Contrast Acuity With Different Colors in Parkinson's Disease

Abnormal color vision and contrast acuity may have significant impact on daily activities.

Evaluate color visual acuity, at high and low contrast, in Parkinson's disease (PD) and controls using an iPad application.

Color visual acuity was tested with the Variable Contrast Acuity Chart (King-Devick Test LLC, Oakbrook Terrace, IL) on an iPad 2 at 40 cms using five colors (red, green, blue, yellow, and black) at low (2.5%) and high (100%) contrast. A numerical score (0-95) was assigned based on the number of correctly identified letters.

Thirty-six PD (mean ± standard deviation age 68 ± 10 years) and 36 controls (72 ± 11.2 years) were studied. PD disease duration was 6.4 ± 4.6 years; MDS-UPDRS part II was 11.7 ± 7.0, and part III was 24.5 ± 9.9. After adjusting for age and sex, PD patients had significantly (P < 0.05) lower scores at high (100%) as well as low (2.5%) contrast for all five colors tested (red, green, blue, yellow, and black), except yellow low contrast (2.5%; P = 0.10). The largest effect size (0.88) was with yellow high contrast, and the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy using a cut-off score of 82 was 31%, 97%, 92%, 58%, and 64%, respectively. No correlation to disease duration was found.

This iPad application may be a simple-to-use biomarker for assessing color vision in PD. Further research is needed to determine disease specificity and whether there is a role in monitoring disease progression, treatment response, and identifying prodromal PD.