Location and Identity of Photoreceptors Contributing to the Full-Field Stimulus Test (FST).

Quantification of visual function in severe forms of inherited retinal disease is challenging because of lack of stable gaze. Full-field stimulus test (FST) was developed two decades ago as an outcome measure to evaluate potential changes to the vision after gene augmentation therapy in RPE65-associated Leber congenital amaurosis. With greater use, there has been greater interest in better understanding photoreceptors dominating the perception of FST. Review of the literature and currently available data support the longstanding and currently prevailing hypothesis that sensitivity of the healthiest retinal region beneficial to visual function drives the sensitivity of FST. In contrast, the alternative hypothesis-that far peripheral photoreceptors hidden from the visual field signal perception of intraocularly scattered light originating from FST-is not supported.