Primary objectives in this investigation of Best's macular dystrophy include: delineation of genetic and clinical characteristics including prognosis and natural history; determination of the diagnostic reliability of EOG ratios; search for genetic linkage; characterization of retinal function parameters; search for metabolic and basic genetic abnormalities; and exploration of possible therapeutic measures. Thus far, 13 pedigrees of Best's macular dystrophy have been ascertained, containing nearly 500 living members. Attempts will be made to study each of these individuals using the EOG and genealogical relationships as the primary means of detection and affected individuals will be studied further with fundus photography, fluorescein angiography, ERG's, and dark adaptation as well as by serial clinical examinations. Blood and saliva will be collected from all family members for linkage analysis. A core group of approximately 50 individuals will be followed at repeated intervals using clinical examination and fundus photography to delineate the natural history and prognosis of this disease.