Measuring Rod- and Cone-Photoreceptor-Specific Vision in Inherited Retinal Diseases Using a Commercial Perimeter.

Purpose: The primary pathology in most inherited retinal diseases (IRDs) is located within photoreceptors. Standard automatic perimetry (SAP) can measure photoreceptor disease severity but cannot distinguish between rods, long/middle-wavelength (L/M)-sensitive, and short-wavelength (S)-sensitive cones. Herein we developed a protocol that can provide photoreceptor-specific sensitivities. Methods: A commercial (unmodified) perimeter was used to develop a clinical protocol that includes five profiles along the vertical meridian, utilizing different chromatic stimuli presented in the dark-adapted state or on adapting backgrounds. Data were recorded by the Perimetry for IRD (PERIRD) consortium in control participants and patients with IRDs. Results: The protocol was developed by evaluating the relationship between chromatic thresholds and adapting backgrounds using a threshold-versus-intensity paradigm. Five conditions were selected: two-color dark-adapted, red-on-blue, and blue-on-yellow tests in addition to white-on-white SAP. Prediction intervals from control eyes were defined, and physiological ranges over which rod-, L/M-, and S-cone-specific results can be obtained were estimated. Testing in complete achromatopsia, blue-cone monochromacy, and enhanced S-cone syndrome confirmed classic patterns expected from cone diseases. Patients with incomplete achromatopsia showed partially retained L/M- or S-cone function. Patients with retinitis pigmentosa demonstrated use of photoreceptor-specific function to interpret different disease subtypes and stages. Total test time for the protocol was usually under 30 minutes. Conclusions: Photoreceptor-specific function can be measured over a large dynamic range using a turnkey commercial perimeter and a relatively short, practical protocol that may be introduced into the clinic, translational work, and clinical trials.