantly influencing health sciences and necessitating investigations of the accuracy and precision of the new technology. The Oculus Pentacam (70700 has been available for some time now and numerous studies have investigated the precision of some of the parameters that the Pentacam is capable of measuring. Unfortunately some of these studies fall short in confusing the meaning of accuracy and precision and in not being able to analyse the data correctly or completely. The aim of this study was to investigate the precision of the anterior and posterior corneal curvature measurements taken with the Oculus Pentacam (70700 holistically with sound multivariate statistical methods. Twenty successive Pentacam measurements were taken over three different measuring sessions on one subject. Keratometric data for both the anterior and posterior corneal surfaces were analysed using multivariate statistics to determine the precision of the Oculus Pentacam. This instrument was found to have good precision both clinically and statistically for anterior corneal measurements but only good clinical precision for the posterior corneal surface. Key words: Oculus Pentacam; keratometric variation; corneal curvature; multivariate statistics

  17. Precision of hyaline cartilage thickness measurements

    Energy Technology Data Exchange (ETDEWEB)

    Jonsson, K.; Buckwalter, K.; Helvie, M.; Niklason, L.; Martel, W. (Univ. of Michigan Hospitals, Ann Arbor, MI (United States). Dept. of Radiology)

    1992-05-01

    Measurement of cartilage thickness in vivo is an important indicator of the status of a joint as the various degenerative and inflammatory arthritides directly affect the condition of the cartilage. In order to assess the precision of thickness measurements of hyaline articular cartilage, we undertook a pilot study using MR imaging, plain radiography, and ultrasonography (US). We measured the cartilage of the hip and knee joints in 10 persons (4 healthy volunteers and 6 patients). The joints in each patient were examined on two separate occasions using each modality. In the hips a swell as the knee joints, the most precise measuring method was plain film radiography. For radiographs of the knees obtained in the standing position, the coefficient of variation was 6.5%; in the hips this figure was 6.34%. US of the knees and MR imaging of the hips were the second best modalities in the measurement of cartilage thickness. In addition, MR imaging enabled the most complete visualization of the joint cartilage. (orig.).

  18. Effect of central corneal thickness on intraocular pressure and comparison of Topcon CT-80 non-contact tonometry with Goldmann applanation tonometry.

    Science.gov (United States)

    Mansoori, Tarannum; Balakrishna, Nagalla

    2018-03-01

    To compare intraocular pressure (IOP) measurements obtained with the Topcon CT-80 non-contact tonometer (NCT) and Goldmann applanation tonometer (GAT), in different ranges of IOP in normal and glaucoma subjects, and to assess the influence of central corneal thickness (CCT) on the IOP measurements in Asian Indian eyes. Four hundred and two eyes of 402 subjects (193 newly diagnosed primary open angle glaucoma [POAG] and 209 normal) were enrolled for this prospective study. For each eye, IOP was measured with GAT by a glaucoma specialist and NCT by a trained optometrist. The IOP values were compared among the tonometers in the three different IOP ranges (≤ 12 mmHg, 13-20 mmHg and ≥ 21 mmHg) using Bland-Altman graphs. Correlation between GAT and NCT was assessed by Pearson correlation co-efficient. CCT was measured with ultrasound pachymetry and its correlation with GAT and NCT was analysed using linear regression analysis. The mean paired difference of IOP between NCT and GAT was 1.556 ± 2.69 mmHg (r = 0.26, p = 0.006) at IOP range of ≤ 12 mmHg, -1.665 ± 2.6 mmHg (r = 0.51, p tonometer and that the IOP readings obtained with these tonometers are not interchangeable. © 2017 Optometry Australia.

  19. Corneal Vibrations during Intraocular Pressure Measurement with an Air-Puff Method

    Directory of Open Access Journals (Sweden)

    Robert Koprowski

    2018-01-01

    Full Text Available Introduction. The paper presents a commentary on the method of analysis of corneal vibrations occurring during eye pressure measurements with air-puff tonometers, for example, Corvis. The presented definition and measurement method allow for the analysis of image sequences of eye responses—cornea deformation. In particular, the outer corneal contour and sclera fragments are analysed, and 3D reconstruction is performed. Methods. On this basis, well-known parameters such as eyeball reaction or corneal response are determined. The next steps of analysis allow for automatic and reproducible separation of four different corneal vibrations. These vibrations are associated with (1 the location of the maximum of cornea deformation; (2 the cutoff area measured in relation to the cornea in a steady state; (3 the maximum of peaks occurring between applanations; and (4 the other characteristic points of the corneal contour. Results. The results obtained enable (1 automatic determination of the amplitude of vibrations; (2 determination of the frequency of vibrations; and (3 determination of the correlation between the selected types of vibrations. Conclusions. These are diagnostic features that can be directly applied clinically for new and archived data.

  20. Common genetic variants near the Brittle Cornea Syndrome locus ZNF469 influence the blinding disease risk factor central corneal thickness.

    Directory of Open Access Journals (Sweden)

    Yi Lu

    2010-05-01

    Full Text Available Central corneal thickness (CCT, one of the most highly heritable human traits (h(2 typically>0.9, is important for the diagnosis of glaucoma and a potential risk factor for glaucoma susceptibility. We conducted genome-wide association studies in five cohorts from Australia and the United Kingdom (total N = 5058. Three cohorts were based on individually genotyped twin collections, with the remaining two cohorts genotyped on pooled samples from singletons with extreme trait values. The pooled sample findings were validated by individual genotyping the pooled samples together with additional samples also within extreme quantiles. We describe methods for efficient combined analysis of the results from these different study designs. We have identified and replicated quantitative trait loci on chromosomes 13 and 16 for association with CCT. The locus on chromosome 13 (nearest gene FOXO1 had an overall meta-analysis p-value for all the individually genotyped samples of 4.6x10(-10. The locus on chromosome 16 was associated with CCT with p = 8.95x10(-11. The nearest gene to the associated chromosome 16 SNPs was ZNF469, a locus recently implicated in Brittle Cornea Syndrome (BCS, a very rare disorder characterized by abnormal thin corneas. Our findings suggest that in addition to rare variants in ZNF469 underlying CCT variation in BCS patients, more common variants near this gene may contribute to CCT variation in the general population.

  1. Comparative Study of Anterior Eye Segment Measurements with Spectral Swept-Source and Time-Domain Optical Coherence Tomography in Eyes with Corneal Dystrophies.

    Science.gov (United States)

    Nowinska, Anna K; Teper, Sławomir J; Janiszewska, Dominika A; Lyssek-Boron, Anita; Dobrowolski, Dariusz; Koprowski, Robert; Wylegala, Edward

    2015-01-01

    To compare anterior eye segment measurements and morphology obtained with two optical coherence tomography systems (TD OCT, SS OCT) in eyes with corneal dystrophies (CDs). Fifty healthy volunteers (50 eyes) and 54 patients (96 eyes) diagnosed with CD (epithelial basement membrane dystrophy, EBMD = 12 eyes; Thiel-Behnke CD = 6 eyes; lattice CD TGFBI type = 15 eyes; granular CD type 1 = 7 eyes, granular CD type 2 = 2 eyes; macular CD = 23 eyes; and Fuchs endothelial CD = 31 eyes) were recruited for the study. Automated and manual central corneal thickness (aCCT, mCCT), anterior chamber depth (ACD), and nasal and temporal trabecular iris angle (nTIA, tTIA) were measured and compared with Bland-Altman plots. Good agreement between the TD and SS OCT measurements was demonstrated for mCCT and aCCT in normal individuals and for mCCT in the CDs group. The ACD, nTIA, and tTIA measurements differed significantly in both groups. TBCD, LCD, and FECD caused increased CCT. MCD caused significant corneal thinning. FECD affected all analyzed parameters. Better agreement between SS OCT and TD OCT measurements was demonstrated in normal individuals compared to the CDs group. OCT provides comprehensive corneal deposits analysis and demonstrates the association of CD with CCT, ACD, and TIA measurements.

  2. Comparative Study of Anterior Eye Segment Measurements with Spectral Swept-Source and Time-Domain Optical Coherence Tomography in Eyes with Corneal Dystrophies

    Directory of Open Access Journals (Sweden)

    Anna K. Nowinska

    2015-01-01

    Full Text Available Purpose. To compare anterior eye segment measurements and morphology obtained with two optical coherence tomography systems (TD OCT, SS OCT in eyes with corneal dystrophies (CDs. Methods. Fifty healthy volunteers (50 eyes and 54 patients (96 eyes diagnosed with CD (epithelial basement membrane dystrophy, EBMD = 12 eyes; Thiel-Behnke CD = 6 eyes; lattice CD TGFBI type = 15 eyes; granular CD type 1 = 7 eyes, granular CD type 2 = 2 eyes; macular CD = 23 eyes; and Fuchs endothelial CD = 31 eyes were recruited for the study. Automated and manual central corneal thickness (aCCT, mCCT, anterior chamber depth (ACD, and nasal and temporal trabecular iris angle (nTIA, tTIA were measured and compared with Bland-Altman plots. Results. Good agreement between the TD and SS OCT measurements was demonstrated for mCCT and aCCT in normal individuals and for mCCT in the CDs group. The ACD, nTIA, and tTIA measurements differed significantly in both groups. TBCD, LCD, and FECD caused increased CCT. MCD caused significant corneal thinning. FECD affected all analyzed parameters. Conclusions. Better agreement between SS OCT and TD OCT measurements was demonstrated in normal individuals compared to the CDs group. OCT provides comprehensive corneal deposits analysis and demonstrates the association of CD with CCT, ACD, and TIA measurements.

  3. Retinal nerve fiber layer measurements by scanning laser polarimetry with enhanced corneal compensation in healthy subjects.

    Science.gov (United States)

    Rao, Harsha L; Venkatesh, Chirravuri R; Vidyasagar, Kelli; Yadav, Ravi K; Addepalli, Uday K; Jude, Aarthi; Senthil, Sirisha; Garudadri, Chandra S

    2014-12-01

    To evaluate the (i) effects of biological (age and axial length) and instrument-related [typical scan score (TSS) and corneal birefringence] parameters on the retinal nerve fiber layer (RNFL) measurements and (ii) repeatability of RNFL measurements with the enhanced corneal compensation (ECC) protocol of scanning laser polarimetry (SLP) in healthy subjects. In a cross-sectional study, 140 eyes of 73 healthy subjects underwent RNFL imaging with the ECC protocol of SLP. Linear mixed modeling methods were used to evaluate the effects of age, axial length, TSS, and corneal birefringence on RNFL measurements. One randomly selected eye of 48 subjects from the cohort underwent 3 serial scans during the same session to determine the repeatability. Age significantly influenced all RNFL measurements. RNFL measurements decreased by 1 µm for every decade increase in age. TSS affected the overall average RNFL measurement (β=-0.62, P=0.003), whereas residual anterior segment retardance affected the superior quadrant measurement (β=1.14, P=0.01). Axial length and corneal birefringence measurements did not influence RNFL measurements. Repeatability, as assessed by the coefficient of variation, ranged between 1.7% for the overall average RNFL measurement and 11.4% for th nerve fiber indicator. Age significantly affected all RNFL measurements with the ECC protocol of SLP, whereas TSS and residual anterior segment retardance affected the overall average and the superior average RNFL measurements, respectively. Axial length and corneal birefringence measurements did not influence any RNFL measurements. RNFL measurements had good intrasession repeatability. These results are important while evaluating the change in structural measurements over time in glaucoma patients.

  4. Mandibular thickness measurements in young dentate adults.

    Science.gov (United States)

    Beaty, Narlin B; Le, Thomas T

    2009-09-01

    To measure thicknesses in clinical landmark areas of the dentate mandibles of young men and women. Using standard radiologic software, we obtained mean (SD) thickness measurements at the inferior or posterior borders of the mandible at the following 7 surgically useful sites: (1) the symphysis, (2) a point halfway between the symphysis and the mental nerve, (3) the mental nerve, (4) a point halfway between the mental nerve and the facial artery notch, (5) the facial artery notch, (6) the angle vertex, and (7) the ramus-condylar neck border. University hospital. A total of 150 dentate men and 75 dentate women aged 18 to 30 years who had undergone computed tomography of the head and neck region during the period of December 20, 2006 to February 20, 2007. Thicknesses of 7 mandibular sites. Mean (SD) thicknesses at the 7 mandibular sites were as follows: symphysis, 14.03 (1.53) mm for men and 13.21 (1.46) mm for women; halfway between the symphysis and the mental nerve, 11.17 (1.37) mm for men and 10.00 (1.08) mm for women; mental nerve, 9.48 (1.28) mm for men and 8.72 (1.00) mm for women; halfway between the mental nerve and the facial artery notch, 10.33 (1.24) mm for men and 9.45 (0.92) mm for women; facial artery notch, 7.27 (0.82) mm for men and 7.10 (0.88) mm for women; angle vertex, 5.42 (0.90) mm for men and 5.39 (0.66) mm for women; and ramus-condylar neck border, 5.90 (0.86) mm for men and 5.85 (0.71) mm for women. Clinical landmark areas in young dentate mandibles have mean thicknesses with limited SDs. The thickness measurements obtained at the sites in this study provide practical reference information for mandibular reconstruction and bicortical screw length estimation.

  5. Cement thickness measurements in cased boreholes

    International Nuclear Information System (INIS)

    Wahl, J.S.; Schuster, N.A.

    1978-01-01

    Methods and apparatus are provided for logging a borehole having solid matter along at least a portion of the wall thereof. Gamma radiation is emitted from the borehole into the surrounding media, and the amount of radiation which returns to the borehole is measured by three detectors located at different distances from the source of radiation, so as to be primarily sensitive to radiation which has respectively penetrated to three different depths in the surrounding media. The thickness of the solid matter on the borehole wall is then determined from the three gamma radiation measurements

  6. Intraocular pressure measurements and corneal biomechanical properties using a dynamic Scheimpflug analyzer, after several keratoplasty techniques, versus normal eyes.

    Science.gov (United States)

    Hugo, J; Granget, E; Ho Wang Yin, G; Sampo, M; Hoffart, L

    2018-01-01

    To evaluate the biomechanical properties of the cornea and their impact on intraocular pressure (IOP) measurement after lamellar keratoplasty, compared to healthy eyes, using a non-contact tonometer with a Scheimpflug camera. This study, from 2014 to 2015, included 22 primary DSAEK, 5 DALK, 6 DSAEK after PK, and 50 control eyes. Using a non-contact tonometer with a high-speed Scheimpflug camera (CORVIS ST, Oculus Optikgeräte GmbH, Wetzlar, Germany), several biomechanical parameters were recorded, including radius at highest concavity (R hc ) and defomation amplitude (DA). Central corneal thickness (CCT) and uncorrected IOP, were also recorded. For the control eyes only, a corrected IOP was calculated, based on age, central corneal thickness, and biomechanical parameters. R hc was significantly lower after DALK (R hc =5.54±0.71, P=0.007) and DSAEK (R hc =6.26±0.77, P=0.042) compared to control eyes (R hc =6.82±0.76). DA was higher after DALK and DSAEK, but not significantly (respectively 1.24±0.09 P=0.41 and 1.22±0.15, P=0.923) compared to normal eyes (1.18±0.15). Uncorrected IOP was not significantly different between post-keratoplasty and control eyes. In control eyes, the corrected IOP (15.23±1.88) was lower than the uncorrected IOP (16.10±2.34); a statistically significant positive correlation between R hc and CCT (R 2 =0.6020, P<0001), and a significant negative correlation between DA and CCT (R 2 =-0.641, P<0.0001) were found. Our study showed that, after lamellar keratoplasty, corneal biomechanics are altered. Corneas with higher ocular rigidity will show a lower DA and a higher R hc . Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  7. Evaluación del espesor corneal central y su influencia en la presión intraocular en pacientes del Hospital "Dr. Miguel Enríquez" Evaluation of the central corneal thickness and its impact on the intraocular pressure of patients in "Dr. Miguel Enriquez" hospital

    Directory of Open Access Journals (Sweden)

    María Teresa Arrronte Alarcón

    2012-01-01

    Full Text Available Objetivo: evaluar el espesor corneal central en sujetos sanos, hipertensos oculares, sospechosos de glaucoma y glaucomatosos, y su influencia en la presión intraocular. Métodos: se realizó un estudio descriptivo y transversal que incluyó 708 ojos de 356 sujetos que acudieron al servicio de oftalmología del Hospital Universitario "Dr. Miguel Enríquez" entre enero y diciembre de 2010. A los pacientes se les midió el espesor corneal central con paquimetría ultrasónica (paquímetro US 4000. El resto de la información se obtuvo a partir de las historias clínicas de los pacientes. Resultados: Los hipertensos oculares presentaron córneas gruesas (p=0,07; el mayor número de casos que tenían diagnóstico de sospecha de glaucoma y de glaucoma primario de ángulo abierto presentaron un grosor corneal delgado (p=0,62 y p=0,08 respectivamente. Si no se hubiese tenido en cuenta el factor de corrección para evaluar la presión intraocular se encontraría 48,1 % de los glaucomatosos y 31,5 % de los hipertensos oculares con diagnóstico inadecuado (pObjective: to evaluate the central corneal thickness in healthy individuals, in persons with ocular hypertension, and in suspected glaucoma and glaucomatous people, and its influence in intraocular pressure. Methods: a cross-sectional and descriptive study was performed in 708 eyes from 356 people who had been seen at ophthalmology service of “Dr. Miguel Enríquez”, university hospital from January to December, 2010. Their central corneal thickness was measured with ultrasonic pachymetry (pachymeter US 4000. The rest of the information came from the clinical histories of the patients. Results: Most of the ocular hypertensives presented thick corneas (p=0,07; a high number of cases that had diagnosis of glaucoma suspicion and primary open-angle glaucoma showed thin corneas (p=0,62 and (p=0,08 respectively. If the correction factor to evaluate the IOP had not been considered, then 48,1 % of the

  8. Measuring coating thicknesses on continuously moving material

    International Nuclear Information System (INIS)

    Holler, J.H.; Stanton, W.B.; Spongr, J.J.; Joffe, B.B.; Raffelsberger, P.W.; Tiebor, J.E.

    1982-01-01

    A method and apparatus using radiation techniques for measuring coating thicknesses on continuously moving strip material without altering a predetermined path along which it travels. A shuttle carrying a measuring probe having a radioactive isotope source and a detection device is provided for reciprocation along a preselected segment of the path of the strip. The shuttle and the probe are releasably engaged with the strip and carried thereby for synchronous movement therewith in the forward direction during a measurement cycle, and are disengaged from the strip when no measurement is being made, the movement of the shuttle then being controlled by an independent drive mechanism, shown as a belt drive, which reciprocates the shuttle along the rails. A belt drives it forward more slowly than the strip, which then engages the shuttle to pull it at strip speed, allowed by a pulley clutch. (author)

  9. Equine corneal stromal abscesses

    DEFF Research Database (Denmark)

    Henriksen, M. D. L.; Andersen, P. H.; Plummer, C. E.

    2013-01-01

    The last 30 years have seen many changes in the understanding of the pathogenesis and treatment of equine corneal stromal abscesses (SAs). Stromal abscesses were previously considered an eye problem related to corneal bacterial infection, equine recurrent uveitis, corneal microtrauma and corneal....... Medical and surgical treatments are now directed towards elimination of fungal and bacterial infections, reduction and replacement of diseased corneal stroma, and suppression of iridocyclitis. If the abscess and anterior uveitis do not respond satisfactorily to medical therapy, full thickness or split...

  10. Reproducibility of corneal, macular and retinal nerve fiber layer ...

    African Journals Online (AJOL)

    side the limits of a consulting room.5. Reproducibility of ... examination, intraocular pressure and corneal thickness ... All OCT measurements were taken between 2 and 5 pm ..... CAS-OCT, Slit-lamp OCT, RTVue-100) have shown ICC.

  11. Influence of corneal biomechanical properties on intraocular pressure differences between an air-puff tonometer and the Goldmann applanation tonometer.

    Science.gov (United States)

    Tranchina, Laura; Lombardo, Marco; Oddone, Francesco; Serrao, Sebastiano; Schiano Lomoriello, Domenico; Ducoli, Pietro

    2013-01-01

    To estimate the influence of corneal properties on intraocular pressure (IOP) differences between an air-puff tonometer (NT530P; Nidek) and the Goldmann applanation tonometer (Haag-Streit). The influence of central corneal thickness (CCT), keratometry, and Ocular Response Analyzer (Reichert) measurements of corneal viscoelasticity [corneal hysteresis (CH) and corneal resistance factor (CRF)] on IOP differences between tonometers was evaluated. The CRF was calculated to be the best predictor of the differences in IOP readings between tonometers (r2=0.23; Ptonometers. Corneal resistance to applanation induced by either contact or noncontact tonometers was calculated to be the most determinant factor in influencing IOP differences between applanation tonometers.

  12. New portable pipe wall thickness measuring technique

    Science.gov (United States)

    Pascente, Joseph E.

    1998-03-01

    One of the biggest inspection challenges facing many of the process industries; namely the petrochemical, refining, fossil power, and pulp and paper industries is: How to effectively examine their insulated piping? While there are a number of failure mechanisms involved in various process piping systems, piping degradation through corrosion and erosion are by far the most prevalent. This degradation can be in the form of external corrosion under insulation, internal corrosion through a variety of mechanisms, and internal erosion caused by the flow of the product through the pipe. Refineries, chemical plants and electrical power plants have MANY thousands of miles of pipe that are insulated to prevent heat loss or heat absorption. This insulation is often made up of several materials, with calcium based material being the most dense. The insulating material is usually wrapped with an aluminum or stainless steel outer wrap. Verification of wall thickness of these pipes can be accomplished by removing the insulation and doing an ultrasound inspection or by taking x- rays at a tangent to the edge of the pipe through the insulation. Both of these processes are slow and expensive. The time required to obtain data is measured in hours per meter. The ultrasound method requires that the insulation be plugged after the inspection. The surface needs to be cleaned or the resulting data will not be accurate. The tangent x-ray only shows two thicknesses and requires that the area be roped off because of radiation safety.

  13. Corneal Laceration

    Medline Plus

    Full Text Available ... Ophthalmology/Strabismus Ocular Pathology/Oncology Oculoplastics/Orbit Refractive ... Corneal Laceration Sections What Is Corneal Laceration? Corneal Laceration Symptoms What Causes ...

  14. Corneal Densitometry as a Tool to Measure Epithelial Ingrowth After Laser In Situ Keratomileusis.

    Science.gov (United States)

    Adran, Daniel; Vaillancourt, Louis; Harissi-Dagher, Mona; Kruh, Jonathan N; Syed, Zeba A; Robinson, Steven; Melki, Samir

    2017-04-01

    This study evaluates the correlation between corneal densitometry and epithelial ingrowth (EI) after laser in situ keratomileusis (LASIK). Corneal densitometry of 3 patients who developed EI after LASIK was measured with the Oculus Pentacam. Corneal densitometry readings of each patient were obtained preoperatively and postoperatively after ingrowth was discovered. Densitometry was recorded at the central nest of opacity and at the leading edges of EI. For all patients, the most severe stages of EI observed on slit-lamp photographs correlated with the highest densitometry readings, with peak densitometry ranging from 73.3 to 95.1. These values were much higher than preoperative densitometry readings, which ranged from 21.8 to 27.2. In 2 cases, the Pentacam densitometry map revealed progression of EI toward the visual axis that was only faintly detectable or not detectable at all on the corresponding slit-lamp photographs. Corneal densitometry seems to be an objective measure of the severity and progression of EI after LASIK.

  15. Comparing two acromegalic patients with respect to central corneal thickness, intraocular pressure, and tear insulin-like growth factor levels before and after treatment

    Directory of Open Access Journals (Sweden)

    Kan Emrah

    2015-01-01

    Full Text Available The aim of the study was to compare the central corneal thickness (CCT, intraocular pressure (IOP, and tear insulin-like growth factor-1 (IGF-1 levels of 2 patients with acromegaly before and after the surgical treatment of the disease. CCTs, IOP levels, and tear IGF-1 values showed a decrease after the treatment in 2 patients. As we found higher CCT, IOP, and tear IGF-1 levels in the active phase of the disease in two acromegaly patients, detailed information about the activity of the disease may be important before the examination of these patients.

  16. Thickness measuring instrument for rubber cord calender production

    International Nuclear Information System (INIS)

    Ye Songfeng

    1988-01-01

    The thickness measuring gauge has been used to measure the rubber film thickness on the coating of textile cord at tire four cord calenders. Combined with micro-computer it completes the automatic control system and acheives automatic thickness measurement and adjustment. The fundamentals, construction, specifications, characteristic and application results are described. Prominent economic benefit has been gained for tire production

  17. Quantitative assessment of corneal vibrations during intraocular pressure measurement with the air-puff method in patients with keratoconus.

    Science.gov (United States)

    Koprowski, Robert; Ambrósio, Renato

    2015-11-01

    One of the current methods for measuring intraocular pressure is the air-puff method. A tonometer which uses this method is the Corvis device. With the ultra-high-speed (UHS) Scheimpflug camera, it is also possible to observe corneal deformation during measurement. The use of modern image analysis and processing methods allows for analysis of higher harmonics of corneal deflection above 100 Hz. 493 eyes of healthy subjects and 279 eyes of patients with keratoconus were used in the measurements. For each eye, 140 corneal deformation images were recorded during intraocular pressure measurement. Each image was recorded every 230 µs and had a resolution of 200 × 576 pixels. A new, original algorithm for image analysis and processing has been proposed. It enables to separate the eyeball reaction as well as low-frequency and high-frequency corneal deformations from the eye response to an air puff. Furthermore, a method for classification of healthy subjects and patients with keratoconus based on decision trees has been proposed. The obtained results confirm the possibility to distinguish between patients with keratoconus and healthy subjects. The features used in this classification are directly related to corneal vibrations. They are only available in the proposed software and provide specificity of 98%, sensitivity-85%, and accuracy-92%. This confirms the usefulness of the proposed method in this type of classification that uses corneal vibrations during intraocular pressure measurement with the Corvis tonometer. With the new proposed algorithm for image analysis and processing allowing for the separation of individual features from a corneal deformation image, it is possible to: automatically measure corneal vibrations in a few characteristic points of the cornea, obtain fully repeatable measurement of vibrations for the same registered sequence of images and measure vibration parameters for large inter-individual variability in patients. Copyright © 2015 Elsevier

  18. Manual for target thickness measurement by alpha particle irradiation

    International Nuclear Information System (INIS)

    Dias, J.F.; Martins, M.N.

    1990-04-01

    A system is described for thin-target thickness measurement through the alpha particle energy loss when them traverse the target. It is also described the program used in the analysis of the target thickness. (L.C.) [pt

  19. [Evaluation of corneal biomechanics in keratoconus using dynamic ultra-high-speed Scheimpflug measurements].

    Science.gov (United States)

    Brettl, S; Franko Zeitz, P; Fuchsluger, T A

    2018-06-22

    The in vivo analysis of corneal biomechanics in patients with keratoconus is especially of interest with respect to diagnosis, follow-up and monitoring of the disease. For a better understanding it is necessary to describe the potential of dynamic Scheimpflug measurements for the detection and interpretation of biomechanical changes in keratoconus. The current state of analyzing biomechanical changes in keratoconus with the Corvis ST (Oculus Optikgeräte GmbH, Wetzlar, Germany) is described. This technique represents a new approach for understanding corneal biomechanics. Furthermore, it was investigated whether the device can biomechanically quantify a rigidity increasing effect of therapeutic UV-crosslinking and whether early stages of keratoconus can be detected using dynamic Scheimpflug analysis. In patients with keratoconus, the in vivo analysis of corneal biomechanics using dynamic Scheimpflug measurements as a supplementary procedure can be of advantage with respect to disease management. By optimization of screening of subclinical keratoconus stages, this method widens the analytic spectrum regarding diagnosis and follow-up of the disease; however, further studies are required to evaluate whether visual outcome of affected patients can be improved by earlier diagnosis.

  20. Study on phototherapeutic keratotomy for bacterial corneal lesions in rabbit

    Directory of Open Access Journals (Sweden)

    Xin Zhou

    2018-05-01

    Full Text Available AIM: To study the effect of phototherapeutic keratectomy(PTKon rabbit bacterial corneal ulcer model and explore the clinical potential of this method. METHODS: Totally 48 eyes from all the 24 New Zealand rabbits were inoculated with Staphylococcus aureus and bacterial corneal ulcer model was established successfully. At 1d after inoculation, 48 eyes were given levofloxacin eye drops when corneal ulcer was confirmed. Then slit lamp inspection and optical coherence tomography(OCTwere performed to measure the central corneal ulcer depth. All the rabbits right eyes were treated with PTK, as an observation group, left eyes were not treated as a control group. The eye section were observed by slit lamp and central thickness of corneal ulcer was measured by OCT at 3 and 7d after this operation. Rabbits were sacrificed and the cornea was removed for pathological section 7d later. RESULTS: The corneal ulcers in both groups had a tendency to heal, showing a decrease in ulcer area and smoothness of the surface. There was no significant difference in the depth of corneal ulcer between the observation group and the control group before PTK(t=0.706, P=0.484. The difference between the two groups of eyes at 3 and 7d after PTK was obviously(PCONCLUSION: PTK can effectively cure rabbit Staphylococcus aureus corneal ulcer and promote ulcer wound healing, which may be used for clinical treatment of patients with bacterial corneal lesions.

  1. Beta ray backscattering studies for thickness measurements

    Energy Technology Data Exchange (ETDEWEB)

    Singh, M; Sharma, K K [Punjabi Univ., Patiala (India). Nuclear Science Labs.

    1979-01-01

    Back-scattering of beta rays from /sup 204/Tl (Esub(..beta..)max = 740 keV) and /sup 90/Sr-/sup 90/Y (Esub(..beta..)max =550 and 2250 keV) has been studied in an improved reflection geometry, using annular sources, from a number of elemental targets with Z values ranging from 13 to 82. Source to target and target to detector geometry factors are 0.0225 and 0.0282 respectively. Values of saturation back scattering thickness obtained in the two cases are 72 +- 10 and 190 +- 40 mg/cm/sup 2/ respectively. It is observed that the intensity of back scattered radiation varies linearly with thickness upto a value of 12 +- 2 mg/cm/sup 2/ in /sup 204/Tl and 17 +- 3 mg/cm/sup 2/ in /sup 90/Sr-/sup 90/Y.

  2. Assessment of UVA-Riboflavin Corneal Cross-Linking Using Small Amplitude Oscillatory Shear Measurements.

    Science.gov (United States)

    Aslanides, Ioannis M; Dessi, Claudia; Georgoudis, Panagiotis; Charalambidis, Georgios; Vlassopoulos, Dimitris; Coutsolelos, Athanassios G; Kymionis, George; Mukherjee, Achyut; Kitsopoulos, Theofanis N

    2016-04-01

    The effect of ultraviolet (UV)-riboflavin cross-linking (CXL) has been measured primarily using the strip extensometry technique. We propose a simple and reliable methodology for the assessment of CXL treatment by using an established rheologic protocol based on small amplitude oscillatory shear (SAOS) measurements. It provides information on the average cross-link density and the elastic modulus of treated cornea samples. Three fresh postmortem porcine corneas were used to study the feasibility of the technique, one serving as control and two receiving corneal collagen cross-linking treatment. Subsequently, five pairs of fresh postmortem porcine corneas received corneal collagen cross-linking treatment with riboflavin and UVA-irradiation (370 nm; irradiance of 3 mW/cm2) for 30 minutes (Dresden protocol); the contralateral porcine corneas were used as control samples. After the treatment, the linear viscoelastic moduli of the corneal samples were measured using SAOS measurements and the average cross-linking densities extracted. For all cases investigated, the dynamic moduli of the cross-linked corneas were higher compared to those of the corresponding control samples. The increase of the elastic modulus of the treated samples was between 122% and 1750%. The difference was statistically significant for all tested samples (P = 0.018, 2-tailed t-test). We report a simple and accurate methodology for quantifying the effects of cross-linking on porcine corneas treated with the Dresden protocol by means of SAOS measurements in the linear regime. The measured dynamic moduli, elastic and viscous modulus, represent the energy storage and energy dissipation, respectively. Hence, they provide a means to assess the changing physical properties of the cross-linked collagen networks after CXL treatment.

  3. Evaluation of Corneal Topography and Biomechanical Parameters after Use of Systemic Isotretinoin in Acne Vulgaris

    Directory of Open Access Journals (Sweden)

    Yusuf Yildirim

    2014-01-01

    Full Text Available Purpose. We report the effect of isotretinoin on corneal topography, corneal thickness, and biomechanical parameters in patients with acne vulgaris. Method. Fifty-four eyes of 54 patients who received oral isotretinoin for treatment of acne vulgaris were evaluated. All patients underwent a corneal topographical evaluation with a Scheimpflug camera combined with Placido-disk (Sirius, ultrasonic pachymetry measurements, and corneal biomechanical evaluation with an ocular response analyzer at baseline, in the 1st, 3rd, and 6th months of treatment, and 6 months after isotretinoin discontinuation. Results. The thinnest corneal thickness measured with Sirius differed significantly in the 1st, 3rd, and 6th months compared with the baseline measurement; there was no significant change in ultrasonic central corneal thickness measurements and biomechanical parameters (corneal hysteresis and corneal resistance factor throughout the study. Average simulated keratometry and surface asymmetry index increased significantly only in the first month of treatment according to the baseline. All changes disappeared 6 months after the end of treatment. Conclusion. Basal tear secretion and corneal morphologic properties were significantly influenced during the systemic isotretinoin treatment and the changes were reversible after discontinuation. No statistical important biomechanical differences were found to be induced by isotretinoin.

  4. Interferometric measurement of film thickness during bubble blowing

    Science.gov (United States)

    Wang, Z.; Mandracchia, B.; Ferraro, V.; Tammaro, D.; Di Maio, E.; Maffettone, P. L.; Ferraro, P.

    2017-06-01

    In this paper, we propose digital holography in transmission configuration as an effective method to measure the time-dependent thickness of polymeric films during bubble blowing. We designed a complete set of experiments to measure bubble thickness, including the evaluation of the refractive index of the polymer solution. We report the measurement of thickness distribution along the film during the bubble formation process until the bubble`s rupture. Based on those data, the variation range and variation trend of bubble film thickness are clearly measured during the process of expansion to fracture is indicated.

  5. Impact of dehydration and fasting on intraocular pressure and corneal biomechanics measured by the Ocular Response Analyzer.

    Science.gov (United States)

    Uysal, Betul Seher; Duru, Necati; Ozen, Umut; Arikan Yorgun, Mucella; Akcay, Emine; Caglayan, Mehtap; Cagil, Nurullah

    2018-04-01

    To investigate the effects of dehydration and fasting on the intraocular pressure (IOP) and corneal biomechanics during Ramadan in healthy subjects. A total of 36 healthy fasting male volunteers with a mean age of 32.7 ± 5.1 years (range 28-38 years) were enrolled in the study. A Reichert Ocular Response Analyzer (ORA) was used to measure the corneal resistance factor (CRF), corneal hysteresis (CH), Goldman-correlated IOP (IOPg), and corneal-compensated IOP (IOPcc), additionally IOP with Goldmann applanation tonometer (IOP-GAT) was taken. All measurements were recorded at 8:00 am and 4:00 p.m. during Ramadan and during a 1-month follow-up after Ramadan was over. Statistical analysis demonstrated no difference in the ORA measurements including CH, CRF, IOPcc, and IOPg; CCT and CV values between fasting and non-fasting periods or within a single day (diurnal changes). Nine volunteers (25% of total subjects) were excluded because eyedrops were believed to disrupt the Ramadan fast consequently IOP-GAT could not be measured from these subjects. No statistically significant difference was noted between IOP-GAT and IOPg measurements of twenty-seven subjects at the different periods and time points. Our results reveal that fasting during Ramadan does not profoundly affect corneal biomechanics and IOP values in healthy volunteers without ocular diseases such as glaucoma. When planning corneal refractive surgery and determining IOP, the ORA measurements can be done safely during a Ramadan fast. Moreover, ORA may be a better alternative for patients that refuse IOP measurement via GAT for examining the accuracy of IOP during fasting. Further studies are needed to better understand the role of these parameters on corneal disease and glaucoma during fasting.

  6. Pelvic floor muscle thickness measured by perineal ultrasonography

    DEFF Research Database (Denmark)

    Bernstein, Inge Thomsen; Juul, N; Grønvall, S

    1991-01-01

    Pelvic floor muscle thickness was assessed in nine healthy female physiotherapists by perineal sonography. All measurements were performed as triple-measurements. The aims were to assess the reliability of the measurements and to establish a reference material. The muscle thickness at rest...

  7. Post-PRK corneal scatter measurements with a scanning confocal slit photon counter

    Science.gov (United States)

    Taboada, John; Gaines, David; Perez, Mary A.; Waller, Steve G.; Ivan, Douglas J.; Baldwin, J. Bruce; LoRusso, Frank; Tutt, Ronald C.; Perez, Jose; Tredici, Thomas; Johnson, Dan A.

    2000-06-01

    Increased corneal light scatter or 'haze' has been associated with excimer laser photorefractive surgery of the cornea. The increased scatter can affect visual performance; however, topical steroid treatment post surgery substantially reduces the post PRK scatter. For the treatment and monitoring of the scattering characteristics of the cornea, various methods have been developed to objectively measure the magnitude of the scatter. These methods generally can measure scatter associated with clinically observable levels of haze. For patients with moderate to low PRK corrections receiving steroid treatment, measurement becomes fairly difficult as the haze clinical rating is non observable. The goal of this development was to realize an objective, non-invasive physical measurement that could produce a significant reading for any level including the background present in a normal cornea. As back-scatter is the only readily accessible observable, the instrument is based on this measurement. To achieve this end required the use of a confocal method to bias out the background light that would normally confound conventional methods. A number of subjects with nominal refractive errors in an Air Force study have undergone PRK surgery. A measurable increase in corneal scatter has been observed in these subjects whereas clinical ratings of the haze were noted as level zero. Other favorable aspects of this back-scatter based instrument include an optical capability to perform what is equivalent to an optical A-scan of the anterior chamber. Lens scatter can also be measured.

  8. Thickness measurement by using cepstrum ultrasonic signal processing

    International Nuclear Information System (INIS)

    Choi, Young Chul; Yoon, Chan Hoon; Choi, Heui Joo; Park, Jong Sun

    2014-01-01

    Ultrasonic thickness measurement is a non-destructive method to measure the local thickness of a solid element, based on the time taken for an ultrasound wave to return to the surface. When an element is very thin, it is difficult to measure thickness with the conventional ultrasonic thickness method. This is because the method measures the time delay by using the peak of a pulse, and the pulses overlap. To solve this problem, we propose a method for measuring thickness by using the power cepstrum and the minimum variance cepstrum. Because the cepstrums processing can divides the ultrasound into an impulse train and transfer function, where the period of the impulse train is the traversal time, the thickness can be measured exactly. To verify the proposed method, we performed experiments with steel and, acrylic plates of variable thickness. The conventional method is not able to estimate the thickness, because of the overlapping pulses. However, the cepstrum ultrasonic signal processing that divides a pulse into an impulse and a transfer function can measure the thickness exactly.

  9. A comparison of the Goldmann applanation and non-contact (Keeler Pulsair EasyEye) tonometers and the effect of central corneal thickness in indigenous African eyes.

    Science.gov (United States)

    Babalola, O E; Kehinde, A V; Iloegbunam, A C; Akinbinu, T; Moghalu, C; Onuoha, I

    2009-03-01

    The Keeler Pulsair EasyEye non-contact tonometer (NCT) was introduced into practice at Rachel Eye Center Abuja, Nigeria, where the patients are indigenous Africans. This was compared to the 'gold standard' Goldmann applanation tonometer (GAT) to determine if the instrument was accurate in Africans, with particular reference to the influence of central corneal thickness (CCT). 174 eyes of 88 patients were analysed. Pachymetry was performed using Sonomed PacScan AP300, and GAT with the Haag Streit R-900. Pachymetric corrections of NCT (NCTc) and GAT (GATc) were carried out with the Sonomed algorithm. Pearson's correlation r, linear regression analysis, Student t-test and Bland-Altman analysis were used to compare the instruments. Mean NCT readings were similar (17.36 mmHg) to mean GAT (17.42 mmHg; p = 0.769). GAT/NCT correlation coefficient, r, was 0.883 as compared with 0.868 for GATc/NCTc. The linear regression equation was GAT = 2.79 + 0.84*NCT (r(2) = 0.78). Forty-five per cent of differences were within 1 mmHg, while 79% were within 3 mmHg. This was similar to findings in some studies on Caucasians. Bland-Altman analysis however suggested that the spread of differences was wider than in those studies. Outliers (differences more than 5 mmHg) sometimes reflected difficulties encountered with GAT in routine practice. Mean CCT was 537.9 microm, (S.D. 38.4, 95% confidence interval 532.1-543.7 microm) and CCT appeared lower than in Caucasians. Both GAT and NCT IOP tended to rise with increasing CCT but NCT had a greater tendency to do so. Regression analysis suggested that NCT IOP increased by 0.6 mmHg for every 10 mum increase in CCT, compared to 0.4 mmHg for GAT. Thirty-eight per cent of the patients preferred NCT as opposed to 25% GAT. The Keeler Pulsair EasyEye gives reliable measurements of IOP in African eyes but is significantly affected by CCT. Particularly in borderline cases where management decisions have to be taken, it may be necessary to have pachymetric

  10. Infrared sensing and the measurement of oil slick thickness

    International Nuclear Information System (INIS)

    Brown, H.M.; Baschuk, J.J.; Goodman, R.H.

    1998-01-01

    The issue of whether infrared images can be used to detect the thickness of a marine oil spill was discussed. Infrared images of oil spills on water show density variations because of variations in oil temperature and emissivity. These observations have been used to determine thickness variations in the oil. Experiments were conducted in a large wave basin using two typical crude oils in the thickness range of 1 mm to 10 mm. Infrared images of oil spills were recorded and simultaneous thickness measurements were made using an acoustic thickness gauge. The study showed that there is no relationship between infrared image pixel greyness and the thickness measured with an acoustic probe. It was not possible to determine the volume of a spill using infrared images. 2 refs., 1 tab., 4 figs

  11. Digital Thickness Measurement of a Transparent Plastic Orthodontic Device

    Science.gov (United States)

    Kim, Yoon-Hwan; Rhim, Sung-Han

    2018-05-01

    A transparent orthodontic device is used to move the teeth to the final calibration position to form a proper set of teeth. Because the uniform thickness of the device plays an important role in tooth positioning, the accuracy of the device's thickness profile is important for effective orthodontic treatment. However, due to the complexity of the device's geometry and the transparency of the device's material, measuring the complete thickness profile has been difficult. In the present study, a new optical scanning method to measure the thickness profile of transparent plastic orthodontic devices is proposed and evaluated by using scanning electron microscopy (SEM). The error of the new measurement method is less than ±18 μm. The new method can be used to measure the thickness of non-specific, multi-curved, transparent orthodontic devices.

  12. Pelvic floor muscle thickness measured by perineal ultrasonography

    DEFF Research Database (Denmark)

    Bernstein, Inge Thomsen; Juul, N; Grønvall, S

    1991-01-01

    Pelvic floor muscle thickness was assessed in nine healthy female physiotherapists by perineal sonography. All measurements were performed as triple-measurements. The aims were to assess the reliability of the measurements and to establish a reference material. The muscle thickness at rest...... and at contraction was 9.4 +/- 0.8 mm and 11.5 +/- 1.1 mm respectively (mean +/- SD). Contraction increased the thickness by 2.2 +/- 0.8 mm or 23 +/- 8%. The intra- and inter observer standard deviation of the estimate was in the range of 4-6%. In conclusion, we find the reliability of the measurements acceptable....

  13. Corneal Laceration

    Medline Plus

    Full Text Available ... Eye Health A-Z Symptoms Glasses & Contacts Tips & Prevention News Ask an Ophthalmologist Patient Stories Español Eye ... Causes Corneal Laceration? Corneal Laceration Diagnosis Corneal Laceration Treatment What Is Corneal Laceration? Leer en Español: ¿Qué ...

  14. The application of XRF to the thickness measurement of paper

    International Nuclear Information System (INIS)

    Guo Wei; Lai Wangchang; Guo Shengliang; Cheng Feng

    2007-01-01

    The purpose of this paper is to study on the application of XRF to the thickness measurement of paper. The mass thickness of a number of paper samples were respectively measured by the X-ray absorption method and the primary rays of radiated sources scattering method. The measurement results had been compared with each other, and got several helpful discussions. The measurement was using the IED-2000P type X-ray fluorescence analyzer from Chengdu Micro-Particle Technology Ltd., which is composed of a Si-pin X-ray detector with thermo electrical cooler, and double isotope sources ( 238 Pu). The experiment indicated that the veracity of the X-ray absorption method on the thickness measurement of paper is better than the primary rays of radiated sources scattering method, and the application of the primary rays of radiated sources scattering method to the thickness measurement of paper is verified as feasible. (authors)

  15. Wall thickness measurements using digital radiography - state of the art

    International Nuclear Information System (INIS)

    Wawrzinek, T.; Zscherpel, U.; Bellon, C.

    1997-01-01

    Projection radiography is a method long since used for wall thickness measurements in pipes. Another method sometimes applied is thickness determination based on measuring changes of the optical density by using radioactive isotopes, as in this case the effects of stray radiation are negligible. The two methods hitherto were to be performed manually, and wall thickness data were derived by calculations with a pocket calculator. The required measuring and calculating work can now be automated by way of computerized processing of digitised images. The paper presents the software for automated evaluation of data of a selected location after system calibration. (orig./CB) [de

  16. Intrastromal corneal ring implants for corneal thinning disorders: an evidence-based analysis.

    Science.gov (United States)

    2009-01-01

    -graft rates in KC patients have been reported. Visual rehabilitation or recovery of visual acuity after transplant may be slow and/or unsatisfactory to patients. INTACS® (Addition Technology Inc. Sunnyvale, CA, formerly KeraVision, Inc.) are the only currently licensed corneal implants in Canada. The implants are micro-thin poly methyl methacrylate crescent shaped ring segments with a circumference arc length of 150 degrees, an external diameter of 8.10 mm, an inner diameter of 6.77 mm, and a range of different thicknesses. Implants act as passive spacers and, when placed in the cornea, cause local separation of the corneal lamellae resulting in a shortening of the arc length of the anterior corneal curvature and flattening the central cornea. Increasing segment thickness results in greater lamellar separation with increased flattening of the cornea correcting for myopia by decreasing the optical power of the eye. Corneal implants also improve corneal astigmatism but the mechanism of action for this is less well understood. Treatment with corneal implants is considered for patients who are contact lens intolerant, having adequate corneal thickness particularly around the area of the implant incision site and without central corneal scarring. Those with central corneal scarring would not benefit from implants and those without an adequate corneal thickness, particularly in the region that the implants are being inserted, would be at increased risk for corneal perforation. Patients desiring to have visual rehabilitation that does not include glasses or contact lenses would not be candidates for corneal ring implants. Placement of the implants is an outpatient procedure with topical anesthesia generally performed by either corneal specialists or refractive surgeons. It involves creating tunnels in the corneal stroma to secure the implants either by a diamond knife or laser calibrated to an approximate depth of 70% of the cornea. Variable approaches have been employed by

  17. Thickness Measurement of Surface Attachment on Plate with Lamb Wave

    Science.gov (United States)

    Ma, Xianglong; Zhang, Yinghong; Wen, Lichao; He, Yehu

    2017-12-01

    Aiming at the thickness detection of the plate surface attachment, a nondestructive testing method based on the Lamb wave is presented. This method utilizes Lamb wave propagation characteristics of signals in a bi-layer medium to measure the surface attachment plate thickness. Propagation of Lamb wave in bi-layer elastic is modeled and analyzed. The two-dimensional simulation model of electromagnetic ultrasonic plate - scale is established. The simulation is conducted by software COMSOL for simulation analysis under different boiler scale thickness wave form curve. Through this study, the thickness of the attached material can be judged by analyzing the characteristics of the received signal when the thickness of the surface of the plate is measured.

  18. Measurement of the thickness of thin films by backscattered protons

    International Nuclear Information System (INIS)

    Samaniego, L.E.Q.

    1976-07-01

    The method of backscattered protons has been used to measure the thickness of thin films. A monoenergetic beam of protons is directed on the film to be measured and the backscattered protons are detected with a particle detector. The film thickness is calculated from the energy spectrum of the protons. In the case of films consisting of several layers of elements with well separated atomic masses, it is possible to separate the spectra of protons scattered from the different elements, permitting a measurement of the thicknesses of the different layers. The method consists of calculating the energy loss of the protons throughout their trajectory, from the point of incidence on the film to the final detection. Thicknesses were measured for the following film combinations: gold on mylar, chromium on mylar, gold on chromium on mylar, and pure mylar. (Author) [pt

  19. Determination of gold coating thickness measurement by using EDXRF

    International Nuclear Information System (INIS)

    Meor Yusoff Meor Sulaian; Masliana Muslimin; Fadlullah Jili Fursani

    2005-01-01

    The paper relates a study on the development of an analysis procedure for measuring the gold coating thickness using EDXRF technique. Gold coating thickness was measured by relating the counts under the Au L? peak its thickness value. In order to get a reasonably accurate result, a calibration graph was plotted using five gold-coated reference standards of different thickness. The calibration graph shows a straight line for thin coating measurement until 0.9 μm. Beyond this the relationship was not linear and this may be resulted from the self-absorption effect. Quantitative analysis was also performed on two different samples of gold coated jewelry and a phone connector. Result from the phone connector analysis seems to agree with the manufacturer gold coating value. From the analysis of gold-coated jewelry it had been able to differentiate the two articles as gold wash and gold electroplated. (Author)

  20. Using laser to measure stem thickness and cut weed stems

    DEFF Research Database (Denmark)

    Heisel, T.; Schou, Jørgen; Andreasen, C.

