PURPOSE: To compare posterior capsule opacification (PCO) after phacoemulsification and implantation of heparin-surface-modified (HSM) poly(methyl methacrylate) (PMMA) intraocular lenses (IOLs) in the capsular bag in patients with diabetes mellitus with that in a control group. SETTING: St. Erik's Eye Hospital, Stockholm, Sweden. METHODS: This prospective study comprised 26 patients with diabetes mellitus and 26 control patients without diabetes. Those with glaucoma, exfoliation syndrome, uveitis, and pupil size smaller than 6.0 mm after dilation were excluded. All patients received the same standardized phacoemulsification procedure with implantation of an HSM PMMA IOL in the capsular bag. Posterior capsule opacification was scored 1 and 2 years after surgery by evaluating retroillumination images taken with a Scheimpflug camera (Nidek Anterior Eye Segment Analysis System) after pupil dilation with phenylephrine 10% and cyclopentolate 1%. The PCO density behind the IOL optic was graded clinically from 0 to 4 (0 = none, 1 = minimal, 2 = mild, 3 = moderate, 4 = severe) and scored using the Evaluation of Posterior Capsule Opacification medical software developing system. RESULTS: No differences in PCO were found between the diabetic and control groups 1 year after surgery. The total PCO score was significantly less in diabetic than in control eyes 2 years after surgery (P