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Andrew A. Chen; The Effect of Decreased Near Visual Acuity on Ishihara's Test for Color Blindness. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3869.
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To determine the effect of decreased near visual acuity on Ishihara’s test for color blindness.
Twenty subjects (8 men and 12 women) were enrolled in the study. All subjects were noted to have logMAR 0.00 (20/20) near visual acuity and normal color vision. Each subject’s right eye was fogged with plus spheres at the phoropter to logMAR near visual acuity of 1.60 (20/800). The 15 plates of the Ishihara color vision test (Kanehara & Co., Ltd) were then presented at 28 inches from the phoropter under bright artificial light conditions and the number of correctly identified plates was recorded. The procedure was then repeated for logMAR near visual acuities of 1.30, 1.20, 1.10, 1.00, 0.90, 0.80, 0.70, and 0.00 (Snellen 20/400 to 20/20).
The average age of subjects was 37.7 years SD 13.9. Subjects with near visual acuity equal to or better than logMAR 1.00 (20/200) correctly identified all color plates. Subjects with near visual acuities of logMAR 1.10 and 1.20 (20/250 and 20/320) missed an average of 1 and 2 previously identified color plates respectively. Subjects with near visual acuity of logMAR 1.30 (20/400) missed an average of 7 previously identified color plates. Subjects with near visual acuity of logMAR 1.60 (20/800) missed an average of 13 previously identified color plates. The corrected Spearman rank order correlation coefficient was -0.97.
Ishihara’s test for color blindness is accurate for individuals with 20/200 near visual acuity or better. Those with near visual acuities between 20/250 and 20/320 should be expected to miss 1 to 2 plates due to decreased vision alone. Finally, using Dr. Ishihara’s criterion for color deficiency (fewer than 10 plates identified correctly), individuals with near visual acuity of 20/400 or worse may be incorrectly diagnosed as color defective if decreased near visual acuity is not taken into account.
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