CAIRS — corneal allogenic intrastromal ring segments — replaces synthetic implants with segments prepared from donor cornea. Biocompatible, removable, and shaped to each individual cone.
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In keratoconus the cornea thins and bulges forward into a cone, scattering light instead of focusing it. For two decades the standard way to reshape such a cornea was to implant thin arcs of PMMA plastic within the stroma. They work — but as a permanent foreign body they can extrude, migrate, thin the tissue above them and cause glare.
CAIRS uses arc-shaped segments cut from human donor cornea instead. The tissue is placed in a femtosecond-laser channel, flattening the cone and pulling the optical centre back toward the visual axis. Because it is corneal tissue rather than plastic, it integrates biologically, does not extrude, and can be removed or exchanged if needed.
A meta-analysis pooling 442 eyes reported a 0.37 logMAR gain in corrected acuity, a 4.49 D reduction in maximum keratometry, and a single severe adverse event across the entire series.
CAIRS surgery for keratoconus: what it is, who it suits and who it does not →
Keratoconus treatment today follows three steps, and they are not interchangeable. This distinction matters more than any single technique:
Corneal cross-linking halts progression. It preserves the vision not yet lost — but does not restore vision already gone.
CAIRS, ring segments, topography-guided ablation or a phakic lens correct the geometry and restore clarity. These do not halt progression.
Lamellar or full-thickness keratoplasty — only where the cornea has scarred, thinned excessively, or previous surgery has failed.
Transplantation is no longer the first step; it is the third.
Our study, "Corneal Allogenic Intrastromal Ring Segments (CAIRS) in Keratoconus: Interim Multi-Surgeon Outcomes", will be presented as an oral presentation at the KCXL International Experts' Meeting in Zurich, 26–28 November 2026. It reports the interim results of a joint series by four surgeons.
Authors: Serkan Güreser, MD; Cemil Orkun Cemiloğlu, MD; İrfan Durukan, MD; Özcan Ulaş Açıkgöz, MD.
CAIRS remains a technique practised by a relatively small number of surgeons worldwide. If you are an ophthalmologist considering it for a patient, or would like to discuss segment planning, cone morphology and channel parameters, you are welcome to get in touch.
Clinical writing, with references, is published in the blog.
Diagnosis and staging of keratoconus rest on corneal tomography and detailed examination. Consultations are held in Sincan, Ankara.
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