title: Prevalence and associations of anisometropia and aniso-astigmatism in a population based sample of 6 year old children.
abstract: OBJECTIVE
  To study the distribution of anisometropia and aniso-astigmatism in young Australian children, together with clinical and ocular biometry relations.
  
  
  METHODS
  The Sydney Myopia Study examined 1765 predominantly 6 year old children from 34 randomly selected Sydney schools during 2003-4. Keratometry, cycloplegic autorefraction, and questionnaire data were collected.
  
  
  RESULTS
  Spherical equivalent (SE) anisometropia (> or =1 dioptre) prevalence was 1.6% (95% confidence interval (CI) 1.1% to 2.4%). Aniso-astigmatism (>or =1D) prevalence was 1.0% (CI: 0.6% to 1.6%). Both conditions were significantly more prevalent among moderately hyperopic (SE > or =2.0D) than mildly hyperopic (SE 0.5-1.9D) children. Myopic children (SE < or =-0.5D) had higher anisometropia prevalence. Neither condition varied by age, sex, or ethnicity. In multivariate analyses, anisometropia was significantly associated with amblyopia, odds ratio (OR) 29, (CI: 8.7 to 99), exotropia (OR 7.7, CI: 1.2 to 50), and neonatal intensive care unit (NICU) admission (OR 3.6, CI: 1.1 to 12.6). Aniso-astigmatism was significantly associated with amblyopia (OR 8.2, CI: 1.4 to 47), maternal age >35 years (OR 4.0, CI: 1.3 to 11.9), and NICU admission (OR 4.6, CI: 1.2 to 17.2). Anisometropia resulted from relatively large interocular differences in axial length (p<0.0001) and anterior chamber depth (p = 0.0009). Aniso-astigmatism resulted from differences in corneal astigmatism (p<0.0001).
  
  
  CONCLUSIONS
  In this predominantly 6 year old population, anisometropia and aniso-astigmatism were uncommon, had important birth and biometry associations, and were strongly related to amblyopia and strabismus.
authors.affiliation: Centre for Vision Research, Department of Ophthalmology, University of Sydney, Westmead, NSW, Australia.
authors.forename: S C
authors.initials: SC
authors.lastname: Huynh
authors.forename: X Y
authors.initials: XY
authors.lastname: Wang
authors.forename: J
authors.initials: J
authors.lastname: Ip
authors.forename: D
authors.initials: D
authors.lastname: Robaei
authors.forename: A
authors.initials: A
authors.lastname: Kifley
authors.forename: K A
authors.initials: KA
authors.lastname: Rose
authors.forename: P
authors.initials: P
authors.lastname: Mitchell
mesh_terms: D000550:Amblyopia / Q000150:complications; D015858:Anisometropia / Q000150:complications / Q000453:epidemiology* / Q000473:pathology; D001251:Astigmatism / Q000150:complications / Q000453:epidemiology* / Q000473:pathology; D001315:Australia / Q000453:epidemiology; D001724:Birth Weight; D002648:Child; D002658:Developmental Disabilities / Q000150:complications; D004812:Epidemiologic Methods; D005006:Ethnicity; D005099:Exotropia / Q000150:complications; D005123:Eye / Q000473:pathology; D005260:Female; D006801:Humans; D006956:Hyperopia / Q000150:complications; D007231:Infant, Newborn; D007234:Infant, Premature; D008297:Male; D008423:Maternal Age; D009099:Multiple Birth Offspring