Psychophysics of Reading: Xix

Abstract-Low vision is any chronic form of visual impairment, not correctable by glasses or contacts that adversely affects performance of important everyday visual tasks. Most people with low vision need magnified text to read. On a fixed-size computer screen, the magnification of text trades off against the proportion of the entire screen visible. To read hypertext, simultaneous access to the full-screen page is important for skimming text and for locating hyperlinks. Therefore, people with low vision using magnified text might encounter difficulties reading hypertext, especially when hyperlinks are placed at unpredictable locations (true for most webpages). We investigated hypertext information retrieval as the time taken and number of nodes traversed to answer a series of questions. In Experiment 1, low-vision performance for reading prose and hypertext was compared to normal performance: low-vision performance deficits in hypertext retrieval were predictable from deficits in conventional prose reading. Experiment 2 evaluated the effect of web-page layout on low-vision performance: retrieval performance was severely affected when hyperlinks had unpredictable locations. This extra deficit was eliminated when users were provided with simultaneous access to full-screen layout. Based on these findings, we discuss the accessibility of the Internet by people with low vision.