In many forms of congenital stationary night blindness, the patient presents with poor night vision and is myopic. I n the X-linked form, visual acuity is usually between 20/40 and 20/200. However, some patients with both the autosomal recessive and X-linked forms do not exhibit myopia, and have normal visual acuity. Further, some patients do not complain of night blindness. In this case, a definitive diagnosis can only be made on the basis of the ERG.
In Oguchi's disease, vision and peripheral fields are normal in daylight; however there is a manifest decrease in visual sensitivity in dim illumination. After typical dark adaptation, rod ERGs are reduced in amplitude. With prolonged dark adaptation (several hours), however, ERG amplitudes can return to near-normal levels.
Fundus albipunctatus is an autosomal recessive disorder characterized by early onset of nonprogressive poor night vision and yellowish-white spots scattered throughout the peripheral fundus. ERG and EOG values may reach normal values, but only after a prolonged (several hours) period of dark adaptation.