Incidence of iris colour change in latanoprost treated eyes

Aims: To determine the incidence of increased iris pigmentation in eyes treated with chronic latanoprost. This is an observational, cohort study. Methods: The anterior segments of both eyes of 43 patients with glaucoma were photographed after unilateral latanoprost therapy. Two independent, masked observers analysed the slides of both eyes of the study participants, and compared the iris pigmentation of both eyes of each patient using a stereo viewer. Results: 30 patients (69.7%) had a definite acquired iridial anisochromia; 15 patients (50%) had increased superficial iris pigmentation with a "granular" appearance (type 1 change), and 15 patients (50%) had an increased "stromal pigmentation" - that is, the affected iris appeared darker than the fellow eye, but without a "granular" appearance (type 2 change). Conclusion: The incidence of increased iris pigmentation induced by latanoprost is much higher than previously reported. The high prevalence of mixed iris colour found in this population and the fact that the patients studied were undergoing unilateral therapy may explain these results.