title: Heritability of the spatial distribution and peak density of macular pigment: a classical twin study.
abstract: OBJECTIVE
  To elucidate the heritability of peak density and spatial width of macular pigment (MP) using a Classical Twin Study.
  
  
  METHODS
  Fundus autofluorescence images were obtained at 488 nm from 86 subjects or 43 twin pairs (21 monozygotic (MZ) and 22 dizygotic (DZ)) (27 male, 59 female) aged from 55 to 76 years (mean 62.2 ± 5.3 years). The relative topographic distribution of MP was measured using a grey scale of intensity (0-255 units) in a 7° eccentricity around the fovea. Relative peak MP density (rPMPD) and relative spatial distribution of MP (rSDMP) were used as the main outcome measure in the statistical analysis.
  
  
  RESULTS
  A significantly higher correlation was found within MZ pairs as compared with that within DZ pairs for rPMPD, (r=0.99, 95% confidence interval (95% CI) 0.93 to 1.00) and 0.22, 95% CI -0.34 to 0.71), respectively, suggesting strong heritability of this trait. When rSDMP was compared, there was no significant difference between the correlations within MZ pairs (r=0.48, 95% CI -0.02 to 0.83) and DZ pairs (r=0.63, 95% CI 0.32 to 0.83), thus rSDMP is unlikely to have a considerable heritable component. In addition, there was no difference between any MP parameter when normal maculae were compared with early age-related macular degeneration (AMD) (rPMPD 0.36 vs 0.34, t=1.18 P=0.243, rSDMP 1.75 vs 1.75, t=0.028 P=0.977).
  
  
  CONCLUSIONS
  rPMPD is a strongly heritable trait whereas rSDMP has minimal genetic influence and a greater influence by environmental factors. The presence of macular changes associated with early AMD did not appear to influence any of these pigment parameters.
authors: Centre for Vision and Vascular Science, Queen's University, Belfast, UK. r.e.hogg@qub.ac.uk
authors: R E
authors: RE
authors: Hogg
authors: E L
authors: EL
authors: Ong
authors: M
authors: M
authors: Chamberlain
authors: M
authors: M
authors: Dirani
authors: P N
authors: PN
authors: Baird
authors: R H
authors: RH
authors: Guymer
authors: F
authors: F
authors: Fitzke
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D040582:Inheritance Patterns; D014975:Lutein / Q000235:genetics* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009887:Ophthalmoscopy; D012160:Retina / Q000378:metabolism*; D012168:Retinal Pigments / Q000235:genetics* / Q000378:metabolism; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D024341:Xanthophylls / Q000235:genetics* / Q000378:metabolism; D065146:Zeaxanthins
chemical_list: D012168:Retinal Pigments; D024341:Xanthophylls; D065146:Zeaxanthins; D014975:Lutein