    2002-01-01

    Stem thickness of the weed Solanum nigrum and the crop sugarbeet was determined with a He-Ne laser using a novel non-destructive technique measuring stem shadow. Thereafter, the stems were cut close to the soil surface with a CO2 laser. Treatments were carried out on pot plants, grown....... A binary model was also tested. The non-linear model incorporating stem thickness described the data best, indicating that it would be possible to optimize laser cutting by measuring stem thickness before cutting. The general tendency was that more energy was needed the thicker the stem. Energy uses...... in the greenhouse, at two different growth stages, and plant dry matter was measured 2-5 weeks after treatment. The relationship between plant dry weight and laser energy was analysed using two different non-linear dose-response regression models; one model included stem thickness as a variable, the other did not...

  1. Model-based cartilage thickness measurement in the submillimeter range

    International Nuclear Information System (INIS)

    Streekstra, G. J.; Strackee, S. D.; Maas, M.; Wee, R. ter; Venema, H. W.

    2007-01-01

    Current methods of image-based thickness measurement in thin sheet structures utilize second derivative zero crossings to locate the layer boundaries. It is generally acknowledged that the nonzero width of the point spread function (PSF) limits the accuracy of this measurement procedure. We propose a model-based method that strongly reduces PSF-induced bias by incorporating the PSF into the thickness estimation method. We estimated the bias in thickness measurements in simulated thin sheet images as obtained from second derivative zero crossings. To gain insight into the range of sheet thickness where our method is expected to yield improved results, sheet thickness was varied between 0.15 and 1.2 mm with an assumed PSF as present in the high-resolution modes of current computed tomography (CT) scanners [full width at half maximum (FWHM) 0.5-0.8 mm]. Our model-based method was evaluated in practice by measuring layer thickness from CT images of a phantom mimicking two parallel cartilage layers in an arthrography procedure. CT arthrography images of cadaver wrists were also evaluated, and thickness estimates were compared to those obtained from high-resolution anatomical sections that served as a reference. The thickness estimates from the simulated images reveal that the method based on second derivative zero crossings shows considerable bias for layers in the submillimeter range. This bias is negligible for sheet thickness larger than 1 mm, where the size of the sheet is more than twice the FWHM of the PSF but can be as large as 0.2 mm for a 0.5 mm sheet. The results of the phantom experiments show that the bias is effectively reduced by our method. The deviations from the true thickness, due to random fluctuations induced by quantum noise in the CT images, are of the order of 3% for a standard wrist imaging protocol. In the wrist the submillimeter thickness estimates from the CT arthrography images correspond within 10% to those estimated from the anatomical

  2. Thickness and roughness measurements of nano thin films by interference

    Directory of Open Access Journals (Sweden)

    A Sabzalipour

    2011-06-01

    Full Text Available In the standard optical interference fringes approach, by measuring shift of the interference fringes due to step edge of thin film on substrate, thickness of the layer has already been measured. In order to improve the measurement precision of this popular method, the interference fringes intensity curve was extracted and analyzed before and after the step preparation. By this method, one can measure a few nanometers films thickness. In addition, using the interference fringes intensity curve and its fluctuations, the roughness of surface is measured within a few nanometers accuracy. Comparison of our results with some direct methods of thickness and roughness measurements, i.e. using surface profilemeter and atomic force microscopy confirms the accuracy of the suggested improvements.

  3. Clinical estimation of intraocular pressure with a non-contact tonometer and Goldman applanation tonometer as a tool for mass screening and its correlation with central corneal thickness: A comparative hospital based study

    Directory of Open Access Journals (Sweden)

    Anshulee Sood

    2015-01-01

    Full Text Available Purpose To assess the mean difference between intra-ocular pressure measurement by Goldmann applanation tonometer and Non Contact tonometer to determine the suitability of tonometer for community or mass screening and the variation in intra-ocular pressure between the two devices with respect to CCT. Material and Methods The proposed study was conducted on 300 eyes of 150 patients. The IOP assessment with the Goldmann applanation tonometer was always subsequent to that with the air-puff noncontact tonometer (AT-555. An average of three readings taken 15 seconds apart, with each method was taken to get final intraocular pressure reading for each eye. The central corneal thickness (CCT measurements were performed using the pachymeter. Results Majority of the eyes were found to be in the 12-24 mmHg group i.e. 51 % eyes in the right eye and 64 % in the left eye. 3. Mean IOP measured with NCT was 22.30±10.149 mmHg and with GAT was 18.31±7.427 mmHg, thus showing a difference of 3.99 mmHg. In patients where IOP was 24mm Hg the difference in the mean IOP for right eye was 5.69mmHg and for left eye 7.84mmHg (p<0.001. Both the methods of IOP measurement showed positive correlation with central corneal thickness. The NCT was more influenced by CCT than GAT; for every 10 micron CCT change, the IOP change expected with NCT was 0.47 mmHg and GAT was 0.29 mmHg. Conclusion Thus we can conclude that NCT can be used as a screening procedure in tertiary care centres catering to a large number of patients wherein it is not possible to do Goldmann applanation tonometry on all patients.. However, intraocular pressure readings may require adjustment, especially when measured with NCT in those patients who have a CCT that is significantly different from population mean.

  4. Comparison of Different Approaches for Measuring Tibial Cartilage Thickness

    Directory of Open Access Journals (Sweden)

    Maier Jennifer

    2017-07-01

    Full Text Available Osteoarthritis is a degenerative disease affecting bones and cartilage especially in the human knee. In this context, cartilage thickness is an indicator for knee cartilage health. Thickness measurements are performed on medical images acquired in-vivo. Currently, there is no standard method agreed upon that defines a distance measure in articular cartilage. In this work, we present a comparison of different methods commonly used in literature. These methods are based on nearest neighbors, surface normal vectors, local thickness and potential field lines. All approaches were applied to manual segmentations of tibia and lateral and medial tibial cartilage performed by experienced raters. The underlying data were contrast agent-enhanced cone-beam C-arm CT reconstructions of one healthy subject’s knee. The subject was scanned three times, once in supine position and two times in a standing weight-bearing position. A comparison of the resulting thickness maps shows similar distributions and high correlation coefficients between the approaches above 0.90. The nearest neighbor method results on average in the lowest cartilage thickness values, while the local thickness approach assigns the highest values. We showed that the different methods agree in their thickness distribution. The results will be used for a future evaluation of cartilage change under weight-bearing conditions.

  5. Metatarsophalangeal joint extension changes ultrasound measurements for plantar fascia thickness.

    Science.gov (United States)

    Granado, Michael J; Lohman, Everett B; Gordon, Keith E; Daher, Noha S

    2018-01-01

    Ultrasound is an inexpensive method for quantifying plantar fascia thickness, especially in those with plantar fasciitis. Ultrasound has also been used to assess the effectiveness of various treatments for plantar fasciitis by comparing plantar fascia thickness before and after an intervention period. While a plantar fascia thickness over 4 mm via ultrasound has been proposed to be consistent with plantar fasciitis, some researchers believe the 4 mm plantar fascia thickness level to be a dubious guideline for diagnosing plantar fasciitis due to the lack of standardization of the measurement process for plantar fascia thickness. In particular, no universal guidelines exist on the positioning of the metatarsophalangeal (MTP) joints during the procedure and the literature also has inconsistent protocols. The purpose of this study is to investigate and compare the influence of MTP joint extension on plantar fascia thickness in healthy participants and those with unilateral plantar fasciitis. The plantar fascia thickness of forty participants (20 with unilateral plantar fasciitis and 20 control) was measured via ultrasound three times at three different MTP joint positions: 1) at rest, 2) 30° of extension from the plantar surface, and 3) maximal extension possible. The plantar fascia became significantly thinner as MTP joint extension increased in both the plantar fasciitis group ( p  plantar fasciitis group, the involved plantar fascia was 1.2 to 1.3 mm thicker (p plantar fascia thickness between the two sides was less than 0.1 mm ( p  plantar fascia thickness. It is recommended that plantar fascia thickness measurements be performed with the toes at rest. If MTP joints must be extended, then the toes should be extended maximally and then noted to ensure subsequent ultrasound procedures are repeated. Standardizing the position of the MTP joints is not only important for attaining the most accurate thickness measurement of the plantar fascia, but is also

  6. Measurement of subcutaneous adipose tissue thickness by near-infrared

    International Nuclear Information System (INIS)

    Wang, Yu; Ying, Zeqiang; Hao, Dongmei; Zhang, Song; Yang, Yimin; Zeng, Yanjun

    2013-01-01

    Obesity is strongly associated with the risks of diabetes and cardiovascular disease, and there is a need to measure the subcutaneous adipose tissue (SAT) layer thickness and to understand the distribution of body fat. A device was designed to illuminate the body parts by near-infrared (NIR), measure the backscattered light, and predict the SAT layer thickness. The device was controlled by a single-chip microcontroller (SCM), and the thickness value was presented on a liquid crystal display (LCD). There were 30 subjects in this study, and the measurements were performed on 14 body parts for each subject. The paper investigated the impacts of pressure and skin colour on the measurement. Combining with principal component analysis (PCA) and support vector regression (SVR), the measurement accuracy of SAT layer thickness was 89.1 % with a mechanical caliper as reference. The measuring range was 5–11 mm. The study provides a non-invasive and low-cost technique to detect subcutaneous fat thickness, which is more accessible and affordable compared to other conventional techniques. The designed device can be used at home and in community.

  7. A comparative study of central corneal thickness (CCT and intraocular pressure (IOP in University of KwaZulu-Natal students of Black and Indian ethnicity*

    Directory of Open Access Journals (Sweden)

    Z. Sardiwalla

    2012-12-01

    Full Text Available Thisstudy compared central corneal thickness (CCT and intraocular pressure (IOP of Black and Indian students from the University of Kwa-Zulu-Natal. Two hundred (100 Black and 100 Indi- an participants of both genders aged 18-25 years (mean and standard deviation; 20.1±1.6 years participated in this study. CCT and IOP were measured for the right eye of each participant using a Tono-Pachymeter (NT530P and a Goldmann applanation tonometer (GAT respectively. Data was analyzed with descriptive, t-test and Pearson’s cor-relation statistics. In the total sample (N = 200, the mean CCT value was 519.5 ± 38.6 μm and CCT was higher in the Indians (526.5 ± 37.2 µm than in the Blacks (512.4 ± 38.9 µm (p = 0.01.  Also, it was higher in the females (522.3 µm than in males (516.7 µm, but the difference was insignificant (p = 0.07. The mean CCT was higher in the Indian males (520.1 µm than in the Black males (513.2 µm, but the difference was insignificant (p=0.39.  However, it was significantly higher in the Indian females (533 µm than in the Black females (511.6 µm (p = 0.003. In the total sample, the mean IOP was 14.6 mmHg and IOP was greater in Indiansthan Blacks (mean = 15.3 ± 2.9 mmHg and 13.8 ± 2.6 mmHg respectively (p = 0.01. Also, the mean IOP (N = 200 value was slightly higher in the females (14.7 mmHg than in males (14.5 mmHg (p = 0.51. The mean IOP was higher in the Indian males (15.0 mmHg than in the Black males (14.0 mmHg (p = 0.07 and the mean IOP value was higher in the Indian females (15.7 mmHg than in the Black females (13.6 mmHg (p < 0.001. The higher mean IOP value in the Indian than Black participants was attributed to the higher mean CCT values. A positive, but inconsistent association between CCT and IOP was found in this study, the coefficient in the total sample (r = 0.382, p = 0.000, in the Blacks (r = 0.196, p = 0.05 and in Indians (r = 0.498, p = 0.000. A national population study comparing CCT and IOP in the various

  8. The thickness measuring methods by means of radionuclides

    International Nuclear Information System (INIS)

    Henker, W.

    1974-01-01

    The thickness measuring devices RMM 24004 produced in German Democratic Republic are described. They consist of measuring probe and central unit. The measuring probe contains radiator and measuring head, which consists of radiation detector and electrometric amplifier. They utilize absorption or backscattering of 147 Pm, 85 Kr, 90 Sr/ 90 Y, 106 Ru/ 106 Rh or 137 Cs radiation in interaction with atoms of measured material. A survey of typical applications is given. (Z.M.)

  9. Thickness measurement instrument with memory storage of multiple calibrations

    International Nuclear Information System (INIS)

    Lieber, S.; Schlesinger, J.; Lieber, D.; Baker, A.

    1979-01-01

    An improved backscatter instrument for the nondestructive measurement of coatings on a substrate is described. A memory having selectable memory areas, each area having stored intelligence available which is determinative of the shape of a functional plot of coating thickness versus backscatter counts per minute unique for each particular combination of emitting isotope, substrate material, coating material and physical characteristics of the measuring instrument. A memory selector switch connects a selected area of memory to a microprocessor operating under program control whereby the microprocessor reads the intelligence stored at the selected area and converts the backscattered count of the coating being measured into indicia of coating thickness

  10. Measurement of compressed breast thickness by optical stereoscopic photogrammetry.

    Science.gov (United States)

    Tyson, Albert H; Mawdsley, Gordon E; Yaffe, Martin J

    2009-02-01

    The determination of volumetric breast density (VBD) from mammograms requires accurate knowledge of the thickness of the compressed breast. In attempting to accurately determine VBD from images obtained on conventional mammography systems, the authors found that the thickness reported by a number of mammography systems in the field varied by as much as 15 mm when compressing the same breast or phantom. In order to evaluate the behavior of mammographic compression systems and to be able to predict the thickness at different locations in the breast on patients, they have developed a method for measuring the local thickness of the breast at all points of contact with the compression paddle using optical stereoscopic photogrammetry. On both flat (solid) and compressible phantoms, the measurements were accurate to better than 1 mm with a precision of 0.2 mm. In a pilot study, this method was used to measure thickness on 108 volunteers who were undergoing mammography examination. This measurement tool will allow us to characterize paddle surface deformations, deflections and calibration offsets for mammographic units.

  11. High-precision thickness measurements using beta backscatter

    International Nuclear Information System (INIS)

    Heckman, R.V.

    1978-11-01

    A two-axis, automated fixture for use with a high-intensity Pm-147 source and a photomultiplier-scintillation beta-backscatter probe for making thickness measurements has been designed and built. A custom interface was built to connect the system to a minicomputer, and software was written to position the tables, control the probe, and make the measurements. Measurements can be made in less time with much greater precision than by the method previously used

  12. Biomedical sensor for transcutaneous oxygen measurements using thick film technology

    OpenAIRE

    Lam, Yu-Zhi (Liza)

    2003-01-01

    The measurement of the partial pressure of oxygen in arterial blood is essential for the analysis of a patient's respiratory condition. There are several commercially available methods and systems to measure this parameter transcutaneously. However, they tend to be cumbersome and costly. To overcome the disadvantages presented, a new type of sensor for transcutaneous blood gas measurement was investigated, employing thick film technology, which is an excellent technique to produce sensors in ...

  13. Ice thickness measurements and volume estimates for glaciers in Norway

    Science.gov (United States)

    Andreassen, Liss M.; Huss, Matthias; Melvold, Kjetil; Elvehøy, Hallgeir; Winsvold, Solveig H.

    2014-05-01

    Whereas glacier areas in many mountain regions around the world now are well surveyed using optical satellite sensors and available in digital inventories, measurements of ice thickness are sparse in comparison and a global dataset does not exist. Since the 1980s ice thickness measurements have been carried out by ground penetrating radar on many glaciers in Norway, often as part of contract work for hydropower companies with the aim to calculate hydrological divides of ice caps. Measurements have been conducted on numerous glaciers, covering the largest ice caps as well as a few smaller mountain glaciers. However, so far no ice volume estimate for Norway has been derived from these measurements. Here, we give an overview of ice thickness measurements in Norway, and use a distributed model to interpolate and extrapolate the data to provide an ice volume estimate of all glaciers in Norway. We also compare the results to various volume-area/thickness-scaling approaches using values from the literature as well as scaling constants we obtained from ice thickness measurements in Norway. Glacier outlines from a Landsat-derived inventory from 1999-2006 together with a national digital elevation model were used as input data for the ice volume calculations. The inventory covers all glaciers in mainland Norway and consists of 2534 glaciers (3143 glacier units) covering an area of 2692 km2 ± 81 km2. To calculate the ice thickness distribution of glaciers in Norway we used a distributed model which estimates surface mass balance distribution, calculates the volumetric balance flux and converts it into thickness using the flow law for ice. We calibrated this model with ice thickness data for Norway, mainly by adjusting the mass balance gradient. Model results generally agree well with the measured values, however, larger deviations were found for some glaciers. The total ice volume of Norway was estimated to be 275 km3 ± 30 km3. From the ice thickness data set we selected

  14. Dynamic-speckle profilometer for online measurements of coating thickness

    Energy Technology Data Exchange (ETDEWEB)

    Kamshilin, A A [Laboratory of Optical Sensor Technology, Department of Physics, University of Kuopio, PO Box 1627, FIN-70211 Kuopio (Finland); Semenov, D V [Laboratory of Optical Sensor Technology, Department of Physics, University of Kuopio, PO Box 1627, FIN-70211 Kuopio (Finland); Nippolainen, E [Laboratory of Optical Sensor Technology, Department of Physics, University of Kuopio, PO Box 1627, FIN-70211 Kuopio (Finland); Miridonov, S [Optics Department, CICESE, Carr. Tijuana-Ensenada km 107, C.P. 22860, A.P. 360, Ensenada, B.C. (Mexico)

    2007-10-15

    Online control of thickness of as-deposited coatings is of great importance because it directly affects the quality of protective coatings. We present a novel approach that enables online, real-time and non-contact measurements thickness of thermally sprayed coatings. The proposed technique uses dynamic speckles generated by rapidly deflecting laser beam. Within 10 ms the system can scan 500 times a small area of the deposited layer thus resulting in measurement accuracy of 5 microns irrespectively of the layer roughness. In comparison with traditional optical triangulation technique of distance measurements, our system has following advantages: (i) much simpler optical scheme that includes conventional photodiode to measure the scattered light, (ii) much simpler electronics for real-time data processing, (iii) much higher speed of measurements.

  15. Dynamic-speckle profilometer for online measurements of coating thickness

    International Nuclear Information System (INIS)

    Kamshilin, A A; Semenov, D V; Nippolainen, E; Miridonov, S

    2007-01-01

    Online control of thickness of as-deposited coatings is of great importance because it directly affects the quality of protective coatings. We present a novel approach that enables online, real-time and non-contact measurements thickness of thermally sprayed coatings. The proposed technique uses dynamic speckles generated by rapidly deflecting laser beam. Within 10 ms the system can scan 500 times a small area of the deposited layer thus resulting in measurement accuracy of 5 microns irrespectively of the layer roughness. In comparison with traditional optical triangulation technique of distance measurements, our system has following advantages: (i) much simpler optical scheme that includes conventional photodiode to measure the scattered light, (ii) much simpler electronics for real-time data processing, (iii) much higher speed of measurements

  16. Macular volume and central foveal thickness measurements in ...

    African Journals Online (AJOL)

    Objective: To determine macular volume and central foveal thickness measurements in normal eyes of healthy. Nigerian adults using Stratus optical coherence tomography. Subjects and Methods: Consenting 100 adults Nigerians with normal eyes were recruited and examined using Carl. Zeiss Stratus Optical Coherence ...

  17. Development of sea water pipe thickness measurement technique

    International Nuclear Information System (INIS)

    Morimoto, Kazuo; Wakayama, Seiichi; Takeuchi, Iwao; Masamori, Sigero; Yamasita, Takesi.

    1995-01-01

    In nuclear and thermal power plants, wall wear of sea water pipes is reported to occur in the inner surface due to corrosion and erosion. From the viewpoint of improving the equipments reliability, it is desirable that wall thickness should be measured from the outer surface of the pipe during operation. In the conventional method, paint on the outer surface of the pipe was locally removed at each point of a 20 by 50 mm grid, and inspection was carried out at these spots. However, this method had some problems, such as (1) it was necessary to replace the paint, and (2) it was difficult to obtain the precise distribution of wall thickness. Therefore, we have developed a wall thickness measuring system which has the following features. (1) It is possible to perform inspection from the outer surface without removing paint during operation. (2) It is possible to measure the distribution of wall thickness and display it as color contour map simultaneously. (3) The work of inspectors can be alleviated by the automatic recording of measured data. (author)

  18. Apparatus for measuring profile thickness of strip material

    International Nuclear Information System (INIS)

    Hold, A.C.

    1982-01-01

    Apparatus for measuring the thickness profile of steel strip comprises a radiation source reciprocally movable in a stepwise fashion (by a belt) across the strip width on one side thereof and a single elongated detector on the other side of the strip aligned with the scanning source. This detector may be a fluorescent scintillator detector or an ionisation chamber. Means are provided for sensing the degree of excitation in the detector in synchronism with the scanning source whereby to provide an output representative of the thickness profile of the strip. (author)

  19. Oxide thickness measurement for monitoring fuel performance at high burnup

    International Nuclear Information System (INIS)

    Jaeger, M.A.; Van Swam, L.F.P.; Brueck-Neufeld, K.

    1991-01-01

    For on-site monitoring of the fuel performance at high burnup, Advanced Nuclear Fuels uses the linear scan eddy current method to determine the oxide thickness of irradiated Zircaloy fuel cans. Direct digital data acquisition methods are employed to collect the data on magnetic storage media. This field-proven methodology allows oxide thickness measurements and rapid interpretation of the data during the reactor outages and makes it possible to immediately reinsert the assemblies for the next operating cycle. The accuracy of the poolside measurements and data acquisition/interpretation techniques have been verified through hot cell metallographic measurements of rods previously measured in the fuel pool. The accumulated data provide a valuable database against which oxide growth models have been benchmarked and allow for effective monitoring of fuel performance. (orig.) [de

  20. The TMS-1 corneal topography measurement applied to calibrated ellipsoidal convex surfaces.

    Science.gov (United States)

    Douthwaite, W A; Matilla, M T

    1996-03-01

    The purpose of this report is to assess the accuracy of the TMS-1 videokeratoscope (Computed Anatomy Inc.) by using convex ellipsoidal surfaces. The ellipsoids were calibrated using Form Talysurf analysis, which allowed for subsequent calculation of the vertex radius and p value. The videokeratoscope was used to examine the same ellipsoids. The data provided by the instrument software were used to plot a graph of r2 verses y2, where r is the measured radius at y, the distance from the corneal point being measured to the optical axis of the instrument. The intercept on the ordinate of this graph gives the vertex radius, and the slope give the p value. The results arising from the Talysurf and the TMS-1 techniques were compared. The TMS-1 videokeratoscope gave readings for the vertex radius that were generally higher than those of the Talysurf analysis. The vertex radius was up to 0.09 mm greater. The p value results were similar by the two methods for p values of approximately 0.8; however, the TMS-1 results were higher, and the discrepancy increased as the p value approached that of a paraboloid. Although the videokeratoscope may be useful in comparative studies of the cornea, there must be some doubt about the absolute values displayed as the surface becomes increasingly aspheric.

  1. Backscattering measurement device for measuring the thickness of a layer

    International Nuclear Information System (INIS)

    Weinstock, J.; Lieber, D.; Hay, W.D.

    1978-01-01

    There is provided for a measuring wheel on the run of which backscattering probes are mounted, serving for irradiation and measurement of the radiation reflected from a strip of substrate tape coated e.g. with Au. The probes are of the model HH-3 of Unit Process Assemblies Inc. The material strip is guided on the outside of the wheel run. The measuring wheel is rotating with such speed that the tangential velocity of a point on the run is equal to the speed of the strip. Therefore the movement of the strip need not be stopped during measurement (on-line measurement). (DG) [de

  2. Highly accurate adaptive TOF determination method for ultrasonic thickness measurement

    Science.gov (United States)

    Zhou, Lianjie; Liu, Haibo; Lian, Meng; Ying, Yangwei; Li, Te; Wang, Yongqing

    2018-04-01

    Determining the time of flight (TOF) is very critical for precise ultrasonic thickness measurement. However, the relatively low signal-to-noise ratio (SNR) of the received signals would induce significant TOF determination errors. In this paper, an adaptive time delay estimation method has been developed to improve the TOF determination’s accuracy. An improved variable step size adaptive algorithm with comprehensive step size control function is proposed. Meanwhile, a cubic spline fitting approach is also employed to alleviate the restriction of finite sampling interval. Simulation experiments under different SNR conditions were conducted for performance analysis. Simulation results manifested the performance advantage of proposed TOF determination method over existing TOF determination methods. When comparing with the conventional fixed step size, and Kwong and Aboulnasr algorithms, the steady state mean square deviation of the proposed algorithm was generally lower, which makes the proposed algorithm more suitable for TOF determination. Further, ultrasonic thickness measurement experiments were performed on aluminum alloy plates with various thicknesses. They indicated that the proposed TOF determination method was more robust even under low SNR conditions, and the ultrasonic thickness measurement accuracy could be significantly improved.

  3. Computer vision based nacre thickness measurement of Tahitian pearls

    Science.gov (United States)

    Loesdau, Martin; Chabrier, Sébastien; Gabillon, Alban

    2017-03-01

    The Tahitian Pearl is the most valuable export product of French Polynesia contributing with over 61 million Euros to more than 50% of the total export income. To maintain its excellent reputation on the international market, an obligatory quality control for every pearl deemed for exportation has been established by the local government. One of the controlled quality parameters is the pearls nacre thickness. The evaluation is currently done manually by experts that are visually analyzing X-ray images of the pearls. In this article, a computer vision based approach to automate this procedure is presented. Even though computer vision based approaches for pearl nacre thickness measurement exist in the literature, the very specific features of the Tahitian pearl, namely the large shape variety and the occurrence of cavities, have so far not been considered. The presented work closes the. Our method consists of segmenting the pearl from X-ray images with a model-based approach, segmenting the pearls nucleus with an own developed heuristic circle detection and segmenting possible cavities with region growing. Out of the obtained boundaries, the 2-dimensional nacre thickness profile can be calculated. A certainty measurement to consider imaging and segmentation imprecisions is included in the procedure. The proposed algorithms are tested on 298 manually evaluated Tahitian pearls, showing that it is generally possible to automatically evaluate the nacre thickness of Tahitian pearls with computer vision. Furthermore the results show that the automatic measurement is more precise and faster than the manual one.

  4. Imaging and thickness measurement of amorphous intergranular films using TEM

    International Nuclear Information System (INIS)

    MacLaren, I.

    2004-01-01

    Fresnel fringe analysis is shown to be unreliable for grain boundaries in yttrium-doped alumina: the determined thicknesses do not agree well with those measured from high resolution transmission electron microscopy (HRTEM), the asymmetry between under- and overfocus is very large, and Fresnel fringes are sometimes shown at boundaries which contain no amorphous film. An alternative approach to the analysis of HRTEM images of grain boundary films is demonstrated: Fourier filtering is used to remove the lattice fringes from the image thereby significantly enhancing the visibility of the intergranular films. The apparent film thickness shows a discrepancy between measurements from the original HRTEM image and the filtered image. It was shown that fringe delocalisation and diffuseness of the amorphous/crystalline interfaces will lead to a significant underestimate of the thickness in unprocessed HRTEM images. In contrast to this, the average thickness can be much more accurately measured from the Fourier-filtered image, provided the boundary is oriented accurately edge-on

  5. Corneal ablation depth readout of the MEL 80 excimer laser compared to Artemis three-dimensional very high-frequency digital ultrasound stromal measurements.

    Science.gov (United States)

    Reinstein, Dan Z; Archer, Timothy J; Gobbe, Marine

    2010-12-01

    To evaluate the accuracy of the ablation depth readout for the MEL 80 excimer laser (Carl Zeiss Meditec). Artemis 1 very high-frequency digital ultrasound measurements were obtained before and at least 3 months after LASIK in 121 eyes (65 patients). The Artemis-measured ablation depth was calculated as the maximum difference in stromal thickness before and after treatment. Laser in situ keratomileusis was performed using the MEL 80 excimer laser and the Hansatome microkeratome (Bausch & Lomb). The Aberration Smart Ablation profile was used in 56 eyes and the Tissue Saving Ablation profile was used in 65 eyes. All ablations were centered on the corneal vertex. Comparative statistics and linear regression analysis were performed between the laser readout ablation depth and Artemis-measured ablation depth. The mean maximum myopic meridian was -6.66±2.40 diopters (D) (range: -1.50 to -10.00 D) for Aberration Smart Ablation-treated eyes and -6.50±2.56 D (range: -1.34 to -11.50 D) for Tissue Saving Ablation-treated eyes. The MEL 80 readout was found to overestimate the Artemis-measured ablation depth by 20±12 μm for Aberration Smart Ablation and by 21±12 μm for Tissue Saving Ablation profiles. The accuracy of ablation depth measurement was improved by using the Artemis stromal thickness profile measurements before and after surgery to exclude epithelial changes. The MEL 80 readout was found to overestimate the achieved ablation depth. The linear regression equations could be used by MEL 80 users to adjust the ablation depth for predicted residual stromal thickness calculations without increasing the risk of ectasia due to excessive keratectomy depth as long as a suitable flap thickness bias is included. Copyright 2010, SLACK Incorporated.

  6. Sensor for thickness measurement of a liquid metal film

    International Nuclear Information System (INIS)

    Blanc, R.

    1984-04-01

    Description, calibration and measuring method of a sensor for the measure of thin liquid metal depths in a temperature range of 0-500 0 C and for shift frequencies from 0 to 100 Hz; these sensors are based on the principle of induction-coil impedance variation, as a function of the thickness of an electrical conductor matter placed in the coil magnetic field [fr

  7. Central corneal thickness, intraocular pressure, and degree of myopia in an adult myopic population aged 20 to 40 years in southeast Spain: determination and relationships

    Directory of Open Access Journals (Sweden)

    Manuel Garcia-Medina

    2011-02-01

    Full Text Available Manuel Garcia-Medina1, Jose Javier Garcia-Medina2,3, Pablo Garrido-Fernandez1, Jose Galvan-Espinosa1, Jesus Martin-Molina1, Carlos Garcia-Maturana4, Sergio Perez-Pardo1, Maria Dolores Pinazo-Duran3 1Department of Ophthalmology, Torrecardenas Hospital, Almeria, Spain; 2Department of Ophthalmology, Huercal Overa Hospital, Almeria, Spain; 3Ophthalmology Research Unit “Santiago Grisolia”, University Hospital Doctor Peset, Valencia, Spain; 4University of Sevilla, SpainObjective: To determine the values of, and study the relationships among, central corneal thickness (CCT, intraocular pressure (IOP, and degree of myopia (DM in an adult myopic population aged 20 to 40 years in Almeria (southeast Spain. To our knowledge this is first study of this kind in this region.Methods: An observational, descriptive, cross-sectional study was done in which a sample of 310 myopic patients (620 eyes aged 20 to 40 years was selected by gender- and age-stratified sampling, which was proportionally fixed to the size of the population strata for which a 20% prevalence of myopia, 5% epsilon, and a 95% confidence interval were hypothesized. We studied IOP, CCT, and DM and their relationships by calculating the mean, standard deviation, 95% confidence interval for the mean, median, Fisher’s asymmetry coefficient, range (maximum, minimum, and the Brown-Forsythe’s robust test for each variable (IOP, CCT, and DM.Results: In the adult myopic population of Almeria aged 20 to 40 years (mean of 29.8, the mean overall CCT was 550.12 µm. The corneas of men were thicker than those of women (P = 0.014. CCT was stable as no significant differences were seen in the 20- to 40-year-old subjects’ CCT values. The mean overall IOP was 13.60 mmHg. Men had a higher IOP than women (P = 0.002. Subjects over 30 years (13.83 had a higher IOP than those under 30 (13.38 (P = 0.04. The mean overall DM was -4.18 diopters. Men had less myopia than women (P < 0.001. Myopia was stable in the

  8. Genome-wide analysis of central corneal thickness in primary open-angle glaucoma cases in the NEIGHBOR and GLAUGEN consortia.

    Science.gov (United States)

    Ulmer, Megan; Li, Jun; Yaspan, Brian L; Ozel, Ayse Bilge; Richards, Julia E; Moroi, Sayoko E; Hawthorne, Felicia; Budenz, Donald L; Friedman, David S; Gaasterland, Douglas; Haines, Jonathan; Kang, Jae H; Lee, Richard; Lichter, Paul; Liu, Yutao; Pasquale, Louis R; Pericak-Vance, Margaret; Realini, Anthony; Schuman, Joel S; Singh, Kuldev; Vollrath, Douglas; Weinreb, Robert; Wollstein, Gadi; Zack, Donald J; Zhang, Kang; Young, Terri; Allingham, R Rand; Wiggs, Janey L; Ashley-Koch, Allison; Hauser, Michael A

    2012-07-03

    To investigate the effects of central corneal thickness (CCT)-associated variants on primary open-angle glaucoma (POAG) risk using single nucleotide polymorphisms (SNP) data from the Glaucoma Genes and Environment (GLAUGEN) and National Eye Institute (NEI) Glaucoma Human Genetics Collaboration (NEIGHBOR) consortia. A replication analysis of previously reported CCT SNPs was performed in a CCT dataset (n = 1117) and these SNPs were then tested for association with POAG using a larger POAG dataset (n = 6470). Then a CCT genome-wide association study (GWAS) was performed. Top SNPs from this analysis were selected and tested for association with POAG. cDNA libraries from fetal and adult brain and ocular tissue samples were generated and used for candidate gene expression analysis. Association with one of 20 previously published CCT SNPs was replicated: rs12447690, near the ZNF469 gene (P = 0.001; β = -5.08 μm/allele). None of these SNPs were significantly associated with POAG. In the CCT GWAS, no SNPs reached genome-wide significance. After testing 50 candidate SNPs for association with POAG, one SNP was identified, rs7481514 within the neurotrimin (NTM) gene, that was significantly associated with POAG in a low-tension subset (P = 0.00099; Odds Ratio [OR] = 1.28). Additionally, SNPs in the CNTNAP4 gene showed suggestive association with POAG (top SNP = rs1428758; P = 0.018; OR = 0.84). NTM and CNTNAP4 were shown to be expressed in ocular tissues. The results suggest previously reported CCT loci are not significantly associated with POAG susceptibility. By performing a quantitative analysis of CCT and a subsequent analysis of POAG, SNPs in two cell adhesion molecules, NTM and CNTNAP4, were identified and may increase POAG susceptibility in a subset of cases.

  9. Corneal biomechanical properties from air-puff corneal deformation imaging

    Science.gov (United States)

    Marcos, Susana; Kling, Sabine; Bekesi, Nandor; Dorronsoro, Carlos

    2014-02-01

    The combination of air-puff systems with real-time corneal imaging (i.e. Optical Coherence Tomography (OCT), or Scheimpflug) is a promising approach to assess the dynamic biomechanical properties of the corneal tissue in vivo. In this study we present an experimental system which, together with finite element modeling, allows measurements of corneal biomechanical properties from corneal deformation imaging, both ex vivo and in vivo. A spectral OCT instrument combined with an air puff from a non-contact tonometer in a non-collinear configuration was used to image the corneal deformation over full corneal cross-sections, as well as to obtain high speed measurements of the temporal deformation of the corneal apex. Quantitative analysis allows direct extraction of several deformation parameters, such as apex indentation across time, maximal indentation depth, temporal symmetry and peak distance at maximal deformation. The potential of the technique is demonstrated and compared to air-puff imaging with Scheimpflug. Measurements ex vivo were performed on 14 freshly enucleated porcine eyes and five human donor eyes. Measurements in vivo were performed on nine human eyes. Corneal deformation was studied as a function of Intraocular Pressure (IOP, 15-45 mmHg), dehydration, changes in corneal rigidity (produced by UV corneal cross-linking, CXL), and different boundary conditions (sclera, ocular muscles). Geometrical deformation parameters were used as input for inverse finite element simulation to retrieve the corneal dynamic elastic and viscoelastic parameters. Temporal and spatial deformation profiles were very sensitive to the IOP. CXL produced a significant reduction of the cornea indentation (1.41x), and a change in the temporal symmetry of the corneal deformation profile (1.65x), indicating a change in the viscoelastic properties with treatment. Combining air-puff with dynamic imaging and finite element modeling allows characterizing the corneal biomechanics in-vivo.

  10. Layer thickness measurement using the X-ray fluorescence principle

    International Nuclear Information System (INIS)

    Mengelkamp, B.

    1980-01-01

    Curium 244 having a gamma energy of about 15.5 keV is used as excitation emitter for contactless and continuous measuring of the thickness of metallic layers on iron strip. Soft gamma radiation is absorbed in matter according to the photo effect, so that X-ray fluorescence radiation is generated in the matter, which depends on the element and is radiated to all sides. For instance, it amounts for iron 6.4 keV and is measured with a specific ionisation chamber for this energy range. With increasing atomic number of the elements, the energy of fluorescence radiation increases and hence also the emission signal of the detector. The prerequisite for a usable measuring effect is an element distance of at least two and the thickness of the layer to be measured being in an optimum range. A signal dependent on the thickness of the layer is produced either by absorption of iron radiation (absorption method - aluminium and tin) or by build-up radiation of the material of the layer (emission method - zinc and lead). (orig./GSCH) [de

  11. DNA Measurement of Overlapping Cell Nuclei in Thick Tissue Sections

    Directory of Open Access Journals (Sweden)

    Liang Ji

    1997-01-01

    Full Text Available The paper describes an improved image analysis procedure for measuring the DNA content of cell nuclei in thick sections of liver tissue by absorption densitometry. Whereas previous methods only permitted the analysis of isolated nuclei, the new technique enables both isolated and overlapping nuclei to be measured. A 3D segmentation procedure determines whether each object is an isolated nucleus or a pair of overlapping nuclei; in the latter case the combined optical density is redistributed to the individual nuclei. A selection procedure ensures that only complete nuclei are measured.

  12. MEASUREMENT OF RNFL THICKNESS USING OCT IMAGES FOR GLAUCOMA DETECTION

    Directory of Open Access Journals (Sweden)

    Dhivyabharathi

    2013-08-01

    Full Text Available The thickness of retinal nerve fiber layer (RNFL is one of the pompous parameters for assessing the disease, Glaucoma. A substantial amount of vision can be lost before the patient becomes aware of any defect. Optical Coherence Tomography (OCT provides enhanced depth and clarity of viewing tissues with high resolution compared with other medical imaging devices. It examines the living tissue non-invasively. This paper presents an automatic method to find the thickness of RNFL using OCT images. The proposed algorithm first extracts all the layers present in the OCT image by texture segmentation using Gabor filter method and an algorithm is then developed to segment the RNFL. The thickness measurement of RNFL is automatically displayed based on pixel calculation. The calculated thickness values are compared with the original values obtained from hospital. The result shows that the proposed algorithm is efficient in segmenting the region of interest without manual intervention. The effectiveness of the proposed method is proved statistically by the performance analysis.

  13. Measurement Of Lead Equivalent Thickness For Irradiation Room: An Analysis

    International Nuclear Information System (INIS)

    Mohd Khalid Matori; Azuhar Ripin; Husaini Salleh; Mohd Khairusalih Mohd Zin; Muhammad Jamal Muhd Isa; Mohd Faizal Abdul Rahman

    2014-01-01

    The Malaysian Ministry of Health (MOH) has established that the irradiation room must have a sufficient thickness of shielding to ensure that requirements for the purpose of radiation protection of patients, employees and the public are met. This paper presents a technique using americium-241 source to test and verify the integrity of the shielding thickness in term of lead equivalent for irradiation room at health clinics own by MOH. Results of measurement of 8 irradiation rooms conducted in 2014 were analyzed for this presentation. Technical comparison of the attenuation of gamma rays from Am-241 source through the walls of the irradiation room and pieces of lead were used to assess the lead equivalent thickness of the walls. Results showed that almost all the irradiation rooms tested meet the requirements of the Ministry of Health and is suitable for the installation of the intended diagnostic X-ray apparatus. Some specific positions such as door knobs and locks, electrical plug sockets were identified with potential to not met the required lead equivalent thickness hence may contribute to higher radiation exposure to workers and the public. (author)

  14. Does air gas aesthesiometry generate a true mechanical stimulus for corneal sensitivity measurement?

    Science.gov (United States)

    Nosch, Daniela S; Pult, Heiko; Albon, Julie; Purslow, Christine; Murphy, Paul J

    2018-03-01

    Belmonte Ocular Pain Meter (OPM) air jet aesthesiometry overcomes some of the limitations of the Cochet-Bonnet aesthesiometer. However, for true mechanical corneal sensitivity measurement, the airflow stimulus temperature of the aesthesiometer must equal ocular surface temperature (OST), to avoid additional response from temperature-sensitive nerves. The aim of this study was to determine: (A) the stimulus temperature inducing no or least change in OST; and (B) to evaluate if OST remains unchanged with different stimulus durations and airflow rates. A total of 14 subjects (mean age 25.14 ± 2.18 years; seven women) participated in this clinical cohort study: (A) OST was recorded using an infrared camera (FLIR A310) during the presentation of airflow stimuli, at five temperatures, ambient temperature (AT) +5°C, +10°C, +15°C, +20°C and +30°C, using the OPM aesthesiometer (duration three seconds; over a four millimetre distance; airflow rate 60 ml/min); and (B) OST measurements were repeated with two stimulus temperatures (AT +10°C and +15°C) while varying stimulus durations (three seconds and five seconds) and airflow rates (30, 60, 80 and 100 ml/min). Inclusion criteria were age measures (analysis of variance) and appropriate post-hoc t-tests were applied. (A) Stimulus temperatures of AT +10°C and +15°C induced the least changes in OST (-0.20 ± 0.13°C and 0.08 ± 0.05°C). (B) OST changes were statistically significant with both stimulus temperatures and increased with increasing airflow rates (p air stimulus of the Belmonte OPM because its air jet stimulus with mechanical setting is likely to have a thermal component. Appropriate stimulus selection for an air jet aesthesiometer must incorporate stimulus temperature control that can vary with stimulus duration and airflow rate. © 2017 Optometry Australia.

  15. X-ray thickness measurement of aluminum alloys

    International Nuclear Information System (INIS)

    Albert, J.J.

    1976-01-01

    The theory of x-ray thickness gauging is extended to reveal the conditions under which a fixed anode voltage is ideal. A mathematical model of an alloy and computations reveal that two voltages can be used to measure the aluminum alloys with an error of roughly 1 percent, determined by the tolerance on manganese content rather than the large errors ordinarily a consequence of the tolerances on copper and zinc content. Implementation is discussed

  16. Refining enamel thickness measurements from B-mode ultrasound images.

    Science.gov (United States)

    Hua, Jeremy; Chen, Ssu-Kuang; Kim, Yongmin

    2009-01-01

    Dental erosion has been growing increasingly prevalent with the rise in consumption of heavy starches, sugars, coffee, and acidic beverages. In addition, various disorders, such as Gastroenterological Reflux Disease (GERD), have symptoms of rapid rates of tooth erosion. The measurement of enamel thickness would be important for dentists to assess the progression of enamel loss from all forms of erosion, attrition, and abrasion. Characterizing enamel loss is currently done with various subjective indexes that can be interpreted in different ways by different dentists. Ultrasound has been utilized since the 1960s to determine internal tooth structure, but with mixed results. Via image processing and enhancement, we were able to refine B-mode dental ultrasound images for more accurate enamel thickness measurements. The mean difference between the measured thickness of the occlusal enamel from ultrasound images and corresponding gold standard CT images improved from 0.55 mm to 0.32 mm with image processing (p = 0.033). The difference also improved from 0.62 to 0.53 mm at the buccal/lingual enamel surfaces, but not significantly (p = 0.38).

  17. Dynamic corneal deformation response and integrated corneal tomography

    Directory of Open Access Journals (Sweden)

    Marcella Q Salomão

    2018-01-01

    Full Text Available Measuring corneal biomechanical properties is still challenging. There are several clinical applications for biomechanical measurements, including the detection of mild or early forms of ectatic corneal diseases. This article reviews clinical applications for biomechanical measurements provided by the Corvis ST dynamic non contact tonometer

  18. Optical Coherence Tomography–Based Corneal Power Measurement and Intraocular Lens Power Calculation Following Laser Vision Correction (An American Ophthalmological Society Thesis)

    Science.gov (United States)

    Huang, David; Tang, Maolong; Wang, Li; Zhang, Xinbo; Armour, Rebecca L.; Gattey, Devin M.; Lombardi, Lorinna H.; Koch, Douglas D.

    2013-01-01

    Purpose: To use optical coherence tomography (OCT) to measure corneal power and improve the selection of intraocular lens (IOL) power in cataract surgeries after laser vision correction. Methods: Patients with previous myopic laser vision corrections were enrolled in this prospective study from two eye centers. Corneal thickness and power were measured by Fourier-domain OCT. Axial length, anterior chamber depth, and automated keratometry were measured by a partial coherence interferometer. An OCT-based IOL formula was developed. The mean absolute error of the OCT-based formula in predicting postoperative refraction was compared to two regression-based IOL formulae for eyes with previous laser vision correction. Results: Forty-six eyes of 46 patients all had uncomplicated cataract surgery with monofocal IOL implantation. The mean arithmetic prediction error of postoperative refraction was 0.05 ± 0.65 diopter (D) for the OCT formula, 0.14 ± 0.83 D for the Haigis-L formula, and 0.24 ± 0.82 D for the no-history Shammas-PL formula. The mean absolute error was 0.50 D for OCT compared to a mean absolute error of 0.67 D for Haigis-L and 0.67 D for Shammas-PL. The adjusted mean absolute error (average prediction error removed) was 0.49 D for OCT, 0.65 D for Haigis-L (P=.031), and 0.62 D for Shammas-PL (P=.044). For OCT, 61% of the eyes were within 0.5 D of prediction error, whereas 46% were within 0.5 D for both Haigis-L and Shammas-PL (P=.034). Conclusions: The predictive accuracy of OCT-based IOL power calculation was better than Haigis-L and Shammas-PL formulas in eyes after laser vision correction. PMID:24167323

  19. Corneal Laceration

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    Full Text Available ... Tips & Prevention News Ask an Ophthalmologist Patient Stories Español Eye Health / Eye Health A-Z Corneal Laceration ... Laceration Treatment What Is Corneal Laceration? Leer en Español: ¿Qué es una laceración de la córnea? Written ...

  20. Corneal Transplantation

    DEFF Research Database (Denmark)

    Hjortdal, Jesper Østergaard

    with less risk of rejection episodes. Besides covering updated chapters on penetrating keratoplasty, and anterior and posterior lamellar procedures, this textbook also gives a thorough overview of the history of corneal transplantation and a detailed presentation of the microstructural components...... and to assist fellows and corneal surgeons in their advice and selection of patients for the best surgical procedure considering benefi ts and risks....

  1. Corneal clarity measurements in healthy volunteers across different age groups: Observational study.

    Science.gov (United States)

    Alzahrani, Khaled; Carley, Fiona; Brahma, Arun; Morley, Debbie; Hillarby, M Chantal

    2017-11-01

    The aim of this study was to standardize and investigate the changes in corneal clarity with age. Densitometry software for the Oculus Pentacam was used to examine corneal clarity at different age groups.A total of 192 eyes from 97 healthy participants were included in this cohort comparative nonrandomized, cross-sectional study. An Oculus Pentcam was used to image the cornea of healthy participants grouped by age (between 10 and 70 years old). Data from the densitometry output have been used to determine clarity in concentric zones and different depths of the cornea.Corneal densitometry (CD) across all ages showed significant differences between groups when divided into the following layers: anterior, central, and posterior or divided into 0 to 2, 2 to 6, and 6 to 10 mm concentric zones (P age in all 3 layers of the periphery (6-10 mm) (P age group had lower clarity than the 20 to 30-age group (P age is differed when the cornea is divided into layers and zones. This study suggests that there are other factors that may play an essential role in corneal clarity as well as age.

  2. Measurement of the thickness of the bronchial epithelium

    International Nuclear Information System (INIS)

    Bowden, D.H.; Baldwin, F.

    1989-02-01

    Cancer of the lung in uranium miners is thought to be related to the inhalation of gaseous radon daughters which become attached to molecules of water vapour or to dust particles. Since, the depth of tissue penetration by alpha particles is short, the thickness of the epithelium that lines the bronchial tree may be a critical factor in the development of cancers at specific sites in the lung. The objectives of the present study were: 1) to measure the thickness of human bronchial epithelium; 2) to determine the distribution and depth of the nuclei of basal cells in the bronchial epithelium; and 3) to compare these parameters in groups of smokers and non-smokers. Twenty-nine surgically removed specimens of the lung were examined (26 smokers, 3 non-smokers). The specimens were fixed and prepared for examination by light and electron microscopy. Blocks of tissue were oriented so that the maximum number of bronchi were cut in cross-section; measurements included bronchi of all sizes from bronchial generations (1≥ 9.01 mm) diameter to the smallest bronchioles, generations 7 - 16 (0.26 - 2.0 mm). Comparison of measurements in smokers and non-smokers show no significant differences, so that the 29 cases are considered to represent a homogeneous group. With progressive divisions of the bronchi, the epithelium decreases in thickness. Of more importance are the figures relating to the distance from the cell surface to the underlying nucleus. Here too, with the exception of goblet cells, the measurements are significantly smaller in generations 7 - 16 than in generation 1

  3. Repeatability and Reproducibility of Retinal Nerve Fiber Layer Parameters Measured by Scanning Laser Polarimetry with Enhanced Corneal Compensation in Normal and Glaucomatous Eyes.

