Abstract
Nineteen young (18-35 year-old) and seven older presbyopic (55-65 year-old, wearing bifocal or progressive glasses) subjects with the same average visual acuity at near distance participated in this full-factorial, repeated measures study with two trial factors: font size (capital letter heights of 1.78, 2.23, and 3.56 mm) and reflective glare. The monitor location was fixed, but subjects were allowed to move their bodies and the chair while performing visually demanding tasks. The productivity improved up to 30% when using a large font size (average visual angle 23.4 arcmin) compared to a smaller font size (14.2 or 16.4 arcmin, p < .0001). The relative contributions of torso flexion (78%), head forward (3%), and chair reposition (4%) to changes in the viewing distance remained constant across font size conditions. Reflective glare had no effect on productivity measures but led to reduction of viewing distance ( p < .0001). There were no significant differences between the two age groups.
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