The effect of trabeculectomy on contrast sensitivity, corneal topography and aberrations.

PURPOSE: To investigate the effect of trabeculectomy on corneal topography, corneal sensitivity and aberrations. METHODS: Twenty-four eyes of 24 subjects with open-angle glaucoma who required glaucoma filtration surgery were assessed. The evaluation of corneal topography, corneal sensitivity and aberrations were done before the trabeculectomy procedure, 1 week and 1 month after the trabeculectomy. RESULTS: There were significant differences in cylindrical power (P = 0.02), contrast sensitivity at 12 cycle/degree spatial frequency (P = 0.04) as well as high order aberration (P = 0.04) and high order without spherical component (P = 0.02) following trabeculectomy. However, significant differences were found for keratometric results and Fourier index in 3 and 6 mm pupil diameters between pre- and post-trabeculectomy (P > 0.05). CONCLUSIONS: According to the findings of the current study, trabeculectomy affects contrast sensitivity at 12 cycle/degree spatial frequency, higher-order aberration and higher order without spherical component aberration 1 month after trabeculectomy. Being knowledgeable about these changes may lead to some advancement in post-surgical management of patients particularly in early stages following trabeculectomy.

Evaluation of anterior chamber angle under dark and light conditions in angle closure glaucoma: An anterior segment OCT study.

AIM: To evaluate changes of nasal and temporal anterior chamber angle (ACA) in subjects with angle closure glaucoma using Spectralis AS-OCT (SAS-OCT) under dark and light conditions. METHODS: Based on dark-room gonioscopy, 24 subjects with open angles and 86 with narrow angles participated in this study. The nasal and temporal angle opening distance at 500 µm anterior to the scleral spur (AOD500), nasal and temporal ACA were measured using SAS-OCT in light and dark conditions. RESULT: In 2 groups, ACA and AOD500 in nasal and temporal quadrants were significantly greater in light compared to dark (all with p=0.000). The AOD500 and ACA were significantly higher in nasal than temporal in measured conditions for 2 groups except the ACA and AOD500 of normal group measured in light. The difference between nasal and temporal in dark (29.07 ± 65.71 µm for AOD500 and 5.7 ± 4.07° for ACA) was greater than light (24.86 ± 79.85 µm for AOD500 and 2.09 ± 7.21° for ACA) condition. But the difference was only significant for ACA (p=0.000). The correlation analysis showed a negative correlation between AOD500 and pupil diameter in temporal and nasal quadrants (both with p=0.000). While temporal AOD500 difference correlated with spherical equivalent, temporal and asal gonioscopy, nasal AOD correlated with IOP, temporal and nasal gonioscopy. CONCLUSIONS: Clinically important changes in ACA structure could be detected with SAS-OCT in nasal and temporal quadrants under different illumination intensity. The results could help in improvement of examination condition for better and more accurate assessment of individuals with angle closure glaucoma.

Prevalence of Refractive Errors in Students with and without Color Vision Deficiency.

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

Efficacy of corneal tomography parameters and biomechanical characteristic in keratoconus detection.

AIM: To determine the efficacy of corneal thickness parameters and corneal biomechanical properties (CBPs) in discriminating between normal and keratoconus eyes. METHOD: After performing a comprehensive ophthalmic examination, 50 mild to moderate keratoconus and 50 age and sex matched myopic astigmatism eyes were prospectively included in the study. The corneal topographic maps and CBP were obtained by Pentacam and Ocular response analyser, respectively. Central corneal thickness (CCT), thinnest corneal thickness (TCT), corneal thickness (CT) and percentage thickness increase (PTI) at 1, 3 and 5mm from the thinnest point and corneal volume (CV) at 3, 5, 7 and 10 centred on thinnest point, corneal hysteresis (CH) and corneal resistance factor (CRF) were recorded. Independent t-test and receiver operating characteristic (ROC) were done with SPSS software (version 15.0, SPSS, Inc.). RESULTS: CCT, TCT, CT at 1, 3 and 5, CV at 3, 5, 7 and 10mm, CH and CRF were significantly lower in keratoconus eyes compared to controls (p<0.001). In addition, PTI at 1, 3 and 5mm from the thinnest point showed significantly higher values in keratoconus group. ROC analysis demonstrated good predictive accuracy for cut-off point values. However, the centrally located indices had higher predictive accuracy compared to the peripherally located indices. CONCLUSION: Although good sensitivity and specificity were found for the mentioned parameters, the centrally located indices had higher predictive accuracy compared to peripherally located indices. It is suggested to use a combination of corneal pachymetry together with CBP for more accurate detection of keratoconus.

Assessment of the anterior chamber parameters after laser iridotomy in primary angle close suspect using Pentacam and gonioscopy.

AIM: To evaluate the changes in the anterior segment parameters of the subjects with primary angle closure suspect (PACS) before and after laser iridotomy (LI) using the Pentacam and gonioscopy. METHODS: Forty-eight eyes of 48 PACS were included. Anterior chamber angle (ACA), central anterior chamber depth (ACD), anterior chamber volume (ACV) and central corneal thickness (CCT) were recorded from the Pentacam before and one month after LI. ACA was graded according to Shaffer classification using the Goldmann gonioscopy. RESULTS: ACA increased significantly from 25.59±4.41 to 26.46±4.33 degrees (P=0.009) and ACV changed from 85.97±16.07mm(3) to 99.25±15.83mm(3) (P=0.000). The changes in ACD, CCT and intraocular pressure were non-significant (P>0.05). Gonioscopy showed significant widening of the Shaffer angle in 4 quadrants (P<0.001). CONCLUSION: Pentacam can serve as the objective instrument in assessing the efficacy of LI.