    Science.gov (United States)

    Ara, Mirian; Ferreras, Antonio; Pajarin, Ana B; Calvo, Pilar; Figus, Michele; Frezzotti, Paolo

    2015-01-01

    To assess the intrasession repeatability and intersession reproducibility of peripapillary retinal nerve fiber layer (RNFL) thickness parameters measured by scanning laser polarimetry (SLP) with enhanced corneal compensation (ECC) in healthy and glaucomatous eyes. One randomly selected eye of 82 healthy individuals and 60 glaucoma subjects was evaluated. Three scans were acquired during the first visit to evaluate intravisit repeatability. A different operator obtained two additional scans within 2 months after the first session to determine intervisit reproducibility. The intraclass correlation coefficient (ICC), coefficient of variation (COV), and test-retest variability (TRT) were calculated for all SLP parameters in both groups. ICCs ranged from 0.920 to 0.982 for intravisit measurements and from 0.910 to 0.978 for intervisit measurements. The temporal-superior-nasal-inferior-temporal (TSNIT) average was the highest (0.967 and 0.946) in normal eyes, while nerve fiber indicator (NFI; 0.982) and inferior average (0.978) yielded the best ICC in glaucomatous eyes for intravisit and intervisit measurements, respectively. All COVs were under 10% in both groups, except NFI. TSNIT average had the lowest COV (2.43%) in either type of measurement. Intervisit TRT ranged from 6.48 to 12.84. The reproducibility of peripapillary RNFL measurements obtained with SLP-ECC was excellent, indicating that SLP-ECC is sufficiently accurate for monitoring glaucoma progression.

  4. Measuring plate thickness using spatial local wavenumber filtering

    International Nuclear Information System (INIS)

    Kang, To; Han, Soon Woo; Park, Jin Ho; Lee, Jeong Han; Park, Gyu Hae; Jeon, Jun Young

    2016-01-01

    Corrosion on the surface of a structure can generate cracks or cause walls to thin. This can lead to fracturing, which can eventually lead to fatalities and property loss. In an effort to prevent this, laser imaging technology has been used over the last ten years to detect thin-plate structure, or relatively thin piping. The most common laser imaging was used to develop a new technology for inspecting and imaging a desired area in order to scan various structures for thin-plate structure and thin piping. However, this method builds images by measuring waves reflected from defects, and subsequently has a considerable time delay of a few milliseconds at each scanning point. In addition, the complexity of the system is high, due to additional required components, such as laser-focusing parts. This paper proposes a laser imaging method with an increased scanning speed, based on excitation and the measurement of standing waves in structures. The wavenumber of standing waves changes at sections with a geometrical discontinuity, such as thickness. Therefore, it is possible to detect defects in a structure by generating standing waves with a single frequency and scanning the waves at each point by with the laser scanning system. The proposed technique is demonstrated on a wall-thinned plate with a linear thickness variation

  5. Measurement of biofilm thickness. An effective Legionella risk assessment tool

    Energy Technology Data Exchange (ETDEWEB)

    Foret, Christophe [BKG France, Arnage (France); Martemianov, Serguei [Poitiers Univ. (FR). Lab. of Thermal Study (LET); Moscow Univ. (Russian Federation). Frumkin Inst. of Physical Chemistry and Electrochemistry; Hater, Wolfgang [BK Giulini GmbH, Duesseldorf (Germany); Merlet, Nicole; Chaussec, Guenole; Tribollet, Bernard

    2010-02-15

    The best way to prevent the risk of bacterial growth in water systems is to monitor and control the microorganisms (biofilm) attached to pipe walls. Three years of laboratory research led two Centre National de Recherche Scientifique (French National Center for Scientific Research) teams (UMR 6008 and UPR 15) to develop a tool designed to determine the average biofilm thickness. The average biofilm thickness measurements carried out on pilot plants fed with natural water were sufficiently accurate and sensitive to monitor the formation and development of biofilm in a water system and to determine the efficiency of the applied treatments. The implementation of appropriate treatments (type and dose of the treatment product) leads to a significant reduction in or even complete removal of the porous layer on the material surface. A reduction of the attached biomass, measured by the sensor, is connected to a decrease in the density of the bacterial attached to the material (viable flora in the plate count agar environment). (orig.)

  6. Online terahertz thickness measurement in films and coatings

    Science.gov (United States)

    Duling, Irl N.; White, Jeffrey S.

    2017-02-01

    Pulsed terahertz systems are currently being deployed for online process control and quality control of multi-layered products for use in the building products and aerospace industries. While many laboratory applications of terahertz can allow waveforms to be acquired at rates of 1 - 40 Hz, online applications require measurement rates of in excess of 100Hz. The existing technologies of thickness measurement (nuclear, x-ray, or laser gauges) have rates between 100 and 1000 Hz. At these rates, the single waveform bandwidth must still remain at 2THz or above to allow thinner layers to be measured. In the applications where terahertz can provide unique capability (e.g. multi-layer thickness, delamination, density) long-term stability must be guaranteed within the tolerance required by the measurement. This can mean multi-day stability of less than a micron. The software that runs on these systems must be flexible enough to allow multiple product configurations, while maintaining the simplicity required by plant operators. The final requirement is to have systems that can withstand the environmental conditions of the measurement. This might mean qualification in explosive environments, or operation in hot, wet or dusty environments. All of these requirements can put restrictions on not only the voltage of electronic circuitry used, but also the wavelength and optical power used for the transmitter and receiver. The application of terahertz systems to online process control presents unique challenges that not only effect the physical design of the system, but can also effect the choices made on the terahertz technology itself.

  7. Changes in corneal sensitivity following cross-linking for progressive early-stage keratoconus

    Directory of Open Access Journals (Sweden)

    Anelise de Medeiros Lago

    2014-04-01

    Full Text Available Purpose: To evaluate changes in corneal sensitivity following corneal cross-linking (CXL in patients with progressive earlier stage keratoconus. Methods: Thirty-eight eyes of 19 patients (11 women, 8 men were included in a prospective, nonrandomized clinical study. The mean patient age was 22 years (range, 18-26 years. Inclusion criteria were early stage bilateral progressive keratoconus, a transparent cornea, and a thickness of ≥440 µm in the thinnest area of the cornea. Using the Cochet-Bonnet esthesiometer, central corneal sensitivity was measured before surgery, 7 days after surgery, and once a month thereafter until recovery of baseline preoperative levels. Central corneal sensitivity >40 mm was considered normal. Results: Corneal sensitivity gradually returned to preoperative levels in all treated eyes. The mean central corneal sensitivity was 52.2, 24.0, 38.2, 42.5, 50.0, and 52.5 mm before surgery, 7 days after surgery, and at 1, 2, 3, and 4 months after surgery, respectively. Normal levels of corneal sensation, but not baseline (preoperative levels, were observed 2 months after surgery. The preoperative levels were observed 3 months after surgery. Conclusions: Our results suggest that central corneal sensitivity can be decreased for as long as 3 months after CXL for progressive earlier stage keratoconus.

  8. Corneal Laceration

    Medline Plus

    Full Text Available ... to Full Corneal Transplantation Nov 29, 2016 Follow The Academy Professionals: Education Guidelines News Multimedia Public & Patients: Contact Us About the Academy Jobs at the Academy Financial Relationships with Industry ...

  9. Influence of corneal parameters in keratoconus on IOP readings obtained with different tonometers.

    Science.gov (United States)

    Firat, Penpe Gul; Orman, Gozde; Doganay, Selim; Demirel, Soner

    2013-03-01

    Accurate intraocular pressure (IOP) measurement is important but of unsure reliability in patients with keratoconus. Different types and models of tonometers are available. This study investigated the influence of corneal parameters on IOP readings obtained by a Goldmann applanation tonometer, a non-contact tonometer and a dynamic contour tonometer. IOP readings with the Goldmann applanation, non-contact and dynamic contour tonometers were obtained from 52 patients with keratoconus and from 50 normal subjects and their corneal parameters were measured using a Pentacam. The mean IOP measurements in keratoconus obtained with the Goldmann applanation, non-contact and dynamic contour tonometers were statistically significantly different from the mean IOP measurements in the normal subjects (p contact tonometers but not on the dynamic contour tonometer. In the control group, thinnest and central corneal thicknesses had a significant effect on findings with the Goldmann and non-contact tonometers but not on the dynamic contour tonometer. The corneal volume (CV) had no significant effect on the three tonometers in both groups. The corneal parameters affecting the IOP readings of the Goldmann applanation tonometers, non-contact tonometers and the dynamic contour tonometers are not the same. While the Goldmann applanation and non-contact tonometers were significantly affected by the corneal parameters that were measured, the dynamic contour tonometer was not affected by any of these corneal parameters. © 2013 The Authors. Clinical and Experimental Optometry © 2013 Optometrists Association Australia.

  10. Measurement of the through thickness compression of a battery separator

    Science.gov (United States)

    Yan, Shutian; Huang, Xiaosong; Xiao, Xinran

    2018-04-01

    The mechanical integrity of the separator is critical to the reliable operation of a battery. Due to its minimal thickness, compression experiments with a single/a few layers of separator are difficult to perform. In this work, a capacitance based displacement set-up has been developed for the measurement of the through thickness direction (TTD) compression stress-strain behavior of the separator and the investigation of its interaction with the electrode. The experiments were performed for a stack of two layers of Celgard 2400 separator, NMC cathode, and separator/NMC cathode/separator stack in both dry and wet (i.e. submersed in dimethyl carbonate DMC) conditions. The experimental results reveal that the separator compression modulus can be significantly affected by the presence of DMC. The iso-stress based rule of mixtures was used to compute the compressive stress-strain curve for the stack from that of the separator and NMC layer. The computed curve agreed with the experimental curve reasonably well up to about 0.16 strain but deviated significantly to a softer response at higher strains. The results suggest that, in the stack, the TTD compressive deformation of the separator is influenced by the NMC cathode.

  11. Measurement of wall thickness with electrodynamic test heads

    International Nuclear Information System (INIS)

    Koch, R.; Maurer, A.

    1993-01-01

    Starting from the boundary conditions fixed by the physical properties of the electromagnetic/acoustic conversion and the operating limits which result from these for the sensors used, the use of electro-dynamic ultrasonic transducers for measuring wall thickness and double checks in plants for automatic production inspection and production control is shown. The sensor itself is the heart of a test system, but only the equipment and plant concepts surrounding the sensor make economic solution of the test problem possible. The quality of the signals which are supplied by a sensor, determines the quality of a test system. This can only be achieved by optimising all parts of a complex automatic test rig, such as the test head, mechanics, electronics and evaluation for the test problem concerned. (orig./HP) [de

  12. Thick Films acoustic sensors devoted to MTR environment measurements. Thick Films acoustic sensors devoted to Material Testing Reactor environment measurements

    Energy Technology Data Exchange (ETDEWEB)

    Very, F.; Rosenkrantz, E.; Combette, P.; Ferrandis, J.Y. [University Montpellier, IES, UMR 5214, F-34000, Montpellier (France); CNRS, IES, UMR 5214, F-34000, Montpellier (France); Fourmentel, D.; Destouches, C.; Villard, J.F. [CEA, DEN, Instrumentation Sensors and Dosimetry Laboratory, Cadarache, F-13108 St Paul lez Durance (France)

    2015-07-01

    The development of advanced instrumentation for in-pile experiments in Material Testing Reactor constitutes a main goal for the improvement of the nuclear fuel behavior knowledge. An acoustic method for fission gas release detection was tested with success during a first experiment called REMORA 3 in 2010 and 2011, and the results were used to differentiate helium and fission gas release kinetics under transient operating conditions. This experiment was lead at OSIRIS reactor (CEA Saclay, France). The maximal temperature on the sensor during the irradiation was about 150 deg. C. In this paper we present a thick film transducer produce by screen printing process. The screen printing of piezoelectric offers a wide range of possible applications for the development of acoustic sensors and piezoelectric structure for measurements in high temperature environment. We firstly produced a Lead Zirconate Titanate (PZT) based paste composed of Pz27 powder from Ferroperm, CF7575 glass, and organic solvent ESL 400. Likewise a Bismuth Titanate based paste synthesized in our laboratory was produced. With these inks we produced thick film up to 130 μm by screen printing process. Material properties characterizations of these thick-film resonators are essential for device design and applications. The piezoelectric coefficients d33 and pyro-electric P(T) coefficient are investigated. The highest P(T) and d33 are respectively 80 μC.m{sup -2}.K{sup -1} and 130 μC.N{sup -1} for the PZT transducer -which validates the fabrication process-. In view of the development of this transducer oriented for high temperature and irradiation environment, we investigated the electrical properties of the transducers for different ranges of frequencies and temperature - from 20 Hz up to 40 MHz between 30 and 400 deg. C. We highlight the evolution of the impedance response and piezoelectric parameters of screen printed piezoelectric structures on alumina. Shortly an irradiation will be realized in

  13. Thick Films acoustic sensors devoted to MTR environment measurements. Thick Films acoustic sensors devoted to Material Testing Reactor environment measurements

    International Nuclear Information System (INIS)

    Very, F.; Rosenkrantz, E.; Combette, P.; Ferrandis, J.Y.; Fourmentel, D.; Destouches, C.; Villard, J.F.

    2015-01-01

    The development of advanced instrumentation for in-pile experiments in Material Testing Reactor constitutes a main goal for the improvement of the nuclear fuel behavior knowledge. An acoustic method for fission gas release detection was tested with success during a first experiment called REMORA 3 in 2010 and 2011, and the results were used to differentiate helium and fission gas release kinetics under transient operating conditions. This experiment was lead at OSIRIS reactor (CEA Saclay, France). The maximal temperature on the sensor during the irradiation was about 150 deg. C. In this paper we present a thick film transducer produce by screen printing process. The screen printing of piezoelectric offers a wide range of possible applications for the development of acoustic sensors and piezoelectric structure for measurements in high temperature environment. We firstly produced a Lead Zirconate Titanate (PZT) based paste composed of Pz27 powder from Ferroperm, CF7575 glass, and organic solvent ESL 400. Likewise a Bismuth Titanate based paste synthesized in our laboratory was produced. With these inks we produced thick film up to 130 μm by screen printing process. Material properties characterizations of these thick-film resonators are essential for device design and applications. The piezoelectric coefficients d33 and pyro-electric P(T) coefficient are investigated. The highest P(T) and d33 are respectively 80 μC.m -2 .K -1 and 130 μC.N -1 for the PZT transducer -which validates the fabrication process-. In view of the development of this transducer oriented for high temperature and irradiation environment, we investigated the electrical properties of the transducers for different ranges of frequencies and temperature - from 20 Hz up to 40 MHz between 30 and 400 deg. C. We highlight the evolution of the impedance response and piezoelectric parameters of screen printed piezoelectric structures on alumina. Shortly an irradiation will be realized in order to

  14. A Study on the Thickness Measurement of Thin Film by Ultrasonic Wave

    International Nuclear Information System (INIS)

    Han, Eung Kyo; Lee, Jae Joon; Kim, Jae Yeol

    1988-01-01

    Recently, it is gradually raised necessity that thickness of thin film is measured accurately and managed in industrial circles and medical world. In this study, regarding to the thickness of film which is in opaque object and is beyond distance resolution capacity, thickness measurement was done by MEM-cepstrum analysis of received ultrasonic wave. In measurement results, film thickness which is beyond distance resolution capacity was measured accurately. And within thickness range that don't exist interference, thickness measurement by MEM-ceptrum analysis was impossible

  15. Clinical Factors Associated with Lamina Cribrosa Thickness in Patients with Glaucoma, as Measured with Swept Source Optical Coherence Tomography.

    Directory of Open Access Journals (Sweden)

    Kazuko Omodaka

    Full Text Available To investigate the influence of various risk factors on thinning of the lamina cribrosa (LC, as measured with swept-source optical coherence tomography (SS-OCT; Topcon.This retrospective study comprised 150 eyes of 150 patients: 22 normal subjects, 28 preperimetric glaucoma (PPG patients, and 100 open-angle glaucoma patients. Average LC thickness was determined in a 3 x 3 mm cube scan of the optic disc, over which a 4 x 4 grid of 16 points was superimposed (interpoint distance: 175 μm, centered on the circular Bruch's membrane opening. The borders of the LC were defined as the visible limits of the LC pores. The correlation of LC thickness with Humphrey field analyzer-measured mean deviation (MD; SITA standard 24-2, circumpapillary retinal nerve fiber layer thickness (cpRNFLT, the vertical cup-to-disc (C/D ratio, and tissue mean blur rate (MBR was determined with Spearman's rank correlation coefficient. The relationship of LC thickness with age, axial length, intraocular pressure (IOP, MD, the vertical C/D ratio, central corneal thickness (CCT, and tissue MBR was determined with multiple regression analysis. Average LC thickness and the correlation between LC thickness and MD were compared in patients with the glaucomatous enlargement (GE optic disc type and those with non-GE disc types, as classified with Nicolela's method.We found that average LC thickness in the 16 grid points was significantly associated with overall LC thickness (r = 0.77, P < 0.001. The measurement time for this area was 12.4 ± 2.4 minutes. Average LC thickness in this area had a correlation coefficient of 0.57 with cpRNFLT (P < 0.001 and 0.46 (P < 0.001 with MD. Average LC thickness differed significantly between the groups (normal: 268 ± 23 μm, PPG: 248 ± 13 μm, OAG: 233 ± 20 μm. Multiple regression analysis showed that MD (β = 0.29, P = 0.013, vertical C/D ratio (β = -0.25, P = 0.020 and tissue MBR (β = 0.20, P = 0.034 were independent variables significantly

  16. Preliminary study of the correlation between refractive error and corneal refractive power, corneal asphericity in myopic eye

    Directory of Open Access Journals (Sweden)

    Qi-Chao Han

    2014-05-01

    Full Text Available AIM: To investigate the correlation between myopic refractive error and relative factors, including the corneal refractive power, posterior refractive power, axial length, corneal asphericity coefficient Q value, central cornea thickness(CCTand intraocular pressure(IOP. METHODS:According to the degree of myopia measured by subjective refraction, 138 myopia patients were divided into three subgroups: mild group(-1.00D--3.00D, moderate group(-3.25D--6.00D, high group(>6.00D. The Pentacam anterior segment tomographer(Germany, Oculus Companywas used to measure the corneal refractive power, posterior refractive power, and corneal asphericity in the right eye. IOP, CCT and axial length were measured by a non-contact tonometer and A-scan ultrasonic, respectively. The data was analyzed with a Pearson correlation analysis and one-way ANOVA. RESULTS: The myopic refractive error was negatively correlated with the axial length(r=-0.682, Pr=0.009, P=0.925. The axial length was negatively correlated with corneal refractive power(r=-0.554, Pr=0.674, Pr=-0.375, P=0.01. There was no significantly correlation between the myopic refractive error and CCT, IOP(r=-0.138, P=0.141; r=-0.121, P=0.157. CONCLUSION:The corneal refractive power plays the role of emmetropization during the development of myopia. There is clinic significance for the correlation between Q value and refractive error, IOP to guide the corneal refractive surgery.

  17. Applications of corneal topography and tomography: a review.

    Science.gov (United States)

    Fan, Rachel; Chan, Tommy Cy; Prakash, Gaurav; Jhanji, Vishal

    2018-03-01

    Corneal imaging is essential for diagnosing and management of a wide variety of ocular diseases. Corneal topography is used to characterize the shape of the cornea, specifically, the anterior surface of the cornea. Most corneal topographical systems are based on Placido disc that analyse rings that are reflected off the corneal surface. The posterior corneal surface cannot be characterized using Placido disc technology. Imaging of the posterior corneal surface is useful for diagnosis of corneal ectasia. Unlike corneal topographers, tomographers generate a three-dimensional recreation of the anterior segment and provide information about the corneal thickness. Scheimpflug imaging is one of the most commonly used techniques for corneal tomography. The cross-sectional images generated by a rotating Scheimpflug camera are used to locate the anterior and posterior corneal surfaces. The clinical uses of corneal topography include, diagnosis of corneal ectasia, assessment of corneal astigmatism, and refractive surgery planning. This review will discuss the applications of corneal topography and tomography in clinical practice. © 2017 Royal Australian and New Zealand College of Ophthalmologists.

  18. Image-guided modified deep anterior lamellar keratoplasty (DALK) corneal transplant using intraoperative optical coherence tomography

    Science.gov (United States)

    Tao, Yuankai K.; LaBarbera, Michael; Ehlers, Justis P.; Srivastava, Sunil K.; Dupps, William J.

    2015-03-01

    Deep anterior lamellar keratoplasty (DALK) is an alternative to full-thickness corneal transplant and has advantages including the absence of allograft rejection; shortened duration of topical corticosteroid treatment and reduced associated risk of glaucoma, cataract, or infection; and enables use of grafts with poor endothelial quality. DALK begins by performing a trephination of approximately 80% stromal thickness, as measured by pachymetry. After removal of the anterior stoma, a needle is inserted into the residual stroma to inject air or viscoelastic to dissect Descemet's membrane. These procedures are inherently difficult and intraoperative rates of Descemet's membrane perforation between 4-39% have been reported. Optical coherence tomography (OCT) provides high-resolution images of tissue microstructures in the cornea, including Descemet's membrane, and allows quantitation of corneal layer thicknesses. Here, we use crosssectional intraoperative OCT (iOCT) measurements of corneal thickness during surgery and a novel micrometeradjustable biopsy punch to precision-cut the stroma down to Descemet's membrane. Our prototype cutting tool allows us to establish a dissection plane at the corneal endothelium interface, mitigates variability in cut-depths as a result of tremor, reduces procedure complexity, and reduces complication rates. iOCT-guided modified DALK procedures were performed on 47 cadaveric porcine eyes by non-experts and achieved a perforation rate of ~5% with a mean corneal dissection time care.

  19. Nondestructive testing technology for measurement coatings thickness on material

    International Nuclear Information System (INIS)

    Yang Mingtai; Wu Lunqiang; Zhang Lianping

    2008-01-01

    The principle, applicability range, advantage and disadvantage of electromagnetic, eddy current method, β backscatter method and XRF methods for nondestructive testing coating thickness of material have been reviewed. The relevant apparatus and manufacturers have been summarized. And the application and developmental direction of manufacturers for nondestructive testing coatings thickness has been foreshowed. (authors)

  20. In Vivo Corneal Biomechanical Properties with Corneal Visualization Scheimpflug Technology in Chinese Population

    Directory of Open Access Journals (Sweden)

    Ying Wu

    2016-01-01

    Full Text Available Purpose. To determine the repeatability of recalculated corneal visualization Scheimpflug technology (CorVis ST parameters and to study the variation of biomechanical properties and their association with demographic and ocular characteristics. Methods. A total of 783 healthy subjects were included in this study. Comprehensive ophthalmological examinations were conducted. The repeatability of the recalculated biomechanical parameters with 90 subjects was assessed by the coefficient of variation (CV and intraclass correlation coefficient (ICC. Univariate and multivariate linear regression models were used to identify demographic and ocular factors. Results. The repeatability of the central corneal thickness (CCT, deformation amplitude (DA, and first/second applanation time (A1/A2-time exhibited excellent repeatability (CV% ≤ 3.312% and ICC ≥ 0.929 for all measurements. The velocity in/out (Vin/out, highest concavity- (HC- radius, peak distance (PD, and DA showed a normal distribution. Univariate linear regression showed a statistically significant correlation between Vin, Vout, DA, PD, and HC-radius and IOP, CCT, and corneal volume, respectively. Multivariate analysis showed that IOP and CCT were negatively correlated with Vin, DA, and PD, while there was a positive correlation between Vout and HC-radius. Conclusion. The ICCs of the recalculated parameters, CCT, DA, A1-time, and A2-time, exhibited excellent repeatability. IOP, CCT, and corneal volume significantly influenced the biomechanical properties of the eye.

  1. Altered corneal biomechanical properties in children with osteogenesis imperfecta.

    Science.gov (United States)

    Lagrou, Lisa M; Gilbert, Jesse; Hannibal, Mark; Caird, Michelle S; Thomas, Inas; Moroi, Sayoko E; Bohnsack, Brenda L

    2018-04-07

    To evaluate biomechanical corneal properties in children with osteogenesis imperfecta (OI). A prospective, observational, case-control study was conducted on children 6-19 years of age diagnosed with OI. Patients with OI and healthy control subjects underwent complete ophthalmic examinations. Additional tests included Ocular Response Analyzer (ORA) and ultrasonic pachymetry. Primary outcomes were central corneal thickness (CCT), corneal hysteresis (CH), and corneal resistance factor (CRF). Intraocular pressure (IOP) was measured directly by either iCare or Goldmann applanation and indirectly by the ORA (Goldmann-correlated and corneal-compensated IOP). Statistically significant differences between OI and control groups were determined using independent samples t test. A total of 10 of 18 OI cases (mean age, 13 ± 4.37 years; 8 males) and 30 controls (mean age, 12.76 ± 2.62 years; 16 males) were able to complete the corneal biomechanics and pachymetry testing. Children with OI had decreased CH (8.5 ± 1.0 mm Hg vs 11.6 ± 1.2 mm Hg [P < 0.001]), CRF (9.0 ± 1.9 mm Hg vs 11.5 ± 1.5 [P < 0.001]) and CCT (449.8 ± 30.8 μm vs 568 ± 47.6 μm [P < 0.001]) compared to controls. The corneal-compensated IOP was significantly higher in OI cases (18.8 ± 3.1 mm Hg) than in controls (15.0 ± 1.6 mm Hg, P < 0.004), but there was no significant difference in Goldmann-correlated IOP (16.3 ± 4.2 mm Hg vs 15.8 ± 2.2 mm Hg). Collagen defects in OI alter corneal structure and biomechanics. Children with OI have decreased CH, CRF, and CCT, resulting in IOPs that are likely higher than measured by tonometry. These corneal alterations are present at a young age in OI. Affected individuals should be routinely screened for glaucoma and corneal pathologies. Copyright © 2018 American Association for Pediatric Ophthalmology and Strabismus. Published by Elsevier Inc. All rights reserved.

  2. Rotary union for use with ultrasonic thickness measuring probe

    Science.gov (United States)

    Nachbar, Henry D.

    1992-01-01

    A rotary union for rotatably supporting an ultrasonic probe operable to nondestructively measure the thickness of steam generator tubes to determine the amount of corrosion experienced by the tubes includes a stationary body having a bore therethrough and an outlet drain, and a fitting rotatably mounted within the upper end of the body. The fitting has a bore aligned with the bore of the body. An electrical cable positioned within a water supply tube in an annular arrangement passes through the bore of the body and the bore of the fitting. This annular arrangement, in turn, is positioned within a connector element which extends outwardly from the fitting bore and is connected to the ultrasonic probe. An elastomeric lower bushing seals the annular arrangement to the lower end of the rotary union body and an elastomeric upper bushing seals the connector element to the fitting to permit the connector element and the ultrasonic probe connected thereto to rotate with the fitting relative to the body. The lower and upper bushings permit water to be passed through the annular arrangement and into the ultrasonic probe and thereafter discharged between the annular arrangement and the connector element to the outlet drain of the rotary union body.

  3. Rotary union for use with ultrasonic thickness measuring probe

    International Nuclear Information System (INIS)

    Nachbar, H.D.

    1992-01-01

    A rotary union for rotatably supporting an ultrasonic probe operable to nondestructively measure the thickness of steam generator tubes to determine the amount of corrosion experienced by the tubes includes a stationary body having a bore therethrough and an outlet drain, and a fitting rotatably mounted within the upper end of the body. The fitting has a bore aligned with the bore of the body. An electrical cable positioned within a water supply tube in an annular arrangement passes through the bore of the body and the bore of the fitting. This annular arrangement, in turn, is positioned within a connector element which extends outwardly from the fitting bore and is connected to the ultrasonic probe. An elastomeric lower bushing seals the annular arrangement to the lower end of the rotary union body and an elastomeric upper bushing seals the connector element to the fitting to permit the connector element and the ultrasonic probe connected thereto to rotate with the fitting relative to the body. The lower and upper bushings permit water to be passed through the annular arrangement and into the ultrasonic probe and thereafter discharged between the annular arrangement and the connector element to the outlet drain of the rotary union body. 5 figs

  4. Topical Drug Formulations for Prolonged Corneal Anesthesia

    Science.gov (United States)

    Wang, Liqiang; Shankarappa, Sahadev A.; Tong, Rong; Ciolino, Joseph B.; Tsui, Jonathan H.; Chiang, Homer H.; Kohane, Daniel S.

    2013-01-01

    Purpose Ocular local anesthetics (OLA’s) currently used in routine clinical practice for corneal anesthesia are short acting and their ability to delay corneal healing makes them unsuitable for long-term use. In this study, we examined the effect on the duration of corneal anesthesia of the site-1 sodium channel blocker tetrodotoxin (TTX), applied with either proparacaine or the chemical permeation enhancer OTAB. The effect of test solutions on corneal healing was also studied. Methods Solutions of TTX, proparacaine, and OTAB, singly or in combination were applied topically to the rat cornea. The blink response, an indirect measure of corneal sensitivity, was recorded using a Cochet-Bonnet esthesiometer, and the duration of corneal anesthesia calculated. The effect of test compounds on the rate of corneal epithelialization was studied in vivo following corneal debridement. Results Combination of TTX and proparacaine resulted in corneal anesthesia that was 8–10 times longer in duration than that from either drug administered alone, while OTAB did not prolong anesthesia. The rate of corneal healing was moderately delayed following co-administration of TTX and proparacaine. Conclusion Co-administration of TTX and proparacaine significantly prolonged corneal anesthesia but in view of delayed corneal re-epithelialization, caution is suggested in use of the combination. PMID:23615270

  5. Thickness gauge for the measurement of the density of graphite

    International Nuclear Information System (INIS)

    Leveque, P.; Gasnier, M.; Hours, R.; Jouquet, G.; Rappeneau, J.; Tanguy, J.C.

    1961-01-01

    A thickness gauge was built, based on absorption of Bremsstrahlung generated in a Be target by a ( 90 Sr + 90 Y) β- source. This allows rapid and precise estimation (95 per cent probable error = 0.7 per cent) of the densities in slabs of graphite having a constant thickness of 25 ± 0.05 mm, the diameter of the beam being about 1 cm. Results obtained in this way are presented. (author) [fr

  6. Correlations between corneal and total wavefront aberrations

    Science.gov (United States)

    Mrochen, Michael; Jankov, Mirko; Bueeler, Michael; Seiler, Theo

    2002-06-01

    Purpose: Corneal topography data expressed as corneal aberrations are frequently used to report corneal laser surgery results. However, the optical image quality at the retina depends on all optical elements of the eye such as the human lens. Thus, the aim of this study was to investigate the correlations between the corneal and total wavefront aberrations and to discuss the importance of corneal aberrations for representing corneal laser surgery results. Methods: Thirty three eyes of 22 myopic subjects were measured with a corneal topography system and a Tschernig-type wavefront analyzer after the pupils were dilated to at least 6 mm in diameter. All measurements were centered with respect to the line of sight. Corneal and total wavefront aberrations were calculated up to the 6th Zernike order in the same reference plane. Results: Statistically significant correlations (p the corneal and total wavefront aberrations were found for the astigmatism (C3,C5) and all 3rd Zernike order coefficients such as coma (C7,C8). No statistically significant correlations were found for all 4th to 6th order Zernike coefficients except for the 5th order horizontal coma C18 (p equals 0.003). On average, all Zernike coefficients for the corneal aberrations were found to be larger compared to Zernike coefficients for the total wavefront aberrations. Conclusions: Corneal aberrations are only of limited use for representing the optical quality of the human eye after corneal laser surgery. This is due to the lack of correlation between corneal and total wavefront aberrations in most of the higher order aberrations. Besides this, the data present in this study yield towards an aberration balancing between corneal aberrations and the optical elements within the eye that reduces the aberration from the cornea by a certain degree. Consequently, ideal customized ablations have to take both, corneal and total wavefront aberrations, into consideration.

  7. Corneal topography

    DEFF Research Database (Denmark)

    Andersen, J.; Koch-Jensen, P.; Østerby, Ole

    1993-01-01

    The central corneal zone is depicted on keratoscope photographs using a small target aperture and a large object distance. Information on the peripheral area is included by employing a hemispherical target with a dense circular and radial pattern. On a 16 mm (R = 8 mm) reference steel sphere the ...

  8. Investigation of Overrun-Processed Porous Hyaluronic Acid Carriers in Corneal Endothelial Tissue Engineering.

    Directory of Open Access Journals (Sweden)

    Jui-Yang Lai

    Full Text Available Hyaluronic acid (HA is a linear polysaccharide naturally found in the eye and therefore is one of the most promising biomaterials for corneal endothelial regenerative medicine. This study reports, for the first time, the development of overrun-processed porous HA hydrogels for corneal endothelial cell (CEC sheet transplantation and tissue engineering applications. The hydrogel carriers were characterized to examine their structures and functions. Evaluations of carbodiimide cross-linked air-dried and freeze-dried HA samples were conducted simultaneously for comparison. The results indicated that during the fabrication of freeze-dried HA discs, a technique of introducing gas bubbles in the aqueous biopolymer solutions can be used to enlarge pore structure and prevent dense surface skin formation. Among all the groups studied, the overrun-processed porous HA carriers show the greatest biological stability, the highest freezable water content and glucose permeability, and the minimized adverse effects on ionic pump function of rabbit CECs. After transfer and attachment of bioengineered CEC sheets to the overrun-processed HA hydrogel carriers, the therapeutic efficacy of cell/biopolymer constructs was tested using a rabbit model with corneal endothelial dysfunction. Clinical observations including slit-lamp biomicroscopy, specular microscopy, and corneal thickness measurements showed that the construct implants can regenerate corneal endothelium and restore corneal transparency at 4 weeks postoperatively. Our findings suggest that cell sheet transplantation using overrun-processed porous HA hydrogels offers a new way to reconstruct the posterior corneal surface and improve endothelial tissue function.

  9. Mass thickness measurement of dual-sample by dual-energy X-rays

    International Nuclear Information System (INIS)

    Chen Mincong; Li Hongmei; Chen Ziyu; Shen Ji

    2008-01-01

    X-ray equivalent energy can be used to measure mass thicknesses of materials. Based on this, a method of mass thickness measurement of dual-sample was discussed. It was found that in the range of sample mass thickness under investigation, the equivalent mass attenuation coefficient of a component could be used to compute mass thicknesses of a dual-sample, with relative errors of less than 5%. Mass thickness measurement of a fish sample was performed, and the fish bone and flesh could be displayed separately and clearly by their own mass thicknesses. This indicates that the method is effective in mass thickness measurement of dual-sample of suitable thicknesses. (authors)

  10. Development of examination technique for oxide layer thickness measurement of irradiated fuel rods

    International Nuclear Information System (INIS)

    Koo, D. S.; Park, S. W.; Kim, J. H.; Seo, H. S.; Min, D. K.; Kim, E. K.; Chun, Y. B.; Bang, K. S.

    1999-06-01

    Technique for oxide layer thickness measurement of irradiated fuel rods was developed to measure oxide layer thickness and study characteristic of fuel rods. Oxide layer thickness of irradiated fuels were measured, analyzed. Outer oxide layer thickness of 3 cycle-irradiated fuel rods were 20 - 30 μm, inner oxide layer thickness 0 - 10 μm and inner oxide layer thickness on cracked cladding about 30 μm. Oxide layer thickness of 4 cycle-irradiated fuel rods were about 2 times as thick as those of 1 cycle-irradiated fuel rods. Oxide layer on lower region of irradiated fuel rods was thin and oxide layer from lower region to upper region indicated gradual increase in thickness. Oxide layer thickness from 2500 to 3000 mm showed maximum and oxide layer thickness from 3000 to top region of irradiated fuel rods showed decreasing trend. Inner oxide layer thicknesses of 4 cycle-irradiated fuel rod were about 8 μm at 750 - 3500 mm from the bottom end of fuel rod. Outer oxide layer thickness were about 8 μm at 750 - 1000 mm from the bottom end of fuel rod. These indicated gradual increase up to upper region from the bottom end of fuel rod. These indicated gradual increase up to upper region from the bottom end of fuel. Oxide layer thickness technique will apply safety evaluation and study of reactor fuels. (author). 6 refs., 14 figs

  11. Validation of Na,K-ATPase pump function of corneal endothelial cells for corneal regenerative medicine.

    Science.gov (United States)

    Hatou, Shin; Higa, Kazunari; Inagaki, Emi; Yoshida, Satoru; Kimura, Erika; Hayashi, Ryuhei; Tsujikawa, Motokazu; Tsubota, Kazuo; Nishida, Kohji; Shimmura, Shigeto

    2013-12-01

    Tissue-engineering approaches to cultivate corneal endothelial cells (CECs) or induce CECs from stem cells are under investigation for the treatment of endothelial dysfunction. Before clinical application, a validation method to determine the quality of these cells is required. In this study, we quantified the endothelial pump function required for maintaining the corneal thickness using rabbit CECs (RCECs) and a human CEC line (B4G12). The potential difference of RCECs cultured on a permeable polyester membrane (Snapwell), B4G12 cells on Snapwell, or B4G12 cells on a collagen membrane (CM6) was measured by an Ussing chamber system, and the effect of different concentrations of ouabain (Na,K-ATPase specific inhibitor) was obtained. A mathematical equation derived from the concentration curve revealed that 2 mM ouabain decreases pump function of RCECs to 1.0 mV, and 0.6 mM ouabain decreases pump function of B4G12 on CM6 to 1.0 mV. Ouabain injection into the anterior chamber of rabbit eyes at a concentration of pump function >1.0 mV is required to maintain the corneal thickness. These results can be used for standardization of CEC pump function and validation of tissue-engineered CEC sheets for clinical use.

  12. Corneal Epithelial Remodeling and Its Effect on Corneal Asphericity after Transepithelial Photorefractive Keratectomy for Myopia

    Directory of Open Access Journals (Sweden)

    Jie Hou

    2016-01-01

    Full Text Available Purpose. To evaluate the changes in epithelial thickness profile following transepithelial photorefractive keratectomy (T-PRK for myopia and to investigate the effect of epithelial remodeling on corneal asphericity. Methods. Forty-four patients (44 right eyes who underwent T-PRK were retrospectively evaluated. Epithelial thickness was measured using spectral-domain optical coherence tomography at different corneal zones (central, 2 mm; paracentral, 2–5 mm; and mid-peripheral, 5-6 mm preoperatively and at 1 week and 1, 3, and 6 months postoperatively. The correlation between the changes in corneal epithelial thickness (ΔCET and postoperative Q-value changes (ΔQ was analyzed 6 months postoperatively. Results. Epithelial thickness at 6 months showed a negative meniscus-like lenticular pattern with less central thickening, which increased progressively toward the mid-periphery (3.69±4.2, 5.19±3.8, and 6.23±3.9 μm at the center, paracenter, and mid-periphery, resp., P<0.01. A significant positive relationship was observed between epithelial thickening and ΔQ 6 months postoperatively (r=0.438, 0.580, and 0.504, resp., P<0.01. Conclusions. Significant epithelial thickening was observed after T-PRK and showed a lenticular change with more thickening mid-peripherally, resulting in increased oblateness postoperatively. Epithelial remodeling may modify the epithelial thickness profile after surface ablation refractive surgery for myopia.

  13. Radioisotope albedo method for measuring thickness of polymers coatings on metal basis

    International Nuclear Information System (INIS)

    Kapranov, B.I.; Myakin'kova, L.V.; Shaverin, V.A.

    1986-01-01

    Theoretical analysis of albedo thickness measuring of polymer coating-metal composite has been made and experimental studies of the range of tested thicknesses of polymer coating when different metal bases and radiation sources are used have been conducted. It is shown that the thickness of polymer coating on metal can be measured using backscattered γ-radiation in the energy range of 20-120 keV at the error 0.15-0.8 mm, at that, for thickness up to 23 mm the use of 147 Pm isotope can be defined as the optimum one; for thicknesses up to 40 mm 241 Am should be used; at thicknesses up to 60 mm - 57 Co. The AGAT-1 albedo gamma thickness gage, designed for measuring thickness of fiber glass coating up to 20 mm on metal base, is described

  14. Practicable methods for histological section thickness measurement in quantitative stereological analyses.

    Science.gov (United States)

    Matenaers, Cyrill; Popper, Bastian; Rieger, Alexandra; Wanke, Rüdiger; Blutke, Andreas

    2018-01-01

    The accuracy of quantitative stereological analysis tools such as the (physical) disector method substantially depends on the precise determination of the thickness of the analyzed histological sections. One conventional method for measurement of histological section thickness is to re-embed the section of interest vertically to its original section plane. The section thickness is then measured in a subsequently prepared histological section of this orthogonally re-embedded sample. However, the orthogonal re-embedding (ORE) technique is quite work- and time-intensive and may produce inaccurate section thickness measurement values due to unintentional slightly oblique (non-orthogonal) positioning of the re-embedded sample-section. Here, an improved ORE method is presented, allowing for determination of the factual section plane angle of the re-embedded section, and correction of measured section thickness values for oblique (non-orthogonal) sectioning. For this, the analyzed section is mounted flat on a foil of known thickness (calibration foil) and both the section and the calibration foil are then vertically (re-)embedded. The section angle of the re-embedded section is then calculated from the deviation of the measured section thickness of the calibration foil and its factual thickness, using basic geometry. To find a practicable, fast, and accurate alternative to ORE, the suitability of spectral reflectance (SR) measurement for determination of plastic section thicknesses was evaluated. Using a commercially available optical reflectometer (F20, Filmetrics®, USA), the thicknesses of 0.5 μm thick semi-thin Epon (glycid ether)-sections and of 1-3 μm thick plastic sections (glycolmethacrylate/ methylmethacrylate, GMA/MMA), as regularly used in physical disector analyses, could precisely be measured within few seconds. Compared to the measured section thicknesses determined by ORE, SR measures displayed less than 1% deviation. Our results prove the applicability

  15. Thickness profile measuring device for rolling metal bands or sheets

    International Nuclear Information System (INIS)

    Campas, J.J.; Terreaux, S.

    1995-01-01

    Previous radiometric thickness gages were affected by insufficient water proofing and limited cooling performances for the detection subsystem (in general specially designed photodiodes). This resulted in poor reliability and life expectancy, in particular when heavy humidity and constant radiative heat are present as for hot rolling in the metal industry. This new gage design brings enhanced performances for these two factors. (D.L.). 4 refs., 3 figs

  16. Diagnostic capability of retinal thickness measures in diabetic peripheral neuropathy

    Directory of Open Access Journals (Sweden)

    Sangeetha Srinivasan

    2017-10-01

    Conclusions: The GCC FLV can differentiate individuals with diabetic neuropathy from healthy controls, while the inferior RNFL thickness is able to differentiate those with greater degrees of neuropathy from those with mild or no neuropathy, both with an acceptable level of accuracy. Optical coherence tomography represents a non-invasive technology that aids in detection of retinal structural changes in patients with established diabetic neuropathy. Further refinement of the technique and the analytical approaches may be required to identify patients with minimal neuropathy.

  17. Measurement of the Area of Corneal Exposure Using Digital Image and Its Application During Assessment for Blepharoplasty.

    Science.gov (United States)

    Park, Kisoo; Guo, Ziyi; Park, Dae Hwan

    2018-02-01

    The normal morphological and functional values of orbits vary according to race, sex, and age. We measured the palpebral fissure using the marginal reflex distance (MRD 1 ), marginal limbal distance (MLD), and vertical height of the palpebral fissure (VHPF). Unfortunately, these measurements are all one-dimensional figures that measure the distance between two points; they have limitations when it comes to measuring the three-dimensional ocular surface. Therefore, this study used the area of corneal exposure (ACE), which shows a two-dimensional area, to measure changes between the sizes of eyes according to age. This study was conducted using preoperative photographs of Koreans in Daegu city, Korea, who underwent plastic surgery in our department except for eyelid surgery. We divided the subjects into eight groups, including ten males and ten females in each decade of age, from age 10 to over 80 years. A total of 160 people were recruited who were followed up for photograph analysis using Adobe Photoshop 7.0 software. In terms of the mean value, the ACEs were 73.3 ± 2% in male subjects and 77.1 ± 2% in female subjects, and values for female subjects were greater than those for male subjects (p Contents or the online Instructions to Authors www.springer.com/00266 .

  18. Short-term corneal changes with gas-permeable contact lens wear in keratoconus subjects: a comparison of two fitting approaches.

    Science.gov (United States)

    Romero-Jiménez, Miguel; Santodomingo-Rubido, Jacinto; Flores-Rodríguez, Patricia; González-Méijome, Jose-Manuel

    2015-01-01

    To evaluate changes in anterior corneal topography and higher-order aberrations (HOA) after 14-days of rigid gas-permeable (RGP) contact lens (CL) wear in keratoconus subjects comparing two different fitting approaches. Thirty-one keratoconus subjects (50 eyes) without previous history of CL wear were recruited for the study. Subjects were randomly fitted to either an apical-touch or three-point-touch fitting approach. The lens' back optic zone radius (BOZR) was 0.4mm and 0.1mm flatter than the first definite apical clearance lens, respectively. Differences between the baseline and post-CL wear for steepest, flattest and average corneal power (ACP) readings, central corneal astigmatism (CCA), maximum tangential curvature (KTag), anterior corneal surface asphericity, anterior corneal surface HOA and thinnest corneal thickness measured with Pentacam were compared. A statistically significant flattening was found over time on the flattest and steepest simulated keratometry and ACP in apical-touch group (all p<0.01). A statistically significant reduction in KTag was found in both groups after contact lens wear (all p<0.05). Significant reduction was found over time in CCA (p=0.001) and anterior corneal asphericity in both groups (p<0.001). Thickness at the thinnest corneal point increased significantly after CL wear (p<0.0001). Coma-like and total HOA root mean square (RMS) error were significantly reduced following CL wearing in both fitting approaches (all p<0.05). Short-term rigid gas-permeable CL wear flattens the anterior cornea, increases the thinnest corneal thickness and reduces anterior surface HOA in keratoconus subjects. Apical-touch was associated with greater corneal flattening in comparison to three-point-touch lens wear. Copyright © 2014 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

  19. Comparison of manual & automated analysis methods for corneal endothelial cell density measurements by specular microscopy.

    Science.gov (United States)

    Huang, Jianyan; Maram, Jyotsna; Tepelus, Tudor C; Modak, Cristina; Marion, Ken; Sadda, SriniVas R; Chopra, Vikas; Lee, Olivia L

    2017-08-07

    To determine the reliability of corneal endothelial cell density (ECD) obtained by automated specular microscopy versus that of validated manual methods and factors that predict such reliability. Sharp central images from 94 control and 106 glaucomatous eyes were captured with Konan specular microscope NSP-9900. All images were analyzed by trained graders using Konan CellChek Software, employing the fully- and semi-automated methods as well as Center Method. Images with low cell count (input cells number <100) and/or guttata were compared with the Center and Flex-Center Methods. ECDs were compared and absolute error was used to assess variation. The effect on ECD of age, cell count, cell size, and cell size variation was evaluated. No significant difference was observed between the Center and Flex-Center Methods in corneas with guttata (p=0.48) or low ECD (p=0.11). No difference (p=0.32) was observed in ECD of normal controls <40 yrs old between the fully-automated method and manual Center Method. However, in older controls and glaucomatous eyes, ECD was overestimated by the fully-automated method (p=0.034) and semi-automated method (p=0.025) as compared to manual method. Our findings show that automated analysis significantly overestimates ECD in the eyes with high polymegathism and/or large cell size, compared to the manual method. Therefore, we discourage reliance upon the fully-automated method alone to perform specular microscopy analysis, particularly if an accurate ECD value is imperative. Copyright © 2017. Published by Elsevier España, S.L.U.

  20. Transepithelial Riboflavin Absorption in an Ex Vivo Rabbit Corneal Model.

    Science.gov (United States)

    Gore, Daniel M; O'Brart, David; French, Paul; Dunsby, Chris; Allan, Bruce D

    2015-07-01

    To measure depth-specific riboflavin concentrations in corneal stroma using two-photon fluorescence microscopy and compare commercially available transepithelial corneal collagen cross-linking (CXL) protocols. Transepithelial CXL riboflavin preparations--MedioCross TE, Ribocross TE, Paracel plus VibeX Xtra, and iontophoresis with Ricrolin+--were applied to the corneal surface of fresh postmortem rabbit eyes in accordance with manufacturers' recommendations for clinical use. Riboflavin 0.1% (VibeX Rapid) was applied after corneal epithelial debridement as a positive control. After riboflavin application, eyes were snap frozen in liquid nitrogen. Corneal cross sections 35-μm thick were cut on a cryostat, mounted on a slide, and imaged by two-photon fluorescence microscopy. Mean (SD) concentrations were calculated from five globes tested for each protocol. Peak riboflavin concentration of 0.09% (± 0.01) was observed within the most superficial stroma (stromal depth 0-10 μm) in positive controls (epithelium-off). At the same depth, peak stromal riboflavin concentrations for MedioCross TE, Ricrolin+, Paracel/Xtra, and Ribocross TE were 0.054% (± 0.01), 0.031% (0.003), 0.021% (± 0.001), and 0.015% (± 0.004), respectively. At a depth of 300 μm (within the demarcation zone commonly seen after corneal cross-linking), the stromal concentration in epithelium-off positive controls was 0.075% (± 0.006), while at the same depth MedioCross TE and Ricrolin+ achieved 0.018% (± 0.006) and 0.016% (0.002), respectively. None of the remaining transepithelial protocols achieved concentrations above 0.005% at this same 300-μm depth. Overall, MedioCross TE was the best-performing transepithelial formulation. Corneal epithelium is a significant barrier to riboflavin absorption into the stroma. Existing commercial transepithelial CXL protocols achieve relatively low riboflavin concentrations in the anterior corneal stroma when compared to gold standard epithelium-off absorption

  1. Clinical usefulness of facial soft tissues thickness measurement using 3D computed tomographic images

    International Nuclear Information System (INIS)

    Jeong, Ho Gul; Kim, Kee Deog; Hu, Kyung Seok; Lee, Jae Bum; Park, Hyok; Han, Seung Ho; Choi, Seong Ho; Kim, Chong Kwan; Park, Chang Seo

    2006-01-01

    To evaluate clinical usefulness of facial soft tissue thickness measurement using 3D computed tomographic images. One cadaver that had sound facial soft tissues was chosen for the study. The cadaver was scanned with a Helical CT under following scanning protocols about slice thickness and table speed: 3 mm and 3 mm/sec, 5 mm and 5 mm/sec, 7 mm and 7 mm/sec. The acquired data were reconstructed 1.5, 2.5, 3.5 mm reconstruction interval respectively and the images were transferred to a personal computer. Using a program developed to measure facial soft tissue thickness in 3D image, the facial soft tissue thickness was measured. After the ten-time repeation of the measurement for ten times, repeated measure analysis of variance (ANOVA) was adopted to compare and analyze the measurements using the three scanning protocols. Comparison according to the areas was analysed by Mann-Whitney test. There were no statistically significant intraobserver differences in the measurements of the facial soft tissue thickness using the three scanning protocols (p>0.05). There were no statistically significant differences between measurements in the 3 mm slice thickness and those in the 5 mm, 7 mm slice thickness (p>0.05). There were statistical differences in the 14 of the total 30 measured points in the 5 mm slice thickness and 22 in the 7 mm slice thickness. The facial soft tissue thickness measurement using 3D images of 7 mm slice thickness is acceptable clinically, but those of 5 mm slice thickness is recommended for the more accurate measurement

  2. Comparison of 120- and 140-μm SMILE Cap Thickness Results in Eyes With Thick Corneas.

    Science.gov (United States)

    Liu, Manli; Zhou, Yugui; Wu, Xianghua; Ye, Tiantian; Liu, Quan

    2016-10-01

    To evaluate clinical outcomes after small incision lenticule extraction (SMILE) with different cap thicknesses in thick corneas. Forty patients with central corneal thickness of more than 560 μm were recruited in this prospective, randomized, masked, paired-eye study. Patients were randomized to receive SMILE with a 120-μm cap thickness in 1 eye and 140-μm cap thickness in the other. Uncorrected and corrected distance visual acuity (CDVA), contrast sensitivity (CS), higher-order aberrations (HOAs), and morphologic modifications of corneal architecture were measured during the 3-month follow-up period. Postoperative refractive outcomes, visual outcomes, CS, and the changes in HOAs were similar between both groups. The persistence of brightly reflective particles in the corneal interface layer was 1388.6 ± 219.5/mm in eyes with 120-μm cap thickness and 54.7 ± 8.6/mm in eyes with 140-μm cap thickness (P line at the interface layer almost disappeared in all eyes with 140-μm cap thickness, and it still persisted in 43% of the fellow eyes at 3 months postoperatively. The anterior surfaces of lenticules in the 140-μm cap thickness group exhibited more smoothness than in the 120-μm cap thickness group. There was a lower level corneal wound-healing response after SMILE with a 140-μm cap thickness than with a 120-μm cap thickness, although the thickness of cap creation did not affect visual outcomes by 3 months postoperatively.

