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The lens of the eye is normally clear. Light passes through the lens to the light sensitive tissues at the back of the retina, to form an image. A cataract forms when proteins in the lens become damaged. When a cataract develops, the lens becomes cloudy and prevents light from reaching the retina, resulting in blurred vision. In its early stages, a cataract may cause a lessening of vision but eventually it can cause blindness if left untreated. Cataracts usually develop slowly and at different rates in each eye.
Most cataracts are due to ageing. By the age of 80 years, it is common for people to develop or form some cataract. Other risk factors include:
Symptoms of cataract can include:
Cataract is detected through a comprehensive eye exam that can include a visual acuity test, dilated eye exam and tonometry. A visual acuity test is an eye chart test which measures how well a person sees at various distances. A dilated eye exam and tonometry need to be carried out by an eye care professional. In a dilated eye exam drops are placed in the eyes to widen, or dilate the pupils and a special magnifying lens is used to examine lens to check for cataract, and the retina and optic nerve for other eye problems. After the exam, close-up vision may remain blurred for several hours. Tonometry is a procedure using a tonometer to measure the pressure inside the eye. Numbing drops may be applied to the eye for this test.
The early symptoms of cataract may be improved with new eye glasses; however, the usual treatment for cataract is surgery. Cataract surgery involves removing the cloudy tissue from the internal part of the lens, and leaving part of the lens capsule behind to act as a support for an implant called an intraocular lens. In most cases only a local anaesthetic (numbing) is needed and the person can go home the same day. Cataract surgery can quickly restore vision and is considered very cost effective.
A national eye survey in 2008 found that cataract was the second-leading cause of low vision for Indigenous Australians. Cataract was the cause of 27% of low vision and 32% of blindness among Indigenous adults, with vision loss from cataract being more common in very remote areas. Only 65% of those with vision loss from cataract had received surgery. Blindness from cataract was 12 time higher for Indigenous adults compared with other Australians. Some of the main issues affecting cataract treatment for Indigenous people, especially in remote areas are:
Fred Hollows Foundation (2012) Cataract. Sydney: Fred Hollows Foundation http://www.hollows.org.au/eye-health/cataract
Cataract (2008) Centre for Eye Research Australia
Taylor HR, National Indigenous Eye Health Survey Team (2009) National Indigenous eye health survey: minum barreng (tracking eyes): full report. Melbourne: Indigenous Eye Health Unit, The University of Melbourne
Taylor HR, Boudville A, Anjou M, McNeil R (2013) The roadmap to close the gap for vision: January 2013 summary report. Melbourne: Indigenous Eye Health Unit, the University of Melbourne
Anjou MD, Boudville AI, Taylor HR (2013) Nationally consistent spectacle supply for Indigenous Australians.Australian and New Zealand Journal of Public Health; 37(1): 94-95
Boudville AI, Anjou MD, Taylor HR (2013) Indigenous access to cataract surgery: an assessment of the barriers and solutions within the Australian health system. Clinical & Experimental Ophthalmology; 41(2): 148–154
© Australian Indigenous HealthInfoNet 2013
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