Purpose: Our interest in reading with peripheral vision centers on its relevance to people with central-field loss, which becomes more prevalent with old age. It has been proposed that the size of the visual span – the number of letters recognized reliably without moving the eyes – is a visual factor limiting reading speed. In this study, we asked whether the size of the visual span and reading speed show similar dependence on age in peripheral vision.

Methods: Seventeen normally sighted young adults (aged 19 to 30 yrs, averaged 23.8) and old adults (aged 55 to 76 yrs, averaged 66) participated. Performance was assessed 10° from fixation in the upper and lower visual fields. Rapid-Serial-Visual-Presentation (RSVP) reading speed was measured. Visual span profiles, measured with trigrams (strings of 3 random letters), are plots of letter-recognition accuracy as a function of letter position. Size of the visual span was defined as the area under this profile, converted to bits of information transmitted.

Results: Visual-span size was larger (27.1 vs. 24.4 bits; p=0.011), and reading speed was higher (191 vs. 124 wpm; p<0.0005) in young than older participants. Visual-span size was larger (26.4 vs. 25.1 bits; p=0.001), and reading speed was higher (169 vs. 146 wpm; p=0.003) in the lower than upper field.

Conclusions: The covariation of reading speed and visual-span size across age and visual-field location supports the view that the size of the visual span is an important factor determining reading speed.