Post penetrating keratoplasty glaucoma - A review.

Glaucoma following penetrating keratoplasty remains a challenge for the treating ophthalmologist. Its frequent occurrence, difficult diagnosis and recalcitrant nature coupled with the propensity to cause irreversible visual loss makes it essential to identify the problem early and manage it effectively. A careful pre-operative assessment along with appropriate intra-operative measures can help to reduce the chances of developing glaucoma in the post-operative period. Wherever indicated, prompt therapy should be initiated to lower intraocular pressure and salvage vision. Effective management of post-operative keratoplasty glaucoma remains an enigma with no single therapy being suited for all cases. One has to weigh the risks and benefits of the anti-glaucoma drugs on the corneal graft. However, it should be kept in mind that although there is a potential option for a graft exchange, vision lost from glaucomatous optic nerve damage cannot be recovered. This review aims at highlighting the magnitude of the problem, assessing the risk factors that predispose to post-penetrating keratoplasty glaucoma along with the methodology for its diagnosis and management.

Effect of trabeculectomy on RNFL thickness and optic disc parameters using optical coherence tomography.

PURPOSE: To study the change in retinal nerve fibre layer (RNFL) thickness and optic nerve head (ONH) parameters using optical coherence tomography (Stratus OCT 3) after trabeculectomy in adult patients with glaucoma. METHODS: A total of 17 patients with glaucoma undergoing trabeculectomy were recruited. Average and quadrant RNFL thickness measurements, vertical integrated rim area, horizontal integrated rim width, disc area, cup area, and rim area were measured using Stratus OCT within a week before surgery and at 1 week, 1 and 3 months postoperatively. Main outcome measures were change in RNFL and ONH parameters. Pre- and postoperative values were analysed using the Wilcoxon signed-rank test. RESULTS: Intraocular pressure (IOP) reduced from 30.23 ± 9.02 mm Hg preoperatively to 9.52 ± 2.42 mm Hg at 1 week, 12.35 ± 4.59 mm Hg at 1 month, and 13.6 ± 2.31 mm Hg at 3 months after trabeculectomy. A significant increase in average (P=0.019) and inferior RNFL (P=0.038) thickness was observed 1 week after surgery. At 3 months postoperatively, they had reverted to preoperative values. RNFL thickness change had no correlation with IOP change. Mean optic disc cup area decreased from 2.39 ± 0.52 mm(2) preoperatively to 2.14 ± 0.52 mm(2) at 1 week (P=0.022), 2.22 ± 0.53 mm(2) at 1 month (P=0.038), and 2.27 ± 0.60 mm(2) at 3 months (P=0.071). No significant change was found in other ONH parameters. CONCLUSIONS: Short-term fluctuations were noted in RNFL thickness and ONH postoperatively following glaucoma filtration surgery. RNFL thickness temporarily increased and cup area decreased but the values reverted to normal within 3 months.

Retinal nerve fiber layer thickness in Indian eyes with optical coherence tomography.

INTRODUCTION: Measuring the thickness of the retinal nerve fiber layer is a potential method of recognizing axon loss prior to the visual field abnormality. OBJECTIVE: To study normal individuals to quantify peripapillary retinal nerve fiber layer (RNFL) thickness in Asian Indian subjects. MATERIALS AND METHODS: This was a prospective study of 150 normal subjects. Peripapillary RNFL was imaged with Optical Coherence Tomography (OCT3) and the thickness of the RNFL around the disc was determined in four quadrants with a 3.4 mm circle OCT scan. The influence of age and gender was evaluated on various parameters using unpaired t test, Pearson's correlation coefficient and ANOVA. RESULTS: The sample included 66 males and 84 females. The mean age of the study sample was 42.64 +/-13.63 years. The average RNFL thickness was 101.07 +/- 10.13µm with the maximum thickness in the inferior quadrant (127.47±15.57) followed by the superior, nasal and temporal quadrants. The difference between the inferior and superior quadrants was statistically significant (p less than 0.001). There was no significant difference in RNFL thickness between males and females. Negative correlation was found between age and average RNFL thickness, superior and temporal average (Pearson's correlation value = -0.262, - 0.209, - 0.294 respectively and p = 0.02, 0.04, 0.001 respectively). CONCLUSION: The present study provides additional data on the existing database of RNFL thickness in Asian Indians. It is also evident that RNFL thickness decreases with age but there is no relationship with gender.

Fixed-diameter scan protocol preferable for retinal nerve fibre layer measurement by optical coherence tomography in all sizes of optic discs.

BACKGROUND: Retinal nerve fibre layer (RNFL) measurements using a fixed-diameter versus a user-defined scan-protocol of optical coherence tomography (Stratus OCT) were compared in 32 normal, 62 glaucoma suspects and 36 glaucomatous eyes. METHODS: Peripapillary RNFL thickness was measured using the standard "fast" RNFL scan-protocol and proportional 2.27 x disc scan protocol. Disc size was measured using the "fast" optic disc protocol. The correlation between RNFL thickness for each scan-protocol and disc size was analysed. RESULTS: In normal eyes, RNFL thickness was independent of the optic-disc area using the fixed-diameter protocol (p = 0.92) but was inversely proportional to disc size using the proportional protocol (p<0.001). In glaucoma suspects, the optic-disc area correlated with RNFL thickness using the fixed-diameter protocol (p<0.001). In the multivariate analysis in glaucomatous eyes, the RNFL thickness using the fixed-diameter protocol was significantly affected by the mean deviation on visual fields but not by disc area (p<0.001 and p = 0.64 respectively) CONCLUSION: In normal subjects, disc size does not appear to affect RNFL measurements by OCT using the fixed-diameter protocol, thus indicating that RNFL thickness may be related to distance from the centre of the optic disc rather than the margin. The thicker RNFL observed in large glaucomatous discs in this study may be related to the earlier stage of glaucoma, though it may not apply to the general population.