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R. J. Adams, A. E. Earle, M. L. Courage; Luminance-Modulated Sinusoidal Optotypes: A New Test for Measuring Human Spatial Contrast Sensitivity. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2015.
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© ARVO (1962-2015); The Authors (2016-present)
Spatial contrast sensitivity is the most thorough measure of pattern vision, arguably, the most critical aspect of human visual functioning. Current tests of contrast sensitivity (CS) fall into two categories, those that employ sine wave gratings varying in both spatial frequency and contrast (e.g, the FACT chart,and those which use recognizable optotypes that decrease in contrast (e.g., the Pelli Robson chart). Both forms of CS testing possess distinct advantages: Sine-wave grating tests are grounded in Fourier’s theorem, test CS over a wide range of spatial frequencies and thus reveal a subject’s complete contrast sensitivity function (CSF). Optotype tests are more comparable to traditional clinical tests of visual acuity and are somewhat more time efficient. An ideal test could combine the desired characteristics of both. In the present work, we report on a novel prototype for one such test.
Five wall charts were constructed using custom software and a high quality PostScript printer. The optotypes on each chart were Landolt Cs which, from the outside edge to the inside edge of the C, modulated sinusoidally in luminance. The average luminance of the sine waves matched the chart’s background. Each chart contained Cs defined by sine waves representing 1 of 5 spatial frequencies (0.75, 1.5, 3, 6 and 12 cy/deg). With each successive row, the optotypes decreased in contrast from 40% to 1.0% in equal log steps. 25 adults (M = 32y) were tested monocularly at 3m with the sine-wave C charts, and for comparison and validation, were also tested with the commercially available FACT, Rabin, Pelli-Robson, and Sloan low contrast CS tests. To examine the applicability of the sine-wave Cs with children, we also tested 25 4- to-5- year- old preschoolers.
All adults easily completed the test very rapidly in an average time of 2.4 min. Results showed that each subject generated an interpretable CSF and that performance predicted that on the commercial CS tests very well. Children required more time (M = 5.4 min), but most (94%) were capable of completion.
The new sine-wave C test of contrast sensitivity appears to be successful. Both adults and children show definitive responses and clear estimates of threshold. Among adults, performance compares very well with existing CS tests. Thus, the sine-wave C test may be a promising "hybrid" tool for the comprehensive assessment of spatial contrast sensitivity as it appears to generate a subject’s full-spectrum CSF, yet still employ optotypes which increases its clinical interpretability and flexibility.
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