The Prevalence and Causes of Vision Impairment and Blindness in Australia: the National Eye Health Survey
Total Page:16
File Type:pdf, Size:1020Kb
The prevalence and causes of vision impairment and blindness in Australia: The National Eye Health Survey Joshua Ross Foreman ORCID ID: https://orcid.org/0000-0002-3685-4054 Submitted in total fulfilment of the requirements of the degree of Doctor of Philosophy February 2018 Centre for Eye Research Australia Department of Ophthalmology Faculty of Medicine, Dentistry and Health Sciences The University of Melbourne 1 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 2 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 3 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. 4 DECLARATION This is to certify that i. the thesis comprises only my original work towards the PhD except where indicated in the preface, ii. due acknowledgement has been made in the text to all other material used, and iii. the thesis is less than 100,000 words in length, exclusive of tables, maps, bibliographies and appendices. Joshua Foreman Centre for Eye Research Australia Department of Ophthalmology University of Melbourne February 2018 5 PREFACE In accordance with University of Melbourne policy, I acknowledge that certain aspects of this work were collaborative. My primary PhD supervisor, Mohamed Dirani, was the Principal Investigator of this study and successfully obtained funding (in collaboration with Vision 2020 Australia), ethical approval from the Human Research Ethics Committee of the Victorian Eye and Ear Hospital and endorsement from the National Aboriginal Community Controlled Health Organisation. He was also involved in the initial conception of this survey, along with Hugh Taylor and Peter van Wijngaarden. I worked with Mohamed Dirani and Stuart Keel to obtain ethical approval from Aboriginal ethical bodies and a coordinated approach involving Mohamed Dirani, Stuart Keel, Larissa Andersen and myself, was employed to facilitate engagement with Indigenous communities. Ross Dunn assisted with the participant sampling and site selection protocol outlined in Chapter 3. Stuart Keel, Pei Ying Lee, Alison Schokman, Larissa Andersen, John Komser, Cayley Bush, Benny Phanthakesone, Hiba Wehbe, Rosamond Gilden and Celestina Pham assisted with logistics and the examination of study participants. Peter van Wijngaarden designed the clinical referral protocol. A total of 27 manuscripts relating to this work have been submitted to journals, of which 25 have been accepted or published and 2 have been provisionally accepted. I am first author on 13, joint first author on one, second author on three and third author on 10 of these manuscripts. This thesis includes ten papers on which I am first author and one on which I am joint first author. The full citation for each included paper is presented below in the order of presentation in this thesis, after which the relative contributions of authors are provided. 6 1. Foreman J, Keel S, Dunn R, van Wijngaarden P, Taylor HR, Dirani M. Sampling methodology and site selection in the National Eye Health Survey: an Australian population-based prevalence study. Clin Exp Ophthalmol. 2017;45(4):336-47. 2. Foreman J, Xie J, Keel S, van Wijngaarden P, Taylor HR, Dirani M. The validity of self- report of eye diseases in participants with vision loss in the National Eye Health Survey. Sci Rep. 2017;7(1):8757. 3. Foreman J, Keel S, van Wijngaarden P, Taylor HR, Dirani M. Recruitment and Testing Protocol in the National Eye Health Survey: A Population-Based Eye Study in Australia. Ophthalmic Epidemiol. 2017: 24(6):353-363. 4. Foreman J, Xie J, Keel S, van Wijngaarden P, Sandhu SS, Ang GS, Fan Gaskin J, Crowston J, Bourne R, Taylor HR, Dirani M. The Prevalence and Causes of Vision Loss in Indigenous and Non-Indigenous Australians: The National Eye Health Survey. Ophthalmology. 2017: 24(12):1743-1752. 5. Foreman J, Xie J, Keel S, Ang GS, Lee PY, Bourne R, Crowston J, Taylor HR, Dirani M. The prevalence and causes of unilateral vision impairment and unilateral blindness in Australia: The National Eye Health Survey. JAMA Ophthalmol. 2018. 6. Keel S*, Foreman J*, Xie J, Taylor HR, Dirani M. Prevalence and associations of presenting near vision impairment in the Australian National Eye Health Survey. Eye. 2018. 7. Foreman J, Xie J, Keel S, Taylor HR, Dirani M. Utilization of eye health-care services in Australia: the National Eye Health Survey. Clin Exp Ophthalmol. 2017. 8. Foreman J, Keel S, Xie J, Van Wijngaarden P, Taylor HR, Dirani M. Adherence to diabetic eye examination guidelines in Australia: the National Eye Health Survey. Med J Aust. 2017;206(9):402-6. 9. Foreman J, Xie J, van Wijngaarden P, Crowston J, Taylor HR, Dirani M. Cataract surgery coverage rates for Indigenous and non-Indigenous Australians: the National Eye Health Survey. Med J Aust. 2017;207(6):256-261. 10. Foreman J, Xie J, Keel S, Taylor HR, Dirani M. Treatment coverage rates for refractive error in the National Eye Health survey. PLoS One. 2017;12(4):e0175353. 11. Foreman J, Dirani M, Taylor H. Refractive error, through the lens of the patient. Clin Exp Ophthalmol. 2017;45:673.674. I conducted the literature review, designed the analysis, interpreted results, authored the first draft, and implemented all author and reviewer feedback for all publications included in this thesis. All authors provided significant intellectual contributions and reviewed all iterations of the manuscripts on which they are listed as authors. Jing Xie contributed to the statistical analysis of each paper on which she is listed as an author. Mohamed Dirani was the Principal 7 Investigator and senior author on all manuscripts in this list and supervised all aspects of this study. Publications 1, 2 and 3 are included in the Methods section of this thesis. Prior to the commencement of data collection, I spent six months refining all aspects of the methodology with my supervisors, Mohamed Dirani, Peter van Wijngaarden and Stuart Keel, including study design, logistics, questionnaire and examination procedures, as well as electronic database contruction.