What is ortho-k? Parents' guide

• Ortho-k is short for orthokeratology. 
• Ortho-k lenses are worn during sleep to gently reshape the cornea so you can see clearly during the day without the need for glasses or contact lenses.
• Correction from ortho-k is temporary and requires ongoing overnight wear to maintain.
• To achieve a successful fitting, ortho-k typically requires more appointments than soft contact lenses.
• Initially, ortho-k can be less comfortable than regular contact lenses, but comfort usually improves dramatically within the first week. 
• Ortho-k is safe to wear as long as lens wear and care guidelines are followed, and ongoing follow-up care visits are attended.

Orthokeratology or ortho-k, describes custom-made rigid contact lenses that are worn overnight to gently reshape the cornea (the clear dome at the front of the eye). This allows temporary clear vision so that glasses or contact lenses do not need to be worn during the day.¹

Being able to have clear vision without needing extra assistance opens up a wealth of other benefits too. They are convenient for busy or active lifestyles, and particularly those who play sports or recreational activities.² 

In addition to correcting vision, ortho-k lenses are effective at slowing the worsening of nearsightedness.^3,4

In many ways the eye works like a camera. It has two lenses that focus light but instead of focusing light onto a computer chip or film, light is instead focused onto the retina.

The main focusing lens is the cornea, located at the front of the eye. The cornea normally has a fixed shape and provides around 75% of the eye's focusing power.

Inside the eye, another lens (called the crystalline lens) is flexible and can change its shape to focus objects at different distances. This action is what allows most people to maintain clear vision, as objects are moved closer to you, such as bringing a phone from far away to close up.

Ortho-k lenses improve vision by gently and temporarily flattening the front surface of the eye (cornea) - just enough to eliminate nearsightedness. When worn overnight, the gentle pressure of the closed eyelids helps keep the ortho-k lenses in place and flatten the cornea. 

Flattening the cornea has the effect of reducing the focusing power of the eye. Since myopia results from an eye with too much focusing power, reducing that focusing power brings it back to normal. With that, objects can focus perfectly on to the retina. Higher amounts of myopia need more flattening to correct the eye's focusing power.¹

Ortho-k lenses are removed upon waking up. With the shape of the eye temporarily fixed, wearers can enjoy their newly corrected vision throughout the day. In this way, ortho k lenses are considered as "vision retainers" for the eye. While dental braces correct the alignment of teeth, ortho-k retainer lenses help to correct the focus of the eye.

Corneal flattening from ortho-k is not permanent.

If you stop wearing the lenses, most of its effect will wear off in a few days.⁵ This is because ortho-k temporarily the front surface of the eye - the cornea.⁶ The cornea is gently compressed in some places and expands in others to match the profile of the ortho-k lens. When lens wear is stopped, the cornea gradually returns to its original shape.¹

In ortho-k, this is why it typically takes up to 1-week of overnight wear to achieve the full effect.⁷ 

The temporary effect from ortho-k offers some useful advantages when compared to the more permanent option of laser surgery, which removes tissue from the cornea. Ortho-k can be stopped at any time to allow the eye to return to its original shape. In fact, research shows that most of the ortho-k effect is reversed within the first week of stopping lens wear.⁵ For children, the temporary effect allows flexibility to adapt the ortho-k lens as their eyes continue to grow and change.

Myopia, also known as nearsightedness or short-sightedness, is becoming increasingly common in children. If a child develops myopia, it usually deteriorates (progresses) rapidly during school years, and sometimes even into early adulthood. Progressive myopia can lead to serious consequences on vision and eye health in adulthood, unless it is diagnosed and treated early.

Fortunately, a lot can be done to slow myopia progression in children, including prescribing special types of spectacles or contact lenses. Habits that are healthy for the eyes, like spending more time outdoors, and less time on close work and screens, can also go a long way. 

Ortho-k has been shown to slow progression of myopia in children by about a half, and currently has the most research supporting its myopia control characteristics than other myopia control methods.^3,4,8 

Specialized equipment and expertise are required to achieve a successful ortho-k lens result. In most countries the eye testing and ortho-k fitting process would be performed by an optometrist or eye doctor.

To check whether someone is suitable for ortho-k, both the refraction (eye prescription) and the shape of the cornea (the clear dome at the front of the eye) have to be measured. 

Corneal shape is measured using a special instrument called a corneal topographer. The topographer takes a picture of the cornea, and then converts it into a precise, three-dimensional model on a computer.⁹ This 3D model of the cornea is used to help determine which ortho-k lens will best fit the eye.

Your eye care practitioner may either select a pre-made lens that suits the model, or design a custom-made ortho-k lens, depending on various factors like the complexity of the model. Either way, the meticulous design process involved should result in a lens that fits extremely well to the eye - like a bespoke, tailored suit. 

