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M. E. Mercer, K. J. Penney, J. R. Drover, M. L. Courage, R. J. Adams; Assessment of Visual Acuity in Preschool Children: A Direct Comparison of the Patti Pics and LEA Symbols Tests. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5511.
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With the increasing emphasis on preschool vision screening, there has been tremendous clinical and commercial interest in developing tools for assessing recognition visual acuity, the current gold standard test for diagnosing early spatial vision deficits. However, interpretation of results from current pediatric tests is problematic as there has been little direct comparison of a child’s acuity across different acuity tests, nor any comparative data obtained from adults. Here, in both preschool children and adults, we evaluate the latest versions of the two most promising commercial pediatric visual acuity tests, the Patti Pics and the LEA symbols.
80 eyes from 45 3-6-yr-olds were tested in a single session with both the illuminated (170 cd/m2) distance (3m) chart versions of the Lea Symbols (available widely) and the Patti Pics (Precision Vision) tests. Both tests follow the MassVat format and the size of the optotypes in each ranged from 0.9 to -0.3 logMAR units (Snellen Equivalents: 20/200 to 20/8). A small sample of adults (n=12) were also tested with both pediatric charts as well as with a Sloan letter acuity chart.
Preschoolers’ visual acuity was slightly but consistently lower on the Patti Pics chart (Mean logMAR = 0.21, Snellen = 20/33) compared to the Lea chart (Mean logMAR = 0.15, Snellen = (20/29). This difference was significant (t = 4.53, p < 0.0001) and represented about half a line difference between the charts. In only 2 eyes (2.5% of the sample), was acuity better on the Patti Pics chart. Like preschoolers, adults also showed slightly lower acuity on the Patti Pics test, and adult Patti Pics estimates appeared to be a better approximation of adult Sloan letter acuity.
As these tests are used widely and at times interchangeably, the small but consistent difference between tests is important to consider, especially for setting fixed visual acuity screening referral criteria and or clinical decision making. Although both tests appear equal in both test time and patient compliance, the Patti Pics have the advantage of greater consistency with an adult acuity test that possesses standardized optotype design, a benefit that may yield more sensitivity and interpretability of early visual pathology.
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