Baseline characteristics of patients with RLBP1 retinitis pigmentosa enrolled in a prospective Natural History Study

Abstract

Purpose : Purpose: Retinitis pigmentosa (RP) due to biallelic mutations in the RLBP1 gene (RLBP1 RP) is an autosomal recessive form of RP, characterized by prolonged dark adaptation and progressive loss of peripheral and then central vision. No prospective natural history study has been conducted on these patients. 159 to 165 patients with identified mutation(s) in RLBP1 have been reported in the peer-reviewed literature. The purpose of this study is to evaluate variability and progression of functional and structural endpoints in RLBP1 RP patients. Here, we report the study design and preliminary baseline data (results of 2-year follow-up are presented in additional abstracts).

Methods : Methods: This is a non-interventional, two-center, prospective study evaluating RLBP1 RP patients every 6 months. The study assessments were: 1) basic eye exam (slit-lamp exam, dilated fundus exam, tonometry), 2) functional assessments including best corrected visual acuity (BCVA) in logMAR (ETDRS letter scores down to no light perception converted to logMAR); contrast sensitivity (CS); color vision (CV); full-field flicker electroretinograms (ERGs); full-field stimulus threshold (FST) dark-adaptation kinetics up to 6 hours for 2 wavelengths (450 and 632 nm); Humphrey visual fields (HVF); and 3) structural assessments by optical coherence tomography and fundus photography. All assessments were performed in both eyes, except the FST.

Results : Results: Forty-five patients (15 men and 30 women) aged 18-70 with RLBP1 mutations were enrolled between Sept 2013 and Jan 2015 (30 patients in Umeå, Sweden and 15 in St John’s, Canada). Key baseline measurements and the correlation between right (OD) and left (OS) eyes are shown in the table below. The recovery of FST to prebleach retinal sensitivity was severely prolonged (between 3-6 hours for both wavelengths). No noticeable differences were observed in any assessments between the two clinical sites. Pearson’s correlations between age and BCVA, central retinal thickness (CRT), HVF mean deviation were 0.60 (p <0.0001), - 0.15 (p = 0.35) and -0.50 (p = 0.0005), respectively (for FST-tested eye).

Conclusions : Conclusions: All endpoints collected for both eyes showed high correlations between eyes confirming bilateral symmetry of the disease. All patients showed severe dark adaptation prolongation. BCVA and HVF mean deviation were correlated with age.

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