Occult retinal dysfunction

It has been reported that there are several retinal dysfunctions without any visible fundus abnormality. Occult retinal dysfunctions are divided into two groups, localized and diffuse. The localized group includes acute zonal occult outer retinopathy and occult macular dystrophy. The diffuse group includes congenital stationary night blindness, cone dystrophy without fundus abnormality, drug toxicity, Creutzfeldt-Jacob disease and cone dyssfunction syndromes. Retinal function tests are essential for diagnosing these diseases. Both the full-field electroretinogram (ERG), which is especially helpful for separating rod and cone functions, and the focal ERG are very useful in the diagnostic processes.