What is Orthokeratology?

Orthokeratology (also known as OrthoK, OK, corneal reshaping, corneal refractive therapy (CRT), or vision shaping treatment (VST)) involves gently reshaping the cornea to temporarily modify or eliminate refractive error. OrthoK is an innovative way of wearing contact lenses – custom lenses are worn overnight, temporarily altering the shape of the cornea enough to produce clear, lasting vision after removal and throughout the day.

The History of Orthokeratology

Reshaping the cornea with contact lenses to improve vision isn't new. Orthokeratology has been practiced by some eye doctors for decades. OrthoK was first introduced to contact lens practitioners by the famous optometrist George Jessen in 1962. The initial flurry into orthokeratology was hindered by poor technology and understanding of the criteria needed to successfully and predictably correct myopia.

With these changes there has been an upsurge in interest in the technique among contact lens specialists. There has also been an enormous interest in the technique among researchers and academics that has resulted in an exponential increase in the numbers published on this technique and an increased amount of funding for research from governments and industry bodies.

Increasing myopia is becoming an epidemic in some Asian countries, where up to 80% of adults have this condition. Recent findings on the ability of ortho k lens wear to slow the progression of myopia means that the lens modality could become a major technique for the control of myopia progression. As such orthokeratology is now in a position where it is ready to become a part of mainstream optometric practice.

How does Orthokeratology work?

Orthokeratology is the use of contact lenses to mould the shape of the cornea to reduce or correct myopic

It can be likened to the use retainers by an orthodontist to straighten teeth. The main difference however is that if a tooth’s position is corrected for some time it will remain in the new position.

The Cornea (front window of the eye) is highly elastic, and always returns to its original shape. This is why retainer lenses are worn several times per week during sleep to maintain the moulding effect once the correct corneal shape has been achieved.

Who is suitable for Orthokeratology?

Orthokeratology is perfectly suited for anybody who wants clear natural vision all day, every day.

• Mild to moderate myopia (-0.75 to –5.00D)
• Mild hyperopes, upto +3.00D
• Presbyopes – monovision corrections
• Active individuals or those with occupational demands not suited to standard RGP or disposable contact lenses.
• Lose their contacts easily, or suffer from allergies from some contact lenses.
• Have considered refractive surgery because of the freedom it provides, but are worried about the risks
• Have difficulty with dry eyes from air conditioning, computer use or dusty environments
• Find soft contact lenses do not fulfil the comfort demands their lifestyle places on their eyes

Myopia Control and Orthokeratology

Practitioners who fit orthokeratology lenses sometimes comment that the normal increase or progression of myopia in children is slowed when these lenses are worn. Although these anecdotal reports are encouraging, at present there is no scientific proof of myopia control with orthokeratology lens wear.

A recent study from Hong Kong suggested that myopia progression may be slowed by up to 50% during overnight orthokeratology. Similar results have also been reported from a study conducted at Ohio State University. However, the authors of these studies found that there was no way to predict the effect for individual children. There were also a number of scientific weaknesses in the design of these studies, and because of these limitations the results are not definitive.

Further research is currently underway to determine whether orthokeratology lenses can reduce the rate of progression of childhood myopia, using more rigorous study designs. The MCOS study, being conducted in Spain, is comparing two groups of children wearing overnight orthokeratology versus spectacles, while the SMART study in the US is comparing orthokeratology with silicone hydrogel contact lens daily wear. A different approach is being taken in a study in Sydney, in which children wear an overnight orthokeratology lens in one eye, and a conventional daily wear rigid lens in the other. Results from these studies are expected in the next year or so, and are awaited with interest.