Visual Impairment, Adaptation Luminance, and Glare: An Empirical Investigation

Abstract

Visually impaired people primarily rely on their remaining vision. Unfavorable lighting conditions can further hamper this remaining vision. In this context, the present contribution mainly focuses on the evaluation of the visual performance of visually impaired and normally sighted individuals under different lighting conditions. To investigate the visual performance empirically, we developed a test involving different adaptation luminance values. A monitor with adjustable brightness facilitated various tests to determine the visual performance as a function of the adaptation luminance and glare. In addition, the subjective impressions of the visually impaired participants were captured via interviews. The study included 98 visually impaired people and 38 people without eye-related ailments. The interview results suggest that most people with visual disabilities require special lighting conditions. An increased lighting requirement is observed amongst 50% of this group. Moreover, 75% of this group display increased glare sensitivity. Likewise, adaptation problems and critical issues related to non-uniform lighting are manifest. Visually impaired individuals display significant in the visual performance variance at different brightness levels. Individuals with eye disease display a greatly reduced contrast threshold and a higher subjective level of discomfort compared to individuals with normal vision. Most visually impaired individuals require a higher degree of brightness to achieve their maximum personal visual performance. About a quarter of these individuals achieves the optimal visual performance at lower brightness, while displaying an increased sensitivity to glare. In general, glare has a decisive influence on the visual performance of visually impaired people. For general lighting purposes, a predominantly indirect lighting source better accommodates these individuals' requirements.