  3. Research progress on the measurement of human lens thickness in vivo

    Directory of Open Access Journals (Sweden)

    Yu-Huan Yang

    2017-05-01

    Full Text Available The precise measurement in lens thickness in vivo, provides great application value for intraocular accommodation and ametropia development mechanism research. And it has great clinical significance for the diagnosis and treatment of glaucoma and cataract. Currently, many ultrasonic methods and optical methods are used in measuring lens thickness. The measurement principles, advantages, disadvantages and the accuracy of the instruments are summarized in this paper. Among these methods, Orbscan II, Pentacam, Lenstar and AS-OCT can be used to measure lens thickness instead of A-scan. More important is the fact that UL-OCT can dynamically monitor the change of the lens thickness with intraocular accommodation. Choosing an instrument with higher measuring accuracy to examine the lens thickness, can provide more accurate and convincing lens thickness data for clinical and scientific research.

  4. Macular volume and central foveal thickness measurements in ...

    African Journals Online (AJOL)

    The mean macula volume was 6.79 + 0.392 µm3. It was 6.861 , 0.297 in males, 6.496 , 0.520 in females and was statistically higher in males than females (P = 0.000). The mean central foveal thickness (MCFT) was 149.58±32.470 µm. It was 154.49 ± 34.652 µm in males and 133.33 ± 15.315 µm in females. MCFT was ...

  5. Nondestructive method to coat thickness measurements through X-ray fluorescence

    International Nuclear Information System (INIS)

    Sanchez, F.

    1986-01-01

    It's described a system that permits thickness measurement and composition of Sn-Pb alloys to simultaneous measurement of Au over Ni over any base, beyond convestionals measurements, including flash coats or touch. (C.M.) [pt

  6. Assessment of corneal biomechanical parameters in myopes and emmetropes using the Corvis ST.

    Science.gov (United States)

    Lee, Rachel; Chang, Robert T; Wong, Ian Y H; Lai, Jimmy S M; Lee, Jacky W Y; Singh, Kuldev

    2016-03-01

    Prior studies have demonstrated conflicting results regarding the relationship between corneal biomechanical properties and refractive error. Thus, the purpose of this study was to compare the corneal biomechanical parameters of myopes and emmetropes. Ninety-four subjects with varying degrees of myopia (aged 29 to 74 years, spherical equivalent [SE] -0.5 to -17.5 D) and 25 emmetropes (aged 19 to 75 years, SE: -0.5 to +0.5 D) presenting at the Queen Mary Hospital, Hong Kong were recruited sequentially for this prospective study. All patients were phakic with no history of coexisting ocular disease. The corneal biomechanical parameters of the right eye of each subject were analysed using the Corvis ST non-contact tonometer. Intraocular pressure (IOP) was measured using both the Corvis ST and the Topcon Non-Contact Tonometer CT-80. Refractive error was measured by non-cycloplegic subjective and objective refractometry. High myopes (SE greater than -6.00 D) demonstrated greater mean outward applanation velocities (p < 0.001) and peak distance measurements (p = 0.009) compared to both low to moderate myopes (SE -0.50 to -6.00 D) and emmetropes. Both outward applanation velocity and peak distance were moderately correlated with refractive error (p ≤ 0.001), strongly correlated with IOP and weakly correlated with central corneal thickness. There were no statistically significant differences in age, IOP or central corneal thickness among emmetropes, low to moderate myopes or high myopes. Within this study of Chinese subjects, high myopes demonstrate greater corneal mean outward applanation velocity on Corvis ST testing, than emmetropes. In particular, those with high myopia (SE greater than -6.00 D) show a distinct corneal biomechanical profile relative to those with either emmetropia or low to moderate myopia using the Corvis ST. © 2016 Optometry Australia.

  7. Cross section measurement and integral test for several activation reactions using T + d and thick-Li + d sources

    International Nuclear Information System (INIS)

    Dumais, J.R.; Tanaka, S.; Odano, N.; Iwasaki, S.; Sugiyama, K.

    1988-01-01

    Recent activities on the area of the cross section measurement for several activation reactions at Department of Nucl. Eng., Tohoku Univ. are described. The first subject is the cross section measurement for (n,2n) reaction on aluminum using the RTNS-II neutron source. Cross sections with rather small error band were obtained for the incident neutron energies from 14 to 14.7 MeV. The second one is the status of the program for the integral experiments on several reactions using the thick Li + d source at Tohoku Fast Neutron Lab. The experimental results showed the usefullness of the source as a tool for the cross section assessment. (author)

  8. Late onset corneal ectasia after LASIK surgery.

    Science.gov (United States)

    Said, Ashraf; Hamade, Issam H; Tabbara, Khalid F

    2011-07-01

    To report late onset corneal ectasia following myopic LASIK. A retrospective cohort case series. Nineteen patients with late onset corneal ectasia following LASIK procedure were examined at The Eye Center, Riyadh, Saudi Arabia. Patients underwent LASIK for myopia with spherical equivalent ranging from -1.4 to -13.75 diopters. Age and gender, history of systemic or local diseases, and time of onset of corneal ectasia were recorded. Eye examination and corneal topographical analyses were done before and after LASIK surgery. Nineteen patients (29 eyes) with late onset corneal ectasia were identified from 1998 to 2008 in 13 male and six female patients. The mean follow-up period was 108 ± 23 months (range 72-144 months). No patient had pre-operative identifiable risk factors for corneal ectasia and the mean time of onset was 57 ± 24 months (range 24-120 months after LASIK). The pre-operative values included mean central pachymetry 553 ± 25 μm, mean keratometry reading of 42.9 ± 1.5 diopters, average oblique cylinder of 1.4 ± 1.2 diopters, posterior surface elevation of 26 ± 2.1 diopters, corneal flap thickness of 160 μm, mean spherical equivalent of -5.6 ± 3.6 diopters, and calculated residual corneal stromal bed thickness was 288 ± 35 μm. Three (5 eyes) patients developed ectasia after pregnancy. Three (4 eyes) patients developed corneal ectasia following severe adenoviral keratoconjunctivitis and had positive PCR for adenovirus type 8. Corneal ectasia may develop many years after LASIK surgery and symptoms could go undetected for some time. Pregnancy and adenoviral keratoconjunctivitis occurred post-operatively in six patients.

  9. Evaluation of intracameral injection of ranibizumab and bevacizumab on the corneal endothelium by scanning electron microscopy.

    Science.gov (United States)

    Ari, Seyhmus; Nergiz, Yusuf; Aksit, Ihsan; Sahin, Alparslan; Cingu, Kursat; Caca, Ihsan

    2015-03-01

    To evaluate the effects of intracameral injection of ranibizumab and bevacizumab on the corneal endothelium by scanning electron microscopy (SEM). Twenty-eight female rabbits were randomly divided into four equal groups. Rabbits in groups 1 and 2 underwent intracameral injection of 1 mg/0.1 mL and 0.5 mg/0.05 mL ranibizumab, respectively; group 3 was injected with 1.25 mg/0.05 mL bevacizumab. All three groups were injected with a balanced salt solution (BSS) into the anterior chamber of the left (fellow) eye. None of the rabbits in group 4 underwent an injection. Corneal thickness and intraocular pressure were measured before the injections, on the first day, and in the first month after injection. The rabbits were sacrificed and corneal tissues were excised in the first month after injection. Specular microscopy was used for the corneal endothelial cell count. Endothelial cell density was assessed and comparisons drawn between the groups and the control. Micrographs were recorded for SEM examination. The structure of the corneal endothelial cells, the junctional area of the cell membrane, the distribution of microvillus, and the cell morphology of the eyes that underwent intracameral injection of vascular endothelial growth factor (VEGF), BSS, and the control group were compared. Corneal thickness and intraocular pressure were not significantly different between the groups that underwent anti-VEGF or BSS injection and the control group on the first day and in the first month of injection. The corneal endothelial cell count was significantly diminished in all three groups; predominantly in group 1 and 2 (P<0.05). The SEM examination revealed normal corneal endothelial histology in group 3 and the control group. Eyes in group 1 exhibited indistinctness of corneal endothelial cell borders, microvillus loss in the luminal surface, excessive blebbing, and disintegration of intercellular junctions. In group 2, the cell structure of the corneal endothelium

  10. The research of device for measuring film thickness of intelligent coating machine

    Directory of Open Access Journals (Sweden)

    Wang Wanjun

    2015-01-01

    Full Text Available Ion beam sputtering machine uses computer to real time monitor the change of film thickness in the preparation process of soft X ray multilayer element fabrication. It solves the problems of uneven film thickness and too thick film thickness and so on, which exist in the original preparation process. The high-precision quartz crystal converts film thickness measurement into frequency measurement. The equal precision frequency meter based on FPGA measures the frequency. It can reduce the signal delay and interference signal of discrete components, accordingly improving the accuracy of measurement. Then it sents the count value to the host computer through the single chip microcomputer serial port. It calculates and displays the value by the GUI of LabVIEW. The experimental results show that, the relative measurement error can be decreased to 1/10, i.e., the measurement accuracy can be improved by more than ten times.

  11. Effects of epidermal growth factor in artificial tear on vitamin C levels of corneal wounded eye tissues.

    Science.gov (United States)

    Gönül, B; Kaplan, B; Bilgihan, K; Budak, M T

    2001-04-01

    To investigate the effect of artificial tear (AT) solution and epidermal growth factor (EGF) treatment on the cornea and aqueous humour ascorbic acid (AA) levels of full-thickness corneal wounded eyes. The effect of EGF on the AA levels of aqueous humour and corneal wound tissue was determined in full-thickness corneal wounded rabbit eyes on the seventh post-operative day. There were three groups: untreated controls, AT-treated controls and an EGF+AT-treated experimental group (n = 6 in each group). Corneal wounded eyes were topically treated with 5 microl AT or 5 microl EGF in AT (1 mg/l EGF in AT prepaaration which contained 3.0% carbopol 940) twice daily for 6 days after operation. The wound strengths were also measured on the seventh post-operative day as a measure of wound healing. Statistical analysis was carried out using the Mann-Whitney U-test by Statview program. The wound strengths of corneas, and AA levels of wound tissues and aqueous humour, increased significantly following AT and EGF treatment (p < 0.05). In the corneal wounded eye, aqueous humour serves as a source of vitamin C and there may be a relation between EGF treatment in AT and AA levels of corneal wounded eye tissues.

  12. Relationship between the thickness of the renal cortex and age: study with CT measurement

    International Nuclear Information System (INIS)

    Xu Yufeng; Tang Guangjian

    2004-01-01

    Objective: To study the relationship between the renal cortical thickness and age, and to establish the range of the normal renal cortex thickness by using CT measurement in different age groups so as to obtain a best age-related and practicable method for clinical measurement. Methods: (1) the accuracy of measuring renal cortical thickness by CT was evaluated: 18 kidney resected due to renal neoplasm were studied and the cortical thickness of the normal part of these specimens was assessed. The difference between the renal cortical thickness of specimens and preoperative measurements of renal cortex of the same patient by contrast enhanced CT was analyzed statistically. (2) 120 patients without history of renal disease or long term usage of potentially renal toxic drugs or history of hypertension were examined by CT with indication (s) other than renal disease. All the patients were divided into 20-40, 41-60, and 61-80 year-old groups. The renal cortical and parenchymal thickness and renal size were measured in three CT sections. The difference of the measurements among the three groups and their relationship to age was analyzed statistically. Results: There was no significant difference between the renal cortical thickness measured by enhanced spiral CT and measured in renal specimens (t=0.80, P=0.43). The renal cortical thickness in three groups was 0.73 cm, 0.65 cm, and 0.53 cm, respectively, and the differences among the three groups were significant (F=93.430, P 0.05). Conclusion: The measurement of the renal cortical thickness with enhanced spiral CT was reliable and was a sensitive method in investigating the morphologic changes of the kidney. The renal cortical thickness of normal kidney diminishes with age, but the change of the ratio of thickness of renal cortex to renal parenchyma with age was not significant

  13. Quantitative computed tomography measures of emphysema and airway wall thickness are related to respiratory symptoms

    DEFF Research Database (Denmark)

    Grydeland, Thomas B; Dirksen, Asger; Coxson, Harvey O

    2010-01-01

    There is limited knowledge about the relationship between respiratory symptoms and quantitative high-resolution computed tomography measures of emphysema and airway wall thickness.......There is limited knowledge about the relationship between respiratory symptoms and quantitative high-resolution computed tomography measures of emphysema and airway wall thickness....

  14. Investigation of the Section Thickness Measurement in Tomosynthesis by Thin Metal Plate Edge Method.

    Science.gov (United States)

    Ikeno, Kaoru; Akita, Tsunemichi; Hanai, Kozo; Muramatsu, Yoshihisa

    When performing tomosynthesis, the section thickness needs to be set depending on a radiographic part and its diagnostic purpose. However, the section thickness in tomosynthesis has not been clearly defined and its measurement method has not been established yet. In this study, we devised the alternative measurement method to diagnose the section thickness using an edge of thin metal plate, and compared with the simulation results, the wire and bead method reported in the previous papers. The tomographic image of the thin metal plate positioned on the table top inclining 30 degrees, which showed the edge spread function (ESF) of each tomographic height, was taken, and then the line spread function (LSF) was obtained by differentiating the ESF image. For the next, a profile curve was plotted by maximum values of LSF of each tomographic height, and a section thickness was calculated using the full width at half maximum (FWHM) of the profile curve. The edge method derived the section thickness close to the simulation results than the other methods. Further, the section thickness depends on the thickness of the metal plate and not the material. The thickness of the metal plate suitable for the evaluation of section thickness is 0.3 mm that is equivalent to pixel size of the flat panel detector (FPD). We conducted quantitative verification to establish the measurement method of the section thickness. The edge method is a useful technique as well as the wire and bead method for grasping basic characteristics of an imaging system.

  15. Assessment of Nuclear Fuels using Radiographic Thickness Measurement Method

    Energy Technology Data Exchange (ETDEWEB)

    Muhammad Abir; Fahima Islam; Hyoung Koo Lee; Daniel Wachs

    2014-11-01

    The Convert branch of the National Nuclear Security Administration (NNSA) Global Threat Reduction Initiative (GTRI) focuses on the development of high uranium density fuels for research and test reactors for nonproliferation. This fuel is aimed to convert low density high enriched uranium (HEU) based fuel to high density low enriched uranium (LEU) based fuel for high performance research reactors (HPRR). There are five U.S. reactors that fall under the HPRR category, including: the Massachusetts Institute of Technology Reactor (MITR), the National Bureau of Standards Reactor (NBSR), the Missouri University Research Reactor (UMRR), the Advanced Test Reactor (ATR), and the High Flux Isotope Reactor (HFIR). U-Mo alloy fuel phase in the form of either monolithic or dispersion foil type fuels, such as ATR Full-size In center flux trap Position (AFIP) and Reduced Enrichment for Research and Test Reactor (RERTR), are being designed for this purpose. The fabrication process1 of RERTR is susceptible to introducing a variety of fuel defects. A dependable quality control method is required during fabrication of RERTR miniplates to maintain the allowable design tolerances, therefore evaluating and analytically verifying the fabricated miniplates for maintaining quality standards as well as safety. The purpose of this work is to analyze the thickness of the fabricated RERTR-12 miniplates using non-destructive technique to meet the fuel plate specification for RERTR fuel to be used in the ATR.

  16. Corneal laceration caused by river crab

    Directory of Open Access Journals (Sweden)

    Vinuthinee N

    2015-01-01

    Full Text Available Naidu Vinuthinee,1,2 Anuar Azreen-Redzal,1 Jaafar Juanarita,1 Embong Zunaina2 1Department of Ophthalmology, Hospital Sultanah Bahiyah, Alor Setar, 2Department of Ophthalmology, School of Medical Sciences, Universiti Sains Malaysia, Kubang Kerian, Malaysia Abstract: A 5-year-old boy presented with right eye pain associated with tearing and photophobia of 1-day duration. He gave a history of playing with a river crab when suddenly the crab clamped his fingers. He attempted to fling the crab off, but the crab flew and hit his right eye. Ocular examination revealed a right eye corneal ulcer with clumps of fibrin located beneath the corneal ulcer and 1.6 mm level of hypopyon. At presentation, the Seidel test was negative, with a deep anterior chamber. Culture from the corneal scrapping specimen grew Citrobacter diversus and Proteus vulgaris, and the boy was treated with topical gentamicin and ceftazidime eyedrops. Fibrin clumps beneath the corneal ulcer subsequently dislodged, and revealed a full-thickness corneal laceration wound with a positive Seidel test and shallow anterior chamber. The patient underwent emergency corneal toileting and suturing. Postoperatively, he was treated with oral ciprofloxacin 250 mg 12-hourly for 1 week, topical gentamicin, ceftazidime, and dexamethasone eyedrops for 4 weeks. Right eye vision improved to 6/9 and 6/6 with pinhole at the 2-week follow-up following corneal suture removal. Keywords: corneal ulcer, pediatric trauma, ocular injury

  17. Manual versus automatic bladder wall thickness measurements: a method comparison study

    NARCIS (Netherlands)

    Oelke, M.; Mamoulakis, C.; Ubbink, D.T.; de la Rosette, J.J.; Wijkstra, H.

    2009-01-01

    Purpose To compare repeatability and agreement of conventional ultrasound bladder wall thickness (BWT) measurements with automatically obtained BWT measurements by the BVM 6500 device. Methods Adult patients with lower urinary tract symptoms, urinary incontinence, or postvoid residual urine were

  18. Triceps skin fold thickness as a measure of body fat in Nigerian

    African Journals Online (AJOL)

    owner

    2012-11-26

    Nov 26, 2012 ... and body fat distribution.2,3 Skin fold thickness measure- ments are a well ... different recognized areas for the measurement of SFT, ..... 'western children.' These .... Asia Pacific J Clin ... sity in children and young people:.

  19. Comparison and interchangeability of macular thickness measured with Cirrus OCT and Stratus OCT in myopic eyes

    Directory of Open Access Journals (Sweden)

    Geng Wang

    2015-12-01

    Full Text Available AIM: To investigate the difference of macular thickness measurements between stratus optical coherence tomography (OCT and Cirrus OCT (Carl Zeiss Meditec, Dublin, CA, USA in the same myopic patient and to develop a conversion equation to interchange macular thickness obtained with these two OCT devices. METHODS: Eighty-nine healthy Chinese adults with spherical equivalent (SE ranging from -1.13 D to -9.63 D were recruited. The macular thickness was measured by Cirrus OCT and Stratus OCT. The correlation between macular thickness and axial length and the agreement between two OCT measurements were evaluated. A formula was generated to interchange macular thickness obtained with two OCT devices. RESULTS: Average macular thickness measured with Stratus OCT (r=-0.280, P=0.008 and Cirrus OCT (r=-0.224, P=0.034 were found to be negatively correlated with axial length. No statistically significant correlation was found between axial length and central subfield macular thickness (CMT measured with Stratus OCT (r=0.191, P=0.073 and Cirrus OCT (r=0.169, P=0.113. The mean CMT measured with Cirrus OCT was 53.63±7.94 μm thicker than with Stratus OCT. The formula CMTCirrus OCT=78.328+0.874×CMTStratus OCT was generated to interchange macular thickness obtained with two OCT devices. CONCLUSION: Macular thickness measured with Cirrus OCT were thicker than with Stratus OCT in myopic eyes. A formula can be used to interchange macular thickness measured with two OCT devices in myopic eyes. Studies with different OCT devices and larger samples are warranted to enable the comparison of macular values measured with different OCT devices.

  20. Measurement of the bremsstrahlung spectra generated from thick ...

    Indian Academy of Sciences (India)

    with those predicted by Monte-Carlo (MC) calculations using PENELOPE code. A close ... done on bremsstrahlung cross-section measurements and many theories have been given for ..... This probability is expected to be maximum for elastic.

  1. Influence of eye biometrics and corneal micro-structure on noncontact tonometry.

    Directory of Open Access Journals (Sweden)

    Danilo A Jesus

    Full Text Available Tonometry is widely used as the main screening tool supporting glaucoma diagnosis. Still, its accuracy could be improved if full knowledge about the variation of the corneal biomechanical properties was available. In this study, Optical Coherence Tomography (OCT speckle statistics are used to infer the organisation of the corneal micro-structure and hence, to analyse its influence on intraocular pressure (IOP measurements.Fifty-six subjects were recruited for this prospective study. Macro and micro-structural corneal parameters as well as subject age were considered. Macro-structural analysis included the parameters that are associated with the ocular anatomy, such as central corneal thickness (CCT, corneal radius, axial length, anterior chamber depth and white-to-white corneal diameter. Micro-structural parameters which included OCT speckle statistics were related to the internal organisation of the corneal tissue and its physiological changes during lifetime. The corneal speckle obtained from OCT was modelled with the Generalised Gamma (GG distribution that is characterised with a scale parameter and two shape parameters.In macro-structure analysis, only CCT showed a statistically significant correlation with IOP (R2 = 0.25, p<0.001. The scale parameter and the ratio of the shape parameters of GG distribution showed statistically significant correlation with IOP (R2 = 0.19, p<0.001 and R2 = 0.17, p<0.001, respectively. For the studied group, a weak, although significant correlation was found between age and IOP (R2 = 0.053, p = 0.04. Forward stepwise regression showed that CCT and the scale parameter of the Generalised Gamma distribution can be combined in a regression model (R2 = 0.39, p<0.001 to study the role of the corneal structure on IOP.We show, for the first time, that corneal micro-structure influences the IOP measurements obtained from noncontact tonometry. OCT speckle statistics can be employed to learn about the corneal micro

  2. Influence of eye biometrics and corneal micro-structure on noncontact tonometry.

    Science.gov (United States)

    Jesus, Danilo A; Majewska, Małgorzata; Krzyżanowska-Berkowska, Patrycja; Iskander, D Robert

    2017-01-01

    Tonometry is widely used as the main screening tool supporting glaucoma diagnosis. Still, its accuracy could be improved if full knowledge about the variation of the corneal biomechanical properties was available. In this study, Optical Coherence Tomography (OCT) speckle statistics are used to infer the organisation of the corneal micro-structure and hence, to analyse its influence on intraocular pressure (IOP) measurements. Fifty-six subjects were recruited for this prospective study. Macro and micro-structural corneal parameters as well as subject age were considered. Macro-structural analysis included the parameters that are associated with the ocular anatomy, such as central corneal thickness (CCT), corneal radius, axial length, anterior chamber depth and white-to-white corneal diameter. Micro-structural parameters which included OCT speckle statistics were related to the internal organisation of the corneal tissue and its physiological changes during lifetime. The corneal speckle obtained from OCT was modelled with the Generalised Gamma (GG) distribution that is characterised with a scale parameter and two shape parameters. In macro-structure analysis, only CCT showed a statistically significant correlation with IOP (R2 = 0.25, p<0.001). The scale parameter and the ratio of the shape parameters of GG distribution showed statistically significant correlation with IOP (R2 = 0.19, p<0.001 and R2 = 0.17, p<0.001, respectively). For the studied group, a weak, although significant correlation was found between age and IOP (R2 = 0.053, p = 0.04). Forward stepwise regression showed that CCT and the scale parameter of the Generalised Gamma distribution can be combined in a regression model (R2 = 0.39, p<0.001) to study the role of the corneal structure on IOP. We show, for the first time, that corneal micro-structure influences the IOP measurements obtained from noncontact tonometry. OCT speckle statistics can be employed to learn about the corneal micro-structure and

  3. A new attempt of measurement film thickness by x-ray diffractometry

    International Nuclear Information System (INIS)

    Kosaka, Masao; Kobayashi, Hideo

    1987-01-01

    In order to make film thickness measurements independent from the property or the structure of the film materials or the substrate, it is needed to adopt instead of directly utilizing the X-ray diffraction intensity, or attenuation information obtained from the substrate or film material, other new methods for measurement. Among the information obtained by X-ray diffraction, if intensity is excluded, others are F.W.H.M. and diffraction angle, only. If it is possible to investigate the film thickness dependency of the diffraction angle, it should be possible to measure the film thickness by diffraction angle. However, since diffraction angle has no film thickness dependency, it cannot be used directly for measurement. However, if we consider the principle of the X-ray diffractometer method, although it may be very slight, the substrate will be eccentric from the revolving center of the goniometer on account of the thickness of the film. If eccentricity occurs, this will cause changes in the diffraction angle. If we set the radius of the goniometer as R, diffraction angle θ, and the eccentricity from the revolving center of the specimen surface X, the deflection angle Δ2θ of 2θ may be expressed by Δ2θ = -2X · COSθ/R Thus, if X is caused by the film thickness, and by measuring the Δ2θ, it will be possible to measure the film thickness. As a result of the experiment, it was found that X-ray diffraction method can be used for the measurement of the film thickness of a few microns or above by utilizing the eccentricity caused by the film thickness. Especially it has the advantage of being able to measure thick films that X-rays will not penetrate, without being influenced by the chemical structure of the film or the substrates. (author)

  4. Quantitative materials analysis of micro devices using absorption-based thickness measurements

    International Nuclear Information System (INIS)

    Sim, L M; Wog, B S; Spowage, A C

    2006-01-01

    Preliminary work in designing an X-ray inspection machine with the capability of providing quantitative thickness analysis based on absorption measurements has been demonstrated. This study attempts to use the gray levels data to investigate the nature and thickness of occluded features and materials within devices. The investigation focused on metallic materials essential to semiconductor and MEMS technologies such as tin, aluminium, copper, silver, iron and zinc. The materials were arranged to simulate different feature thicknesses and sample geometries. The X-ray parameters were varied in-order to modify the X-ray energy spectrum with the aim of optimising the measurement conditions for each sample. The capability of the method to resolve differences in thicknesses was found to be highly dependent on the material. The thickness resolution with aluminium was the poorest due to its low radiographic density. The thickness resolutions achievable for silver and tin were significantly better and of the order of 0.015 mm and 0.025 mm respectively. From the linear relationship between the X-ray attenuation and sample thickness established, the energy dependent linear attenuation coefficient for each material was determined for a series of specific energy spectra. A decrease in the linear attenuation coefficient was observed as the applied voltage and thickness of the material increased. The results provide a platform for the development of a novel absorption-based thickness measurement system that can be optimised for a range of industrial applications

  5. High-throughput measurement of polymer film thickness using optical dyes

    Science.gov (United States)

    Grunlan, Jaime C.; Mehrabi, Ali R.; Ly, Tien

    2005-01-01

    Optical dyes were added to polymer solutions in an effort to create a technique for high-throughput screening of dry polymer film thickness. Arrays of polystyrene films, cast from a toluene solution, containing methyl red or solvent green were used to demonstrate the feasibility of this technique. Measurements of the peak visible absorbance of each film were converted to thickness using the Beer-Lambert relationship. These absorbance-based thickness calculations agreed within 10% of thickness measured using a micrometer for polystyrene films that were 10-50 µm. At these thicknesses it is believed that the absorbance values are actually more accurate. At least for this solvent-based system, thickness was shown to be accurately measured in a high-throughput manner that could potentially be applied to other equivalent systems. Similar water-based films made with poly(sodium 4-styrenesulfonate) dyed with malachite green oxalate or congo red did not show the same level of agreement with the micrometer measurements. Extensive phase separation between polymer and dye resulted in inflated absorbance values and calculated thickness that was often more than 25% greater than that measured with the micrometer. Only at thicknesses below 15 µm could reasonable accuracy be achieved for the water-based films.

  6. Corneal endothelial cell loss and corneal biomechanical characteristics after two-step sequential or combined phaco-vitrectomy surgery for idiopathic epiretinal membrane

    DEFF Research Database (Denmark)

    Hamoudi, Hassan; Christensen, Ulrik Correll; La Cour, Morten

    2017-01-01

    with non-contact specular microscopy. Pachymetry [central cornea thickness (CCT)], keratometry and cornea volume (CV) were measured with Pentacam Scheimpflug camera. Primary outcome was change in CED after 12 months; secondary outcomes were changes in CCT and CV after 12 months. RESULTS: Sixty-two eyes......PURPOSE: To assess the impact of sequential and combined surgery [cataract surgery and 23-gauge pars plana vitrectomy (PPV) with peeling] on corneal endothelium cell density (CED) and corneal biomechanical characteristics. METHODS: Phakic eyes with epiretinal membrane (ERM) were prospectively...... allocated to (i) cataract surgery and subsequent PPV (CAT group), (ii) PPV and subsequent cataract surgery (VIT group) or (iii) phacovitrectomy (COMBI group). Eyes were examined at baseline, 1 month after each surgery, and at 3 and 12 months follow-up. Corneal endothelium cell density (CED) was assessed...

  7. Analysis of low-energy and high-frequency femtosecond laser for the construction of deep anterior donor corneal lamellae

    Directory of Open Access Journals (Sweden)

    Gustavo Victor

    2014-04-01

    Full Text Available Purpose: To evaluate the efficacy and reliability of a low-energy femtosecond laser with a high repetition rate for construction of deep anterior donor corneal lamellae. Methods: This was a prospective laboratory investigation. Twenty-five human corneal buttons were femtosecond laser cut to create thick anterior lamellae (diameter, 10mm; thickness, 500µm. The laser cuts were made using an LDV® femtosecond laser in a Ziemer® anterior chamber. To obtain a better edge, the lamellae were trephined with an 8mm trephine (Katena®. The central corneal thickness and the anterior lamellae were measured using a Mitutoyo® thickness gauge with an accuracy of 0.001mm. Results: The central thickness of the 25 corneas ranged from 500 to 705µm (mean, 584 ± 51µm. The thickness of the anterior lamellae ranged from 420 to 480µm (mean, 455 ± 12.7µm. The anterior lamellae diameters were 7.90 ± 0.1mm, and all laser cuts were round. The lamellar interfaces appeared regular by surgical microscopy. There were no cases of inter-lamellar adhesion. Conclusion: The LDV® femtosecond laser appears to be a safe and reliable instrument for cutting deep anterior lamellae from donor corneoscleral buttons. Minimal variation in donor lamellar depth with the laser will be useful for creating donor corneal tissue for deeper anterior lamellar keratoplasty or endothelial keratoplasty surgery or both from a single donor cornea.

  8. CD147 required for corneal endothelial lactate transport.

    Science.gov (United States)

    Li, Shimin; Nguyen, Tracy T; Bonanno, Joseph A

    2014-06-26

    CD147/basigin is a chaperone for lactate:H(+) cotransporters (monocarboxylate transporters) MCT1 and MCT4. We tested the hypothesis that MCT1 and -4 in corneal endothelium contribute to lactate efflux from stroma to anterior chamber and that silencing CD147 expression would cause corneal edema. CD147 was silenced via small interfering ribonucleic acid (siRNA) transfection of rabbit corneas ex vivo and anterior chamber lenti-small hairpin RNA (shRNA) pseudovirus in vivo. CD147 and MCT expression was examined by Western blot, RT-PCR, and immunofluorescence. Functional effects were examined by measuring lactate-induced cell acidification, corneal lactate efflux, [lactate], central cornea thickness (CCT), and Azopt (a carbonic anhydrase inhibitor) sensitivity. In ex vivo corneas, 100 nM CD147 siRNA reduced CD147, MCT1, and MCT4 expression by 85%, 79%, and 73%, respectively, while MCT2 expression was unaffected. CD147 siRNA decreased lactate efflux from 3.9 ± 0.81 to 1.5 ± 0.37 nmol/min, increased corneal [lactate] from 19.28 ± 7.15 to 56.73 ± 8.97 nmol/mg, acidified endothelial cells (pHi = 6.83 ± 0.07 vs. 7.19 ± 0.09 in control), and slowed basolateral lactate-induced acidification from 0.0034 ± 0.0005 to 0.0012 ± 0.0005 pH/s, whereas apical acidification was unchanged. In vivo, CD147 shRNA increased CCT by 28.1 ± 0.9 μm at 28 days; Azopt increased CCT to 24.4 ± 3.12 vs. 12.0 ± 0.48 μm in control, and corneal [lactate] was 47.63 ± 6.29 nmol/mg in shCD147 corneas and 17.82 ± 4.93 nmol/mg in paired controls. CD147 is required for the expression of MCT1 and MCT4 in the corneal endothelium. Silencing CD147 slows lactate efflux, resulting in stromal lactate accumulation and corneal edema, consistent with lactate efflux as a significant component of the corneal endothelial pump. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

  9. A method to measure the mean thickness and non-uniformity of non-uniform thin film by alpha-ray thickness gauge

    International Nuclear Information System (INIS)

    Miyahara, Hiroshi; Yoshida, Makoto; Watanabe, Tamaki

    1977-01-01

    The α-ray thickness gauge is used to measure non-destructively the thicknesses of thin films, and up to the present day, a thin film with uniform thickness is only taken up as the object of α-ray thickness gauge. When the thickness is determined from the displacement between the absorption curves in the presence and absence of thin film, the absorption curve must be displaced in parallel. When many uniform particles were dispersed as sample, the shape of the absorption curve was calculated as the sum of many absorption curves corresponding to the thin films with different thicknesses. By the comparison of the calculated and measured absorption curves, the number of particles, or the mean superficial density can be determined. This means the extension of thickness measurement from uniform to non-uniform films. Furthermore, these particle models being applied to non-uniform thin film, the possibility of measuring the mean thickness and non-uniformity was discussed. As the result, if the maximum difference of the thickness was more than 0.2 mg/cm 2 , the nonuniformity was considered to distinguish by the usual equipment. In this paper, an α-ray thickness gauge using the absorption curve method was treated, but one can apply this easily to an α-ray thickness gauge using α-ray energy spectra before and after the penetration of thin film. (auth.)

  10. Thermal and infrared-diode laser effects on indocyanine-green-treated corneal collagen

    Science.gov (United States)

    Timberlake, George T.; Patmore, Ann; Shallal, Assaad; McHugh, Dominic; Marshall, John

    1993-07-01

    It has been suggested that laser welds of collagenous tissues form by interdigitation and chemical bonding of thermally 'unraveled' collagen fibrils. We investigated this proposal by attempting to weld highly collagenous, avascular corneal tissue with an infrared (IR) diode laser as follows. First, the temperature at which corneal collagen shrinks and collagen fibrils 'split' into subfibrillary components was determined. Second, since use of a near-IR laser wavelength necessitated addition of an absorbing dye (indocyanine green (ICG) to the cornea, we measured absorption spectra of ICG-treated tissue to ensure that peak ICG absorbance did not change markedly when ICG was present in the cornea. Third, using gel electrophoresis of thermally altered corneal collagen, we searched for covalently crosslinked compounds predicted by the proposed welding mechanism. Finally, we attempted to weld partial thickness corneal incisions infused with ICG. Principal experimental findings were as follows: (1) Human corneal (type I) collagen splits into subfibrillary components at approximately 63 degree(s)C, the same temperature that produces collagen shrinkage. (2) Peak ICG absorption does not change significantly in corneal stroma or with laser heating. (3) No evidence was found for the formation of novel compounds or the loss of proteins as a result of tissue heating. All tissue treated with ICG, however, exhibited a novel 244 kD protein band indicating chemical activity between collagen and corneal stromal components. (4) Laser welding corneal incisions was unsuccessful possibly due to shrinkage of the sides of the incision, lack of incision compression during heating, or a less than optimal combination of ICG concentration and radiant exposure. In summary, these experiments demonstrate the biochemical and morphological complexity of ICG-enhanced IR laser-tissue welding and the need for further investigation of laser welding mechanisms.

  11. Corneal Deformation Response and Ocular Geometry: A Non-invasive Diagnostic Strategy in Marfan Syndrome

    Science.gov (United States)

    Beene, Lauren C.; Traboulsi, Elias I.; Seven, Ibrahim; Ford, Matthew R.; Roy, Abhijit Sinha; Butler, Robert S.; Dupps, William J.

    2015-01-01

    Purpose To evaluate corneal air-puff deformation responses and ocular geometry as predictors of Marfan syndrome. Design Prospective observational clinical study Methods Sixteen investigator-derived, 4 standard Ocular Response Analyzer (ORA), and geometric variables from corneal tomography and optical biometry using Oculus Pentacam and IOL Master were assessed for discriminative value in Marfan syndrome, measuring right eyes of 24 control and 13 Marfan syndrome subjects. Area under the receiver operating characteristic (AUROC) curve was assessed in univariate and multivariate analyses Results Six investigator-derived ORA variables successfully discriminated Marfan syndrome. The best lone disease predictor was Concavity Min (Marfan syndrome 47.5 ± 20, control 69 ± 14, p = 0.003; AUROC = 0.80). Corneal hysteresis and corneal resistance factor were decreased (Marfan syndrome CH 9.45 ± 1.62, control CH 11.24 ± 1.21, p = 0.01; Marfan syndrome CRF 9.77 ± 1.65, control CRF 11.03 ± 1.72, p = 0.01) and corneas were flatter in Marfan syndrome (Marfan syndrome Kmean 41.25 ± 2.09 D, control Kmean 42.70 ± 1.81 D, p = 0.046). No significant differences were observed in central corneal thickness, axial eye length, or intraocular pressure. A multivariate regression model incorporating corneal curvature and hysteresis loop area (HLA) provided the best predictive value for Marfan syndrome (AUROC = 0.85). Conclusions This study describes novel biodynamic features of corneal deformation responses in Marfan syndrome, including increased deformation, decreased bending resistance, and decreased energy dissipation capacity. A predictive model incorporating HLA and corneal curvature shows greatest potential for non-invasive clinical diagnosis of Marfan syndrome. PMID:26432567

  12. Corneal Deformation Response and Ocular Geometry: A Noninvasive Diagnostic Strategy in Marfan Syndrome.

    Science.gov (United States)

    Beene, Lauren C; Traboulsi, Elias I; Seven, Ibrahim; Ford, Matthew R; Sinha Roy, Abhijit; Butler, Robert S; Dupps, William J

    2016-01-01

    To evaluate corneal air-puff deformation responses and ocular geometry as predictors of Marfan syndrome. Prospective observational clinical study. Sixteen investigator-derived, 4 standard Ocular Response Analyzer (ORA), and geometric variables from corneal tomography and optical biometry using Oculus Pentacam and IOL Master were assessed for discriminative value in Marfan syndrome, measuring right eyes of 24 control and 13 Marfan syndrome subjects. Area under the receiver operating characteristic (AUROC) curve was assessed in univariate and multivariate analyses. Six investigator-derived ORA variables successfully discriminated Marfan syndrome. The best lone disease predictor was Concavity Min (Marfan syndrome 47.5 ± 20, control 69 ± 14, P = .003; AUROC = 0.80). Corneal hysteresis (CH) and corneal resistance factor (CRF) were decreased (Marfan syndrome CH 9.45 ± 1.62, control CH 11.24 ± 1.21, P = .01; Marfan syndrome CRF 9.77 ± 1.65, control CRF 11.03 ± 1.72, P = .01) and corneas were flatter in Marfan syndrome (Marfan syndrome Kmean 41.25 ± 2.09 diopter, control Kmean 42.70 ± 1.81 diopter, P = .046). No significant differences were observed in central corneal thickness, axial eye length, or intraocular pressure. A multivariate regression model incorporating corneal curvature and hysteresis loop area (HLA) provided the best predictive value for Marfan syndrome (AUROC = 0.85). This study describes novel biodynamic features of corneal deformation responses in Marfan syndrome, including increased deformation, decreased bending resistance, and decreased energy dissipation capacity. A predictive model incorporating HLA and corneal curvature shows greatest potential for noninvasive clinical diagnosis of Marfan syndrome. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. Thickness measurement for the different metals by using Cs-137 gamma source with gamma transmission technique

    International Nuclear Information System (INIS)

    Bueyuek, B.; Tugrul, B.

    2009-01-01

    The purpose of this study is an experimental analysis of thickness measurement for various metals with the gamma transmission technique using Cs-137 as the radioisotope source. Lead, steel, brass, and aluminum, which are frequently used metals in industry, were chosen for the experiments. As the radioisotope source Cs-137 was preferred for the study since it has long half-life, it is mono energetic, and it penetrates the metals that were studied. Experiments were observed in the constant experimental geometry. Calibration curves for the four metal samples were plotted using the obtained results. To test the plotted calibration curves, counts for determining thickness measurement were collected for each sample and the obtained relative count values were used in conjunction with the plotted calibration curves for each sample to determine its thickness. The thicknesses of the samples have been measured with a micrometer and the results were comparatively analyzed with the measurement results obtained by the gamma transmission technique. The results of the analyses revealed that the thickness measurement values obtained with the gamma transmission technique and the thickness measurement values obtained with the conventional technique significantly converge to each other and the difference between the two values is at an acceptable level. Therefore the reliability of thickness measurements with the gamma transmission technique and the resulting calibration curves have been demonstrated.

  14. Revisited the mathematical derivation wall thickness measurement of pipe for radiography

    Energy Technology Data Exchange (ETDEWEB)

    Hamzah, A.R.; Amir, S.M.M. [Non Destructive Testing(NDT) Group, Industrial Technology Div., Malaysian Nuclear Agency, Selangor (Malaysia)

    2007-07-01

    Wall thickness measurement of pipe is very important of the structural integrity of the industrial plant. However, the radiography method has an advantage because the ability of penetrating the insulated pipe. This will have economic benefit for industry. Moreover, the era of digital radiography has more advantages because the speed of radiographic work, less exposure time and no chemical used for film development. Either the conventional radiography or digital radiology, the wall thickness measurement is using the tangential radiography technique (TRT). In case, of a large diameter, pipe (more than inches) the determination maximum penetration wall thickness must be taken into the consideration. This paper is revisited the mathematical derivation of the determination of wall thickness measurement based on tangential radiography technique (TRT). The mathematical approach used in this derivation is the Pythagoras theorem and geometrical principles. In order to derive the maximum penetration wall thickness a similar approach is used. (authors)

  15. Air-coupled ultrasound for plate thickness measurements

    OpenAIRE

    Waag, Grunde

    2017-01-01

    Non-destructive testing using ultrasound is well established as a technique of inspecting miscellaneous structures and components. Ultrasonic waves propagating in an elastic solid are sensitive to both the material and geometrical properties of the solid. Decades of experience have shown that it is possible to extract these properties from the waves in an efficient and reliable way in a variety of practical measurement settings. Different techniques have been developed over many decades, and ...

  16. Selection of the ''best'' model for converting beta backscatter count readings into thickness measurements

    International Nuclear Information System (INIS)

    Smiriga, N.G.

    1976-01-01

    This report compares two models for converting beta backscatter count readings into thickness measurements. The necessary formulas to be used in an unweighted and weighted regression analysis are listed. The question of whether one should perform a regression analysis using the five available standard thicknesses or whether one should, in addition to these standard thicknesses, use zero as a standard thickness is decided. A weighted regression analysis is compared with an unweighted one for each model. The ''best'' model is selected, and the conclusions of the analysis are presented

  17. Sonographic Measurement of AP Diameter and Wall Thickness of the Gallbladder

    International Nuclear Information System (INIS)

    Chung, S.K.; Lee, J. S.; Huh, S. J.; Baek, I. S.

    1982-01-01

    Call bladder size and wall thickness are important in the assessment of the pathologic condition. Authors have measured AP diameter of gallbladder and evaluated the change of all thickness between fasting and postprandial state. The results were as follows: 1. The mean of AP diameter was 2.18+0.49cm 2. The wall thickness was 2.7+0.6mm in fasting state and 3.3+0.8mm after meal. 3. The increase of wall thickness after fat meal was significant statistically(p<.001)

  18. The determination of the pressure-viscosity coefficient of two traction oils using film thickness measurements

    NARCIS (Netherlands)

    Leeuwen, van H.J.

    2010-01-01

    The pressure-viscosity coefficients of two commercial traction fluids are determined by fitting calculation results on accurate film thickness measurements, obtained at a wide range of speeds, and different temperatures. Film thickness values are calculated using a numerical method and approximation

  19. A semi-automated method for measuring thickness and white matter ...

    African Journals Online (AJOL)

    A semi-automated method for measuring thickness and white matter integrity of the corpus callosum. ... and interhemispheric differences. Future research will determine normal values for age and compare CC thickness with peripheral white matter volume loss in large groups of patients, using the semiautomated technique.

  20. Reliability of Various Measurement Stations for Determining Plantar Fascia Thickness and Echogenicity

    Directory of Open Access Journals (Sweden)

    Adebisi Bisi-Balogun

    2016-04-01

    Full Text Available This study aimed to determine the relative and absolute reliability of ultrasound (US measurements of the thickness and echogenicity of the plantar fascia (PF at different measurement stations along its length using a standardized protocol. Twelve healthy subjects (24 feet were enrolled. The PF was imaged in the longitudinal plane. Subjects were assessed twice to evaluate the intra-rater reliability. A quantitative evaluation of the thickness and echogenicity of the plantar fascia was performed using Image J, a digital image analysis and viewer software. A sonography evaluation of the thickness and echogenicity of the PF showed a high relative reliability with an Intra class correlation coefficient of ≥0.88 at all measurement stations. However, the measurement stations for both the PF thickness and echogenicity which showed the highest intraclass correlation coefficient (ICCs did not have the highest absolute reliability. Compared to other measurement stations, measuring the PF thickness at 3 cm distal and the echogenicity at a region of interest 1 cm to 2 cm distal from its insertion at the medial calcaneal tubercle showed the highest absolute reliability with the least systematic bias and random error. Also, the reliability was higher using a mean of three measurements compared to one measurement. To reduce discrepancies in the interpretation of the thickness and echogenicity measurements of the PF, the absolute reliability of the different measurement stations should be considered in clinical practice and research rather than the relative reliability with the ICC.

  1. Reliability of Various Measurement Stations for Determining Plantar Fascia Thickness and Echogenicity.

    Science.gov (United States)

    Bisi-Balogun, Adebisi; Cassel, Michael; Mayer, Frank

    2016-04-13

    This study aimed to determine the relative and absolute reliability of ultrasound (US) measurements of the thickness and echogenicity of the plantar fascia (PF) at different measurement stations along its length using a standardized protocol. Twelve healthy subjects (24 feet) were enrolled. The PF was imaged in the longitudinal plane. Subjects were assessed twice to evaluate the intra-rater reliability. A quantitative evaluation of the thickness and echogenicity of the plantar fascia was performed using Image J, a digital image analysis and viewer software. A sonography evaluation of the thickness and echogenicity of the PF showed a high relative reliability with an Intra class correlation coefficient of ≥0.88 at all measurement stations. However, the measurement stations for both the PF thickness and echogenicity which showed the highest intraclass correlation coefficient (ICCs) did not have the highest absolute reliability. Compared to other measurement stations, measuring the PF thickness at 3 cm distal and the echogenicity at a region of interest 1 cm to 2 cm distal from its insertion at the medial calcaneal tubercle showed the highest absolute reliability with the least systematic bias and random error. Also, the reliability was higher using a mean of three measurements compared to one measurement. To reduce discrepancies in the interpretation of the thickness and echogenicity measurements of the PF, the absolute reliability of the different measurement stations should be considered in clinical practice and research rather than the relative reliability with the ICC.

