Evaluation of Changes in Refractive Errors Before and After Trabeculectomy and Shunt Surgery.

PURPOSE: The aim of the present study was to investigate the change rate of astigmatism and axial, myopia, and hypermetropia in trabeculectomy and shunt surgery. PATIENTS AND METHODS: In this comparative study, two groups of 16 patients with an average age of 52.4±8.9 and 94.6±6.7 respectively underwent trabeculectomy and shunt surgery. The changes of reactive error were compared before the surgery and 1 week, 1 month, and 3 months after the surgery. Data from the two groups were analyzed via Friedman and Mann-Whitney tests. RESULTS: Average of intraocular pressure (IOP) before, and 1 week, 1 month, and 3 months after trabeculectomy is 31.31±7.6, 9.8±2.8, 10.5±1.29, 10.9±1.26 (P<0.05) and shunt is 36.06±10.32, 13.5±3.3, 11.68±2.21, 11.18±1.27 (P<0.05). Average astigmatism in trabeculectomy is -1.00±0.59, -6.00±1.9, -2.21±1.18, -1.37±0.62 (P<0.05) and in shunt it is -0.89±0.46, -1.56±1.62, -1.51±1.46, -1.07±0.85 (P>0.05). Percent WRT astigmatism in trabeculectomy is 37.5, 100, 37.5, 31.25 and in shunt it is 43.75, 50, 50, 56.25 and average of spherical equivalence (SE) in trabeculectomy is -0.31±1.49, 1.43±1.94, 0.27±1.74, 0.04±1.46 (P<0.05) and in shunt it is 0.65±1.5, 1.03±2.03, -0.70±1.64, 0.62±1.54 (P<0.05). Astigmatism and axial comparisons between trabeculectomy and shunt with Mann-Whitney test were significant (P<0.05), but SE was not significant (P>0.05). CONCLUSION: The surgeries induced hypermetropia and reduction with the passing of time but astigmatism amount and percent of with-the-rule astigmatism in trabeculectomy were more than in shunt surgery.

Intrasubject Repeatability and Interdevice Agreement of Anterior Chamber Depth Measurements by Orbscan and Pentacam in Different Grades of Keratoconus.

OBJECTIVES: To evaluate the repeatability of anterior chamber depth (ACD) measurements by Orbscan and Pentacam imaging devices in different grades of keratoconus. METHODS: One examiner performed 3 consecutive ACD measurements with both devices on 74 eyes of 42 keratoconus patient. Repeatability was assessed using intrasession test-retest variability. Within-subject SD was determined for repeatability, and the coefficient of variation was calculated for each measurement. The intraclass correlation coefficient (ICC) was also determined to assess the variance of repeated data. RESULTS: Overall, the three ACD measurements were not significantly different either with Pentacam or Orbscan. The ICC index values were greater than 90% with both devices, and it significantly reduced at higher grades of keratoconus with Pentacam. Interdevice differences were statistically significant. The interdevice agreement with ACD measurements was 0.981, and the agreement was lower at higher grades of keratoconus. The 95% limits of agreement between the 2 devices for ACD was from -0.19 to 0.04. CONCLUSIONS: Our results indicate acceptable repeatability for ACD measurements with both Orbscan and Pentacam in keratoconus patients. The progression of keratoconus has no significant effect on repeatability results of these devices. The good agreement between them allows their interchangeable use.

Macular Thickness in Moderate to Severe Amblyopia.

PURPOSE: To compare the macular retinal thickness of moderately to severely amblyopic eyes with non-amblyopic eyes as controls. METHODS: This case control study was conducted on 56 children aged 4 to 10 years old (64.3% female subjects). Twenty-eight children had unilateral amblyopia (28 amblyopic eyes as cases and 28 normal fellow eyes as internal controls) and 28 children had normal visual acuity in both eyes and were considered as external controls (n = 56 eyes). Among our cases, 14 had strabismic amblyopia and 14 had anisometropic amblyopia. Macular retinal thickness was measured using optical coherence tomography at the center and in 1-, 3-, and 6-mm rings. RESULTS: Best-corrected visual acuity of the amblyopic eyes was less than that of the internal and external controls, and the best-corrected visual acuity of their fellow eyes was also less than that of the external controls. Thickness of the central macula and a 1-mm ring area in the amblyopic eyes was higher than that of both internal and external controls. Difference of central macular thickness ≥20 µm between two eyes of the amblyopic children was significantly more than non-amblyopic subjects. CONCLUSIONS: Based on the results of this study, the macular retinal thickness was significantly higher in moderate to severe amblyopic eyes compared to their fellow eyes and external controls. This might be due to macular developmental disorders in amblyopic eyes. Therefore, optical coherence tomography imaging is recommended if subtle macular abnormalities are suspected in moderate to severe amblyopic eyes.

Characteristics of Posterior Corneal Astigmatism in Different Stages of Keratoconus.

