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Özlem Engin, Annemarie Romers, Xanne Slot, Mari Gutter, Martha Tjon Fo Sang, Maria Fronius, Dominique Despriet, Huibert J. Simonsz; Recognizability Of Equally Sized And Spaced Optotypes From Amsterdam Picture Chart, Tumbling-E, Lea Symbols, EDTRS And Landolt-C In Health And Amblyopia. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1578.
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Picture charts were formerly calibrated for the age group the charts were used for. Accordingly, acuity measured with the Amsterdam Picture Chart (APK) is 5/5 in an average 4-year-old but 0.8 a year later with Landolt-C. To obtain conversion factors between the charts, first the recognizability of the optotype shapes should be known.
Logarithmic charts were made (Figure) with Landolt-C (L-C), Lea Symbols, Tumbling-E (T-E), APK and ETDRS optotypes with identical size, distance (4 and 1 optotypes) and ratio. First, we recruited 100 healthy students without uncorrected refractive error. Charts were randomly presented under DIN EN ISO 8596 and 8597 conditions. A row was passed if 3/5 or 6/10 optotypes were read correctly. Thresholds with Lea, T-E, APK and EDTRS relative to that with L-C were calculated. Error rates were calculated per optotype and orientation. Secondly, children with newly diagnosed amblyopia (≥2 lines acuity difference) were examined in a similar fashion.
Average testing time was 40 minutes in students. Threshold size of Lea, T-E, APK and ETDRS was 1.167, 1.024, 1.291, 0.994 as compared to L-C optotypes. The most difficult Lea optotype was read incorrectly 33% more often than the easiest optotype, until the threshold was reached. The most difficult APK and ETDRS optotype was read incorrectly 100% more often than the easiest optotype. There was no orientation preference for T-E and L-C. Results in amblyopia are forthcoming.
Recognizability was good for ETDRS and L-C, but low for APK optotypes.
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