If patients with onset after preschool age exhibit optic nerve edema or tortuous vessels as well as optic nerve atrophy with thickening of the nasal and superior quadrants of the RNFL, then the primary LHON-related mtDNA mutation sites should be screened first, followed analysis of OPA1. (3) When neither OPA1 nor primary LHON-related mtDNA mutations were found in these patients, the coding regions of OPA3 were subsequently sequenced. This evidence concerns the gene OPA3 and Leber hereditary optic neuropathy.