Assessing contrast sensitivity function in CRB1-retinopathies: Exploring child-friendly measures of visual function.

PURPOSE: Mutations affecting the CRB1 gene can result in a range of retinal phenotypes, including early onset severe retinal dystrophy/Leber congenital amaurosis (EOSRD/LCA), retinitis pigmentosa, cone-rod dystrophy (CORD), and macular dystrophy (MD). As research into treatment strategies advances towards clinical translation, there is a need to establish reliable outcome metrics. This study explores the contrast sensitivity function (CSF) across different spatial frequencies in individuals with CRB1-retinopathies using the child-friendly PopCSF test, an iPad-based "gamified" assessment. METHODS: Prospective cross-sectional study of 20 patients with molecularly confirmed biallelic CRB1 pathogenic variants from Moorfields Eye Hospital, London, UK, was conducted. Best-corrected visual acuity (BCVA), contrast sensitivity using the Pelli-Robson chart, and the PopCSF test were performed. RESULTS: Of the 20 CRB1 patients, seven had EOSRD/LCA, three had CORD, and 10 had MD. There was no statistically significant difference between the mean BCVA between phenotypes (P = 0.066). However, a significant difference was found between groups in the mean letter log contrast sensitivity (logCS) and area under the contrast sensitivity function (AUCSF) with P = 0.047 and P < 0.001, respectively. A moderate positive correlation was observed between Pelli-Robson and PopCSF (r = 0.53, P = 0.020). The CRB1 cohort had significantly lower CSF at both low and high spatial frequencies compared to controls. Among the CRB1 phenotypes, patients with EOSRD/LCA, exhibited the lowest CSF. CONCLUSIONS: This study is the first to examine CSF across spatial frequencies in patients with CRB1-retinopathies using the novel PopCSF test. TRANSLATIONAL RELEVANCE: The CSF holds promise as a potential functional vision trial endpoint.