Influence of illumination on results of the hue-discrimination test, Roth 28-Hue desaturated

Abstract

Objectives: To study the influence of different illumination levels on the results of the hue-discrimination test, Roth 28-Hue desaturated. Subjects and methods: The cap-sorting test, Roth 28-Hue desaturated, was conducted using four different illumination levels and four groups of patients taken from a total test cohort of 172 ocularly and generally healthy subjects: 4800 lux (Group 1: 76 subjects; mean age±SD: 30±9 years); 2000 lux (Group 2: 35 subjects; mean age±SD: 31±5 years); 1000 lux (Group 3: 34 subjects; mean age±SD: 31±8 years); and 100 lux (Group 4: 26 subjects; mean age±SD: 30±7 years). The illumination levels were determined with the Minolta Chroma Meter XY-1. Illumination was provided by fluorescent light sources with a balanced spectral distribution and a color-rendering index of 93 (Osram L36W/12 LDL Daylight). Results: No differences could be detected between the illumination level of 4800 lux (average error sum=median±MAD; 42±18) and 2000 lux (average error sum: 40±22). However, examination with 1000 lux showed a small increase in the average error sum (52±21) and the examination with 100 lux showed a statistically significant increase in the average error sum (78±20)(Wilcoxon, p<0.001) but without a preferred disturbance of any particular color axis. Discussion: These differences in error score demonstrate that the results of hue-discrimination tests can be influenced by the illumination level. This must be considered when the results of different color tests are compared. As a standard, we recommend an illumination level of 2000 lux.