Collagen Cross-linking or CXL

A  treatment for keratoconus increases collagen by applying a one-time-only topical dose of riboflavin drops to the cornea and exposing the cornea to a low amount of ultraviolet A (UVA) light. The activated riboflavin enhances corneal strength and integrity by increasing collagen crosslinking, as proven experimentally and published in the peer-reviewed literature.

This riboflavin/UVA therapy has been safe thus far. There have been no reported complications in the crystalline lens or retina due to the limitation of UVA transmission through the cornea. In a 3-year study of patients with actively pro- gressing keratoconus, the pattern of increasing mean keratometry values was not only halted, but it was also reversed and flattened by a mean of 2.00D.That result persisted during the 3-year follow-up period.

What is the CXL procedure?

Ultraviolet light is used to promote increased cross-linking between collagen fibers within the cornea. Increasing the amount of cross-linking results in increased strength or rigidity of the cornea.

 

What is the CXL procedure used for?

Keratoconus and corneal ectasia are conditions where the cornea bulges and becomes “cone” shaped. This results in astigmatism which can become irregular and impair vision even with glasses. Often contact lenses are the only option available to provide improved vision. Should patients become contact lens intolerant because of disease progression,then surgical options may need to be considered. These options include implantation of Intacs or Ferrara intracorneal rings or partial or full thickness corneal transplants. Strengthening the cornea by cross-linking its building blocks (collagen) can arrest progression of keratoconus and has also been reported to partially reverse the corneal steepening that has already taken place.

What does the procedure involve?

The cornea which is the front transparent structure of the eye is first anaesthetised using drops. The procedure is performed in the clinic in a semi-reclined chair or stretcher. Strong antibiotics are also used to prevent infection. The mucous surface of the cornea (epithelium) is disrupted using a special instrument* and then Riboflavin (Vitamin B2) drops are placed in the eye every few minutes. The drops are yellow and become absorbed by the cornea and the front of the eye. A lid speculum is placed in the eye to keep the lids open and the calibrated ultraviolet device is then focused on the eye and switched on for 30 minutes. It is important not to move during the procedure and medical personnel will check periodically to make sure the device is in the correct position. The yellow pigment of the Riboflavin absorbs the Ultraviolet A light.

Once the procedure is completed, a soft bandage contact lens will be placed in the eye and antibiotics will be instilled. The contact lens will be removed in one or two days.

How long does it take for the procedure to work?

Cross-linking takes place as a result of exposure to Ultraviolet light. The cornea increases in rigidity soon after the procedure although the process of crosslinking continues on for a period of a few days afterwards. The effect on corneal shape takes longer but flattening does not occur in all eyes that have had treatment. A satisfactory result will be arresting the progress of keratoconus. 

How often will I need to be followed?

You will be seen soon after the procedure to remove the contact lens and you will remain on eye drops for a few weeks. You will be seen at 1 month, 3 months, 6 months and one year. Following this it is important that you be seen on an annual basis by your eye care provider as you normally would.

When can I wear contact lenses again?

You may return to wearing lenses after one month. Your lenses may need to be changed if your cornea changes shape. 

Are there any risks?

As the mucous lining of the cornea is disrupted, there is a very small risk of infection. This is rare and prevented through the use of antibiotics before and after the procedure.

Is Ultraviolet light harmful?

Ultraviolet A light used in this procedure is not harmful to the eye in measured doses. Ultraviolet C light (in sunlight) is potentially harmful. The Light emitting diodes used in the 3C-R device is of a wavelength that is not harmful. Furthermore, light emission is carefully measured and calibrated prior to each treatment. There is also a self diagnostic check on the device which prevents use in case of a malfunction. There have been concerns about toxicity to the retina (at the back of the eye) however the Riboflavin pigment in the cornea and front of the eye, absorbs the Ultraviolet light and in effect stops the light from being transmitted to the retina.

At ECC we have been some of the pioneers in Lebanon and the region in providing this sight-saving procedure for many years now and our results have been excellent so far.