OBJECTIVE: To evaluate clinical features of patients related to opacification of hydrophilic acrylic intraocular lenses, four years after surgery. METHODS: We evaluated six cases of late opacification of Ioflex intraocular lenses (case group) compared to 24 patients (control group) with no opacification. Both groups underwent phacoemulsification as a result of a community campaign for underprivileged people. Patients who underwent bilateral cataract surgery had only the right eye included on the study. The patients were submitted to ophthalmic examination, including measurements of corrected distance visual acuity and biomicroscopy slitlamp evaluation. Detailed medical histories were obtained. Surgical details were retrieved. RESULTS: Systemic arterial hypertension was recorded in 4 patients from the case group and 11 in the control group, with no statistically significant difference between groups. A single patient in the control group had diabetes mellitus, and so was not considered for statistical analysis. No environmental factor could be related. There were no statistically significant differences for mean visual acuity between the groups of patients regarding the evaluation periods. One eye in the control group received an Ioflex intraocular lens with the same lot number as one of the opacified lenses. CONCLUSION: No clear patient factor could be related to late Ioflex lens opacification.