title: Normative distribution of visual acuity in 3- to 6-year-old Chinese preschoolers: the Shenzhen kindergarten eye study.
abstract: OBJECTIVE
  To document the distribution of uncorrected visual acuity (UCVA) in a defined population of Chinese preschoolers and to discuss its implications for vision referral.
  
  
  METHODS
  Preschoolers aged 3 to 6 years old were recruited from kindergartens in Shenzen. Uncorrected visual acuity was estimated by using Early Treatment Diabetic Retinopathy Study Tumbling E charts, followed by cycloplegic refraction and ocular examination. The reference population was defined as children without clinically significant ocular abnormalities, with spherical equivalent refraction greater than -0.50 to less than +2.00 diopters (D), astigmatism less than 0.75 D, and anisometropia less than 2.00 D. The age-specific UCVA cutoffs were defined by the line where the single-sided 95th percentile of the reference population fell.
  
  
  RESULTS
  A total of 483 of the 1255 children enrolled were considered the reference population. The monocular UCVA cutoff fell on the line of 20/63 at age 3, 20/50 at age 4, and 20/40 at ages 5 and 6. Using no better than these lines as criteria generated referral rates of 9.4% to 27.8% in the general population at different ages, and detected 83.3% and more than 90.0% of those with myopia and amblyopia, respectively. Using uncorrected interocular difference of two or more lines referred 3.6% to 4.3% of the population but identified only approximately 20.0% of those with amblyopia.
  
  
  CONCLUSIONS
  Visual acuity is still developing in preschoolers even at age 6. Most children with myopia and amblyopia can be identified with age-specific, monocular UCVA cutoffs in vision screening using Tumbling E charts, with tolerable false-positive rates. Further studies are needed to define the age at which children without significant refractive errors reach 20/20 UCVA.
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Xinxing
authors.initials: X
authors.lastname: Guo
authors.affiliation: Department of Ophthalmology, Shenzhen Maternity and Child Healthcare Hospital, Southern Medical University, Shenzhen, China.
authors.forename: Min
authors.initials: M
authors.lastname: Fu
authors.affiliation: Department of Ophthalmology, Shenzhen Maternity and Child Healthcare Hospital, Southern Medical University, Shenzhen, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Lü
authors.affiliation: Department of Ophthalmology, Shenzhen Maternity and Child Healthcare Hospital, Southern Medical University, Shenzhen, China.
authors.forename: Qixia
authors.initials: Q
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Yangfa
authors.initials: Y
authors.lastname: Zeng
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Xiaohu
authors.initials: X
authors.lastname: Ding
authors.affiliation: Research School of Biological Science, Australian National University, Canberra, Australian Capital Territory, Australia.
authors.forename: Ian G
authors.initials: IG
authors.lastname: Morgan
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China Centre for Eye Research Australia, University of Melbourne, Melbourne, Australia.
authors.forename: Mingguang
authors.initials: M
authors.lastname: He
mesh_terms: D002648:Child; D002675:Child, Preschool; D002681:China; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D012016:Reference Values; D012030:Refractive Errors / Q000175:diagnosis; D014787:Vision Tests / Q000379:methods; D014792:Visual Acuity / Q000502:physiology*
keywords: normative distribution; vision screening; visual acuity