Issue 159 Item 12 Color Vision Test Detects Diabetic Retinopathy Before Vision i

Automated tritan contrast threshold (TCT) assessment identifies sight-threatening diabetic retinopathy before vision is lost. Color vision often deteriorates before visual acuity is lost and morphological changes are detectable, Dr. Anthony G. Casswell, of Sussex Eye Hospital in Brighton, and colleagues explain. However, conventional color discrimination tests are not sensitive enough for widespread screening purposes.

The authors performed automated TCT testing on 510 patients with best corrected visual acuity exceeding 20/30, and findings were compared to those obtained by slit lamp biomicroscopy. TCT was measured using a computerized, cathode ray tube-based system with a custom-made plug-in card stimulus generator. The TCT was 42.5 for patients with no retinopathy and 41.7 for those with background retinopathy.

Seventeen eyes exhibited STDR, and TCT correlated significantly with the presence of STDR (p < 0.001), with a sensitivity of 94% and a specificity of 95%. The sensitivity for detecting proliferative retinopathy and maculopathy was 100%. Among the 3 patients with pre-proliferative retinopathy, mean TCT was 29.6. For the 2 with proliferative retinopathy, the mean TCT was 21.7, and for the 12 with maculopathy, the TCT was 24.0.

TCT deficits showed no association with duration of diabetes or the latest glycosylated hemoglobin results.

Because it directly measures visual function, Dr. Casswell’s team believes that TCT testing will “also identify early those subjects who will progress to develop more severe retinal disease.” Br J Ophthalmol 2003;87:747-752.