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

Importance: The role of the filtration bleb for IOP management following trabeculectomy (TRAB) and deep sclerectomy (DS) in glaucoma is highlighted in this study.

Background: 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.

Design: The retrospective study was performed by a single surgeon.

Participants: Twenty-eight patients with open-angle glaucoma were recruited into the study, 14 in each of the TRAB (fornix) and DS groups.

Methods: The surgical intervention was dependent on the irido-corneal angle configuration on gonioscopy.

Main outcome measures: 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.

Results: 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.

Conclusions and relevance: 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.