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ICRS (Intracorneal Ring Segments) for Keratoconus


Intracorneal Ring Segments (ICRS) are small arc-shaped implants of varying thickness and length made of inert plastic which are implanted in a laser cut channel within the cornea. They act to provide a gross shape correction in Stage III (moderate to advanced) Keratoconus or Stage II (moderate) Keratoconus where vision is poor because of corneal shape asymmetry.

Different types of ICRS are available, but the best results in the treatment of Keratoconus have been published for Keraring ICRS in combination with femtosecond laser implantation. Kerarings are implanted closer to the centre of the cornea than older ICRS designs. This creates more flattening effect and adds a margin of safety compared with larger diameter ICRS. We use Keraring ICRS in conjunction with femtosecond laser implantation and accurate 3D corneal shape mapping to optimise results.

ICRS implantation is a day case procedure performed under local anaesthetic, using drops to numb the eye. The procedure takes about 30 minutes and is painless, but some discomfort (like a grain of sand in the eye) is normal in the first 24 hours after surgery. We would recommend taking two days off work.


Risks and benefits of ICRS implantation

  • ICRS implantation is safe but efficacy is highly variable. About 2/3 of patients achieve significant gains in spectacle Corrected Distance Visual Acuity (CDVA). Although many patients experience a marked visual improvement, in some cases there is no subjective or objective improvement in vision.
  • ICRS is the main alternative to corneal transplantation for patients with moderate to advanced Keratoconus and problems with hard contact lens wear. ICRS implantation should not affect the chance of a successful corneal transplant if this becomes necessary subsequently.
  • Further surgery may be necessary after ICRS implantation (approximately 1 patient in 50). This can include repositioning or removal of the implants.
  • Infection is unusual after ICRS implantation but can occur (in less than 1% of patients). It may result in the need for the implant to be removed and may cause some permanent scarring in the area of the ring channel. This damaged block of tissue would normally be removed completely in any subsequent corneal transplantation procedure.  
  • ICRS can be combined with other procedures to stabilise corneal shape and improve vision in Keratoconus. Corneal shape is normally stable by three months after ICRS implantation. At that stage, Corneal Collagen Cross-linking is often performed to ‘lock-in’ longer-term corneal shape stability. After a further period of monitoring (typically 2 years) to ensure corneal shape stability has been achieved, other procedures including ICL implantation and laser treatments can be used to improve vision further.
  • Keraring ICRS have a good long-term safety record. Over 100,000 patients have had keraring implants over the last 18 years.

If you wish to arrange a preliminary consultation, please telephone 020 7566 2156 or 07484 081815 (or from outside the UK +44 (0)20 7566 2156 or +44 7484 081815) or email