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Contrast sensitivity norms for the Mentor B-VAT II-SG video acuity tester.

The Mentor B-VAT II-SG video acuity tester is a high-resolution video system designed to present many of the targets used in standard vision examinations (Snellen optotypes, clock charts, etc.). The SG model also presents sinusoidal gratings at various spatial frequencies and contrasts, making it possible to measure contrast sensitivity functions (CSF's). Using this system, we measured CSF's in a group of 69 young observers with well corrected vision. Contrast sensitivity scores were obtained at each of five spatial frequencies. A total of 5710 trials was presented. The mean contrast sensitivity scores of our group agree well with norms of other available CSF measurement systems, provided that the low spatial frequency truncation effects of each system are taken into account. A random subset of the group was retested 1 month later; no significant differences were found, demonstrating the reliability of the measurements. The data of this study should aid the clinician in identifying visual disorders. The data may be used to determine quantitative deviations from the norms or as a rapid screening test.