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A question on parents' minds when considering Orthokeratology treatment for their children is the aspect of safety. Is Ortho K safe?
In short, yes. Parents can be assured that Ortho K treatment is a safe form of vision treatment for their children.
There are some risks, as with any other kinds of contact lens wear. The main risk factor of concern is the possibility of eye infection, or microbial keratitis (infection and inflammation of the cornea, the clear surface of the eye).
But Ortho K lenses, which are custom-shaped rigid lenses worn overnight, are not statistically more risky to wear than regular, monthly-disposable soft contact lenses. As Ortho K treatment occurs at home during sleep, in a controlled safe environment, the lenses are also not exposed to outdoor environments or water elements (swimming, showering) during the day time.
The risk of microbial keratitis for an Ortho K lens wearer is estimated at only 13 per 10,000 wearers, per year. That's a statistical risk of just 0.0013% per year.
So a serious infection event with Ortho K treatment is actually extremely rare, when OK lenses are professionally fitted by a reputable practitioner, and worn with due care. In Australia, eye care practitioners are highly regulated. As such, the vast majority of Ortho K lens wearers in Australia never encounter any significant problems even after many years of using Ortho K.
Studies show Ortho K to be as safe for children as regular day-time contact lenses.
The key to safe Ortho K wear is to be vigilant and minimise risks, by maintaining high levels of hygiene standards, every single day. No shortcuts. No being complacent. We ensure that all our paediatric patients and their parents understand this.
This means thorough hand washing with anti-bacterial liquid soap each time before touching the eyes or the Ortho K lenses. Daily cleaning and sterilising the lenses and lens case every morning after removing the lenses, using new solution. The cleaning solution we recommend is AO Sept hydrogen peroxide.
Younger children wearing Ortho K lenses are not at any higher risk than teenagers or adults. Children are generally good at following instructions. In fact, adult wearers of regular soft contact lenses who have become complacent and do the wrong things (eg. sleeping in their regular contact lenses when not supposed to, or go swimming with their lenses, or not replacing their lenses regularly) are those at highest risk of microbial keratitis.
Successful, safe fitting of Ortho K also depends on the practitioner's skills and experience. Ortho K fitting is complex and unfortunately not every practitioner does it equally well. OK lenses that are fitted poorly can cause problems such as corneal staining and lens binding — while these are not serious problems they can increase the risks of Ortho K wear in the long term.
BE CAUTIOUS. IF IN DOUBT, ASK THE OPTOMETRIST
We ask our patients to have a close look at their eyes in the mirror each morning, ensuring the eyes appear white and feel comfortable.
Our patients understand that whenever they have any concerns, however minor, to notify our optometrist right away. This includes any unusual redness or eye irritation. Our optometrist Dr Philip Cheng is qualified in ocular therapeutics, which means if there is a potential concern he can prescribe medical treatment right away to keep complications at bay. As part of our Ortho K service, we provide 24/7 support for our patients, with a direct line to our optometrist at all times.
From time to time, a minor case of viral or bacterial conjunctivitis (pink eye) is something that can happen to anyone, adult or child. It is not typically caused by Ortho K wear but rather it passes easily between people. Like a common cold. In the event of conjunctivitis we recommend taking a brief break from Ortho K wear until the redness subsides, usually after a few days, to minimise the risks.
Here at the Melbourne Myopia Clinic, your eye health is our priority. We maintain a 100% safety record with no incidence of microbial keratitis with any of our patients fitted with Ortho K lenses here.
How to ensure safe Ortho K wear:
Orthokeratology (Ortho K) is a better choice than regular glasses for children with myopia, but why is it so?
Myopia is the eye condition that make objects far away blurry, while objects up-close are clear. This is because the eye is too long for its focusing power, resulting in the image of a distant object being focused in front of the retina, rather than on it. People with myopia are also commonly called short-sighted, or near-sighted — often, people find these terms confusing.
Both glasses and Ortho K correct myopia by refocusing this out-of-focus image backwards onto the surface of the retina, so the image becomes clear. Glasses do this by bending light with a concave lens (a minus-powered lens). Ortho K restores clear vision by flattening the front surface of the eye (the cornea — the clear window where light enters the eye) by the use of a mould worn at night-time, reducing the curvature of the cornea so that light is focused further back, onto the retina.
So if glasses and Ortho K do the much same thing in restoring clear vision, why is Ortho K effective in slowing myopia progression in children but glasses are not?
The answer lies in how peripheral vision is corrected, not just central vision. When we see, the sharpest part of our vision comes from the central area of our retina, known as the macula. While our peripheral vision is also vital, objects that fall away from the centre of our vision isn't in sharp focus. We don't tend to notice this as our eyes are constantly moving to where we want to see.
Glasses are made to give us sharp vision in the centre of our vision, in our macula area. The optics of single-vision spectacle lenses, originally developed centuries ago, assume that the eye is a round sphere. In a short-sighted, or myopic, eye the shape of the eyeball is actually an oblong shape. Oval, not round.
The higher the degree of myopia, the more oblong the eye shape becomes, due to the eye being stretched and elongated length-wise. It is also this elongation that leads to significantly increased risks of eye disease development — glaucoma, retinal detachment, cataract and myopic macular degeneration are all associated with myopia.
What happens with glasses for correction of myopia is that while the central part of vision is in clear focus, peripheral vision is well out of focus, with the peripheral image being focused beyond the surface of the retina. The technical term for this phenomenon is called 'peripheral hyperopic defocus'. Myopia research in recent times has found that this image blur in the peripheral retina is part of what drives the progression of myopia in children.
When the eye senses the blurred peripheral image focused behind the retina it tries to grow to 'catch-up' to the position of this image — this is a stimulus for abnormal eye growth in myopia. And the greater the myopia, due to an increase in eye elongation, or a more oblong eye shape, the greater the mismatch between central focus and peripheral focus, and thus the greater the stimulus for the eye to continue growing longer. This is why regular glasses do not help slow myopia progression; in fact, the optics of glasses can accelerate progression by inducing further peripheral hyperopic defocus.
Glasses only correct central vision. Ortho K corrects both central and peripheral vision. Optimised focusing of peripheral vision is why Ortho K is better than glasses for children with progressive myopia.
With Ortho K, we can achieve different points of focus for central vision and for peripheral vision. We restore clear central vision by placing the central image onto the retina, and in addition we focus peripheral light on or in front of the retina, by means of a graded treatment effect that naturally occurs with Orthokeratology. Instead of having just one corrective lens power, as occurs with ordinary glasses, with Ortho K treatment there is a change of corrective power on the surface of the eye from the centre to the edge, more closely aligned to the oblong shape of the eye.
By reducing the peripheral image hyperopic defocus we reduce or eliminate the signals for the eye to grow longer. This more sophisticated way of restoring vision from the centre to the periphery, giving better focusing of light across the back of the eye, is why Ortho K can slow the progression of myopia when regular glasses cannot. For short-sighted children whose eyes are continually getting worse, Ortho K is a far better option than glasses in being able to correct their eyesight as well as reducing the rate of vision deterioration.