Risk Factors for Flat Anterior Chamber Requiring Intervention After Glaucoma Drainage Implant: A Retrospective Case-Controlled Study

PURPOSE: To identify risk factors for flat anterior chamber that required additional intervention in the postoperative period (90 days) after uncomplicated Baerveldt Glaucoma Implant (BGI) surgery. DESIGN: Retrospective, matched case-control study. METHODS: A total of 42 cases (eyes) that received BGI at Anne Bates Leach Eye Hospital between February 1, 2011, and January 1, 2019, and that developed flat anterior chamber were included. For each case, we matched 2 controls (84). Variables included sex, diagnosis, diabetes, hypertension, pre- and postoperative glaucoma medications, ocular conditions, and intraocular pressure (IOP). Multivariable conditional logistic regression determined odds ratios (ORs) for independent predictors. RESULTS: Case patients were more likely to be female (69.1% case patients/41.7% controls), to have a history of taking oral carbonic anhydrase inhibitors (CAIs) at tube opening (21.4%/7.1%), to be of another race/ethnicity (11.9%/0.0%), and to have pseudoexfoliation (23.8%/6.0%), and were less likely to be using cholinergic agonists (0.0%/11.9%) at baseline and to have primary open angle glaucoma (42.9%/64.3%). Case patients had greater mean age (75.9/64.9 years), earlier tube opening time (5.6/6.2 weeks), and lower IOP after tube opening (7.2/14.4 mm Hg), but IOP before opening was higher (24.7/19.5 mm Hg). We identified 3 independent predictors: older age (10-year increase OR = 3.59, P <.0001), oral CAI use at tube opening (OR = 5.65, P =.009), and higher IOP prior to tube opening (3 mm Hg increase OR = 1.30, P =.018). CONCLUSION: Risk factors for flat anterior chamber were older age, oral CAIs at tube opening, and higher IOP before tube opening. Strategies to minimize the acute IOP reduction that preceded this complication such as discontinuing oral CAI prior to tube opening may be considered.