Effect of Trabeculectomy on OCT Measurements of the Optic Nerve Head Neuroretinal Rim Tissue

Purpose: Ophthalmologists commonly perform glaucoma surgery to treat progressive glaucoma. Few studies have examined the stability of OCT neuroretinal rim parameters after glaucoma surgery for ongoing detection of glaucoma progression. Design: Longitudinal cohort study. Participants: Twenty eyes (16 participants) with primary open-angle glaucoma who had undergone trabeculectomy. Methods: We calculated the change in OCT parameters (minimum rim area [MRA], minimum rim width [MRW], Bruch's membrane opening [BMO] area, mean cup depth [MCD], anterior lamina cribrosa surface depth [ALCSD], prelaminar tissue thickness, retinal nerve fiber layer thickness [RFNLT]) during an interval from the visit before the surgery to the visit after the surgery, a span of approximately 6 months. We also calculated changes in the same eyes over 2 separate 6-month intervals during which trabeculectomy did not occur to serve as a control. We compared these intervals using a generalized linear model (with compound symmetry correlation structure), accounting for the correlation between intervals for the same eye. Main Outcomes Measures: Minimum rim width, MRA, angle above the reference plane for MRW and MRA, BMO area, MCD, mean ALCSD, prelaminar tissue thickness, RNFLT, and visual field parameters (mean deviation, pattern standard deviation, and visual field index). Results: The intervals during which trabeculectomy occurred showed a significant decrease in intraocular pressure (-9.2 mmHg; P < 0.001) when compared with control intervals. Likewise, the following neuroretinal rim parameters showed significant changes with trabeculectomy: increased MRW (+6.04 mu m; P = 0.001), increased MRA (+0.014 mm(2); P = 0.024), increased angle above reference plane of MRW (+2.64 degrees; P < 0.001), decreased MCD (-24.2 mu m; P = <0.001), and decreased mean ALCSD (-18.91 mu m; P = 0.006). This is consistent with an increase in rim tissue thickness and a more anterior position of the internal limiting membrane and ALCS relative to the BMO plane. Conversely, RNFLT change was not significantly different between trabeculectomy and control intervals (P = 0.37). Conclusions: Trabeculectomy resulted in anatomic changes to the optic nerve head rim associated with reduced glaucomatous cupping. The RNFLT may be amore stablemeasure of disease progression that clinicians can use to monitor across intervals in which glaucoma surgery occurs. (C) 2019 by the American Academy of Ophthalmology