A novel instrument to determine hue discrimination

Purpose We report and verify a novel hue discrimination instrument. We also investigate its efficiency to determine hue discrimination in persons with normal color vision. Study design Experimental and clinical investigation. Method and study participants The instrument setup comprises an optical unit and examination unit. The optical unit is composed of the same 2 spectrometers and their controllers, which enables the independent emission of different spectral lights. Two independent bundle fibers connect the optical unit and the examination unit. Two different wavelength lights are illuminated on the bipartite upper and lower circular objectives with a visual angle of 2 degrees in the examination unit. The examinee recognizes the difference in the spectral lights between the bipartite targets. Persons with normal color vision are examined and the findings are confirmed using the Ishihara Test for Colour Deficiency. Results The instrument could generate spectral light from 450 to 650 nm within 2-nm accuracy. The spectral light showed a different light intensity according to the spectral centroid, ranging from 450 to 650 nm, but the difference could be adjusted and was negligible in terms of determination of hue discrimination using the power meter. Three width slits, 0.2 mm, 0.5 mm, and 1.0 mm, to homogenize the light path were investigated. The half-width wavelength was accurate on each spectral centroid; however, the 0.5 mm slit was suitable to generate an efficient light path. The hue discrimination differed among the study participants. In general, at short and long wavelength lights, the hue discrimination range was large: about 15 nm at 450 nm and about 10 nm at 650 nm. Between 470 and 620 nm, the hue discrimination showed good sensitivity and specificity between 8 and 2 nm depending on the targeting wavelength lights. Intraindividual variation was small, ranging from 3 to 1 nm, thus indicating good repeatability. The time to examine the hue discrimination was about 20 min. Conclusion This newly invented instrument using two independent spectrometer units enabled the determination of hue discrimination. The instrument’s sensitivity and specificity including its repeatability were confirmed and indicated that the instrument could be a clinically applicable method.