Optical coherence tomography assessment of retinal nerve fiber layer thickness changes after glaucoma surgery.

Abstract

To assess changes in retinal nerve fiber layer (NFL) thickness in glaucoma patients after filtration surgery by using optical coherence tomography (OCT). Retrospective observational case series. Thirty-eight eyes of 31 glaucoma patients who underwent trabeculectomy or a combined procedure of cataract extraction and trabeculectomy were evaluated retrospectively. Eyes were imaged with OCT before surgery (1 week to 6 months before surgery; mean +/- standard deviation [SD], 71.3 +/- 61.2 days) and after surgery (6-12 months after surgery; 247.2 +/- 63.5 days) to measure peripapillary NFL thickness. Changes in mean and segmental NFL thickness with respect to age, postoperative change in intraocular pressure (IOP), preoperative visual field test global indices, and change in visual field global indices. A significant increase in the overall mean NFL thickness was present after surgery (P < 0.0001). Segmental analysis found a significant increase in NFL thickness in the nasal, superior, and temporal quadrants. IOP decreased after surgery from 22.0 +/- 6.4 mmHg to 11.4 +/- 4.7 mmHg (mean +/- SD). Twenty-eight (73.7%) of 38 eyes had an IOP reduction >30%. The mean NFL thickness increase (0.5- microm/mmHg decrease of IOP) was significantly correlated with the IOP reduction (r = -0.41; P = 0.03). No correlation was found between NFL thickness changes and age, preoperative visual field global indices, or change in visual field global indices. A significant increase of the mean NFL thickness, which was related to IOP reduction, was detected after glaucoma filtration surgery.