OCCULT MACULAR DYSTROPHY

PURPOSE: Occult macular dystrophy is a hereditary macular dystrophy wi thout any visible abnormality of the fundus or abnormality indicated b y fluorescein angiography even when visual acuity is decreased. Normal full-field electroretinogram in both cone and rod components with abn ormal focal macular cone electroretinogram is the key to diagnosing th is disorder. The purpose of this study was to identify the function of the macular rods and to provide detailed clinical findings in occult macular dystrophy. METHODS: Thirteen patients from eight families were examined. The fundi of 12 patients were essentially normal (occult ma cular dystrophy), and the oldest patient in one family disclosed bull' s eye maculopathy. In the 12 patients, including the patient with bull 's eye maculopathy, the profiles of cone and rod absolute thresholds w ere performed across the 60-degree horizontal meridian of the posterio r pole. RESULTS: All 12 patients showed cone sensitivity loss only in the macular area. Six relatively young patients revealed normal rod se nsitivity, whereas six older patients showed borderline rod sensitivit y or abnormal rod sensitivity in the macular area. CONCLUSIONS: The pa thology of occult dystrophy involves either only the macular cone syst em or macular cone and rod systems without any visible abnormality. Th is difference of the pathology suggests a different clinical entity or a different stage of occult macular dystrophy.