  2. A semi-empirical method for measuring thickness of pipe-wall using gamma scattering technique

    International Nuclear Information System (INIS)

    Vo Hoang Nguyen; Hua Tuyet Le; Le Dinh Minh Quan; Hoang Duc Tam; Le Bao Tran; Tran Thien Thanh; Tran Nguyen Thuy Ngan; Chau Van Tao; VNUHCM-University of Science, Ho Chi Minh City; Huynh Dinh Chuong

    2016-01-01

    In this work, we propose a semi-empirical method for determining the thickness of pipe-wall, of which the determination is performed by combining the experimental and Monte Carlo simulation data. The testing measurements show that this is an efficient method to measure the thickness of pipe-wall. In addition, this work also shows that it could use a NaI(Tl) scintillation detector and a low activity source to measure the thickness of pipe-wall, which is simple, quick and high accuracy method. (author)

  3. Experimental Influences in the Accurate Measurement of Cartilage Thickness in MRI.

    Science.gov (United States)

    Wang, Nian; Badar, Farid; Xia, Yang

    2018-01-01

    Objective To study the experimental influences to the measurement of cartilage thickness by magnetic resonance imaging (MRI). Design The complete thicknesses of healthy and trypsin-degraded cartilage were measured at high-resolution MRI under different conditions, using two intensity-based imaging sequences (ultra-short echo [UTE] and multislice-multiecho [MSME]) and 3 quantitative relaxation imaging sequences (T 1 , T 2 , and T 1 ρ). Other variables included different orientations in the magnet, 2 soaking solutions (saline and phosphate buffered saline [PBS]), and external loading. Results With cartilage soaked in saline, UTE and T 1 methods yielded complete and consistent measurement of cartilage thickness, while the thickness measurement by T 2 , T 1 ρ, and MSME methods were orientation dependent. The effect of external loading on cartilage thickness is also sequence and orientation dependent. All variations in cartilage thickness in MRI could be eliminated with the use of a 100 mM PBS or imaged by UTE sequence. Conclusions The appearance of articular cartilage and the measurement accuracy of cartilage thickness in MRI can be influenced by a number of experimental factors in ex vivo MRI, from the use of various pulse sequences and soaking solutions to the health of the tissue. T 2 -based imaging sequence, both proton-intensity sequence and quantitative relaxation sequence, similarly produced the largest variations. With adequate resolution, the accurate measurement of whole cartilage tissue in clinical MRI could be utilized to detect differences between healthy and osteoarthritic cartilage after compression.

  4. Construction of a human corneal stromal equivalent with non-transfected human corneal stromal cells and acellular porcine corneal stromata.

    Science.gov (United States)

    Diao, Jin-Mei; Pang, Xin; Qiu, Yue; Miao, Ying; Yu, Miao-Miao; Fan, Ting-Jun

    2015-03-01

    A tissue-engineered human corneal stroma (TE-HCS) has been developed as a promising equivalent to the native corneal stroma for replacement therapy. However, there is still a crucial need to improve the current approaches to render the TE-HCS equivalent more favorable for clinical applications. At the present study, we constructed a TE-HCS by incubating non-transfected human corneal stromal (HCS) cells in an acellular porcine corneal stromata (aPCS) scaffold in 20% fetal bovine serum supplemented DMEM/F12 (1:1) medium at 37 °C with 5% CO2in vitro. After 3 days of incubation, the constructed TE-HCS had a suitable tensile strength for transplantation, and a transparency that is comparable to native cornea. The TE-HCS had a normal histological structure which contained regularly aligned collagen fibers and differentiated HCS cells with positive expression of marker and functional proteins, mimicking a native HCS. After transplantation into rabbit models, the TE-HCS reconstructed normal corneal stroma in vivo and function well in maintaining corneal clarity and thickness, indicating that the completely biological TE-HCS could be used as a HCS equivalent. The constructed TE-HCS has promising potentials in regenerative medicine and treatment of diseases caused by corneal stromal disorders. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. In situ measurement of low-Z material coating thickness on high Z substrate for tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, D., E-mail: dmueller@pppl.gov; Roquemore, A. L.; Jaworski, M.; Skinner, C. H.; Miller, J.; Creely, A. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Raman, P.; Ruzic, D. [Department of Nuclear, Plasma, and Radiological Engineering, Center for Plasma Material Interaction, University of Illinois, Urbana, Illinois 61801 (United States)

    2014-11-15

    Rutherford backscattering of energetic particles can be used to determine the thickness of a coating of a low-Z material over a heavier substrate. Simulations indicate that 5 MeV alpha particles from an {sup 241}Am source can be used to measure the thickness of a Li coating on Mo tiles between 0.5 and 15 μm thick. Using a 0.1 mCi source, a thickness measurement can be accomplished in 2 h of counting. This technique could be used to measure any thin, low-Z material coating (up to 1 mg/cm{sup 2} thick) on a high-Z substrate, such as Be on W, B on Mo, or Li on Mo. By inserting a source and detector on a moveable probe, this technique could be used to provide an in situ measurement of the thickness of Li coating on NSTX-U Mo tiles. A test stand with an alpha source and an annular solid-state detector was used to investigate the measurable range of low-Z material thicknesses on Mo tiles.

  6. Reliability assessment for thickness measurements of pipe wall using probability of detection

    International Nuclear Information System (INIS)

    Nakamoto, Hiroyuki; Kojima, Fumio; Kato, Sho

    2013-01-01

    This paper proposes a reliability assessment method for thickness measurements of pipe wall using probability of detection (POD). Thicknesses of pipes are measured by qualified inspectors with ultrasonic thickness gauges. The inspection results are affected by human factors of the inspectors and include some errors, because the inspectors have different experiences and frequency of inspections. In order to ensure reliability for inspection results, first, POD evaluates experimental results of pipe-wall thickness inspection. We verify that the results have differences depending on inspectors including qualified inspectors. Second, two human factors that affect POD are indicated. Finally, it is confirmed that POD can identify the human factors and ensure reliability for pipe-wall thickness inspections. (author)

  7. Measurement of the residual stress distribution in a thick pre-stretched aluminum plate

    Science.gov (United States)

    Yuan, S. X.; Li, X. Q.; M, S.; Zhang, Y. C.; Gong, Y. D.

    2008-12-01

    Thick pre-stretched aluminum alloy plates are widely used in aircraft, while machining distortion caused by initial residual stress release in thick plates is a common and serious problem. To reduce the distortion, the residual stress distribution in thick plate must be measured. According to the characteristics of the thick pre-stretched aluminum alloy plate, based the elastic mechanical theory, this article deduces the modified layer-removal strain method adapting two different strain situations, which are caused by tensile and compressive stress. To validate this method, the residual stresses distribution along the thick direction of plate 2D70T351 is measured by this method, it is shown that the new method deduced in this paper is simple and accurate, and is very useful in engineering.

  8. Nondestructive web thickness measurement of micro-drills with an integrated laser inspection system

    Science.gov (United States)

    Chuang, Shui-Fa; Chen, Yen-Chung; Chang, Wen-Tung; Lin, Ching-Chih; Tarng, Yeong-Shin

    2010-09-01

    Nowadays, the electric and semiconductor industries use numerous micro-drills to machine micro-holes in printed circuit boards. The measurement of web thickness of micro-drills, a key parameter of micro-drill geometry influencing drill rigidity and chip-removal ability, is quite important to ensure quality control. Traditionally, inefficiently destructive measuring method is adopted by inspectors. To improve quality and efficiency of the web thickness measuring tasks, a nondestructive measuring method is required. In this paper, based on the laser micro-gauge (LMG) and laser confocal displacement meter (LCDM) techniques, a nondestructive measuring principle of web thickness of micro-drills is introduced. An integrated laser inspection system, mainly consisting of a LMG, a LCDM and a two-axis-driven micro-drill fixture device, was developed. Experiments meant to inspect web thickness of micro-drill samples with a nominal diameter of 0.25 mm were conducted to test the feasibility of the developed laser inspection system. The experimental results showed that the web thickness measurement could achieve an estimated repeatability of ± 1.6 μm and a worst repeatability of ± 7.5 μm. The developed laser inspection system, combined with the nondestructive measuring principle, was able to undertake the web thickness measuring tasks for certain micro-drills.

  9. Dynamic measurement of the corneal tear film with a Twyman-Green interferometer

    Science.gov (United States)

    Micali, Jason D.; Greivenkamp, John E.; Primeau, Brian C.

    2015-05-01

    An interferometer for measuring dynamic properties of the in vivo tear film on the human cornea has been developed. The system is a near-infrared instantaneous phase-shifting Twyman-Green interferometer. The laser source is a 785 nm solid-state laser, and the system has been carefully designed and calibrated to ensure that the system operates at eye-safe levels. Measurements are made over a 6 mm diameter on the cornea. Successive frames of interferometric height measurements are combined to produce movies showing both the quantitative and qualitative changes in the topography of the tear film surface and structure. To date, measurement periods of up to 120 s at 28.6 frames per second have been obtained. Several human subjects have been examined using this system, demonstrating a surface height resolution of 25 nm and spatial resolution of 6 μm. Examples of features that have been observed in these preliminary studies of the tear film include postblink disruption, evolution, and stabilization of the tear film; tear film artifacts generated by blinking; tear film evaporation and breakup; and the propagation of foreign objects in the tear film. This paper discusses the interferometer design and presents results from in vivo measurements.

  10. Measurement of facial soft tissues thickness using 3D computed tomographic images

    International Nuclear Information System (INIS)

    Jeong, Ho Gul; Kim, Kee Deog; Shin, Dong Won; Hu, Kyung Seok; Lee, Jae Bum; Park, Hyok; Park, Chang Seo; Han, Seung Ho

    2006-01-01

    To evaluate accuracy and reliability of program to measure facial soft tissue thickness using 3D computed tomographic images by comparing with direct measurement. One cadaver was scanned with a Helical CT with 3 mm slice thickness and 3 mm/sec table speed. The acquired data was reconstructed with 1.5 mm reconstruction interval and the images were transferred to a personal computer. The facial soft tissue thickness were measured using a program developed newly in 3D image. For direct measurement, the cadaver was cut with a bone cutter and then a ruler was placed above the cut side. The procedure was followed by taking pictures of the facial soft tissues with a high-resolution digital camera. Then the measurements were done in the photographic images and repeated for ten times. A repeated measure analysis of variance was adopted to compare and analyze the measurements resulting from the two different methods. Comparison according to the areas was analyzed by Mann-Whitney test. There were no statistically significant differences between the direct measurements and those using the 3D images(p>0.05). There were statistical differences in the measurements on 17 points but all the points except 2 points showed a mean difference of 0.5 mm or less. The developed software program to measure the facial soft tissue thickness using 3D images was so accurate that it allows to measure facial soft tissue thickness more easily in forensic science and anthropology

  11. Measurement of facial soft tissues thickness using 3D computed tomographic images

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Ho Gul; Kim, Kee Deog; Shin, Dong Won; Hu, Kyung Seok; Lee, Jae Bum; Park, Hyok; Park, Chang Seo [Yonsei Univ. Hospital, Seoul (Korea, Republic of); Han, Seung Ho [Catholic Univ. of Korea, Seoul (Korea, Republic of)

    2006-03-15

    To evaluate accuracy and reliability of program to measure facial soft tissue thickness using 3D computed tomographic images by comparing with direct measurement. One cadaver was scanned with a Helical CT with 3 mm slice thickness and 3 mm/sec table speed. The acquired data was reconstructed with 1.5 mm reconstruction interval and the images were transferred to a personal computer. The facial soft tissue thickness were measured using a program developed newly in 3D image. For direct measurement, the cadaver was cut with a bone cutter and then a ruler was placed above the cut side. The procedure was followed by taking pictures of the facial soft tissues with a high-resolution digital camera. Then the measurements were done in the photographic images and repeated for ten times. A repeated measure analysis of variance was adopted to compare and analyze the measurements resulting from the two different methods. Comparison according to the areas was analyzed by Mann-Whitney test. There were no statistically significant differences between the direct measurements and those using the 3D images(p>0.05). There were statistical differences in the measurements on 17 points but all the points except 2 points showed a mean difference of 0.5 mm or less. The developed software program to measure the facial soft tissue thickness using 3D images was so accurate that it allows to measure facial soft tissue thickness more easily in forensic science and anthropology.

  12. The study of thickness and density compensation of neutron-measuring moisture system on conveyor belt

    International Nuclear Information System (INIS)

    Jia Wenbao; Su Tongling; Zhang Xiaomin; Xu Zhongfeng

    1999-01-01

    The neutron-measuring transmission moisture system on the conveyer belt is systematically studied. A method of density and thickness compensation has been used to carryout the on-line measurements of the moisture of the unshaped, discontinuous and irregular moving matter. At the same time, the thickness weighed average method is employed to modify the prompt moisture at a fixed time, and to improve the accuracy of measuring the moisture. The experimental data show that the measurement errors are within ±2.5% when the thickness is between 2 cm and 16 cm and the water percentage is between 6% and 16%. The errors can reach 0.2% if thickness weighed average for moving matter lasts for a long time

  13. In-vivo corneal pulsation in relation to in-vivo intraocular pressure and corneal biomechanics assessed in-vitro. An animal pilot study.

    Science.gov (United States)

    Rogala, Maja M; Danielewska, Monika E; Antończyk, Agnieszka; Kiełbowicz, Zdzisław; Rogowska, Marta E; Kozuń, Marta; Detyna, Jerzy; Iskander, D Robert

    2017-09-01

    The aim was to ascertain whether the characteristics of the corneal pulse (CP) measured in-vivo in a rabbit eye change after short-term artificial increase of intraocular pressure (IOP) and whether they correlate with corneal biomechanics assessed in-vitro. Eight New Zealand white rabbits were included in this study and were anesthetized. In-vivo experiments included simultaneous measurements of the CP signal, registered with a non-contact method, IOP, intra-arterial blood pressure, and blood pulse (BPL), at the baseline and short-term elevated IOP. Afterwards, thickness of post-mortem corneas was determined and then uniaxial tensile tests were conducted leading to estimates of their Young's modulus (E). At the baseline IOP, backward stepwise regression analyses were performed in which successively the ocular biomechanical, biometric and cardiovascular predictors were separately taken into account. Results of the analysis revealed that the 3rd CP harmonic can be statistically significantly predicted by E and central corneal thickness (Models: R 2  = 0.662, p biomechanics in-vitro was confirmed. In particular, spectral analysis revealed that higher amplitude and power of the 3rd CP harmonic indicates higher corneal stiffness, while the 1st CP harmonic correlates positively with the corresponding harmonic of the BPL signal. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Automatic measuring system of zirconium thickness for zirconium liner cladding tubes

    International Nuclear Information System (INIS)

    Matsui, K.; Yamaguchi, H.; Hiroshima, T.; Sakamoto, T.; Murayama, R.

    1985-01-01

    An automatic system of pure zirconium liner thickness for zirconium-zircaloy cladding tubes has been successfully developed. The system consists of three parts. (1) An ultrasonic thickness measuring method for mother tubes before cold rolling. (2) An electromagnetic thickness measuring method for the manufactured tubes. (3) An image processing method for the cross sectional view of the manufactured cut tube samples. In Japanese nuclear industry, zirconium-zircaloy cladding tubes have been tested in order to realize load following operation in the atomic power plant. In order to provide for the practical use in the near future, Sumitomo Metal Industries, Ltd. has been studied and established the practical manufacturing process of the zirconium liner cladding tubes. The zirconium-liner cladding tube is a duplex tube comprising an inner layer of pure zirconium bonded to zircaloy metallurgically. The thickness of the pure zirconium is about 10 % of the total wall thickness. Several types of the automatic thickness measuring methods have been investigated instead of the usual microscopic viewing method in which the liner thickness is measured by the microscopic cross sectional view of the cut tube samples

  15. [Macular thickness measured by optical coherence tomography in pseudoaphakic eyes with clear vs yellow implant].

    Science.gov (United States)

    Chamorro, E; Bonnin-Arias, C; Pérez-Carrasco, M J; Alvarez-Rementería, L; Villa-Collar, C; Armadá-Maresca, F; Sánchez-Ramos, C

    2014-04-01

    To study the use of optical coherence tomography (OCT), for measuring the macular thickness variations produced over time in elderly pseudophakic subjects implanted with a clear intraocular lens (IOL) in one eye, and a yellow IOL in the other eye. Macular thickness measurements were obtained in the 36 eyes of 18 subjects over 65 years, with cataracts surgically removed from both eyes and implanted with different absorbance (clear and yellow) IOLs in 2 separate surgeries. Stratus-OCT was used to determine the macular thickness in 2 sessions with 5 years of difference. After 5 years of follow-up, the eyes implanted with clear IOLs revealed a significant decrease in macular thickness. However, in eyes implanted with yellow IOLs the macular thickness remained stable. The mean overall decrease in macular thickness in eyes implanted with clear IOLs was 5 ± 8 μm (P=.02), and foveal thickness reduction was 10 ± 17 μm (P=.02). The macular thickness changes produced in eyes implanted with a yellow IOL differ from those with a clear IOL. These observation point to a possible protective effect of yellow IOL against the harmful effects of light in elderly pseudophakic subjects. However, studies with a longer follow-up are still needed to confirm that the protection provided by this IOL model is clinically significant. Copyright © 2010 Sociedad Española de Oftalmología. Published by Elsevier Espana. All rights reserved.

  16. Area and depth of surfactant-induced corneal injury predicts extent of subsequent ocular responses.

    Science.gov (United States)

    Jester, J V; Petroll, W M; Bean, J; Parker, R D; Carr, G J; Cavanagh, H D; Maurer, J K

    1998-12-01

    To correlate area and depth of initial corneal injury induced by surfactants of differing type and irritant properties with corneal responses and outcome in the same animals over time by using in vivo confocal microscopy (CM). Six groups of six adult rabbits were treated with anionic, cationic, and nonionic surfactants that caused different levels of ocular irritation. Test materials included slight irritants: 5% sodium lauryl sulfate (SLS), polyoxyethylene glycol monoalkyl ether (POE), and 5% 3-isotridecyloxypropyl-bis(polyoxyethylene) ammonium chloride (ITDOP); mild irritants: 5% 3-decyloxypropyl-bis(polyoxyethylene) amine (DOP) and sodium linear alkylbenzene sulfonate (LAS); and a moderate irritant: a proprietary detergent (DTRGT). Ten microliters surfactant were directly applied to the cornea of one eye of each rabbit. Ten untreated rabbits served as control subjects. Area and depth of initial injury was determined by using in vivo CM to measure epithelial thickness, epithelial cell size, corneal thickness, and depth of stromal injury in four corneal regions at 3 hours and at day 1. Area and depth of corneal responses to injury were evaluated at various times from days 3 through 35 by macroscopic grading and quantitative confocal microscopy through-focusing (CMTF). In vivo CM revealed corneal injury with slight irritants to be restricted to the epithelium, whereas the mild and moderate irritants caused complete epithelial cell loss with increasing anterior stromal damage: DOP < LAS < DTRGT. With the slight ocular irritants there was little or no change in corneal thickness or the CMTF intensity profiles. Three hours after treatment, mild and moderate ocular irritants caused a significant increase in corneal thickness, which peaked at day 1 with DOP (483.3+/-80.1 microm) and LAS (572.3+/-60.0 microm) and day 3 with DTRGT (601.4+/-68.7 microm); returning to normal (similar to control values) by day 7 with DOP and day 35 with LAS and DTRGT. The CMTF intensity

  17. The use of radiography for thickness measurement and corrosion monitoring in pipes

    International Nuclear Information System (INIS)

    Edalati, K.; Rastkhah, N.; Kermani, A.; Seiedi, M.; Movafeghi, A.

    2006-01-01

    In this study of pipes of 150 mm diameters, thickness ranging from 4.2 to 15.0 mm was determined by using two radiography techniques: tangential radiography and double wall radiography. It was concluded that thickness losses of 10%, 20% and 50% could be determined by these methods. Formulae were developed for the double wall radiography method with a high precision of thickness measurement for non-insulated pipes. The precision was comparable with ultrasonic measurement results. Corrosion type and corrosion surface could be observed by these methods. Internal or external corrosion produced different effects in tangential radiography. Insulation removal was not necessary using the radiographic techniques

  18. The use of radiography for thickness measurement and corrosion monitoring in pipes

    Energy Technology Data Exchange (ETDEWEB)

    Edalati, K. [Department of NDT, Nuclear Safety and Radiation Protection Technological Centre, AEOI, P.O. Box 14155-1399, Tehran (Iran, Islamic Republic of)]. E-mail: NDT99@aeoi.org.ir; Rastkhah, N. [Department of NDT, Nuclear Safety and Radiation Protection Technological Centre, AEOI, P.O. Box 14155-1399, Tehran (Iran, Islamic Republic of); Kermani, A. [Department of NDT, Nuclear Safety and Radiation Protection Technological Centre, AEOI, P.O. Box 14155-1399, Tehran (Iran, Islamic Republic of); Seiedi, M. [Department of NDT, Nuclear Safety and Radiation Protection Technological Centre, AEOI, P.O. Box 14155-1399, Tehran (Iran, Islamic Republic of); Movafeghi, A. [Department of NDT, Nuclear Safety and Radiation Protection Technological Centre, AEOI, P.O. Box 14155-1399, Tehran (Iran, Islamic Republic of)

    2006-10-15

    In this study of pipes of 150 mm diameters, thickness ranging from 4.2 to 15.0 mm was determined by using two radiography techniques: tangential radiography and double wall radiography. It was concluded that thickness losses of 10%, 20% and 50% could be determined by these methods. Formulae were developed for the double wall radiography method with a high precision of thickness measurement for non-insulated pipes. The precision was comparable with ultrasonic measurement results. Corrosion type and corrosion surface could be observed by these methods. Internal or external corrosion produced different effects in tangential radiography. Insulation removal was not necessary using the radiographic techniques.

  19. The effect of contact lens usage on corneal biomechanical parameters in myopic patients.

    Science.gov (United States)

    Cankaya, Ali B; Beyazyildiz, Emrullah; Ileri, Dilek; Ozturk, Faruk

    2012-07-01

    To determine and compare the corneal biomechanical properties in myopic patients who use contact lenses and those who do not use contact lenses. The study consisted of 56 myopic patients who used contact lenses (study group) and 123 myopic patients who did not use contact lenses (control group). Intraocular pressure (IOP) was measured with an ocular response analyzer (ORA) and a Goldmann applanation tonometer. Central corneal thickness was measured with an ultrasonic pachymeter. Axial length and anterior chamber depth measurements were acquired with contact ultrasound A-scan biometry. The differences in ORA parameters between study and control group participants were analyzed. The mean corneal hysteresis in study and control groups was 10.1 ± 1.6 mm Hg (6.5-15.9 mm Hg) and 9.7 ± 1.5 mm Hg (6.3-14.2 mm Hg), respectively (P = 0.16). The mean corneal resistance factor was 10.4 ± 1.9 mm Hg (4.6-15.5 mm Hg) in the study group compared with 9.6 ± 1.9 mm Hg (5.1-15.0 mm Hg) in the control group. The difference for corneal resistance factor was statistically significant (P = 0.014). There was no significant difference in corneal-compensated IOP (P = 0.24). Mean Goldmann-correlated IOP was significantly higher in the study group than in control subjects (15.8 ± 3.2 vs. 14.7 ± 3.7 mm Hg) (P = 0.044). None of the corneal biomechanical parameters was significantly correlated to duration of contact lens usage in the study group. Our results suggest that ORA-generated parameters may be different in subjects with and without contact lens usage. Further longitudinal studies need to be performed to establish the relevance of our results.

  20. Quantitative CT measures of emphysema and airway wall thickness are related to D(L)CO

    DEFF Research Database (Denmark)

    Grydeland, Thomas B; Thorsen, Einar; Dirksen, Asger

    2011-01-01

    There is limited knowledge on the relationship between diffusing capacity of the lung for carbon monoxide (D(L)CO) and quantitative computed tomography (CT) measures of emphysema and airway wall thickness.......There is limited knowledge on the relationship between diffusing capacity of the lung for carbon monoxide (D(L)CO) and quantitative computed tomography (CT) measures of emphysema and airway wall thickness....

  1. Ellipsometry measurements of thickness of oxide and water layers on spherical and flat silicon surfaces

    International Nuclear Information System (INIS)

    Kenny, M.J.; Netterfield, R.; Wielunski, L.S.

    1998-01-01

    Full text: Ellipsometry has been used to measure the thickness of oxide layers on single crystal silicon surfaces, both flat and spherical and also to measure the extent of adsorption of moisture on the surface as a function of partial water vapour pressure. The measurements form part of an international collaborative project to make a precise determination of the Avogadro constant (ΔN A /N A -8 ) which will then be used to obtain an absolute definition of the kilogram, rather than one in terms of an artefact. Typically the native oxide layer on a cleaned silicon wafer is about 2 nm thick. On a polished sphere this oxide layer is typically 8 to 10 nm thick, the increased thickness being attributed to parameters related to the polishing process. Ellipsometry measurements on an 89 mm diameter polished silicon sphere at both VUW and CSIRO indicated a SiO 2 layer at 7 to 10 nm thick. It was observed that this thickness varied regularly. The crystal orientation of the sphere was determined using electron patterns generated from an electron microscope and the oxide layer was then measured through 180 arcs of great circles along (110) and (100) planes. It was observed that the thickness varied systematically with orientation. The minimum thickness was 7.4 nm at the axis (softest direction in silicon) and the greatest thickness was 9.5 nm at the axis (hardest direction in silicon). This is similar to an orientation dependent cubic pattern which has been observed to be superimposed on polished silicon spheres. At VUW, the sphere was placed in an evacuated bell jar and the ellipsometry signal was observed as the water vapour pressure was progressively increased up to saturation. The amount of water vapour adsorbed at saturation was one or two monolayers, indicating that the sphere does not wet

  2. Measurement of sea ice thickness using electromagnetic sounding; Denji tansaho wo mochiita kaihyoatsu no keisoku

    Energy Technology Data Exchange (ETDEWEB)

    Kawauchi, K; Suzuki, I; Goto, N [Muroran Institute of Technology, Hokkaido (Japan); Hoshiyama, K

    1997-10-22

    Thickness of sea ice is measured by an electromagnetic method making use of the peculiarities of sea ice. Sea ice floats on the seawater (saline water), and the result is two horizontal layers greatly different from each other in conductivity, with seawater being highly conductive and ice being non-conductive. A study is conducted on Lake Kumatori, a saline lake in Abashiri City, in which effort a board of naturally frozen sea ice and a board of sea ice allowed to form on the sea surface at a spot from which ice has been removed are examined. A portable electromagnetic probe EM38 of GEONICS Company is employed to perform measurement in a horizontal dipole mode. To determine the relationship between the obtained conductivity measurements and sea ice thickness, holes are bored in the sea ice boards for the measurement of their thickness for the formulation of an experimental regression equation. Measurements along the traverse line 1 and traverse line 3 are converted into sea ice thickness by use of the experimental regression equation, and the result is that ice thickness is the greatest near the quay growing thinner away from the shore. The study shows that sea ice thickness may be measured accurately by electromagnetic probing. 3 refs., 10 figs.

  3. Structure-function relationship between the octopus perimeter cluster mean sensitivity and sector retinal nerve fiber layer thickness measured with the RTVue optical coherence tomography and scanning laser polarimetry.

    Science.gov (United States)

    Naghizadeh, Farzaneh; Garas, Anita; Vargha, Péter; Holló, Gábor

    2014-01-01

    To determine structure-function relationship between each of 16 Octopus perimeter G2 program clusters and the corresponding 16 peripapillary sector retinal nerve fiber layer thickness (RNFLT) values measured with the RTVue-100 Fourier-domain optical coherence tomography (RTVue OCT) and scanning laser polarimetry with variable corneal compensation (GDx-VCC) and enhanced corneal compensation (GDx-ECC) corneal compensation. One eye of 110 white patients (15 healthy, 20 ocular hypertensive, and 75 glaucoma eyes) were investigated. The Akaike information criterion and the F test were used to identify the best fitting model. Parabolic relationship with logarithmic cluster mean sensitivity and linear sector RNFLT values provided the best fit. For RTVue OCT, significant (P0.05) was found for the control eyes. Mean sensitivity of the Octopus visual field clusters showed significant parabolic relationship with the corresponding peripapillary RNFLT sectors. The relationship was more general with the RTVue OCT than GDx-VCC or GDx-ECC. The results show that visual field clusters of the Octopus G program can be applied for detailed structure-function research.

  4. In situ non-destructive measurement of biofilm thickness and topology in an interferometric optical microscope.

    Science.gov (United States)

    Larimer, Curtis; Suter, Jonathan D; Bonheyo, George; Addleman, Raymond Shane

    2016-06-01

    Biofilms are ubiquitous and impact the environment, human health, dental hygiene, and a wide range of industrial processes. Biofilms are difficult to characterize when fully hydrated, especially in a non-destructive manner, because of their soft structure and water-like bulk properties. Herein a method of measuring and monitoring the thickness and topology of live biofilms of using white light interferometry is described. Using this technique, surface morphology, surface roughness, and biofilm thickness were measured over time without while the biofilm continued to grow. The thickness and surface topology of a P. putida biofilm were monitored growing from initial colonization to a mature biofilm. Measured thickness followed expected trends for bacterial growth. Surface roughness also increased over time and was a leading indicator of biofilm growth. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Microscopic image processing system for measuring nonuniform film thickness profiles: Image scanning ellipsometry

    International Nuclear Information System (INIS)

    Liu, A.H.; Plawsky, J.L.; Wayner, P.C. Jr.

    1993-01-01

    The long-term objective of this research program is to determine the stability and heat transfer characteristics of evaporating thin films. The current objective is to develop and use a microscopic image-processing system (IPS) which has two parts: an image analyzing interferometer (IAI) and an image scanning ellipsometer (ISE). The primary purpose of this paper is to present the basic concept of ISE, which is a novel technique to measure the two dimensional thickness profile of a non-uniform, thin film, from several nm up to several μm, in a steady state as well as in a transient state. It is a full-field imaging technique which can study every point on the surface simultaneously with high spatial resolution and thickness sensitivity, i.e., it can measure and map the 2-D film thickness profile. The ISE was tested by measuring the thickness profile and the refractive index of a nonuniform solid film

  6. Lead Equivalent Thickness Measurement for Mixed Compositions of Barium Plaster Block

    International Nuclear Information System (INIS)

    Norriza Mohd Isa; Muhammad Jamal Muhammad Isa; Nur Shahriza Zainuddin; Mohd Khairusalih Md Zin; Shahrul Azlan Azizan

    2016-01-01

    Measurement of lead equivalent thickness for ionizing radiation exposure room wall shall be performed as stated in Malaysian Standard MS 838. A few numbers of sample blocks with different mixture of barium plaster compositions based and varies certain thickness as a shielding material for exposure room wall belong to a local company were tested by using Cs-137, Co-60 and Am-241 with different activities . Radiations passed through the samples were detected with calibrated survey meter. The distance between radiation source and the detector is about 40 cm. Lead uniformity test on the samples was also determined at three labeled points on the samples. Lead equivalent thicknesses for the samples were evaluated based on a calibration graph that was plotted with lead sheets and with the radiation sources. Results shown that lead equivalent thickness for the samples with same actual physical thickness represent different values for different sources. (author)

  7. Macular thickness and macular volume measurements using spectral domain optical coherence tomography in normal Nepalese eyes

    Directory of Open Access Journals (Sweden)

    Pokharel A

    2016-03-01

    Full Text Available Amrit Pokharel,1 Gauri Shankar Shrestha,2 Jyoti Baba Shrestha2 1Department of Ophthalmology, Kathmandu Medical College Teaching Hospital, 2B P Koirala Lions Centre for Ophthalmic Studies, Institute of Medicine, Kathmandu, Nepal Purpose: To record the normative values for macular thickness and macular volume in normal Nepalese eyes. Methods: In all, 126 eyes of 63 emmetropic subjects (mean age: 21.17±6.76 years; range: 10–37 years were assessed for macular thickness and macular volume, using spectral domain-optical coherence tomography over 6×6 mm2 in the posterior pole. A fast macular thickness protocol was employed. Statistics such as the mean, median, standard deviation, percentiles, and range were used, while a P-value was set at 0.05 to test significance. Results: Average macular thickness and total macular volume were larger in males compared to females. With each year of increasing age, these variables decreased by 0.556 µm and 0.0156 mm3 for average macular thickness and total macular volume, respectively. The macular thickness was greatest in the inner superior section and lowest at the center of the fovea. The volume was greatest in the outer nasal section and thinnest in the fovea. The central subfield thickness (r=-0.243, P=0.055 and foveal volume (r=0.216, P=0.09 did not correlate with age. Conclusion: Males and females differ significantly with regard to macular thickness and macular volume measurements. Reports by other studies that the increase in axial length reduced thickness and volume, were negated by this study which found a positive correlation among axial length, thickness, and volume. Keywords: macular thickness, macular volume, optical coherence tomography, Nepal

  8. Absolute Thickness Measurements on Coatings Without Prior Knowledge of Material Properties Using Terahertz Energy

    Science.gov (United States)

    Roth, Don J.; Cosgriff, Laura M.; Harder, Bryan; Zhu, Dongming; Martin, Richard E.

    2013-01-01

    This study investigates the applicability of a novel noncontact single-sided terahertz electromagnetic measurement method for measuring thickness in dielectric coating systems having either dielectric or conductive substrate materials. The method does not require knowledge of the velocity of terahertz waves in the coating material. The dielectric coatings ranged from approximately 300 to 1400 m in thickness. First, the terahertz method was validated on a bulk dielectric sample to determine its ability to precisely measure thickness and density variation. Then, the method was studied on simulated coating systems. One simulated coating consisted of layered thin paper samples of varying thicknesses on a ceramic substrate. Another simulated coating system consisted of adhesive-backed Teflon adhered to conducting and dielectric substrates. Alumina samples that were coated with a ceramic adhesive layer were also investigated. Finally, the method was studied for thickness measurement of actual thermal barrier coatings (TBC) on ceramic substrates. The unique aspects and limitations of this method for thickness measurements are discussed.

  9. Hyaline cartilage thickness in radiographically normal cadaveric hips: comparison of spiral CT arthrographic and macroscopic measurements.

    Science.gov (United States)

    Wyler, Annabelle; Bousson, Valérie; Bergot, Catherine; Polivka, Marc; Leveque, Eric; Vicaut, Eric; Laredo, Jean-Denis

    2007-02-01

    To assess spiral multidetector computed tomographic (CT) arthrography for the depiction of cartilage thickness in hips without cartilage loss, with evaluation of anatomic slices as the reference standard. Permission to perform imaging studies in cadaveric specimens of individuals who had willed their bodies to science was obtained from the institutional review board. Two independent observers measured the femoral and acetabular hyaline cartilage thickness of 12 radiographically normal cadaveric hips (from six women and five men; age range at death, 52-98 years; mean, 76.5 years) on spiral multidetector CT arthrographic reformations and on coronal anatomic slices. Regions of cartilage loss at gross or histologic examination were excluded. CT arthrographic and anatomic measurements in the coronal plane were compared by using Bland-Altman representation and a paired t test. Differences between mean cartilage thicknesses at the points of measurement were tested by means of analysis of variance. Interobserver and intraobserver reproducibilities were determined. At CT arthrography, mean cartilage thickness ranged from 0.32 to 2.53 mm on the femoral head and from 0.95 to 3.13 mm on the acetabulum. Observers underestimated cartilage thickness in the coronal plane by 0.30 mm +/- 0.52 (mean +/- standard error) at CT arthrography (P cartilage thicknesses at the different measurement points was significant for coronal spiral multidetector CT arthrography and anatomic measurement of the femoral head and acetabulum and for sagittal and transverse CT arthrography of the femoral head (P cartilage thickness from the periphery to the center of the joint ("gradients") were found by means of spiral multidetector CT arthrography and anatomic measurement. Spiral multidetector CT arthrography depicts cartilage thickness gradients in radiographically normal cadaveric hips. (c) RSNA, 2007.

  10. Analysis and Comparison of Thickness and Bending Measurements from Fabric Touch Tester (FTT and Standard Methods

    Directory of Open Access Journals (Sweden)

    Musa Atiyyah Binti Haji

    2018-03-01

    Full Text Available Fabric Touch Tester (FTT is a relatively new device from SDL Atlas to determine touch properties of fabrics. It simultaneously measures 13 touch-related fabric physical properties in four modules that include bending and thickness measurements. This study aims to comparatively analyze the thickness and bending measurements made by the FTT and the common standard methods used in the textile industry. The results obtained with the FTT for 11 different fabrics were compared with that of standard methods. Despite the different measurement principle, a good correlation was found between the two methods used for the assessment of thickness and bending. As FTT is a new tool for textile comfort measurement and no standard yet exists, these findings are essential to determine the reliability of the measurements and how they relate to the well-established standard methods.

  11. Effects of laser in situ keratomileusis (LASIK) on corneal biomechanical measurements with the Corvis ST tonometer.

    Science.gov (United States)

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

    2015-01-01

    This study was initiated to evaluate biomechanical changes using the Corvis ST tonometer (CST) on the cornea after laser in situ keratomileusis (LASIK). University Medical Center Hamburg-Eppendorf, Germany, and Care Vision Refractive Centers, Germany. Retrospective cohort study. This retrospective study included 37 eyes of 37 refractive patients. All CST measurements were performed 1 day before surgery and at the 1-month follow-up examination. The LASIK procedure included mechanical flap preparation using a Moria SBK microkeratome and an Allegretto excimer laser platform. Statistically significant differences were observed for mean first applanation length, mean first and second deflection lengths, mean first and second deflection amplitudes, radius of curvature, and peak distance. Significant positive correlations were found between the change (Δ) of radius of curvature and manifest refraction spherical equivalent (MRSE), ablation depth, and Δintraocular pressure as well as between AD and ΔHC-time. Each diopter of myopic correction in MRSE resulted in an increase in Δradius of curvature of 0.2 mm. Several CST parameters were statistically significantly altered by LASIK, thereby indicating that flap creation, ablation, or both, significantly change the ability of the cornea to absorb or dissipate energy.

  12. Changes in corneal structure with continuous wear of high-Dk soft contact lenses: a pilot study.

    Science.gov (United States)

    González-Méijome, J M; González-Pérez, J; Cerviño, A; Yebra-Pimentel, E; Parafita, M A

    2003-06-01

    Despite numerous studies that have considered the effects of extended wear of high-Dk soft contact lenses on ocular physiology, little attention has been paid to the impact of such lenses on central or peripheral corneal thickness and curvature. The present study aims to report the time course of changes in corneal thickness and curvature that accompanies the 30-night continuous wear of new silicone hydrogel soft contact lenses in a neophyte population in a longitudinal study. Six subjects wore high-Dk lotrafilcon (Dk = 140) on a 30-night replacement schedule for 12 months. Only measurements from the right eye were considered for analysis. Topographical measurements of corneal thickness and curvature were taken. The same parameters were monitored for an additional period of 3 months after lens removal. An almost homogenous increase in corneal radius of curvature was detected for all the locations studied, being statistically significant for the 4-mm cord diameter area. This effect was associated with a progressive thinning effect for the central cornea, whereas midperipheral and peripheral areas did not display such a thinning effect during continuous wear. These effects were still evident for the central cornea 3 months after contact lens wear discontinuation. Continuous wear of high-Dk silicone hydrogel contact lenses is associated with clinically appreciable changes in topographical corneal curvature, whereas only a reduction in corneal thickness is appreciated in the central area. This effect seems to be a result of mechanical pressure induced by these hybrid hyperpermeable materials, characterized by a higher modulus of elasticity. The small sample size compromises the conclusions addressed from this study, and further work will be necessary to confirm the present results.

  13. Ultrasonographic measurement of the axillary recess thickness in an asymptomatic shoulder

    Directory of Open Access Journals (Sweden)

    Gi-Young Park

    2017-04-01

    Full Text Available Purpose The purpose of this study was to measure the axillary recess (AR thickness in an asymptomatic shoulder by using ultrasonography (US and to analyze the factors affecting it. Methods We recruited 141 patients (52 males; 89 females; age, 57.7±9.9 years with unilateral shoulder pain and performed US on the unaffected shoulder. Two physiatrists measured the AR thickness of the unaffected shoulder independently. All patients were examined in an upright sitting position with 90° shoulder abduction. The ultrasonographic transducer was placed longitudinally on the mid-axillary line and along the long axis of the humeral shaft. The factors affecting the AR thickness values were analyzed, and intra-class correlation coefficients were used for assessing the reproducibility of each measurement. Results The intrarater reliability values for the two physiatrists were 0.98 and 0.96, respectively. The inter-rater reliability of the mean AR thickness measurements was 0.91. The mean AR thickness in all subjects, males, and females was 2.8±0.6 mm, 3.1±0.6 mm, and 2.6±0.5 mm (P<0.01, respectively. No difference between the left and the right sides (males, P=0.086; females, P=0.535 or between the dominant and the non-dominant sides (males, P=0.173; female, P=0.244 was found. The AR thickness correlated positively with the height (r=0.313, P<0.01 and the weight (r=0.319, P<0.01. However, it did not correlate with the body mass index (r=0.152, P=0.077 or the age (r=-0.056, P=0.515. Conclusion US measurements of the AR thickness in asymptomatic shoulders demonstrated excellent intrarater and inter-rater reliabilities. The AR thickness showed anatomical variation with sex, height, and weight.

  14. Ultrasonographic measurement of the axillary recess thickness in an asymptomatic shoulder

    Energy Technology Data Exchange (ETDEWEB)

    Park, Gi Young; Lee, Jin Hoon; Kwon, Dae Gil [Dept. of Rehabilitation Medicine, Catholic University of Daegu School of Medicine, Daegu (Korea, Republic of)

    2017-04-15

    The purpose of this study was to measure the axillary recess (AR) thickness in an asymptomatic shoulder by using ultrasonography (US) and to analyze the factors affecting it. We recruited 141 patients (52 males; 89 females; age, 57.7±9.9 years) with unilateral shoulder pain and performed US on the unaffected shoulder. Two physiatrists measured the AR thickness of the unaffected shoulder independently. All patients were examined in an upright sitting position with 90° shoulder abduction. The ultrasonographic transducer was placed longitudinally on the mid-axillary line and along the long axis of the humeral shaft. The factors affecting the AR thickness values were analyzed, and intra-class correlation coefficients were used for assessing the reproducibility of each measurement. The intrarater reliability values for the two physiatrists were 0.98 and 0.96, respectively. The inter-rater reliability of the mean AR thickness measurements was 0.91. The mean AR thickness in all subjects, males, and females was 2.8±0.6 mm, 3.1±0.6 mm, and 2.6±0.5 mm (P<0.01), respectively. No difference between the left and the right sides (males, P=0.086; females, P=0.535) or between the dominant and the non-dominant sides (males, P=0.173; female, P=0.244) was found. The AR thickness correlated positively with the height (r=0.313, P<0.01) and the weight (r=0.319, P<0.01). However, it did not correlate with the body mass index (r=0.152, P=0.077) or the age (r=-0.056, P=0.515). US measurements of the AR thickness in asymptomatic shoulders demonstrated excellent intrarater and inter-rater reliabilities. The AR thickness showed anatomical variation with sex, height, and weight.

  15. Ultrasonic Measurement of Interfacial Layer Thickness of Sub-Quarter-Wavelength

    Energy Technology Data Exchange (ETDEWEB)

    Kim, No Hyu; Lee, Sang Soon [Korea University of Technology and Education, Cheonan (Korea, Republic of)

    2003-12-15

    This paper describes a new technique for thickness measurement of a very thin layer less than one-quarter of the wavelength of ultrasonic wave used in the ultrasonic pulse-echo measurements. The technique determines the thickness of a thin layer in a tapered medium from constructive interference of multiple reflection waves. The interference characteristics are derived and investigated in theoretical and experimental approaches. Modified total reflection wave g(t) defined as difference between total and first reflection waves increases in amplitude as the interfacial layer thickness decreases down to zero. A layer thickness less than one-tenth of the ultrasonic wavelength is measured using the maximum amplitude of g(t) with a good accuracy and sensitivity. The method also requires no inversion process to extract the thickness information from the waveforms of reflected waves, so that it makes possible to have the on-line thickness measurement of a thin layer such as a lubricating oil film in thrust bearings and journal bearings during manufacturing process

  16. Ultrasonic Measurement of Interfacial Layer Thickness of Sub-Quarter-Wavelength

    International Nuclear Information System (INIS)

    Kim, No Hyu; Lee, Sang Soon

    2003-01-01

    This paper describes a new technique for thickness measurement of a very thin layer less than one-quarter of the wavelength of ultrasonic wave used in the ultrasonic pulse-echo measurements. The technique determines the thickness of a thin layer in a tapered medium from constructive interference of multiple reflection waves. The interference characteristics are derived and investigated in theoretical and experimental approaches. Modified total reflection wave g(t) defined as difference between total and first reflection waves increases in amplitude as the interfacial layer thickness decreases down to zero. A layer thickness less than one-tenth of the ultrasonic wavelength is measured using the maximum amplitude of g(t) with a good accuracy and sensitivity. The method also requires no inversion process to extract the thickness information from the waveforms of reflected waves, so that it makes possible to have the on-line thickness measurement of a thin layer such as a lubricating oil film in thrust bearings and journal bearings during manufacturing process

  17. Error Analysis of Ceramographic Sample Preparation for Coating Thickness Measurement of Coated Fuel Particles

    International Nuclear Information System (INIS)

    Liu Xiaoxue; Li Ziqiang; Zhao Hongsheng; Zhang Kaihong; Tang Chunhe

    2014-01-01

    The thicknesses of four coatings of HTR coated fuel particle are very important parameters. It is indispensable to control the thickness of four coatings of coated fuel particles for the safety of HTR. A measurement method, ceramographic sample-microanalysis method, to analyze the thickness of coatings was developed. During the process of ceramographic sample-microanalysis, there are two main errors, including ceramographic sample preparation error and thickness measurement error. With the development of microscopic techniques, thickness measurement error can be easily controlled to meet the design requirements. While, due to the coated particles are spherical particles of different diameters ranged from 850 to 1000μm, the sample preparation process will introduce an error. And this error is different from one sample to another. It’s also different from one particle to another in the same sample. In this article, the error of the ceramographic sample preparation was calculated and analyzed. Results show that the error introduced by sample preparation is minor. The minor error of sample preparation guarantees the high accuracy of the mentioned method, which indicates this method is a proper method to measure the thickness of four coatings of coated particles. (author)

  18. Optical coherence tomography of the effects of stromal hydration on clear corneal incision architecture.

    Science.gov (United States)

    Calladine, Daniel; Tanner, Vaughan

    2009-08-01

    To evaluate the effects of stromal hydration on clear corneal incision (CCI) architecture immediately after surgery using anterior segment optical coherence tomography (AS-OCT). Department of Ophthalmology, Royal Berkshire Hospital, Reading, United Kingdom. Clear corneal incisions in adult eyes were examined using a Visante AS-OCT imaging system within 1 hour of surgery. Half the CCIs had stromal hydration with a balanced salt solution and half did not. Incisions were made with a 2.75 mm steel keratome. Intraocular pressure (IOP) was measured within 90 minutes after surgery. The CCI length and corneal thickness at the CCI site were measured using software built into the AS-OCT system. Thirty CCIs were evaluated. Stromal hydration significantly increased the measured CCI length (Pthe result of a trend toward increased corneal thickness at the CCI site with hydration (PThe mean CCI length was 1.69 mm +/- 0.27 (SD) (range 1.31 to 2.32 mm) with hydration and 1.51 +/- 0.23 mm (range 1.30 to 1.95 mm) without hydration. The mean IOP was 20.9 +/- 8.18 mm Hg and 15.8 +/- 8.20 mm Hg, respectively. The IOP tended to be higher with hydration (Pthe eye with a higher early postoperative IOP, showing the importance of taking stromal hydration into account when designing similar OCT studies of CCI architecture.

  19. Tear progression of symptomatic full-thickness and partial-thickness rotator cuff tears as measured by repeated MRI.

    Science.gov (United States)

    Kim, Yang-Soo; Kim, Sung-Eun; Bae, Sung-Ho; Lee, Hyo-Jin; Jee, Won-Hee; Park, Chang Kyun

    2017-07-01

    The purpose of this study was to analyse the natural course of symptomatic full-thickness and partial-thickness rotator cuff tears treated non-operatively and to identify risk factors affecting tear enlargement. One hundred and twenty-two patients who received non-surgical treatment for a partial- or full-thickness supraspinatus tear were included in this study. All rotator cuff tears were diagnosed with magnetic resonance imaging (MRI), and the same modality was used for follow-up studies. Follow-up MRI was performed after at least a 6-month interval. We evaluated the correlation between tear enlargement and follow-up duration. Eleven risk factors were analysed by both univariate and multivariate analyses to identify factors that affect enlargement of rotator cuff tears. The mean follow-up period was 24.4 ± 19.5 months. Out of 122 patients, 34 (27.9%) patients had an initial full-thickness tear and 88 (72.1%) patients had a partial-thickness tear. Considering all patients together, tear size increased in 51/122 (41.8%) patients, was unchanged in 65/122 (53.3%) patients, and decreased in 6/122 (4.9%) patients. Tear size increased for 28/34 (82.4%) patients with full-thickness tears and 23/88 (26.1%) patients with partial-thickness tears. From the two groups which were followed over 12 months, a higher rate of enlargement was observed in full-thickness tears than in partial-thickness tears (6-12 months, n.s.; 12-24 months, P = 0.002; over 24 months, P rotator cuff tears and 23/88 (26.1%) of symptomatic partial-thickness tears increased in size over a follow-up period of 6-100 months. Full-thickness tears showed a higher rate of enlargement than partial-thickness tears regardless of the follow-up duration. Univariate and multivariate analyses suggested that full-thickness tear was the most reliable risk factor for tear enlargement. The clinical relevance of these observations is that full-thickness rotator cuff tears treated conservatively should be

  20. Non-Contact Thickness and Profile Measurements of Rolled Aluminium Strip Using EMAT

    International Nuclear Information System (INIS)

    Hobbis, A.; Aruleswaran, A.

