title: Iris color and visual functions.
abstract: BACKGROUND
  The aim of this study was to evaluate if iris color is associated with differences in visual functions such as intraocular straylight (IOSL), contrast sensitivity (CS), or best-corrected visual acuity (BCVA).
  
  
  METHODS
  In this retrospective cohort study, which is a subgroup analysis of a large prospective trial about visual impairments in European car drivers, we included 853 persons between 20 and 80 years of age and without a history of ocular surgery or any eye disease including cataract. Subjects participated in an ophthalmological examination, grading of lens opacity, and the measurement of visual functions such as IOSL, CS, and BCVA. Dependent on iris color, participants were divided into four groups: light-blue, blue-grey, green-hazel, and brown.
  
  
  RESULTS
  Independent of age, IOSL was significantly (all p values < 0.0001, Fisher's LSD test) higher in participants with light-blue colored iris (1.14 log(IOSL) [95 % CI: 1.11-1.17]) compared to participants with blue-grey (1.07 log(IOSL) [95 % CI: 1.05-1.09]), green-hazel (1.06 log(IOSL) [95 % CI: 1.04-1.08]) or brown (1.06 log(IOSL) [95 % CI: 1.04-1.08]) iris color. CS was also lower in participants with light-blue pigmented irises (1.60 log(CS) [95 % CI: 1.58-1.62]) than in the other groups, but statistically significant (p = 0.013, Fisher's LSD test) only compared to brown iris color. For BCVA we could not found any difference between the four groups.
  
  
  CONCLUSIONS
  We could show in this study that iris color has a significant impact on IOSL and to a lower degree on CS, but not on BCVA. Persons with light-blue iris color who showed significantly higher IOSL values therefore may experience disability glare in daily situations such as driving at night more often than others.
authors.affiliation: Department of Ophthalmology, Paracelsus Medical University Salzburg, Muellner Hauptstrasse 48, 5020 Salzburg, Austria. c.nischler@salk.at
authors.forename: Christian
authors.initials: C
authors.lastname: Nischler
authors.forename: Ralph
authors.initials: R
authors.lastname: Michael
authors.forename: Christine
authors.initials: C
authors.lastname: Wintersteller
authors.forename: Patrick
authors.initials: P
authors.lastname: Marvan
authors.forename: Laurentius J
authors.initials: LJ
authors.lastname: van Rijn
authors.forename: Joris E
authors.initials: JE
authors.lastname: Coppens
authors.forename: Thomas J T P
authors.initials: TJ
authors.lastname: van den Berg
authors.forename: Martin
authors.initials: M
authors.lastname: Emesz
authors.forename: Günther
authors.initials: G
authors.lastname: Grabner
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D015350:Contrast Sensitivity / Q000502:physiology*; D005127:Eye Color / Q000502:physiology*; D005260:Female; D019466:Glare; D006801:Humans; D008027:Light; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012542:Scattering, Radiation; D014792:Visual Acuity / Q000502:physiology*; D055815:Young Adult