Abstract
Purpose :
Usher Syndrome type 1 is a rare disease (prevalence: 1/50,000 in Europe) characterized by retinitis pigmentosa (RP), a congenital profound deafness and vestibular dysfunction. This study evaluates the natural history and retinal phenotypic differences in patients with Usher syndrome type 1B (USH1B) due to MYO7A mutations.
Methods :
Retrospective, chart-review study. The USH1B population included 45 patients from 38 families (age range, 9-61 years; median, 27) followed at the CHNO des Quinze-Vingts, Paris. Recorded visual assessments included visual acuity (VA), visual field (VF) and optical coherence tomography (OCT). Structure-function correlations were performed in comparison with age and phenotypic variability was studied.
Results :
The median best eye visual acuity (BCVA) for the cohort was 0.5 in decimal (range, 0.05–1.25), and correlated to the age (Spearman's rank correlation coefficient, r = -0.57; p < 0.0001), with central retina thickness (CRT) and length of the ellipsoid zone (lEZ) on OCT (r = 0.51; p = 0.0025; r = 0.53; p = 0.0016, respectively). Correlation between BCVA and CRT is higher when analyzing data from patients without edema (r = 0.72; p = 0.0005).VA decreases with advancing age but it is preserved until approximately 50 years.
VF loss follows a pattern similar to non-syndromic RP, initially showing scotomas deepening in mid-periphery in the first decade, and progressively coalescing and extending. The residual tubular VF is also progressively reduced over time. The median of the diameter of the residual central VF was 35° (range, 3°–170°), and was also correlated with age (r = -0.46; p=0.0014).
OCT shows epiretinal membranes in 8% of cases, and cystoid macular edema (CME) in 39% especially in younger patients. The CME rate was 67% in patients under 20 years old, 29% between 21 and 40 years old and 17% over 40. In the patients without CME, the median CRT was 154.8 (range, 100–279μm), and is correlated to lEZ (r = 0.75; p = 0.0002).
Conclusions :
This study provides a better understanding of the natural progression of the ocular disease in patients with USH1B. The additional knowledge on this rare genetic form of RP will facilitate the appropriate selection of USH1B patients for whom treatment with gene therapy would be expected to provide the optimal benefit-risk balance in ongoing clinical trials.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.