Central visual function over two-year follow-up of patients with RLBP1 retinitis pigmentosa enrolled in a prospective Natural History Study

Abstract

Purpose : Central visual function is typically affected in moderate to advanced stages of retinitis pigmentosa. A subset of patients with retinitis pigmentosa due to mutations in both alleles of the RLBP1 gene (RLBP1 RP) shows early foveal involvement. A prospective Natural History Study was initiated to evaluate functional and structural endpoints in RLBP1 RP patients. Here, we report preliminary 2-year results on test-retest variability and progression of central visual function measurements, namely best-corrected visual acuity, contrast sensitivity and color vision (results from other endpoints are presented in additional abstracts).

Methods : This non-interventional, two-center (Sweden and Canada), prospective study included evaluations of 45 RLBP1 RP patients every 6 months. Central visual function was evaluated as best-corrected visual acuity (BCVA) in logMAR (ETDRS letter scores and low vision down to no light perception were converted to logMAR); contrast sensitivity (CS) in logCS using Pelli-Robson charts; and color vision (CV) as Bowman's Total Color Difference Score (TCDS) assessed with Farnsworth D15 under illuminant C equivalent conditions. Annual progression was estimated as the slope of a random effect linear growth model and test-retest variability was assessed using the intra-class correlation coefficient (ICC). Between-eye correlations were made for each measurement at each visit.

Results : BCVA, CS and CV preliminary results (mean values) as well as annual progression slope and test-retest variability (ICC) for right (OD) and left (OS) eyes are displayed in the table. Statistically significant Pearson’s correlations between the two eyes at baseline and at each follow-up visit were observed for BCVA ranging from 0.92 to 0.96 (p <0.001), CS ranging from 0.91 to 0.94 (p <0.001), and CV ranging from 0.79 to 0.92 (p <0.001). No noticeable differences in mean and standard deviation for any assessments were observed between the two clinical sites.

Conclusions : For BCVA, CS and CV, there was no statistically significant progression over the 2-year follow-up. Patients with RLBP1 RP showed similar severity of the disease in both eyes on all measurements of central vision.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.