The effects of size and analysis method on the performance of the Farnsworth-Munsell D-15 test

Abstract

On the basis that dichromats function as anomalous trichromats when undertaking large-field colour vision tasks, it has been suggested that dichromats will perform better on a large-field D-15 than on a standard D-15. The technique of Vingrys and King-Smith was used to provide a multi-factorial analysis of D-15 plots. When the angular subtense of a colour task exceeds 4°, it is also necessary to use the CIE 1964 Supplementary Standard Observer to calculate chromaticity co-ordinates by which to assess performance. Standard and large-field (7× linear increase) D-15 tests were administered to 17 protanopes and 21 deuteranopes. The results were analysed in terms of the distance travelled in CIE Luv colour space and by the method of Vingrys and King-Smith. The large-field D-15 data were analysed using chromaticities calculated for the CIE 1931 and 1964 Standard Observers.

The change of standard observer created a statistically significant change in angle of about 3°, an increase in S-Index and a decrease in total distance travelled (all p ≤ 0.001 except for deuteranopes, S-Index and C-Index with p < 0.05 and 0.01 respectively). In practice the most significant change is in the angle which could lead to mis-diagnosis of type of defect. There were no statistically significant differences in the dichromats, performance of the standard and large-field D-15 tests (either analysis).