Intracorneal ring segment implantation

Intracorneal ring segment (ICRS) implantation is a minimally invasive eye surgery that involves the implantation of a medical device into the cornea to alter its shape and improve vision.

Cornea is the strong, transparent, outermost tissue of the eye. Apart from protecting the eye from dust, germs, and other foreign substances, it plays an important role in vision. Cornea acts like a window that controls the light entering the eye. When light rays reflecting from an object reach the cornea, it bends the light and focuses it onto the eye’s natural lens. The lens then projects the light onto the retina that converts this light into impulses, which are moved to the brain through the optic nerve. Therefore, the refractive function of the cornea is essential for vision.

However, in certain eye conditions such as keratoconus, cornea loses its natural shape and becomes thinner and steeper, resulting in progressive vision loss. Although the condition can be initially treated with contact lenses or glasses, it may worsen with time, requiring the individual to undergo corneal transplantation.

Intracorneal ring segment implant provides an alternative to corneal transplantation. The surgery includes placing two small, crescent-shaped plastic rings into the cornea to restore its natural shape.

ICRS implantation is better than corneal transplantation because the rings can be easily removed if any complications arise.

The surgery does not treat keratoconus and, therefore, it is generally combined with another procedure called corneal collagen crosslinking to make the cornea stable.

This surgery is indicated to treat the following conditions:

• Keratoconus associated astigmatism and myopia (nearsightedness): Symptoms of keratoconus include:
  • Distortion of vision
  • Blurring
  • Sensitivity to light and irritation
  • Glare
  • Frequent change in prescription of contact lens or glasses
• Mild myopia: Symptoms of myopia include:
  • Headaches
  • Eyestrain
  • Difficulty seeing distant objects
  • Need to squint to see clearly
• Pellucid marginal degeneration: This condition does not usually present with any symptoms; however, individuals experience a gradual reduction in vision that does not resolve with glasses.
• Weakening of cornea after LASIK surgery

Eye surgeons do not perform this procedure in individuals who are below 21 years of age and have:

• Vision correctable with contact lens
• Unclear central cornea
• Corneal thickness less than that required (450 microns)
• Corneal hydrops (corneal opacification due to oedema)
• Advanced keratectasia grade IV (abnormal bulging of cornea)
• Herpetic keratitis (viral infection of eye caused due to herpes virus)
• Vascular, collagen, and autoimmune disease

Your doctor will perform a routine eye examination to observe changes in your cornea, the eye’s inability to focus light on the retina, and other signs of keratoconus. In addition, you will be asked to undergo specific tests, including:

• Corneal topography: It looks for irregularities in the cornea by creating a computerised photograph of the eye.
• Ultrasound pachymetry: This measures corneal thickness. 

The eye surgeon will give you the following instructions to prepare for the surgery:

• Share a list of all the medications that you take, including over-the-counter medicines, herbs, vitamins, and supplements.
• You will be asked to discontinue blood-thinning medications such as warfarin, apixaban, or rivaroxaban a few days prior to the surgery.
• Ask a family member, friend, or responsible adult to drive you home following the procedure.
• Remove all your jewellery and piercings at home before arriving at the hospital for the surgery. In addition, avoid wearing eye make-up or dark-coloured nail polish.
• If you are a smoker, the eye surgeon will ask you to discontinue smoking at least two weeks prior to the surgery. You should also avoid drinking alcohol for a day before the surgery.
• You will be asked to not eat anything after midnight of the night before the surgery. However, you can drink clear liquids, such as water, tea or coffee (without sugar, sweetener, or cream), and apple juice, until two hours before the scheduled time of the surgery.
• Wear loose, comfortable clothes while going to the hospital for the surgery.
• The hospital staff will ask you to sign a consent form, granting permission for the procedure.

Once you reach the hospital, the hospital staff will ask you to change into a hospital gown. The surgery is performed either with general (which will put you to sleep for the duration of the procedure) or local anaesthesia (numbing medicine) and usually involves the following steps:

• After administration of anaesthesia, the surgeon will place a lid speculum (an instrument that keeps the eye open during the surgery) on your eye.
• He/she will mark the centre of your eye as a guideline and then create an incision using a calibrated diamond knife. Your eye will be kept fixed in place during this process.
• Next, the surgeon will insert two semicircular instruments called dissectors into the incision and rotate them clockwise and anticlockwise to create channels for the implantation of the rings.
• The surgeon will then inserts two ring segments through the incisions into these channels and positions them properly with a hook-like instrument called a Sinskey hook.
• Once this is done and the surgery is complete, the surgeon will put eye drops or creams in the operated eye to prevent infection and inflammaiton.

The cut may not need stitches. If the surgery were conducted with general anaesthesia, you would be moved to the recovery ward following the operation.

Before you are discharged from the hospital, the surgeon will give you certain instructions to take of yourself. These include:

• Wear dark glasses during the day and an eye shield while sleeping for some days following the surgery.
• You will be prescribed antibiotics and eye drops, take them as prescribed.
• You can resume watching TV and walking right after the surgery. However, avoid swimming, contact sports, jogging, and other similar activities for four to six weeks.
• You will likely be permitted to bathe, below the neck, on the same day of the surgery. However, the surgeon may not recommend taking a head bath for three to four weeks. 
• While shaving or washing your face, do not let water go inside the operated eye.
• Resume driving only after consulting with the surgeon.
• Avoid the use of eye cosmetics for a minimum of four weeks.
• Avoid smoking and drinking alcohol until your doctor allows you to after surgery.

The procedure does not eliminate the need for contact lenses or spectacles. Instead, ICRS stabilises the cornea to make the use of contact lenses and glasses more comfortable.

When to see the doctor?

Contact the eye surgeon immediately if you:

• Feel that your symptoms are getting worse
• Experience discharge, increasing pain, redness, or decreased vision

Some of the risks or side effects associated with the surgery include:

• Infection
• Glare
• Problems with night vision
• Fluctuating vision
• Blurred vision
• Halos
• Contact lens fitting becomes difficult
• Dissatisfaction with vision correction post-surgery

Most of the side effects mentioned above resolve within three to six months after surgery. However, some people experience these symptoms even after a few years, which can lead to the removal of ICRS.

Your eye will be checked daily for the first two to three days after the surgery. Additionally, you will be required to follow up at six weeks, three months, six months, and 12 months after the surgery.

Disclaimer: The above information is provided purely from an educational point of view and is in no way a substitute for medical advice by a qualified doctor.