Written and maintained by CASRAI Editorial Board
Last updated
General information for clinic, lab and supply staff and researchers. It is not medical advice and does not describe how to fit or insert lenses; eye-care decisions belong to an eye-care professional.
Short answer
Orthokeratology (ortho-k) is the use of specially designed and fitted contact lenses to temporarily reshape the cornea so that vision improves, according to the American Academy of Ophthalmology (AAO). The lenses flatten the center of the cornea and are usually worn overnight. The effect lasts only while the lenses keep being worn. In US regulation, the rigid gas permeable lens definition in 21 CFR 886.5916 is the relevant device text.
Definition and scope
AAO describes ortho-k as temporary reshaping of the cornea with specially designed lenses, aimed mainly at near-sightedness (myopia). Search results also use the names ortho k lenses, ortho-k and corneal reshaping for the same practice. The lenses are removed during the day.
Ortho-k is a different thing from refractive surgery. AAO notes that if lenses stop being worn, the eyes eventually return to their original shape and the refractive error returns, so the change is not permanent.
How ortho-k lenses are used in practice
AAO describes the lenses as flattening the center of the cornea, which changes how light bends as it enters the eye; most are worn overnight and removed during the day. The eye-care professional first maps the cornea with corneal topography, which AAO describes as a painless test that shows the shape and curves of the cornea. Fitting steps and wear schedules are set by the prescriber and the manufacturer’s instructions for use, and are outside the scope of this page.
Related concepts
Rigid gas permeable (RGP) lenses
Ortho-k lenses are generally rigid gas permeable (RGP) lenses used for a reshaping purpose. For how RGP differs from soft lens materials, see contact lens materials and the explainer on hydrogels.
Daily-wear and replacement-schedule lenses
Soft lenses used for vision correction follow replacement schedules covered in daily vs monthly contact lenses. That comparison does not cover ortho-k.
Myopia control
Whether ortho-k slows myopia progression in children is a separate question from whether it corrects vision. AAO states there is no firm evidence that ortho-k can slow the progression of myopia in children, while noting it is being studied (AAO, checked 2026-10-30).
Where it matters for labs, clinics and supply decisions
How the US regulation frames the lens
The eCFR text of 21 CFR 886.5916 (checked 2026-10-30) defines a rigid gas permeable contact lens as a device worn directly on the cornea to correct vision, made from materials whose polymer molecules generally do not absorb or attract water, such as cellulose acetate butyrate, polyacrylate-silicone and silicone elastomers. The regulation classifies these lenses as Class II when for daily wear only and Class III when for extended wear.
| Lens wear category in 21 CFR 886.5916 | Device class |
|---|---|
| Daily wear only | Class II |
| Extended wear | Class III |
This table reproduces the regulation text for RGP lenses. It does not assign any particular class to an individual ortho-k product. A brand’s own regulatory status is recorded in that product’s FDA entry, so a general statement about ortho-k as a practice does not stand in for it.
What the practice involves, as a supply checklist
- Corneal mapping equipment. AAO describes a corneal topography map of the cornea’s shape and curves as part of the evaluation.
- Equipment context. For the wider list of clinic equipment, see the ophthalmology surgery center supply checklist.
- The lenses themselves. AllAboutVision describes lenses that are either held in the practice’s inventory or custom ordered, and says up to three pairs of temporary lenses may be needed while the final design is settled.
- Lens hygiene supplies. The CDC states that failure to wear, clean and store contact lenses as directed can increase the risk of eye infections such as microbial keratitis, and that the majority of wearers do not practice proper contact lens hygiene. See contact lens case replacement for the CDC interval and the evidence behind it.
Common misunderstandings
- “It permanently fixes vision.” AAO says the cornea returns to its original shape and the refractive error returns if lenses are no longer worn.
- “Overnight lenses are lower risk because they are worn asleep.” AAO says ortho-k is associated with an increased risk of infection, a concern it highlights especially for children and adolescents, and that infections can cause lifelong vision impairment.
- “Ortho-k is proven to stop myopia progression.” AAO states there is no firm evidence of this; it is being studied.
- “Any FDA-regulated lens is an approved ortho-k lens.” The CFR section covers the RGP lens device type. It does not by itself establish the status of a given brand.
FAQ
What is orthokeratology?
It is the use of specially designed and fitted contact lenses to temporarily reshape the cornea to improve vision (AAO).
What are ortho k lenses?
They are the rigid gas permeable lenses used for orthokeratology. AAO says they flatten the center of the cornea and are mostly worn overnight.
Is the effect permanent?
No. AAO says the eyes eventually go back to their original shape and the refractive error returns if the lenses are not worn.
What infection risk does the CDC describe for contact lenses in general?
The CDC says improper wear, cleaning and storage can increase the risk of eye infections such as microbial keratitis, and that serious infections such as Acanthamoeba and fungal keratitis can result in vision loss or blindness.
Sources
- American Academy of Ophthalmology, What Is Orthokeratology?, checked 2026-10-30.
- eCFR, 21 CFR 886.5916, Rigid gas permeable contact lens, checked 2026-10-30.
- CDC, About Contact Lenses, checked 2026-10-30.
- AllAboutVision, Orthokeratology, consumer eye-health site, checked 2026-10-30 (used only for the lens-inventory and temporary-lens description).
