Numeral legibility and visual complexity

To enhance the peripheral legibility of numerals we designed three versions of the digits from 1 through 9 by modifying the complexity of each numeral (equivalent to their digit skeleton) while controlling for variations in other physical parameters. Observers identified the different versions of the digits in random three-digit strings, presented within their peripheral visual field. Our results showed that the digit ‘1’should have a narrow design without a crossbar at the bottom, the digits ‘3’ and ‘9’ should benefit from open apertures, and the digit ‘7’ should have a straight leg and no serif at the horizontal bar. The data further demonstrated that crowded digits presented in the periphery of the visual field generally profit from a short morphological skeleton. The findings can improve the identifiability of numbers for readers with normal visions as well as for readers with central visual field loss.