OPA1 and autosomal dominant optic atrophy: ,23 About 57–75 % of ADOA patients carry a variant in the optic atrophy type 1 (OPA1) gene, 1 % of patients a variant in the OPA3 gene, and the rest variants in OPA4, OPA5 or OPA8. 1,24 Genetic deficiency of OPA1 is associated with mitochondrial fragmentation and impaired respiratory capacity, as reported in primary cell cultures of human fibroblasts and murine RGCs.25