    2006-01-01

    Accurate measurement of strip thickness is a very high priority for the aluminium rolled product industry. This paper presents the findings of trials to measure the thickness of aluminium strip using a send-receive, radially polarised Electromagnetic Acoustic Transducer (EMAT). A broadband EMAT system, developed at Warwick University, UK with a centre frequency of approximately 5 MHz and frequency content up to 12 MHz was used. The resultant ultrasonic waveforms have been processed using Fourier analysis. Static measurements of aluminium alloy samples in the thickness range between 0.28 mm to 2.8 mm have been measured using this non-contact approach at stand-offs of up to 2 mm. Measurements across the aluminium strip width to evaluate its profile for quality control was also carried out successfully. Some of the experiments and results obtained are described in detail

  1. Method of accurate thickness measurement of boron carbide coating on copper foil

    Science.gov (United States)

    Lacy, Jeffrey L.; Regmi, Murari

    2017-11-07

    A method is disclosed of measuring the thickness of a thin coating on a substrate comprising dissolving the coating and substrate in a reagent and using the post-dissolution concentration of the coating in the reagent to calculate an effective thickness of the coating. The preferred method includes measuring non-conducting films on flexible and rough substrates, but other kinds of thin films can be measure by matching a reliable film-substrate dissolution technique. One preferred method includes determining the thickness of Boron Carbide films deposited on copper foil. The preferred method uses a standard technique known as inductively coupled plasma optical emission spectroscopy (ICPOES) to measure boron concentration in a liquid sample prepared by dissolving boron carbide films and the Copper substrates, preferably using a chemical etch known as ceric ammonium nitrate (CAN). Measured boron concentration values can then be calculated.

  2. Measurement of Mucosal Thickness in Denture-bearing Area of Edentulous Mandible

    Directory of Open Access Journals (Sweden)

    Jian Dong

    2015-01-01

    Full Text Available Background: The thickness of the alveolar mucosa influences the probability of the occurrence of denture-induced irritations. Thick denture-supporting tissues offer relief from mucosal tenderness and ulcers; however, the uniformity of the thickness across the entire mandibular alveolar mucosa cannot be accurately determined in edentulous patients. This study aimed to assess the mucosal thickness of the denture-bearing area in the edentulous mandible. Methods: Twenty-seven edentulous patients underwent cone-beam computed tomography scanning, wherein the patients wore a record base to retract soft tissues away from the alveolar mucosa. The measured regions were the central incisor (IC, lateral incisor (IL, canine (Ca, first premolar (P1, second premolar (P2, first molar (M1, and second molar (M2 regions. The thickness was measured in the alveolar ridge crest (T, buccal (B1-B4, and lingual (L1-L4 alveolar ridge mucosa. The average thickness of the mucosa at buccal sides (B and lingual sides (L were also assessed. Results: The differences in the mucosal thickness between the left and right sides were not significant. In the Ca-M2 regions, T was the thickest, and L3 was the thinnest of all the measured points in the same regions. L was significantly less than B in posterior regions (P < 0.01. On the other hand, M2 at L4 was thinnest of all the measured regions from Ca to M2 (P < 0.01, and was thicker than IC, IL, P1, and P2 at B2. Conclusions: Since the mucosal thickness of denture-bearing area in the edentulous mandible is not uniform; the tissue surface of the denture base or custom tray should be selectively relieved, which may reduce the risk of denture-induced irritations.

  3. Characterization of the flooding in vertical tubes by means of the film thickness measurement

    International Nuclear Information System (INIS)

    Malandrone, M.; Mioliggi, L.; Panella, B.; Scorta, G.

    1992-01-01

    The air-water countercurrent flow up to the flooding transition in a vertical tube has been experimentally investigated by liquid film thickness measurement performed by means of an electrical two-wires conductance probe. The liquid film mean thickness, the probability density function, the spectral power density and the power of the signal have been derived for a wide range of air and water flow rate, and related to the flow pattern with particular attention to the flooding phenomena. (6 figures) (Author)

  4. Relationship between macular thickness measurement and signal strength using Stratus optical coherence tomography

    OpenAIRE

    Segal, Ori; Shapira, Yinon; Gershoni, Assaf; Vainer, Igor; Nemet, Arie Y; Geffen, Noa; Mimouni, Michael

    2016-01-01

    Ori Segal,1 Yinon Shapira,2 Assaf Gershoni,1 Igor Vainer,2 Arie Y Nemet,1 Noa Geffen,1 Michael Mimouni2 1Department of Ophthalmology, Meir Medical Center, Kfar Saba, Israel and the Sackler School of Medicine, Tel Aviv University, Tel Aviv, 2Department of Ophthalmology, Rambam Health Care Campus, Haifa, Israel Purpose: To examine the relationship between signal strength and macular thickness as measured by Stratus optical coherence tomography (OCT)’s fast macular thickness protocol...

  5. The determination of the pressure-viscosity coefficient of a lubricant through an accurate film thickness formula and accurate film thickness measurements : part 2 : high L values

    NARCIS (Netherlands)

    Leeuwen, van H.J.

    2011-01-01

    The pressure-viscosity coefficient of a traction fluid is determined by fitting calculation results on accurate film thickness measurements, obtained at different speeds, loads, and temperatures. Through experiments, covering a range of 5.6 thickness values are

  6. SEA ICE THICKNESS MEASUREMENT BY GROUND PENETRATING RADAR FOR GROUND TRUTH OF MICROWAVE REMOTE SENSING DATA

    Directory of Open Access Journals (Sweden)

    M. Matsumoto

    2018-04-01

    Full Text Available Observation of sea ice thickness is one of key issues to understand regional effect of global warming. One of approaches to monitor sea ice in large area is microwave remote sensing data analysis. However, ground truth must be necessary to discuss the effectivity of this kind of approach. The conventional method to acquire ground truth of ice thickness is drilling ice layer and directly measuring the thickness by a ruler. However, this method is destructive, time-consuming and limited spatial resolution. Although there are several methods to acquire ice thickness in non-destructive way, ground penetrating radar (GPR can be effective solution because it can discriminate snow-ice and ice-sea water interface. In this paper, we carried out GPR measurement in Lake Saroma for relatively large area (200 m by 300 m, approximately aiming to obtain grand truth for remote sensing data. GPR survey was conducted at 5 locations in the area. The direct measurement was also conducted simultaneously in order to calibrate GPR data for thickness estimation and to validate the result. Although GPR Bscan image obtained from 600MHz contains the reflection which may come from a structure under snow, the origin of the reflection is not obvious. Therefore, further analysis and interpretation of the GPR image, such as numerical simulation, additional signal processing and use of 200 MHz antenna, are required to move on thickness estimation.

  7. Sea Ice Thickness Measurement by Ground Penetrating Radar for Ground Truth of Microwave Remote Sensing Data

    Science.gov (United States)

    Matsumoto, M.; Yoshimura, M.; Naoki, K.; Cho, K.; Wakabayashi, H.

    2018-04-01

    Observation of sea ice thickness is one of key issues to understand regional effect of global warming. One of approaches to monitor sea ice in large area is microwave remote sensing data analysis. However, ground truth must be necessary to discuss the effectivity of this kind of approach. The conventional method to acquire ground truth of ice thickness is drilling ice layer and directly measuring the thickness by a ruler. However, this method is destructive, time-consuming and limited spatial resolution. Although there are several methods to acquire ice thickness in non-destructive way, ground penetrating radar (GPR) can be effective solution because it can discriminate snow-ice and ice-sea water interface. In this paper, we carried out GPR measurement in Lake Saroma for relatively large area (200 m by 300 m, approximately) aiming to obtain grand truth for remote sensing data. GPR survey was conducted at 5 locations in the area. The direct measurement was also conducted simultaneously in order to calibrate GPR data for thickness estimation and to validate the result. Although GPR Bscan image obtained from 600MHz contains the reflection which may come from a structure under snow, the origin of the reflection is not obvious. Therefore, further analysis and interpretation of the GPR image, such as numerical simulation, additional signal processing and use of 200 MHz antenna, are required to move on thickness estimation.

  8. Thickness measurement by two-sided step-heating thermal imaging

    Science.gov (United States)

    Li, Xiaoli; Tao, Ning; Sun, J. G.; Zhang, Cunlin; Zhao, Yuejin

    2018-01-01

    Infrared thermal imaging is a promising nondestructive technique for thickness prediction. However, it is usually thought to be only appropriate for testing the thickness of thin objects or near-surface structures. In this study, we present a new two-sided step-heating thermal imaging method which employed a low-cost portable halogen lamp as the heating source and verified it with two stainless steel step wedges with thicknesses ranging from 5 mm to 24 mm. We first derived the one-dimensional step-heating thermography theory with the consideration of warm-up time of the lamp, and then applied the nonlinear regression method to fit the experimental data by the derived function to determine the thickness. After evaluating the reliability and accuracy of the experimental results, we concluded that this method is capable of testing thick objects. In addition, we provided the criterions for both the required data length and the applicable thickness range of the testing material. It is evident that this method will broaden the thermal imaging application for thickness measurement.

  9. Relationship between renal cortex and parenchyma thickness and renal function: study with CT measurement

    International Nuclear Information System (INIS)

    Xu Yufeng; Tang Guangjian; Jiang Xuexiang

    2006-01-01

    Objective: To study the relationship between renal morphology and renal function, and to assess the value of CT as a criterion to grade renal function. Methods: Enhancement CT were performed in 89 patients with no local renal disease whose split renal glomerular filtration rates (GFR) were measured by renal dynamic imaging with 99 Tc m -DTPA. The 178 kidneys were divided into normal renal function, mild and severe renal impairment groups according to renal function. Differences between three groups respect to the mean thickness of renal cortex and parenchyma were assessed by ANOVA. Using Pearson's correlation test, the correlation between the renal cortex, parenchyma thicknesses and renal GFR were examined. The value of CT in predicting renal function was assessed by using ROC analysis. Results: The renal cortex thicknesses of normal renal function, mild and severe renal impairment groups were (5.9±1.1), (4.6± 1.1), and (3.3±1.0) mm respectively, and the renal parenchyma thicknesses were (26.3±4.2), (21.3±4.6), (16.2±4.6) mm. There were significant differences of renal cortex, parenchyma thicknesses between 3 groups (cortex F=54.78, P<0.01; parenehyma F=43.90, P<0.01). The thicknesses of renal cortex (r=0.752, P<0.01), parenchyma (r=0.738, P<0.01) had positive linear correlation with renal function. ROC analysis of the renal cortex thicknesses measured by CT in predicting mild and severe renal impairment showed that the Az was 0.860 and 0.905 respectively, whereas that of parenchyma was 0.868 and 0.884. Conclusion: The thicknesses of renal cortex, parenchyma measured by CT can reflect renal function. CT was a supplementary method to assess renal function. (authors)

  10. Measurement of lateral charge diffusion in thick, fully depleted, back-illuminated CCDs

    Energy Technology Data Exchange (ETDEWEB)

    Karcher, Armin; Bebek, Christopher J.; Kolbe, William F.; Maurath, Dominic; Prasad, Valmiki; Uslenghi, Michela; Wagner, Martin

    2004-06-30

    Lateral charge diffusion in back-illuminated CCDs directly affects the point spread function (PSF) and spatial resolution of an imaging device. This can be of particular concern in thick, back-illuminated CCDs. We describe a technique of measuring this diffusion and present PSF measurements for an 800 x 1100, 15 mu m pixel, 280 mu m thick, back-illuminated, p-channel CCD that can be over-depleted. The PSF is measured over a wavelength range of 450 nm to 650 nm and at substrate bias voltages between 6 V and 80 V.

  11. A convenient method for X-ray analysis in TEM that measures mass thickness and composition

    Science.gov (United States)

    Statham, P.; Sagar, J.; Holland, J.; Pinard, P.; Lozano-Perez, S.

    2018-01-01

    We consider a new approach for quantitative analysis in transmission electron microscopy (TEM) that offers the same convenience as single-standard quantitative analysis in scanning electron microscopy (SEM). Instead of a bulk standard, a thin film with known mass thickness is used as a reference. The procedure involves recording an X-ray spectrum from the reference film for each session of acquisitions on real specimens. There is no need to measure the beam current; the current only needs to be stable for the duration of the session. A new reference standard with a large (1 mm x 1 mm) area of uniform thickness of 100 nm silicon nitride is used to reveal regions of X-ray detector occlusion that would give misleading results for any X-ray method that measures thickness. Unlike previous methods, the new X-ray method does not require an accurate beam current monitor but delivers equivalent accuracy in mass thickness measurement. Quantitative compositional results are also automatically corrected for specimen self-absorption. The new method is tested using a wedge specimen of Inconel 600 that is used to calibrate the high angle angular dark field (HAADF) signal to provide a thickness reference and results are compared with electron energy-loss spectrometry (EELS) measurements. For the new X-ray method, element composition results are consistent with the expected composition for the alloy and the mass thickness measurement is shown to provide an accurate alternative to EELS for thickness determination in TEM without the uncertainty associated with mean free path estimates.

  12. Analysis of biological characteristics of corneal endothelium in old patients with high myopia

    Directory of Open Access Journals (Sweden)

    Ya-Qiong Chen

    2014-11-01

    Full Text Available AIM: To analyze quantitatively the biological characteristics of corneal endothelium in old patients of high myopia with non-contact automatic corneal endothelial microscope.METHODS:A total of 189 old patients(197 eyeswere divided into the high myopia group and the normal control group according to refractive diopter, in which the former 98 cases(103 eyes, the latter 91 cases(94 eyes. The hexagonal cell(6A, the coefficient of variation(CV, the average cell area(AVE, the average cell density(CDand the central corneal thickness(CCTwere measured by non-contact automatic corneal endothelium. SPSS 14.0 software was used to analyze their percentage. Z-test was used to compare the mean and Chi-square test was used to compare the rate in between. RESULTS: The average cell density in high myopia patients decreased, but there were 14 eyes >3 000/mm2, 11 eyes 2 and 78 eyes in the 2 000~3 000/mm2, there were each 0 eye, 3 eyes and 91 eyes respectively in the normal control group. There was statistically significant difference between high myopia group and control(χ2=19.11, PPP>0.05. CONCLUSION: There will provide a reference valuable for clinical surgeon. Because according to the changes of parameters and morphology of the corneal endothelial cells, we can understand the repair ability, to predict the consequence of the treatment, in order to determine the design and the choice of a surgical.

  13. Manual B-mode versus automated radio-frequency carotid intima-media thickness measurements

    NARCIS (Netherlands)

    Dogan, Soner; Plantinga, Yvonne; Dijk, Joke M.; van der Graaf, Yolanda; Grobbee, Diederick E.; Bots, Michiel L.; Algra, N. N.; Doevendans, P. A.; Eikelboom, C.; van der Graaf, Y.; Grobbee, E.; Kappelle, L. J.; Mali, W. P. Th M.; Moll, F. L.; Rutten, G. E. H. M.; Visseren, F. L. J.

    2009-01-01

    Carotid intima-media thickness (CIMT) serves as an indicator of atherosclerosis and cardiovascular risk. Manual measurements of B-mode ultrasound images are the most applied method. Automated measurements with radiofrequency (RF) ultrasound have been suggested as an alternative. The aim of this

  14. CT measurement of normal pericardial thickness in adults on computed tomography

    International Nuclear Information System (INIS)

    Choi, Young Woo; Park, Chan Sup; Jeon, Yong Sun; Bae, In Young; Choi, Sung Gyu; Koo, Jin Hoe; Chung, Won Kyun

    1998-01-01

    The purpose of this study was to establish, using computed tomography, the normal thickness of the pericardium in adults. Materials and Methods: CT scans of 50 patients, including sections through the level of the heart, were reviewed. Patients were excluded if there were any suspicions of pericardial abnormality such as infectious or neoplastic diseases. Twenty-four of the 50 were men and 26 were women; their mean age was 47.0(range,18-76) years. We measured pericardial thickness at the level of the right ventricle, interventricular septum and left ventricle, and also compared pericardial thickness in terms of age and sex. Results: In all patients, the pericardium was observed in the right ventricular region; in 41 (82%) at the interventricular septum; and in 41 (82%) along the left ventricle. The mean thickness of normal pericardium at the level of the right ventricle, interventricular septum, and left ventricle was 1.8 mm ± 0.5 mm, 1.8 mm ± 0.4 mm, and 1.7 mm ± 0.5 mm, respectively. No statistically significant correlation was apparent between pericardial thickness and age group (p > 0.63, ANOVA test). Mean pericardial thickness was 1.9 mm ± 0.6 mm in males and 1.7 mm ± 0.4 mm in females; thus, no statistically significant correlation was apparent between pericardial thickness and sex (p >0.29, Student's t-test). Conclusion: The pericardium was best visualized in sections through the right ventricle.The mean thickness of normal pericardium was 1.8 mm ± 0.5 mm and pericardial thickness did not differ according to age or sex

  15. A new measurement method of coatings thickness based on lock-in thermography

    Science.gov (United States)

    Zhang, Jin-Yu; Meng, Xiang-bin; Ma, Yong-chao

    2016-05-01

    Coatings have been widely used in modern industry and it plays an important role. Coatings thickness is directly related to the performance of the functional coatings, therefore, rapid and accurate coatings thickness inspection has great significance. Existing coatings thickness measurement method is difficult to achieve fast and accurate on-site non-destructive coatings inspection due to cost, accuracy, destruction during inspection and other reasons. This paper starts from the introduction of the principle of lock-in thermography, and then performs an in-depth study on the application of lock-in thermography in coatings inspection through numerical modeling and analysis. The numerical analysis helps explore the relationship between coatings thickness and phase, and the relationship lays the foundation for accurate calculation of coatings thickness. The author sets up a lock-in thermography inspection system and uses thermal barrier coatings specimens to conduct an experiment. The specimen coatings thickness is measured and calibrated to verify the quantitative inspection. Experiment results show that the lock-in thermography method can perform fast coatings inspection and the inspection accuracy is about 95%. Therefore, the method can meet the field testing requirements for engineering projects.

  16. Measurement of sheath thickness by lining out grooves in the Hall-type stationary plasma thrusters

    International Nuclear Information System (INIS)

    Yu Daren; Wu Zhiwen; Ning Zhongxi; Wang Xiaogang

    2007-01-01

    Using grooves created along the axial direction of the discharge channel, a method for measuring sheath thickness in Hall-type stationary plasma thrusters has been developed. By distorting the wall surface using these grooves, it is possible to numerically study the effect of the wall surface on the sheath and near wall conductivity. Monte Carlo method is applied to calculate the electron temperature variation with different groove depths. The electron dynamic process in the plasma is described by a test particle method with the electron randomly entering the sheath from the discharge channel and being reflected back. Numerical results show that the reflected electron temperature is hardly affected by the wall surface if the groove depth is much less than the sheath thickness. On the other hand, the reflected electron temperature increases if the groove depth is much greater than the sheath thickness. The reflected electron temperature has a sharp jump when the depth of groove is on the order of the sheath thickness. The simulation is repeated with different sheath thicknesses and the results are the same. Therefore, a diagnosis mean of the sheath thickness can be developed based on the method. Also the simulation results are in accord with the experimental data. Besides, the measurement method may be applicable to other plasma device with similar orthogonal steady state electrical and magnetic fields

  17. Oxide thickness measurement technique for duplex-layer Zircaloy-4 cladding

    International Nuclear Information System (INIS)

    McClelland, R.G.; O'Leary, P.M.

    1992-01-01

    Siemens Nuclear Power Corporation (SNP) is investigating the use of duplex-layer Zircaloy-4 tubing to improve the waterside corrosion resistance of cladding for high-burnup pressurized water reactor (PWR) fuel designs. Standard SNP PWR cladding is typically 0.762-mm (0.030-in.)-thick Zircaloy-4. The SNP duplex cladding is nominally 0.660-mm (0.026-in.)-thick Zircalloy-4 with an ∼0.102-mm (0.004-in.) outer layer of another, more corrosion-resistant, zirconium-based alloy. It is common industry practice to monitor the in-reactor corrosion behavior of Zircaloy cladding by using an eddy-current 'lift-off' technique to measure the oxide thickness on the outer surface of the fuel cladding. The test program evaluated three different cladding samples, all with the same outer diameter and wall thickness: Zircaloy-4 and duplex clad types D2 and D4

  18. Quantitative analysis and metallic coating thickness measurements by X-ray fluorescence

    International Nuclear Information System (INIS)

    Negrea, Denis; Ducu, Catalin; Malinovschi, Viorel; Moga, Sorin; Boicea, Niculae

    2009-01-01

    Full text: This paperwork covers the use of X-ray fluorescence (XRF) for determining the concentration and the coating thickness on metallic samples. The analysis method presented here may also be applicable to other coatings, providing that the elemental nature of the coating and substrate are compatible with the technical aspects of XRF, such as the absorption coefficient of the system, primary radiation, fluorescent radiation and type of detection. For the coating thickness measurement it was used the substrate-line attenuation method and a computing algorithm was developed. Its advantage relies in the fact that no special calibration with standard samples having different layer thickness is needed. The samples used for evaluation were metallic pieces of iron with zinc-nickel coatings of different thickness obtained by electrochemical deposition. (authors)

  19. Quantitative analysis and metallic coating thickness measurements by X-ray fluorescence

    International Nuclear Information System (INIS)

    Negrea, Denis; Ducu, Catalin; Malinovschi, Viorel; Moga, Sorin; Boicea, Niculae

    2009-01-01

    This work deals with the use of X-ray fluorescence (XRF) for determining the concentration and the coating thickness on metallic samples. The analysis method presented here may also be applicable to other coatings, providing that the elemental nature of the coating and substrate are compatible with the technical aspects of XRF, such as the absorption coefficient of the system, primary radiation, fluorescent radiation and type of detection. For the coating thickness measurement it was used the substrate-line attenuation method and an algorithm was developed. Its advantage relies in the fact that no special calibration with standard samples having different layer thickness is needed. The samples used for evaluation were metallic pieces of iron with zinc-nickel coatings of different thickness obtained by electrochemical deposition. (authors)

  20. Development of a human corneal epithelium model utilizing a collagen vitrigel membrane and the changes of its barrier function induced by exposing eye irritant chemicals.

    Science.gov (United States)

    Takezawa, Toshiaki; Nishikawa, Kazunori; Wang, Pi-Chao

    2011-09-01

    The brief TEER (trans-epithelial electrical resistance) assay after exposing chemicals to corneal epithelium in vivo is known as a suitable method for evaluating corneal irritancy and permeability quantitatively and continuously. A collagen vitrigel membrane we previously developed is a thin (about 20 μm thick) and transparent membrane composed of high density collagen fibrils equivalent to connective tissues in vivo, e.g. corneal Bowman's membrane. To develop such a TEER assay system in vitro utilizing a human corneal epithelial model, HCE-T cells (a human corneal epithelial cell line) were cultured on the collagen vitrigel membrane substratum prepared in a Millicell chamber suitable for TEER measurement. Human corneal epithelium model possessing 5-6 cell layers sufficient for TEER assay was successfully reconstructed on the substratum in the Millicell chamber by culturing the cells in monolayer for 2 days and subsequently in air-liquid interface for 7 days. The exposure of chemicals to the model induced the time-dependent relative changes of TEER in response to the characteristic of each chemical within a few minutes. These results suggest that the TEER assay using the human corneal epithelial model is very useful for an ocular irritancy evaluation as an alternative to the Draize eye irritation test. Copyright © 2011 Elsevier Ltd. All rights reserved.

  1. Measurement of Li target thickness in the EVEDA Li Test Loop

    Energy Technology Data Exchange (ETDEWEB)

    Kanemura, Takuji, E-mail: kanemura.takuji@jaea.go.jp [Japan Atomic Energy Agency, 4002 Narita, O-arai, Higashi-Ibaraki-gun, Ibaraki 311-1393 (Japan); Kondo, Hiroo; Furukawa, Tomohiro; Hirakawa, Yasushi [Japan Atomic Energy Agency, 4002 Narita, O-arai, Higashi-Ibaraki-gun, Ibaraki 311-1393 (Japan); Hoashi, Eiji; Yoshihashi, Sachiko; Horiike, Hiroshi [Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan); Wakai, Eiichi [Japan Atomic Energy Agency, 4002 Narita, O-arai, Higashi-Ibaraki-gun, Ibaraki 311-1393 (Japan)

    2015-10-15

    Highlights: • The objective is to validate stability of the IFMIF liquid Li target flowing at 15 m/s. • Design requirement of target thickness fluctuation is ±1 mm. • Mean and maximum wave amplitude are 0.26 and 1.46 mm, respectively. • Average thickness can be well predicted with developed analytical model. • Li target was adequately stable and satisfied design requirement. - Abstract: A high-speed (nominal: 15 m/s, range: 10–16 m/s) liquid lithium wall jet is planned to serve as the target for two 40 MeV and 125 mA deuteron beams in the International Fusion Materials Irradiation Facility (IFMIF). The design requirement of target thickness stability is 25 ± 1 mm under a vacuum of 10{sup −3} Pa. This paper presents the results of the target thickness measurement conducted in the EVEDA Li Test Loop under a wide range of conditions including the IFMIF condition (target speed of 10, 15, and 20 m/s; vacuum pressure of 10{sup −3} Pa; and Li temperature of 250 °C). For measurement, we use a laser probe method that we developed in advance; this method generates statistical measurements method using a laser distance meter. The measurement results obtained under the IFMIF nominal condition (15 m/s, 10{sup −3} Pa, 250 °C) at the IFMIF beam center are as follows: average target thickness = 26.08 ± 0.09 mm (2σ), mean wave amplitude = 0.26 ± 0.01 mm (2σ), and maximum wave amplitude = 1.46 ± 0.25 mm (2σ). Of the total wave components, 99.7% are within the design requirement. The analytically predicted target thickness is in excellent agreement with the experimental data, resulting in successful characterization of the Li target thickness.

  2. Sea-ice thickness from field measurements in the northwestern Barents Sea

    Science.gov (United States)

    King, Jennifer; Spreen, Gunnar; Gerland, Sebastian; Haas, Christian; Hendricks, Stefan; Kaleschke, Lars; Wang, Caixin

    2017-02-01

    The Barents Sea is one of the fastest changing regions of the Arctic, and has experienced the strongest decline in winter-time sea-ice area in the Arctic, at -23±4% decade-1. Sea-ice thickness in the Barents Sea is not well studied. We present two previously unpublished helicopter-borne electromagnetic (HEM) ice thickness measurements from the northwestern Barents Sea acquired in March 2003 and 2014. The HEM data are compared to ice thickness calculated from ice draft measured by ULS deployed between 1994 and 1996. These data show that ice thickness varies greatly from year to year; influenced by the thermodynamic and dynamic processes that govern local formation vs long-range advection. In a year with a large inflow of sea-ice from the Arctic Basin, the Barents Sea ice cover is dominated by thick multiyear ice; as was the case in 2003 and 1995. In a year with an ice cover that was mainly grown in situ, the ice will be thin and mechanically unstable; as was the case in 2014. The HEM data allow us to explore the spatial and temporal variability in ice thickness. In 2003 the dominant ice class was more than 2 years old; and modal sea-ice thickness varied regionally from 0.6 to 1.4 m, with the thinner ice being either first-year ice, or multiyear ice which had come into contact with warm Atlantic water. In 2014 the ice cover was predominantly locally grown ice less than 1 month old (regional modes of 0.5-0.8 m). These two situations represent two extremes of a range of possible ice thickness distributions that can present very different conditions for shipping traffic; or have a different impact on heat transport from ocean to atmosphere.

  3. Role of experimental resolution in measurements of critical layer thickness for strained-layer epitaxy

    International Nuclear Information System (INIS)

    Fritz, I.J.

    1987-01-01

    Experimental measurements of critical layer thicknesses (CLT's) in strained-layer epitaxy are considered. Finite experimental resolution can have a major effect on measured CLT's and can easily lead to spurious results. The theoretical approach to critical layer thicknesses of J. W. Matthews [J. Vac. Sci. Technol. 12, 126 (1975)] has been modified in a straightforward way to predict the apparent critical thickness for an experiment with finite resolution in lattice parameter. The theory has also been modified to account for the general empirical result that fewer misfit dislocations are generated than predicted by equilibrium calculation. The resulting expression is fit to recent x-ray diffraction data on InGaAs/GaAs and SiGe/Si. The results suggest that CLT's in these systems may not be significantly larger than predicted by equilibrium theory, in agreement with high-resolution measurements

  4. Tundish Cover Flux Thickness Measurement Method and Instrumentation Based on Computer Vision in Continuous Casting Tundish

    Directory of Open Access Journals (Sweden)

    Meng Lu

    2013-01-01

    Full Text Available Thickness of tundish cover flux (TCF plays an important role in continuous casting (CC steelmaking process. Traditional measurement method of TCF thickness is single/double wire methods, which have several problems such as personal security, easily affected by operators, and poor repeatability. To solve all these problems, in this paper, we specifically designed and built an instrumentation and presented a novel method to measure the TCF thickness. The instrumentation was composed of a measurement bar, a mechanical device, a high-definition industrial camera, a Siemens S7-200 programmable logic controller (PLC, and a computer. Our measurement method was based on the computer vision algorithms, including image denoising method, monocular range measurement method, scale invariant feature transform (SIFT, and image gray gradient detection method. Using the present instrumentation and method, images in the CC tundish can be collected by camera and transferred to computer to do imaging processing. Experiments showed that our instrumentation and method worked well at scene of steel plants, can accurately measure the thickness of TCF, and overcome the disadvantages of traditional measurement methods, or even replace the traditional ones.

  5. Reliability of ultrasound thickness measurement of the abdominal muscles during clinical isometric endurance tests.

    Science.gov (United States)

    ShahAli, Shabnam; Arab, Amir Massoud; Talebian, Saeed; Ebrahimi, Esmaeil; Bahmani, Andia; Karimi, Noureddin; Nabavi, Hoda

    2015-07-01

    The study was designed to evaluate the intra-examiner reliability of ultrasound (US) thickness measurement of abdominal muscles activity when supine lying and during two isometric endurance tests in subjects with and without Low back pain (LBP). A total of 19 women (9 with LBP, 10 without LBP) participated in the study. Within-day reliability of the US thickness measurements at supine lying and the two isometric endurance tests were assessed in all subjects. The intra-class correlation coefficient (ICC) was used to assess the relative reliability of thickness measurement. The standard error of measurement (SEM), minimal detectable change (MDC) and the coefficient of variation (CV) were used to evaluate the absolute reliability. Results indicated high ICC scores (0.73-0.99) and also small SEM and MDC scores for within-day reliability assessment. The Bland-Altman plots of agreement in US measurement of the abdominal muscles during the two isometric endurance tests demonstrated that 95% of the observations fall between the limits of agreement for test and retest measurements. Together the results indicate high intra-tester reliability for the US measurement of the thickness of abdominal muscles in all the positions tested. According to the study's findings, US imaging can be used as a reliable method for assessment of abdominal muscles activity in supine lying and the two isometric endurance tests employed, in participants with and without LBP. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Development of ultrasonic heat transfer tube thickness measurement apparatus. Contract research

    Energy Technology Data Exchange (ETDEWEB)

    Ohba, Toshihiro; Katoh, Chiaki; Yanagihara, Takao [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Suetugu, Hidehiko; Yano, Masaya [Sumitomo Chemical Co., Ltd., Tokyo (Japan)

    2003-01-01

    The demonstration test for evaluating reliability of the acid recovery evaporator at Rokkasho Reprocessing Plant has been carried out at JAERI. For the nondestructive measurement of the thickness of heat transfer tubes of the acid recovery evaporator in corrosion test, we have developed thickness measurement apparatus for heat transfer tubes by ultrasonic immersion method with high resolution. The ultrasonic prove in a heat transfer tube can be moved vertically and radially. The results obtained by this apparatus coincident well with those obtained by a destructive method using an optical microscope. (author)

  7. Simultaneous measurement of group refractive index and thickness of optical samples using optical coherence tomography

    International Nuclear Information System (INIS)

    Cheng, Hsu-Chih; Liu, Yi-Cheng

    2010-01-01

    Optical coherence tomography (OCT), based on a Michelson interferometer and utilizing low coherence light as the optical source, is a novel technique for the noninvasive imaging of optical scattering media. A simple OCT scheme based on a 3x3 fiber coupler is presented for the simultaneous measurement of the refractive index and thickness of optical samples. The proposed system enables the refractive index and thickness to be determined without any prior knowledge of the sample parameters and is characterized by a simple and compact configuration, a straightforward measurement procedure, and a low cost. The feasibility of the proposed approach is demonstrated experimentally using BK7 and B270 optical glass samples.

  8. Measurement of the thickness and homogeneity of thin foils by slowing down alpha particles

    International Nuclear Information System (INIS)

    Bimbot, R.; Della Negra, S.; Deprun, C.; Gardes, D.; Rivet, M.F.

    1979-01-01

    The energy loss of 8.785 MeV α particles passing through a thin foil is used to measure the foil thickness. The measurement is performed in various points of the target, the abscissa and ordinate of which are set with precision from the outside of the chamber. This gives a thickness map of the target. The working up of the data, and the use of energy loss tables are made in a standard way. The absolute uncertainty is of some percent for 100 μg/cm 2 foils. The technique has been refined to reach the same precision for 10 μg/cm 2 targets [fr

  9. Uncertainty in stratiform cloud optical thickness inferred from pyranometer measurements at the sea surface

    Directory of Open Access Journals (Sweden)

    Anna Rozwadowska

    2004-06-01

    Full Text Available The relative "plane-parallel" error in a mean cloud optical thickness retrieved from ground-based pyranometer measurements is estimated. The plane-parallel error is defined as the bias introduced by the assumption in the radiative transfer model used in cloud optical thickness retrievals that the atmosphere, including clouds, is horizontally homogeneous on the scale of an individual retrieval. The error is estimated for the optical thickness averaged over the whole domain, which simulates the mean cloud optical thickness obtained from a time series of irradiance measurements. The study is based on 3D Monte Carlo radiative transfer simulations for non-absorbing, all-liquid, layer clouds. Liquid water path distributions in the clouds are simulated by a bounded cascade fractal model. The sensitivity of the error is studied with respect to the following factors: averaging time of irradiance used in an individual retrieval, mean cloud optical thickness, cloud variability, cloud base height and solar zenith angle. In the simulations presented in this paper, the relative bias in the domain averaged cloud optical thickness retrieved from pyranometer measurements varies from +1% for optically thin clouds to nearly -20%. The highest absolute value of the relative bias is expected for thick and variable clouds with high bases (e.g. 1 km and retrievals based on long-term mean irradiances (averaging time of the order of several tens of minutes or hours. The bias can be diminished by using short-term irradiance averages, e.g. of one minute, and by limiting retrievals to low-level clouds.

  10. Abdominal Subcutaneous Fat Thickness Measured by Ultrasonography Correlates with Hyperlipidemia and Steatohepatitis in Obese Children.

    Science.gov (United States)

    Lee, Sung Hyun; Kim, Dongwan; Baek, Min Young; Tchah, Hann; Kim, Yeon Sun; Ryoo, Eell; Kim, Yun Mi

    2015-06-01

    The aim of this study is to evaluate the relationship between abdominal subcutaneous fat thickness measured by ultrasonography (US) and serum lipid profile and liver transaminases in obese children. One hundred and sixty-six children diagnosed with obesity from May 2001 to December 2013 were included in this study. Data on serum lipid profile and liver transaminases were collected from clinical records. Abdominal subcutaneous fat thickness and grade of hepatic steatosis were evaluated by US. Of the 166 children, 107 were diagnosed with hepatic steatosis by US, 46 with grade I, 56 with grade II, and five children with grade III. According to the grade of hepatic steasosis, the average values of midline abdominal subcutaneous fat thickness and right flank abdominal subcutaneous fat thickness measured 2.9±0.8 cm and 1.9±0.7 cm in the normal group, 3.3±0.8 cm and 2.0±0.7 cm in grade I, 3.8±0.8 cm and 2.3±0.8 cm in grade II, and 4.1±0.8 cm and 2.8±1.4 cm in grade III, respectively. Abdominal subcutaneous fat thickness correlated with grade of hepatic steatosis (pabdominal subcutaneous fat thickness correlated with concentration of serum lipids and liver transaminases in the age group of 12-14 years (pAbdominal subcutaneous fat thickness measured by US can be used as a reliable predictor of possible hyperlipidemia and steatohepatitis in children, especially during the adolescent stage.

  11. Retinal nerve fiber layer thickness in normals measured by spectral domain OCT.

    Science.gov (United States)

    Bendschneider, Delia; Tornow, Ralf P; Horn, Folkert K; Laemmer, Robert; Roessler, Christopher W; Juenemann, Anselm G; Kruse, Friedrich E; Mardin, Christian Y

    2010-09-01

    To determine normal values for peripapillary retinal nerve fiber layer thickness (RNFL) measured by spectral domain Optical Coherence Tomography (SOCT) in healthy white adults and to examine the relationship of RNFL with age, gender, and clinical variables. The peripapillary RNFL of 170 healthy patients (96 males and 74 females, age 20 to 78 y) was imaged with a high-resolution SOCT (Spectralis HRA+OCT, Heidelberg Engineering) in an observational cross-sectional study. RNFL thickness was measured around the optic nerve head using 16 automatically averaged, consecutive circular B-scans with 3.4-mm diameter. The automatically segmented RNFL thickness was divided into 32 segments (11.25 degrees each). One randomly selected eye per subject entered the study. Mean RNFL thickness in the study population was 97.2 ± 9.7 μm. Mean RNFL thickness was significantly negatively correlated with age (r = -0.214, P = 0.005), mean RNFL decrease per decade was 1.90 μm. As age dependency was different in different segments, age-correction of RNFL values was made for all segments separately. Age-adjusted RNFL thickness showed a significant correlation with axial length (r = -0.391, P = 0.001) and with refractive error (r = 0.396, P<0.001), but not with disc size (r = 0.124). Normal RNFL results with SOCT are comparable to those reported with time-domain OCT. In accordance with the literature on other devices, RNFL thickness measured with SOCT was significantly correlated with age and axial length. For creating a normative database of SOCT RNFL values have to be age adjusted.

  12. Relationship between Central Corneal Thickness, Vitreous ...

    African Journals Online (AJOL)

    eye health and also aid in developing strategies to help early diagnoses and management of ... of disease, determining the effec veness of medical .... air-dry. A drop of topical anaesthe c (Tetracaine HCl. 0.1%) was ins lled in subject's eye.

  13. Corneal endothelial cell density and morphology in healthy Turkish eyes.

    Science.gov (United States)

    Arıcı, Ceyhun; Arslan, Osman Sevki; Dikkaya, Funda

    2014-01-01

    Purpose. To describe the normative values of corneal endothelial cell density, morphology, and central corneal thickness in healthy Turkish eyes. Methods. Specular microscopy was performed in 252 eyes of 126 healthy volunteers (M : F, 42 : 84). Parameters studied included mean endothelial cell density (MCD), mean cell area (MCA), coefficient of variation (CV) in cell size, percentage of hexagonal cells, and central corneal thickness (CCT). Results. The mean age of volunteers was 44.3 ± 13.5 (range, 20 to 70) years. There was a statistically significant decrease in MCD (P Filipino eyes and higher than that described in Indian, Thai, and Iranian eyes.

  14. Calculated /alpha/-induced thick target neutron yields and spectra, with comparison to measured data

    International Nuclear Information System (INIS)

    Wilson, W.B.; Bozoian, M.; Perry, R.T.

    1988-01-01

    One component of the neutron source associated with the decay of actinide nuclides in many environments is due to the interaction of decay /alpha/ particles in (/alpha/,n) reactions on low Z nuclides. Measurements of (/alpha/,n) thick target neutron yields and associated neutron spectra have been made for only a few combinations of /alpha/ energy and target nuclide or mixtures of actinide and target nuclides. Calculations of thick target neutron yields and spectra with the SOURCES code require /alpha/-energy-dependent cross sections for (/alpha/,n) reactions, as well as branching fractions leading to the energetically possible levels of the product nuclides. A library of these data has been accumulated for target nuclides of Z /le/ 15 using that available from measurements and from recent GNASH code calculations. SOURCES, assuming neutrons to be emitted isotopically in the center-of-mass system, uses libraries of /alpha/ stopping cross sections, (/alpha/,n) reaction cross reactions, product nuclide level branching fractions, and actinide decay /alpha/ spectra to calculate thick target (/alpha/,n) yields and neutron spectra for homogeneous combinations of nuclides. The code also calculates the thick target yield and angle intergrated neutron spectrum produced by /alpha/-particle beams on targets of homogeneous mixtures of nuclides. Illustrative calculated results are given and comparisons are made with measured thick target yields and spectra. 50 refs., 1 fig., 2 tabs

  15. Evaluation of the x-ray fluorescence method of precious metal plating thickness measurements. Technological spinoff report

    International Nuclear Information System (INIS)

    Carson, J.S.; Hearn, N.K.; Pettie, C.B.

    1975-09-01

    It is shown that gold and silver plating thickness measurements made using an x-ray spectrograph could be closely correlated with thicknesses measured from sectional samples. Good correlations were also shown for single overlays of gold over silver when each layer was less than 0.0003 inch thick

  16. Polysaccharide coating of human corneal endothelium

    DEFF Research Database (Denmark)

    Schroder, H D; Sperling, S

    1977-01-01

    Electron microscopy revealed the presence of a 600-1500 A thick layer of polysaccharide on the surface of human corneal endothelial cells. The surface layer was visualized by combined fixation and staining in a mixture of ruthenium red and osmium tetroxide. The coating material was stable for at ...... for at least 39 h post mortem and was retained on disintegrating cells....

  17. A digital instrument for nondestructive measurements of coating thicknesses by beta backscattering

    Science.gov (United States)

    Farcasiu, D. M.; Apostolescu, T.; Bozdog, H.; Badescu, E.; Bohm, V.; Stanescu, S. P.; Jianu, A.; Bordeanu, C.; Cracium, M. V.

    1992-02-01

    The elements of nondestructive gauging of coatings applied on various metal bases are presented. The intensity of the backscattered beta radiations is related to the thickness of the coating. With a fixed measuring geometry and radioactive sources (147Pm, 204Tl, 90Sr+90Y) the intensity of the backscattered beta particles is dependent on the following parameters: coating thickness, atomic number of the coating material and of the base, the beta particle energy and the surface finish. It can be used for the measurement of a wide range of coating thicknesses provided that the difference between the coating and the support atomic numbers is at least 20%. Fields of application include electronics, electrotechnique and so on.

  18. A digital instrument for nondestructive measurements of coating thicknesses by beta backscattering

    International Nuclear Information System (INIS)

    Farcasiu, D.M.; Apostolescu, T.; Bozdog, H.; Badescu, E.; Bohm, V.; Stanescu, S.P.; Jianu, A.; Bordeanu, C.; Craciun, M.V.

    1992-01-01

    The elements of nondestructive gauging of coatings applied on various metal bases are presented. The intensity of the backscattered beta radiations is related to the thickness of the coating. With a fixed measuring geometry and radioactive sources ( 147 Pm, 204 Tl, 90 Sr+ 90 Y) the intensity of the backscattered beta particles is dependent on the following parameters: Coating thickness, atomic number of the coating material and of the base, the beta particle energy and the surface finish. It can be used for the measurement of a wide range of coating thicknesses provided that the difference between the coating and the support atomic numbers is at least 20%. Fields of application include electronics, electrotechnique and so on. (orig.)

  19. Corneal and Retinal Neuronal Degeneration in Early Stages of Diabetic Retinopathy.

    Science.gov (United States)

    Srinivasan, Sangeetha; Dehghani, Cirous; Pritchard, Nicola; Edwards, Katie; Russell, Anthony W; Malik, Rayaz A; Efron, Nathan

    2017-12-01

    To examine the neuronal structural integrity of cornea and retina as markers for neuronal degeneration in nonproliferative diabetic retinopathy (NPDR). Participants were recruited from the broader Brisbane community, Queensland, Australia. Two hundred forty-one participants (187 with diabetes and 54 nondiabetic controls) were examined. Diabetic retinopathy (DR) was graded according to the Early Treatment Diabetic Retinopathy Study (ETDRS) scale. Corneal nerve fiber length (CNFL), corneal nerve branch density (CNBD), corneal nerve fiber tortuosity (CNFT), full retinal thickness, retinal nerve fiber layer (RNFL), ganglion cell complex (GCC), focal (FLV) and global loss volumes (GLV), hemoglobin A1c (HbA1c), nephropathy, neuropathy, and cardiovascular measures were examined. The central zone (P = 0.174), parafoveal thickness (P = 0.090), perifovea (P = 0.592), RNFL (P = 0.866), GCC (P = 0.798), and GCC GLV (P = 0.338) did not differ significantly between the groups. In comparison to the control group, those with very mild NPDR and those with mild NPDR had significantly higher focal loss in GCC volume (P = 0.036). CNFL was significantly lower in those with mild NPDR (P = 0.004) in comparison to the control group and those with no DR. The CNBD (P = 0.094) and CNFT (P = 0.458) did not differ between the groups. Both corneal and retinal neuronal degeneration may occur in early stages of diabetic retinopathy. Further studies are required to examine these potential markers for neuronal degeneration in the absence of clinical signs of DR.

  20. Receiver calibration and the nonlinearity parameter measurement of thick solid samples with diffraction and attenuation corrections.

    Science.gov (United States)

    Jeong, Hyunjo; Barnard, Daniel; Cho, Sungjong; Zhang, Shuzeng; Li, Xiongbing

    2017-11-01

    This paper presents analytical and experimental techniques for accurate determination of the nonlinearity parameter (β) in thick solid samples. When piezoelectric transducers are used for β measurements, the receiver calibration is required to determine the transfer function from which the absolute displacement can be calculated. The measured fundamental and second harmonic displacement amplitudes should be modified to account for beam diffraction and material absorption. All these issues are addressed in this study and the proposed technique is validated through the β measurements of thick solid samples. A simplified self-reciprocity calibration procedure for a broadband receiver is described. The diffraction and attenuation corrections for the fundamental and second harmonics are explicitly derived. Aluminum alloy samples in five different thicknesses (4, 6, 8, 10, 12cm) are prepared and β measurements are made using the finite amplitude, through-transmission method. The effects of diffraction and attenuation corrections on β measurements are systematically investigated. When diffraction and attenuation corrections are all properly made, the variation of β between different thickness samples is found to be less than 3.2%. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Detrital illite crystals identified from crystallite thickness measurements in siliciclastic sediments

    Science.gov (United States)

    Aldega, L.; Eberl, D.D.

    2005-01-01

    Illite crystals in siliciclastic sediments are heterogeneous assemblages of detrital material coming from various source rocks and, at paleotemperatures >70 ??C, of superimposed diagenetic modification in the parent sediment. We distinguished the relative proportions of 2M1 detrital illite and possible diagenetic 1Md + 1M illite by a combined analysis of crystal-size distribution and illite polytype quantification. We found that the proportions of 1Md + 1M and 2M1 illite could be determined from crystallite thickness measurements (BWA method, using the MudMaster program) by unmixing measured crystallite thickness distributions using theoretical and calculated log-normal and/or asymptotic distributions. The end-member components that we used to unmix the measured distributions were three asymptotic-shaped distributions (assumed to be the diagenetic component of the mixture, the 1Md + 1M polytypes) calculated using the Galoper program (Phase A was simulated using 500 crystals per cycle of nucleation and growth, Phase B = 333/cycle, and Phase C = 250/ cycle), and one theoretical log-normal distribution (Phase D, assumed to approximate the detrital 2M1 component of the mixture). In addition, quantitative polytype analysis was carried out using the RockJock software for comparison. The two techniques gave comparable results (r2 = 0.93), which indicates that the unmixing method permits one to calculate the proportion of illite polytypes and, therefore, the proportion of 2M1 detrital illite, from crystallite thickness measurements. The overall illite crystallite thicknesses in the samples were found to be a function of the relative proportions of thick 2M1 and thin 1Md + 1M illite. The percentage of illite layers in I-S mixed layers correlates with the mean crystallite thickness of the 1Md + 1M polytypes, indicating that these polytypes, rather than the 2M1 polytype, participate in I-S mixed layering.

  2. Americium-241 use of measurement lead equivalent thickness for medical x-ray room: A review

    International Nuclear Information System (INIS)

    Mohd Khalid Matori; Husaini Saleh; Abd Aziz Mhd Ramli; Muhammad Jamal Md Isa; Mohd Firdaus Abd Rahman; Zainal Jamaluddin

    2010-01-01

    Lead equivalent thickness measurement of a shielding material in diagnostic radiology is very important to ensure that requirements for the purpose of radiation protection of patients, employees and the public are met. The Malaysian Ministry of Health (MOH) has established that the irradiation room must have sufficient shielding thickness, for example for general radiography it must be at least equal to 2.0 mm of Pb, for panoramic dental radiography at least equal to 1.5 mm of Pb and for mammography should be a minimum of 1.0 mm of Pb. This paper presents a technique using americium-241 source to test and verify the integrity of the shielding thickness in term of lead equivalent for X-ray room at health centres. Results of measurement of 30 irradiation rooms conducted from 2009 to mid 2010 were analyzed for this presentation. Technical comparison of the attenuation of gamma rays from Am-241 source through the walls of the irradiation room and pieces of lead were used to assess the lead equivalent thickness of the walls. Results showed that 96.7 % of the irradiation rooms tested meet the requirements of the Ministry of Health and is suitable for the installation of the intended diagnostic X-ray apparatus. Some specific positions such as door knobs and locks, electrical plug sockets were identified with potential to not met the required lead equivalent thickness hence may contribute to higher radiation exposure to workers and the public. (author)

  3. Comparing electron tomography and HRTEM slicing methods as tools to measure the thickness of nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Alloyeau, D., E-mail: alloyeau.damien@gmail.com [Laboratoire Materiaux et Phenomenes Quantiques, Universite Paris 7/CNRS, UMR 7162, 2 Place Jussieu, 75251 Paris (France); Laboratoire d' Etude des Microstructures - ONERA/CNRS, UMR 104, B.P. 72, 92322 Chatillon (France); Ricolleau, C. [Laboratoire Materiaux et Phenomenes Quantiques, Universite Paris 7/CNRS, UMR 7162, 2 Place Jussieu, 75251 Paris (France); Oikawa, T. [Laboratoire Materiaux et Phenomenes Quantiques, Universite Paris 7/CNRS, UMR 7162, 2 Place Jussieu, 75251 Paris (France); JEOL (Europe) SAS, Espace Claude Monet, 1 Allee de Giverny, 78290 Croissy-sur-Seine (France); Langlois, C. [Laboratoire Materiaux et Phenomenes Quantiques, Universite Paris 7/CNRS, UMR 7162, 2 Place Jussieu, 75251 Paris (France); Le Bouar, Y.; Loiseau, A. [Laboratoire d' Etude des Microstructures - ONERA/CNRS, UMR 104, B.P. 72, 92322 Chatillon (France)

    2009-06-15

    Nanoparticles' morphology is a key parameter in the understanding of their thermodynamical, optical, magnetic and catalytic properties. In general, nanoparticles, observed in transmission electron microscopy (TEM), are viewed in projection so that the determination of their thickness (along the projection direction) with respect to their projected lateral size is highly questionable. To date, the widely used methods to measure nanoparticles thickness in a transmission electron microscope are to use cross-section images or focal series in high-resolution transmission electron microscopy imaging (HRTEM 'slicing'). In this paper, we compare the focal series method with the electron tomography method to show that both techniques yield similar particle thickness in a range of size from 1 to 5 nm, but the electron tomography method provides better statistics since more particles can be analyzed at one time. For this purpose, we have compared, on the same samples, the nanoparticles thickness measurements obtained from focal series with the ones determined from cross-section profiles of tomograms (tomogram slicing) perpendicular to the plane of the substrate supporting the nanoparticles. The methodology is finally applied to the comparison of CoPt nanoparticles annealed ex situ at two different temperatures to illustrate the accuracy of the techniques in detecting small particle thickness changes.

