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J. J. O'Neill, G. J. McKay, D. A. Simpson, G. Silvestri; The Epidemiology of Retinitis Pigmentosa in Northern Ireland. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3724.
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© ARVO (1962-2015); The Authors (2016-present)
The aims of this study are to determine the prevalence of Retinitis Pigmentosa (RP) in Northern Ireland, which has a relatively small and stable population, and secondly to determine phenotypic-genotypic correlations.
All available databases of patients diagnosed with RP dating back over the past twenty years were interrogated. Advertisements about the study were placed in key locations throughout NI. Prevalence figures were calculated based on the most recent census results published in 2006 stating the population of Northern Ireland to be 1,710,300. Participants had venous blood drawn for DNA and a subset of patients were comprehensively phenotyped using LogMar distance acuity charts and Farnsworth D15 for colour blindness. Visual fields were also tested using Humphreys 24-2. and the fundus was imaged using the Topcon TRC 50EX. Genotyping was conducted using linkage exclusion and direct sequencing.
A total of 475 patients were identified as having RP. A prevalence of 1:3996 was calculated after elimination of the deceased and those people no longer residing in NI. The mean age of the study population was 50.4 (SD 21.7), 52% were female and 48% male. 21% had autosomal dominant inheritance, 20% autosomal recessive, 12% X-linked and 47% had no family history (sporadic). Mutations identified to date involve Rho, USH, and RPGR genes. With specific reference to two rhodopsin mutations R145W and Y168C identified in ADRP families, variations in disease phenotype were observed from slight pigmentary changes and white dots to extensive retinal pigment epithelium (RPE) atrophy depending on stage of disease. Visual fields demonstrated an increase in the degree of loss with increasing age, ranging from <5 to 30 degrees of field loss and early onset of nyctalopia leading to some peripheral loss before twenty years of age.
The epidemiology of RP in NI is very similar to that reported elsewhere. Compilation of a Northern Ireland Retinitis Pigmentosa Database will facilitate future characterisation and treatment of RP within this population. In particular, genetic counselling will be improved and more information will be available for patients about their disease and its prognosis.
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