Contrast letter acuity as a measure of visual dysfunction in patients with Friedreich ataxia.
BACKGROUND
Friedreich ataxia is a progressive neurodegenerative disorder affecting afferent cerebellar pathways and other neuronal systems, including afferent visual pathways. A systematic clinical outcome measure for examination of visual dysfunction in Friedreich ataxia has not been identified. We sought to identify a simple, reliable method for assessing clinical and subclinical visual dysfunction in patients with Friedreich ataxia.


METHODS
Contrast letter acuity was measured binocularly in Friedreich ataxia patients and age-matched visually asymptomatic volunteers (control group) using the Low-contrast Sloan Letter Charts at three different low-contrast levels (5.0%, 1.25%, and 0.6%). Binocular high-contrast visual acuity (100% level) was also determined for each participant.


RESULTS
Despite equal median binocular high-contrast visual acuities between the two groups, patients with Friedreich ataxia had significantly lower (worse) Low-contrast Sloan Letter Chart scores compared with controls, particularly at the lowest contrast levels (1.25% and 0.6%). Ambulation status significantly predicted Low-contrast Sloan Letter Charts scores in linear regression models accounting for patient age, suggesting a potential complementary role for Low-contrast Sloan Letter Chart testing in the assessment of disease status as well as visual function in Friedreich ataxia.


CONCLUSIONS
This study demonstrates that Low-contrast Sloan Letter Chart testing may provide a useful clinical outcome measure for Friedreich ataxia and other neuro-ophthalmologic disorders.
Lynch
David R
DR
Department of Neurology, University of Pennsylvania and The Children's Hospital of Philadelphia, 19104, USA. lynch@pharm.med.upenn.edu
Farmer
Jennifer M
JM
Rochestie
Dustin
D
Balcer
Laura J
LJ
D000293:Adolescent; D000328:Adult; D002648:Child; D015350:Contrast Sensitivity; D005621:Friedreich Ataxia / Q000150:complications*; D006801:Humans; D008875:Middle Aged; D014786:Vision Disorders / Q000175:diagnosis* / Q000209:etiology*; D014787:Vision Tests; D015348:Vision, Binocular; D014792:Visual Acuity