A case of occult macular dystrophy

Background: In 1996, Miyake and colleagues proposed a new type of hereditary macular dystrophy in which visual acuity is abnormal, rod and cone electroretinograms (ERGs) are normal, and ophthalmoscopic and angiographic fundus findings are normal, but focal macular and multifocal (mf) ERGs are abnormal; they named this new type of hereditary macular dystrophy "occult macular dystrophy". Case Report: A 21-year-old female with a history of progressive decrease of vision in both eyes over the past 3 to 4 years was examined. Her corrected visual acuity was 0.3 in both eyes. Funduscopy and fluorescein angiography showed no abnormality. Scotopic, bright-flash, photopic, and 30-Hz flicker full-field ERGs were normal. There were, however, decreased local responses in the central area on multifocal ERG (mfERG). Her color vision, implicit time of mfERG, and visual fields were normal. Conclusions: We diagnosed occult macular dystrophy in this case. Considering previous reports, this case seems to represent the early stage of the disease, because the patient was relatively young and had no visual dysfunction other than impaired visual acuity and abnormal mfERG responses.