Orphanet rare-disease nomenclature entry Orphanet_1243 (Best vitelliform macular dystrophy) (BVMD) is a genetic macular dystrophy characterized by loss of central visual acuity, metamorphopsia and a decrease in the Arden ratio secondary to an egg yolk-like lesion located in the foveal or parafoveal region. Also known as: BMD, BVMD, Best disease, Best macular dystrophy, Early-onset vitelliform macular dystrophy, Juvenile-onset vitelliform macular dystrophy, Polymorphic vitelline macular degeneration, Vitelliform macular dystrophy type 2.