Purchase this article with an account.
Yu-Chi Tai; Optimal Viewing Distance for Reading Text of Small Font. Invest. Ophthalmol. Vis. Sci. 2016;57(12):210.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The use of digital electronic devices is prevailed in the developed world (e.g., 87% of Americans, 90% of Germans, and 80% of Taiwanese use computers daily). It’s common for people to spend more than 8 hours a day on computer devices. Young adults and teens even spend more than 11 hours viewing electronic displays. Growing with the screening time is the complaint of viewing discomfort, such as blurry vision, strained eyes, dry eyes, and fatigue. This study sought to determine the optimal distance for viewing text of small font size onscreen and its effect on the accommodative system.
Viewing distance and real-time accommodation were measured while subjects read articles on a tablet with text of 4-, 7-, 1--, and 12-point font. With each font size, subjects (N=43, 18-39 yo, avg.=24.39) were asked to set the tablet at the furthest distance that they can read and read for 30 minutes while their accommodation (Spherical Equivalent Refraction, SER) and reading speed were recorded, followed by measurement of accommodative amplitude (AA), accommodative facility (AF), and self-rating of viewing discomfort. The same protocol was repeated with the nearest and the preferred viewing distance.
While the nearest viewing distance stays the same (12 cm), the furthest (48, 80, 98, 113 cm for 4-, 7-, 10-, and 12-point font, respectively) and the preferred (28, 41, 50, and 57 cm) viewing distance increased with font size. In the meantime, SER (-2.23, -1.98, -1.99, -1.76 diopters), AA and visual discomfort (2.6, 2.0, 1.5, 1.3 on a 4-point scale) decreased with larger font size.
Although subjects can read at anywhere between the furthest and the nearest distances, the preferred distance was located in the middle and decreased as text got smaller. Close distances increased the accommodative demand, which exacerbates viewing discomfort. Practitioners need to consider the effect of closer viewing distance on the oculomotor system before treating people with asthenopia.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
This PDF is available to Subscribers Only