Psychophysics of reading. XV: Font effects in normal and low vision

Purpose. Little is known about the effect of font on low-vision reading. In this study, the authors measured the influence of font in reading with normal and low vision. Methods. Reading acuity, maximum reading speed, and critical print size (the smallest print that can be read with maximum speed) were measured in 50 normal subjects and 42 subjects with low vision. Data were collected using versions of the MNREAD Acuity Chart printed with the Times (proportionally spaced) and Courier (fixed-width) fonts. Results. Reading acuity scores obtained with Courier were better than those obtained with Times for both normal (mean difference, 0.05 logMAR, P < 0.001) and subjects with low vision (0.09 logMAR, P < 0.001). Similarly, critical print sizes measured with Courier were smaller than those measured with Times (mean difference, 0.06 logMAR for normal subjects and subjects with low vision, P < 0.002). Maximum reading speeds for normal subjects were 5% faster with Times than with Courier (P < 0.001), but for subjects with low vision, maximum reading speeds were 10% slower with Times than with Courier (P < 0.05). For print smaller than the critical print size, the reading speeds of normal subjects and subjects with low vision were substantially slower (by as much as 50%) for Times than for Courier. Conclusions. There are small, but significant, advantages of Courier over Times in reading acuity, critical print size, and reading speed for subjects with low vision. For normal subjects, the differences are slighter, with an advantage in reading speed for Times. However, for print sizes close to the acuity limit, choice of font could make a significant difference in both normal and low-vision reading performance.