Study to Assess Efficacy,Safety and Tolerability of Idebenone in the Treatment of Leber's Hereditary Optic Neuropathy

Inclusion Criteria: * Age \> or = 14 years and \< 65 years * Impaired visual acuity in at least one eye due to LHON * Onset of visual loss due to LHON lies five years or less prior to Baseline * Confirmation of either G11778A, T14484C or G3460A LHON mtDNA mutations at \>60% in blood * No explanation for the visual failure besides LHON * Body weight ≥ 45 kg * Negative urine pregnancy test at Screening and at Baseline (women of childbearing potential). Exclusion Criteria: * Treatment with Coenzyme Q10 or idebenone within 1 month prior to Baseline * Pregnancy and/or breast-feeding * Weekly alcohol intake 35 units (men) or 24 units (women) * Current drug abuse * Clinically significant abnormalities of clinical haematology or biochemistry including, but not limited to, elevations greater than 2 times the upper limit of normal of AST, ALT or creatinine * Participation in another clinical trial of any investigational drug within 3 months prior to Baseline * Other factor that, in the investigator's opinion, excludes the patient from entering the study