PurposeTo evaluate the differences in posterior capsule opacification (PCO) and visual and optical performance between a microincision intraocular lens (IOL) and a conventional IOL.SettingOphthalmology Department, St. Thomas' Hospital, London, United Kingdom.MethodsPatients with bilateral cataract were prospectively randomized to receive a HumanOptics MC611MI microincision IOL (microlens group) or an Alcon AcrySof MA60AC 3-piece IOL (control group) in either eye and were followed for 24 months. Best corrected visual acuity (BCVA) (logMAR) was measured; PCO was quantified by POCO software analysis of retroillumination images. Aberrations and modulation transfer function (MTF) were measured at the 24-month visit.ResultsThe study enrolled 32 patients. The mean percentage area PCO was greater in the microlens group than in the control group from 3 months onward and was statistically significant from 12 months onward. The greatest difference in PCO between groups was at 24 months: mean 25.45% ± 34.51% (SD) in the microlens group versus 7.82% ± 13.35% in the control group (P = .029). The BCVA in the control group was slightly better at all time points; the difference between groups was statistically significant at 3, 6, and 12 months. No significant difference in aberrations was detected. The MTF curves were comparable for both IOLs.ConclusionsBoth IOLs provided good visual performance. There was no evidence of distortion of the microincision IOL in the capsular bag. The microincision IOL had poorer PCO performance, which was visually significant and was caused by migration of lens epithelial cells through its broad optic–haptic junctions.