To determine predictors of success in reading
with low vision aids, in terms of reading
acuity, optimum acuity reserve, and maximum reading
speed, for observers with vision loss from various causes.
One hundred people with vision loss affecting their daily lives participated. Clinical visual function
measurements of distance acuity, contrast sensitivity, binocular threshold visual fields, and near reading
performance with a MNRead chart at 40 cm were obtained. Reading
performance aided by habitual low vision aids was also assessed with a MNRead chart.
acuity was best predicted by clinical reading
acuity and contrast sensitivity. For most observers, a 2:1 acuity reserve was sufficient to achieve near-maximum reading
speed, but one-third of observers with aided reading
acuity better than 1.2M required a higher acuity reserve. Aided maximum reading
speed was best predicted by clinically assessed reading
speed and by clinical reading
People with vision impairment are likely to achieve 1M with a low vision aid if their clinically assessed reading
acuity is better than 0.85 logMAR. If acuity is worse than this, but contrast sensitivity is better than 1.05 logCS, 1M is also likely to be achieved. A 2:1 acuity reserve is adequate for 75% of observers, but those with good aided reading
acuity may require further magnification to achieve best reading
speeds. Fluent reading
(>80 words per minute) is likely to be achieved if an observer reads fluently with large print at a fixed working distance and if clinically assessed reading
acuity is better than 1.0 logMAR.