Intracorneal Ring Segments
Rings that tension and flatten the cornea in keratoconus: suitable patients, the procedure and realistic expectations.
Intracorneal ring (INTACS) surgery — rings placed within the cornea, the clear front layer of the eye — was developed to treat myopia. Since 2002, however, it has been used in keratoconus (a cornea that is thinner and more cone-shaped than normal). Because LASIK is already very effective for myopia, INTACS is now used only in keratoconus. In keratoconus, INTACS stretches the cornea from the sides like a hoop and flattens it to some degree.
Intracorneal rings are transparent half-rings made of a material called PMMA. Their inner diameter is 6.8 mm and their outer diameter 8.1 mm. Their thickness ranges from 0.25 mm to 0.45 mm in steps of 0.05 mm. They correct roughly −1.25 to −4.00 dioptres of refractive error.
When Intracorneal Rings Are Used in Keratoconus
- Mild to moderate keratoconus (corneal steepness should be limited to 55–57 D)
- A clear cornea (there should be no scarring)
- People who cannot wear contact lenses
- A corneal thickness of at least 450 microns where the INTACS will be placed
- People whose keratoconus has stopped progressing or is progressing very slowly
When Intracorneal Rings Cannot Be Used in Keratoconus
- Collagen tissue diseases
- Pregnant or breastfeeding women
- Corneal diseases (recurrent corneal erosion syndrome, dystrophies)
- Certain medications (Accutane, amiodarone, sumatriptan)
- Herpes simplex and herpes zoster infections of the eye
How Intracorneal Rings Are Placed
- The eye is numbed with drops.
- The channels in which the rings will sit are created either mechanically or with a femtosecond laser.
- The rings are inserted into the channels created in the cornea.
- A single stitch is placed where the rings enter the cornea.
- Antibiotic drops are put in the eye and the procedure is complete.
Whether the channels are created mechanically or with a femtosecond laser does not affect the visual results. There are also different approaches to the position and number of rings: one or two rings can be placed, and the entry point can be chosen in different positions. None of these approaches has been proven superior to the others.
Possible Complications of Intracorneal Rings
- The channels for the rings not being created properly
- The rings shifting out of position
- Infection of the eye
- Blood on the white of the eye (temporary; may last a few weeks)
- Blood vessels growing into the cornea
- Haloes around lights in patients with large pupils
Success Rate of Intracorneal Ring Treatment
Intracorneal rings do not stop the progression of keratoconus. After rings are placed in an eye with keratoconus, one should not expect the eye to be fully corrected or to see perfectly without glasses. After INTACS the steepness of the cornea decreases, the prescription falls, and vision with and without glasses improves — but this never means the prescription will fall to exactly zero. A contact lens can be worn on an eye with INTACS if desired.
Intracorneal Rings at a Glance
- Anaesthesia
- Anaesthetic drops or general anaesthesia
- Duration
- 15 minutes per eye
- Bandage
- The eye is not bandaged.
- After surgery
- There may be redness and mild stinging, which can last a few days.
- Vision
- From the next day, once the bandage is removed. The final level of vision is reached after one month, when the stitch is removed and glasses or a contact lens are fitted.
- Return to work
- The next day
- Stitch removal
- The single stitch is removed after one month.
- Eye check-ups
- The day after surgery, after 1 month and after 3 months. After the stitch is removed at one month, the glasses or contact lens prescription is determined.
- Eye drops
- For one month
Have your eyes assessed
Send your prescription history, previous eye reports and any corneal imaging for an individual assessment — in person in İstanbul or over video.
With every surgical or interventional procedure, results vary from person to person. Please obtain a detailed opinion from your doctor before any procedure.
This article is for general information only and does not replace a medical examination or personalised medical advice.