Scrolling text can be an effective reading aid for those with central vision loss. Our results suggest that increased interword spacing with scrolling text may further improve the reading experience of this population. This conclusion may be of particular interest to low-vision aid developers and visual rehabilitation practitioners.
The dynamic, horizontally scrolling text format has been shown to improve reading performance in individuals with central visual loss. Here, we sought to determine whether reading performance with scrolling text can be further improved by modulating interword spacing to reduce the effects of visual crowding, a factor known to impact negatively on reading with peripheral vision.
The effects of interword spacing on reading performance (accuracy, memory recall, and speed) were assessed for eccentrically viewed single sentences of scrolling text. Separate experiments were used to determine whether performance measures were affected by any confound between interword spacing and text presentation rate in words per minute. Normally sighted participants were included, with a central vision loss implemented using a gaze-contingent scotoma of 8° diameter. In both experiments, participants read sentences that were presented with an interword spacing of one, two, or three characters.
Reading accuracy and memory recall were significantly enhanced with triple-character interword spacing (both measures, P ≤ .01). These basic findings were independent of the text presentation rate (in words per minute).
We attribute the improvements in reading performance with increased interword spacing to a reduction in the deleterious effects of visual crowding. We conclude that increased interword spacing may enhance reading experience and ability when using horizontally scrolling text with a central vision loss.