Fig. 29. Electroretinogram (ERG) responses in early retinitis pigmentosa and congenital stationary night blindness (CSNB). Responses in retinitis pigmentosa are typically small or nonrecordable under all stimulus conditions. A. Responses using ISCEV standard conditions. B. Standard ERG responses of a patient with CSNB. The distinction between CSNB and retinitis pigmentosa is very important in the clinical retina.