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Russell J. Adams, Avery Earle, Mary L. Courage; Fusing sine waves with optotypes: A new test of human spatial contrast sensitivity. Journal of Vision 2009;9(8):1023. doi: 10.1167/9.8.1023.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Current tests of spatial contrast sensitivity (CS) fall into two categories, those that employ luminance-modulated sine-wave gratings (e.g., the FACT chart), or those that use recognizable Snellen-like optotypes (e.g., the Pelli Robson chart). Both forms possess distinct advantages but an ideal test would combine the desired characteristics of each format. Here, we report on a novel prototype for one such test.
Methods: Five wall charts were constructed using custom software and a high quality PostScript printer. The optotypes on each row of a chart were Landolt Cs which, from the outside edge to the inside edge of each C, modulated sinusoidally in luminance. The average luminance within each C matched the chart's background. Each chart contained sine-wave Cs representing 1 of 5 spatial frequencies (0.75, 1.5, 3.0, 6.0 and 12.0 c/deg), with contrast on each successive row decreasing from 40% to 1% in equal log steps. 25 adults were tested monocularly at 3m, and for comparison and validation, were also tested with standard commercial CS tests: the FACT, Rabin, Pelli-Robson, and low contrast Sloan tests. To examine applicability with children, 25 4-and 5-year-olds were also tested.
Results: Adults easily completed the test in an average of only 2.3 min. Results showed that each subject generated an interpretable contrast sensitivity function (CSF), with individual performance on the sine-wave Cs predicting very well, the results on the standard CS tests. Children required more time (5.7 min) but most (94%) were capable of successful completion.
Conclusions: The new sine-wave C test of contrast sensitivity appears very successful. Both adults and children show definitive responses and clear estimates of threshold. Thus, the test holds promise as a hybrid tool for assessing simultaneously, both optotype CS and full spectrum contrast sensitivity, a feature that should have both experimental and clinical value.
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