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E. Moore, S. Subbiah, G. J. McKay, G. Silvestri; Geographical Distribution of Genetic Haplotypes in Patients With Stage 4 Exudative Age Related Macular Degeneration (AMD) in the Northern Ireland Population. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2114.
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© ARVO (1962-2015); The Authors (2016-present)
To establish if risk and protective genetic haplotypes for genes associated with AMD show geographic clustering across Northern Ireland.
All fluorescein angiograms carried out in 2001 were reviewed and 161 patients identified with stage 4 exudative AMD. Demographic details were recorded and patient birth location plotted on a map of Northern Ireland. Population demographics were obtained from the Northern Ireland Statistics and Research Agency. The prevalence of stage 4 eAMD was then calculated for each region and adjusted for age. Venous blood samples were collected from 121 patients representing 75% of the study population for the year 2001. Ascertainment of a control population in excess of 500 samples was undertaken to provide an indication of the genetic stratification across the province. Genetic haplotype analysis was undertaken for Complement Factor H (CFH), CFHR1, CFHR3, LOC387715, Complement Factor B (FB), Complement component 2 (C2) and Vascular Endothelial Growth Factor (VEGF). A questionnaire was answered by the affected cohort detailing history of smoking, angiopathic disease, drug history, refractive status, eye colour, body mass index and family history of migration.
Geographical clustering of stage 4 AMD similar to that seen in 2002 and 2003 was confirmed in 2001 with a distinct East-West divide with increased prevalence of AMD in the eastern counties. Preliminary analysis suggests a high incidence of AMD risk haplotypes within the affected cohort with a decreasing incidence of protective haplotypes. Comparisons between the incidence of these haplotypes and the general population is being investigated to ascertain whether genetic stratification across the province is likely to lead to a decreased risk of AMD for those living in the West.
Our results show a statistically significant bias in the incidence of grade 4 eAMD reported across Northern Ireland over 3 successive time periods. Our hypothesis that genetic stratification may support these findings is based on an investigation by Dolan et al. (2005) where genetic stratification across Ireland was proven. Comparison of genetic haplotypes of the risk loci implicated in AMD between the affected cohort and the general population will identify if this is the case in relation to the incidence of AMD. Interestingly there are 25% more sunlight hours in the east compared to the west, this may be a confounding factor and this will be further evaluated.
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