Intrastromal corneal ring segments

Intrastromal corneal ring segments (ICRS)are semi-circular (or crescent-shaped) implant rings made of polymethyl-methacrylate (plastic) which are inserted deep within the stroma of the peripheral cornea in selected keratoconus patients. The ICRS make the cornea more rounded at the place where they are implanted while flattening the central cornea.

This has the effect of refocusing the keratoconus, regularising the cornea and improving the corrected (with glasses or lenses) and non-corrected acuity of vision. The rings are inserted in tissue tunnels which are created either mechanically with a special knife or, better still and more accurately, with a Femtosecond laser.


  • Keratoconus patients who are no longer able to wear contact lenses.
  • Progressive keratoconus (after UV-CXL)
  • Pellucid marginal degeneration (after UV-CXL)
  • Post-Lasik ectasia (after UV-CXL)
  • Residual astigmatism after radial keratotomy
  • Residual astigmatism after penetrating keratoplasty (PKP)


  • Acute keratoconus with a keratometry > 70 diopters
  • Large central corneal opacity
  • Oedema
  • Severe allergies
  • Recurrent corneal erosion
  • Excessive patient expectations

The results of this technique are encouraging, but patients’expectations should also be realistic. The cornea is made more regular, vision is improved, but perfect acuity of vision will never be achieved.

More about Intrastromal corneal ring segments

Possible risks

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