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

BackgroundDopamine 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. DesignProspective, randomized, placebo-controlled, double-masked clinical trial conducted at the University of Minnesota. ParticipantsForty-five subjects with albinism. MethodsSubjects 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 MeasuresSide-effects and best-corrected visual acuity 20 weeks after enrolment. ResultsAll 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. ConclusionsLevodopa, in the doses used in this trial and for the time course of administration, did not improve visual acuity in subjects with albinism.