Measuring Visual Discomfort

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Abstract
A two-parameter Rasch Rating Scale model was developed to measure visual discomfort. Initially it was found that participants reporting frequent severe headache, reading difficulties of a visual nature, and short effective reading times experienced more severe visual discomfort. The validity of this measurement instrument was tested in four experiments. In Experiments 1 and 2 reports of unpleasant somatic and perceptual side-effects or ratings of unpleasantness were obtained for low, moderate, and high scorers on the Visual Discomfort Scale. It was found that those with higher scores reported a greater number of unpleasant side-effects and rated square-wave patterns across the spatial frequency range, and a letter pattern as more unpleasant and distorted to view than those with low scores on the scale. In Experiments 3 and 4 these subjective findings were extended to performance. Efficiency was measured using a copying and reading task. It was found that those obtaining high scores on the Visual Discomfort Scale performed with less efficiency than others. It was concluded that experience of unpleasant somatic and perceptual side-effects from pattern viewing produce performance difficulties in individuals who we sensitive to pattern. The Visual Discomfort Scale is a reliable and valid measure for testing the extent of these difficulties.