Two-Color Dark-Adapted Perimetry Implemented with a Commercially Available Perimeter to Characterize Rod-Pathway Sensitivity

BACKGROUND AND OBJECTIVE: To characterize rod-pathway function across the visual field using 2-color dark-adapted perimetry (2cDAP) implemented with conventional Octopus 900 Pro perimeters. PATIENTS AND METHODS: Eighteen visually normal individuals and two retinitis pigmentosa (RP) patients participated. Thresholds were measured under dark-adapted conditions at 15 locations along the horizontal meridian using short (450 nm) and long (610 nm) wavelength stimuli. Threshold differences between the two wavelengths were used to determine rod- vs cone-mediated function. RESULTS: Among controls, peripheral and perifoveal thresholds for the short-wavelength stimulus were approximately 2 log units lower than for the long-wavelength stimulus. Foveal thresholds for the two wavelengths were similar. RP threshold profiles differed considerably from the controls, with normal foveal thresholds and high peripheral thresholds for both wavelengths. CONCLUSIONS: 2cDAP can be performed with an unmodified Octopus perimeter to evaluate rod function across the visual field and obtain information that is not available with standard automated perimetry.