NDUFS2 and retinal degeneration: Previous studies have indicated that variants in SSBP1, ACO2, RTN4IP1, NBAS, OPA3 and FDXR could manifest a concurrent occurrence of retinal degeneration in the fundus along with optic atrophy.15,16,40-45 Biallelic mutations in nuclear genes such as DNAJC30, NDUFS2, NDUFAF5, NDUFA12, MECR and MCAT have been identified in unsolved cases with typical LHON-like phenotypes.10-14 However, the systematic summary of the fundus characteristics of nHON is limited.