CAIRS (corneal allogenic intrastromal ring segments) is a keratoconus procedure that implants thin, curved segments of sterilised human donor cornea into a laser-created channel in your own cornea. The segments gently flatten the steep, cone-shaped area, improving the corneal shape so glasses and contact lenses fit and work better — and helping stabilise progressive keratoconus. Because the implants are natural corneal tissue rather than plastic, they integrate biologically and avoid the thinning, erosion and extrusion sometimes seen with synthetic rings. At our partner clinics in London and South England, CAIRS starts from £3,500 per eye and is frequently combined with corneal cross-linking in the same setting.
What is CAIRS and KeraNatural?
Keratoconus is a progressive condition in which the normally dome-shaped cornea thins and bulges into an irregular cone. This distorts vision, drives up short-sightedness and astigmatism, and eventually makes spectacles and standard contact lenses unable to give clear sight. CAIRS reshapes the cornea from within: arc-shaped segments are placed in the mid-cornea to redistribute tension and pull the cone flatter and more central.
KeraNatural is the leading brand of pre-cut, sterilised allograft (donor) corneal ring segment, processed from screened human corneal tissue. Unlike the rigid plastic (PMMA) segments used in traditional Intacs surgery, KeraNatural rings are living-tissue-derived, fully transparent and biocompatible — so the eye accepts them without the foreign-body complications that can affect synthetic implants.
Who is CAIRS suitable for?
- Progressive or established keratoconus where vision is no longer adequately corrected by glasses
- Patients intolerant of rigid or scleral contact lenses, or wanting to reduce dependence on them
- Corneas too thin or too steep for some synthetic ring designs
- Those wishing to delay or avoid a corneal transplant (DALK or full graft)
- Often performed alongside cross-linking to both reshape and stabilise the cornea
CAIRS does not cure keratoconus, but by improving corneal shape it can sharpen vision, improve contact-lens tolerance, and is a tissue-additive step that keeps future options — including transplant — fully open.
Not sure if CAIRS is right for your cornea? A corneal assessment with tomography scans confirms your keratoconus stage and whether ring segments will help.
Book a corneal assessmentCAIRS vs synthetic rings vs combined treatment
Corneal ring segments come in two families — donor-tissue (CAIRS/KeraNatural) and synthetic plastic (Intacs). Your surgeon will recommend the right approach based on your corneal thickness, cone location and whether your keratoconus is still progressing.
Related corneal-tissue options your surgeon may discuss include CTAK corneal tissue addition, Bowman layer transplant and, for advanced disease, DALK partial-thickness transplant.
What happens during CAIRS surgery
CAIRS is a day-case procedure performed under local anaesthetic eye drops. You stay awake and feel no pain — only light and gentle pressure. Each eye takes around 20–30 minutes.
- Numbing drops are applied and your eye is cleaned and held gently open.
- A femtosecond laser creates a precise circular channel within the middle layer (stroma) of your cornea — no blade is used.
- The pre-cut KeraNatural donor segments are placed into the channel at the depth and position planned from your scans.
- The segments immediately begin to redistribute corneal tension, flattening the cone and improving symmetry.
- If indicated, cross-linking is performed in the same session to lock in stability. A protective contact lens may be placed and you rest before going home.
Recovery week-by-week
Comfort returns quickly because the corneal surface is barely disturbed. Vision settles gradually as the cornea adapts to its new shape.
Day of surgery
Mild grittiness, watering and light sensitivity. A bandage contact lens may be in place. Rest the eye; no rubbing. Drops begin.
Days 1–7
Discomfort fades over the first few days. First review checks the segments are well positioned. Vision may fluctuate.
Weeks 2–6
The cornea stabilises into its new shape. Vision steadily improves. Most return to work and screen use within days.
Months 1–3
Refraction settles. Updated glasses or a new contact-lens fitting — often a better, flatter fit than before surgery.
Long term
With cross-linking, keratoconus is typically stabilised. Annual corneal monitoring confirms the cornea stays stable.
Cost & insurance
Our CAIRS pricing is all-inclusive: consultant assessment, corneal tomography and planning, the sterilised KeraNatural segments, femtosecond laser, the procedure, post-op drops and your review appointments.
- Self-pay: from £3,500 per eye for CAIRS; from £4,900 per eye when combined with cross-linking.
- Insurance: keratoconus ring surgery is covered by many insurers where medically indicated — we help with authorisation.
- Finance: 0% options available to spread the cost.
Compare keratoconus pathways on our prices hub, or explore every corneal treatment on the treatments hub. If you already wear specialist lenses, ask about scleral lens fitting after surgery.