title: Supplementation with the carotenoids lutein or zeaxanthin improves human visual performance.
abstract: BACKGROUND
  Macular pigment (MP) is found in diurnal primate species when vision spans a range of ambient illumination and is mediated by cone and rod photoreceptors. The exact role of MP remains to be determined. In this study we investigate two new hypotheses for possible MP functions.
  
  
  OBJECTIVE
  As MP absorption coincides partly with that of rhodopsin, MP may reduce rod signal effectiveness in the mesopic range, thus extend the usefulness of cone-mediated vision into the mesopic range. Forward light scatter in the eye can reduce retinal image contrast. If blue light contributes significantly to intraocular scatter, selective blue light absorption by MP could reduce the effects of scatter.
  
  
  METHODS
  We investigated 34 subjects from a carotenoid supplementation trial. The measurements included high mesopic contrast acuity thresholds (CATs), macular pigment optical density (MPOD), wavefront aberrations, and scattered light. The measurements were made after 6 months of daily supplementation with zeaxanthin (Z, OPTISHARP), lutein (L), a combination of the two (C), or placebo (P), and again after a further 6 months of doubled supplementation.
  
  
  RESULTS
  The data reveal a trend toward lower CATs in all groups supplemented, with a statistically significant improvement in the lutein group (p = 0.001), although there was no correlation with MPOD. Light scattering in the eye and the root-mean-square wavefront aberrations show decreasing trends as a result of supplementation, but no correlation with MPOD.
  
  
  CONCLUSIONS
  The results suggest that supplementation with L or Z increases MPOD at the fovea and at 2.5 degrees , and that supplementation can improve CATs at high mesopic levels and hence visual performance at low illumination.
authors.affiliation: Applied Vision Research Centre, Department of Optometry and Visual Science, City University, London, UK.
authors.forename: Jessica
authors.initials: J
authors.lastname: Kvansakul
authors.forename: Marisa
authors.initials: M
authors.lastname: Rodriguez-Carmona
authors.forename: David F
authors.initials: DF
authors.lastname: Edgar
authors.forename: Felix M
authors.initials: FM
authors.lastname: Barker
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Köpcke
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schalch
authors.forename: John L
authors.initials: JL
authors.lastname: Barbur
mesh_terms: D000293:Adolescent; D000328:Adult; D015350:Contrast Sensitivity / Q000187:drug effects; D019587:Dietary Supplements; D005584:Fovea Centralis / Q000187:drug effects; D006801:Humans; D008027:Light; D014975:Lutein / Q000008:administration & dosage*; D008266:Macula Lutea / Q000187:drug effects*; D008297:Male; D010857:Pigment Epithelium of Eye / Q000187:drug effects*; D012542:Scattering, Radiation; D013028:Space Perception / Q000187:drug effects; D014792:Visual Acuity / Q000187:drug effects*; D024341:Xanthophylls / Q000008:administration & dosage*; D065146:Zeaxanthins
chemical_list: D024341:Xanthophylls; D065146:Zeaxanthins; D014975:Lutein