Assessment of Macular Function Using the SKILL Card in Adults With Type 2 Diabetes Mellitus

PURPOSE. To evaluate the impact of reduced contrast and reduced luminance on visual acuity (VA) using the Smith-Kettlewell Institute Low Luminance (SKILL) Card in patients with type 2 diabetes mellitus (T2DM). METHODS. We studied adults aged 27 to 65 years, 32 with T2DM and no retinopathy (NoRet group), 22 with T2DM and nonproliferative diabetic retinopathy (NPDR group), and 38 healthy control subjects. Monocular high-contrast (SKILL light) and low-contrast, low-luminance (SKILL dark) near visual acuities were tested. The SKILL score was calculated as the difference between dark chart and light chart acuities and was corrected for age. Contrast sensitivity (CS) was also measured. Subject group differences were examined using ANOVA and Tukey honestly significant difference test. Receiver operating characteristic curve analysis was used to assess the ability of the SKILL Card and CS to discriminate the subject groups. RESULTS. The SKILL score and CS were significantly worse in both diabetes groups compared with the controls (P < 0.01). SKILL scores in the NPDR group were poorest (highest) and significantly worse than those in the NoRet group (P < 0.05). SKILL scores discriminated NPDR and NoRet patients from the controls with high accuracy (99% and 88%, respectively), which was significantly (P < 0.03) better than CS (78% and 74%, respectively). CONCLUSIONS. The SKILL Card demonstrated vision function changes in diabetes even in the absence of clinically evident retinopathy. Diabetic retinopathy led to a further increase in the SKILL score, while high-contrast VA remained unchanged.