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The prevalence and causes of visual impairment in indigenous Australians within central Australia: the Central Australian Ocular Health Study J Landers, T Henderson and J Craig Br J Ophthalmol 2010 94: 1140-1144 originally published online June 7, 2010
doi: 10.1136/bjo.2009.168146
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Global issues
The prevalence and causes of visual impairment in indigenous Australians within central Australia: the Central Australian Ocular Health Study J Landers,1 T Henderson,2 J Craig1 1
Department of Ophthalmology, Flinders Medical Centre, Adelaide, South Australia, Australia 2 Department of Ophthalmology, Alice Springs Hospital, Alice Springs, Northern Territory, Australia Correspondence to Dr John Landers, Flinders Medical Centre, Flinders Drive, Bedford Park, South Australia 5042, Australia;
[email protected] Accepted 13 December 2009 Published Online First 7 June 2010
ABSTRACT Aim To determine the prevalence and causes of visual impairment and blindness among indigenous Australians living in central Australia. Methods 1884 individuals aged 20 years or older, living in one of 30 remote communities within the statistical local area of “Central Australia”, were recruited for this study, from which 1883 were assessable. This equated to 36% of those $20 years old and 67% of those $40 years old within this district. Participants were recruited as they presented to the eye clinic at each remote community. Patients underwent Snellen visual acuity testing and subjective refraction. After this, an assessment of their anterior and posterior segments was made. Rates and causes of bilateral visual impairment (vision worse than Snellen visual acuity 6/12 in the better eye) and bilateral blindness (Snellen visual acuity worse than 6/60 in the better eye) were presented. Results 19.4% (365/1883) had bilateral visual impairment (25.1% of those $40 years old) and 2.8% (53/1883) had bilateral blindness (3.6% of those $40 years old). Refractive error followed by cataract were the main causes for bilateral visual impairment and blindness. Following these, diabetic eye disease and trachomatous corneal opacification were the main causes of bilateral visual impairment and bilateral blindness, respectively. Conclusion This study indicates that bilateral visual impairment and blindness are, respectively, 25.1% and 3.6% among indigenous Australians, four to seven times higher than among the non-indigenous Australian population. Trachoma is the leading cause of bilateral blindness after refractive error and cataract.
Over the past 30 years, numerous population-based studies have defined the burden of ocular morbidity within their population.1e5 They have identified the leading causes of visual impairment, thereby allowing a targeted approach to reduce these levels by allocating services and funding. They have also identified differences between populations throughout the world, demonstrating variations in genetic predisposition, environmental exposures and access to services. For example, worldwide, the most common causes of visual impairment are cataract, trachoma and glaucoma.6 This is in contrast to the developed world in which agerelated macular degeneration, glaucoma and cataract predominate.6 7 To better allocate resources, an accurate knowledge of the prevalence of ocular disorders must be known. The Central Australian Ocular Health Study was designed to enumerate the levels of 1140
ocular morbidity among indigenous Australians living in remote communities within the central Australian statistical local area. In the 1970s, the National Trachoma and Eye Health Program (NTEHP)8 surveyed 49% of the indigenous population across Australia looking primarily at vision, refractive error, trachoma and other causes of visual impairment. However, since then, there has been no comprehensive populationbased assessment of ocular health among indigenous Australians assessing multiple ocular morbidities within the same population. This study was designed to determine the prevalence and causes of visual impairment and blindness among indigenous Australians living in central Australia.
METHODS The Central Australian Ocular Health Study took place in very remote communities within the statistical local area of “Central Australia”, excluding those living in and around the city of Alice Springs. The area encompassed 548 400 km2 and included a target population of 5173 persons $20 years old (ie, adults) living throughout this region (figure 1).9e13 Clinics were held at 30 of the largest communities a total of once or twice per year depending on the population of the community. Given the length of time between each of these clinics, the health workers in the communities would actively encourage every resident to attend the clinics regardless of their symptoms. Patients were recruited from those who identified themselves as indigenous Australians, presenting to the remote clinics at each of these communities during the 36-month period between July 2005 and June 2008. Ethical approval from the Central Australian Human Research Ethics Committee was obtained and conformed to the tenets of the Declaration of Helsinki. The aims of the study were explained, with an interpreter whenever necessary, and written informed consent was obtained. Data were entered on a standardised form, which had been constructed before the commencement of the study. This was to ensure completeness and consistency in the data collection. All data collection was performed under the supervision of one of two consultant ophthalmologists. A predetermined protocol was followed for each patient, which set out the sequence of data collection and the parameters to be assessed for each part of the eye. Presenting visual acuity was determined using a tumbling E acuity chart at 3 m in a well-lit room. If the patient could not read the top letter (6/120 Br J Ophthalmol 2010;94:1140e1144. doi:10.1136/bjo.2009.168146
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Global issues disorder (glaucoma) at an expected prevalence of 0.4%.8 Glaucoma was considered to be present if category 2 criteria20 were fulfilled (cup/disc ratio or cup/disc ratio asymmetry $99.5th percentile (ie, $0.8)18 in the absence of any other explanation) or if category 3 criteria20 were fulfilled (visual acuity 99.5th percentile, or visual acuity
