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M.D. Chamberlain, P.N. Baird, J.L. Hopper, R.H. Guymer; Heritability of Clinical Features of Age–Related Macular Degeneration – A Twin Study . Invest. Ophthalmol. Vis. Sci. 2005;46(13):217.
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Purpose: Age–related macular degeneration is the commonest cause of severe visual impairment in the Western world. Previous twin studies have suggested significant genetic influence in AMD, and increasing interest has developed as to whether certain clinical sub–phenotypic features are more strongly inherited than others. Elucidation of strongly heritable sub–phenotypes may allow more effective gene–searching strategies in AMD in the future. Methods: Three hundred and ten (310) twin pairs, 182 MZ pairs and 128 DZ pairs, were recruited from the NHMRC–funded Australian Twin Registry and local advertising. The mean age of participants was 65.2 years, with 68.1% of participants being female and 31.9% male. Participants underwent dilated fundus photography, and two independent observers examined digitised photographic images. Photographs were graded using the Wisconsin grading system. Results: The prevalence of early AMD was 19.5% in the 169 twin pairs graded to date. The case–wise concordance for AMD was 0.59 in MZ twins and 0.31 in DZ twins in this initial cohort, implying a significant role for genes in AMD pathogenesis. Concordance of sub–phenotypic features such as intermediate drusen, soft drusen, pigmentary changes and ≥20 hard drusen were significantly greater in MZ than DZ twins (MZ/DZ risk ratio=1.68, 2.30, 1.93 and 1.49 respectively). This effect was not seen in scattered (<20) hard drusen (MZ/DZ risk ratio=0.94). Conclusions: These findings further confirm a significant genetic influence in AMD. Grading of the remaining cohort will allow a more powerful examination of the heritability of the clinical AMD sub–phenotypes.
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