Detailed Evaluation of Chromatic Pupillometry and Full-Field Stimulus Testing to Assess Ultralow Vision in Retinitis Pigmentosa

PURPOSE: Novel therapeutic options, such as regenerative medicine and gene therapy, are now emerging as viable treatment options for patients with severe visual impairments, such as retinitis pigmentosa (RP). Gradable assessment of patients’ visual function is essential to consider treatment options and to evaluate treatment outcomes; however, evaluation of visual function in patients with advanced low vision is often challenging because of patients’ poor and sometimes unpredictable responses. In this study, we attempted to accurately assess visual capabilities and disease stage in patients with RP with a visual acuity (VA) of ≤ 0.01. DESIGN: Retrospective analysis of visual function indicators, including VA, retinal thickness, full-field stimulus testing (FST), and chromatic pupillometry. SUBJECTS: Overall, 43 patients (84 eyes) with advanced RP with a VA of ≤ 0.01 visited Kobe City Eye Hospital from 2019 to 2021. METHODS: Hierarchical (multilevel) Bayesian modeling was used to estimate individual eye’s pupil response and FST threshold, taking into account the ambiguity and randomness often observed in patients with ultralow vision. Using the estimated ability obtained from each test, the correlation between each test and retinal thickness was further analyzed to make a comprehensive assessment of the data. MAIN OUTCOME MEASURES: Visual acuity, retinal thickness, FST threshold, and pupil diameter change to different light stimuli. RESULTS: Full-field stimulus testing and pupillometry measurements were moderately correlated with VA but exhibited a wide range of values within the same VA groups. Full-field stimulus testing was not correlated with central retinal thickness at counting fingers/hand motion VA range and seemed to reflect overall remaining photoreceptor function, including peripheral retina. Pupillometry may be able to distinguish between different levels of inner retinal function. CONCLUSIONS: The combination of pupillometry and FST allowed for graded evaluation of visual function within patients grouped in the same VA groups in patients with advanced RP with ultralow vision. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.