Importance: Retinitis pigmentosa (RP) is the leading cause of incurable inherited blindness in the developed world, with an estimated prevalence of 1 in 3500 individuals. Therefore, it is important to develop new treatments for this disease.
Objective: To determine the effect of oral treatment with 9-cis β-carotene on visual function of patients with RP.
Design: Randomized, double-masked, placebo-controlled, crossover clinical trial.
Setting: University tertiary medical facility.
Participants: Thirty-four patients with RP who were at least 18 years of age. Twenty-nine patients completed the study and were included in the analysis.
Interventions: Patients were treated daily for 90 days with capsules containing 300 mg of 9-cis β-carotene-ich alga Dunaliella bardawil (β-carotene, approximately 20 mg) or placebo (starch). Following a 90-day washout period, they were treated for 90 days with the other capsules.
Main outcomes and measures: The primary outcomewas the change for both eyes from baseline to the end of each treatment in dark-adapted maximal electroretinographic b-wave amplitude. The secondary outcomes were the changes in light-adapted maximal b-wave amplitude, dark- and light-adapted visual field, and best-corrected visual acuity.
Results: The mean change in dark-adapted maximal b-wave amplitude relative to initial baseline was +8.4 μV for 9-cis β-carotene vs −.9 μV for placebo (P = .001). Ten participants (34.5%) had an increase of more than 10 μV for both eyes (range, 11-42 μV) after 9-cis β-carotene treatment compared with no participants after placebo treatment. The percentage change in light-adapted b-wave response was +17.8%for 9-cis β-carotene vs −.0% for placebo (P = .01). No significant differences were found between the groups for visual field and best-corrected visual acuity. No adverse effects were observed.
Conclusions and relevance: Treatment with 9-cis β-carotene significantly increased retinal function in patients with RP under the tested conditions. The optimal therapeutic regimen will be determined in future, larger clinical trials. 9-cis β-Carotene may represent a new therapeutic approach for some patients with RP.
Trial registration: clinicaltrials.gov Identifier: NCT01256697.