Longitudinal analysis of contrast acuity in Friedreich ataxia.

Abstract

OBJECTIVE:

To determine the natural history of contrast acuity in Friedreich ataxia.

METHODS:

In the Friedreich Ataxia-Clinical Outcome Measures Study, participants (n = 764) underwent binocular high- and low-contrast visual acuity testing at annual study visits. Mixed-effects linear regression was used to model visual acuity as a function of time, with random intercepts and slopes to account for intraindividual correlation of repeated measurements. A time-varying covariate was used to adjust for diabetes, and interaction terms were used to assess for effect modification by GAA repeat length, disease duration, and other variables.

RESULTS:

Across a median of 4.4 years of follow-up, visual acuity decreased significantly at 100% contrast (-0.37 letters/y, 95% confidence interval [CI]: -0.52 to -0.21), 2.5% contrast (-0.81 letters/year, 95% CI: -0.99 to -0.65), and 1.25% contrast (-1.12 letters/y, 95% CI: -1.29 to -0.96 letters/year). There was a significant interaction between time and GAA repeat length such that the rate of decrease in visual acuity was greater for patients with higher GAA repeat lengths at 2.5% contrast (p = 0.018) and 1.25% contrast (p = 0.043) but not 100% contrast. There was no effect modification by age at onset after adjusting for GAA repeat length.

CONCLUSIONS:

Low-contrast visual acuity decreases linearly over time in Friedreich ataxia, and the rate of decrease is greater at higher GAA repeat lengths. Contrast sensitivity has the potential to serve as a biomarker and surrogate outcome in future studies of Friedreich ataxia.

• Authors: Ali G Hamedani, Lauren A Hauser, Susan Perlman, Katherine Mathews, George R Wilmot, Theresa Zesiewicz, S H Subramony, Tetsuo Ashizawa, Martin B Delatycki, Alicia Brocht, David R Lynch
• Journal: Neurology. Genetics (Neurol Genet) Vol. 4 Issue 4 Pg. e250 (Aug 2018) ISSN: 2376-7839 [Print] United States
• PMID: 30065952 (Publication Type: Journal Article)