Longitudinal analysis of contrast acuity in Friedreich ataxia

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

Research output: Contribution to journalArticle

3 Scopus citations

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.

Original languageEnglish (US)
Article numbere250
JournalNeurology: Genetics
Volume4
Issue number4
DOIs
StatePublished - Aug 1 2018

ASJC Scopus subject areas

  • Clinical Neurology
  • Genetics(clinical)

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