title: The inheritance of peripapillary atrophy.
abstract: OBJECTIVE
  To estimate the relative importance of genes and environment in peripapillary atrophy type beta (beta-PPA) in a classic twin study.
  
  
  METHODS
  Female twin pairs (n = 506) aged 49 to 79 years were recruited from the St. Thomas' UK Adult Twin Registry. Peripapillary atrophy was identified from masked grading of stereoscopic optic disc photographs. Structural equation modeling was performed using Mx with polychoric correlations of beta-PPA and refractive error (divided into deciles).
  
  
  RESULTS
  Beta-PPA prevalence was 25.1% and did not vary with zygosity. Case-wise concordance for right eyes was 0.76 (95% CI, 0.57-0.88) for monozygotic (MZ) and 0.37 (95% CI, 0.15-0.56) for dizygotic (DZ) pairs. Multivariate modeling suggested additive genetic effects and individual environment, with no shared environment or dominant genetic effect. Beta-PPA heritability was 0.70 (95% CI, 0.54-0.83), and spherical equivalent 0.88 (95% CI, 0.85-0.91); age had no significant effect on variance. The genetic correlation between beta-PPA and spherical equivalent was -0.21. However, only 3% of the genetic variance of beta-PPA was explained by genetic factors in common with refractive error, with 67% explained by specific genetic factors for beta-PPA. Of the 30% of variance explained by unique environmental factors, only 3% was explained by these factors in common with environmental factors involved in refractive error.
  
  
  CONCLUSIONS
  The presence of beta-PPA, a frequent ocular finding known to be associated with open-angle glaucoma, appears to be under strong genetic control, with only a small amount of this genetic effect shared with genes involved in myopia.
authors.affiliation: Centre for Vision Research, University of Sydney, Australia. phealey@glaucoma.net.au
authors.forename: Paul R
authors.initials: PR
authors.lastname: Healey
authors.forename: Paul
authors.initials: P
authors.lastname: Mitchell
authors.forename: Clare E
authors.initials: CE
authors.lastname: Gilbert
authors.forename: Anne J
authors.initials: AJ
authors.lastname: Lee
authors.forename: Dongliang
authors.initials: D
authors.lastname: Ge
authors.forename: Harold
authors.initials: H
authors.lastname: Snieder
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Spector
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Hammond
mesh_terms: D000368:Aged; D001284:Atrophy / Q000235:genetics; D002829:Choroid / Q000473:pathology*; D004200:Diseases in Twins / Q000235:genetics*; D005260:Female; D006801:Humans; D040582:Inheritance Patterns; D008875:Middle Aged; D010857:Pigment Epithelium of Eye / Q000473:pathology*; D015995:Prevalence; D012030:Refractive Errors / Q000235:genetics*; D012042:Registries; D014429:Twins, Dizygotic / Q000235:genetics; D014430:Twins, Monozygotic / Q000235:genetics