Quantitative specification of color of the tongue was performed by chroma meter (Minolta CR-100) according to the Commission Internationale de l'Eclarirage 1976 (L*a*b*) Space, the color was analyzed with digital expressions as L* (value), a* (hue of red-green), b* (hue of yellow-blue) and c* (chroma) values.
The difference of the color of the tongue of the patients before and after administration of herbal medicine extracts for 12 weeks was detected by the chroma meter with statistical significance. The change of the color of the tongue of a diabetic female was also able to record on the course of the cerebrovascular accident.
To analyze the correlation between these quantified values and the findings of the tongue by inspection, 116 patients were devided into four groups (whitish, red, dark and violet) according to the color of the tongue by inspection. Most patients in the violet tongue group showed small b* value. As a group the violet group showed significantly smaller b* value than those of the whitish, red and dark groups. In the L*a*b* space as the b* value becomes small the hue becomes blue.
Analyzing the relationship between the diabetic retinopathy and the b* value, color of the tongue of 21 diabetics was examined by the chroma meter. As the result eight patients with diabetic retinopathy indicated significantly smaller b* value than those of 13 patients without retinopathy.
These obsevations suggest that the color of the tongue would be able to specificate quantitatively by chroma meter, the value measured would be correlated to the finding by inspection of the tongue, and that diabetic retinopathy would related with the hue of blue of the tongue detected by this specification system.