Primary rhegmatogenous retinal detachment: clinical epidemiology and genetic aetiology
Primary rhegmatogenous retinal detachment (RRD) is one of the most common ophthalmic emergencies. RRD is caused by a full thickness break in the retina which initiates separation of the neurosensory retina from the underlying retinal pigment epithelium. The subsequent accumulation of fluid within this potential space extends the area of detachment and causes visual loss. Previous assessments of RRD incidence have demonstrated large differences in case definition and methodology, with incidence estimates varying 3-fold geographically and in different time periods. To date there have been no systematic or prospective incidence estimates of primary RRD in the U.K. In this thesis I present the findings of a 2-year epidemiology study that prospectively aimed to recruit all incident cases of primary RRD diagnosed in Scotland. Case recruitment from consenting participants comprised a detailed questionnaire and a blood sample. In this thesis, I present the findings of the Scottish retinal detachment study that examined the incidence, demographic features, temporal incidence trends, as well as clinical and socio-economic associations of primary RRD in Scotland. From the clinical and genetic resource I assembled, I calculated the first population based estimate of the sibling recurrence risk ratio for RRD and designed and assisted in the analysis of the first case-control genome wide association study of this condition. Results from this study have estimated the annual incidence of primary RRD in Scotland to be 12.05 per 100,000 population. Based on this estimate, there are approximately 7,300 new cases annually in the United Kingdom. RRD incidence increases with age, is more common in men and right eyes, and is strongly associated with socio-economic affluence. In addition, using hospital episode data, the overall age-standardised incidence of RRD in Scotland was shown to be steadily increasing since 1987 with an average annual increase of 1.9%. Analysis of the clinical findings highlighted that the majority of RRD cases are caused by more than one retinal break; an important consideration for appropriate surgical management. Ocular trauma, previous cataract surgery, family history, and retinal degeneration are important predisposing features. In addition, over a 2 year period approximately 7% of individuals will suffer a RRD in the fellow eye representing an important risk of bilateral visual loss. Furthermore, I demonstrate that the risk of having an affected sibling with RRD is increased 2-fold given that one sibling has had the condition, substantiating a genetic component to the pathogenesis of this condition. In the final aspect of this thesis I will present the design and analysis of a two stage case-control genome-wide association study examining the role of common genetic variants and selected candidate genes in predisposing to RRD development.