Full-Field Stimulus Threshold: A Key Functional Outcome Measure in Retinal Diseases and Clinical Trials

Full-field stimulus threshold (FST) testing is a psychophysical method used to assess global retinal function, particularly in patients with severe visual impairment where conventional perimetry is unreliable. This review explores the development, clinical protocols, and applications of FST in retinal diseases, with a focus on its role in inherited retinal dystrophies (IRDs) such as Leber congenital amaurosis (LCA) and retinitis pigmentosa (RP). FST has emerged as a key functional outcome measure in clinical trials, particularly in evaluating novel gene therapies for IRDs. Its fixation-independent nature and ability to detect residual visual function make it valuable for assessing disease progression and treatment efficacy. However, challenges remain regarding standardization and test variability. Ongoing efforts seek to standardize and optimize FST protocols and establish it as a standardized metric in both clinical and research settings.