Myopia (short-sightedness) has been recognised as one of the five leading causes of blindness and visual impairments in the world by the World Health Organisation. Research shows there are a number of options to slow myopia progression, and thus reduce the associated increased eye health risks including glaucoma, macular degeneration and retinal detachment. One of these is overnight Orthokeratology, often referred to as Ortho K or Ortho-K. Although most of us are familiar with spectacles and daytime wear contact lenses, I often get asked in practice what is Ortho K? Is it true that I can see clearly through the day with no daytime correction?! The answer is yes!
I absolutely love seeing the great, big smile on a child’s face after a week of wearing Ortho-K lenses and their excitement (and their parents!) of reading many more lines down the vision chart. My first experience with Ortho-K was in high school when my mum was fitted with these lenses to correct her myopia, and I am just as excited now about Ortho-K as I was back then. It seems like magic! But in fact, it’s a scientifically verified and safe way to correct vision in myopia.
So, what is Orthokeratology?
Ortho K are custom-made rigid lenses that are worn overnight. They gently reshape the cornea (the clear dome at the front of the eye) so that you can see clearly during the day without the need for glasses or contact lenses. This provides lifestyle benefits, particularly for active children and adults, sports and recreational activities. The corneal reshaping is reversible. Thus if you stop wearing the Ortho K lenses, your eye shape and prescription will return to its pre Ortho K baseline. It is also an alternative to LASIK or other refractive surgery for adults. There is some awareness of the Ortho K lens on eye initially when applied and there is generally very good adaptation and comfort. It can be worn to correct vision in children and adults.
How does Orthokeratology slow myopia progression?
Orthokeratology lenses in myopia correction are designed with a flatter central curve; creating a positive pressure centrally and a negative pulling pressure in the mid-periphery of the cornea. This redistributes the cells in the front layer of the cornea to the mid-periphery, creating a transient volcano-like shaped treatment — flatter in the centre and steeper in the mid-periphery. Don’t worry, we can only see this ‘volcano’ shape when measured on our instruments, not with the naked eye, and you can’t feel the shape underneath your eyelids either!
The corneal reshaping allows light-rays to focus accurately on the centre and mid-periphery of the retina (the light sensitive ‘film’ layer at the back of the eye), providing clear vision. The defocus of the peripheral light in the eye is theorised to slow myopia progression and stabilise eye growth. The effect of Ortho K in changing eye muscle coordination, particularly for eye muscle postures shown to be risk factors for myopic progression, is another suggested hypothesis for its proven effect in slowing myopia progression.
Is my prescription suitable for Orthokeratology?
Orthokeratology can be used to correct myopia (short-sightedness), hyperopia (long-sightedness), astigmatism and presbyopia (blurred near vision that commences when we reach our 40s). To assess if you are a good candidate, your optometrist will map the front surface of your eye with an instrument called a topographer. Similar to geographical topography showing the hills, valleys and physical shape of the landscape, this corneal map will indicate whether the shape of your eye combined with your prescription will provide clear vision from the Ortho K. It is also used to custom-make the Ortho K lens for your eye shape. As described above, due to the central flattening in myopia Ortho K correction, a naturally very flat cornea and/or higher prescriptions can be more difficult to achieve full refractive correction. However for myopia control purposes, there is research indicating that even partial myopia correction with Ortho K (and the remaining prescription corrected with glasses) can slow myopia progression and eyeball length growth in children.
Is it safe?
Research shows that Orthokeratology is a safe treatment for correcting vision and use in myopia control. There is a small risk of a serious eye infection with any type of contact lens wear, but these risks are low – read more about contact lens safety in children via this link. There also appears to be decreased risks of inflammatory conditions in children aged 8–15 years, compared with older teenagers and adults. Each child is different though and parents, practitioners and the child can determine together if it is appropriate. The risks of adverse events are reduced by strictly following the cleaning and maintenance practices that your optometrist discusses with you and attending regular eye examinations.
Where do I find an eye care practitioner that fits Orthokeratology?
Just over 1% of eye care practitioners worldwide fit orthokeratology contact lenses. You can find your local practitioner in Australia and New Zealand by searching on http://www.oso.net.au/where-do-i-get-it, or if you’re located in another part of the world search on https://www.orthokacademy.com/find-an-ortho-k-doctor2/ or https://www.eurok.eu/practitioners.