Orthokeratology: night lenses against myopia

In the evening, before going to sleep, a ten-year-old girl places two small rigid lenses on her eyes. In the morning she takes them out, and all day she sees the blackboard sharply without wearing anything on her eyes. It is not a trick: night contact lenses, which specialists call orthokeratology, reshape the form of the cornea for a few hours.

Today they are prescribed mainly to children, with an added aim: to slow the myopia that increases during growth¹. Here is what the studies say about the effect and the risks.

In this article

1. How night contact lenses work
2. How much they slow myopia in children
3. After treatment ends
4. The risk of infection: what studies say
5. Who may be a candidate
6. Frequently asked questions
7. Sources

How night contact lenses work

Orthokeratology lenses are rigid gas-permeable lenses, with a geometry designed to reshape the cornea^1,8. During sleep they flatten the centre of the cornea: on waking, myopia is reduced for some hours, and the wearer can see well during the day¹. It is a temporary effect: to maintain it the lenses must be worn regularly.

The second effect, the one on the growth of the eye, has to do with the periphery. Myopia in children increases mainly because the eye lengthens. According to the most studied hypothesis, the reshaped cornea changes the way light reaches the edges of the retina, creating a blur that would restrain the stimulus to lengthen; the exact mechanism, however, is not yet known². The other lenses and glasses that exploit the same principle are described in the article on lenses and glasses to slow myopia.

Ordinary rigid lenses, worn by day, do not give this result: in the 2023 Cochrane review they showed no differences compared with the control groups³. What seems to count is the design that reshapes the cornea, not the material.

How much they slow myopia in children

The 2023 Cochrane review pooled 64 randomised trials with 11,617 children aged 4 to 18. In the control groups the eye lengthened on average by 0.31 millimetres in a year and by 0.56 in two; with orthokeratology the lengthening was less by 0.19 millimetres at one year and by 0.28 at two³. A report by the American Academy of Ophthalmology, based on 13 studies, translates these numbers in an intuitive way: in two years about 0.3 millimetres of lengthening instead of 0.6, equal to a difference of about half a dioptre⁵.

Two details recur in several studies. The first is age: the effect seems greater in younger children, and the Academy’s report points in particular to those who start between 6 and 8^4,5. The second is combination with low-dose atropine eye drops. In a randomised trial on 164 children aged 8 to 12, orthokeratology together with 0.01% atropine slowed lengthening more than either treatment alone; in children aged 8 to 10, however, the difference compared with the lenses alone was not significant⁶. We discuss atropine in the article on low-dose atropine.

The limitations are those of all research on myopia. In the Cochrane review 61% of the studies came from China or other Asian countries, the duration ranged from one to three years and the certainty of the evidence from very low to moderate³. Studies on European children are few, although a 2020 review reports that in Europe one lens model has obtained specific authorisation for myopia control¹.

After treatment ends

When a child no longer wears the lenses, the cornea returns to its previous shape, and with it the myopia¹. What happens to the growth of the eye is more uncertain. According to a 2024 meta-analysis, after orthokeratology ended the eye lengthened by 0.10 millimetres more than in those who continued the lenses⁷, and the Academy’s report speaks of a possible rebound⁵. The Cochrane review, however, judges the evidence on this point inconclusive³. We do not yet know what the ideal duration of treatment is⁷.

The risk of infection: what studies say

Wearing contact lenses during sleep increases the risk of microbial keratitis, an infection of the cornea that, in severe cases, can leave permanent damage to vision^5,10. It is the point on which the studies are most cautious.

• A 2016 systematic review, of 170 publications, concluded that the risk with orthokeratology is similar to that of other lenses worn at night; the most common complication was small superficial lesions of the cornea, and no long-term effects were found on its innermost layer⁸.
• A working group of American experts, in 2021, observed that night lenses for orthokeratology might increase the risk of infection in children, in particular from Acanthamoeba, an amoeba that lives in water, and that failure to follow the rules of use remains an important risk factor¹⁰.
• The 2024 meta-analysis found adverse events up to about four times more frequent than with traditional contact lenses, but with evidence that is still fragile⁷.

The risk linked to water is described in the article on contact lenses, showering and swimming pools.

Who may be a candidate

In the ROMIO study, for example, the children had myopia between 0.50 and 4 dioptres and limited astigmatism⁴. According to the Academy’s report, the effect may be greater in the youngest and in those with larger-than-average pupils⁵. In many countries the lenses are authorised to temporarily reduce myopia, and are prescribed mainly, but not only, to children¹.

Consistency matters a great deal: the review on safety indicates as conditions for a good result correct application, cleaning rules followed rigorously, regular check-ups and prompt treatment of complications⁸. It is a daily commitment for the whole family, and costs and reimbursement vary greatly from one European country to another.

Frequently asked questions

Does orthokeratology make myopia go away?

No. It corrects myopia for some hours by reshaping the cornea, but the effect fades when the lenses are no longer worn¹. In children it can slow the increase in myopia while treatment continues^3,7.

From what age can night contact lenses be used?

The studies have involved children as young as 6, and the effect seems greater in those who start between 6 and 8^4,5. The decision is made with the ophthalmologist, also taking into account the daily commitment the lenses require⁸.

Are night contact lenses dangerous?

The main risk is an infection of the cornea, rare but potentially serious⁵. How much higher it is than with other lenses is uncertain: one review finds it similar to that of other lenses worn at night⁸, another finds adverse events more frequent than with traditional lenses, with fragile evidence⁷. On the importance of hygiene and check-ups the sources agree^8,10.

Night contact lenses are among the tools with a measured effect on the growth of myopia in children^3,5. Their value, however, lies in the balance between a benefit measured in tenths of a millimetre and a rare but serious risk, which depends greatly on how the lenses are used and checked^8,9.