Corneal ring implantation is a surgical technique that involves installing a plastic ring into the middle layer of the cornea, the transparent front section of the eye, to correct vision. The cornea acts as a windscreen by protecting the inner eye structures from germs and debris. It's also the primary focusing structure of the eye responsible for directing over 70 per cent of light to the retina, the spot at the inner back wall layer of the eye that recognizes light and images. Distortion or damage to the shape of the cornea affects its focusing power leading to poor eyesight.

The procedure can treat poor vision due to certain corneal disorders, including nearsightedness, keratoconus, pellucid marginal degeneration and corneal swelling, after laser in situ keratomileusis (LASIK) and radial keratotomy surgery. The corneal inserts are made of a biocompatible material, so the patient doesn't feel them and other people won't see them. The technique is also completely reversible, and patients can have the corneal implants removed if their vision changes or aren't satisfied with the results.

Also Known As

  • ICRS
  • Corneal insert
  • Corneal implant
  • Intrastromal corneal ring
  • Intrastromal corneal ring segment


Before the Procedure 

The eye surgeon will take the detailed medical and surgical history of the patient. It is critical for the patient to disclose all the medications they use, including prescription drugs, over the counter medicines and dietary supplements. Some substances can increase the risk of surgical complications, so the surgeon will advise the patient on whether to stop using any of the medications before the operation. S/he will also conduct a complete eye examination, including corneal topography/tomography, i.e., computerized mapping of the cornea.

The surgeon will provide instructions on how to prepare for the procedure. For example, the patient may be asked not to eat solid food at least 12 hours ahead of the surgery. The patient should also come with someone or make arrangements to be taken home after the procedure.


Corneal inserts work by flattening and reshaping the cornea, which helps to focus light rays on the retina, improving the patient's vision.

ICRS implantation is an outpatient treatment performed in the eye surgeon's office or an outpatient surgery center. The technician will measure the patient's eye pressure before the procedure as a safety measure. The patient will be given medication to help them relax as well as anesthetic eye drops and injections to numb the eye.

The procedure may vary somewhat, but in general, the surgeon will make small cuts in the outer margin of the cornea. S/he will then make tunnels under the corneal outer layer and insert the parts of the plastic ring into the tunnels. S/he will stitch up the cuts, apply an antibiotic ointment to help prevent infection, patch the eye and cover it. It's a quick procedure that takes about 15 minutes per eye. In most cases, only one eye is treated in a single procedure.

Risks & Complications

Advances in laser technology have made ICRS implantation safer. There are rare risks, including:

  • Infection
  • Inflammation
  • Reduced vision
  • Chronic eye pain
  • Halos or glare at night
  • Swelling of the cornea
  • Perforation of the eye
  • Lights appearing too bright (glare)
  • Seeing rings (halos) around lights at night

In some cases, the patient may report a mild headache because of the medication administered before the operation. The patient may experience some redness, soreness, blurred vision and increased sensitivity to light for some hours following the procedure.

Complications associated with the procedure are sporadic and include movement of the ring, dislodgement of the ring, secondary vision disorder and need for an adjustment surgery.

After Care & Recovery

The surgeon will prescribe eye drop medication to prevent infection and give aftercare instructions. The patient must wear the eye patch as directed to prevent the movement and dislodgement of the corneal ring. The surgeon will see the patient the day after the surgery to assess the outcome. The patient should report any pain, swelling, decreased vision or increased eye redness.

The recovery usually takes a day or two, during which time the patient must avoid certain activities as directed by the doctor. These include not rubbing the eyes, preventing water from getting into the eye and avoiding activities like yoga, strenuous tasks, heavy lifting, bending, sports, high-impact exercise, etc. It's also wise to avoid activities that can expose the eye to dust and other contaminants that can lead to infection.


Close to 100 per cent of the patients meet the requirements for driving without corrective lenses after the surgery, and over half of them achieve 20/20 vision or better. Therefore, some patients may no longer need to wear corrective lenses while others may still need lenses, even though their eyesight will have improved overall.