  4. Performance of a fiber optic sensor for online measurement of coating thickness

    Science.gov (United States)

    D'Emilia, Giulio

    1999-01-01

    Some aspects concerning a methodology for the measurement of thickness of dry and wet coatings which is based on a fiber optic probe are discussed in order to verify the feasibility of this approach and the capability of such a probe of on- line measuring. In this preliminary step of the research some problems discussed mainly concerning the methodology which has been proposed and which is based on the measuring of the reflectance of the coating plated on thin steel sheets for use in the food industry. Furthermore the effect of the main interfering and modifying quantities is discussed both theoretically and experimentally when the measurement has to be carried out in order to allow on-line coating thickness measurements with satisfactory accuracy.

  5. Triceps skin fold thickness as a measure of body fat in Nigerian ...

    African Journals Online (AJOL)

    Background: Skin fold thickness (SFT) at selected areas offers a simple method of subcutaneous fat assessment and provides a good estimate of obesity and body fat distribution. The triceps SFT has been shown to be one of the best and most popular sites for SFT measurement in children. Objective: To assess the body fat ...

  6. An optical method for measuring the thickness of a falling condensate in gravity assisted heat pipe

    Directory of Open Access Journals (Sweden)

    Kasanický Martin

    2015-01-01

    Full Text Available A large number of variables is the main problem of designing systems which uses heat pipes, whether it is a traditional - gravity, or advanced - capillary, pulsating, advanced heat pipes. This article is a methodology for measuring the thickness of the falling condensate in gravitational heat pipes, with using the optical triangulation method, and the evaluation of risks associated with this method.

  7. Correction of thickness measurement errors for two adjacent sheet structures in MR images

    International Nuclear Information System (INIS)

    Cheng Yuanzhi; Wang Shuguo; Sato, Yoshinobu; Nishii, Takashi; Tamura, Shinichi

    2007-01-01

    We present a new method for measuring the thickness of two adjacent sheet structures in MR images. In the hip joint, in which the femoral and acetabular cartilages are adjacent to each other, a conventional measurement technique based on the second derivative zero crossings (called the zero-crossings method) can introduce large underestimation errors in measurements of cartilage thickness. In this study, we have developed a model-based approach for accurate thickness measurement. We model the imaging process for two adjacent sheet structures, which simulate the two articular cartilages in the hip joint. This model can be used to predict the shape of the intensity profile along the sheet normal orientation. Using an optimization technique, the model parameters are adjusted to minimize the differences between the predicted intensity profile and the actual intensity profiles observed in the MR data. The set of model parameters that minimize the difference between the model and the MR data yield the thickness estimation. Using three phantoms and one normal cadaveric specimen, the usefulness of the new model-based method is demonstrated by comparing the model-based results with the results generated using the zero-crossings method. (author)

  8. Thin-film thickness measurement using x-ray peak ratioing in the scanning electron microscope

    International Nuclear Information System (INIS)

    Elliott, N.E.; Anderson, W.E.; Archuleta, T.A.; Stupin, D.M.

    1981-01-01

    The procedure used to measure laser target film thickness using a scanning electron microscope is summarized. This method is generally applicable to any coating on any substrate as long as the electron energy is sufficient to penetrate the coating and the substrate produces an x-ray signal which can pass back through the coating and be detected

  9. Aluminum hydroxide coating thickness measurements and brushing tests on K West Basin fuel elements

    International Nuclear Information System (INIS)

    Pitner, A.L.

    1998-01-01

    Aluminum hydroxide coating thicknesses were measured on fuel elements stored in aluminum canisters in K West Basin using specially developed eddy current probes . The results were used to estimate coating inventories for MCO fuel,loading. Brushing tests successfully demonstrated the ability to remove the coating if deemed necessary prior to MCO loading

  10. Radiographic technique and brackets affect measurements of proximal enamel thickness on mandibular incisors

    NARCIS (Netherlands)

    Ang, Amy Giok Phing; Steegmans, Pauline Antoinette Josephine; Kerdijk, Wouter; Livas, Christos; Ren, Yijin

    2017-01-01

    Objective: To investigate the influence of radiographic film and tube positioning, the presence and the size of brackets on in vitro measurements of proximal enamel thickness of mandibular incisors on periapical radiographs aimed to aid planning of interproximal enamel reduction procedures in

  11. Femoral cartilage thickness measurements in healthy individuals: learning, practicing and publishing with TURK-MUSCULUS.

    Science.gov (United States)

    Özçakar, Levent; Tunç, Hakan; Öken, Öznur; Ünlü, Zeliha; Durmuş, Bekir; Baysal, Özlem; Altay, Zuhal; Tok, Fatih; Akkaya, Nuray; Doğu, Beril; Çapkın, Erhan; Bardak, Ayşenur; Çarlı, Alparslan Bayram; Buğdaycı, Derya; Toktaş, Hasan; Dıraçoğlu, Demirhan; Gündüz, Berrin; Erhan, Belgin; Kocabaş, Hilal; Erden, Gül; Günendi, Zafer; Kesikburun, Serdar; Omaç, Özlem Köroğlu; Taşkaynatan, Mehmet Ali; Şenel, Kazım; Uğur, Mahir; Yalçınkaya, Ebru Yılmaz; Öneş, Kadriye; Atan, Çiğdem; Akgün, Kenan; Bilgici, Ayhan; Kuru, Ömer; Özgöçmen, Salih

    2014-01-01

    Measurement of the femoral cartilage thickness by using in-vivo musculoskeletal ultrasonography (MSUS) has been previously shown to be a valid and reliable method in previous studies; however, to our best notice, normative data has not been provided before in the healthy population.The aim of our study was to provide normative data regarding femoral cartilage thicknesses of healthy individuals with collaborative use of MSUS. This is across-sectional study run at Physical and Rehabilitation Medicine Departments of 18 Secondary and Tertiary Centers in Turkey. 1544 healthy volunteers (aged between 25-40 years) were recruited within the collaboration of TURK-MUSCULUS (Turkish Musculoskeletal Ultrasonography Study Group). Subjects who had a body mass index value of less than 30 and who did not have signs and symptoms of any degenerative/inflammatory arthritis or other rheumatic diseases, history of knee trauma and previous knee surgery were enrolled. Ultrasonographic measurements were performed axially from the suprapatellar window by using linear probes while subjects' knees were in maximum flexion. Three (mid-point) measurements were taken from both knees (lateral condyle, intercondylar area, medial condyle). A total of 2876 knees (of 817 M, 621 F subjects) were taken into analysis after exclusion of inappropriate images. Mean cartilage thicknesses were significantly lower in females than males (all p< 0.001). Thickness values negatively correlated with age; negatively (females) and positively (males) correlated with smoking. Men who regularly exercised had thicker cartilage than who did not exercise (all p < 0.05). Increased age (in both sexes) and absence of exercise (males) were found to be risk factors for decreased cartilage thicknesses. Further data pertaining to other countries would be interesting to uncover whether ethnic differences also affect cartilage thickness. Collaborative use of MSUS seems to be promising in this regard.

  12. Validation of Airborne FMCW Radar Measurements of Snow Thickness Over Sea Ice in Antarctica

    Science.gov (United States)

    Galin, Natalia; Worby, Anthony; Markus, Thorsten; Leuschen, Carl; Gogineni, Prasad

    2012-01-01

    Antarctic sea ice and its snow cover are integral components of the global climate system, yet many aspects of their vertical dimensions are poorly understood, making their representation in global climate models poor. Remote sensing is the key to monitoring the dynamic nature of sea ice and its snow cover. Reliable and accurate snow thickness data are currently a highly sought after data product. Remotely sensed snow thickness measurements can provide an indication of precipitation levels, predicted to increase with effects of climate change in the polar regions. Airborne techniques provide a means for regional-scale estimation of snow depth and distribution. Accurate regional-scale snow thickness data will also facilitate an increase in the accuracy of sea ice thickness retrieval from satellite altimeter freeboard estimates. The airborne data sets are easier to validate with in situ measurements and are better suited to validating satellite algorithms when compared with in situ techniques. This is primarily due to two factors: better chance of getting coincident in situ and airborne data sets and the tractability of comparison between an in situ data set and the airborne data set averaged over the footprint of the antennas. A 28-GHz frequency modulated continuous wave (FMCW) radar loaned by the Center for Remote Sensing of Ice Sheets to the Australian Antarctic Division is used to measure snow thickness over sea ice in East Antarctica. Provided with the radar design parameters, the expected performance parameters of the radar are summarized. The necessary conditions for unambiguous identification of the airsnow and snowice layers for the radar are presented. Roughnesses of the snow and ice surfaces are found to be dominant determinants in the effectiveness of layer identification for this radar. Finally, this paper presents the first in situ validated snow thickness estimates over sea ice in Antarctica derived from an FMCW radar on a helicopterborne platform.

  13. Glaucoma after corneal replacement.

    Science.gov (United States)

    Baltaziak, Monika; Chew, Hall F; Podbielski, Dominik W; Ahmed, Iqbal Ike K

    Glaucoma is a well-known complication after corneal transplantation surgery. Traditional corneal transplantation surgery, specifically penetrating keratoplasty, has been slowly replaced by the advent of new corneal transplantation procedures: primarily lamellar keratoplasties. There has also been an emergence of keratoprosthesis implants for eyes that are high risk of failure with penetrating keratoplasty. Consequently, there are different rates of glaucoma, pathogenesis, and potential treatment in the form of medical, laser, or surgical therapy. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. Thin film thickness measurement error reduction by wavelength selection in spectrophotometry

    International Nuclear Information System (INIS)

    Tsepulin, Vladimir G; Perchik, Alexey V; Tolstoguzov, Victor L; Karasik, Valeriy E

    2015-01-01

    Fast and accurate volumetric profilometry of thin film structures is an important problem in the electronic visual display industry. We propose to use spectrophotometry with a limited number of working wavelengths to achieve high-speed control and an approach to selecting the optimal working wavelengths to reduce the thickness measurement error. A simple expression for error estimation is presented and tested using a Monte Carlo simulation. The experimental setup is designed to confirm the stability of film thickness determination using a limited number of wavelengths

  15. Measurement of neutron yield by 62 MeV proton beam on a thick Beryllium target

    International Nuclear Information System (INIS)

    Alba, R; Cosentino, G; Zoppo, A Del; Pietro, A Di; Figuera, P; Finocchiaro, P; Maiolino, C; Santonocito, D; Schillaci, M; Barbagallo, M; Colonna, N; Boccaccio, P; Esposito, J; Celentano, A; Osipenko, M; Ricco, G; Ripani, M; Viberti, C M; Kostyukov, A

    2013-01-01

    In the framework of research on IVth generation reactors and high intensity neutron sources a low-power prototype neutron amplifier was recently proposed by INFN. It is based on a low-energy, high current proton cyclotron, whose beam, impinging on a thick Beryllium converter, produces a fast neutron spectrum. The world database on the neutron yield from thick Beryllium target in the 70 MeV proton energy domain is rather scarce. The new measurement was performed at LNS, covering a wide angular range from 0 to 150 degrees and an almost complete neutron energy interval. In this contribution the preliminary data are discussed together with the proposed ADS facility.

  16. Value of endometrial thickness measurement for diagnosing focal intrauterine pathology in women without abnormal uterine bleeding

    DEFF Research Database (Denmark)

    Dreisler, E; Sorensen, S Stampe; Ibsen, P H

    2009-01-01

    OBJECTIVE: To assess the diagnostic value of transvaginal sonographic (TVS) measurement of endometrial thickness for diagnosing focal intrauterine pathology in women without abnormal uterine bleeding (AUB). METHODS: A random selection from the Danish Civil Registration System was made: 1660 women...... of endometrial thickness is a poor diagnostic test, but is apparently efficacious in excluding focal intrauterine pathology, especially in postmenopausal women. The 4-5-mm threshold conventionally used to exclude endometrial malignancy in women with postmenopausal bleeding is not transferable to women without...

  17. Role of Measurement of the Maximum Intimal-Medial Thickness in the Brain Health Examination Program

    OpenAIRE

    上山, 憲司; 中川原, 譲二; 武田, 利兵衛; 中村, 博彦

    2005-01-01

    The maximum intimal-medial thickness (Max-IMT) of the carotid artery wall (Max-IMT) was measured by ultrasonography in 1,932 people checked in the brain health examination program in our hospital. We studied relationship Max-IMT and age, systolic blood pressure, presence of asymptomatic cerebral infarction. Five hundreds seventy-two people (29.9%) had atherosclerotic thickness of Max-IMT that was more than 1.1 mm. Normal Max-IMT that less than 1.0 mm was observed in 1,360 people (70.1%). More...

  18. Measurement of oxide-layer thickness of internal granules in high-purity aluminium

    International Nuclear Information System (INIS)

    Takacs, S.; Ditroi, F.; Mahunka, I.

    1989-01-01

    Charged-particle activation analysis was used for the determination of bulk oxygen concentration in aluminium. High-purity aluminium samples and mixtures containing different amounts of alumina were irradiated by 13 MeV 3 He particles. The aim of the investigation was to determine the oxide-layer thickness on the surface of internal aluminium granules. The measurement was carried out by determining the bulk oxygen concentration in the samples, and calculating the oxide-layer thickness, by using model conditions about the microstructure of the aluminium samples. (author) 5 refs

  19. XRD measurement of mean thickness, thickness distribution and strain for illite and illite-smectite crystallites by the Bertaut-Warren-Averbach technique

    Science.gov (United States)

    Drits, Victor A.; Eberl, Dennis D.; Środoń, Jan

    1998-01-01

    A modified version of the Bertaut-Warren-Averbach (BWA) technique (Bertaut 1949, 1950; Warren and Averbach 1950) has been developed to measure coherent scattering domain (CSD) sizes and strains in minerals by analysis of X-ray diffraction (XRD) data. This method is used to measure CSD thickness distributions for calculated and experimental XRD patterns of illites and illite-smectites (I-S). The method almost exactly recovers CSD thickness distributions for calculated illite XRD patterns. Natural I-S samples contain swelling layers that lead to nonperiodic structures in the c* direction and to XRD peaks that are broadened and made asymmetric by mixed layering. Therefore, these peaks cannot be analyzed by the BWA method. These difficulties are overcome by K-saturation and heating prior to X-ray analysis in order to form 10-Å periodic structures. BWA analysis yields the thickness distribution of mixed-layer crystals (coherently diffracting stacks of fundamental illite particles). For most I-S samples, CSD thickness distributions can be approximated by lognormal functions. Mixed-layer crystal mean thickness and expandability then can be used to calculate fundamental illite particle mean thickness. Analyses of the dehydrated, K-saturated samples indicate that basal XRD reflections are broadened by symmetrical strain that may be related to local variations in smectite interlayers caused by dehydration, and that the standard deviation of the strain increases regularly with expandability. The 001 and 002 reflections are affected only slightly by this strain and therefore are suited for CSD thickness analysis. Mean mixed-layer crystal thicknesses for dehydrated I-S measured by the BWA method are very close to those measured by an integral peak width method.

  20. On the comparison between MRI and US imaging for human heel pad thickness measurements

    DEFF Research Database (Denmark)

    Matteoli, Sara; Corbin, Nadège Corbin; Wilhjelm, Jens E.

    2011-01-01

    The human heel pad thickness, defined as the shortest distance between the calcaneus and heel skin, is one of the intrinsic factor which must be taken into account when investigating the biomechanics of the heel pad. US and MRI are the preferable imaging modalities used to measure the heel pad...... thickness as they are both ionizing-free radiations. The aim of this paper is to measure the bone to skin distance of nine heel pad phantoms from MRI and US images, and to compare the results with a true value (TV) in order to find the errors. Paired sample t-test was used to compare the measurements......1530 (P-value=0.402). Results confirm the necessity to investigate on the real speed of sound for the heel pad tissues, in order to have realistic measurements when dealing with human heel pads. __________________________________________________________________________________________________________...

  1. Articular Cartilage Thickness Measured with US is Not as Easy as It Appears

    DEFF Research Database (Denmark)

    Torp-Pedersen, Søren; Bartels, E. M.; Wilhjelm, Jens E.

    2011-01-01

    insonation. If US measurements are compared to measurements with other techniques, they should be corrected for the higher sound speed in cartilage. Purpose: To study whether investigators correctly identify the articular cartilage, whether they insonate orthogonally, and whether they correct for sound speed....... Materials and Methods: A literature search limited to the last 10 years of studies applying US to measure cartilage thickness. Results: 15 studies were identified and they referred to another 8 studies describing methods of thickness measurement. 11 of the 15 studies identified the superficial cartilage...... border incorrectly, and 6 applied oblique insonation. 2 of the 15 studies corrected for sound speed. Of the further 8 studies, one might correctly identify the superficial cartilage border, 4 applied oblique insonation, and none corrected for sound speed. Conclusion: We found that the majority of studies...

  2. An examination of mass thickness measurements with X-ray sources

    International Nuclear Information System (INIS)

    Chen Mincong; Li Hongmei; Chen Ziyu; Shen Ji

    2008-01-01

    A method using X-rays to measure mass thickness is discussed. The method utilizes a filter to absorb low energy and characteristic photons so that the hardened X-ray spectra have a peaked energy distribution. An equivalent X-ray energy, which defines the attenuation in a material of interest can be used. The effect on the X-ray spectra of different filters is examined with Monte Carlo simulation using the EGSnrc package. A theoretical model for X-ray absorption that shows that the method can achieve good precision for a certain range of mass thicknesses is advanced. Experimental results agree well with the theoretical analysis. It is found that for a certain range of mass thicknesses, the relative error can be less than 1% for the aluminum alloy sample at the tube voltage of 30 or 45 kV

  3. An examination of mass thickness measurements with X-ray sources

    Energy Technology Data Exchange (ETDEWEB)

    Chen Mincong; Li Hongmei; Chen Ziyu [Department of Modern Physics, University of Science and Technology of China, Jin Zhai Road, Hefei 230026 (China); Shen Ji [Department of Modern Physics, University of Science and Technology of China, Jin Zhai Road, Hefei 230026 (China)], E-mail: shenji@ustc.edu.cn

    2008-10-15

    A method using X-rays to measure mass thickness is discussed. The method utilizes a filter to absorb low energy and characteristic photons so that the hardened X-ray spectra have a peaked energy distribution. An equivalent X-ray energy, which defines the attenuation in a material of interest can be used. The effect on the X-ray spectra of different filters is examined with Monte Carlo simulation using the EGSnrc package. A theoretical model for X-ray absorption that shows that the method can achieve good precision for a certain range of mass thicknesses is advanced. Experimental results agree well with the theoretical analysis. It is found that for a certain range of mass thicknesses, the relative error can be less than 1% for the aluminum alloy sample at the tube voltage of 30 or 45 kV.

  4. Utilization of the Rutherford backscattering technique for precise measurements of thickness by an alternative procedure

    International Nuclear Information System (INIS)

    Chagas, E.F.

    1985-01-01

    This technique was used to determine the thickness of targets on very thick substrates as this type of target is used a lot in nuclear physics, and especially in γ spectroscpy. The difficulties introduced in this case, occur because of the appearance of a small peak on a very high continuous background, due to the fact that the atomic number of the substrate is bigger than that of the targets. These difficulties are overcome using an alternative procedure to determine precisely the loss of energy of the beam whilst crossing the refered target. Targets of 59 Co, 46-48-50 Ti and 10 B on substrate of Pd and Ta, with thicknesses betwnn 30μg/cm 2 and 500μg/cm 2 were measured with a precision of 5%. The biggest sources of imprecision are the amounts of dE/dX. (Author) [pt

  5. Space- and time-resolved resistive measurements of liquid metal wall thickness

    Energy Technology Data Exchange (ETDEWEB)

    Mirhoseini, S. M. H.; Volpe, F. A., E-mail: fvolpe@columbia.edu [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)

    2016-11-15

    In a fusion reactor internally coated with liquid metal, it will be important to diagnose the thickness of the liquid at various locations in the vessel, as a function of time, and possibly respond to counteract undesired bulging or depletion. The electrical conductance between electrodes immersed in the liquid metal can be used as a simple proxy for the local thickness. Here a matrix of electrodes is shown to provide spatially and temporally resolved measurements of liquid metal thickness in the absence of plasma. First a theory is developed for m × n electrodes, and then it is experimentally demonstrated for 3 × 1 electrodes, as the liquid stands still or is agitated by means of a shaker. The experiments were carried out with Galinstan, but are easily extended to lithium or other liquid metals.

  6. Thickness Measurement of a Film on a Substrate by Low-Frequency Ultrasound

    Institute of Scientific and Technical Information of China (English)

    LI Ming-Xuan; WANG Xiao-Min; MAO Jie

    2004-01-01

    @@ We describe a new simple technique for the low-frequency ultrasonic thickness measurement of an air-backed soft thin layer attached on a hard substrate of finite thickness through the frequency-shifts of the substrate resonances by the substrate-side insonification. A plane compressive wave impinging normally on the substrate surface from a liquid is studied. Low frequency here means an interrogating acoustical wave frequency of less than half of coating to the substrate. Equations for the frequency-shifts are derived and solved by the Newton iterative method and the Taylor expansion method, respectively, indicating satisfactory agreement within the range of interest of thickness ratio of the thin layer to the substrate for a polymer-aluminium structure. An experimental setup is constructed to verify the validity of the technique.

  7. Space- and time-resolved resistive measurements of liquid metal wall thickness

    International Nuclear Information System (INIS)

    Mirhoseini, S. M. H.; Volpe, F. A.

    2016-01-01

    In a fusion reactor internally coated with liquid metal, it will be important to diagnose the thickness of the liquid at various locations in the vessel, as a function of time, and possibly respond to counteract undesired bulging or depletion. The electrical conductance between electrodes immersed in the liquid metal can be used as a simple proxy for the local thickness. Here a matrix of electrodes is shown to provide spatially and temporally resolved measurements of liquid metal thickness in the absence of plasma. First a theory is developed for m × n electrodes, and then it is experimentally demonstrated for 3 × 1 electrodes, as the liquid stands still or is agitated by means of a shaker. The experiments were carried out with Galinstan, but are easily extended to lithium or other liquid metals.

  8. Recovery of Corneal Endothelial Cells from Periphery after Injury.

    Directory of Open Access Journals (Sweden)

    Sang Ouk Choi

    Full Text Available Wound healing of the endothelium occurs through cell enlargement and migration. However, the peripheral corneal endothelium may act as a cell resource for the recovery of corneal endothelium in endothelial injury.To investigate the recovery process of corneal endothelial cells (CECs from corneal endothelial injury.Three patients with unilateral chemical eye injuries, and 15 rabbit eyes with corneal endothelial chemical injuries were studied. Slit lamp examination, specular microscopy, and ultrasound pachymetry were performed immediately after chemical injury and 1, 3, 6, and 9 months later. The anterior chambers of eyes from New Zealand white rabbits were injected with 0.1 mL of 0.05 N NaOH for 10 min (NaOH group. Corneal edema was evaluated at day 1, 7, and 14. Vital staining was performed using alizarin red and trypan blue.Specular microscopy did not reveal any corneal endothelial cells immediately after injury. Corneal edema subsided from the periphery to the center, CEC density increased, and central corneal thickness decreased over time. In the animal study, corneal edema was greater in the NaOH group compared to the control at both day 1 and day 7. At day 1, no CECs were detected at the center and periphery of the corneas in the NaOH group. Two weeks after injury, small, hexagonal CECs were detected in peripheral cornea, while CECs in mid-periphery were large and non-hexagonal.CECs migrated from the periphery to the center of the cornea after endothelial injury. The peripheral corneal endothelium may act as a cell resource for the recovery of corneal endothelium.

  9. Mediterranean diet, micronutrients and macronutrients, and MRI measures of cortical thickness.

    Science.gov (United States)

    Staubo, Sara C; Aakre, Jeremiah A; Vemuri, Prashanthi; Syrjanen, Jeremy A; Mielke, Michelle M; Geda, Yonas E; Kremers, Walter K; Machulda, Mary M; Knopman, David S; Petersen, Ronald C; Jack, Clifford R; Roberts, Rosebud O

    2017-02-01

    The Mediterranean diet (MeDi) is associated with reduced risk of cognitive impairment, but it is unclear whether it is associated with better brain imaging biomarkers. Among 672 cognitively normal participants (mean age, 79.8 years, 52.5% men), we investigated associations of MeDi score and MeDi components with magnetic resonance imaging measures of cortical thickness for the four lobes separately and averaged (average lobar). Higher MeDi score was associated with larger frontal, parietal, occipital, and average lobar cortical thickness. Higher legume and fish intakes were associated with larger cortical thickness: legumes with larger superior parietal, inferior parietal, precuneus, parietal, occipital, lingual, and fish with larger precuneus, superior parietal, posterior cingulate, parietal, and inferior parietal. Higher carbohydrate and sugar intakes were associated with lower entorhinal cortical thickness. In this sample of elderly persons, higher adherence to MeDi was associated with larger cortical thickness. These cross-sectional findings require validation in prospective studies. Copyright © 2016 the Alzheimer's Association. Published by Elsevier Inc. All rights reserved.

  10. Measuring the thickness of austenitic weld deposits on carbon steel walls using a magnetic method

    International Nuclear Information System (INIS)

    Wagner, K.

    1988-01-01

    The theoretical background is described of a magnetic method characterized by a marked compensation of the undesirable effect of δ-ferrite content in the deposit, on the accuracy of measuring deposit thickness. A description is also given of the basic types of sensors and the results are summarized of comparing measurements performed on weld deposits of WWER-type reactor pressure vessels. (author). 7 figs., 5 refs

  11. Corneal Reinnervation and Sensation Recovery in Patients With Herpes Zoster Ophthalmicus: An In Vivo and Ex Vivo Study of Corneal Nerves.

    Science.gov (United States)

    Cruzat, Andrea; Hamrah, Pedram; Cavalcanti, Bernardo M; Zheng, Lixin; Colby, Kathryn; Pavan-Langston, Deborah

    2016-05-01

    To study corneal reinnervation and sensation recovery in Herpes zoster ophthalmicus (HZO). Two patients with HZO were studied over time with serial corneal esthesiometry and laser in vivo confocal microscopy (IVCM). A Boston keratoprosthesis type 1 was implanted, and the explanted corneal tissues were examined by immunofluorescence histochemistry for βIII-tubulin to stain for corneal nerves. The initial central corneal IVCM performed in each patient showed a complete lack of the subbasal nerve plexus, which was in accordance with severe loss of sensation (0 of 6 cm) measured by esthesiometry. When IVCM was repeated 2 years later before undergoing surgery, case 1 showed a persistent lack of central subbasal nerves and sensation (0 of 6). In contrast, case 2 showed regeneration of the central subbasal nerves (4786 μm/mm) with partial recovery of corneal sensation (2.5 of 6 cm). Immunostaining of the explanted corneal button in case 1 showed no corneal nerves, whereas case 2 showed central and peripheral corneal nerves. Eight months after surgery, IVCM was again repeated in the donor tissue around the Boston keratoprosthesis in both patients to study innervation of the corneal transplant. Case 1 showed no nerves, whereas case 2 showed new nerves growing from the periphery into the corneal graft. We demonstrate that regaining corneal innervation and corneal function are possible in patients with HZO as shown by corneal sensation, IVCM, and ex vivo immunostaining, indicating zoster neural damage is not always permanent and it may recover over an extended period of time.

  12. Posterior pole asymmetry analysis and retinal thickness measurements in young relatives of glaucoma patients

    Directory of Open Access Journals (Sweden)

    Gökhan Pekel

    2015-08-01

    Full Text Available The presence of a family history of glaucoma is a known risk factor for primary open-angle glaucoma (POAG in middle-aged and older individuals. In this study, our aim was to demonstrate possible early glaucomatous alterations in young first- and second-degree relatives of POAG patients by spectral-domain optical coherence tomography. A total of 104 participants (52 relatives of POAG patients and 52 healthy individuals were recruited in this cross-sectional study. All the participants were between 17 years and 45 years of age. All eyes underwent testing with spectral-domain optical coherence tomography. Peripapillary retinal nerve fiber layer thickness, hemifield macular thickness, macular ganglion cell complex thickness, posterior pole asymmetry analysis, and retinal arteriolar caliber measurements were taken for comparison between the study and control groups. The mean peripapillary retinal nerve fiber layer thickness was 104.9 ± 8.8 μm in the study group and 105.6 ± 7.4 μm in the control group (p = 0.68. Although whole macular thickness measurements were higher in the control group when compared with the study group (p = 0.008, the macular ganglion cell complex thickness was similar in both groups (p = 0.87. The posterior pole asymmetry analysis revealed no statistically significant difference between the groups in the aspect of consecutive black squares (p = 0.79. The mean retinal arteriolar caliber was 85.9 ± 4.8 μm in the study group and 86.0 ± 5.0 μm in the control group (p = 0.90. In conclusion, young relatives of POAG patients do not show characteristic glaucomatous damage when compared with the controls.

  13. Influence of veneer thickness on residual stress profile in veneering ceramic: measurement by hole-drilling.

    Science.gov (United States)

    Mainjot, Amélie K; Schajer, Gary S; Vanheusden, Alain J; Sadoun, Michaël J

    2012-02-01

    The veneering process of frameworks induces residual stresses and can initiate cracks when combined with functional stresses. The stress distribution within the veneering ceramic as a function of depth is a key factor influencing failure by chipping. This is a well-known problem with Yttria-tetragonal-zirconia-polycrystal based fixed partial dentures. The objective of this study is to investigate the influence of veneer thickness on the stress profile in zirconia- and metal-based structures. The hole-drilling method, often used for engineering measurements, was adapted for use with veneering ceramic. The stress profile was measured in bilayered disc samples of 20 mm diameter, with a 1 mm thick zirconia or metal framework. Different veneering ceramic thicknesses were performed: 1 mm, 1.5 mm, 2 mm, 2.5 mm and 3 mm. All samples exhibited the same type of stress vs. depth profile, starting with compressive at the ceramic surface, decreasing with depth up to 0.5-1.0 mm from the surface, and then becoming compressive again near the framework, except for the 1.5 mm-veneered zirconia samples which exhibited interior tensile stresses. Stresses in the surface of metal samples were not influenced by veneer thickness. Variation of interior stresses at 1.2 mm from the surface in function of veneer thickness was inverted for metal and zirconia samples. Veneer thickness influences in an opposite way the residual stress profile in metal- and in zirconia-based structures. A three-step approach and the hypothesis of the crystalline transformation are discussed to explain the less favorable residual stress development in zirconia samples. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  14. Detecting thermal phase transitions in corneal stroma by fluorescence micro-imaging analysis

    Science.gov (United States)

    Matteini, P.; Rossi, F.; Ratto, F.; Bruno, I.; Nesi, P.; Pini, R.

    2008-02-01

    Thermal modifications induced in corneal stroma were investigated by the use of fluorescence microscopy. Freshly extracted porcine corneas were immersed for 5 minutes in a water bath at temperatures in the 35-90°C range and stored in formalin. The samples were then sliced in 200-μm-thick transversal sections and analyzed under a stereomicroscope to assess corneal shrinkage. Fluorescence images of the thermally treated corneal samples were acquired using a slow-scan cooled CCD camera, after staining the slices with Indocyanine Green (ICG) fluorescent dye which allowed to detect fluorescence signal from the whole tissue. All measurements were performed using an inverted epifluorescence microscope equipped with a mercury lamp. The thermally-induced modifications to the corneal specimens were evaluated by studying the grey level distribution in the fluorescence images. For each acquired image, Discrete Fourier Transform (DFT) and entropy analyses were performed. The spatial distribution of DFT absolute value indicated the spatial orientation of the lamellar planes, while entropy was used to study the image texture, correlated to the stromal structural transitions. As a result, it was possible to indicate a temperature threshold value (62°C) for high thermal damage, resulting in a disorganization of the lamellar planes and in full agreement with the measured temperature for corneal shrinkage onset. Analysis of the image entropy evidenced five strong modifications in stromal architecture at temperatures of ~45°C, 53°C, 57°C, 66°C, 75°C. The proposed procedure proved to be an effective micro-imaging method capable of detecting subtle changes in corneal tissue subjected to thermal treatment.

  15. The Usefulness of Visceral Fat Thickness Measured by Ultrasonography as an Abdominal Obesity Index

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yong Kyun [Dept. of Diagnostic Radiology, Korealife Daejeon Healthcare Center, Daejeon (Korea, Republic of); Han, Man Seok [Dept. of Diagnostic Radiology, Chungnam National University Hospital, Daejeon (Korea, Republic of)

    2008-09-15

    Abdominal obesity with visceral fat accumulation have been known to be intimately associated with the development of metabolic syndrome. Therefore, it is important to estimate the precise amount of visceral fat. Ultrasonography has been reported that it is a simple and noninvasive method for visceral fat evaluation. Purpose of this study is to evaluate the association of ultrasonographic visceral fat thickness, anthropometric indexes, and risk factor of metabolic syndrome, and to investigate the cut-off value of abdominal visceral fat thickness leading to increased risk of metabolic syndrome. The subject included 200 men and 200 women who visited D healthcare center in Daejeon from January to April 2008. The subcutaneous fat thickness and visceral fat thickness were measured by ultrasonograph. As anthropometric index, we measured body mass index, waist circumference and waist/height ratio. As for the risk factor of metabolic syndrome, we measured blood pressure, high density lipoprotein cholesterol, triglyceride and fasting serum glucose. VFT was significantly correlated with waist circumference, (r=0.683/M, r=0.604/F), waist to height ratio (r=0.633/M, r=0.593/F) and BMI (r=0.621/M, r=0.534/F) in both men and women. In addition it was significantly correlated with Systolic blood pressure (r=0.229/M, r=0.232/F), Diastolic blood pressure ((r=0.285/M, r=0.254/F), high density cholesterol (r=-0.254/M, r=-0.254/F), Triglyceride (r=0.475/M, r=0.411/F), and Fasting blood sugar (r=0.158/M, r=0.234/F) in both men and women. The cut-off value of visceral fat thickness leading to the increased risk of metabolic syndrome was 4.58 cm (sensitivity 89.2%, specificity 71.2%) in men and 3.50 cm (sensitivity 61.2% specificity 80.8%) in women respectively. The odds ratio of the risk of metabolic syndrome was dramatically increased with the abdominal visceral fat thickness level over 6 cm in men and 5 cm in women. The visceral fat thickness using ultrasonography was significantly

  16. The Usefulness of Visceral Fat Thickness Measured by Ultrasonography as an Abdominal Obesity Index

    International Nuclear Information System (INIS)

    Kim, Yong Kyun; Han, Man Seok

    2008-01-01

    Abdominal obesity with visceral fat accumulation have been known to be intimately associated with the development of metabolic syndrome. Therefore, it is important to estimate the precise amount of visceral fat. Ultrasonography has been reported that it is a simple and noninvasive method for visceral fat evaluation. Purpose of this study is to evaluate the association of ultrasonographic visceral fat thickness, anthropometric indexes, and risk factor of metabolic syndrome, and to investigate the cut-off value of abdominal visceral fat thickness leading to increased risk of metabolic syndrome. The subject included 200 men and 200 women who visited D healthcare center in Daejeon from January to April 2008. The subcutaneous fat thickness and visceral fat thickness were measured by ultrasonograph. As anthropometric index, we measured body mass index, waist circumference and waist/height ratio. As for the risk factor of metabolic syndrome, we measured blood pressure, high density lipoprotein cholesterol, triglyceride and fasting serum glucose. VFT was significantly correlated with waist circumference, (r=0.683/M, r=0.604/F), waist to height ratio (r=0.633/M, r=0.593/F) and BMI (r=0.621/M, r=0.534/F) in both men and women. In addition it was significantly correlated with Systolic blood pressure (r=0.229/M, r=0.232/F), Diastolic blood pressure ((r=0.285/M, r=0.254/F), high density cholesterol (r=-0.254/M, r=-0.254/F), Triglyceride (r=0.475/M, r=0.411/F), and Fasting blood sugar (r=0.158/M, r=0.234/F) in both men and women. The cut-off value of visceral fat thickness leading to the increased risk of metabolic syndrome was 4.58 cm (sensitivity 89.2%, specificity 71.2%) in men and 3.50 cm (sensitivity 61.2% specificity 80.8%) in women respectively. The odds ratio of the risk of metabolic syndrome was dramatically increased with the abdominal visceral fat thickness level over 6 cm in men and 5 cm in women. The visceral fat thickness using ultrasonography was significantly

  17. Non-contact Measurement of Remaining Thickness of Corroding Superheater Tubes. Phase 1

    Energy Technology Data Exchange (ETDEWEB)

    Borggreen, Kjeld; Storesund, Jan

    2006-10-15

    Corrosion of superheaters has become a severe problem in many biomass boilers and incineration plants. This new situation calls for frequent tube wall thickness testing of the superheaters during very short shut-downs. To meet this demand Electro Magnetic Acoustic Transducer (EMAT) candidates as substitute for conventional manually operated contact UT-transducers. The EMAT can contactlessly generate an ultrasonic wave in the interphase between the external oxide and the metal. This means that measurements can be undertaken much quicker and with a much higher coverage simultaneously, without preceding blast operations. It is the aim of the project to demonstrate the usefulness of two simple EMAT systems, Panametrics and Sonatest, for fast and reliable tube thickness inspections in difficult-to-access superheater sections. The present Phase 1 of the project involves testing of the performance of the two systems in laboratory with the following results: 1. Both instruments work well on plate, tube, and pipe samples assuming the presence of an external oxide layer formed at a temperature above approximately 400 deg C. 2. Both instruments work well on all types of ferritic and martensitic steels but not on austenitic steels. 3. Both instruments work well independent of the thickness of the active oxide layer. 4. Both instruments work well independent of tube diameter, wall thickness, and sample width. 5. Both instruments work well over a very large range of wall thicknesses. Minimum tube wall thickness is less than 1.8 mm. 6. The tolerable lift-off (free distance between transducer and tube surface) is 2.4 - 3.0 mm for Panametrics system and 3.6 - 4.8 mm for Sonatest's system. The tolerable lift-off is a measure of the thickness of ash deposits, which can be tolerated on the tube surface as well as the misplacement, which can be tolerated in case of remote tube testing. 7. The tolerable off-set between tube axis and probe axis is very large for both instruments (10

  18. Ultrasound-based measurement of liquid-layer thickness: A novel time-domain approach

    Science.gov (United States)

    Praher, Bernhard; Steinbichler, Georg

    2017-01-01

    Measuring the thickness of a thin liquid layer between two solid materials is important when the adequate separation of metallic parts by a lubricant film (e.g., in bearings or mechanical seals) is to be assessed. The challenge in using ultrasound-based systems for such measurements is that the signal from the liquid layer is a superposition of multiple reflections. We have developed an algorithm for reconstructing this superimposed signal in the time domain. By comparing simulated and measured signals, the time-of-flight of the ultrasonic pulse in a layer can be estimated. With the longitudinal sound velocity known, the layer thickness can then be calculated. In laboratory measurements, we validate successfully (maximum relative error 4.9%) our algorithm for layer thicknesses ranging from 30 μm to 200 μm. Furthermore, we tested our method in the high-temperature environment of polymer processing by measuring the clearance between screw and barrel in the plasticisation unit of an injection moulding machine. The results of such measurements can indicate (i) the wear status of the tribo-mechanical screw-barrel system and (ii) unsuitable process conditions.

  19. [Epidemiologic study of tear film lipid layer thickness measurement in the population of Taishitun Community in Beijing].

    Science.gov (United States)

    Liang, Q F; Du, X H; Su, Y D; Wang, N L; Wei, Z J; Labbé, Antoine

    2017-07-11

    Objective: To investigate the distribution of tear film lipid layer thickness (LLT) and the relationship between symptoms and signs of dry eye and tear film LLT in the population of Taishitun Community in Beijing. Methods: A cross-sectional study. From May 2016 to August 2016, three streets of Taishitun Community were randomly selected as survey districts and 540 persons were taken as investigation subjects. Every participant completed 6 items of dry eye examinations as follows: questionnaire (Ocular Surface Disease Index, OSDI), measurement of tear film LLT, tear film break-up time (TBUT), corneal and conjunctival staining, SchirmerⅠtest and the infrared meibomian photography. According to their age, all participants were divided into four groups: junior group (analysis and multivariate Logistic regression analysis, distribution of the variables of LLT and the relationship between dry eye symptoms and LLT were studied. Results: A total of 473 residents finally participated in this study, and the response ratio was 87.6%. The values of LLT were normally distributed. The average LLT was (59.87±18.50) nm [(60.16±19.15) nm in males and (59.67±18.57) nm in females], and the comparison of LLT with different genders was not statistically significant ( t= 0.198, P= 0.843). The tear film LLT of four different age groups had statistical significance ( F= 15.092, P0.05. F= 0.538, P >0.05). In the OSDI symptom questionnaire, only blurred vision and decreased visual acuity were related to the tear film LLT ( Pfilm LLT ( P> 0.05). Conclusions: In Taishitun Community of Beijing, the values of tear film LLT had a normal distribution. The LLT was positively correlated with age, but inversely correlated with the severity of the symptoms of dry eye. There was no significant correlation between the LLT and the TBUT, SchirmerⅠtest result and meibomian gland loss rate. (Chin J Ophthalmol, 2017, 53: 495-501) .

  20. Corneal Laceration

    Medline Plus

    Full Text Available ... a very serious injury and requires immediate medical attention to avoid severe vision loss. If your eye ... Feb 13, 2017 How do you measure the size of pannus under a slit lamp? Oct 05, ...

  1. Sea ice thickness measurements collected during the LOMROG 2007 and 2009 expeditions

    DEFF Research Database (Denmark)

    Skourup, Henriette; Forsberg, René; Hanson, Susanne

    and 2009 we have collected a unique data set of late summer sea ice thickness, freeboard height and snow depth from the high Arctic Ocean during the time of the annual minimum sea ice extent. The data were collected by on-the-ground drilling and EM measurements. Here we give a brief overview of the data......According to scientific measurements, the Arctic sea ice extent has declined dramatically over the past thirty years, with the most extreme decline seen in the summer melt season. Other observations indicate that the sea ice has become thinner and perennial ice less widely distributed...... collection, as well as the results including the freeboard-to-sea-ice thickness conversion factor, which is used when interpreting freeboard heights measured by remote sensing....

  2. Simultaneous refractive index and thickness measurement with the transmission interferometric adsorption sensor

    Energy Technology Data Exchange (ETDEWEB)

    Sannomiya, Takumi; Voeroes, Janos [Laboratory of Biosensors and Bioelectronics, Department of Information Technology and Electrical Engineering, ETH Zurich, 8092, Zurich (Switzerland); Balmer, Tobias E [Materials Research Center, ETH Zurich, 8093, Zurich (Switzerland); Heuberger, Manfred, E-mail: sannomiya@biomed.ee.ethz.c, E-mail: tobias.balmer@mat.ethz.c, E-mail: manfred.heuberger@empa.c, E-mail: janos.voros@biomed.ee.ethz.c [Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, 8093, Zurich (Switzerland)

    2010-10-13

    Refractive index and thickness of the adlayer are determined simultaneously using the transmission interferometric adsorption sensor (TInAS). Optical biosensors, where both refractive index and thickness of a homogeneous adlayer (thus the adsorbed mass) are determined simultaneously, so-called model-free biosensors, are important tools to investigate the adsorbed mass of biomolecules with unknown conformation. Our proposed calculation method enables model-free biosensing from a single spectrum acquired by a simple TInAS setup, namely using information of peak/dip positions as well as peak/dip intensities. The feasibility of this method was experimentally tested by adsorbing polyelectrolyte multilayer as well as biomolecules. To validate the new method also for the more intricate heterogeneous adlayer, the apparent refractive index and thickness were assessed theoretically by simulating a selection of different adsorbate configurations with the multiple multipole program (MMP). We found that a lateral inhomogeneity of the adsorbate (e.g. islands or adsorbed colloids) results in correct thickness and in reduced refractive index averaged in proportion to their density while vertically inhomogeneous density caused more complex responses. However, the apparent mass was always correct. Measurement errors can lead to significant errors in the apparent refractive index, particularly when the adlayer is very thin (<5 nm). This model-free TInAS technique would be useful not only for the measurement of adsorbed mass but also for the conformational analysis of the adsorbed molecules.

  3. Measurements of the dependence of damage thresholds on laser wavelength, pulse duration and film thickness

    International Nuclear Information System (INIS)

    Rainer, F.; Vercimak, C.L.; Carniglia, C.K.; Milam, D.; Hart, T.T.

    1985-01-01

    Results of three experiments are described. The authors used 351-nm and 355-nm pulses with durations of 0.6, 1, 5 and 9 ns to measure thresholds for a variety of antireflectance and high reflectance coatings. The functional form t/sup m/, with t the pulse duration, was used to scale fluence thresholds measured at 0.6 ns to those measured at 9.0 ns. Values of the coefficient m ranged from 0.10 to 0.51. The average value was 0.30. In the second experiment, they measured thresholds at 1064 nm, 527 nm and 355 nm for single-frequency high reflectance ZrO/sub 2//SiO/sub 2/ coatings. Coatings for all three frequencies were deposited simultaneously by use of masks in the coating chamber. Thresholds varied from 2-4 J/cm/sup 2/ at 355 nm to 7-10 J/cm/sup 2/ at 1064 nm. The third experiment measured thresholds at 355 nm for antireflection coatings made with layer thicknesses varying from greater than one wavelength to less than a quarterwavelength. A significant variation of threshold with coating thickness was not observed, but the median thresholds increased slightly as coating thickness increased

  4. Terahertz thickness measurements for real industrial applications: from automotive paints to aerospace industry (Conference Presentation)

    Science.gov (United States)

    Krimi, Soufiene; Beigang, René

    2017-02-01

    In this contribution, we present a highly accurate approach for real-time thickness measurements of multilayered coatings using terahertz time domain spectroscopy in reflection geometry. The proposed approach combines the benefits of a model-based material parameters extraction method to calibrate the specimen under test, a generalized modeling method to simulate the terahertz radiation behavior within arbitrary thin films, and the robustness of a powerful evolutionary optimization algorithm to increase the sensitivity and the precision of the minimum thickness measurement limit. Furthermore, a novel self-calibration model is introduced, which takes into consideration the real industrial challenges such as the effect of wet-on-wet spray in the car painting process and the influence of the spraying conditions and the sintering process on ceramic thermal barrier coatings (TBCs) in aircraft industry. In addition, the developed approach enables for some applications the simultaneous determination of the complex refractive index and the coating thickness. Hence, a pre-calibration of the specimen under test is not required for such cases. Due to the high robustness of the self-calibration method and the genetic optimization algorithms, the approach has been successfully applied to resolve individual layer thicknesses within multi-layered coated samples down to less than 10 µm. The regression method can be applied in time-domain, frequency-domain or in both the time and frequency-domain simultaneously. The data evaluation uses general-purpose computing on graphics processing units and thanks to the developed highly parallelized algorithm lasts less than 300 ms. Thus, industrial requirements for fast thickness measurements with an "every-second-cycle" can be fulfilled.

  5. Ultrasonographic evaluation of reproductive tract measures and fat thickness traits in pre-pubertal Nellore heifers

    Directory of Open Access Journals (Sweden)

    Fabio Morato Monteiro

    2012-02-01

    Full Text Available The aim of this study was to evaluate the relationship between reproductive tract and fat thickness measures obtained by ultrasound in prepubertal Nellore heifers. A total of 128 Nellore heifers born in 2006 and 2007 were submitted to ultrasound evaluations (13, 16, 19 and 22 months of age of reproductive tract measures and fat thickness traits. These animals were from a selection experiment (NeC: control line, and NeS: selection line for yearling weight started in 1981. Mean values of ovary area, height of the right uterine horn (HU, maximum follicular diameter (FOL, backfat thickness (BF, rump fat thickness (RF, and body condition score were analyzed. Repeated records were modeled using the PROC MIXED procedure (SAS, fitting a model that included the selection line, year of birth, measurement as fixed effects, and interactions. Body weight differed between the selected (281.48 kg and control (210.51 kg lines. Only the least square means of FOL were lower in the NeC line compared to the NeS line (P < 0.05, although the difference in mean HU between the two lines was of only borderline significance (P = 0.06. The rate of growth for the three reproductive traits was similar in the two lines. Simple and residual correlations between the reproductive and subcutaneous fat traits ranged from low to medium. The highest correlations were observed between HU and RF (Pearson correlation = 0.71 and residual correlation = 0.34. The current results are consistent with the literature, indicating that fat thickness traits are not good predictors of prepubertal reproductive traits in heifers. Further studies are necessary to clarify the relationship between reproduction and body fat in Nellore heifers.