By this stage, your eye care practitioner will be able to predict how well ortho-k will fit the eye, even before the lens is inserted.

If the initial stage is successful, a number of steps need to be followed to complete the lens fitting process. Because of the highly customized nature of ortho-k lenses, it typically involves more follow-up appointments compared to regular contact lenses.^1,9

A typical visit schedule will involve:

1. Eye examination: measurements such as the prescription and the cornea map will be used to decide which ortho-k lens to order.
2. Lens collection: where the individual will learn how to insert, remove, and care for ortho-k lenses.
3. After the first night of lens wear: a visit the next morning ensures that the wearer has completed a successful night of wearing the lens. This can be an early indicator of fitting success, but the full effect of ortho-k shouldn't be expected until 1 week of consistent wear.
4. After 1 week of lens wear: by this visit, the full effect of ortho-k can be expected and the eye care practitioner can assess whether adjustments need to be made to optimize the lens. In some cases, it can take a little longer to achieve full effect.

Ongoing visits will depend on whether or not the lens needs to be altered to improve the way it fits the eye. It is important to understand that real-life lens wear is needed to fully understand how each eye responds to ortho-k lens wear. Fortunately - once the optimal lens is achieved, ongoing appointments will start to spread out.

The eyes are sensitive parts of our body. Like breaking in a new pair of shoes, there might be mild discomfort at first, but ortho-k soon becomes comfortable after a few days of wear. 

Despite this, ortho-k lenses are not supposed to be painful. As each lens is either custom-made for an individual eye, or selected to very closely match the contours of the eye, this precise alignment should result in a lens that feels as comfortable as possible. 

For new wearers who are not used to the feeling of wearing a rigid contact lens on the eye, some initial mild discomfort or irritation is normal. It can feel like there is a bit of dust underneath the eyelid. This is simply due to the upper eyelid being aware of the lens on the eye, and is also called 'lens awareness'.

Typically, the eye will create tears to try and wash the ortho-k lens out because it thinks it’s a piece of dust. Eye watering happens when the eye wants to wash away something it recognises as foreign. Over time, comfort levels can improve to the point where the lenses may feel like they are not there at all.

Ortho-k lenses are safe to wear as long as proper lens care steps are followed. To minimize the risks of eye infection, lenses should be cleaned and disinfected daily, and stored in a safe container.

Studies show that the overall risk of eye infection is extremely low in ortho-k lenses, provided that the wearer follows consistent hygiene processes.^10–12 The safety profile of ortho-k is similar to daytime reusable soft contact lenses, and is also safer to wear overnight compared to soft contact lenses. 

Sleeping with contact lenses on is typically not recommended for hygiene reasons, but ortho-k is an exception. This is mainly because ortho-k lenses are removed during the day (instead of being left on the eye for many days) and disinfected regularly, which reduces the opportunity for infection to develop.

Lenses and their cases should never into contact with tap water. Organisms known as Acanthamoeba are often found in water (e.g. tap water, water storage tanks) and pose an increased risk to the eye compared to other micro-organisms. Acanthamoeba can cause serious eye infection to the cornea (Acanthamoeba keratitis), which can become sight-threatening if not treated.¹³

Ortho-k lenses can be considered one of the easiest types of contact lenses to wear. Being rigid, gas permeable lenses, this makes them easier to pick up and handle compared to floppier soft contact lenses, which do not hold their shape very well.

Ortho-k lenses are also smaller than most soft contact lenses, which can make them easier to apply to the eye. Their smaller size can make them a little harder to remove than soft lenses, but there are easily learned lens removal techniques to simplify this process.

Being worn overnight also offers advantages, because once applied the wearer closes their eyes and goes to sleep, which removes the problem of a lens falling out during the day.

Although ortho-k is most commonly prescribed to correct myopia (nearsightedness), it can also be used to correct hyperopia (farsightedness), astigmatism and presbyopia (age-related blurred vision at near).¹

The acceptable range of myopia correction using ortho-k includes strengths up to -4.50D with up to -1.50D of astigmatism. This is supported by medical approvals such as the USA Food and Drug Administration (FDA).¹ Higher myopia correction can be achieved;¹⁵ but the more correction that is needed, the lower the likelihood of achieving a successful outcome.

Ultimately, successful vision correction from ortho-k is depends on many individual factors. For these reasons, a prescription range should only be considered a guide. Consult an optometrist or eye doctor for personalized advice on you or your child's suitability for ortho-k.  

Read more about the benefits and suitability of ortho-k by age:

• Children
• Teenagers
• Young adults

The answer to this question depends on motivation, individual circumstances and cost.

Ortho-k offers great benefits for most lifestyles, and there are additional long-term benefits for children with myopia, as they are an effective form of childhood myopia treatment. However, motivation is needed to get through the first few weeks, as it typically takes more time to fit ortho-k compared to soft contact lenses and they are less comfortable over the first few times they are worn.

