The key to 20-20 vision could be as simple as a good night’s sleep.
First developed over 40 years ago, the relatively unknown practice of orthokeratology (Ortho-K) uses corrective contact lenses to re-shape the cornea (the clear outer layer of the eye) while the patient sleeps, bringing the eye into focus.
The cornea retains its corrected shape for up to 20 hours after the contact lenses are removed, allowing for perfect vision without glasses or contact lenses.
The treatment is recommended for people who work in dry, dusty or air-conditioned environments (where it’s often difficult to wear contact lenses) as well as for athletes and emergency workers, when reliance on visual aids could be a liability.
Approximately 25% of adults worldwide suffer from myopia or short-sightedness, a condition where the eyeball is too long or there is too much curvature in the cornea; this causes light entering the eye to focus incorrectly on the retina, making distant objects appear blurry.
Scientists have known for centuries that pressure on the eye can create a temporary improvement in vision — an ancient Chinese remedy used sandbags placed on the eye to prevent short-sightedness — but it’s only recently that improved diagnostic tools and contact lens technology have made the treatment both safe and effective.
Ortho-K can be used to treat myopia of up to -6,00 diopters (studies are underway for the treatment of far-sightedness) with no or little astigmatism. Before treatment patients’ eyes are mapped using corneal topography, to determine accurately the cornea’s shape. This allows the optometrist to custom design a lens for each eye and establish whether or not the patient is a good candidate for Ortho-K.
People with thin corneas may not be suitable candidates as Ortho-K further thins the centre of the cornea. Ortho-K is also contra-indicated for patients with severe dry eyes, eye disease or frequent eye infections. Because the treatment involves the long-term use of permanent (rather than disposable) contact lenses, a high level of hygiene compliance is essential — protein build-up (proteins are present in human tears and often collect on contact lenses) can reduce the effectiveness of the lenses, while the presence of bacteria can lead to serious eye infections.
Patients also have to be prepared to wear their Ortho-K lenses for at least five hours a night, explains optometrist Natasa Tsangari. Because the lenses’ effects are temporary, missing even one night could see patients waking up with imperfect — and unknown — vision, depending on how much the cornea’s shape has regressed. Researchers are working on eye drops that will help the cornea retain its improved shape for longer periods, adds Tsangari.
It can also take up to a week for the Ortho-K lenses to be effective, meaning first-time users will experience several days of transition at varying prescriptions.
‘At first it’s a bit uncomfortable, but after a week you hardly feel the lens,” Tsangari says. What patients will feel is the price: Ortho-K will cost anything upwards of R6 000 (including consultations and two lenses).