title: The heritability of dry eye disease in a female twin cohort.
abstract: OBJECTIVE
  We estimated the relative importance of genes and environment in dry eye disease (DED) using a classic twin study.
  
  
  METHODS
  A large sample of 3930 female monozygotic and dizygotic twins from the UK Adult Twin Registry (TwinsUK) was questioned about the presence of a DED diagnosis and about DED symptoms in the preceding 3 months. In addition, a subset of 606 twins was examined for several dry eye signs. Genetic and environmental effects were estimated using maximum likelihood structural equation modeling.
  
  
  RESULTS
  All DED outcome variables showed higher correlation in monozygotic twin pairs than in dizygotic twin pairs, suggesting genes have a contributory role in DED. The DED symptoms showed a heritability of 29% (95% confidence interval [CI], 18%-40%). A clinician's diagnosis of DED with concurrent use of artificial tears showed a heritability of 41% (95% CI, 26%-56%). Estimates of the heritability of DED signs were 25% (95% CI, 7%-42%) for interblink interval, 58% (95% CI, 43%-70%) for Schirmer value, 40% (95% CI, 25%-53%) for tear osmolarity, and 78% (95% CI, 59%-90%) for the presence of blepharitis. The unique environment explained the remainder of the variance. We found no significant heritability for tear breakup time.
  
  
  CONCLUSIONS
  Genetic factors contribute moderately to the diagnosis, symptoms, and the signs of DED. Compared to other ocular phenotypes, the lower heritability might reflect some of the difficulties in objective phenotyping of DED in a population-based sample. However, future genetic studies are now justified and may help in unraveling the pathophysiology of DED.
authors.affiliation: Department of Twin Research & Genetic Epidemiology, King's College London, St. Thomas' Hospital, London, United Kingdom.
authors.forename: Jelle
authors.initials: J
authors.lastname: Vehof
authors.affiliation: Department of Epidemiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Bin
authors.initials: B
authors.lastname: Wang
authors.affiliation: Department of Twin Research & Genetic Epidemiology, King's College London, St. Thomas' Hospital, London, United Kingdom.
authors.forename: Diana
authors.initials: D
authors.lastname: Kozareva
authors.affiliation: Department of Twin Research & Genetic Epidemiology, King's College London, St. Thomas' Hospital, London, United Kingdom.
authors.forename: Pirro G
authors.initials: PG
authors.lastname: Hysi
authors.affiliation: Department of Epidemiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Harold
authors.initials: H
authors.lastname: Snieder
authors.affiliation: Department of Twin Research & Genetic Epidemiology, King's College London, St. Thomas' Hospital, London, United Kingdom Department of Ophthalmology, King's College London, St. Thomas' Hospital, London, United Kingdom.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Hammond
mesh_terms: D003941:Diagnostic Techniques, Ophthalmological; D004200:Diseases in Twins; D015352:Dry Eye Syndromes / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics*; D005260:Female; D005500:Follow-Up Studies; D020022:Genetic Predisposition to Disease; D006801:Humans; D008875:Middle Aged; D015995:Prevalence; D012042:Registries; D011795:Surveys and Questionnaires; D014429:Twins, Dizygotic / Q000235:genetics*; D014430:Twins, Monozygotic / Q000235:genetics*; D006113:United Kingdom / Q000453:epidemiology
keywords: DED; OSDI; dry eye disease; environment; genetics; heritability; sicca syndrome