Intraocular Pressure Reduction after Phacoemulsification versus Manual Small-Incision Cataract Surgery: A Randomized Controlled Trial

Abstract

To compare reduction in intraocular pressure (IOP) and change in anterior chamber angle configuration between eyes undergoing phacoemulsification versus those undergoing manual small-incision cataract surgery (MSICS). Prospective, randomized, double-masked, parallel assignment clinical trial. Five hundred eyes of 500 participants 40 to 70 years of age with normal IOP, gonioscopically open angles, and age-related cataract. Eyes underwent phacoemulsification or MSICS after a 1:1 randomization and allocation code. Best-corrected vision, IOP, comprehensive slit-lamp evaluation, and anterior segment (AS) optical coherence tomography (OCT) were performed at baseline and at 1, 3, and 6 months follow-up. Change in IOP (ΔIOP) and AS OCT parameters between baseline and 6 months after surgery. Six months, similar IOP reduction was observed in eyes undergoing phacoemulsification (ΔIOP=2.7±2.9 mmHg) and MSICS (ΔIOP= 2.6±2.6 mmHg; P= 0.70). Widening of the angle opening distance (AOD) 500 μm from the scleral spur (median ΔAOD500= 103 μm; interquartile range= 39-179 μm) was also similar in both groups (P= 0.28). Multivariate linear regression analysis showed that eyes with higher baseline IOP experienced significantly greater reduction in IOP at 6 months (ΔIOP= 0.46-mmHg reduction for every 1-mmHg increment in baseline IOP; 95% confidence interval [CI], 0.4-0.5 mmHg; P < 0.001). After adjusting for covariates, the magnitude of widening of AOD500 was not associated significantly with reduction in IOP (1.33-mmHg reduction for every 1-mm increment in AOD500; P= 0.07). Baseline AOD500 (β=-0.60-mm change/1-mm increment of baseline AOD; 95% CI,-0.67 to-0.53 mm) and anterior chamber depth (β= 0.07-mm change/1-mm increment of baseline anterior chamber depth; 95% CI, 0.04-0.1 mm) were significant predictors of AOD500 widening at 6 months. Both phacoemulsification and MSICS led to significant and similar IOP reductions 6 months after surgery, and both surgeries produced similar changes in anterior chamber and angle parameters. Higher baseline IOP was associated with greater IOP reduction; IOP reduction also can be attributed partly to changes in angle and anterior chamber configuration, although these parameters were unable to predict significantly predict IOP drop at 6 months.