PURPOSE: To test a topical agent with purported antiapoptotic properties as prophylactic treatment after first eye involvement in Leber hereditary optic neuropathy (LHON), a maternally-inherited disorder characterized by bilateral, often sequential, visual loss. DESIGN: Open labeled, nonrandomized prospective pilot study.METHODS: Nine primary mutation molecularly confirmed LHON patients with one eye vision loss for less than 6 months and normal visual function in the fellow eye were treated with brimonidine purite 0.15% (Alphagan P) 4 times daily in the unaffected eye for up to 2 years. Visual acuity was the primary efficacy outcome. Secondary measures included changes on automated perimetry and quantification of the relative afferent pupillary defect. RESULTS: There were 8 men and 1 woman enrolled, aged 13 to 54 years (mean 32 years), eight with the 11778 mitochondrial DNA (mtDNA) mutation, and one with the 3460 mutation. Despite normal visual acuity at baseline in all patients, 7 patients had some minimal changes in the central visual field of the study eye. All patients had deterioration of vision in their second eye. In 1 of the 2 patients who had treatment initiated within 16 days after first eye involvement, good visual acuity was maintained in the study eye at 15 month followup, despite a mildly abnormal study eye baseline visual field. CONCLUSIONS: LHON may be a bilateral condition at onset more frequently than appreciated, with asymmetric severity at presentation. Topical brimonidine purite in this dosage was unsuccessful in preventing second eye involvement in recently monocularly-symptomatic LHON. PURPOSE: To test a topical agent with purported antiapoptotic properties as prophylactic treatment after first eye involvement in Leber hereditary optic neuropathy (LHON), a maternally-inherited disorder characterized by bilateral, often sequential, visual loss. DESIGN: Open labeled, nonrandomized prospective pilot study.METHODS: Nine primary mutation molecularly confirmed LHON patients with one eye vision loss for less than 6 months and normal visual function in the fellow eye were treated with brimonidine purite 0.15% (Alphagan P) 4 times daily in the unaffected eye for up to 2 years. Visual acuity was the primary efficacy outcome. Secondary measures included changes on automated perimetry and quantification of the relative afferent pupillary defect. RESULTS: There were 8 men and 1 woman enrolled, aged 13 to 54 years (mean 32 years), eight with the 11778 mitochondrial DNA (mtDNA) mutation, and one with the 3460 mutation. Despite normal visual acuity at baseline in all patients, 7 pat All patients had deterioration of vision in their second eye. In 1 of the 2 patients who had treatment initiated within 16 days after first eye involvement, good visual acuity was maintained in the study eye at 15 month followup, despite a mildly abnormal eye eye baseline visual field. CONCLUSIONS: LHON may be a bilateral condition at onset more frequently than appreciated, with asymmetric severity at presentation. Topical brimonidine purite in this dosage was unsuccessful in preventing second eye involvement in recently monocularly-symptomatic LHON.