Parallel processing under conditions of discomfort glare G Bargary, J L Barbur |
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Applied Vision Research Centre, City University London, United Kingdom
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| A light source causes scattered light on the retina and this in turn reduces object contrast and can also cause discomfort glare. Previous work addressing the effect of glare on vision has focused mainly on the reduction of object contrast caused by light scatter, rather than the often-accompanying discomfort glare. This study compares performance measured with single and multiple stimuli under varying levels of glare. This reveals the cost of parallel processing, but any additional cost in performance across glare levels can be attributable to discomfort glare. Standard contrast-acuity tasks (containing single and multiple stimuli) were carried out with and without an annulus LED glare source. Discomfort glare thresholds were determined prior to testing. All contrast-acuity tasks were carried out in the absence of glare. The tests were then repeated with the glare source set at the subject’s discomfort glare threshold and 0.3 log units above and below this threshold. Parallel processing with multiple stimuli causes increased thresholds when compared to single stimuli. This expected cost was however significantly greater at and above the discomfort glare threshold. Studies that have focused solely on disability glare may be underestimating the adverse effect glaring light sources can have on visual performance. |
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