title: Heritability of cilioretinal arteries: a twin study.
abstract: OBJECTIVE
  To determine whether the presence of one or more cilioretinal arteries, a distinct element of the pattern of fundus vessels, is genetically programmed, influenced by environmental factors, or the result of random mechanisms of vascular development.
  
  
  METHODS
  The fundi of 112 pairs of healthy monozygotic and dizygotic twins were examined using digital fundus photography and visual assessment of grayscale fundus photographs and color transparencies to detect the presence of cilioretinal arteries.
  
  
  RESULTS
  Cilioretinal arteries were present in 45.1% of participants and 28.8% of eyes. The majority of cilioretinal arteries, 88.2%, were located temporally, and 11.8% were located nasally. Monozygotic twins had higher concordance rates for cilioretinal arteries than dizygotic twins. Tetrachoric correlations and Mantel-Haenszel odds ratios demonstrated statistically significant evidence of a genetic effect underlying the presence of cilioretinal arteries (P < 0.01). Statistical analysis supported the hypothesis that additive genetic factors influenced the presence of cilioretinal arteries with a heritability of 71.4%, the remaining variance being attributable to nonshared or random environmental factors.
  
  
  CONCLUSIONS
  The presence or absence of one or more cilioretinal arteries in healthy persons is markedly influenced by genetic factors.
authors.affiliation: Department of Ophthalmology, Herlev Hospital, University of Copenhagen, Denmark. ninat@dadlnet.dk
authors.forename: Nina C B B
authors.initials: NC
authors.lastname: Taarnhøj
authors.forename: Inger C
authors.initials: IC
authors.lastname: Munch
authors.forename: Kirsten O
authors.initials: KO
authors.lastname: Kyvik
authors.forename: Birgit
authors.initials: B
authors.lastname: Sander
authors.forename: Line
authors.initials: L
authors.lastname: Kessel
authors.forename: Thorkild I A
authors.initials: TI
authors.lastname: Sørensen
authors.forename: Jesper L
authors.initials: JL
authors.lastname: Hougaard
authors.forename: Michael
authors.initials: M
authors.lastname: Larsen
mesh_terms: D000328:Adult; D019842:Ciliary Arteries / Q000033:anatomy & histology*; D004777:Environment; D005260:Female; D006801:Humans; D040582:Inheritance Patterns / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D011110:Polymorphism, Genetic; D012161:Retinal Artery / Q000033:anatomy & histology*; D014429:Twins, Dizygotic / Q000235:genetics*; D014430:Twins, Monozygotic / Q000235:genetics*