Hue discrimination and S cone pathway sensitivity in early diabetic retinopathy.

Measures of hue discrimination and M (green) and S (blue) cone pathway sensitivities were compared in a group of 24 diabetics with either early background retinopathy or no retinopathy. The Farnsworth-Munsell 100-hue test was used to measure hue discrimination, and a two-color increment threshold technique was used to measure S and M cone pathway sensitivities. The results were compared to the level of diabetic retinopathy, to the degree of macular edema, and to the duration of the disease. No significant correlation was found between the Farnsworth-Munsell 100-hue error scores and the level of retinopathy; S cone pathway sensitivity loss, however, correlated significantly with both the level of retinopathy and the degree of macular edema. Our results indicate that measurements of S cone pathway sensitivity using an increment threshold technique provide a more sensitive method than hue discrimination for detecting color vision deficits in early diabetic retinopathy.