To compare the classification and severity of congenital color vision deficiency using a Nagel anomaloscope and Farnsworth Munsel 100-hue Test (FM 100-hue). Methods

A total of 394 eyes of 197 patients diagnosed with congenital color vision deficiency were included. Examinations using a Nagel anomaloscope and FM 100-hue were performed, and color vision abnormalities were classified as a protan color defect or deutan color defect by each test, and the degrees of color vision abnormalities were compared. Results

The tests showed 64.3% ( p < 0.001) agreement in the classification of color vision deficiencies. The Nagel anomaloscope was able to classify all cases, whereas 143 eyes (36.3%) could not be classified using the FM 100-hue test. In the case of the same type of color vision abnormality in both eyes, 196 cases (99.5%) using the Nagel anomaloscope and 111 cases (56.3%) using the FM 100-hue were observed. Regarding the degree of color defect, there was a moderate positive correlation between the two tests (r = 0.43; p < 0.001). There were no significant differences in the total error scores between mild anomalous trichromacy and severe anomalous trichromacy as assessed using FM 100-hue ( p = 0.087). Conclusions

The Nagel anomaloscope was a more appropriate test for discerning the degree of color defect and binocular classification. In severity assessments, there was a moderate positive correlation between the two test methods. However, there were no significant differences in the total error scores between mild anomalous trichromacy and severe anomalous trichromacy as assessed using FM 100-hue. Therefore, it was difficult to perform severity classification using the Nagel anomaloscope based on the total error score of the FM 100-hue test.