title: Crowded task performance in visually impaired children: magnifier versus large print.
abstract: 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): [1] the magnifier group (4-6 year olds [n = 13] and 7-8 year olds [n = 19]), and [2] 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 1.7× magnification and the large print provided 1.8× magnification. Performance measures: [1] NVA without magnification at 40 cm, [2] near vision with magnification, and [3] 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.
authors.affiliation: Bartiméus, Institute for the Visually Impaired, Zeist, The Netherlands. bhuurneman@bartimeus.nl
authors.forename: Bianca
authors.initials: B
authors.lastname: Huurneman
authors.forename: F Nienke
authors.initials: FN
authors.lastname: Boonstra
authors.forename: Cornelis A
authors.initials: CA
authors.lastname: Verezen
authors.forename: Antonius H N
authors.initials: AH
authors.lastname: Cillessen
authors.forename: Ger
authors.initials: G
authors.lastname: van Rens
authors.forename: Ralf F A
authors.initials: RF
authors.lastname: Cox
mesh_terms: D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007909:Lenses; D008297:Male; D008402:Mass Media; D011932:Reading; D012682:Sensory Aids; D013647:Task Performance and Analysis; D015354:Vision, Low / Q000503:physiopathology* / Q000534:rehabilitation; D014792:Visual Acuity / Q000502:physiology*; D019987:Persons with Visual Disabilities