Prevalence of Chronic Ocular Diseases in a Genetic Isolate: The Norfolk Island Eye Study (NIES)

Abstract

Purpose: 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.

KEYWORDS::

• Blindness
• Epidemiology
• Genetics
• Glaucoma
• Macular degeneration
• Norfolk Island
• Pitcairn Island
• Population isolates

ACKNOWLEDGMENTS

We thank the Norfolk Islanders for welcoming us into their community and for their participation and assistance in this study. Financial support was provided by the RVEEH research committee and the Peggy and Leslie Cranbourne Foundation, DAM is a recipient of the Pfizer Australia Senior Research Fellowship. We would like to thank Byoung-Sun Chu, Robert MacMillan, Julie Barbour and Colleen Wilkinson for helping examine the Norfolk Islanders. CERA receives Operational Infrastructure Support from the Victorian Government.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.