Coarsened Exact Matching of Phaco-Trabectome to Trabectome in Phakic Patients: Lack of Additional Pressure Reduction from Phacoemulsification

PURPOSE: To compare intraocular pressure (IOP) after trabectome-mediated ab interno trabeculectomy surgery in phakic patients (T) and trabectome with same session phacoemulsification (PT) using Coarsened Exact Matching. Although phacoemulsification is associated with IOP reduction when performed on its own, it is not known how much it contributes in PT. METHODS: Subjects were divided into phakic T and PT. Exclusion criteria were follow-up for <12 months and additional glaucoma surgery. Demographics were compared by the Mann-Whitney U test and chi-squared test for continuous and categorical variables, respectively. Multiple imputation was utilized to avoid eliminating data with missing values. Groups were then matched using Coarsened Exact Matching based on age, race, type of glaucoma, baseline IOP, and number of preoperative glaucoma medications. Univariate linear regression was used to examine IOP reduction after surgery; those variables that were statistically significant were included in the final multivariate regression model. RESULTS: A total of 753 cases were included (T: 255, PT: 498). When all variables except for age were kept constant, there was an additional IOP reduction of 0.05±0.01 mmHg conferred for every yearly increment in age. Every 1 mmHg increase in baseline IOP correlated to an additional IOP reduction of 0.80±0.02 mmHg. Phacoemulsification was not found to be a statistically significant contributor to IOP when comparing T and PT (p≥0.05). T had a 21% IOP reduction to 15.9±3.5 mmHg (p<0.01) while PT had an 18% reduction to 15.5±3.6 mmHg (p<0.01). Number of medications decreased (p<0.01) in both groups from 2.4±1.2 to 1.9±1.3 and from 2.3±1.1 to 1.7±1.3, respectively. CONCLUSION: Phacoemulsification does not make a significant contribution to postoperative IOP or number of medications when combined with trabectome surgery in phakic patients.