After and before: These diagrams show what happens to the shape of a myopic cornea after orthoK treatment. The dark blue area in the diagram at the top shows a cornea that has been treated to make it flatter, which means light is refracted less. This alteration in the refraction corrects the error of a myopic eye (at the bottom), allowing the image to focus correctly on the retina.

Credit: UNSW

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SYDNEY: Australian researchers are testing a new method to stop the progression of short-sightedness with special contact lenses that alter the shape of the eye.

Short-sightedness or 'myopia' affects 25 per cent of Australian adults and there is currently no preventative treatment.

Optometrist and research scientist Helen Swarbrick, of the University of New South Wales, in Sydney, is now leading a world-first study, where children will wear rigid contact lenses that reshape their eyes – a technique known as orthokeratology (orthoK).

Elongation of the eyeball

A relatively small number of Australian adults already use orthoK. But only as temporary fix, and it is not currently used as a preventative method. "Research is needed to confirm whether this is an effective way of controlling myopia [in children]," said Swarbrick who believes orthoK use has been held back by a lack of detailed study.

Myopia sufferers see nearby objects clearly but distant objects appear blurred. The condition is usually identified in young children and worsens as the child grows. The poor vision stems from faulty growth in the eye that leads to elongation of the eyeball and steepening of the cornea. If the cornea is too steep, light entering the eye is refracted to point in front of the retina, as opposed to directly onto the retina.

OrthoK presents one way for adults to manage the problem without surgery. Patients wear rigid contact lens at night while sleeping and then remove them during the daytime. The lenses work by squashing the cornea, reducing its steepness, and thereby relieving the symptoms of myopia.

The reshaping is temporary, however – so contact lenses must be worn every night – but it is hoped that the treatment might have a preventative effect in children.

Promising treatment

Pauline Cho, a physician specialising in contact lenses at the Hong Kong Polytechnic University, led a study in 2005 which indicated orthoK use in children not only reshaped the cornea but also actually slowed the elongation of the eyeball.

Cho's work was based on historic data, but Swarbick's team will now recruit 75 Australian children to participate in a controlled study that should provide a clear answer as to the effectiveness of the technique as a preventative. The initiative was announced at a press conference in Sydney on Tuesday.

Gavin Bonham, the President of the Orthokeratology Society of Oceania, has been prescribing orthoK treatment for the last ten years. "Australia is a world leader in orthokeratology," says Bonham, who added that there could be a huge surge of interest in the technology if the new study finds it effective in slowing or stopping the progression of myopia.

People who are long-sighted (hyperopic) have corneas that are too flat, which is the opposite problem to myopia and causes nearby objects to appear blurred. OrthoK has been found to be less successful as a method to treat long-sightedness, but Swarbrick's team are looking into that too.