Blue-on-yellow perimetry in the complete type of congenital stationary night blindness

Purpose. To resolve the discrepancy between nonrecordable full-field short wavelength cone electroretinograms (S-cone ERGs) and the presence of normal color vision in patients with the complete type of congenital stationary night blindness (CSNB1). Methods. Conventional white-on-white (W- W) perimetry, blue-on-yellow (B-Y) perimetry, and the Farnsworth-Munsell 100- hue test were performed in five patients with CSNB1. Diagnosis of CSNB1 was made by clinical and electrophysiological examinations. Twelve normal, age- matched control subjects and an additional 7 normal, highly myopic subjects were tested. Results. Color vision was normal in all the CSNB1 patients by the Farnsworth-Munsell 100-hue test. B-Y perimetry demonstrated that blue cone sensitivity in CSNB1 was normal in the fixation area, but the mean sensitivities of the entire 60°field, the central 0°-to-15°, and 15°-to- 30°ring were significantly decreased compared with the normal and myopic subjects. The sensitivity difference between 15°-to-30°and 0°-to-15°in B-Y perimetry increased significantly in CSNB1 compared with both normal and myopic control subjects. Conclusions. Our perimetric results demonstrated that the S-cone function in CSNB1 is preserved only in the fovea and becomes abnormal toward the peripheral retina. This accounts for the normal color vision that tests mainly foveal function and the nonrecordable S-cone ERGs that arise mainly from peripheral retina.