What Do Ortho-K Lenses Do to Your Eyes While You Sleep?

Ordinary lenses go in during the day and come out at night. You have probably been told many times not to sleep in your lenses.

Yet there are lenses that work the other way round: you put them in at night and take them out in the morning. Their proper name is orthokeratology lenses (ortho-k). In Korea they are often called "dream lenses".

It is the cornea, not the lens, that corrects your vision

The American Academy of Ophthalmology (AAO) explains that ortho-k lenses flatten the center of the cornea, changing how light is bent as it enters the eye. The treatment is often compared to dental braces.

Ortho-k lenses are not soft lenses but rigid gas permeable (RGP) lenses that let oxygen through. They need to be rigid to give the cornea a consistent shape.

The cornea changes shape while you sleep, and it keeps that shape for a while after you take the lenses out in the morning. That lets you go through the day without glasses or lenses.

The effect is not permanent

The AAO explains that when you stop wearing ortho-k lenses, the cornea slowly goes back to its normal shape and the myopia comes back. To keep the effect, you have to keep wearing them every night.

It is not a one-time fix like refractive surgery. It means a continuing routine of putting in and caring for lenses every night.

In the US, overnight wear was approved in 2002

On June 13, 2002, the US Food and Drug Administration (FDA) approved one manufacturer's corneal refractive therapy lenses for overnight wear. The approval states the use as temporary reduction of myopia of up to 6.00 diopters in eyes with astigmatism of up to 1.75 diopters. It also states that continued overnight wear is needed to maintain the effect.

The AAO also notes that ortho-k is mainly used for myopia and works best for mild to moderate prescriptions. Whether it suits you depends on your prescription and the shape of your cornea, so an examination before fitting is essential.

Does it slow myopia in children?

This is the biggest reason ortho-k gets attention today. Why myopia is rising is covered in the previous article.

In an assessment published in 2019, the AAO reviewed 13 studies. Most were done in people of Asian ethnicity.

• Over two years, ortho-k reduced the lengthening of the eye by about 50% (about 0.3 mm in the ortho-k groups against about 0.6 mm in the control groups).
• That corresponds to a difference of about 0.5 diopters in prescription.
• The effect may be greater when started early, at ages 6 to 8.
• After stopping, or switching to another form of correction, rebound can occur.

The report concluded that ortho-k may be effective in slowing myopia progression in children and adolescents. In the same sentence it added that safety remains a concern.

The biggest risk is infection

With ortho-k you sleep in lenses. Why sleeping in lenses is risky is covered in It Was Only a Nap: Six People Who Slept in Their Contact Lenses.

A safety report the AAO published in 2008 found that more than 100 cases of infectious keratitis in ortho-k users had been described in case reports. Bacteria and Acanthamoeba were the causes. The data available then could not show how often complications occur, and the report advised building a wide margin of safety into ortho-k regimens.

The AAO explains that the infection risk is especially concerning for children and adolescents, because it is hard for children to keep up good hygiene on their own.

If you are considering ortho-k

1. Get examined to see whether it suits you. It depends on your prescription and corneal shape.
2. Don't skip follow-up visits. The AAO says regular eye exams are needed.
3. Keep lens and case hygiene strict. Keep water away from your lenses.
4. For a child, parents should share in the care.
5. Check the cost in advance. The AAO says that in the US it costs $1,000 to $4,000 to start and $300 to $500 a year afterwards. It differs by country.

If your eye hurts or is red, or you can't see well after taking the lenses out in the morning, don't put them back in that night; see an eye doctor.

References

• American Academy of Ophthalmology (AAO), What Is Orthokeratology?
• American Academy of Ophthalmology (AAO), Myopia Control in Children
• VanderVeen DK et al., Use of Orthokeratology for the Prevention of Myopic Progression in Children: A Report by the American Academy of Ophthalmology, Ophthalmology 2019
• Van Meter WS et al., Safety of Overnight Orthokeratology for Myopia: A Report by the American Academy of Ophthalmology, Ophthalmology 2008
• US Food and Drug Administration (FDA), Premarket Approval P870024/S043

This article is general information and does not recommend any product or treatment. Follow the examination and instructions of an eye care professional for ortho-k fitting and care.