Genetic and environmental contributions to strabismus and phoria: evidence from twins

Vision Res. 2009 Oct;49(20):2485-93. doi: 10.1016/j.visres.2009.08.006. Epub 2009 Aug 11.


The causes of manifest (strabismus) and latent (phoria) misalignment of the visual axes are incompletely understood. We calculated genetic and environmental contributions to strabismus based upon a critical review and quantitative meta-analysis of previous strabismus twin studies (n=3418 twin pairs) and calculated contributions to phoria based upon a new twin study (n=307 twin pairs). Our results suggest that genetic liability is necessary to develop strabismus, whereas environmental factors are sufficient to cause most phorias. The different etiologies implied by this work suggest that strabismus and phoria should be carefully distinguished in epidemiological work.

Publication types

  • Research Support, N.I.H., Extramural
  • Review

MeSH terms

  • Adolescent
  • Child
  • Child, Preschool
  • Diseases in Twins / etiology*
  • Diseases in Twins / genetics
  • Evidence-Based Medicine / methods
  • Genetic Predisposition to Disease
  • Humans
  • Meta-Analysis as Topic
  • Risk Factors
  • Strabismus / epidemiology
  • Strabismus / etiology*
  • Strabismus / genetics
  • Twin Studies as Topic / methods
  • Young Adult