title: Risk factors for amblyopia in the vision in preschoolers study.
abstract: OBJECTIVE
  To evaluate risk factors for unilateral amblyopia and for bilateral amblyopia in the Vision in Preschoolers (VIP) study.
  
  
  METHODS
  Multicenter, cross-sectional study.
  
  
  METHODS
  Three- to 5-year-old Head Start preschoolers from 5 clinical centers, overrepresenting children with vision disorders.
  
  
  METHODS
  All children underwent comprehensive eye examinations, including threshold visual acuity (VA), cover testing, and cycloplegic retinoscopy, performed by VIP-certified optometrists and ophthalmologists who were experienced in providing care to children. Monocular threshold VA was tested using a single-surround HOTV letter protocol without correction, and retested with full cycloplegic correction when retest criteria were met. Unilateral amblyopia was defined as an interocular difference in best-corrected VA of 2 lines or more. Bilateral amblyopia was defined as best-corrected VA in each eye worse than 20/50 for 3-year-olds and worse than 20/40 for 4- to 5-year-olds.
  
  
  METHODS
  Risk of amblyopia was summarized by the odds ratios and their 95% confidence intervals estimated from logistic regression models.
  
  
  RESULTS
  In this enriched sample of Head Start children (n = 3869), 296 children (7.7%) had unilateral amblyopia, and 144 children (3.7%) had bilateral amblyopia. Presence of strabismus (P<0.0001) and greater magnitude of significant refractive errors (myopia, hyperopia, astigmatism, and anisometropia; P<0.00001 for each) were associated independently with an increased risk of unilateral amblyopia. Presence of strabismus, hyperopia of 2.0 diopters (D) or more, astigmatism of 1.0 D or more, or anisometropia of 0.5 D or more were present in 91% of children with unilateral amblyopia. Greater magnitude of astigmatism (P<0.0001) and bilateral hyperopia (P<0.0001) were associated independently with increased risk of bilateral amblyopia. Bilateral hyperopia of 3.0 D or more or astigmatism of 1.0 D or more were present in 76% of children with bilateral amblyopia.
  
  
  CONCLUSIONS
  Strabismus and significant refractive errors were risk factors for unilateral amblyopia. Bilateral astigmatism and bilateral hyperopia were risk factors for bilateral amblyopia. Despite differences in selection of the study population, these results validated the findings from the Multi-Ethnic Pediatric Eye Disease Study and Baltimore Pediatric Eye Disease Study.
authors.affiliation: School of Biomedical Sciences, College of Medicine, Drexel University, Philadelphia, Pennsylvania.
authors.forename: Maisie
authors.initials: M
authors.lastname: Pascual
authors.affiliation: Department of Ophthalmology, Scheine Eye Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Jiayan
authors.initials: J
authors.lastname: Huang
authors.affiliation: Department of Ophthalmology, Scheine Eye Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Maureen G
authors.initials: MG
authors.lastname: Maguire
authors.affiliation: College of Optometry, The Ohio State University, Columbus, Ohio.
authors.forename: Marjean Taylor
authors.initials: MT
authors.lastname: Kulp
authors.affiliation: The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
authors.forename: Graham E
authors.initials: GE
authors.lastname: Quinn
authors.affiliation: Pennsylvania College of Optometry, Salus University, Elkins Park, Pennsylvania.
authors.forename: Elise
authors.initials: E
authors.lastname: Ciner
authors.affiliation: College of Optometry, Northeastern State University, Tahlequah, Oklahoma.
authors.forename: Lynn A
authors.initials: LA
authors.lastname: Cyert
authors.affiliation: School of Optometry, University of California at Berkeley, Berkeley, California.
authors.forename: Deborah
authors.initials: D
authors.lastname: Orel-Bixler
authors.affiliation: New England College of Optometry, Boston, Massachusetts.
authors.forename: Bruce
authors.initials: B
authors.lastname: Moore
authors.affiliation: Department of Ophthalmology, Scheine Eye Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania. Electronic address: gsying@mail.med.upenn.edu.
authors.forename: Gui-Shuang
authors.initials: GS
authors.lastname: Ying
mesh_terms: D000550:Amblyopia / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D018479:Early Intervention, Educational; D005260:Female; D006801:Humans; D008297:Male; D016017:Odds Ratio; D012030:Refractive Errors / Q000150:complications / Q000453:epidemiology*; D042262:Retinoscopy; D012307:Risk Factors; D013285:Strabismus / Q000150:complications / Q000453:epidemiology*; D014481:United States / Q000453:epidemiology; D015351:Vision Screening; D014785:Vision, Ocular; D014792:Visual Acuity / Q000502:physiology