New test can detect eye disease early

Melbourne: Scientists have developed a new, quick and simple eye test that can predict who is more at risk of age-related macular degeneration (AMD), a leading cause of blindness worldwide.

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.

"Many people as they grow older have little yellow blobs of protein and lipids that build up in the retina, known as drusen," said Professor Ted Maddess of The VC and The Australian National University (ANU).

"While having drusen doesn't always lead to AMD, it can signal an increase in the individual's risk of the eye disease," Maddess said.

Maddess explained 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," he said.

"However, these tests ignore other parts of the retina, which our study now shows can be damaged in early AMD," he added.

Using the TrueField Analyser, a device developed by Maddess's team and 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," Maddess said.

"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 patients," Maddess said.
The study was published in Graefe's Archive for Clinical and Experimental Ophthalmology.