Comparison of bleb morphology between trabeculectomy and deep sclerectomy using a clinical grading scale and anterior segment optical coherence tomography

Abstract

The role of the filtration bleb for IOP management following trabeculectomy (TRAB) and deep sclerectomy (DS) in glaucoma is highlighted in this study. This study serves to analyse the bleb morphology and IOP using the Indiana Bleb Appearance Grading Scale (IBAGS) and the anterior-segment optical coherence tomography (AS-OCT) postoperatively and at 3 months. The retrospective study was performed by a single surgeon. Twenty-eight patients with open-angle glaucoma were recruited into the study, 14 in each of the TRAB (fornix) and DS groups. The surgical intervention was dependent on the irido-corneal angle configuration on gonioscopy. Pre-operatively, we collected visual acuity, medications and IOP. Three months postoperatively, we used the IBAGS to assess bleb morphology, including bleb height, extent, vascularity and leak. AS-OCT was also used to assess bleb height, thickness, cyst presence and posterior and intrascleral fluid. Central corneal thickness and mean IOP at 3 months postoperatively were significantly lower in the TRAB group (7.75 vs. 12.27 mmHg; P = 0.005). Blebs that were significantly higher, broader and less vascular compared with DS were displayed by TRAB eyes. The AS-OCT measurements confirmed TRAB eyes had significantly higher blebs and increased intrascleral fluid compared with DS eyes. Significant differences in bleb morphology, correlating with improved IOP outcomes in TRAB eyes compared with DS eyes in patients with open-angle glaucoma, were showed by both the IBAGS and AS-OCT. Despite the limitations of each classification system, a higher bleb with an increased aqueous reservoir is associated with optimal IOP results.