What Is Corneal Cross Linking?

22 October 2019

Author: Jacci

What Is Corneal Cross Linking?

Corneal cross-linking is a procedure to treat keratoconus; an eye condition in which the cornea progressively becomes thin and weak, affecting around one in 450 people.

During the procedure, new links of collagen fibres are created within the eye to strengthen and stabilise the cornea. In most cases this procedure will take anything from 30-90 minutes to perform.

The end goal of corneal cross-linking isn’t to cure the patient of keratoconus, which is actually an incurable condition, but to significantly delay the progression of the disease.

It is the only known treatment to do so and the preferred alternative to a corneal transplant

In this article we investigate: 

  • The two types of corneal cross-linking procedures
  • Why corneal cross-linking is needed
  • What happens during treatment
  • The ins-and-outs of recovery 

The two types of corneal cross-linking

There are two methods of corneal cross-linking; epithelium-off cross-linking and epithelium-on cross-linking. The epithelium refers to the thin outer layer of the cornea; which protects the cornea from bacteria.

Let’s explain:

corneal cross linking

Epithelium-off cross-linking

During this procedure the epithelium is removed, to allow the liquid riboflavin to enter the deeper corneal tissue.

Although this technique works very well, it is also believed to increase the risk of infection and can lead to clouding in your cornea. 

Epithelium-on cross-linking

In this procedure, the protective corneal epithelium is left intact and instead loosened with eye drops; making it a less invasive procedure than epithelium-off cross-linking.

With this method there are fewer side effects, however some experts question whether the epi-on treatment can stop keratoconus. Studies are still in process to clarify just how effective this method is.

Surgeons often debate as to which of these methods is better, but as it currently stands, the FDA have only approved the epi-off procedure.

When is corneal cross-linking needed?

Corneal cross-linking, also known as corneal collagen cross-linking, is suitable for those who suffer keratoconus. It is usually only recommended in deteriorating cases, in a bid to slow the condition down. 

Progression of keratoconus usually comes to a halt by your mid-thirties, meaning patients of this age and over are usually not suitable for corneal cross-linking.

Keratoconus occurs when the cornea (front part of the eye) progressively thins and weakens. This in turn causes the eye to bulge and create a cone like shape; this can dramatically distort vision. In severe cases, a corneal transplant may be required. 

Additionally, a similar condition called pellucid marginal degeneration will sometimes require corneal cross-linking. Pellucid marginal degeneration (PMD) refers to bilateral thinning of the peripheral region of the cornea- similar to keratoconus, but not the same!

Corneal cross-linking does not fully correct near-sightedness, far-sightedness or astigmatism. Meaning, if you fall into any of these categories, you will still need to wear glasses or contact lenses following treatment. 

What happens during corneal cross-linking?

Corneal cross-linking is currently the only treatment available to suspend the worsening of keratoconus. Clinical trials have shown that it has a success rate of more than 90%.

As well as preventing keratoconus from getting worse, corneal cross-linking can also improve the shape of the cornea; this is true for around 45% of cases.

The treatment itself is minimally invasive. During the procedure a liquid called riboflavin (vitamin B2) is applied to the surface of the eye immediately followed by exposure to ultraviolet light. 

This combination induces a reaction, which causes fibres within the cornea to cross-link (bond more tightly); mimicking the natural stiffening of the cornea which happens with age.

In most cases, the procedure takes 30-90 minutes. If you are undergoing epithelium-off, your surgeon will place you in a reclining position to remove the epithelial layer from your cornea.

Recovering from corneal cross-linking

Patients can return straight home after corneal cross-linking; with recovery usually taking around one week. Within this time, it is strongly advised that patients do not drive or commence any sporting activities, until given the all-clear from their surgeon.  

Vision may be blurred for a few days following surgery, but this will improve gradually. Slight discomfort may also be experienced for up to 5 days post-surgery; however this varies from patient to patient. 

Ultralase have developed a clear aftercare schedule for corneal cross-linking patients. Five visits are required, with the first being 3-4 days after treatment and discharge usually 9 months later. 

Medicated eye drops will be provided after surgery. These help to prevent infection, reduce inflammation and relieve discomfort; it is in the best interest of the patient to take this medication exactly as directed by the surgeon.

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