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Sloan Low Contrast Letter Acuity
Availability
Charts are available for purchase from: Click here for Sloan Low Contrast Letter Acuity
Classification
Core for FA
Supplemental for MS
Short Description of Instrument
Construct measured: Low contrast letter acuity
Generic vs. disease specific: Generic
Means of administration: Assessment
Intended respondent: Patient
# of items: N/A
# of subscales and names of sub-scales: N/A
# of items per sub-scale: N/A
Comments/Special Instructions
Scoring: Charts are scored based on the number of letters identified correctly. This format provides continuous scoring and may allow Sloan charts to capture losses of contrast at small letter sizes.
 
Background: Low contrast acuity testing provides information on patient- reported aspects of vision. This testing is performed using low-contrast Sloan letter charts. Each chart corresponds to a different contrast level (shade of gray letters on white/retroilluminated background).
Rationale/Justification
Strengths/Weaknesses: Sloan charts have a standardized format based on Early Treatment Diabetic Retinopathy Study visual acuity charts, which are the standard used for ophthalmology clinical trials.
 
Psychometric Properties: Inter-rater agreement was described with the intraclass correlation coefficient (ICC) and comparison of mean scores. Excellent inter-rater agreement (ICC=0.86-0.95) was demonstrated at each contrast level among MS patients (n=100) and visually-asymptomatic volunteers (n=33). Average letter scores at the lowest contrast level (0.6%) were highly variable in the MS group, even among patients with visual acuities of 20/20 or better, and among those who required no assistance for ambulation.
 
Administration: Patients are instructed to stand 1 m away from the Sloan letter charts and read the letters, starting with the highest contrast.
References
Balcer LJ, et al. Contrast letter acuity as a visual component for the Multiple Sclerosis Functional Composite. Neurol. 2003; 61:1367-73.
 
Other References:
 
Balcer LJ, et al. New low-contrast vision charts: reliability and test characteristics in patients with multiple sclerosis. Mult Scler June 2000; 6(3):163-171.
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