title: Environmental and Genetic Factors Explain Differences in Intraocular Scattering.
abstract: OBJECTIVE
  To study the relative impact of genetic and environmental factors on the variability of intraocular scattering within a classical twin study.
  
  
  METHODS
  A total of 64 twin pairs, 32 monozygotic (MZ) (mean age: 54.9 ± 6.3 years) and 32 dizygotic (DZ) (mean age: 56.4 ± 7.0 years), were measured after a complete ophthalmologic exam had been performed to exclude all ocular pathologies that increase intraocular scatter as cataracts. Intraocular scattering was evaluated by using two different techniques based on a straylight parameter log(S) estimation: a compact optical instrument based in the principle of optical integration and a psychophysical measurement. Intraclass correlation coefficients (ICC) were used as descriptive statistics of twin resemblance, and genetic models were fitted to estimate heritability.
  
  
  RESULTS
  No statistically significant difference was found for MZ and DZ groups for age (P = 0.203), best-corrected visual acuity (P = 0.626), cataract gradation (P = 0.701), sex (P = 0.941), optical log(S) (P = 0.386), or psychophysical log(S) (P = 0.568), with only a minor difference in equivalent sphere (P = 0.008). Intraclass correlation coefficients between siblings were similar for scatter parameters: 0.676 in MZ and 0.471 in DZ twins for optical log(S); 0.533 in MZ twins and 0.475 in DZ twins for psychophysical log(S). For equivalent sphere, ICCs were 0.767 in MZ and 0.228 in DZ twins. Conservative estimates of heritability for the measured scattering parameters were 0.39 and 0.20, respectively.
  
  
  CONCLUSIONS
  Correlations of intraocular scatter (straylight) parameters in the groups of identical and nonidentical twins were similar. Heritability estimates were of limited magnitude, suggesting that genetic and environmental factors determine the variance of ocular straylight in healthy middle-aged adults.
authors.affiliation: Laboratorio de Óptica Universidad de Murcia, Murcia, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Benito
authors.affiliation: Laboratorio de Óptica Universidad de Murcia, Murcia, Spain.
authors.forename: Lucía
authors.initials: L
authors.lastname: Hervella
authors.affiliation: Laboratorio de Óptica Universidad de Murcia, Murcia, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Tabernero
authors.affiliation: Laboratorio de Óptica Universidad de Murcia, Murcia, Spain.
authors.forename: Alexandros
authors.initials: A
authors.lastname: Pennos
authors.affiliation: Laboratorio de Óptica Universidad de Murcia, Murcia, Spain.
authors.forename: Harilaos
authors.initials: H
authors.lastname: Ginis
authors.affiliation: Registro de Gemelos de Murcia, Departamento de Anatomía Humana y Psicobiología, Universidad de Murcia, Murcia, Spain.
authors.forename: Juan F
authors.initials: JF
authors.lastname: Sánchez-Romera
authors.affiliation: Registro de Gemelos de Murcia, Departamento de Anatomía Humana y Psicobiología, Universidad de Murcia, Murcia, Spain.
authors.forename: Juan R
authors.initials: JR
authors.lastname: Ordoñana
authors.affiliation: Servicio de Oftalmología, Hospital Universitario Arrixaca, Murcia, Spain.
authors.forename: Marcos
authors.initials: M
authors.lastname: Ruiz-Sánchez
authors.affiliation: Servicio de Oftalmología, Hospital Universitario Arrixaca, Murcia, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: Marín
authors.affiliation: Laboratorio de Óptica Universidad de Murcia, Murcia, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Artal
mesh_terms: D000328:Adult; D057108:Corneal Wavefront Aberration / Q000235:genetics*; D004200:Diseases in Twins / Q000235:genetics*; D005260:Female; D059647:Gene-Environment Interaction; D006801:Humans; D008027:Light; D008297:Male; D008875:Middle Aged; D012542:Scattering, Radiation; D014429:Twins, Dizygotic / Q000235:genetics*; D014430:Twins, Monozygotic / Q000235:genetics*