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

Abstract

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. 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. 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. 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.