Reading acuity as a predictor of low-vision reading performance

PURPOSE. Most people with low vision experience difficulty with reading. Reading assessment can provide guidance for prescription of reading aids and strategies for reading rehabilitation. Here we investigate the effectiveness of letter acuity (LA) and reading acuity (RA) as predictors of low-vision reading performance. METHODS. Low-vision subjects (n = 58), young control subjects (n = 52), and older control subjects (n = 14) participated in this study. The low-vision subjects were separated into a Macular group (n = 30) and a Nonmacular group (n = 28) based on whether the diagnoses primarily affected the macular area. LA was measured with the Lighthouse Distance Visual Acuity Chart and RA with the MNREAD Acuity Chart. Reading speeds were obtained across a range of print sizes from the MNREAD test. The MNREAD data were used to estimate required print sizes for three functionally important types of reading for each subject: spot reading (40 words/min [wpm]), fluent reading (80 wpm), and critical print size (required to achieve maximum reading speed). RESULTS. For equal values of LA, the Macular group had significantly worse RA than the Nonmacular group. The differences between vision groups, as well as individual variations within groups, were largely explained by the differences in RA. RA is a better predictor than LA for spot reading size, fluent reading size, and critical print size. CONCLUSIONS. RA may provide more accurate assessment of reading performance than LA for purposes of low-vision reading rehabilitation.