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U. K. Nair, M. E. Schneck, D. C. Fletcher; Associations of Reading Speed and Error Rates on the SKRead Test With PRL Eccentricity and Scotoma Location. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1166.
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© ARVO (1962-2015); The Authors (2016-present)
To compare reading times and error rates of the Minnesota Reading Acuity (MNRead) and the Smith-Kettlewell Reading Test (SKRead) and study associations with preferred retinal locus (PRL) eccentricity and scotoma location relative to the PRL.
72 better seeing eyes of 72 patients with age-related macular degeneration (AMD) had MNRead, SKRead and visual acuity (VA) testing performed in their initial low vision evaluation. The SKRead chart utilizes the same 60 character per font size format as the MNRead chart but instead of sentences uses random words and letters designed to impede cognitive correction of errors. Reading speed and errors were recorded for each test. Scanning laser ophthalmoscope (SLO) macular function testing was also performed and PRL distance from the fovea was recorded. If scotomas were present, these were noted to be either vertical, to the left, or to the right of the PRL.
Median VA was 20/113. Age median/ range was 84/ 73-97. As expected, reading speeds were lower (28.2 vs. 8.4 seconds/ 60 character block) and error rates (errors/ 60 character block) were higher (2.9 vs 0.4) for the SK Read than the MN read. This was true for all scotoma locations. Error rate and PRL eccentricity were more strongly associated on the SKRead (0.64 characters/deg; R2 = 0.25) than on the MNRead (0.11 characters/deg; R2 = 0.14). When a right-sided scotoma was present, fastest reading times were significantly slower (t-test) on the SKRead (38.8 s) compared with vertical/no scotomas (17.0 s) and left-sided scotomas (20.0 s). Visual acuity did not differ among these groups. Further, reading speed did not differ between those with right scotomas and those with combined right and left scotomas.
As previously found for those with normal vision, low vision patients read more slowly and make more errors when reading random text, compared with continuous text. With increasing PRL eccentricity, low vision patients make more mistakes when reading random text; this finding is much less pronounced for continuous text. Right-sided scotomas significantly hinder reading more than scotomas in other locations.
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