Crowded task performance in visually impaired children: magnifier versus large print
SourceGraefe'S Archive for Clinical and Experimental Ophthalmology, 251, 7, (2013), pp. 1813-1819
Article / Letter to editor
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Graefe'S Archive for Clinical and Experimental Ophthalmology
SubjectDCN MP - Plasticity and memory; NCEBP 2: Evaluation of complex medical interventions
BACKGROUND: This study compares the influence of two different types of magnification (magnifier versus large print) on crowded near vision task performance. METHODS: Fifty-eight visually impaired children aged 4-8 years participated. Participants were divided in two groups, matched on age and near visual acuity (NVA):  the magnifier group (4-6 year olds [n = 13] and 7-8 year olds [n = 19]), and  the large print group (4-6 year olds [n = 12] and 7-8 year olds [n = 14]). At baseline, single and crowded Landolt C acuity were measured at 40 cm without magnification. Crowded near vision was measured again with magnification. A 90 mm diameter dome magnifier was chosen to avoid measuring the confounding effect of navigational skills. The magnifier provided 1.7x magnification and the large print provided 1.8x magnification. Performance measures:  NVA without magnification at 40 cm,  near vision with magnification, and  response time. Working distance was monitored. RESULTS: There was no difference in performance between the two types of magnification for the 4-6 year olds and the 7-8 year olds (p's = .291 and .246, respectively). Average NVA in the 4-6 year old group was 0.95 logMAR without and 0.42 logMAR with magnification (p < .001). Average NVA in the 7-8 year was 0.71 logMAR without and 0.01 logMAR with magnification (p < .001). Stronger crowding effects predicted larger improvements of near vision with magnification (p = .021). CONCLUSIONS: A magnifier is equally effective as large print in improving the performance of young children with a range of visual acuities on a crowded near vision task. Visually impaired children with stronger crowding effects showed larger improvements when working with magnification.
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