Purpose:To study the effect of capsular bag irrigation of trypan blue dye (0.06%) on posterior capsular opacification (PCO) in eyes undergoing phacoemulsification.Methods:This was a randomized, trial conducted at a tertiary eye care center in central India. The study included 50 patients (100 eyes) with senile cataracts who were scheduled for phacoemulsification and intraocular lens (IOL) implantation and were willing to undergo bilateral cataract surgery. One eye of each patient was randomized to one of two groups. The dye group received 0.2 ml of trypan blue injected in the capsular bag after cortical cleanup under air. The control group (other eye of the same patient) received 0.2 ml of balanced salt solution injected in a similar manner. PCO in the central 3 mm area of IOL optic was analyzed by a masked observer using an evaluation of PCO software computer analysis system at 6, 12, 24, and 36 months.Results:The average age of patients was 62.05 ± 6.22 in the dye group and 64.92 ± 7.16 years in the control group. The mean PCO score at 6 months was significantly lower in the dye group (0.10 ± 0.15) than in the control group (0.22 ± 0.30). There were no significant differences in the PCO scores between the two groups from 12 to 36 months. At the end of 3 years, eight eyes in the dye group and seven in the control group required YAG capsulotomy (P = 0.21).Conclusion:Capsular bag irrigation of trypan blue dye decreased the PCO score at 6 months, but it had no effect at 36 months.