Benefits of color vision testing in diabetes

Color vision tests may help prevent diabetic patients from worsening

By A. Paul Chous, MA, OD, FAAO, CDE

ODs must consider a more sophisticated color vision analysis for patients with diabetes. Color vision deficits in diabetes (and prediabetes) are common and may precede vascular retinopathy,1-3worsen with progressing retinopathy—especially macular edema,4,5and affect vision-related quality of life.6

Tracking threshold color vision changes over time appears to be a reasonable surrogate marker for worsening retinopathy and metabolic control. Analogous to threshold visual field stability or deterioration in patients with glaucoma, allowing for adjustment of our recommendations and therapeutic targets based on trend analysis (e.g., improved blood glucose control; color and contrast enhancing ophthalmic lenses; modification of the patient’s chromatic visual environment; and nutritional supplementation).7

Diabetes and color vision

Diabetes is known to affect blue-yellow color vision per a number of reports.8-10 Tritan deficits are worse in those with diabetes and no retinopathy compared to age-matched controls. The severity of such defects is associated with increasing severity of diabetic retinopathy (see Figure 1).4

Abnormal Farnsworth-Munsell 100 hue test results, primarily blue-yellow deficits, have been associated with both diabetes and prediabetes (impaired fasting glucose and/or impaired glucose tolerance). Higher total error scores increase the odds of prediabetes or diabetes six to 13-fold independently of other risk factors. The risk of non-proliferative retinopathy increases more than 20-fold.11

Diabetes duration and mean glucose (as reflected by HbA1c) were shown to be associated with predominantly tritan defects in 849 subjects with type 2 diabetes and no ophthalmoscopic signs of retinopathy. Some 22 percent of patients demonstrated abnormalities using the far less sensitive Farnsworth D-15 color vision test.12

Testing for color deficiencies

Automated color contrast threshold (CCT) testing is a more sensitive measure of color perception. It combines hue discrimination with reduced contrast optotype targets (letters or Landolt Cs) to isolate function of long (L), medium (M), and short (S) wavelength responsive cone cells and their attendant neural connections.

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Source: Optometry Times