Pupil obscuration mediates the impact of an overhead glare source

Interindividual variability in discomfort from glare has been documented in previous studies, but the causes are not well understood. An observer-related factor that contributes to the variation in perceived glare across individuals is the portion of the face exposed to direct illumination, which is influenced by facial geometry. We hypothesized that individuals with a shaded pupil (due to deeply recessed pupils within the eye socket) would tolerate higher luminance for an overhead glare source compared to individuals with an unshaded pupil. To test this hypothesis, an experiment was conducted where the facial models of 29 participants were collected using a 3D scanner. Participants were seated at a spherical apparatus and asked to set the luminance of a light source positioned 60° above the line of sight using matching and adjustment procedures. For a source positioned 60° above the line of sight, participants with an unshaded pupil set the borderline between comfort and discomfort luminance to a significantly lower value compared to those with a shaded pupil. This can inform more inclusive lighting design guidelines by considering individuals who are likely more sensitive to overhead sources due to their facial geometry.