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Optical physicists Doctors Kodikullam and Chitralekha Avudainayagam from the University of New South Wales report their findings in the July issue of the journal Optics Letters.
People with astigmatism have eye lenses that do not focus symmetrically, which Dr Kodikullam Avudainayagam says makes much of the world look smudged.
In the most common form of the condition, the vertical and horizontal lines of a cross are in focus at two different distances.
About 10 per cent of the population have a degree of astigmatism that requires correction, says Dr Avudainayagam, adding it can be very hard to correct if not caught at an early age.
He says the current gold standard of diagnosing it involves patients trialing different lenses until they can see a test image 6 metres away completely clearly.
This can be slow and cumbersome, and people have to remember how things look with each lens as they compare them.
Sunburst image
Optometrists commonly use a sunburst - lines radiating out from a central point - as the test image to diagnose astigmatism.
Instead, Dr Avudainayagam and partner have used a hologram that portrays a range of sunburst images in 3D simultaneously, to replace the need to trial different correcting lenses.
Each sunburst image emulates a different focal length of a correcting lens.
"It's the equivalent of looking through different lenses simultaneously," Dr Avudainayagam said.
Current eye tests for astigmatism involve showing patients numerous lenses, which can be slow and confusing.
The hologram method offers patients different views at the same time.
A person with common astigmatism will see the vertical rays of the sunburst as clearest at one distance and the horizontal rays of the sunburst clearest at another.
At a middle distance all rays appear equally blurry.
By asking the patient to describe what they see, an optometrist would be able to diagnose the exact nature of the astigmatism, says Dr Avudainayagam.
He says comparing the equivalent of different lenses simultaneously will make it much easier for a patient to give accurate feedback to their optometrist.
The different sunbursts in the hologram are labelled to allow a patient to communicate which sunbursts they are describing.
This particular research was carried out using a camera with an astigmatic lens focused at different distances to simulate the vision of a person with astigmatism.
But Dr Avudainayagam says the hologram method has already been tested on real eyes in another experiment involving a different focusing problem.
The second paper will be published in the Journal of the Optical Society of America.
Dr Avudainayagam says the new test for astigmatism must be trialed on astigmatism in young people, which researchers do not know much about. © 2007 Australian Broadcasting Corporation
Posted July 10th, 2007 by Dinka
