Visual Fatigue and Spatial Frequency Adaptation to Video Displays of Text

This article proposes that adaptation to the fundamental spatial frequency of lines of text on a video display terminal (VDT) provides a single explanation for a wide variety of reports of visual fatigue by VDT users. Reliable contrast threshold elevations at spatial frequencies of 2, 3, and 5 cycles/deg were found after subjects read single-spaced text on a VDT. This adaptation also reduces sensitivity to spatial frequencies in the range (2 to 6 cycles/deg) largely responsible for the reflexive accommodative response (Bour, 1981. Charman and Heron, 1979), and therefore could account for objective optometric measures of disturbed accommodation as well as some subjective effects of VDT viewing. Implications for video display design and for further research are discussed.

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