Thursday 30 October, 2014

Scientists devise easier test for blindness

Published On: Tue, Oct 9th, 2012 | Eye Diseases | By BioNews

Scientists have demonstrated a quick, accurate test for one of the world’s leading causes of blindness, age-related macular degeneration (AMD).

The condition can be just as effectively, more rapidly and cheaply diagnosed under bright lights, instead of making patients sit for 20 minutes in a darkened room.

“AMD accounts for half of the legal blindness cases in Australia,” says Ted Maddess, professor from The Vision Centre and The Australian National University. “It affects one in seven people over the age of 50, costing the nation. Globally, it affects 25 to 30 million people.”

“While current tests for AMD are done in the light, scientists have proposed that it might be better if the patient has their vision adapted to the dark prior to the test,” the journal Vision Research quotes him as saying.

“This is because they had found that rod receptors – vision cells that we use to see in black and white and in low light – die earlier in AMD than the cone receptors we use to see in colour during the day. So it had been suggested that AMD tests would be more accurate if they were based on the health of a person’s rods,” adds Maddes.

Using the TrueField Analyzer, a device developed by Maddess’ team and the Australian company Seeing Machines, the researchers tested how pupils respond to images on LCD screens, according to a Vision Centre statement.

“The response of the pupils is a good indicator of how well the eyes are working – healthy eyes, being more sensitive to stimuli, will produce larger pupil contractions than damaged eyes,” Maddess says.

“We found little to no difference in the results – with the TrueField Analyzer, we could diagnose AMD just as well regardless of how much light the eyes were exposed to during the test.

“This means that the cones of an AMD patient are about as damaged as the rods, so tests that are based on a person’s cone vision are just as accurate,” concludes Maddes.

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