The prevalence and causes of vision impairment and blindness in Australia: the National Eye Health Survey

Abstract

Vision impairment (VI) and blindness affect 440 million people worldwide. As most cases can be avoided through evidence-based eye health care interventions, the elimination of avoidable VI and blindness is a global health priority. Nationally-representative population surveys on the prevalence and causes of VI and blindness are required to inform targeted eye health care programs.

This thesis documents Australia’s first National Eye Health Survey (NEHS) that aimed to determine the prevalence and causes of vision loss and rates of utilisation of eye health care services for non-Indigenous Australians aged 50 years or older and Indigenous Australians aged 40 years or older residing in all levels of geographic remoteness in Australia.

Multistage random-cluster sampling was used to select a nationally-representative sample of 3098 non-Indigenous Australians and 1738 Indigenous Australians from 30 population clusters across all five geographic remoteness strata (Major Cities, Inner Regional, Outer Regional, Remote and Very Remote). Participants underwent an interviewer-administered questionnaire and a series of standardised eye examinations, including visual acuity assessment, anterior segment assessment, perimetry, fundus photography and intraocular pressure measurement.

The prevalence of bilateral vision loss was 6.5% (95% confidence interval [CI]: 5.4-7.8) in non-Indigenous Australians and 11.2% (95% CI: 9.5-13.1) in Indigenous Australians. The age- and sex-adjusted prevalence of bilateral vision loss was 2.8 times higher in Indigenous than non-Indigenous Australians (P<0.001). The prevalence of unilateral vision loss amongst non-Indigenous and Indigenous Australians was 16.0% (95% CI: 14.4-17.7) and 14.9% (95% CI: 13.1-16.8), respectively, but after adjustment, unilateral vision loss was 1.4 times more prevalent in Indigenous Australians (P=0.003). Geographic remoteness was associated with a higher prevalence of bilateral (Outer Regional odds ratio [OR]: 2.02) and unilateral (Very Remote OR: 1.65) vision loss in Indigenous Australians, but not non-Indigenous Australians.

Uncorrected refractive error and cataract were the leading causes of bilateral and unilateral vision loss, accounting for 70.4%-80.9% of all cases. Age-related macular degeneration was the leading cause of bilateral blindness (71.4%) and the third leading cause of bilateral vision loss (10.3%) in non-Indigenous Australians. Cataract was the leading cause of bilateral blindness (40%), and diabetic retinopathy was the second leading cause of bilateral blindness (20%) in Indigenous Australians.

Eighty-two percent of non-Indigenous Australians had undergone an eye examination within the past two years. Forty-seven percent of Indigenous Australians had been examined within the past year, as per national recommendations. Fewer Indigenous than non-Indigenous Australians with diabetes adhered to diabetic eye examination guidelines (52.7% [95% CI: 45.9-59.6] v 77.5% [95% CI: 71.8-83.3], OR: 0.37). Cataract surgery coverage (58.5% [95% CI: 49.8-66.8] v 88.0% [95% CI: 84.5-90.6]) and refractive error treatment coverage rates (82.2% [95% CI: 78.6-85.3] v 93.5% [95% CI: 92.0-94.8) were significantly lower in Indigenous Australians compared to non-Indigenous Australians (OR: 32 and 0.51, respectively).

The NEHS has provided nationally-representative data on the prevalence and causes of vision loss and the utilisation of eye health care services for non-Indigenous and Indigenous Australians. This study has shown that the non-Indigenous population of Australia has a lower prevalence of vision loss than other high-income countries, and that there is a significant excess burden of vision loss in the Indigenous population of Australia. Most vision loss in Australia is avoidable and can be eliminated by utilising the findings of this survey to optimise treatment rates of avoidable causes of vision loss. Improvements in the availability and uptake of eye health care services in Indigenous communities, particularly in non-metropolitan areas, are required to close the gap in Indigenous eye health. Marginalised and under-served Indigenous populations in other countries may benefit from the execution of similarly stratified nationwide surveys, the results of which may be used to optimise blindness prevention programs for at-risk population groups.