Once the new wearer has quickly adapted, though, research has indicated that some people who have experienced dry eye symptoms in soft contact lens wear can actually find ortho-k a more comfortable way to correct their vision - with their dry eye symptoms improving and these wearers preferring ortho-k.¹⁴

There is typically a higher upfront cost for ortho-k compared to daily wear contact lenses, because of the greater amount of consultation time that is generally required and higher individual lens cost. However, ortho-k lenses last longer than disposable contact lenses, causing the cost to likely balance out over time. How your optometrist or eye doctor charges for these costs varies depending on each clinic, and by country and region. 

Once cost is factored into your decision, the next consideration is your lifestyle. Ortho-k lenses are particularly suitable for active people who are inconvenienced by wearing contact lenses during the day, and in some cases can be a more comfortable option for those who find daytime contact lens wear uncomfortable.¹⁴ Parents may consider ortho-k safer and easier to manage for children, because all of the lens wear and cleaning happens at home.¹

To ensure correct fitting and that your or your child’s eyes are suitable, ortho-k lenses should only be purchased from a registered optometrist or eye doctor. Specialist equipment is needed to measure the eye to calculate the correct lens to use, and to assess its effects on the eye over time. The high degree of skill and complex work involved in designing a high-quality lens makes it is important for ortho-k consultations to be done in-person.

Depending on location, fitting fees and ongoing follow-up after care may be bundled with lens price, or charged separately, which can make it difficult to compare prices across different providers. Experience is probably the most important guide - an experienced ortho-k lens fitter may be willing to offer a suitability assessment before asking for commitment to purchase lenses. 

Find an ortho-k practitioner near you:

• US and Canada
• Europe
• Australia & NZ

1. Vincent SJ, Cho P, Chan KY, Fadel D, Ghorbani-Mojarrad N, González-Méijome JM, et al. CLEAR - orthokeratology. Cont Lens Anterior Eye. 2021 Apr;44(2):240–69.
2. Zhao F, Zhao G, Zhao Z. Investigation of the effect of orthokeratology lenses on quality of life and behaviors of children. Eye Contact Lens. 2018 Jun 25;44(5):335–8.
3. Si JK, Tang K, Bi HS, Guo DD, Guo JG, Wang XR. Orthokeratology for myopia control: a meta-analysis. Optom Vis Sci. 2015 Mar;92(3):252–7.
4. Sun Y, Xu F, Zhang T, Liu M, Wang D, Chen Y, et al. Orthokeratology to control myopia progression: a meta-analysis. PLoS One. 2015 Apr 9;10(4):e0124535.
5. Wu R, Stapleton F, Swarbrick HA. Residual corneal flattening after discontinuation of long-term orthokeratology lens wear in asian children. Eye Contact Lens. 2009 Nov;35(6):333–7.
6. Swarbrick HA, Wong G, O’Leary DJ. Corneal response to orthokeratology. Optom Vis Sci. 1998 Nov;75(11):791–9.
7. Alharbi A, Swarbrick HA. The effects of overnight orthokeratology lens wear on corneal thickness. Invest Ophthalmol Vis Sci. 2003 Jun;44(6):2518–23.
8. Brennan NA, Toubouti YM, Cheng X, Bullimore MA. Efficacy in myopia control. Prog Retin Eye Res. 2021 Jul;83(100923):100923.
9. Cho P, Cheung SW, Mountford J, White P. Good clinical practice in orthokeratology. Cont Lens Anterior Eye. 2008 Feb;31(1):17–28.
10. Bullimore MA, Sinnott LT, Jones-Jordan LA. The risk of microbial keratitis with overnight corneal reshaping lenses. Optom Vis Sci. 2013 Sep;90(9):937–44.
11. Bullimore MA, Mirsayafov DS, Khurai AR, Kononov LB, Asatrian SP, Shmakov AN, et al. Pediatric microbial keratitis with overnight orthokeratology in Russia. Eye Contact Lens. 2021 Jul 1;47(7):420–5.
12. Stapleton F, Keay L, Edwards K, Naduvilath T, Dart JKG, Brian G, et al. The incidence of contact lens-related microbial keratitis in Australia. Ophthalmology. 2008 Oct;115(10):1655–62.
13. Ibrahim YW, Boase DL, Cree IA. How could contact lens wearers be at risk of Acanthamoeba infection? A review. J Optom. 2009;2(2):60–6.
14. Charm J, Cho P. High myopia-partial reduction ortho-k: a 2-year randomized study. Optom Vis Sci. 2013 Jun;90(6):530–9.
15. Duong K, McGwin G Jr, Franklin QX, Cox J, Pucker AD. Treating uncomfortable contact lens wear with orthokeratology. Eye Contact Lens. 2021 Feb 1;47(2):74–80.