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ORTHOKERATOLOGY
(ORTHOK)
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The word Orthokeratology (also known as OrthoK) is derived from the Greek word “ortho”, meaning straight or correct; “kerato”, meaning cornea (the front window that allows light to enter the eye and focus it) and “ology”, meaning study of. The term OrthoK therefore refers to the altering and or straightening of the shape of the cornea to change the way it focuses light, thereby correcting vision.
OrthoK provides clients with the freedom to enjoy what they love, without the need for glasses or contact lenses during the day. This is particularly useful for active people who regularly participate in sport and fitness. And arguably most importantly, in addition to the possible benefit of slowing down myopia progression, OrthoK is also ideal for children and teenagers as it gives them the freedom to learn and enjoy all aspects of life without having to worry about using glasses or contact lenses during the day. In addition, this provides parents with the peace of mind that their child has the high level of vision they need to thrive.
OrthoK is effective for many occupations and working environments where traditional contact lenses and glasses may not be ideal, such as physical, dusty or weather-dependent environments. Furthermore, OrthoK is an option when traditional contact lenses become intolerable due to dry eye. If you are myopic or your child spends lots of time indoors reading or using digital devices, they are at risk of developing progressive myopia and may benefit from OrthoK.
OrthoK involves the design and fitting of custom manufactured contact lenses that are worn whilst asleep and then removed upon waking up. Throughout the night these specialised contact lenses gently reshape the cornea in a controlled fashion. Once the OrthoK contact lenses are removed, the end result is improved vision without any optical correction required during the day. OrthoK has predominantly been used to correct short-sightedness (myopia); however, recent advances in the technology mean OrthoK is now available for long-sightedness (hyperopia), astigmatism (two different focal points) and presbyopia (age-related near sight loss).
OrthoK contact lenses do not physically touch the cornea in the centre. Instead, the exactly-designed back surface of the contact lens manipulates tears, creating hydraulic pressure (pressure created by a fluid) that redistributes the tissue of the top layer of the cornea (known as the epithelium). For short-sightedness, the hydraulic pressure pushes the central part of the epithelium outward i.e. toward the edge of the cornea. As a result, the central cornea is reshaped into a flatter surface which focuses light rays properly onto the retina (the tissue that detects light at the back of the eye), similar to standard contact lenses and spectacles.
This process is similar to how refractive laser surgery such as LASIK works, but in refractive laser surgery a laser is used to precisely “cut” away parts of the cornea to reshape it and correct a prescription. OrthoK is an ideal alternative as it achieves a similar result to surgery while being less invasive (no surgery is involved). No optical correction is worn during the day, and if OrthoK lens wear is stopped, the elastic nature of the cornea means it simply reverts to its original shape. OrthoK is therefore completely reversible, unlike surgery where once the cornea is “cut away” in LASIK, it cannot be put “back in”.
Numerous scientific investigations have provided evidence that OrthoK may slow down the progression of short-sightedness (myopia), and it is utilised for this purpose worldwide. Myopia is caused by the eyeball growing too long; as a result, light is focused in front of the retina, causing blurry vision. With traditional spectacles and contact lenses, light is focused exactly on the retina centrally, providing clear vision. However, peripherally, light is actually focused behind the retina, encouraging the eye to grow longer and increasing the level of myopia. In myopic OrthoK, the central tissue of the cornea is pushed outward, flattening the central surface to focus light on the central retina and provide clear vision. The tissue that is pushed outward accumulates around the peripheral cornea, making it steeper so light rays are focused in front of the retina peripherally (the opposite of traditional spectacles and contact lenses). This peripheral “defocus” is thought to signal to the eye that it does not need to grow any longer, thereby slowing down the progression of myopia.
Myopia is more than just a spectacle prescription, it carries very real risks of developing potentially blinding ocular health complications such as retinal detachment and glaucoma if left to progress unchecked. OrthoK is one of the options available for slowing the progression of myopia – click here to read more about myopia control and options available.
Mortimer Hirst was one of the earliest adopters of OrthoK and our clinical team strive to be the leaders in this very specialised area of contact lens fitting. The optometrists at Mortimer Hirst regularly publish peer-reviewed scientific articles on OrthoK and are actively involved in research on OrthoK at the University of Auckland. Current investigations include determining what factors affect how successful OrthoK will be and methods of making the results more predictable. The clinical team specialise in OrthoK as a whole, including complex myopic OrthoK fittings and the recent advances in OrthoK that enable its use for hyperopia, astigmatism and presbyopia.
Mortimer Hirst utilises state of the art OrthoK fitting technology, including the latest hardware and software to custom design OrthoK lenses based on various individual factors. This includes the use of corneal topography; a device used to produce a three-dimensional map of the shape of the cornea. The scan is carried out in seconds and is non-contact (does not involve anything touching the eye). The optometric contact lens specialist then utilises the three-dimensional corneal map to design custom bespoke OrthoK contact lenses. This means that every client fitted with OrthoK receives contact lenses custom designed specifically for their eyes. This is of utmost importance to achieve the best possible vision and maintain long term safety with lens wear since all eyes are unique.
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