[Study of color perception using a new color test and desaturated panel D 15 in normal subjects and diabetics]

The authors used two tests (the Lanthony's New Color Test and the desaturated Panel D 15 test) to evaluate color vision in 235 subjects (235 eyes) of which 80 normal and 155 diabetic (85 with background retinopathy and 70 without retinopathy, as demonstrated by fluorescein angiography). The diabetic patients with maculopathy or macular oedema, with mixed or proliferative retinopathy, or with any form of advanced degenerative retinopathy were excluded from this study. The New Color Test was performed in accordance with Lanthony's standardized method, applying only the separation phase (to quantifying the color perception defect, if any) in photopic illuminance conditions at 250 lux. The desaturated Panel D 15 (qualitative classification test) has been performed at illuminance of 500 lux. Both normal and diabetic subjects were divided into two age groups (below and above 45 years) and the discriminatory value of two tests has been assessed in relation to age, diabetes and background retinopathy. The New Color Test showed a highly significant difference between normal subjects and diabetics of comparable age with background retinopathy. The was also a highly significant difference between diabetics with and without retinopathy. On the other hand, the difference between normal subjects and diabetics without retinopathy proved significant in the below-45 age group and not significant in the above-45 age group. The results obtained in the desaturated Panel D 15 test have been similar: below the 45 years of age all differences among the three subject groups proved significant, whereas in the above-45 age group no significant differences were observed. The authors conclude that, in the below-45 age group, both tests yield abnormal results in presence of background retinopathy (9% and 17% false positives in the NCT and desaturated Panel D 15 test respectively), but fail to discriminate adequately between normal subjects and diabetics without retinopathy. The latter, in fact, often show normal tests responses (poor sensitivity). In the above 45-age group both tests show reduced discriminatory capability. In particular, the specificity proves to be very poor (44% and 85% false positives respectively). This due to the deterioration of color perception produced by aging. Lastly, both tests confirmed that, in diabetic retinopathy, defective color perception takes the form of a blue-yellow confusion axis.