Intacs Intracorneal Ring Segments


The intracorneal ring segments (ICRS) are a type of corneal implant used for correcting refractive errors, and specifically for low myopia, which due to higher costs is used much less frequently than LASIK and laser procedures. Perhaps the most important use of intracorneal ring segments is for patients with mild to moderate keratoconus with clear and thick enough corneas. In patients with keratoconus, the cornea is not naturally aspirated; therefore, performing LASIK or laser procedures in order to correct refractive errors is forbidden for these patients, but intracorneal ring segments can improve vision with or without glasses in these patients and reduce the severity of the disease.Tehran Noor Eye Hospital was the first ophthalmic center in Iran to provide this type of medical services.


The implantation of intracorneal ring segments is an outpatient procedure performed in two steps, using local anesthetic eye drops. In the first stage, using the appropriate instruments, a radial incision is made in the peripheral cornea, through which two concentric semi-circular tunnels are created in the cornea. Then in the second step, the ring segments with the calculated thickness are implanted in these tunnels. After the surgery, eye drops are prescribed for one to several weeks. In the first few days after the surgery, the eye is sensitive to light, and it's recommended to use sunglasses. Postoperative restrictions only include touching and rubbing the cornea and heavy physical activities in the first 4 to 6 weeks after the surgery.

It should be noted that these ring segments are made of a special plastic called PMMA which is compatible with the cornea. Interestingly, the material has been used to make intraocular lenses in the past 50 years and is fully compatible with the eye tissue, so it does not cause inflammation.

In Tehran-Iran Noor Eye Hospital, during the surgical procedure of orneal ring implantation two rings are usually placed on the two sides of the cornea. Each ring is a 150° arc and 0.8 millimeters in width. Correcting refractive errors in the patient depends on the thickness of the segments, varying from 0.25 to 0.45 mm.

This technique is not applicable for patients with myopia greater than one diopter. However, it is effective in patients with keratoconus who usually suffer from astigmatism as well.


The main three advantages of Intracorneal Ring Segments are as follows:

1. High accuracy in correcting myopia, at least equal to that of LASIK surgery. According to the FDA (Food and Drug Administration) study, the postoperative outcomes have been observed: in 55% of the patients visual acuity was improved more than 16/20 after 2 years, in 75% of the patients more than 20/20, in 91% of the patients more than 25/20 and in 95% of the patients visual acuity was improved more than 40/20.

2. No tissue changes in the central cornea and maintaining the normal corneal shape

3. The ability to revert to preoperative status in case of removing intracorneal ring segments.

Note: In ICRS implantation, there is no need for complicated microkeratome and laser technologies such as those used in LASIK, and in this regard, it is considered as a special treatment in the developing countries.

Note: The results of the surgery are different in patients with keratoconus and myopia. Implanting ring segments improves visual acuity by two lines on average in 50% of patients, although some patients may achieve more improvement. In fact, in patients with keratoconus who don’t have a good vision with glasses before the surgery, ICRS implantation reduces corneal irregularities that along with new prescription eyeglasses results in a better vision.


Limitations of ICRS Implantation

The only present problem with the implantation of intracorneal ring segments is its limited range of patients who are proper candidates for this procedure. In other words, patients with myopia from -1 to -4.5 diopters and a maximum astigmatism of 1 diopter can be treated with this technique.

Other Uses of ICRS Implantation are as follows:

-The correction of residual refractive errors after LASIK

-The correction of keratoconus More guides and complete information are provided for patients by the eye care team of Tehran Noor Eye Hospital in Iran.


Patients with insulin-dependent diabetes, connective tissue diseases, autoimmune or immunodeficiency diseases as well as pregnant or breastfeeding women, patients with recurrent corneal erosion or corneal dystrophies, and those taking medications such as Accutane (for curing acnes), amiodarone (for heart disease) and sumatriptan (for treatment of migraines) are the subjects of contraindications to intracorneal ring segments implantation. Inform your ophthalmologist before the surgery in case of taking any medications.


Although the surgical procedure of ICRS has been approved by FDA, it should be noted that similar to other refractive surgical procedures, there might be some complications as a result:

-Postoperative infections: 0.2%

-An increased astigmatism, hypo or hyper-correction: 3.7%

-Corneal neovascularization: 1.2%

-Halos and glares especially at night: 1-3%

-Light sensitivity: less than 1%

-Night vision difficulty: 4.3%

-Keratic precipitates around the ring: usually asymptomatic

Note: No vision threatening complications have been observed within the one-year follow-up period after ICRS implantation.

How long does the surgical procedure of intraocular ring implantation take?

Is the surgical procedure of intracorneal ring implantation painful?

Can the surgery be performed on both eyes simultaneously?

What are the postoperative limitations ?

Can you expect a best-corrected vision after refractive surgical procedures?

Can the patients keep doing their sports activities after intracorneal ring implantation?




-How long does the surgical procedure of intraocular ring implantation take?

This procedure takes around 15 minutes for each eye.


-Is the surgical procedure of intracorneal ring implantation painful?

No. Using local anesthetic drops, the surgery is painless. However, burning eyes, foreign body sensation and watery eyes are expected in the first hours and days after the surgery which can be controlled by taking prescribed medications.


-Can the surgery be performed on both eyes simultaneously?

Yes, the studies have shown that the risk of developing postoperative complications in the surgical procedure that is performing simultaneously on both eyes is not higher than the surgical procedure that is performing just on one eye.


-What are the postoperative limitations ?

The patient should avoid rubbing the eye in the first 6 months after surgery. During the first several weeks after surgery, care should be taken regarding the eye’s health and protecting it against impacts and infections. Eye shields should be worn while sleeping. The patients should not wear makeup at least for one week and has to keep materials like spray or shampoo out of their eyes for several weeks. Contact lenses should not be worn in the first few weeks, either.


-Can you expect a best-corrected vision after refractive surgical procedures?

In most refractive surgical procedures, 100% correction and 20/20 normal vision without wearing glasses cannot be expected. So, if you have such expectations, do not undergo this surgery. Do not expect a vision better than your current glasses or lenses could provide. You should know that if your glasses or lens prescriptions are determined correctly, there would be a very low chance that your vision improves after the surgery. If you have amblyopia (lazy eye), you should not expect to be treated using these methods.


-Can the patients keep doing their sports activities after intracorneal ring implantation?

Moderate sports activities such as running, walking, or common exercise don’t cause any problems, but lifting objects heavier than 7.5kg should be avoided.