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Pinakin Gunvant Davey, Raymond Maeda, Aaron Seitz; Assessment of Evans low contrast sensitivity in measuring log contrast sensitivity.. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3903.
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© ARVO (1962-2015); The Authors (2016-present)
Clinically a quick and reliable estimate of contrast sensitivity levels is desirable to evaluate patients with decreased vision or difficulty of vision in dim illumination. The Evans Low Contrast Test (ELCT) chart presents Sloan Letters optotypes line size of 20/630 (a testing distance of 1m) varying contrast in sets of 3 letters of equal contrast level. All triplets are balanced for letter difficulty and differ in contrast by 0.15 log contrast step. The purpose of this study was to evaluate the short term repeatability of the ELCT in measuring lowest log contrast appreciated in healthy and eyes with ocular pathology.
Study participants were tested at 13 feet in a dark environment and the retro illuminated box provided the background illumination for the ELCT chart. Twenty five study participants with either normal visual function or decreased visual function performed assessment with ELCT twice viewing the chart binocularly. Repeatability was assessed using Altman and Bland plots and 95% limits of agreement were calculated. Difference in measurements was assessed using paired samples t-test.
The mean log contrast of attempt 1 and attempt 2 was 2.198 and 2.208 (standard deviation 0.17 and 0.08 respectively). The mean difference between the groups was not statistically significant (paired samples t-test: t statistic =0.36; p value =0.72). The test was easy to perform and the results were obtained in a couple of minutes maximum.
The Evans Low Contrast Test provides a quick and easy method of estimating lowest log contrast and may be useful test in identifying decreased contrast sensitivity in individuals with ocular pathology.
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