Rod saturation perimetry. Testing of the cone function with achromatic objects.

Restriction of the visual fields in bright illumination and return of the peripheral field in lower illumination were the main complaints of a 59-year-old woman with slowly progressive cone dysfunction and normal rod function. She had normal central visual acuity, normal central color vision, and normal visual fields when tested with the standard Goldmann perimeter. A large ring scotoma was demonstrated in both of her eyes, using tangential perimetry employing a white background of 85% reflection and test objects darker than the background. Using a background of 250 candelas/sq m, which caused a complete saturation of the rod function, the scotoma was absolute. Black test objects of 5% reflection were not seen.