Related Experiment Video
Updated: Feb 7, 2026
Author Spotlight: Assessment of Visual Acuity in Central Vision Loss Through Motion-Based Peripheral Vision Testing
Published on: February 23, 2024
Longitudinal analysis of contrast acuity in Friedreich ataxia
Ali G Hamedani1, Lauren A Hauser1, Susan Perlman1
1Department of Neurology (A.G.H., D.R.L.), University of Pennsylvania; Divisions of Neurology and Pediatrics (L.A.H., D.R.L.), Children's Hospital of Philadelphia, PA; Department of Neurology (S.P.), University of California at Los Angeles; Departments of Neurology and Pediatrics (K.M.), University of Iowa; Department of Neurology (G.R.W.), Emory University, Atlanta, GA; Department of Neurology (T.Z.), University of South Florida, Tampa Bay; Department of Neurology (S.H.S.), University of Florida, Gainesville; Department of Neurology (T.A.), Houston Methodist Hospital, TX; Murdoch Children's Research Institute (M.B.D.), Melbourne, Victoria, Australia; and Department of Neurology (A.B.), University of Rochester, NY.
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.
Related Concept Videos
02:20Longitudinal Research
01:26Longitudinal Studies
01:26Phase Contrast and Differential Interference Contrast Microscopy
In-phase-contrast microscopes, interference between light directly passing through a cell and light refracted by cellular components is used to create high-contrast, high-resolution images without staining. It is the oldest and simplest type of microscope that creates an image by altering the wavelengths of light rays passing through the specimen. Altered wavelength paths are created using an annular stop in the condenser. The annular stop produces a hollow cone of...
03:46Qualitative Analysis
For instance, group IV...
03:40Dimensional Analysis
Conversion Factors and Dimensional Analysis
The unit...
01:35Pedigree Analysis