Evaluation of Conjunctival Bleb Detection After Vitrectomy by Ultrasound Biomicroscopy, Optical Coherence Tomography and Direct Visualization

Abstract

Purpose: To compare ultrasound biomicroscopy (UBM), anterior-segment optical coherence tomography (AS-OCT), and direct visualization for detecting conjunctival blebs in sutureless sclerotomies after vitrectomy. Conjunctival blebs are formed by sclerotomy leakage due to incompetent closure.Methods: Experimental, randomized, and observer-masked study in which 23-gauge vitrectomies were performed in cadaveric pig eyes. Postoperative conjunctival blebs were assessed by UBM, AS-OCT, and direct visualization. No conjunctival blebs were classified as Grade 0 (G0), thin blebs (less than or equal to one-half of scleral thickness) as Grade 1 (G1) and thick blebs (greater than one-half of scleral thickness) as Grade 2 (G2).Results: Fifty pig eyes were included. Conjunctival blebs were found in 13.3% (8% G1, 5.3% G2) of the incisions analyzed by UBM, in 20% (14.7% G1, 5.3% G2) of the sclerotomies studied by AS-OCT, and in 7.3% (2% G1, 5.3% G2) of the wounds evaluated by direct visualization. AS-OCT was the most sensitive method for identifying conjunctival blebs when compared with UBM and direct visualization (p < 0.001). In turn, UBM was better than direct visualization for observing sclerotomy blebs (p = 0.004).Conclusions: AS-OCT is the most sensitive technique for detecting subclinical blebs (G1) and thus, it may be useful in research for studying the influence that surgical factors and maneuvers may exert on sclerotomy closure capacity after vitrectomy. Direct visualization, that is used in routine clinical practice to determine which sclerotomies should be sutured, is useful only to identify thick blebs (G2) after vitrectomy.