The Effect of Phacoemulsification on Intraocular Pressure in Eyes with Preexisting Glaucoma Drainage Implants

Purpose: To study the effect of phacoemulsification on intraocular pressure (IOP) control in patients with preexisting glaucoma drainage implants (GDIs). Design: Retrospective, observational case series. Participants: A total of 45 patients (51 eyes) with previously placed GDIs who underwent phacoemulsification between January 2013 and March 2018. Methods: The list of patients was obtained from billing records. Clinical data were retrieved from the corresponding electronic medical records. Main Outcome Measures: Intraocular pressure, number of glaucoma medications before and after phacoemulsification (postoperative day 1, week 1, months 1, 3, 6, 12, 18, and 24), rate of failure (failure defined as IOP >18 mmHg and IOP increase >20% at 2 consecutive visits after month 1, need for additional glaucoma surgery, or loss of light perception vision), and postoperative complications. Results: Mean follow-up was 23.0 ± 11.1 months. The average interval between GDI surgery and phacoemulsification was 9.4 ± 6.7 months. An Ahmed glaucoma valve (AGV; New World Medical) was implanted in 12 eyes, a Baerveldt glaucoma implant (BGI; Johnson & Johnson Surgical Vision) was implanted in 36 eyes, and a Molteno (Molteno Ophthalmic Limited) glaucoma implant was implanted in 3 eyes. Before phacoemulsification, the mean IOP was 14.4 ± 4.4 mmHg on 2.1 ± 1.3 glaucoma medications. At postoperative month 24, the mean IOP was 12.6 ± 4.4 mmHg (n = 29, P = 0.519) on 2.0 ± 1.6 (P = 0.457) glaucoma medications. The reduction in IOP was significant only at postoperative week 1 (P = 0.031). The cumulative failure rate was 3.9% at 1 year and 11.8% at 2 years. The AGV group had a significantly higher mean IOP before phacoemulsification than the BGI group (P = 0.016). Analysis of covariance, taking the baseline IOP as a covariate, revealed no differences in postoperative IOP and number of glaucoma medications between groups, except for month 18 (1 patient in the BGI group had uncontrolled IOP requiring surgery). Postoperative complications included cystoid macular edema (10%), corneal decompensation (6%), and choroidal effusion (4%). Conclusions: Phacoemulsification after GDI surgery resulted in a transient reduction in IOP at postoperative week 1. Patients with previously placed AGVs had similar postoperative outcomes compared with those with BGIs.