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Orthodontics corrects teeth. Orthopaedics corrects skeletal injuries.
Orthokeratology corrects the cornea (front surface of the eye).
It is a non-surgical, reversible procedure in which specially designed contact lens devices are used to reshape the front surface of the cornea of the eye gently and gradually.
The Ortho-K lens devices are only worn during sleeping hours. On waking, the lenses are removed. The reshaped corneal surface allows clear and natural vision for the rest of the waking day without the need for prescription glasses or contact lenses.
In June 2002 the American Food and Drug Administration (FDA) granted approval to overnight Orthokeratology stating it to be a safe and controlled procedure. Currently there are about 50 optometrists in South Africa that are fully trained to do the overnight Orthokeratology procedure.
Suitable candidates
Orthokeratology is ideal for children and adults with prescriptions ranging from -1.00 to -10.00 dioptres of myopia (nearsightedness) and from +1.00 to +5.00 dioptres of hyperopia (farsightedness). Currently only low to moderate amounts of astigmatism can be corrected.
New designs are currently being tested, which will allow for the correction of high astigmatism, presbyopia (reading problems for the over 40’s) and post-LASIK (refractive surgery) patients who still have some residual myopia (nearsightedness) or irregular treatment areas.
How it is done
The first step is to receive a complete eye exam from an optometrist, who is registered with the Health Professions Council of South Africa, and who is trained to do Orthokeratology. During the exam, a comprehensive pathology screening is done to rule out any disease in the eye and especially the cornea. An accurate prescription is also obtained which is necessary to calculate the correct Ortho-K lens.
An exact measurement of the shape of the cornea is then taken. This is done with a corneal topographer, which produces a three-dimensional topographical map of the cornea by measuring up to 22 000 points on the corneal surface.
Once the exact curvature and shape of the cornea is known, Ortho-K lenses are specially designed to fit the shape of your eye. These lenses are then worn during sleeping hours. Once the Ortho-K lens is in the eye, they operate like normal contact lenses, allowing clear sight. On awakening, the lenses are removed, but your sight still remains clear. No glasses or other contact lenses are required during the waking day to see clearly.
How it works
While you sleep, the lens moulds the cornea using fluid forces to conform the cornea to reverse geometry design of the lens. This produces a flatter central cornea and steepens the peripheral cornea, correcting the nearsightedness.
In the case of hyperopia and presbyopia, the cornea is conformed to the double reverse geometry design of the lens, steepening the central cornea and flattening the peripheral cornea, correcting the farsightedness.
Improvements can usually be seen the next day, with the procedure stabilising after a week. With the high minus powers (correcting myopia over -6.00D), the procedure takes from two to four weeks to stabilise. Ortho-K does not make any permanent changes to the eye surface. Your eyes will revert to their former state within one to four weeks as soon as you stop using the lenses.
The risks involved with the treatment are the same risk as for any contact lens wearers ranging from allergies to bacterial infections due to poor hygiene.
The lenses are surprisingly comfortable to wear and most people comment that they forget they have lenses in their eyes after the first night of sleeping with the lenses.
Benefits
Ortho-K holds particular appeal for:
- People who participate in sport, especially contact and water sports
- People working in dusty or dirty environments that can cause problems for regular contact lenses or spectacles
- People who are contact-lens-intolerant due to dry eyes, allergies or environmental factors
- Children. Apart from improving their vision, children and especially teenagers benefit from the improved self-esteem, the ability to play all sports, and the ability to wear designer sunglasses. Parents don’t have to worry about contact lenses, because they’re left at home where they can’t be lost or damaged.
In short, Ortho-K works best for people who don't want to wear glasses or contact lenses all day, but don't mind wearing contact lenses while they sleep.
Ortho-K is also not for everyone. You have to have a healthy cornea that is free of any disease. The same corneal health criteria that holds true for any of the refractive surgery corrections like LASIK, holds true for Ortho-K.
If your primary goal is not to handle contact lenses or spectacle frames each day, other alternatives should also be considered like extended wear (EW) soft contact lenses.
The EW contact lenses are made from a new lens material called silicone hydrogel. The new material provides enough oxygen to the cornea to allow people to sleep with the lens. The American FDA has approved the lens to be worn continuously for up to 30 days.
(Charl Laas, Originally published January 2006)
Useful resources:
South African Optometric Association
Tel: 011 805 4517
South African National Council for the Blind
Tel: 012 452 3811
Retina South Africa
Tel: 011 622 4904
Ophthalmological Society of South Africa
