Does levodopa improve vision in albinism? Results of a randomized, controlled clinical trial

Background: Dopamine is an intermediate product in the biosynthesis of melanin pigment, which is absent or reduced in albinism. Animal research has shown that supplying a precursor to dopamine, levodopa, may improve visual acuity in albinism by enhancing neural networks. This study examines the safety and effectiveness of levodopa on best-corrected visual acuity in human subjects with albinism. Design: Prospective, randomized, placebo-controlled, double-masked clinical trial conducted at the University of Minnesota. Participants: Forty-five subjects with albinism. Methods: Subjects with albinism were randomly assigned to one of three treatment arms: levodopa 0.76mg/kg with 25% carbidopa, levodopa 0.51mg/kg with 25% carbidopa, or placebo and followed for 20 weeks, with best-corrected visual acuity measured at enrollment, and at weeks 5, 10, 15, and 20 after enrollment. Side-effects were recorded with a symptom survey. Blood was drawn for genotyping. Main Outcome Measures: Side-effects and best-corrected visual acuity 20 weeks after enrolment. Results: All subjects had at least one mutation found in a gene known to cause albinism. Mean age was 14.5 years (range: 3.5 to 57.8 years). Follow up was 100% and compliance was good. Minor side-effects were reported; there were no serious adverse events. There was no statistically significant improvement in best-corrected visual acuity after 20 weeks with either dose of levodopa. Conclusions: Levodopa, in the doses used in this trial and for the time course of administration, did not improve visual acuity in subjects with albinism.