title: The Association between Foveal Morphology and Macular Pigment Spatial Distribution: An Ethnicity Study.
abstract: OBJECTIVE
  Macular pigment (MP) spatial distribution varies considerably among individuals. We investigated ethnic variations in MP spatial distribution in relation to foveal architecture.
  
  
  METHODS
  We measured MP optical density (MPOD) using heterochromatic flicker photometry (MAP test, City, University of London) in 76 white, 80 South Asian and 70 black volunteers (18 to 39 years). MPOD spatial profiles were classified objectively as exponential, ring-like or central dip, based on deviations away from an exponential fit. Measurements including total retinal thickness (RT), inner retinal layer (IRL), inner and outer plexiform layer (IPL and OPL) thickness, foveal width and foveal pit slope were taken from Spectralis SD-OCT (Heidelberg, Germany) scans.
  
  
  RESULTS
  Integrated MPOD up to 1.8° (MPODint) was higher in South Asian (0.84±0.26) and black (0.84±0.31) than whites (0.63±0.24, P<0.0005). Ethnicity explained around 10% of the variance while gender played no significant role. MPOD profile phenotypes were associated with ethnicity: 58% with ring profiles were South Asian and 43% with dip profiles were black (χ2(4,226) = 13.4, P = 0.009). MPODint was lower in exponential (0.66±0.21) compared to ring-like (0.96±0.26) and central dip (1.00±0.32, P<0.0005) groups. White subjects had thicker IRL at 0° (130±21μm) than South Asian (123±16μm) and blacks (116±14μm; F(2) = 12.4, P<0.0005), with comparable results for IPL (P<0.0005) and OPL (P = 0.03). There was no significant difference in IRL, IPL or OPL (from 0 to 3.8° retinal eccentricity) or foveal width between MP profile groups (P>0.05).
  
  
  CONCLUSIONS
  We report a significant difference in the amount and distribution of MP between ethnicities that is not explained by variations in foveal morphology.
authors.affiliation: Applied Vision Research Centre, The Henry Wellcome Laboratories for Vision Sciences, City, University of London, London, United Kingdom.
authors.forename: Irene
authors.initials: I
authors.lastname: Ctori
authors.affiliation: Applied Vision Research Centre, The Henry Wellcome Laboratories for Vision Sciences, City, University of London, London, United Kingdom.
authors.forename: Byki
authors.identifier: http://orcid.org/0000-0002-4864-0723
authors.initials: B
authors.lastname: Huntjens
mesh_terms: D005006:Ethnicity; D005260:Female; D005584:Fovea Centralis / Q000033:anatomy & histology*; D006801:Humans; D065348:Macular Pigment; D008297:Male; D010641:Phenotype; D010783:Photometry
chemical_list: D065348:Macular Pigment