Reading of Dynamically Displayed Text by Low Vision Observers

When compared to the time required to read a normally displayed page of text, low vision observers read faster from a scroll display, in which the text is continuously panned across a computer screen (Legge et al., 1989). They also read faster from a rapid serial visual presentation (RSVP) display in which each word is presented to the same place on a computer screen (Rubin & Turano, 1994). The views seen from the scroll display are similar to what would be seen when a magnifier or other low vision aid is scanned across a page of text. Readers with low vision are reported to read text displayed in this manner about 15% faster than a static page of text (Legge et al., 1989). As Legge et al. point out, this advantage may be due, in part, to the time saved because no return sweeps are needed to reposition the eyes at the beginning of the next line of text. This return sweep is time consuming for normally sighted observers (Rayner, 1978), and even more so for low vision observers who are known to have difficulty with eye movement control (cf. Peli, 1986; Whittaker et al., 1991). This advantage for scroll displays was not seen for normally sighted observers in Legge et al.'s study. In fact, they read 44% slower on average.