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Crowded Letter and Crowded Picture LogMAR acuity in Children with Amblyopia: a quantitative comparison.

O'Boyle, Cathy, Chen, Sean and Little, Julie-Anne (2016) Crowded Letter and Crowded Picture LogMAR acuity in Children with Amblyopia: a quantitative comparison. British Journal of Ophthalmology, 100 . [Journal article]

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URL: http://bjo.bmj.com/content/early/2016/07/07/bjophthalmol-2015-307677.full

DOI: 10.1136/bjophthalmol-2015-307677


Aims: Clinically, picture acuity tests are thought to overestimate visual acuity (VA) compared with letter tests, but this has not been systematically investigated in children with amblyopia. This study compared VA measurements with the LogMAR Crowded Kay Picture test to the LogMAR Crowded Keeler Letter acuity test in a group of young children with amblyopia. Methods: 58 children (34 male) with amblyopia (22 anisometropic, 18 strabismic and 18 with both strabismic/anisometropic amblyopia) aged 4-6 years (mean=68.7, range=48-83 months) underwent VA measurements. VA chart testing order was randomised, but the amblyopic eye was tested before the fellow eye. All participants wore up-to-date refractive correction. Results: The Kay Picture test significantly overestimated VA by 0.098logMAR (95% LOA, 0.13) in the amblyopic eye and 0.088logMAR (95% LOA, 0.13) in the fellow eye respectively (p<0.001). No interactions were found from occlusion therapy, refractive correction or type of amblyopia on VA results (p>0.23). For both the amblyopic and fellow eyes, Bland-Altman plots demonstrated a systematic and predictable difference between Kay Picture and Keeler Letter charts across the range of acuities tested (Keeler acuity: amblyopic eye 0.75 to -0.05 logMAR; fellow eye 0.45 to -0.15 logMAR). Linear regression analysis (p<0.00001) and also slope values close to one (amblyopic 0.98, fellow 0.86) demonstrate that there is no proportional bias.Conclusion: The Kay Picture test consistently overestimated VA by approximately 0.10logMAR when compared to the Keeler Letter test in young children with amblyopia. Due to the predictable difference found between both crowded logMAR acuity tests, it is reasonable to adjust Kay Picture acuity thresholds by +0.10logMAR to compute expected Keeler Letter acuity scores.

Item Type:Journal article
Keywords:Amblyopia, Kay Pictures, Visual Acuity, Crowding
Faculties and Schools:Faculty of Life and Health Sciences > School of Biomedical Sciences
Faculty of Life and Health Sciences
Research Institutes and Groups:Biomedical Sciences Research Institute
Biomedical Sciences Research Institute > Optometry and Vision Science
ID Code:35001
Deposited By: Dr Julie-Anne Little
Deposited On:18 Jul 2016 08:31
Last Modified:17 Oct 2017 16:24

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