Reading Digital with Low Vision

Abstract

Reading difficulty is a major consequence of vision loss for more than four million Americans with low vision. Difficulty in accessing print imposes obstacles to education, employment, social interaction and recreation. In recent years, research in vision science has made major strides in understanding the impact of low vision on reading, and the dependence of reading performance on text properties. The ongoing transition to the production and distribution of digital documents brings about new opportunities for people with visual impairment. Digital documents on computers and mobile devices permit customization of print size, spacing, font style, contrast polarity and page layout to optimize reading displays for people with low vision. As a result, we now have unprecedented opportunities to adapt text format to meet the needs of visually impaired readers.

Figure 1

A. Topaz Desktop Video Magnifier (Freedom Scientific). B. Amigo Portable Low Vision Electronic Magnifier (Enhanced Vision).

Figure 2

Magnified text on a computer screen using the screen-magnification software ZoomText (Ai Squared).

Figure 3

Two sides of the MNREAD acuity chart used for testing reading vision (Precision Vision).

Figure 4

Sample MNREAD plots of reading speed vs. print size for a subject with normal vision (A) and a subject with low vision (B). Adapted from Calabrese et al. (2016).

Figure 5

Reading Speed (words per minute) is plotted as a function of Angular Print Size (x-height in degrees). Data are taken from four experiments using RSVP (open circles), and scrolling text (filled circles, filled squares, triangles). The data points are means across subjects. Reprinted from Legge & Bigelow, (2011).

Figure 6

Reading speed (words/minute) is plotted as a function of angular print size using Snellen notation. The red curves in the four panels show results for individual AMD subjects, with the upper white curves showing the average data for a group of normally sighted age-matched controls. The yellow stars mark Critical Print Size.

Figure 7

This figure simulates 2° text displayed on an iPad3 and an iPhone5 at viewing distances of 16” (top row) and 8” (bottom row). Only the iPad at 8” exceeds 12 characters per line and 10 words per screen for both Times (left panel) and Courier (right panel).

Figure 8

Samples of text are shown in six fonts. A blurring filter simulates viewing the samples in 18 pt print, at a viewing distance of 40 cm (16”) with four levels of acuity. Which font appears to have best visibility as acuity declines?

Figure 9

Comparison of Courier and Eido Fonts from Bernard et al. (2016).

Figure 10

The 14 lines of Shakespeare's Sonnet CXVI are rendered with seven contrast levels for each of the two contrast polarities. Numbers refer to the Michelson contrast between the letters and the background in the original photograph, where a value of 100% represents maximum contrast. Reprinted from Legge (2007, Fig. 3.1.)