  6. Measurement of Choroidal Perfusion and Thickness Following Systemic Sildenafil (Viagra®)

    Science.gov (United States)

    Kim, David Y.; Silverman, Ronald H.; Chan, R.V. Paul; Khanifar, Aziz A.; Rondeau, Mark; Lloyd, Harriet; Schlegel, Peter; Coleman, D. Jackson

    2011-01-01

    Objective To demonstrate anatomic and physiologic changes in the human choroid following systemic sildenafil citrate (ViagraR) using enhanced depth imaging spectral domain-optical coherence tomography (EDI-OCT) and swept-scan high frequency digital ultrasound. Methods Seven healthy male subjects (mean age 32.7 years) were evaluated at baseline and two hours after ingesting 50 mg of sildenafil. Swept-scan high frequency digital ultrasound and EDI-OCT were utilized to measure choroidal perfusion and thickness, respectively. Results were read by masked observers. The Wilcoxon signed-rank test and t-test were used to analyze differences in choroidal flow and thickness at baseline and two hours after ingestion of sildenafil. Results Two hours following sildenafil, increased choroidal perfusion was observed in 11 of 12 eyes measured by swept-scan high frequency digital ultrasound. The mean increase was 3.46 (±2.00) times baseline with a range of 0.47 to 7.80 times baseline (p=0.004). Increased choroidal thickness was observed in 12 of 12 eyes measured with EDI-OCT. The average choroidal thickness increased by 11.6% temporal to the fovea, 9.3% nasal to the fovea, and 10.7% underneath the fovea (p<0.001 for all values). Conclusions Choroidal perfusion and thickness both increase in response to systemic sildenafil. These changes could secondarily affect retinal function, explain previously reported clinical symptoms, and potentially be a useful adjunct for treatment of ocular diseases that would benefit from increased choroidal blood flow. PMID:22974308

  7. Goldmann applanation tonometry compared with corneal-compensated intraocular pressure in the evaluation of primary open-angle Glaucoma

    Directory of Open Access Journals (Sweden)

    Ehrlich Joshua R

    2012-09-01

    Full Text Available Abstract Background To better understand the role of corneal properties and intraocular pressure (IOP in the evaluation of primary open-angle glaucoma (POAG; and to determine the feasibility of identifying glaucomatous optic neuropathy (GON using IOP corrected and uncorrected for corneal biomechanics. Methods Records from 1,875 eyes of consecutively evaluated new patients were reviewed. Eyes were excluded if central corneal thickness (CCT or Ocular Response Analyzer (ORA measurements were unavailable. Presence or absence of GON was determined based on morphology of the optic disc, rim and retinal nerve fiber layer at the time of clinical examination, fundus photography and Heidelberg Retinal Tomography. Goldmann-applanation tonometry (GAT in the untreated state was recorded and Goldmann-correlated (IOPg and corneal-compensated IOP (IOPcc were obtained using the ORA. Glaucomatous eyes were classified as normal or high-tension (NTG, HTG using the conventional cutoff of 21 mm Hg. One eligible eye was randomly selected from each patient for inclusion. Results A total of 357 normal, 155 HTG and 102 NTG eyes were included. Among NTG eyes, IOPcc was greater than GAT (19.8 and 14.4 mm Hg; p  Conclusions IOPcc may account for measurement error induced by corneal biomechanics. Compared to GAT, IOPcc may be a superior test in the evaluation of glaucoma but is unlikely to represent an effective diagnostic test.

  8. Novel method for the measurement of liquid film thickness during fuel spray impingement on surfaces.

    Science.gov (United States)

    Henkel, S; Beyrau, F; Hardalupas, Y; Taylor, A M K P

    2016-02-08

    This paper describes the development and application of a novel optical technique for the measurement of liquid film thickness formed on surfaces during the impingement of automotive fuel sprays. The technique makes use of the change of the light scattering characteristics of a metal surface with known roughness, when liquid is deposited. Important advantages of the technique over previously established methods are the ability to measure the time-dependent spatial distribution of the liquid film without a need to add a fluorescent tracer to the liquid, while the measurement principle is not influenced by changes of the pressure and temperature of the liquid or the surrounding gas phase. Also, there is no need for non-fluorescing surrogate fuels. However, an in situ calibration of the dependence of signal intensity on liquid film thickness is required. The developed method can be applied to measure the time-dependent and two-dimensional distribution of the liquid fuel film thickness on the piston or the liner of gasoline direct injection (GDI) engines. The applicability of this technique was evaluated with impinging sprays of several linear alkanes and alcohols with different thermo-physical properties. The surface temperature of the impingement plate was controlled to simulate the range of piston surface temperatures inside a GDI engine. Two sets of liquid film thickness measurements were obtained. During the first set, the surface temperature of the plate was kept constant, while the spray of different fuels interacted with the surface. In the second set, the plate temperature was adjusted to match the boiling temperature of each fuel. In this way, the influence of the surface temperature on the liquid film created by the spray of different fuels and their evaporation characteristics could be demonstrated.

  9. Chest wall thickness measurements and the dosimetric implications for male workers in the uranium industry

    International Nuclear Information System (INIS)

    Kramer, Gary H.; Hauck, Barry M.; Allen, Steve A.

    2000-01-01

    The Human Monitoring Laboratory has measured the chest wall thickness and adipose mass fraction of a group of workers at three Canadian uranium refinery, conversion plant, and fuel fabrication sites using ultrasound. A site specific biometric equation has been developed for these workers, who seem to be somewhat larger than other workers reported in the literature. The average chest wall thickness of the seated persons measured at the uranium conversion plant and refinery was about 3.8 cm, and at the fuel fabrication facility was 3.4 cm. These values are not statistically different. Persons measured in a seated geometry had a thinner chest wall thickness than persons measured in a supine geometry - the decrease was in the range of 0.3 cm to 0.5 cm. It follows that a seated geometry will give a lower MDA (or decision level) than a supine geometry. Chest wall thickness is a very important modifier for lung counting efficiency and this data has been put into the perspective of the impending Canadian dose limits that will reduce the limit of occupationally exposed workers to essentially 20 mSv per year. Natural uranium must be measured based on the 235 U emissions at these type of facilities. The refining and conversion process removes 234 Th and the equilibrium is disturbed. This is unfortunate as the MDA values for this nuclide are approximately a factor of three lower than the values quoted below. The sensitivity of the germanium and phoswich based lung counting system has been compared. Achievable MDA's (30 minute counting time) with a four-phoswich-detector array lie in the range of 4.7 mg to 13.5 mg of natural uranium based on the 235 U emissions over a range of chest wall thicknesses of 1.6 cm to 6.0 cm. The average achievable MDA is about 8.5 mg which can be reduced to about 6.2 mg by doubling the counting time. Similarly, MDA's (30 minute counting time) obtainable with a germanium lung counting system will lie in the range of 3 mg to 28 mg of natural uranium

  10. A reliable control system for measurement on film thickness in copper chemical mechanical planarization system

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hongkai; Qu, Zilian; Zhao, Qian; Tian, Fangxin; Zhao, Dewen; Meng, Yonggang; Lu, Xinchun [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China)

    2013-12-15

    In recent years, a variety of film thickness measurement techniques for copper chemical mechanical planarization (CMP) are subsequently proposed. In this paper, the eddy-current technique is used. In the control system of the CMP tool developed in the State Key Laboratory of Tribology, there are in situ module and off-line module for measurement subsystem. The in situ module can get the thickness of copper film on wafer surface in real time, and accurately judge when the CMP process should stop. This is called end-point detection. The off-line module is used for multi-points measurement after CMP process, in order to know the thickness of remained copper film. The whole control system is structured with two levels, and the physical connection between the upper and the lower is achieved by the industrial Ethernet. The process flow includes calibration and measurement, and there are different algorithms for two modules. In the process of software development, C++ is chosen as the programming language, in combination with Qt OpenSource to design two modules’ GUI and OPC technology to implement the communication between the two levels. In addition, the drawing function is developed relying on Matlab, enriching the software functions of the off-line module. The result shows that the control system is running stably after repeated tests and practical operations for a long time.

  11. Residual stress measurements in thick structural weldments by means of neutron diffraction

    International Nuclear Information System (INIS)

    Ohms, C.; Youtsos, A.G.; Idsert, P. v.d.; Timke, T.

    2000-01-01

    Welding residual stresses in large structural components are a major concern with respect to their performance and lifetime. In large structures reasonable thermal stress relief treatment is usually impossible due to the component size. On the other hand, prediction of welding stresses by numerical modelling has not yet proven to be generally reliable, while the experimental determination of such stresses remains a demanding task. At the high flux reactor (HFR), Petten, a new residual stress diffractometer has been installed recently capable of handling of components up to 1000 kg - the large component neutron diffraction facility (LCNDF). It has facilitated residual stress measurements in two large welded components, of which results are presented here. The first component represents a bi-metallic weld in form of a pipe of 25 mm wall thickness. Three dimensional measurements of residual stress are discussed in detail. The second specimen is a 66 mm wall thickness austenitic steel nuclear piping weld. Results on relief of strain within the weld through post weld heat treatment (PWHT) are presented. Additionally results obtained earlier at former CRNL (CAN) on a section of a thick nuclear piping weld are presented in order to illustrate the variation in the reference lattice parameter trough the weld and the heat affected zone (HAZ). These results clearly show the necessity to determine the reference parameters for each location in all measurement directions by means of measurements in small coupons free of macro-stresses. (orig.)

  12. The relationship between corneal biomechanical properties and confocal microscopy findings in normal and keratoconic eyes.

    Science.gov (United States)

    Hurmeric, Volkan; Sahin, Afsun; Ozge, Gokhan; Bayer, Atilla

    2010-06-01

    To investigate the relationship between corneal biomechanical properties and confocal microscopy (CM) findings in normal and keratoconic eyes. The study consisted of 28 eyes of 28 healthy volunteers and 23 eyes of 15 patients with keratoconus. The diagnosis of keratoconus was made with corneal topography and clinical findings. The corneal hysteresis (CH) and corneal resistance factor (CRF) were measured by the ocular response analyzer. In vivo CM was performed with NIDEK Confoscan 3. CH and CRF were compared with corneal morphological findings (detailed cell counts of endothelial, stromal, and epithelial cells) in vivo. CH was 10.1 +/- 1.3 mm Hg in normal eyes and 7.4 +/- 1.5 mm Hg in keratoconic eyes (P < 0.0001). CRF was 10.1 +/- 1.8 mm Hg in normal eyes and 6.2 +/- 1.4 mm Hg in keratoconic eyes (P < 0.0001). CH and CRF were negatively correlated with full-thickness stromal keratocyte density (P < 0.01; r = -0.52 and P < 0.001; r = -0.67, respectively) in healthy eyes. Keratocyte density of the posterior half of the stroma was found to be significantly related with CRF in healthy eyes (beta = -0.404; P = 0.01). There was no significant relationship among CH, CRF, and CM findings in eyes with keratoconus. There is a significant relationship between CRF and keratocyte density of the posterior half of the stroma in healthy eyes. Our results suggest that corneal elasticity is related to not only stromal matrix but also cellular structure of the cornea.

  13. Computed tomographic measurement of gluteal subcutaneous fat thickness in reference to failure of gluteal intramuscular injections

    Energy Technology Data Exchange (ETDEWEB)

    Burbridge, B.E. [Univ. of Saskatchewan, Royal Univ. Hospital, Academic Dept. of Medical Imaging, Saskatoon, Saskatchewan (Canada)]. E-mail: brent.burbridge@usask.ca

    2007-04-15

    Casual observation of gluteal region fat thickness on computed tomography (CT) of the pelvis leads to the hypothesis that, in some individuals intended intramuscular injections are not properly deposited in the gluteal muscle. We gathered and analyzed data to determine whether this hypothesis was true. CT scans of the pelvis were analyzed over an 18-day period in the tall of 2005. The thickness of gluteal region subcutaneous fat was measured in a standardized manner. Measurement of gluteal region subcutaneous fat thickness was performed for 298 pelvic CT scans. There were 150 male subjects and 148 female subjects. The average gluteal fat thickness for female subjects was 33.2 mm, whereas the average for male subjects was 23.1 mm. Analysis revealed a significant difference in gluteal region fat thickness between male and female subjects. A 37-mm needle, allowing for 6-mm penetration of the gluteal muscle, would not have entered the gluteal muscle fibres in 81 of 148 female subjects (54.7%), in 21 of 150 male subjects (14%), and in 102 of the 298 total sample (34.2%). Analysis revealed a significant difference between male and female subjects with regard to gluteal muscle needle penetration. An overall predicted failure rate of 34% was identified for intended gluteal intramuscular injections when the standard technique was used. This is important information for care providers who inject medications in the gluteal region. In a significant number of patients, the medications will be injected subcutaneously and not into the gluteal musculature, possibly altering the pharmacokinetics of the administered medication. An alternative injection site should probably be chosen to increase the success rate of intramuscular deposition of medications and vaccines in unselected adults. (author)

  14. Comparison of different methods for measuring the passive film thickness on metals

    International Nuclear Information System (INIS)

    Benoit, Marie; Bataillon, Christian; Gwinner, Benoit; Miserque, Frédéric; Orazem, Mark E.; Sánchez-Sánchez, Carlos M.; Tribollet, Bernard; Vivier, Vincent

    2016-01-01

    Highlights: • In situ EIS and ex situ XPS were used for the characterization of zirconium oxide films. • The film thicknesses can be obtained from the analysis of a single EIS diagram. • A convenient graphical method to extract film properties is proposed. - Abstract: In situ electrochemical impedance spectroscopy (EIS) and ex situ X-ray photoelectron spectroscopy (XPS) measurements on electrogenerated zirconium oxide films on zirconium (Zr/ZrO_2) were used to quantify the oxide film thickness and resistivity profiles through the oxide. The EIS analysis presented here takes advantage of the high-frequency domain at which the constant-phase element (CPE) behavior of the oxide film reverts to a capacitive response and the Cole-Cole representations of the complex capacitance to extract the high-frequency capacitance of the oxide film without reference to the nature of the time-constant distribution within the oxide film. The film thickness of the ZrO_2 samples measured from the high-frequency capacitance of EIS were in good agreement with the thickness obtained from XPS. Moreover, the EIS analysis presented is based on the use of the integral solution of the power law model, which allows to obtain in one single EIS experiment, both the film thickness and the resistivity profile in the ZrO_2 film. This work suggests a convenient graphical method to extract film properties and serves to validate a key assumption of the power-law model for interpretation of CPE parameters in terms of physical properties.

  15. Measurement of resonances in 12 C + 4 He through inverse kinematics with thick targets

    International Nuclear Information System (INIS)

    Aguilera, E.F.; Lizcano, D.; Martinez Q, E.; Fernandez, M.C.; Murillo, G.; Goldberg, V.; Skorodumov, B.B.; Rogachev, G.

    2003-01-01

    The excitation function of elastic scattering for the system 12 C + 4 He to energy from 0.5 to 3.5 MeV in the center of mass system (c.m.) was measured. We use a gassy thick target and the technique of inverse kinematics which allows to make measurements at 180 degrees in c.m. Using the R matrix theory those was deduced parameters of the resonances and the results were compared with measurements reported in the literature made with other techniques. (Author)

  16. Highly accurate thickness measurement of multi-layered automotive paints using terahertz technology

    Science.gov (United States)

    Krimi, Soufiene; Klier, Jens; Jonuscheit, Joachim; von Freymann, Georg; Urbansky, Ralph; Beigang, René

    2016-07-01

    In this contribution, we present a highly accurate approach for thickness measurements of multi-layered automotive paints using terahertz time domain spectroscopy in reflection geometry. The proposed method combines the benefits of a model-based material parameters extraction method to calibrate the paint coatings, a generalized Rouard's method to simulate the terahertz radiation behavior within arbitrary thin films, and the robustness of a powerful evolutionary optimization algorithm to increase the sensitivity of the minimum thickness measurement limit. Within the framework of this work, a self-calibration model is introduced, which takes into consideration the real industrial challenges such as the effect of wet-on-wet spray in the painting process.

  17. Highly accurate thickness measurement of multi-layered automotive paints using terahertz technology

    International Nuclear Information System (INIS)

    Krimi, Soufiene; Beigang, René; Klier, Jens; Jonuscheit, Joachim; Freymann, Georg von; Urbansky, Ralph

    2016-01-01

    In this contribution, we present a highly accurate approach for thickness measurements of multi-layered automotive paints using terahertz time domain spectroscopy in reflection geometry. The proposed method combines the benefits of a model-based material parameters extraction method to calibrate the paint coatings, a generalized Rouard's method to simulate the terahertz radiation behavior within arbitrary thin films, and the robustness of a powerful evolutionary optimization algorithm to increase the sensitivity of the minimum thickness measurement limit. Within the framework of this work, a self-calibration model is introduced, which takes into consideration the real industrial challenges such as the effect of wet-on-wet spray in the painting process.

  18. Simultaneous reflectometry and interferometry for measuring thin-film thickness and curvature

    Science.gov (United States)

    Arends, A. A.; Germain, T. M.; Owens, J. F.; Putnam, S. A.

    2018-05-01

    A coupled reflectometer-interferometer apparatus is described for thin-film thickness and curvature characterization in the three-phase contact line region of evaporating fluids. Validation reflectometry studies are provided for Au, Ge, and Si substrates and thin-film coatings of SiO2 and hydrogel/Ti/SiO2. For interferometry, liquid/air and solid/air interferences are studied, where the solid/air samples consisted of glass/air/glass wedges, cylindrical lenses, and molded polydimethylsiloxane lenses. The liquid/air studies are based on steady-state evaporation experiments of water and isooctane on Si and SiO2/Ti/SiO2 wafers. The liquid thin-films facilitate characterization of both (i) the nano-scale thickness of the absorbed fluid layer and (ii) the macro-scale liquid meniscus thickness, curvature, and curvature gradient profiles. For our validation studies with commercial lenses, the apparatus is shown to measure thickness profiles within 4.1%-10.8% error.

  19. Refinement of Out of Circularity and Thickness Measurements of a Cylinder for Finite Element Analysis

    Science.gov (United States)

    2016-09-01

    refined finite element model. Note that the longitudinal seam weld at θ = 0° (= 360°) runs along the green area and through the centre of the red...Longitudinal seam weld is a theta = 0/360 deg UNCLASSIFIED DST-Group-TN-1521 UNCLASSIFIED 7 Figure 2. Example of thickness distribution in the... weld seam at 0° is clearly evident. Inspection of similar graphs for all sections indicates similarly good comparison between the measured and

  20. Measurement of thickness of thin water film in two-phase flow by capacitance method

    International Nuclear Information System (INIS)

    Sun, R.K.; Kolbe, W.F.; Leskovar, B.; Turko, B.

    1981-09-01

    A technique has been developed for measuring water film thickness in a two-phase annular flow system by the capacitance method. An experimental model of the flow system with two types of electrodes mounted on the inner wall of a cylindrical tube has been constructed and evaluated. The apparatus and its ability to observe fluctuations and wave motions of the water film passing over the electrodes is described in some detail

  1. SU-E-I-53: Variation in Measurements of Breast Skin Thickness Obtained Using Different Imaging Modalities

    International Nuclear Information System (INIS)

    Nguyen, U; Kumaraswamy, N; Markey, M

    2014-01-01

    Purpose: To investigate variation in measurements of breast skin thickness obtained using different imaging modalities, including mammography, computed tomography (CT), ultrasound, and magnetic resonance imaging (MRI). Methods: Breast skin thicknesses as measured by mammography, CT, ultrasound, and MRI were compared. Mammographic measurements of skin thickness were obtained from published studies that utilized standard positioning (upright) and compression. CT measurements of skin thickness were obtained from a published study of a prototype breast CT scanner in which the women were in the prone position and the breast was uncompressed. Dermatological ultrasound exams of the breast skin were conducted at our institution, with the subjects in the upright position and the breast uncompressed. Breast skin thickness was calculated from breast MRI exams at our institution, with the patient in the prone position and the breast uncompressed. Results: T tests for independent samples demonstrated significant differences in the mean breast skin thickness as measured by different imaging modalities. Repeated measures ANOVA revealed significant differences in breast skin thickness across different quadrants of the breast for some modalities. Conclusion: The measurement of breast skin thickness is significantly different across different imaging modalities. Differences in the amount of compression and differences in patient positioning are possible reasons why measurements of breast skin thickness vary by modality

  2. Automated Measurement of Tear Film Dynamics and Lipid Layer Thickness for Assessment of Non-Sjögren Dry Eye Syndrome With Meibomian Gland Dysfunction.

    Science.gov (United States)

    Ji, Yong Woo; Lee, Jeihoon; Lee, Hun; Seo, Kyoung Yul; Kim, Eung Kweon; Kim, Tae-Im

    2017-02-01

    To investigate automated values from an advanced corneal topographer with a built-in real keratometer, color camera, and ocular surface interferometer for the evaluation of non-Sjögren dry eye syndrome (NSDES) with meibomian gland dysfunction (MGD). Sixty-four patients (64 eyes) diagnosed with NSDES with MGD were enrolled. All eyes were evaluated using the Ocular Surface Disease Index (OSDI), fluorescence staining score, tear film breakup time (TBUT), Schirmer test, and MGD grade. Noninvasive Keratograph average tear film breakup time (NIKBUTav), tear meniscus height (TMHk), meibomian gland (MG) dropout grade, and lipid layer thickness (LLT) using interferometry were measured. Among automated indexes, NIKBUTav (mean 7.68 ± 4.07 s) and the MG dropout grade (mean 1.0 ± 0.5) significantly correlated with the OSDI (mean 40.6 ± 22.9) (r = -0.337, P = 0.006; and r = 0.201, P = 0.023, respectively), as did all conventional indicators, except the Schirmer score (mean 9.1 ± 5.9 mm). TMHk (mean 0.21 ± 0.18 mm) had significant correlation with the Schirmer score, the staining score (mean 1.2 ± 0.7), TBUT (mean 3.8 ± 1.8 s), and NIKBUTav (r = 0.298, P = 0.007; r = -0.268, P = 0.016; r = 0.459, P < 0.001; and r = 0.439, P < 0.001, respectively), but not any MGD indicator, even the MG dropout grade. NIKBUTav showed significant correlations with all clinical parameters and other automated values, except the Schirmer score and LLT (mean 83.94 ± 20.82 nm) (all (Equation is included in full-text article.)≥ 0.25 and P < 0.01). The MG dropout grade highly correlated with all indexes except TMHk (all (Equation is included in full-text article.)≥ 0.25 and P < 0.05). LLT was significantly associated with TBUT, MGD grade (mean 2.0 ± 0.7), and MG dropout grade (r = 0.219, P = 0.047; r = -0.221, P = 0.039; and r = 0.433, P < 0.001, respectively), although it was not related to patient symptoms. Automated noninvasive measurements using an advanced corneal topographer and LLT

  3. Semi-automated Digital Imaging and Processing System for Measuring Lake Ice Thickness

    Science.gov (United States)

    Singh, Preetpal

    Canada is home to thousands of freshwater lakes and rivers. Apart from being sources of infinite natural beauty, rivers and lakes are an important source of water, food and transportation. The northern hemisphere of Canada experiences extreme cold temperatures in the winter resulting in a freeze up of regional lakes and rivers. Frozen lakes and rivers tend to offer unique opportunities in terms of wildlife harvesting and winter transportation. Ice roads built on frozen rivers and lakes are vital supply lines for industrial operations in the remote north. Monitoring the ice freeze-up and break-up dates annually can help predict regional climatic changes. Lake ice impacts a variety of physical, ecological and economic processes. The construction and maintenance of a winter road can cost millions of dollars annually. A good understanding of ice mechanics is required to build and deem an ice road safe. A crucial factor in calculating load bearing capacity of ice sheets is the thickness of ice. Construction costs are mainly attributed to producing and maintaining a specific thickness and density of ice that can support different loads. Climate change is leading to warmer temperatures causing the ice to thin faster. At a certain point, a winter road may not be thick enough to support travel and transportation. There is considerable interest in monitoring winter road conditions given the high construction and maintenance costs involved. Remote sensing technologies such as Synthetic Aperture Radar have been successfully utilized to study the extent of ice covers and record freeze-up and break-up dates of ice on lakes and rivers across the north. Ice road builders often used Ultrasound equipment to measure ice thickness. However, an automated monitoring system, based on machine vision and image processing technology, which can measure ice thickness on lakes has not been thought of. Machine vision and image processing techniques have successfully been used in manufacturing

  4. Human Chorioretinal Layer Thicknesses Measured in Macula-wide, High-Resolution Histologic Sections

    Science.gov (United States)

    Messinger, Jeffrey D.; Sloan, Kenneth R.; Mitra, Arnab; McGwin, Gerald; Spaide, Richard F.

    2011-01-01

    Purpose. To provide a comprehensive description of chorioretinal layer thicknesses in the normal human macula, including two-layer pairs that can produce a combined signal in some optical coherence tomography (OCT) devices (ganglion cell [GCL] and inner plexiform [IPL] layers and outer plexiform [OPL] and outer nuclear [ONL] layers). Methods. In 0.8-μm-thick, macula-wide sections through the foveola of 18 donors (age range, 40–92 years), 21 layers were measured at 25 locations by a trained observer and validated by a second observer. Tissue volume changes were assessed by comparing total retinal thickness in ex vivo OCT and in sections. Results. Median tissue shrinkage was 14.5% overall and 29% in the fovea. Histologic laminar boundaries resembled those in SD-OCT scans, but the shapes of the foveolar OPL and ONL differed. Histologic GCL, IPL, and OPLHenle were thickest at 0.8. to 1, 1.5, and 0.4 mm eccentricity, respectively. ONL was thickest in an inward bulge at the foveal center. At 1 mm eccentricity, GCL, INL, and OPLHenle represented 17.3% to 21.1%, 18.0% to 18.5%, and 14.2% to 16.6% of total retinal thickness, respectively. In donors ≥70 years of age, the RPE and choroid were 17.1% and 29.6% thinner and OPLHenle was 20.8% thicker than in donors macula were generated. Newer OCT systems can separate GCL from IPL and OPLHenle from ONL, with good agreement for the proportion of retinal thickness occupied by OPLHenle in OCT and histology. The thickening of OPLHenle in older eyes may reflect Müller cell hypertrophy associated with rod loss. PMID:21421869

  5. Comparisons of Soft Tissue Thickness Measurements in Adult Patients With Various Vertical Patterns

    Directory of Open Access Journals (Sweden)

    Neslihan Seyhan Cezairli

    2017-08-01

    Full Text Available Objective: The purposes of this study were to evaluate to study soft tissue facial profile among the different vertical patterns using the Holdaway analysis and the soft tissue thickness measurements. Materials and Methods: The study sample consisted of 90 patients divided into 3 groups: low angle group (30 patients; mean age, 20.38±3.76 years, normal angle group (30 patients; mean age, 19.36±2.83 years and high angle group (30 patients; mean age, 19.44±2.14 years. The study sample, comprised a total of 90 patients (54 women and 36 men divided into low-angle, normal-angle and high angle groups based on vertical growth pattern using the SN/GoGn angle (high-angle group >37°; low-angle group <27°; and control group or normal angle group 27-37°. Facial soft-tissue thickness and Holdaway measurements were analyzed on each radiograph with Image J programme. One-way analysis of variance and post-hoc test (Tukey were used to compare Holdaway measurements and soft tissue thicknesses among the three groups. Results: Significant differences among vertical patterns were observed for the ‘gnathion’, ‘menton’, ‘stomion’ and ‘inferior sulcus to H line’ when both genders were combined. These measurements were thinner in the high-angle group. Significant differences among vertical patterns were observed for ‘gnathion’ and ‘lower lip to H line’ in women; for ‘stomion’ and ‘nose prominence’ in men when examined separately. Conclusion: Facial soft tissue measurements except some for in high angle group were thinner than in low angle group. All soft tissue measurements were greater except for gnathion in low angle group in men than in women.

  6. Optical instrument for measurement of vaginal coating thickness by drug delivery formulations

    International Nuclear Information System (INIS)

    Henderson, Marcus H.; Peters, Jennifer J.; Walmer, David K.; Couchman, Grace M.; Katz, David F.

    2005-01-01

    An optical device has been developed for imaging the human vaginal epithelial surfaces, and quantitatively measuring distributions of coating thickness of drug delivery formulations - such as gels - applied for prophylaxis, contraception or therapy. The device consists of a rigid endoscope contained within a 27-mm-diam hollow, polished-transparent polycarbonate tube (150 mm long) with a hemispherical cap. Illumination is from a xenon arc. The device is inserted into, and remains stationary within the vagina. A custom gearing mechanism moves the endoscope relative to the tube, so that it views epithelial surfaces immediately apposing its outer surface (i.e., 150 mm long by 360 deg. azimuthal angle). Thus, with the tube fixed relative to the vagina, the endoscope sites local regions at distinct and measurable locations that span the vaginal epithelium. The returning light path is split between a video camera and photomultiplier. Excitation and emission filters in the light path enable measurement of fluorescence of the sited region. Thus, the instrument captures video images simultaneously with photometric measurement of fluorescence of each video field [∼10 mm diameter; formulations are labeled with 0.1% w/w United States Pharmacoepia (USP) injectable sodium fluorescein]. Position, time and fluorescence measurements are continuously displayed (on video) and recorded (to a computer database). The photomultiplier output is digitized to quantify fluorescence of the endoscope field of view. Quantification of the thickness of formulation coating of a surface sited by the device is achieved due to the linear relationship between thickness and fluorescence intensity for biologically relevant thin layers (of the order of 0.5 mm). Summary measures of coating have been developed, focusing upon extent, location and uniformity. The device has begun to be applied in human studies of model formulations for prophylaxis against infection with HIV and other sexually transmitted

  7. Abdominal fat thickness measurement using Focused Impedance Method (FIM) - phantom study

    Science.gov (United States)

    Haowlader, Salahuddin; Baig, Tanveer Noor; Siddique-e Rabbani, K.

    2010-04-01

    Abdominal fat thickness is a risk indicator of heart diseases, diabetes, etc., and its measurement is therefore important from the point of view of preventive care. Tetrapolar electrical impedance measurements (TPIM) could offer a simple and low cost alternative for such measurement compared to conventional techniques using CT scan and MRI, and has been tried by different groups. Focused Impedance Method (FIM) appears attractive as it can give localised information. An intuitive physical model was developed and experimental work was performed on a phantom designed to simulate abdominal subcutaneous fat layer in a body. TPIM measurements were performed with varying electrode separations. For small separations of current and potential electrodes, the measured impedance changed little, but started to decrease sharply beyond a certain separation, eventually diminishing gradually to negligible values. The finding could be explained using the intuitive physical model and gives an important practical information. TPIM and FIM may be useful for measurement of SFL thickness only if the electrode separations are within a certain specific range, and will fail to give reliable results if beyond this range. Further work, both analytical and experimental, are needed to establish this technique on a sound footing.

  8. Comparison of corneal power, astigmatism, and wavefront aberration measurements obtained by a point-source color light-emitting diode-based topographer, a Placido-disk topographer, and a combined Placido and dual Scheimpflug device.

    Science.gov (United States)

    Ventura, Bruna V; Wang, Li; Ali, Shazia F; Koch, Douglas D; Weikert, Mitchell P

    2015-08-01

    To evaluate and compare the performance of a point-source color light-emitting diode (LED)-based topographer (color-LED) in measuring anterior corneal power and aberrations with that of a Placido-disk topographer and a combined Placido and dual Scheimpflug device. Cullen Eye Institute, Baylor College of Medicine, Houston, Texas USA. Retrospective observational case series. Normal eyes and post-refractive-surgery eyes were consecutively measured using color-LED, Placido, and dual-Scheimpflug devices. The main outcome measures were anterior corneal power, astigmatism, and higher-order aberrations (HOAs) (6.0 mm pupil), which were compared using the t test. There were no statistically significant differences in corneal power measurements in normal and post-refractive surgery eyes and in astigmatism magnitude in post-refractive surgery eyes between the color-LED device and Placido or dual Scheimpflug devices (all P > .05). In normal eyes, there were no statistically significant differences in 3rd-order coma and 4th-order spherical aberration between the color-LED and Placido devices and in HOA root mean square, 3rd-order coma, 3rd-order trefoil, 4th-order spherical aberration, and 4th-order secondary astigmatism between the color-LED and dual Scheimpflug devices (all P > .05). In post-refractive surgery eyes, the color-LED device agreed with the Placido and dual-Scheimpflug devices regarding 3rd-order coma and 4th-order spherical aberration (all P > .05). In normal and post-refractive surgery eyes, all 3 devices were comparable with respect to corneal power. The agreement in corneal aberrations varied. Drs. Wang, Koch, and Weikert are consultants to Ziemer Ophthalmic Systems AG. Dr. Koch is a consultant to Abbott Medical Optics, Inc., Alcon Surgical, Inc., and i-Optics Corp. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  9. Measurement of the thickness of the urethrovaginal space in women with or without vaginal orgasm.

    Science.gov (United States)

    Gravina, Giovanni Luca; Brandetti, Fulvia; Martini, Paolo; Carosa, Eleonora; Di Stasi, Savino M; Morano, Susanna; Lenzi, Andrea; Jannini, Emmanuele A

    2008-03-01

    The physiology and anatomy of female sexual function are poorly understood. The differences in sexual function among women may be partly attributed to anatomical factors. The purpose of this study was to use ultrasonography to evaluate the anatomical variability of the urethrovaginal space in women with and without vaginal orgasm. Twenty healthy, neurologically intact volunteers were recruited from a population of women who were a part of a previous published study. All women underwent a complete urodynamic evaluation and those with clinical and urodynamic urinary incontinence, idiopathic detrusor overactivity, or micturition disorders, as well as postmenopausal women and those with sexual dysfunction were excluded. The reported experience of vaginal orgasm was investigated. The urethrovaginal space thickness as measured by ultrasound was chosen as the indicator of urogenital anatomical variability. Designated evaluators carried out the measurements in a blinded fashion. The urethrovaginal space and distal, middle, and proximal urethrovaginal segments were thinner in women without vaginal orgasm. A direct correlation between the presence of vaginal orgasm and the thickness of urethrovaginal space was found. Women with a thicker urethrovaginal space were more likely to experience vaginal orgasm (r = 0.884; P = 0.015). A direct and significant correlation between the thickness of each urethrovaginal segment and the presence of vaginal orgasm was found, with the best correlation observed for the distal segment (r = 0.863; P orgasm.

  10. Reproducibility of sonographic measurement of thickness and echogenicity of the plantar fascia.

    Science.gov (United States)

    Cheng, Ju-Wen; Tsai, Wen-Chung; Yu, Tung-Yang; Huang, Kuo-Yao

    2012-01-01

    To evaluate the intra- and interrater reliability of ultrasonographic measurements of the thickness and echogenicity of the plantar fascia. Eleven patients (20 feet), who complained of inferior heel pain, and 26 volunteers (52 feet) were enrolled. Two sonographers independently imaged the plantar fascia in both longitudinal and transverse planes. Volunteers were assessed twice to evaluate intrarater reliability. Quantitative evaluation of the echogenicity of the plantar fascia was performed by measuring the mean gray level of the region of interest using Digital Imaging and Communications in Medicine viewer software. Sonographic evaluation of the thickness of the plantar fascia showed high reliability. Sonographic evaluations of the presence or absence of hypoechoic change in the plantar fascia showed surprisingly low agreement. The reliability of gray-scale evaluations appears to be much better than subjective judgments in the evaluation of echogenicity. Transverse scanning did not show any advantage in sonographic evaluation of the plantar fascia. The reliability of sonographic examination of the thickness of the plantar fascia is high. Mean gray-level analysis of quantitative sonography can be used for the evaluation of echogenicity, which could reduce discrepancies in the interpretation of echogenicity by different sonographers. Longitudinal instead of transverse scanning is recommended for imaging the plantar fascia. Copyright © 2011 Wiley Periodicals, Inc.

  11. Scale Thickness Measurement of Steam Generator Tubing Using Eddy Current Signal of Bobbin Coil

    International Nuclear Information System (INIS)

    Kim, Chang Soo; Um, Ki Soo; Kim, Jae Dong

    2012-01-01

    Steam generator is one of the major components of nuclear power plant and steam generator tubes are the pressure boundary between primary and secondary side, which makes them critical for nuclear safety. As the operating time of nuclear power plant increases, not only damage mechanisms but also scaled deposits on steam generator tubes are known to be problematic causing tube support flow hole blockage and heat fouling. The ability to assess the extent and location of scaled deposits on tubes became essential for management and maintenance of steam generator and eddy current bobbin data can be utilized to measure thickness of scale on tubes. In this paper, tube reference standards with various thickness of scaled deposit has been set up to provide information about the overall deposit condition of steam generator tubes, providing essential tool for steam generator management and maintenance to predict and prevent future damages. Also, methodology to automatically measure scale thickness on tubes has been developed and applied to field data to estimate overall scale amount.

  12. Equations of bark thickness and volume profiles at different heights with easy-measurement variables

    Energy Technology Data Exchange (ETDEWEB)

    Cellini, J. M.; Galarza, M.; Burns, S. L.; Martinez-Pastur, G. J.; Lencinas, M. V.

    2012-11-01

    The objective of this work was to develop equations of thickness profile and bark volume at different heights with easy-measurement variables, taking as a study case Nothofagus pumilio forests, growing in different site qualities and growth phases in Southern Patagonia. Data was collected from 717 harvested trees. Three models were fitted using multiple, non-lineal regression and generalized linear model, by stepwise methodology, iteratively reweighted least squares method for maximum likelihood estimation and Marquardt algorithm. The dependent variables were diameter at 1.30 m height (DBH), relative height (RH) and growth phase (GP). The statistic evaluation was made through the adjusted determinant coefficient (r2-adj), standard error of the estimation (SEE), mean absolute error and residual analysis. All models presented good fitness with a significant correlation with the growth phase. A decrease in the thickness was observed when the relative height increase. Moreover, a bark coefficient was made to calculate volume with and without bark of individual trees, where significant differences according to site quality of the stands and DBH class of the trees were observed. It can be concluded that the prediction of bark thickness and bark coefficient is possible using DBH, height, site quality and growth phase, common and easy measurement variables used in forest inventories. (Author) 23 refs.

  13. Wall thickness measurements of tubes by Internal Rotary Inspection System (IRIS)- a comparative study with metallography

    International Nuclear Information System (INIS)

    Subramanian, C.V.; Joseph, A.; Ramesh, A.S.; Jayakumar, T.; Kalyanasundaram, P.; Baldev Raj

    1996-01-01

    Internal Rotary Inspection System (IRIS) is a relatively new ultrasonic system of heat exchanger/ steam condenser tubes and pipelines for measurement of wall thinning and pitting due to corrosion. The wall thickness measurements made during a scan around the circumference of the tube are displayed as a stationary rectilinear display of circumferential cross section (Bscan) of the tube. The paper describes the results obtained on tubes of various materials used in process industries having corrosion on inner and outer surfaces of the tube. (author)

  14. Microprocessor isotope gauges for measurement of coating thickness and of air dust pollution

    International Nuclear Information System (INIS)

    Machaj, B.; Zrudelny, F.; Sikora, A.; Jaszczuk, J.

    1986-01-01

    The article describes a coating thickness gauge based on measurement of backscattered beta particles, and an air dust pollution gauge based on measurement of dust deposited from known volume of ambient air passed through a filter, by attenuation of beta radiation. In both cases to control the gauges and to process head signals microcomputer system based on Intel 8080 microprocessor is employed. Algorithms for processing and control of the gauges and corresponding flow charts are presented. Block diagram of microcomputer system used is presented, as well as the manner of operation of the gauges. (author)

  15. The effects of high-Dk rigid contact lens center thickness, material permeability, and blinking on the oxygen uptake of the human cornea.

    Science.gov (United States)

    Gardner, Hope Patterson; Fink, Barbara A; Mitchell, Lynn G; Hill, Richard M

    2005-06-01

    The human corneal oxygen uptake responses associated with the static (nonblinking) and dynamic (blinking) wear of five rigid gas-permeable materials with high oxygen permeabilities were determined for three different center thicknesses and compared with the responses for the normal open eye and severe hypoxic stress (static wear of polymethylmethacrylate). Corneal oxygen uptake rates were measured with a Clark-type polarographic electrode during two sessions with each of 10 human subjects. Measurements were made on the right eye for the normal open eye (air) and after 5 minutes of static and dynamic wear of polymethylmethacrylate and five rigid gas-permeable contact lens materials: Fluoroperm 92 (paflufocon A, Dk = 92), Fluoroperm 151 (paflufocon D, Dk = 151), 1992 Menicon SF-P (melafocon A, Dk = 102), 1995 Menicon SF-P (melafocon A, Dk = 159), and Menicon Z (tisilfocon A, Dk = 163-250). Lenses were manufactured in three different center thicknesses (0.12, 0.16, and 0.20 mm), with all other parameters remaining constant. Repeated-measures analysis of variance was used and included lens material (five levels), blinking condition (two levels), and lens thickness (three levels) as within-subject effects. Significant differences were found in corneal oxygen responses to lens material (p Dk rigid lens materials studied here, moderate changes in lens thickness or material permeability may result in modest differences in corneal hypoxic relief, whereas blinking results in no significant improvement to corneal oxygenation.

  16. Tear Mediators in Corneal Ectatic Disorders.

    Directory of Open Access Journals (Sweden)

    Dorottya Pásztor

    Full Text Available To compare the concentrations of 11 tear mediators in order to reveal the biochemical difference between pellucid marginal degeneration (PMD and keratoconus (KC.We have designed a cross-sectional study in which patients with corneal ectasia based on slit-lamp biomicroscopy and Pentacam HR (keratometry values (K1, K2, Kmax, astigmatism, minimal radius of curvature (Rmin, corneal thickness (Apex and Min, indices (surface variation, vertical asymmetry, keratoconus, central keratoconus, height asymmetry and decentration were enrolled. Eyes of keratoconic patients were similar to the PMD patients in age and severity (K2, Kmax and Rmin. Non-stimulated tear samples were collected from nine eyes of seven PMD patients, 55 eyes of 55 KC patients and 24 eyes of 24 healthy controls. The mediators' (interleukin -6, -10, chemokine ligand 5, -8, -10, matrix metalloproteinase (MMP -9, -13, tissue inhibitor of metalloproteinases (TIMP-1, tissue plasminogen activator, plasminogen activator inhibitor, nerve growth factor concentrations were measured using Cytometric Bead Array.MMP-9 was the only mediator which presented relevant variances between the two patient groups (p = 0.005. The ratios of MMP-9 and TIMP-1 were 2.45, 0.40 and 0.23 in PMD, KC and the controls, respectively.As far as we are aware, this is the first study that aims to reveal the biochemical differences between PMD and KC. Further studies of biomarkers to investigate the precise role of these mediators need to be defined, and it is important to confirm the observed changes in a larger study to gain further insights into the molecular alterations in PMD.

  17. Comparison of stromal corneal nerves between normal and keratoconus patients using confocal microscopy.

    Science.gov (United States)

    Ramírez Fernández, M; Hernández Quintela, E; Naranjo Tackman, R

    2014-08-01

    To evaluate the differences in stromal corneal nerves between normal patients and keratoconus patients. A total of 140 eyes of 70 normal patients (group A) and 122 eyes of 87 keratoconus patients (group B) were examined with the confocal microscope, with a central scan of the total corneal thickness being taken. The morphology and thickness of the corneal stromal nerves were evaluated by using the Navis v. 3.5.0. software. Nerve thickness was obtained from the mean between the widest and the narrowest portions of each stromal nerve. Corneal stromal nerves were observed as irregular linear hyper-reflective structures with wide and narrow portions in all cases. Mean corneal stromal nerves thickness in group A was 5.7±1.7 (range from 3.3 to 10.4 μ), mean corneal stromal nerves thickness in group B was 7.2±1.9 (range from 3.5 to 12.0 μ). There was a statistical significant difference (P<.05) in stromal corneal nerves thickness between group A and group B. Stromal corneal nerves morphology was similar in both groups, but stromal nerves were thicker in keratoconus patients. Copyright © 2013 Sociedad Española de Oftalmología. Published by Elsevier Espana. All rights reserved.

  18. Finite grid radius and thickness effects on retarding potential analyzer measured suprathermal electron density and temperature

    International Nuclear Information System (INIS)

    Knudsen, W.C.

    1992-01-01

    The effect of finite grid radius and thickness on the electron current measured by planar retarding potential analyzers (RPAs) is analyzed numerically. Depending on the plasma environment, the current is significantly reduced below that which is calculated using a theoretical equation derived for an idealized RPA having grids with infinite radius and vanishingly small thickness. A correction factor to the idealized theoretical equation is derived for the Pioneer Venus (PV) orbiter RPA (ORPA) for electron gases consisting of one or more components obeying Maxwell statistics. The error in density and temperature of Maxwellian electron distributions previously derived from ORPA data using the theoretical expression for the idealized ORPA is evaluated by comparing the densities and temperatures derived from a sample of PV ORPA data using the theoretical expression with and without the correction factor

  19. Boundaries of dreams, boundaries of dreamers: thin and thick boundaries as a new personality measure.

    Science.gov (United States)

    Hartmann, E

    1989-11-01

    Previous work by the author and his collaborators on frequent nightmare sufferers demonstrated that these people had striking personality characteristics which could be called "thin boundaries" in a number of different senses. In order to measure thin and thick boundaries, a 145-item questionnaire, the Boundary Questionnaire, has been developed which has now been taken by over 1,000 persons. Preliminary results are presented indicating that, as predicted a priori, several new groups of nightmare sufferers and groups of art students scored usually "thin," whereas a group of naval officers had usually "thick" boundaries. Overall, thinness on the Boundary Questionnaire correlated highly positively (r = .40) with frequency of dream recall and also significantly (r = .16) with length of sleep.

  20. Measurement of thickness of thin films by the X-ray diffraction method

    International Nuclear Information System (INIS)

    Srinivasan, C.; Balasingh, C.; Singh, A.K.

    1979-07-01

    X-ray diffraction method can be used to measure the thickness of thin films (coatings). The principle and the experimental details of the x-ray diffraction methods are described. The intensities of the diffracted beams are derived assuming a random orientation of the crystallites in the diffracting medium. Consequently, the expressions are not valid when the sample has preferred orientation. To check the performance of the method, thicknesses of nickel deposits on mild steel plates were determined by the x-ray diffraction method and the results compared with those obtained by the weighing method and metallographic examination. The weighing method which gives an accuracy of +- 0.1 micron is taken as the standard. The x-ray diffraction methods and the metallographic examinations give values within +- 1 micron of the value obtained by the weighing method. (author)

  1. Apparent increase in the thickness of superconducting particles at low temperatures measured by electron holography.

    Science.gov (United States)

    Hirsch, J E

    2013-10-01

    We predict that superconducting particles will show an apparent increase in thickness at low temperatures when measured by electron holography. This will result not from a real thickness increase, rather from an increase in the mean inner potential sensed by the electron wave traveling through the particle, originating in expansion of the electronic wavefunction of the superconducting electrons and resulting negative charge expulsion from the interior to the surface of the superconductor, giving rise to an increase in the phase shift of the electron wavefront going through the sample relative to the wavefront going through vacuum. The temperature dependence of the observed phase shifts will yield valuable new information on the physics of the superconducting state of metals. Copyright © 2013 Elsevier B.V. All rights reserved.

  2. Choroidal thickness changes after dynamic exercise as measured by spectral-domain optical coherence tomography

    Directory of Open Access Journals (Sweden)

    Nihat Sayin

    2015-01-01

    Full Text Available Purpose: To measure the choroidal thickness (CT after dynamic exercise by using enhanced depth imaging optical coherence tomography (EDI-OCT. Materials and Methods: A total of 19 healthy participants performed 10 min of low-impact, moderate-intensity exercise (i.e., riding a bicycle ergometer and were examined with EDI-OCT. Each participant was scanned before exercise and afterward at 5 min and 15 min. CT measurement was taken at the fovea and 1000 μ away from the fovea in the nasal, temporal, superior, and inferior regions. Retinal thickness, intraocular pressure, ocular perfusion pressure (OPP, heart rate, and mean blood pressure (mBP were also measured. Results: A significant increase occurred in OPP and mBP at 5 min and 15 min following exercise (P ˂ 0.05. The mean subfoveal CT at baseline was 344.00 ± 64.71 μm compared to 370.63 ± 66.87 μm at 5 min and 345.31 ± 63.58 μm at 15 min after exercise. CT measurements at all locations significantly increased at 5 min following exercise compared to the baseline (P ˂ 0.001, while measurements at 15 min following exercise did not significant differ compared to the baseline (P ˃ 0.05. There was no significant difference in retinal thickness at any location before and at 5 min and 15 min following exercise (P ˃ 0.05. Conclusion: Findings revealed that dynamic exercise causes a significant increase in CT for at least 5 min following exercise.

  3. Development of liquid film thickness measurement technique by high-density multipoint electrodes method

    International Nuclear Information System (INIS)

    Arai, Takahiro; Furuya, Masahiro; Kanai, Taizo

    2010-01-01

    High-density multipoint electrode method was developed to measure a liquid film thickness transient on a curved surface. The devised method allows us to measure spatial distribution of liquid film with its conductance between electrodes. The sensor was designed and fabricated as a multilayer print circuit board, where electrode pairs were distributed in reticular pattern with narrow interval. In order to measure a lot of electrode pairs at a high sampling rate, signal-processing method used by the wire mesh sensor measurement system was applied. An electrochemical impedance spectrometry concludes that the sampling rate of 1000 slices/s is feasible without signal distortion by electric double layer. The method was validated with