Ab Interno Automated Trephination For Failed Filtering Blebs: Long–Term Follow–Up

Abstract

Abstract: : Purpose: To evaluate the effectiveness of ab interno bleb revision using an automated trephine in rescuing failed filtering blebs. Methods: We treated 40 failed blebs of 38 patients between 1995 and 2003. Blebs treated were previously functioning, mature, cystic, and well defined. Patients were included if they had had previous trabeculectomy with or without anti–metabolites and a post–trephination follow–up period of at least 3 months. Results: Mean age was 69.2 years (range 36–88). Mean follow–up was 32.3 months (range 3–96). Mean time between trabeculectomy and trephination was 58.3 months (range 2–194). 31 eyes received anti–metabolites (5–FU) either at the time of trephination or post–operatively. 

We defined success as IOP ≤ 21 mmHg and at least 20% reduction from baseline on the same or fewer number of pre–trephination medications, 30/40 eyes (75%) fit the criteria for success over the course of follow–up. Among all 40 eyes with ≥ 3 months of follow–up there was a significant drop in IOP from pre–trephination to 3 months (p < 0.001), after which generalized estimating equations with random effects indicated that the average trend in IOP with time was negative, but not significant (p = 0.2). The percentage of patients requiring ≥ 2 medications declined from 90% at pre–trephination to 21% at 3 months (p < 0.0001 by Fisher’s exact test), and was stable thereafter (p from Mantel’s test for trend = 0.96). Some patients were able to eliminate all medications. Patients who did not meet the criteria of success regained successful IOP control with other modalities of management including medical treatment and bleb needling. One eye required a trabeculectomy revision and two eyes required artificial drainage shunts. Complications were few. Conclusion: Ab interno trephination is a useful modality for rescuing selected failed filtering blebs.

Keywords: clinical (human) or epidemiologic studies: systems/equipment/techniques • intraocular pressure • outflow: trabecular meshwork