GDF15 and Leber hereditary optic neuropathy: Serum glial fibrillary acidic protein, neurofilament light chain and Growth/differentiation factor-15s were increased in the chronic stage of Leber hereditary optic neuropathy and autosomal-dominant optic atrophy, suggesting an ongoing neurodegeneration in both optic neuropathies with a role for optic nerve head astrocytes in this process.