title: The Nakuru eye disease cohort study: methodology & rationale.
abstract: BACKGROUND
  No longitudinal data from population-based studies of eye disease in sub-Saharan-Africa are available. A population-based survey was undertaken in 2007/08 to estimate the prevalence and determinants of blindness and low vision in Nakuru district, Kenya. This survey formed the baseline to a six-year prospective cohort study to estimate the incidence and progression of eye disease in this population.
  
  
  METHODS
  A nationally representative sample of persons aged 50 years and above were selected between January 2007 and November 2008 through probability proportionate to size sampling of clusters, with sampling of individuals within clusters through compact segment sampling. Selected participants underwent detailed ophthalmic examinations which included: visual acuity, autorefraction, visual fields, slit lamp assessment of the anterior and posterior segments, lens grading and fundus photography. In addition, anthropometric measures were taken and risk factors were assessed through structured interviews. Six years later (2013/2014) all subjects were invited for follow-up assessment, repeating the baseline examination methodology.
  
  
  CONCLUSIONS
  The methodology will provide estimates of the progression of eye diseases and incidence of blindness, visual impairment, and eye diseases in an adult Kenyan population.
authors.affiliation: International Centre for Eye Health, Department of Clinical Research, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine (LSHTM), Keppel Street, London WC1E 7HT, UK. Andrew.bastawrous@lshtm.ac.uk.
authors.forename: Andrew
authors.initials: A
authors.lastname: Bastawrous
authors.forename: Wanjiku
authors.initials: W
authors.lastname: Mathenge
authors.forename: Tunde
authors.initials: T
authors.lastname: Peto
authors.forename: Helen A
authors.initials: HA
authors.lastname: Weiss
authors.forename: Hillary
authors.initials: H
authors.lastname: Rono
authors.forename: Allen
authors.initials: A
authors.lastname: Foster
authors.forename: Matthew
authors.initials: M
authors.lastname: Burton
authors.forename: Hannah
authors.initials: H
authors.lastname: Kuper
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D003430:Cross-Sectional Studies; D003941:Diagnostic Techniques, Ophthalmological; D005128:Eye Diseases / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology; D005260:Female; D006306:Health Surveys / Q000379:methods*; D006801:Humans; D007630:Kenya / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011446:Prospective Studies; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D014792:Visual Acuity