The effect of phacoemulsification on intraocular pressure in eyes with pre-existing glaucoma drainage implants.

Abstract Purpose To study the effect of phacoemulsification on intraocular pressure (IOP) control in patients with pre-existing glaucoma drainage implants (GDIs). Design Retrospective observational case series Subjects 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 IOP, 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 mm Hg and an IOP increase >20% at two 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) was implanted in 12 eyes, a Baerveldt glaucoma implant (BGI) in 36 eyes, and a Molteno glaucoma implant (MGI) in 3 eyes. Prior to phacoemulsification, the mean IOP was 14.4 ± 4.4 mm Hg on 2.1 ± 1.3 glaucoma medications. At postoperative month 24, the mean IOP was 12.6 ± 4.4 mm Hg (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 prior to phacoemulsification than the BGI group (P = 0.016). ANCOVA analysis, taking the baseline IOP as a covariate, revealed no differences in postoperative IOP and number of glaucoma medications between groups, except for month 18 (one 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 following 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.