Welcome to the Research in Orthokeratology (ROK) group at the School of Optometry & Vision Science UNSW, Sydney.
Orthokeratology is a clinical technique of correcting mild to moderate degrees of short-sightedness through corneal reshaping using specially designed rigid contact lenses.
ORTHOKERATOLOGY (also known as OK, ortho-k or corneal refractive therapy - CRT) is a clinical technique of corneal reshaping using specially designed rigid contact lenses. In modern OK, lenses are usually worn only during sleep and are removed first thing in the morning. During the night the contact lenses gently reshape the front surface of the eye, correcting the refractive error and allowing clear vision through all waking hours without the need for spectacles or contact lenses.
We can correct low to moderate degrees of myopia (short-sightedness) with OK. If you know your prescription, this translates to a maximum of about 4.00 to 5.00 dioptres of myopia. The correction is achieved by applying gentle pressure to the centre of the cornea (the clear window of the eye) to flatten it slightly. This reduces the optical power of the cornea, thus correcting myopia.
OK lenses for myopia may correct about half of your astigmatism, but this varies from patient to patient. Some practitioners, particularly in Europe, are experimenting with complex toric lens designs to correct astigmatism.
New lens designs for the correction of hyperopia (long-sightedness) are being developed here in Australia and in the USA. These lenses aim to gently steepen the cornea, increasing corneal optical power and thus correcting hyperopia.
There are currently no OK lens designs specifically to help people who require glasses for reading. This condition is known as presbyopia and affects everyone over the age of 40 years. We have recently commenced trials of new lens designs aimed at creating a multi-focal cornea, to assist those patients who require glasses for correcting both near and far vision.
Apart from the refractive status of your eye, there are many other factors that may influence your suitability for overnight OK lens wear. In general, this procedure is only suitable for people with good ocular (and general) health and low prescriptions. Patients must have the dexterity to handle the lenses for insertion and removal and must closely follow practitioner instructions on lens wearing schedule and lens care procedures, to ensure safe lens wear.
No, the effect of overnight OK lenses on corneal shape is temporary, and temporary and wears off over a few days if the lenses are not worn. To maintain the optical effect, lenses must be re-inserted and worn every night (or in some cases, every 2nd second or 3rd third night).
As with all contact lens wear, there are some risks associated with OK treatment. Strict adherence to practitioner instructions on lens wear, handling and care is essential to minimise these risks and ensure safe lens wear. This is important because OK lenses are worn in the closed eye, which is a riskier environment than the open eye. In our previous studies we have not experienced any serious adverse reactions to OK lens wear. However, corneal infections resulting in scarring and loss of vision have been reported with this type of lens wear, particularly in Asia where clinical standards are not as strict as in Australia.
If you are a low to moderate myope and would like to find out more about being fitted with OK lenses, the Orthokeratology Society of Oceania lists appropriately qualified Australian orthokeratology practitioners on its website.
We’re always interested in recruiting subjects with different refractive errors (including myopia, hyperopia, presbyopia and astigmatism) to take part in our research at UNSW. If you’re interested in participating in our research, please contact us. Or you can fill out our ROK participants form.