Psychophysics of Reading: Xvii

Most people with low vision need magnification to read. Page navigation is the process of moving a magnifier during reading. Modern electronic technology can provide many alternatives for navigating through text. This study compared reading speeds for four methods of displaying text. The four methods varied in their page-navigation demands. The closed-circuit television (CCTV) and MOUSE methods involved manual navigation. The DRIFT method (horizontally drifting text) involved no manual navigation, but did involve both smooth-pursuit and saccadic eye movements. The rapid serial visual presentation (RSVP) method involved no manual navigation, and relatively few eye movements. There were 7 normal subjects and 12 lowvision subjects (7 with central-field loss, CFL group, and 5 with central fields intact, CFI group). The subjects read 70-word passages at speeds that yielded good comprehension. Taking the CCTV reading speed as a benchmark, neither the normal nor low-vision subjects had significantly different speeds with the MOUSE method. As expected from the reduced navigational demands, normal subjects read faster with the DRIFT method (85% faster) and the RSVP method (169%). The CFI group read significantly faster with DRIFT (43%) and RSVP (38%). The CFL group showed no significant differences in reading speed for the four methods. Most people with low vision need magnification to achieve their best reading performance. Sometimes, electronic magnifiers are preferable to optical magnifiers because they can provide higher magnification, greater freedom of eye position, and reverse-contrast (white-on-black) text. In view of the increasing affordability of video and computer technology, it is important for users, clinicians, and designers to know how low-vision reading performance varies with different ways of displaying electronically magnified text. The goal of this study was to compare the reading speeds of low vision subjects on an everyday reading task, using four widely used methods for text presentation. When viewing highly magnified text on a screen, only a few letters of the line of text are visible at one time. The reader must use some technique, termed page navigation, to advance through the text, revealing successive portions of the line of text on the display screen. We studied four methods of page navigation. Two of them required manual movement [closed-circuit TV (CCTV) and MOUSE]. The other two were "automatic" in the sense that sequencing of text on the display was controlled by the electronic device, rather than the reader (DRIFT and RSVP).