Spatial frequency sensitivity in observers with visual discomfort

Three experiments were conducted to obtain evidence of increased sensitivity among observers with visual discomfort to spatial frequencies of 2 to 4 c/deg. In the first experiment the method of paired comparisons was used to obtain judgements of parterns most physically unpleasant and most perceptually distorted to view. It was found that observers classified as experiencing severe visual discomfort reported greatest physical unpleasantness to patterns with a spatial frequency of 2 to 4 c/deg. Perceptual distortion was greatest at 4 and 8 c/deg. The moderate visual discomfort and control groups reported greatest physical discomfort and perceptual distortion at the highest spatial frequencies tested. In Experiment Two the size of the stimulus patterns was substantially reduced. Severe visual discomfort and control groups rated patterns with spatial frequencies between 1 and 16 c/deg for degree of physical unpleasantness and perceptual distortion. With the reduced pattern size it was found that both groups reported grearest difficulty of both types in the higher spatial frequency. range. In Experiment Three contrast senstivity functions were obtained for control and severe visual discomfort groups for spatial frequencies between 1 and 12 c/deg. These were presented when stationery and temporally modulated at 6 HZ. It was found that there was no difference between the groups when temporally modulated gratings were used. When stationery gratings were presented the severe visual discomfort group were more sensitive than the control group at 2 c/deg and less sensitive than this group at 12 c/deg. There was considerable individual variation from the visual discomfort group. The results are discussed in terms of the sustained-transient model of human visual processing