Full-field stimulus threshold dark-adaptation kinetics over two-year follow-up in patients with RLBP1 retinitis pigmentosa enrolled in a prospective Natural History Study

Abstract

Purpose : Retinitis pigmentosa (RP) due to biallelic mutations in the RLBP1 gene (RLBP1 RP) is an autosomal recessive form of RP, with a hallmark of severely prolonged dark adaptation. 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 the variability and progression of dark-adaptation measured by a full-field stimulus threshold (FST) test (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. FST dark-adaptation kinetics were measured (Espion Ganzfeld Profile, Diagnosys LLC) in one eye at 450 and 632 nm wavelengths for up to 6 hours after overnight dark adaptation. Post-dilation, three repeated threshold measurements were obtained pre-bleach, immediately after bleach (0 minutes), at 15 and 30 minutes, and 1, 2, 3, and 6 hours post-bleach. The median of the three repeated threshold measurements was used for the kinetic curve. Annual progression (slope) was estimated using a random effect linear growth model and test-retest variability was assessed using the intra-class correlation coefficient (ICC).

Results : Preliminary FST kinetics (mean values), as well as annual progression (slope) and test-retest variability (ICC) are reported in Table 1. RLBP1 RP patients showed severe delays in dark adaptation at both wavelengths with recovery to pre-bleach levels after three to six hours. Additionally, patients had abnormal FST thresholds which correlated (Pearson’s correlations) with age and BCVA at baseline as shown in Table 2.

Conclusions : RLBP1 RP patients showed severely delayed dark adaptation. There was no significant disease progression in FST thresholds over 2 years. There were good correlations of FST thresholds with age and BCVA.

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