Repeatability of reading ability indices in subjects with impaired vision.

PURPOSE Reading speed and acuity measurements are important means of evaluating reading performance in subjects with impaired vision. The MNREAD charts are gradually becoming a popular means of measuring reading ability in low-vision clinics; yet, to date there are no standards of reliability for the visually impaired population. The present study was conducted to determine the coefficients of repeatability for reading speed, reading acuity, and critical print size in a visually impaired population. METHODS Twenty-seven visually impaired subjects (19 women and 8 men; mean age, 72.07; SD, 12.79 years) participated. Test-retest repeatability of the MNREAD charts was assessed at the subject's preferred viewing distance over two sessions by the same examiner. RESULTS The coefficient of repeatability (CR) was found to be +/-0.10 logMAR for reading acuity, +/-0.20 logMAR for critical print size and +/-0.10 logarithm of words per minute for reading speed. The CR was not dependent on visual acuity. CONCLUSIONS As expected, the coefficients of repeatability are higher in visually impaired subjects than in normal subjects. Critical print size measurements have the poorest reliability and precision and should be interpreted with caution.