title: The Tromsø Eye Study: study design, methodology and results on visual acuity and refractive errors.
abstract: OBJECTIVE
  To describe the study design and methodology of the Tromsø Eye Study (TES), and to describe visual acuity and refractive error in the study population.
  
  
  METHODS
  The Tromsø Eye Study is a sub-study of the Tromsø Study, a population-based multipurpose longitudinal study in the municipality of Tromsø, Norway. The Tromsø Eye Study was a part of the sixth survey of the Tromsø Study, conducted from October 2007 through December 2008. The eye examination included information on self-reported eye diseases, assessment of visual acuity and refractive errors, retinal photography and optical coherence tomography. Retinal images were graded for diabetic retinopathy and age-related macular degeneration, and with computer-assisted measurements of arteriolar and venular diameters. In addition, TES researchers have access to the large comprehensive Tromsø Study database including physical examination results, carotid artery ultrasound, electrocardiogram, bone densitometry, cognitive tests, questionnaires, DNA, blood and urine samples and more from the present and the five previous surveys.
  
  
  RESULTS
  Visual acuity was assessed in 6459 subjects and refraction in 6566 subjects aged 38-87 years. Snellen visual acuity <20/60 was found in 1.2% (95% CI 0.95-1.5) of the participants and there was no gender difference. Visual impairment increased with age, and in the age group 80-87 years, the overall visual acuity <20/60 was 7.3% (95% CI 3.3-11.2). Spherical equivalent showed an increasing trend with age and there was no clinically relevant difference between men and women. Retinal photography was performed in 6540 subjects.
  
  
  CONCLUSIONS
  Prevalence of visual impairment was low but increased with age. There was a trend towards hyperopia with age and no clinically relevant difference in refraction between the sexes. TES aims to provide epidemiological research on several eye and eye-related diseases. Owing to a comprehensive data collection, it has the opportunity to explore issues related to environmental factors, cognition and their interaction with diseases in this community.
authors.affiliation: Department of Ophthalmology and Neurosurgery, University Hospital of North Norway, Tromsø, NorwayResearch Group of Epidemiology of Chronic Diseases, Department of Community Medicine, Faculty of Health Sciences, University of Tromsø, Tromsø, NorwayBrain and Circulation Research Group, Department of Clinical Medicine, Faculty of Health Sciences, University of Tromsø, Tromsø, NorwayDepartment of Ophthalmology, Nordland Hospital, Bodø, NorwayDepartment of Neurology and Neurophysiology, University Hospital of North Norway, Tromsø, NorwayNIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital, NHS Foundation Trust, London, UKUCL Institute of Ophthalmology, Head of Reading Centre, London, UKDepartment of Ophthalmology, Odense University Hospital, Odense, Denmark.
authors.forename: Geir
authors.initials: G
authors.lastname: Bertelsen
authors.forename: Maja G
authors.initials: MG
authors.lastname: Erke
authors.forename: Therese
authors.initials: T
authors.lastname: von Hanno
authors.forename: Ellisiv B
authors.initials: EB
authors.lastname: Mathiesen
authors.forename: Tunde
authors.initials: T
authors.lastname: Peto
authors.forename: Anne K
authors.initials: AK
authors.lastname: Sjølie
authors.forename: Inger
authors.initials: I
authors.lastname: Njølstad
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D035843:Biomedical Research / Q000379:methods*; D003930:Diabetic Retinopathy / Q000453:epidemiology; D016021:Epidemiologic Studies; D005260:Female; D005387:Finland / Q000453:epidemiology; D006306:Health Surveys; D006801:Humans; D008137:Longitudinal Studies; D008268:Macular Degeneration / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012030:Refractive Errors / Q000453:epidemiology*; D012107:Research Design; D041623:Tomography, Optical Coherence; D014786:Vision Disorders / Q000453:epidemiology*; D014792:Visual Acuity / Q000502:physiology*; D019987:Persons with Visual Disabilities / Q000706:statistics & numerical data