Specialized tests, e.g., toxin screens and serum B12 for toxic optic neuropathy; markers for autoimmune diseases; antibody to aquaporin-4 and MRI spine in NMO; genetic analysis for mitochondrial mutation in cases of Leber’s hereditary optic neuropathy, are required in suspected conditions. This evidence concerns the gene AQP4 and Leber hereditary optic neuropathy.