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Ortho-K, short for orthokeratology, is a relatively new concept to many Australians. Most people may not have heard of it before, or know what it does, or how it works. If you're reading this page you probably want to learn more about Ortho-K and how it might help you or your child see clearer. In the next few eye blogs I will go into detail to explain everything you need to know about Ortho-K overnight contact lenses, which I believe is the future of vision correction.
What is Ortho-K?
Ortho-K is a special type of vision correction technology that uses a breathable rigid contact lens to change the shape of your eyes as you sleep. Also called Sleep Lenses or Night Contacts, you put on the lenses just before you go to bed, and when you wake up in the morning you remove your lenses and enjoy clear vision for the rest of your day, without wearing glasses or daytime contact lenses.
How does it work?
Ortho-K sounds amazing because it really is. Our Ortho-K patients find it incredible to get their clear vision back without needing to wear glasses or contacts during the day. No more dry eyes or discomfort at work, and for kids no need for the parents to worry about them losing their glasses or contacts at school. The science behind this technology is a little complex, but here's a brief explanation of how it works.
For correction of short-sightedness (blurred vision in the far distance, also known as myopia), an Ortho-K lens flattens a central 5-6mm zone of your eye's front surface, the cornea. This surface flattening is similar to what happens with laser surgery (LASIK), only that Ortho-K is a temporary and reversible process and laser surgery is permanent. Flattening the cornea by a precisely calculated amount bends light to refocus it onto the surface of your retina, restoring your vision.
An Ortho-K lens a specially designed rigid contact lens made to precisely fit the shape of your eye's surface. Every lens is tailor-made for each eye's shape and prescription. At Eyecare Concepts we use the sophisticated Medmont E300 corneal topographer (pictured below) with 102,000 individual points to scan your eyes' unique surface contours to generate 3D topographical maps of its shape. We then use this topography data and advanced computer simulation software to design your lenses to fit your eyes perfectly. The information we can capture is so precise that we can design the fitting of your lenses with an accuracy level measured in microns (0.001 mm).
The image below shows how an Ortho-K lens works on the eye to correct vision. The lens, together with the eye's natural tear layer and eyelid in its closed state during sleep, places gentle hydraulic forces on the eye's surface, to gradually mould its shape by the precise pre-determined amounts required to give clear vision. You never feel any addition pressure on your eyes while wearing the lenses during sleep as the forces are very gentle. The centre of the lens does not actually directly touch the centre of the eye's surface but rather it vaults over the centre, and supported by a very thin film of tears, by approximately 20 microns (0.02 mm) — less than half the thickness of a strand of human hair. This is the kind of precision involved.
The shape of an Ortho-K lens is different from other kinds of contact lenses. It is also technically known as a 'reverse geometry lens'. There are multiple curves on the back of the lens surface that create different pressure zones and for helping the lens to centre correctly on your eye as you sleep. The fluro-green areas on the right-side image show the areas where the shape of the lens changes from the central 'treatment zone' to the peripheral 'alignment zone'. This lens is fitting perfectly on the eye with a well-centred and even treatment zone, important for good, clear vision. The green glow is from fluorescein dye placed on the eye during the lens evaluation process. Normally the lens is completely clear.
The left-side image is a 3D topography map of an eye following Ortho-K vision correction — showing flattening of the central zone of the eye surface (circular area in green), surrounded by a peripheral band (in red) of surface elevation changes which also helps to control short-sightedness progression in children and teenagers (myopia control) using Ortho-K lenses.
Below is an example of one of our patients successfully fitted with Ortho-K lenses. The upper-left image is her natural eye surface shape before Ortho-K lens treatment. She had a prescription of -3.00 short-sighted plus a mild amount of astigmatism. The lower-left image shows the post-treatment shape of her cornea after Ortho-K lens wear. The red ring represents the positioning of her lens during sleep, showing excellent lens centration. On the right image the centre blue zone is the vision correction zone and is the ideal treatment effect that we are looking for. Her -3.00 prescription and astigmatism was fully corrected with Ortho-K, giving her 20/20 vision in just 1 week.
EYECARE CONCEPTS — MELBOURNE ORTHO K PRACTITIONER
Philip Cheng - B.Optom (Melb) Ocular Therapeutics (GCOT). Optometrist at Eyecare Concepts Kew East, Melbourne. An experienced eye care & contact lens practitioner with expertise in myopia control & orthokeratology.