Color vision impairment was examined in patients with type 2 diabetes
mellitus (DM2) without retinopathy. We assessed the type and degree of
distortions of individual color spaces. DM2 patients (n = 32),
and age-matched controls (n = 20) were tested using the
Farnsworth D-15 and the Lanthony D-15d tests. In addition, subsets of caps
from both tests were employed in a triadic procedure (Bimler &
Kirkland, 2004). Matrices of inter-cap
subjective dissimilarities were estimated from each subject's
“odd-one-out” choices, and processed using non-metric
multidimensional scaling. Two-dimensional color spaces, individual and
group (DM2 patients; controls), were reconstructed, with the axes
interpreted as the R/G and B/Y perceptual opponent systems.
Compared to controls, patient results were not significant for the D-15
and D-15d. In contrast, in the triadic procedure the residual distances
were significantly different compared to controls: right eye, P =
0.021, and left eye, P = 0.022. Color space configurations for
the DM2 patients were compressed along the B/Y and R/G dimensions.
The present findings agree with earlier studies demonstrating diffuse
losses in early stages of DM2. The proposed method of testing uses color
spaces to represent discrimination and provides more differentiated
quantitative diagnosis, which may be interpreted as the perceptual color
system affected. In addition, it enables the detection of very mild color
vision impairment that is not captured by the D-15d test. Along with
fundoscopy, individual color spaces may serve for monitoring early
functional changes and thereby to support a treatment strategy.