PURPOSE: To evaluate the magnitudes and axis orientation of anterior corneal astigmatism (ACA) and posterior corneal astigmatism (PCA), the ratio of ACA to PCA, and the correlation between ACA and PCA in the different stages of keratoconus (KCN). METHODS: This retrospective case series comprised 161 eyes of 161 patients with KCN (104 men, 57 women; mean age, 22.35 ± 6.10 years). The participants were divided into four subgroups according to the Amsler-Krumeich classification. A Scheimpflug imaging system was used to measure the magnitude and axis orientation of ACA and PCA. The posterior-anterior corneal astigmatism ratio was also calculated. The results were compared among different subgroups. RESULTS: The average amounts of anterior, posterior, and total corneal astigmatism were 4.08 ± 2.21 diopters (D), 0.86 ± 0.46 D, and 3.50 ± 1.94 D, respectively. With-the-rule, against-the-rule, and oblique astigmatisms of the posterior surface of the cornea were found in 61 eyes (37.9%), 67 eyes (41.6%), and 33 eyes (20.5%), respectively; corresponding figures in the anterior corneal surface were 55 eyes (32.4%), 56 eyes (34.8%), and 50 eyes (31.1%), respectively. A strong correlation (P ≤ 0.001, r = 0.839) was found between ACA and PCA in the different stages of KCN; the correlation was weaker in eyes with grade 3 (P ≤ 0.001, r = 0.711) and grade 4 (P ≤ 0.001, r = 0.717) KCN. The maximum posterior-anterior corneal astigmatism ratio (PCA/ACA, 0.246) was found in patients with stage 1 KCN. CONCLUSION: Corneal astigmatism in anterior surface was more affected than posterior surface by increasing in the KCN severity, although PCA was more affected than ACA in an early stage of KCN.

Contrast sensitivity to spatial gratings in moderate and dim light conditions in patients with diabetes in the absence of diabetic retinopathy.

OBJECTIVE: To evaluate the ability of contrast sensitivity (CS) to discriminate loss of visual function in diabetic subjects with no clinical signs of retinopathy relative to that of normal subjects. RESEARCH DESIGN AND METHODS: In this prospective cross-sectional study, we measured CS in 46 diabetic subjects with a mean age of 48±6 years, a best-corrected visual acuity of 20/20 and no signs of diabetic retinopathy. The CS in these subjects was compared with CS measurements in 46 normal control subjects at four spatial frequencies (3, 6, 12, 18 cycles per degree) under moderate (500 lux) and dim (less than 2 lux) background light conditions. RESULTS: CS was approximately 0.16 log units lower in patients with diabetes relative to controls both in moderate and in dim background light conditions. Logistic regression classification and receiver operating characteristic curve analysis indicated that CS analysis using two light conditions was more accurate (0.78) overall compared with CS analysis using only a single illumination condition (accuracy values were 0.67 and 0.70 in moderate and dim light conditions, respectively). CONCLUSIONS: Our results showed that patients with diabetes without clinical signs of retinopathy exhibit a uniform loss in CS at all spatial frequencies tested. Measuring the loss in CS at two spatial frequencies (3 and 6 cycles per degree) and two light conditions (moderate and dim) is sufficiently robust to classify diabetic subjects with no retinopathy versus control subjects.

Corneal thickness measurements with Scheimpflug and slit scanning imaging techniques in keratoconus.

PURPOSE: To determine the repeatability of corneal thickness measurements with Scheimpflug (Pentacam) and slit scanning (Orbscan) imaging techniques in different grades of keratoconus. METHODS: This study was conducted as a cross-sectional research. Imaging with Orbscan and Pentacam was performed on patients with different grades of keratoconus. With each device, 3 measurements were taken at 10 min intervals. Repeatability indices in different grades of keratoconus were calculated for each device. RESULTS: Seventy-four eyes of 42 keratoconus patients were enrolled. Repeatability index (RI) of central corneal thickness (CCT) measurements in keratoconus grade 1, 2, and 3, were 12.8, 9.9, and 24.2 with Pentacam, and 23.6, 26.3, and 59.3 with Orbscan, respectively. For the thinnest point, these figures were 9.6, 8.0, and 35.7 with Pentacam and 19.5, 16.6, and 26.8 with Orbscan, respectively. The 95% limit of agreement (LOA) between Pentacam and Orbscan in measuring CCT and thinnest point in grade 1 were -25.5-47.7 mic and -33.3-32.8 mic, respectively. These results for grade 2 were -9.8-50.6 mic and -26.2-43.7 mic, respectively. In grade 3, 95% LoA were -20-64.6 mic and -31.4-60.5 mic, respectively. CONCLUSIONS: The results of this study showed that although repeated measurements of the CCT with Orbscan and Pentacam are strongly correlated, repeatability values of CCT measurements significantly decrease at more advanced grades of keratoconus. In all keratoconus grades, repeatability of CCT measurements was better with Pentacam than Orbscan. These findings indicate that corneal thickness readings have less validity in patients with advanced keratoconus.

Photorefractive keratectomy for patients with preoperative low Schirmer test value.

