It is currently unclear how much of the B vitamin production by gut microbiota is accessible by the host; however, our results suggest that microbial modulation, combined with dietary or pharmacological supplementation of B vitamin levels to modulate retinal RPE65 expression, could have potential therapeutic value in the treatment of retinal diseases and in general maintenance of eye health in old age. The gene discussed is RPE65; the disease is Abnormal retinal morphology.