What is OrthoK?

OrthoK has been around for a long time, from around 1962 in fact which is when the first scientific journal paper on the topic was published. Back then practitioners found they could correct myopia (short-sightedness) by getting patients to wear progressively flatter rigid lenses manufactured in PMMA (Perspex) material. It was well known that wearing rigid lenses caused corneal distortion, so the inquisitive trail blazers of the time decided it a good idea to put this lens induced distortion to good use through fitting flat lenses to purposely flatten the cornea to correct myopia.

Lenses had to be fit in a progressive manner because they could only be fit slightly flatter than the cornea otherwise they would fall off the eye. A week or two would then need to pass for the cornea to flatten enough so that a new even flatter lens could be fitted. The lenses could only be worn during the day, and once full correction was achieved the final lens needed to be worn for at least part of the day so that the full refractive effect remained, otherwise corneal shape started to return towards where it has started. Sounds like hard, and expensive work!

Fortunately, things got much easier in the late 80’s, thanks to invention of computerised corneal topography; computer numerical control (CNC) lathes; and gas permeable materials. The collision of these three advancing technologies vastly improved measurement of corneal shape – giving a better model of the cornea to work from to design a lens; the ability to manufacture reverse geometry lenses – crude approaches of achieving this were possible prior to CNC lathes but CNC lathes simplified the process and vastly improved repeatability of manufacturer; and gas permeable materials made it possible for the lenses to be worn safely overnight.

Almost overnight OrthoK became accelerated OrthoK, accelerated because reverse geometry designs allowed practitioners to jump straight to fitting the end lens and achieve the full refractive effect in a vastly reduced period without the interim stage lenses. Ability to wear overnight meant that day time wear to retain the effect was no longer required.

Nowadays the ‘accelerated’ term has largely been dropped. At your fingertips you can now select from a multitude of lens designs and through following some simple steps establish the best fit lens that when worn overnight is highly likely to fully correct within 1 week -  it’s hard not to get excited about that! No need for glasses during the day, no need for contact lenses that can become uncomfortable during the day and aggravate dry eye, freedom from eye correction when playing sports, the list goes on.

This practitioner led approach in OrthoK development is still alive and kicking. Practitioners break new ground and the research to support or help modify their actions follows, making it an exciting modality of contact lenses to be involved in fitting.

Now that you know how OrthoK was born and came of age, it’s your turn to get involved in fitting them. With growing evidence for slowing progression of myopia, OrthoK is in its heyday, but I’m convinced the story still has a long way to go – what part will you play?

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About Paul

Dr Paul Gifford is a co-founder of Eyefit, an information resource to assist contact lens practitioners in all modes of practice. Learn more about him here.