Ortho-k for myopia control

• Ortho-k provides two benefits: correcting blurred vision from myopia, and slowing down myopia progression which is called myopia control.
• Ortho-k has the largest volume of evidence for myopia control in children and teenagers, compared to other treatments.
• How ortho-k provides a myopia control effect is believed to be due to the way it alters how peripheral light rays are brought to focus in front of the retina.
• If ortho-k is being used for myopia control and lens wear is stopped, it is important that eyes are carefully tracked to ensure that myopia remains stable, with ortho-k wear resumed if myopia is found to progress faster than expected.

Myopia, also known as short-sightedness or near-sightedness, is not just about a pair of glasses. Once myopia (shortsightedness) in children and teenagers develops, it typically progresses or worsens every few months until the late teenage or early adulthood years.¹

Myopia progression brings with it:

• Increasingly blurred vision
• The need for frequent changes in spectacle or contact lens prescription
• Increased risk of eye diseases and vision problems over a person’s lifetime.²

'Myopia control' has become the increasingly adopted term to describe any approach that aims to slow progression of myopia.

The good news it that there is now a huge body of evidence to support that myopia control can be achieved using specially designed glasses, contact lenses and ortho-k.

Ortho-k is a special type of rigid contact lens which is worn overnight, while sleeping, to gently reshape the cornea (the clear dome at the front of the eye) so that daytime wear of glasses or contact lenses is not needed.³

Ortho-k is one of the first myopia vision correction options that has also been recognized to provide a myopia control effect, with current research indicating that ortho-k offers around a 50% myopia control effect.^4,5 This means that ortho-k slows myopia progression by around a half compared to vision correction with standard single vision glasses or contact lenses.

How ortho-k provides a myopia control effect is not fully understood, but the most widely accepted reason is that it changes the way that light is focused inside the eye.

Ortho-k corrects myopia by gently flattening the cornea by a controlled amount. The cornea works like a lens, and through being flattened its focusing power is modified to bring light back into focus on the retina and correct vision.

It just happens that the way the cornea is flattened by ortho-k also creates a unique shape profile, which causes some light rays to bend in different ways. The light rays that enter the cornea most closely to its center, called central light rays, are brought into focus at the center of the retina to provide clear vision. The light rays that enter towards the edge of the cornea are called peripheral light rays, and these are instead brought into focus in front of the retina.

Studies have shown that myopia eye growth can be slowed when peripheral light rays are focused in front of the retina, which is exactly what ortho-k does when it is used to correct myopia.³ Researchers explain that bringing peripheral light rays into focus in front of the retina acts like a stop signal for eye growth.

There are many different contact lens manufacturers making ortho-k lenses, and consequently many different ortho-k lens designs in the market. The majority of published myopia control research into ortho-k has used these 'standard' types of ortho-k lens designs, which indicates that a myopia control effect can be expected from wearing a standard ortho-k lens design.

You've just learned that standard ortho-k lens designs provide a 50% myopia control effect. While this is still around the largest myopia control effect that can be expected right now,⁶ researchers are still keen to see if ortho-k's myopia control effect can be improved.

The approach that most researchers have taken is to modify ortho-k lens designs so that they either bend more peripheral light rays to focus in front of the retina, or increase how far in front of the retina the peripheral light rays are focused. The general premise is that this will create a stronger myopic eye growth stop signal and thereby a stronger myopia control effect.

Current research shows promising signs that ortho-k lenses can be modified to increase the myopia control effect, although these modified lenses can be slightly less easy to fit. More longer term studies are needed.⁷

The short answer is yes. Ortho-k provides a 50% myopia control effect, causing it to slow myopia progression by around half.^4,5 This means it's normal for myopia to progress even while wearing ortho-k lenses for myopia control, and this should in fact be expected.

How much myopia will progress while wearing ortho-k lenses depends on many factors, particularly age, sex and ethnicity. Myopia typically progresses at a faster rate in younger years, which varies between boys and girls at different ages, and typically progresses faster in Asian compared to Caucasian children.¹

At eye care visits, the optometrist or eye doctor is able to measure myopia and compare against average expected myopia progression rates to advise whether myopia is progressing as expected. However, you need to be aware that knowledge on human myopia progression is still growing, and there are currently no fully reliable measures for how much and how fast myopia will progress in an individual. This means that the eye doctor can only advise whether myopia is progressing within the expected range.

The International Myopia Institute recommends six monthly checkups when ortho-k is used for myopia control.⁸

Most myopia progression typically occurs throughout childhood and comes to a stop in the late teens or early adulthood,¹ though it can continue throughout the twenties. Ortho-k lenses can only control myopia progression while wear continues, which means that to be effective for myopia control, ortho-k wear should be continued throughout childhood.

There is limited research on what happens to myopia progression when ortho-k wear is stopped, but one study reported that children who stopped before age 14 experienced faster progression, or a 'rebound effect'. This was resolved as soon as ortho-k wear was recommenced.

Their advice was that myopia progression should be monitored closely if ortho-k for myopia control is stopped, and ortho-k wear resumed if myopia is found to progress faster than during ortho-k wear.⁹

Research has shown that atropine eye drops can be used at night, before putting on ortho-k lenses, to increase the myopia control effect of ortho-k. The combined effect appears to happen only in the first six months,¹⁰ and more research is needed to understand for whom this could be most beneficial.

Because myopia typically progresses faster at younger ages,¹ it would be beneficial to start any myopia control treatment at the earliest opportunity, and ideally from when myopia is first detected.⁶

However, when it comes to ortho-k, age limits are introduced because a child needs to be capable of handling ortho-k lenses and being comfortable with the measurements that need to be taken. How young will depend on the individual child but published studies have included children from age 6.³

For age specific content on ortho-k for myopia control see our following articles:

• Ortho-k for myopia control in children
• Ortho-k for myopia control in teenagers
• Ortho-k for myopia control in young adults

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7. Guo B, Cheung SW, Kojima R, Cho P. One-year results of the Variation of Orthokeratology Lens Treatment Zone (VOLTZ) Study: a prospective randomised clinical trial. Ophthalmic Physiol Opt. 2021 Jul;41(4):702-714.
8. Gifford KL, Richdale K, Kang P, Aller TA, Lam CS, Liu YM, Michaud L, Mulder J, Orr JB, Rose KA, Saunders KJ, Seidel D, Tideman JWL, Sankaridurg P. IMI - Clinical Management Guidelines Report. Invest Ophthalmol Vis Sci. 2019 Feb 28;60(3):M184-M203. 
9. Cho P, Cheung SW. Discontinuation of orthokeratology on eyeball elongation (DOEE). Cont Lens Anterior Eye. 2017 Apr;40(2):82-87. (link)
10. Tan Q, Ng AL, Cheng GP, Woo VC, Cho P. Combined 0.01% atropine with orthokeratology in childhood myopia control (AOK) study: A 2-year randomized clinical trial. Cont Lens Anterior Eye. 2022 May 30:101723. (link)
11. Gifford KL, Gifford P, Hendicott PL, Schmid KL. Zone of Clear Single Binocular Vision in Myopic Orthokeratology. Eye Contact Lens. 2020 Mar;46(2):82-90. (link)
12. González-Méijome JM, Carracedo G, Lopes-Ferreira D, Faria-Ribeiro MA, Peixoto-de-Matos SC, Queirós A. Stabilization in early adult-onset myopia with corneal refractive therapy. Cont Lens Anterior Eye. 2016 Feb;39(1):72-7. (link)