Apr 13 2004
UNSW researchers have found the first scientific evidence that special orthokeratology (OK) contact lenses worn only while you sleep may be able to correct long-sightedness;
- UNSW researchers have found the first scientific evidence that special orthokeratology (OK) contact lenses worn only while you sleep may be able to correct long-sightedness;
- The pilot study holds future promise of a safe, simple and reversible treatment for the many people with this vision problem (when you can see distant objects clearly but close objects are blurry). In Australia, moderate long-sightedness affects 8% to 10% of the population.
- The finding builds on the team’s earlier studies into the often dramatic and rapid improvements achieved with OK lens therapy for myopia - or short-sightedness. Many myopic people have been able literally to throw away their glasses.
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A traditional Chinese remedy for short-sightedness reportedly was to sleep with small sandbags on the eyes.
Australia now plays a leading role in a myopia therapy that uses special orthokeratology (known as OK or ortho-K) contact lenses that are worn during sleep and removed during waking hours.
The rigid polymer lenses are flattened in the centre so that they gently press on the soft surface of the cornea to reshape it and correct its focal length.
Vision begins to change within as little as 10 minutes and many myopic people can see normally - without the need for spectacles -after only a week of wearing OK lenses at night. Some then need only use the lenses every two or three nights to maintain normal vision. Others with a greater degree of myopia need to wear them every night.
The therapy is safe, reversible, highly effective, much cheaper (about $1,200 in total, including consultation and follow-up) than laser surgery (about $5,000 for both eyes). Vision returns to its prior state when users stop wearing OK lenses.
It’s estimated that about two-thirds of myopic people can have their vision problems corrected in this way.
A pilot study by a team led by Dr Helen Swarbrick, a senior lecturer and contact lens expert in the UNSW School of Optometry and Vision Science, now has found evidence that a new “steep” OK lens design may be able to overcome long-sightedness
The study suggests that a steep lens could work by reshaping the wearer’s cornea to alter the eye’s focal length in the opposite way to the effect achieved by using flat lenses to correct short-sightedness (see graphic).
The study involved 10 young adults being fitted with steep OK lenses for four hours. Before-and-after tests showed a significant steepening of the subjects’ corneas and they also reported a small but significant reduction in long-sightedness.
A report on the study has been accepted for publication in the leading US science journal Optometry and Vision Science.
It will be the first research paper in a refereed scientific journal to show the potential for OK lenses to correct long-sightedness.
Dr Swarbrick comments: “Although the study involved only a small number of subjects, it’s very promising that we were able to achieve a measurable change even in such a short time. We now plan to expand on this preliminary study with a more extensive research program starting later this year, with industry backing.”
“It happens so fast it’s amazing”
She began researching OK lens therapy for short-sightedness in 1997 and was “a complete sceptic” at the time but soon became a convert when she saw them in action.
“It happens so fast it’s amazing: even after as little as 10 minutes of OK lens use, some short-sighted people can read unassisted a further two lines down an eight-line eye chart. After one night’s wear, some people can read up to six or seven lines down the chart.
“There’s increasing interest around the world; it’s an amazingly wide field of research and Australians lead the way both in research and in the design and manufacture of OK lenses.”
Fellow UNSW researcher, Ms Nina Tahhan, clinic research manager for the Vision Co-operative Research Centre, recently published a research report on myopic OK lens therapy involving 60 subjects. It confirmed that about three-quarters of the benefit is achieved on the first night alone and that very little further change occurred after the first week.
“People are a bit sceptical about it but I use them myself and I can tell you that I had glasses from the age of 15 and hated wearing them: now, I couldn’t even tell you where my glasses are,” says Ms Tahhan.
About 25 per cent of the Australian population – some five million people – are affected by myopia to varying degrees. About two-thirds of those are moderately affected and are potentially treatable with ortho-K lenses, Dr Swarbrick believes.
“It’s a very exciting therapy with dramatic results.”
Despite them having been in use nationally since the mid-1990s, less than 2,000 Australians have had the therapy so far, according to Dr Gavin Boneham, a Sydney optometrist.
Dr Boneham is President of the Orthokeratology Society of Australia, which represents practitioners in the field. He is also a part-time lecturer in optometry at UNSW.
“It’s a very exciting therapy with dramatic results,” he says. “You can put a lens on a person and start to see some improvement within an hour.
“Whenever you do it with patients they invariably say: ‘Why haven’t I heard of this before?’
“It usually takes only three or four days before they can go all day without contact lenses or glasses and there’s no problem with dry eye – which affects some contact lens wearers – because they only have them in at night.”
Modern contact lenses for overnight wear are permeable to oxygen, which greatly reduces the chances of infection and swelling.
Dr Boneham says the OK lens safety record in Australia is excellent, with only two recorded cases of infection resulting from their use. In both cases, poor hygiene was involved.
Dr Swarbrick recently analysed 38 published reports of serious complications from OK lens use throughout the world in the past four years and found that the vast majority were from the People’s Republic of China.
The types of infections reported there often involved bacteria associated with poor water quality. Dr Swarbrick says that the high infection rate in China emphasises the need for good hygiene, high lens quality and skilled practitioner training.
Interest in treatments for myopia in East Asia generally has increased markedly in line with the reported myopia epidemic there, she says.
“Up to half the children in many kindergarten classes in Taiwan now wear glasses, and 90 per cent of 18 year-olds there are myopic,” she says. “The sharp increase in myopia in East Asia has happened in just one generation.
“An increase in urbanisation, television, computers and intense education – requiring much greater use of close vision in the young – have all been raised as potential influences but we still don’t know exactly what’s causing it.”
Surveys of schoolchildren visiting the UNSW School of Optometry have not found a similar trend.
Dr Swarbrick will be the invited keynote speaker at the forthcoming Second Global Orthokeratology Symposium at Toronto, Canada, in July, where she will also receive the Rodger Kame Memorial Award for her research on the issue.
Images are available to go with this story at: http://www.science.unsw.edu.au/news/oklens.asp