Abstract
Purpose:
To evaluate vision function at reduced contrast and reduced luminance using the Smith-Kettlewell Institute Low Luminance (SKILL) card in adult patients with type 2 diabetes and with or without retinopathy.
Methods:
We studied 13 participants with no retinopathy (NoRet group), 13 participants with moderate to severe retinopathy (NPDR group) and 40 healthy control subjects (control group). Their mean ages were 54.0 ± 10.5, 54.4 ± 9.1, and 41.8 ± 12.2 yrs for the NoRet, NPDR and control groups, respectively. All the participants with diabetes had diabetes duration of at least 10 yrs and an HbA1c above 7%. All the participants had 20/20 or better-corrected visual acuity. Monocular high contrast and low contrast, low luminance (1 log unit less than the white chart) near visual acuity were tested using light and dark sides of the SKILL card at a distance of 40 cm. The SKILL score was calculated as the difference in performance on the low-contrast dark versus the high-contrast light side adjusted for the age difference between the controls and diabetic groups. T-tests were performed to examine whether the subject groups differed. Linear regressions were performed to examine effects of age, HbA1c, central macular thickness, and duration of diabetes on SKILL score.
Results:
The SKILL score was higher (reflecting reduced performance on the low contrast, low luminance chart) in both of the diabetic groups as compared to the controls but was significantly different only between controls and the NPDR group (P<0.05). There was no statistically significant correlation between HbA1c or duration of diabetes and SKILL score (P>0.5 for both). Age was positively correlated with SKILL score in controls and in NoRet group (both P<0.03) but not in the NPDR group (P>0.5).
Conclusions:
The SKILL card sensitively assesses vision function change in diabetes when acuity is still good. Diabetic retinopathy leads to an increased SKILL score i.e. reduced performance, while visual acuity is unaffected. The SKILL score can provide different information about mechanisms of diabetic retinal damage than regular visual acuity charts.
Keywords: 499 diabetic retinopathy •
754 visual acuity