Fig. 5.
Minimum display width for low-vision individuals. The minimum display widths are presented as a function of visual acuity (VA, bottom x axis) for two viewing distances (40 cm, blue line: y = 1.22*100.96VA and 15 cm, red line: y = 0.46*100.96VA), where y is the minimum display width in centimeters and VA is visual acuity (logMAR). The derivation of the equations for the red and blue lines are provided in SI Appendix, Appendix 2. These equations use a liberal CCC value of nine characters, rounding up to the nearest integer value from the average value of 8.4 found in our experiment for low vision. The CPS corresponding to each VA are shown on the top x axis. The relationship between VA and CPS was obtained from 87 low-vision participants (29–31, a scatter plot is provided in SI Appendix, Appendix 3). Eighteen fonts were included in the analyses (SI Appendix, Appendix 4) with the colored lines showing results for Times New Roman and the gray ribbons representing the results across all fonts*. Dashed vertical lines show examples for mild, moderate, and severe low vision with corresponding acuities of 0.5, 1.0, and 1.5 logMAR. The intersections of these vertical lines with the blue and red diagonal lines represent the minimum display widths for these acuities and reading distances. The display widths of five common digital displays (smart watch, phone, tablet, laptop, and desktop computer) are shown on the right y axis.