A study of mechanisms for discomfort glare Y Jia, G Bargary, J L Barbur |
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Applied Vision Research Centre, City University London, United Kingdom
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| The presence of a bright light source in the visual field can generate visual discomfort, often described as ‘discomfort glare’. The mechanisms underlying discomfort glare remain poorly understood, even after 50 years of multidisciplinary research [Mainster et al., 2012, American Journal of Ophthalmology, 153(4), 587-593]. However, any mechanistic account of discomfort glare must begin with a given quantity of light reaching the retina, and yet previous studies have focused mostly on properties of the glare-source. In this study, the pupil size was measured throughout, while glare-source size, eccentricity and background luminance were varied. The participants were required to view a source of light presented against a simulated residential street background in the form of uniform flashes of light of varying intensity. Discomfort glare thresholds were estimated using a staircase procedure; the dependent variable was retinal illuminance, a quantity proportional to the amount of light per unit area of the retina. It was found that at the threshold for discomfort glare, retinal illuminance is approximately constant and independent of glare-source size, background luminance and eccentricity. A model based on saturation of photoreceptor signals in the retina that accounts for both the glare thresholds and the corresponding pupil responses will be described. |
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