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Ophthalmic Physiol Opt. 2003 Nov;23(6):541-6.

Visual acuity assessment: a comparison of two tests for measuring children's vision.

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School of Optometry, University of Waterloo, Waterloo, Ontario, Canada.



To compare the Kay Picture Test and the logMAR Crowded Test.


Monocular visual acuity measurement was attempted on 103 paediatric subjects (aged between 2.5 and 16 years) attending eye clinics, using each of the visual acuity tests.


The results obtained with the two tests were found to be comparable as confirmed with the Intra-class Correlation Coefficient, which revealed good agreement between the two tests. There was significant correlation between the visual acuity results measured and high conformity in the results from the weaker eye. There was a statistical difference in acuity scores between the tests; the Kay Picture Test gave a lower logMAR score with a mean difference of 0.08 logMAR. This 0.08 difference represents an actual difference of less than one line of acuity measure which can be considered to be clinically insignificant. There was a significant difference in the ability to perform each of the tests under binocular conditions, with more of the 50 children, aged 5 and under, able to perform the Kay Picture Test than the logMAR Crowded Test.


The results obtained with the two tests are comparable. Both tests can be considered to be appropriate for amblyopia detection and the use of picture-based logMAR tests should be considered for younger children.

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