title: Longitudinal study of anisometropia in Singaporean school children.
abstract: OBJECTIVE
  The purpose of this study was to document the incidence rates of anisometropia, year-by-year prevalences, changes in the intereye difference in spherical equivalent (SE), and its association with myopia progression and axial length changes in a cohort of Singaporean school children.
  
  
  METHODS
  This is a prospective cohort study of Singaporean school children (n = 1979) aged 7 to 9 years who were examined annually with cycloplegic refraction and ultrasonography over a 3-year period.
  
  
  RESULTS
  In the 1908 children without anisometropia at commencement, the 3-year cumulative incidence rate of anisometropia (difference in SE at least 1.0 D) was 144 (7.55%; 95% CI: 6.42-8.85). The mean intereye difference in SE in all children at baseline was 0.29 +/- 0.46 D (SD: 0.46) and increased to 0.44 D (0.59) on the last examination. On the initial examination, 3.6% (95% CI: 2.8-4.4) or 71 children had anisometropia. Of the 59 of 71 children who completed all examinations, only 3 (5.1%) had an increase in the intereye difference in SE by at least 0.5 D, whereas 2 (3.4%) had a decrease of at least 0.5D. The mean intereye difference in SE was stable between visits. The change in intereye difference in SE correlated with the change in intereye axial length (r = 0.43). Compared with the isometropic children, each eye of the anisometropic children had a higher rate of progression of myopia.
  
  
  CONCLUSIONS
  The 3-year incidence of anisometropia was 7.55% in these young Singaporean children. Although the frequency of anisometropia increased with time, the difference in SE between eyes tended to remain stable.
authors.affiliation: Singapore National Eye Center, National University of Singapore, Singapore. louistong@hotmail.com
authors.forename: Louis
authors.initials: L
authors.lastname: Tong
authors.forename: Yiong-Huak
authors.initials: YH
authors.lastname: Chan
authors.forename: Gus
authors.initials: G
authors.lastname: Gazzard
authors.forename: Donald
authors.initials: D
authors.lastname: Tan
authors.forename: Seang-Mei
authors.initials: SM
authors.lastname: Saw
mesh_terms: D015858:Anisometropia / Q000453:epidemiology*; D002648:Child; D018450:Disease Progression; D005123:Eye / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D008297:Male; D009216:Myopia / Q000503:physiopathology; D015995:Prevalence; D011446:Prospective Studies; D012846:Singapore / Q000453:epidemiology; D014463:Ultrasonography