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C.E. Gilbert, M.S. H. Liew, F.J. G. M. van Kuijk, J. Mellerio, J. Marshall, S. Beatty, T.D. Spector, C.J. Hammond; Spatial Profile Distribution of Macular Pigment Is Highly Heritable . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3804.
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© ARVO (1962-2015); The Authors (2016-present)
There is evidence that macular pigment (MP) protects the eye against age–related macular degeneration. The spatial profile of MP varies among individuals and effects volume and peak MP levels. A classical twin study was performed to investigate whether genetic factors influence the spatial profile of MP distribution.
296 healthy twin volunteers (158 monozygotic [MZ], 138 dizygotic [DZ]), aged 16–50 years, were recruited from the TwinsUK registry at St. Thomas’ Hospital. MP was measured using a modified Heidelberg Retinal Angiograph (HRA), which acquires fundus autofluoresence images (AF) using 2 wavelengths (488nm & 514nm). Using AF images, MP density maps and spatial distribution profiles were obtained using Trieschmann’s grading system. The presence of a ‘ring structure’ or central dip in MP levels was also noted. Concordance of a ring structure in MZ twins was compared with concordance in DZ twins.
The MP profile of right and left eyes was highly correlated (r=0.97); MP profiles of right eyes were used in subsequent analyses. Most subjects had a type 1 MP profile (0.92), with 71 MZ twin pairs being concordant for a type 1 profile and 2 being discordant. For DZ twins, 59 were concordant and 10 were discordant for the type 1 profile. The prevalence of type 2 profiles was 0.08 (n=16) (MZ twins 6 concordant/2 discordant; DZ twins 0 concordant/8 discordant). Type 3 (n=1) and 4 (n=1) were rare. The prevalence of a ring structure was 0.31 and the concordance in MZ twins was 0.85 (95% CI 0.75–0.95) compared to 0.43 in DZ twins (95% CI 0.23–0.63), suggesting a genetic role (p for difference<0.001).
The Type 1 MP profile was the commonest spatial distribution pattern. MZ twin pairs showed a significantly higher concordance for the presence of a central dip in MP (i.e. a ring structure on MP density maps) compared to DZ twins, suggesting that genetic factors play an important role in determining the spatial distribution pattern of MP. Future studies will reveal whether the profile pattern influences the accumulation of MP with dietary carotenoid supplementation.
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