Past research has not fully ascertained the extent to which people with glaucoma
have difficulties with reading
. This study measures change in reading
speed when letter contrast is reduced, to test the hypothesis that patients with glaucoma
are more sensitive to letter contrast than age-similar visually healthy people.
Fifty-three patients with glaucoma
[mean age: 66 years (standard deviation: 9)] with bilateral visual field (VF) defects and 40 age-similar visually healthy control subjects [mean age: 69 (standard deviation: 8) years] had reading
speeds measured using sets of fixed size, non-scrolling texts on a computer setup that incorporated an eye tracking device. All participants had visual acuity ≥6/9, and they underwent standard tests of visual function including Humphrey 24-2 and 10-2 VFs. Potential non-visual confounders were also tested, including cognitive ability (Middlesex Elderly Assessment of Mental Status Test) and general reading
ability. Individual average raw reading
speeds were calculated from 8 trials (different passages of text) at both 100% and 20% letter contrast.
Patients had an average 24-2 VF MD of −6.5 (range: 0.7 to −17.3) dB in the better eye. The overall median reduction in reading
speed due to decreasing the contrast of the text in the patients was 20%, but with considerable between-individual variation (interquartile range, 8%–44%). This reduction was significantly greater (p = 0.01) than the controls [median: 11% (interquartile range, 6%–17%)]. Patients and controls had similar average performance on Middlesex Elderly Assessment of Mental Status Test (p = 0.71), a modified Burt Reading
ability test (p = 0.33), and a computer-based lexical decision task (p = 0.53) and had similar self-reported day-to-day reading
frequency (p = 0.12).
Average reduction in reading
speed caused by a difference in letter contrast between 100% and 20% is significantly more apparent in patients with glaucoma
when compared with visually healthy people with a similar age and similar cognitive/reading