Optimized light sources for enhancing color discrimination in people with low vision

Abstract

This research was divided into 2 parts. The aim of the first part was to investigate if illuminance level and correlated color temperature (CCT) had an effect on mobility performance in people with low vision compared to the elderly wearing simulated low vision glasses and the elderly with naked eyes. We also compared their mobility in pouring liquid to a specified level. The second part’s aim was to optimize combinations of light emitting diode (LED) channels that increased the discrimination of color in people with low vision. The research procedure of the first part involved 7 lighting conditions, with different illuminance levels and CCTs, and walking course with an obstacle. The participants walked along the walking course at their normal speed and avoid contacting the obstacles. The walking speed and contact score indicated mobility performance. We found that the illuminance levels and the CCTs, in the experiment, did not influence the walking mobility of the low vision and the elderly with low vision glasses. However, the walking speed obtained from a different type of low visions differed under low illuminance level. Moreover, the walking speed of the elderly with low vision glasses was slower than the low vision. The deviation of the specified scale in pouring liquid by the low vision was less than by the elderly with low vision glasses. The elderly with naked eyes had better mobility performance than the low vision. The research procedure of the second part involved color discrimination in colored pairs under 14 LEDs individually, having different spectral power distribution (SPD), by the participants wearing cloudy and blurred simulated low vision glasses (CVG and BVG). The selected channels yielded the lowest color difference (∆E*ab) between the pairs determined in psychophysics experiment. The least color difference of the colored pairs, that could be enhanced, indicated the performance of the SPD or LED channels. We combined the optimized SPDs from 3 regions (short, medium and long) of wavelength, obtained from CVG and BVG, and made white light from them for testing color discrimination of 200 colored pairs. Finally, the optimized white lights were tested by participants with simulated low vision glasses and the patients with low vision. The results were indicated that R-RP-P pairs and BG-G pairs were enhanced by CV-L and Y-YR pairs and PB-B pairs were enhanced by BV-L because of the different SPD of lighting. The proposed combinations of SPDs showed better performance and gave the lower average color difference threshold than the commercial white light. Comparison of 3 of proposed lighting by simulated low vision observers and the low vision patients showed that the color difference (∆E*94) thresholds were similar.