Purpose: The purpose of this study was to develop a convenient means to measure rod (and cone) function by automated perimetry in patients with inherited retinal degenerations (IRDs).
Methods: A currently available automated perimeter was used to determine sensitivity (in decibels) to a blue target in the dark-adapted (DA) state and a white target in the light-adapted (LA) state. Normal subjects and IRD patients were evaluated with a full-threshold 71-locus strategy (the retinitis pigmentosa [RP] test) and a size III target. Comparisons were made with results from the more commonly used methods of two-color DA perimetry and middle/long-wavelength LA perimetry in the same patients.
Results: Rod function using the blue target and the RP test was determined for normal subjects by measuring DA sensitivities. If patients detected the blue stimulus in the DA state, it was determined whether the value was rod mediated by using normal data acquired during the cone plateau phase of dark adaptation. If rod mediated, rod sensitivity loss (RSL) was calculated and mapped across the visual field. Light-adapted sensitivities in normal subjects were also measured, permitting cone sensitivity losses (CSL) to be calculated for the patients. Multiple methods were used to compare RSL and CSL results with those from two-color DA perimetry and chromatic LA perimetry, and there was close correspondence between the methods.
Conclusions: The unmodified automated static perimeter used in the DA and LA states presents a practical approach to accomplish current goals of treatment trials in IRDs. This proof-of-principle study is an initial step toward establishing a clinical method to gather reproducible data on photoreceptor-mediated sensitivity.