Bleb Morphology After Mitomycin-C Augmented Trabeculectomy – Comparison between Clinical Evaluation and Anterior Segment Optical Coherence Tomography


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Abstract

Purpose:To study the longitudinal correlation between the clinical morphological appearance of filtering blebs with anterior segment optical coherence tomography (AS-OCT) in the early postoperative period.Methods:Thirty eyes of 30 glaucoma patients scheduled for first-time trabeculectomy with mitomycin C 0.02% were consecutively enrolled. The filtering blebs were evaluated clinically according to a grading system and with AS-OCT at day 1 and weeks 1, 2, 3, 4 and 12 following surgery. Bleb wall thickness (BWT) and bleb cavity height (BCH) were analyzed by means of horizontal and vertical AS-OCT-scans.Results:Nineteen eyes (63%) had functioning blebs without any further surgical intervention. IOP changed from 18.4±1.3▒mm Hg with preoperatively applied glaucoma medication to a mean of 9.75±1.4▒mm Hg at all follow-ups postoperatively without medication. Mean BWT during follow-up was 575±47▒μm; mean BCH was 295±72▒μm. Nine filtering blebs (30%) showed encapsulation requiring a bleb needling. This was recognized clinically at week 3 in four, and at week 4 in five cases. The tendency towards encapsulation was seen much earlier with AS-OCT, already showing a statistically thinner BWT (P=0.036) at week 1 and a higher BCH (P=0.005) at week 2 post-surgery, compared to the group with functioning blebs. As of week 3, IOP increased and was statistically significantly higher (P=0.016) compared to the group with functioning blebs. Two patients (7%) showed early scarring.Conclusion:AS-OCT allows an analysis of the clinically invisible deeper layers of the filtering bleb. Characteristics of encapsulation, like higher blebs with thinner bleb walls, are sooner recognized than the clinical appearance. This might benefit the management of the postoperative period after trabeculectomy and the long-term outcome.

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