Anterior segment changes following short-term reading and its correlation with corneal biomechanical characteristics.

PURPOSE: To investigate the changes in anterior segment following short-term reading and evaluate the correlation of such changes with corneal biomechanical characteristics (CBC). METHODS: Thirty-six right eyes of 36 healthy subjects were examined. Anterior segment parameters were measured using the Pentacam before and after 30 min of reading. Ocular Response Analyzer was used to record CBC after reading. The following were recorded: central corneal thickness (CCT), central corneal power (CCP), superior corneal power (SCP), inferior corneal power (ICP), anterior chamber depth (ACD), anterior chamber volume (ACV), anterior chamber angle (ACA), corneal hysteresis (CH) and corneal resistance factor (CRF). Statistical analysis was performed with the paired student t-test and Pearson correlation test in SPSS 16. RESULTS: There were statistically significant decreases in CCP, SCP, ACD and ACV values following reading (p < 0.05). Our results showed a statistically significant negative correlation between CH and changes in ICP (r = 0.36, p = 0.02). Significant negative correlations were also found between CRF and changes in ICP (r = 0.41, p = 0.01) and SCP (r = 0.34, p = 0.04). On the other hand, statistical analysis indicated no correlation between CBC and other studied parameters (p > 0.05). CONCLUSION: This study demonstrated significant changes in some anterior segment parameters after reading. Being knowledgeable about these changes may have important implications in high accuracy examinations such as pre-operative assessment of corneal refractive surgery candidates. This could also help researchers have a better understanding of the factors that may influence near work related development of refractive errors.

Anterior segment parameters in Indian young adults using the Pentacam.

To evaluate Pentacam-Scheimpflug imaging of anterior segment parameters in young Indian adults. In this prospective study 120 eyes of 60 normal Indian subjects with a mean age of 25.93 ± 6.58 years (range 17-39 years) were assessed by Pentacam. Main outcome measures were central corneal thickness (CCT), thinnest corneal thickness (TCT), apex corneal thickness (apex CT), peripheral corneal thickness at 2, 4, 6 and 8 mm from the thinnest point, location of the thinnest pachymetry, corneal volume (CV), anterior chamber depth (ACD), anterior chamber volume (ACV) and anterior chamber angle (ACA). Independent samples t test, dependent samples t test, ANOVA and Pearson correlation test were used for statistical analysis. The mean CCT, TCT, Apex CT and CV were 544.95 ± 35.42, 542 ± 35.19, 545.43 ± 35.45 and 61.64 ± 4.17 µm, respectively. There was a gradual increase in CT from the thinnest point to the periphery. The mean ACD was 3.14 ± 0.33 mm, mean ACV was 177.77 ± 29.02 mm(3), and mean ACA was 39.36° ± 5.42°. There was no significant difference between CCT, TCT and Apex CT. A significant positive correlation was found between CCT and peripheral CT and also between anterior chamber parameters. TCT was mainly located in the inferotemporal and superotemporal zone. No significant difference was found in parameters between the right and left eyes and also between genders. This study provided information about a wide range of parameters in the anterior segment of healthy Indian eyes. These results could be helpful in assessment of patients with corneal diseases, glaucoma and screening for refractive surgeries.

Anterior segment characteristics of keratoconus eyes in a sample of Asian population.

PURPOSE: To assess changes in anterior segment parameters of keratoconus eyes at different stages of the disease in a sample of the Asian population. METHODS: Files of 32 patients (48 eyes) diagnosed as clinical keratoconus were assessed and the following parameters noted: central corneal thickness (CCT), thinnest corneal thickness (TCT), location of thinnest pachymetry, anterior chamber depth (ACD) at the centre from posterior corneal surface, ACD at 1, 2 and 3mm inferior-paracentral, ACD at thinnest pachymetry, anterior chamber volume (ACV) and anterior chamber angle (ACA). For analysis, keratoconus eyes were classified into 3 subgroups according to mean keratometry readings (mild: K≤47.0D, moderate: 47.0

Corneal thickness and volume in subclinical and clinical keratoconus.

To evaluate corneal thickness and volume in subclinical and clinical keratoconus in Asian population with the aim of discriminating between normal and ectatic cornea. Eyes were placed into one of the following three groups: normal, subclinical, and mild-moderate keratoconus. Pentacam Scheimpflug imaging (Oculus Inc., Wetzlar, Germany) was performed for each participant to record thinnest corneal thickness, central corneal thickness, corneal volume (CV), peripheral corneal thickness (PCT) and percentage thickness increase (PTI) at 2, 4, 6, and 8 mm. The data were exported to SPSS for statistical analysis. Subjects comprised 52 normal, 15 subclinical keratoconus, and 32 mild-moderate clinical keratoconus eyes. Our results indicated that corneal thickness (CT) distribution, PTI, and CV in normal eyes were significantly different compared with subclinical and clinical keratoconus (P < .05). Overall, subclinical group exhibited lower CT distribution and volume, and higher PTI in comparison with normal eyes. However, they showed higher CT distribution and volume, and lower PTI compared with keratoconus group. In addition, there was a smaller change in PCT and PTI from the thinnest point of the cornea to the periphery. The results of the present study indicate that CT parameters and CV were significantly different in normal versus subclinical group and in normal versus keratoconus group. These findings could help clinicians to better discriminate between normal and ectatic cornea.