Influence of macular pigment on the sensitivity to discomfort glare from daylight

Abstract

Understanding the factors that influence the human perception of glare is necessary to properly address glare risks in buildings and achieve comfortable visual environments, especially in the workplace. Yet large inter-individual variabilities in glare perception remain unexplained and thus uncovered by the current empirical glare models. We hypothesize that this variability has an origin in the human retina, in particular in the density of macular pigments present in its central area, which varies between individuals. Macular pigments are known to absorb blue light and attenuate chromatic aberration, thus reducing light scatter. This study presents the outcomes of the first experiment ever conducted in a daylit office environment, in which glare sensitivity and macular pigment density were measured and compared for 110 young healthy individuals, along with other ocular parameters. The participants were exposed to different glare conditions induced by the sun filtered through either color-neutral or blue-colored glazing. In neutral daylight conditions with sun disc in the near periphery, neither macular pigment nor any other investigated ocular factors have an impact on discomfort glare perception whereas glare perception in conditions with the blue-colored sun disc in the near periphery was found to be correlated with macular pigment optical density.

Figure 1

Density plots of measured ocular parameters of the participants: (a) MPOD values of participants’ eyes in Experiment I and (b) Experiment II, (c) Photostress recovery time and d: mean iris thickness of the participants’ right eye in experiment I.

Figure 2

Measured photometric and spectral characteristics of daylight during the experiments. (a) Sun luminance (cd/m²) and (b) DGP values measured from HDR images (taken at participants’ eye level) shown as the boxplots with median values for each experimental condition. (c) Mean normalized SPDs of the sun disc (dia 5.8°) and (d) the SPDs of daylight measured at participants’ eye level for each condition. (e) Mean alpha-opic irradiance values calculated for the sun-disc (dia ~ 5.8°) and (f) calculated at the eye level for cones and ipRGCs photoreceptor types normalized over each experimental condition.

Figure 3

Distribution of participants’ responses to discomfort glare: on binary response labels (top) and on Likert four-point labels (bottom).

Figure 4

Box plots comparing the mean differences of MPOD between the two groups of participants less sensitive and more sensitive to glare under blue-colored and color-neutral glazing.

Figure 5

Participant performing the test, left: in experiment I under color-neutral glazing; right: in experiment II under blue-colored glazing (Top), Test procedure at EPFL (Bottom).

Figure 6

(a) Example fisheye images of the test condition in Experiment I and II, (b) Falsecolor version of the images showing the scene luminance distribution, (c) variation in the sun luminance between the experimental conditions.

Figure 7

Spectral transmittances of the ‘sun window’ glazing used in experiment I and experiment II.