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S.–H. Cheung, M. Kwon, G.E. Legge; Aging Effects on MNREAD Parameters . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5830.
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MNREAD is a continuous–text reading–acuity chart in which reading speed is measured as a function of print size. The MNREAD chart has 19 sentences at print sizes from 1.3 logMAR to –0.5 logMAR in 0.1 log steps. Each sentence has 60 characters (approximately 10 words). The MNREAD chart measures 3 key parameters of visual reading: maximum reading speed (MRS), critical print size (CPS) and reading acuity (RA). Reading speed typically remains constant at the MRS for larger print sizes, and decreases sharply for print sizes smaller than the CPS. RA is the smallest print size that can be read. How do these 3 MNREAD parameters depend on age?
Sixty eight participants were divided into 6 age groups with mean ages: 9 ± 1, 11 ± 1, 13 ± 1, 24 ± 5, 55 ± 3 and 70 ± 5 years. Participants were asked to read the MNREAD sentences aloud as quickly and accurately as possible. At each print size, time to finish the sentence and the number of errors were recorded. These data were used to calculate the reading speeds in words per minute (wpm). Log reading speed as a function of print size was fitted with an exponential function, which had a steep rise at small print sizes and a horizontal asymptote at large print sizes. The asymptote of the fitted function indicated the MRS. CPS was defined as a print size on the fitted function that yielded 90% of the MRS. RA was also calculated.
Mean MRS increased from 139 wpm in the age–9 group to 197 wpm in the age–55 group and then decreased to 185 wpm in the age–70 group. Mean MRS values significantly differ across the age groups (p < 0.001). Regression analysis using age in years as a predictor showed significant aging effects on CPS (p < 0.05). The fitted coefficient for the age predictor was 0.0018, which indicated an increase of 0.018 logMAR in CPS for every 10 years of age. No significant aging effect on RA was found.
Aging effects are different for the 3 MNREAD parameters. Aging affects MRS and CPS, but not RA. MNREAD may detect changes in visual function that cannot be detected by using a letter acuity chart alone. Our findings suggest that different age norms should be used in comparing MNREAD data from patients of different ages.
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