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Nicola Anstice, Samantha Watkins, Melissa Thomson, Benjamin Thompson, Robert J Jacobs, Andrew Collins; Comparison of visual acuity across pediatric tests. Invest. Ophthalmol. Vis. Sci. 2014;55(13):439.
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© ARVO (1962-2015); The Authors (2016-present)
The measurement of visual acuity (VA) is central to the management of many ocular diseases and is particularly critical in the diagnosis and treatment of amblyopia. Young children are unable to perform VA measurement on adult charts and, as they progress in age, their VA will be measured with picture optotypes followed by letter matching and letter naming tasks. Therefore it is important to know how measurements obtained on pediatric tests relate to one another. This study provides data on the comparability of 4 pediatric VA tests.
Four pediatric VA charts (crowded linear Kay Pictures, crowded linear Lea Symbols, crowded linear Keeler logMAR and multiple line HOTV) were used to obtain VAs for 25 adult participants and 17 children (4-9 years of age) under best corrected and defocused (+1.00 DS blur) conditions. Measurements were also made using the gold standard Early Treatment of Diabetic Retinopathy Study (ETDRS) chart for comparison. To investigate the legibility of individual Kay pictures optotypes, a separate group of 25 adults had their threshold recognition acuities measured using individual uncrowded Kay pictures and uncrowded Landolt C targets.
In both adults and children, Kay Pictures produced significantly better VA outcomes than all other charts by 1.5-3 lines (p < 0.001). Lea symbols, HOTV and crowded Keeler logMAR charts produced comparable measurements. In children, ETDRS acuity was significantly worse than acuity measurements from all pediatric charts (p < 0.001). In adults, threshold VA for the uncrowded Kay Pictures ranged from 0.40 to -0.59 logMAR, compared with -0.20 logMAR for the Landolt C targets (a 2-4 line equivalent difference). Repeated measures ANOVA revealed significant differences between the legibility of each of the Kay Pictures with the duck being the most easily recognised of all pictures.
Visual acuity measured with the Kay pictures is significantly better than other VA tests. The different legibility between Kay pictures is because it is possible to perceive the shape, angle, tilt and curvature of the optotypes. These features allow the pictures to be recognized at distances greater than predicted from the human resolution limit and the size of details contained within the pictures. This suggests that the use of the Kay Pictures chart should be avoided for children who are likely to progress other recognition charts.
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