title: Crowding ratio in young normally sighted children.
abstract: OBJECTIVE
  To determine normal values of the crowding ratio (CR) in children.
  
  
  METHODS
  Of 62 normally sighted primary school children aged 4-12 years old the CR was determined both for distance and near vision. The examinations were performed using commonly available test charts based on the LEA symbols.
  
  
  RESULTS
  At near, the CR was significantly better than at distance and for all ages <2.0. The upper limit of the CR at distance was <2.0 from age six.
  
  
  CONCLUSIONS
  With commonly available tests the CR can easily be determined in school age children. For children >6 years of age, a CR > 2.0 (i.e. at least 3 lines difference between the result of a single optotype acuity test and a line acuity test) is suspicious and warrants further investigation. It may, for example, be a sign of cerebral visual impairment (CVI).
authors.affiliation: Bartiméus Institute for the Visually Impaired, Ophthalmology, Zeist, Netherlands. mdekker@bartimeus.nl
authors.forename: Marjoke J
authors.initials: MJ
authors.lastname: Dekker
authors.forename: Florine
authors.initials: F
authors.lastname: Pilon
authors.forename: Mieke M C
authors.initials: MM
authors.lastname: Bijveld
authors.forename: Gerard C
authors.initials: GC
authors.lastname: de Wit
authors.forename: Maria M
authors.initials: MM
authors.lastname: van Genderen
mesh_terms: D002648:Child; D002675:Child, Preschool; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008297:Male; D010469:Perceptual Distortion / Q000502:physiology*; D012016:Reference Values; D012684:Sensory Thresholds; D014786:Vision Disorders / Q000503:physiopathology*; D014787:Vision Tests / Q000295:instrumentation; D015348:Vision, Binocular / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology*