Peripheral and central colour contrast sensitivity in diabetes

To study the influence of diabetes, with or without early retinopathy, on peripheral and central colour contrast sensitivity.

The study included 32 patients with diabetes mellitus type II and 47 age-matched normals. The patients were divided into three sub-groups. 1. Diabetics with no retinopathy (on photographs or biomicroscopy). 2. Diabetics with microaneurysms only. 3. Diabetics with microaneurysms and hard exudates. Colour contrast sensitivity was measured with a computer graphics system along the protan, deutan and tritan axes.

The peripheral colour contrast thresholds were significantly elevated for all axes when comparing the group with microaneurysms and exudates to normals. There were also significant differences between the group with microaneurysms and hard exudates and the two other diabetic groups, respectively, but only for the tritan axis. Diabetics with no retinopathy or with microaneurysms only did not differ significantly from normals. The central colour contrast thresholds showed significant differences between normals and the group with microaneurysms, but only for the protan and deutan axes. There were significant differences for all three axes between normals and the group with microaneurysms and hard exudates. There were also significant differences between the group with microaneurysms and hard exudates and the two other diabetic groups, but only for the tritan axis. Diabetics with no retinopathy did not differ significantly from normals.

Peripheral colour contrast sensitivity was affected by low-grade diabetes type II retinopathy. This finding has to be considered if the method is to be used in screening for glaucoma. The central colour contrast sensitivity test seems to correlate to the degree of retinopathy and thereby perhaps provides a new screening method for diabetes retinopathy. Further studies are required in order to evaluate such a possibility.