BACKGROUND: This study investigates the role of the SLC38A8 gene. SLC38A8 facilitates glutamine influx, which converts to glutamate in the visual pathway. Mutations in SLC38A8 are associated with FHONDA syndrome, a subtype of foveal hypoplasia with congenital nystagmus and optic-nerve-decussation defects without pigmentation leading to severe vision loss. METHODS: In vivo and in vitro methods were conducted using retinal cell lines overexpressing SLC38A8, and Slc38a8/Slc38a7 gene-edited mice to evaluate visual function and physiological changes. Statistical analyses included two-way ANOVA, multiple regression, and ANCOVA. RESULTS: In vitro, SLC38A8 overexpression influenced retinal gene expression, light detection, and visual perception, as well as glutamine and glutamate dynamics. In Y79 CONCLUSIONS: Our findings underscore SLC38A8 role in retinal function and glutamine-glutamate metabolism, with clinical implications for FHONDA and potential future dietary intervention targeting glutamine or glutamate.