A new, quick and simple eye test can predict who is more at risk of age-related macular degeneration (AMD), a leading cause of blindness worldwide.
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Researchers at Australia's Vision Centre (VC) have found that while people with early AMD can still see in fine detail, other parts of their vision may be damaged and this isn't revealed by current eye tests.
The new test, by revealing the damage, can show doctors or optometrists where to look and when to watch a patient more closely, helping them to lessen the risk of the disease and avoid total blindness.
Professor Ted Maddess of The VC and The Australian National University (ANU) explains that AMD occurs when the drusen accumulate and expand, blocking the retina from getting oxygen or from disposing dead eye cell or tissue. This causes patches of the retina to die or leads to abnormal growth of blood vessels in the eye.
"It ends up damaging our central vision, which we use to read, drive and see in fine detail. This is why current tests for AMD focus on the central visual field. However, these tests ignore other parts of the retina, which our study now shows can be damaged in early AMD," said Mr. Maddess.
Using the TrueField Analyzer, a device developed by Mr. Maddess's team and the Australian company Seeing Machines, Vision Centre researchers tested how pupils of early AMD respond to images on LCD screens. The images were provided to each eye at 44 locations in the person's visual field.
Two video cameras using infrared lighting recorded the instantaneous response of the pupils, which was then analysed by a computer.
“All the patients had drusen and most could see in fine detail, which means that their central vision was still working well. However, when we measured other parts of their vision, we found that their pupils responded less compared to people without AMD. This shows that some of the drusen were harming parts of their vision, and the test reveals which patches were causing the damage. While we don't know if damage caused by drusen will always result in AMD, the test can act as a warning sign for doctors and patient.
"For instance, if there's a patch of drusen near the central vision, and if the person's vision is damaged in the same area, it's a sign that they need close attention. Doctors can advise the patient to exercise more, to eat more antioxidants, or to stop habits like smoking that cause eye disease. They can also have the patient come in more frequently for check-ups," says Mr. Maddess.
Mr. Maddess says AMD currently affects one in seven Australians over the age of 50, costs $2.6 billion a year, and will rob the central vision of 1.77 million Australians by 2030. In developed countries about 15 percent of people over 40 show signs of early AMD, with about four percent progressing to late stage AMD each year. ■