title: Prevalence of chronic ocular diseases in a genetic isolate: the Norfolk Island Eye Study (NIES).
abstract: OBJECTIVE
  Over 40% of the permanent population of Norfolk Island possesses a unique genetic admixture dating to Pitcairn Island in the late 18(th) century, with descendents having varying degrees of combined Polynesian and European ancestry. We conducted a population-based study to determine the prevalence and causes of blindness and low vision on Norfolk Island.
  
  
  METHODS
  All permanent residents of Norfolk Island aged ≥ 15 years were invited to participate. Participants completed a structured questionnaire/interview and underwent a comprehensive ophthalmic examination including slit-lamp biomicroscopy.
  
  
  RESULTS
  We recruited 781 people aged ≥ 15, equal to 62% of the permanent population, 44% of whom could trace their ancestry to Pitcairn Island. No one was bilaterally blind. Prevalence of unilateral blindness (visual acuity [VA] < 6/60) in those aged ≥ 40 was 1.5%. Blindness was more common in females (P=0.049) and less common in people with Pitcairn Island ancestry (P<0.001). The most common causes of unilateral blindness were age-related macular degeneration (AMD), amblyopia, and glaucoma. Five people had low vision (Best-Corrected VA < 6/18 in better eye), with 4 (80%) due to AMD. People with Pitcairn Island ancestry had a lower prevalence of AMD (P<0.001) but a similar prevalence of glaucoma to those without Pitcairn Island ancestry.
  
  
  CONCLUSIONS
  The prevalence of blindness and visual impairment in this isolated Australian territory is low, especially amongst those with Pitcairn Island ancestry. AMD was the most common cause of unilateral blindness and low vision. The distribution of chronic ocular diseases on Norfolk Island is similar to mainland Australian estimates.
authors.affiliation: Centre for Eye Research Australia, University of Melbourne, Department of Ophthalmology, Royal Victorian Eye and Ear Hospital, Victoria, Australia.
authors.forename: Justin C
authors.initials: JC
authors.lastname: Sherwin
authors.forename: Lisa S
authors.initials: LS
authors.lastname: Kearns
authors.forename: Alex W
authors.initials: AW
authors.lastname: Hewitt
authors.forename: Yaling
authors.initials: Y
authors.lastname: Ma
authors.forename: John
authors.initials: J
authors.lastname: Kelly
authors.forename: Lyn R
authors.initials: LR
authors.lastname: Griffiths
authors.forename: David A
authors.initials: DA
authors.lastname: Mackey
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D001766:Blindness / Q000453:epidemiology* / Q000235:genetics; D015785:Eye Diseases, Hereditary / Q000453:epidemiology* / Q000235:genetics; D005260:Female; D007839:Functional Laterality; D005828:Genetics, Population / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008542:Melanesia / Q000453:epidemiology; D008875:Middle Aged; D015995:Prevalence; D017678:Sex Distribution; D011795:Surveys and Questionnaires; D015354:Vision, Low / Q000453:epidemiology* / Q000235:genetics; D014792:Visual Acuity; D019987:Persons with Visual Disabilities / Q000706:statistics & numerical data; D055815:Young Adult