Evaluation of Contrast Sensitivity, Color Vision, Visual Acuity in Patients with, without Diabetes

To investigate the discriminative ability of contrast sensitivity (CS), color vision and best corrected visual acuity (BCVA) in detecting functional losses in diabetic participants with and without retinopathy In this cross sectional study we examined 105 patients in Khatam-Al-Anbia Eye Hospital of Mashhad University of Medical Sciences including 70 diabetic patients (35 with retinopathy and 35 without retinopathy in fundus photography) with 35 control non-diabetic subjects matched for age and sex. The diabetic participants were subgrouped according to the level of retinopathy (EDTRS classification). CS was examined by means of CSV-1000 E instrument at 3, 6, 12 and 18 cpd, respectively in each eye. Color discrimination ability was measured with the Farnsworth D-15 test and BCVA by Snellen chart. When comparing visual performance of the right and left eyes of patients in each group, only the mean CS values at 6 cpd differ significantly in diabetics without retinopathy (P=0.01). CS was significantly lower in the diabetic eyes with retinopathy than in the normal eyes in all spatial frequencies. Comparing to control group, there was a statistically significant CS loss in spatial frequencies of 3, 6, 18 cpd in the diabetic eyes without retinopathy (P<0.05). The mean logMAR BCVA and color vision abnormalities were significantly higher in the diabetic eyes with retinopathy than in the normal eyes or the diabetic eyes without retinopathy (P<0.001). There was no significant difference between the visual performance of those diabetics without retinopathy compared to the control group. The sensitivity and specificity were almost identical for all tests of visual function in the right and left eyes. The sensitivity and specificity of the CS test in 6 cpd were 71% and 82% which were significantly higher than other spatial frequencies. So the discriminative ability of this spatial frequency in detecting diabetics with retinopathy was 71% and in detecting those without was 82%. The sensitivity and the specificity of the color vision test and BCVAs (logMAR≥0.05, Snellen≤9/10) were 79% and 94% respectively. There was significant difference between the visual performance of those diabetics with retinopathy compared to those without. There was excellent agreement between the results of these three tests. The findings also suggest that the appropriate combination of existing tests may be a useful method of improving screening accuracy in diabetic patients.