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Irene Ctori, Byki Huntjens; Do ethnic variations in foveal morphology explain variations in macular pigment spatial density distribution?. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3620.
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© ARVO (1962-2015); The Authors (2016-present)
Macular pigment (MP) spatial density distribution may vary with ethnicity. Variations in central retinal thickness with ethnicity have also been reported. We investigated ethnic variations in MP spatial distribution in relation to foveal thickness profiles.
We measured MP optical density (MPOD) using heterochromatic flicker photometry (MAP test, City University London) in 76 white, 80 South Asian and 70 black volunteers (males and females,18 to 39 years; all UK residents). Exclusion criteria included ocular pathology, visual acuity worse than 0.3 logMAR and current/previous user of MP supplements. MPOD spatial profiles were classified objectively as exponential, ring-like or central dip, based on deviations away from an exponential fit to the data taking into account instrument measurement error. Inner retinal thickness (IRT) and inner and outer plexiform layer (IPL and OPL) thickness measurements were taken from Spectralis (Heidelberg, Germany) OCT scans at retinal eccentricities corresponding to MPOD measurement locations. We performed between-groups analysis of variance to analyze differences between groups and Pearson Chi-squared test to explore relationships between MP profile type and ethnic grouping.
Integrated MPOD up to 1.8° (MPOD INT) 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 and gender played no significant role. Within each ethnic group, MPOD INT did not vary between subjects born and raised abroad vs. the UK, neither did it vary according to eye colour or smoking status (p>0.05). 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). There was a statistically significant difference in MPOD INT between exponential (0.66±0.21), ring-like (0.96±0.26) and central dip (1.00±0.32, p<0.0005) groups. White subjects had thicker IRT 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 IRT, IPL or OPL (0 to 3.8°) between MP profile groups (p>0.05).
We report a significant difference in the amount and distribution of MP between ethnicities that is not explained by variations in central retinal thickness.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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