PURPOSE: To compare dry eye signs and symptoms between patients with preoperative low and normal Schirmer test after Photorefractive keratectomy (PRK). METHODS: In this prospective, nonrandomized, comparative case series, 76 eyes of 76 patients were preoperatively categorized into two groups according to selected criteria for characterization of tear film status: the low Schirmer test value (STV) group and the normal STV group. For the tear function assessment, we performed a Schirmer test with and without anesthesia, tear break-up time (TBUT) test, and measurement dry eye symptoms using the Farsi translation of Ocular Surface Disease Index (OSDI) questionnaire pre- and 3 months post-operation. RESULTS: Postoperatively, the Schirmer and TBUT values were significantly lower in both groups than preoperatively (all p < 0.05). Deterioration in tear secretion was significantly greater in the low STV group (p = 0.012), but tear stability was more compromised in the normal STV group (p = 0.021). The changes in OSDI score were not significant between the two groups. CONCLUSION: These results demonstrated that tear function deteriorates after PRK. Therefore, patients with low preoperative Schirmer test values should be thoroughly assessed for dry eye before proceeding with refractive surgery to eliminate postoperative complication.

Intraocular pressure measurement by three different tonometers in primary congenital glaucoma.

PURPOSE: To determine the agreement between intraocular pressure (IOP) measurements using an automated non-contact tonometer (NCT), Goldmann applanation tonometer (GAT), and the ocular response analyzer (ORA) in subjects with primary congenital glaucoma (PCG). METHODS: Twenty-nine eyes of 17 PCG patients underwent IOP measurements using NCT, GAT and ORA. Variables obtained by the ORA were corneal-compensated IOP (IOPcc), Goldmann-correlated IOP (IOPg), corneal hysteresis (CH), and corneal resistance factor (CRF). A difference more than 1.5 mmHg for IOP was considered as clinically relevant. RESULTS: Mean age of the patients was 12 years. Mean IOP (±standard deviation, SD) was 15.3 ± 2.8 mmHg (GAT), 15.5 ± 6.0 (NCT), 19.2 ± 7.0 (IOPg), and 21.1 ± 7.9 (IOPcc); (P = 0.001). Except for NCT vs. GAT (P = 1.0), the average IOP difference between each pair of measurements was clinically relevant. The 95% limits of agreements were - 10.2 to 10.3 mmHg (NCT vs. GAT), -7.8 to 15.3 (IOPg vs. GAT), and - 8.1 to 19.0 (IOPcc vs. GAT). The differences in IOP measurements increased significantly with higher average IOP values (r = 0.715, P = 0.001, for NCT vs. GAT; r = 0.802, P < 0.001, for IOPg vs. GAT; and r = 0.806, P < 0.001, for IOPcc vs. GAT). CH showed a significant association with differences in IOP measurements only for IOPcc vs. GAT (r = 0.830, P < 0.001). CONCLUSION: Mean IOP obtained by NCT was not significantly different from that of GAT, but ORA measured IOPs were significantly higher than both other devices.

Comparison of keratometry measurements using the Pentacam HR, the Orbscan IIz, and the TMS-4 topographer.

PURPOSE: To compare and evaluate the agreement between keratometry readings using three devices: the Pentacam HR, the Orbscan IIz, and the TMS-4 topographer. METHODS: In this prospective comparative study, 115 eyes from 115 healthy refractive surgery candidates were sequentially examined using three devices. Fourier analysis was used to evaluate corneal astigmatism in these subjects. The outcome measures comprised steep and flat keratometry readings, corneal astigmatism, the mean keratometry reading, and the J0 and J45 components. Repeated-measures analysis of variance (RM-anova) and Bland-Altman plots with 95% limits of agreement were used to evaluate the difference between measurements. RESULTS: The mean keratometry readings were 43.89 ± 1.51, 43.52 ± 1.48, and 43.79 ± 1.50 D using the TMS-4 topographer, the Orbscan IIz, and the Pentacam HR, respectively (p < 0.001; RM-anova). The mean keratometric astigmatism was 1.27 ± 0.87, 1.20 ± 0.86, and 1.21 ± 0.82 D using the TMS-4 topographer, the Orbscan IIz, and the Pentacam HR, respectively (p = 0.007; RM-anova). The J0 measurements were higher using the TMS-4 topographer compared with the Orbscan IIz (p = 0.021; Bonferroni test). The mean, steep, and flat keratometry data were in better agreement using the TMS-4 topographer and the Pentacam HR. In general, the Orbscan IIz device measured lower values than either the TMS-4 topographer or the Pentacam HR. However, the corneal astigmatism measurements and the J0 component showed the best agreement using the TMS-4 topographer and the Orbscan IIz. CONCLUSIONS: The TMS-4 topographer and the Pentacam HR produced similar readings and can be used interchangeably to measure simulated keratometry values in young, healthy eyes. To measure corneal astigmatism, the TMS-4 topographer and the Orbscan IIz produced values that were similar and could be used interchangeably.