Keratoconus is a condition affecting about 1 in 2000 people where the collagen fibres in the cornea are relatively loosely arranged and not tightly bound to one another as it would be in a healthy cornea. The result is that the fibres can slip over one another and cause a steepening (cone) of the lower half of the cornea. This leads to a reduction in vision, an increase in astigmatism and the introduction of aberrations that reduce the quality of vision.

Corneal cross-linking (CXL) is a procedure that we have been doing at the Wellington Eye Clinic since January 2007 when the device received CE approval. We were the first clinic in Ireland to offer CXL for keratoconus.

Lens Cross-linking More Cross Linking

The figures above show the parallel corneal layers (white) and the collagen cross-linking (red) which are increased after Corneal Cross-Linking (CXL) treatment.

CXL (also known as CCCL and C3-R) has been used for 7 years prior to this with great success. It was first used in Dresden, Germany on 23 patients with one being treated and the other eye not being treated to monitor efficacy. In the 23 eyes not treated, 22 got worse with progression of the keratoconus. All 23 treated eyes achieved success in terms of slowing down the progression of keratoconus and in most cases, stopping the progression altogether. In fact, a number showed improvements in vision and corneal topography as a result of the CXL.

This is the only procedure available to specifically stop the progression of keratoconus and strengthen the individual collagen fibres in the cornea.

At the Wellington Eye Clinic, we have found the following:
In all cases, the progression of deterioration slows down.
In almost all cases, it stops altogether and the cornea becomes very stable unlike with progressing keratoconus where it continuously deteriorates.
In approximately 70% the corneal shape actually improves.

We currently suggest CXL in 2 specific instances:

There is evidence of the condition progressing

A patient who has been wearing a hard contact lens finds that they cannot wear it any longer: CXL is performed here to hopefully allow the CL to be worn again and secondly, to prevent the need for a corneal transplant.

In order for CXL to be performed, the cornea requires at least 400 micron of stromal thickness (the amount of cornea below the epithelial layer on the surface). If the cornea is thinner than this, CXL can still be done by first hydrating the cornea, causing it to swell to at least 400 microns, and then doing the CXL.

In cases where the cornea has still got very good thickness (around 500 micron and more), we have the ability to do a procedure called SimLC (Simultaneous Laser and CXL). Here the corneal surface is first smoothed using an excimer laser in topography-guided mode to create a better shape and then this shape is “fixed in time” with the CXL procedure that follows directly thereafter. (Topography-guided laser is based on the corneal shape rather than the refraction / glasses prescription like regular laser procedures)

The average amount of corneal shape improvement that we are achieving with regular CXL is just over 2 diopters while with SimLC, the average improvement is over 6 diopters (measurement of refractive error or corneal power). This figure is calculated by adding the amount of flattening achieved over the steepest area (usually at the 6 o'clock position on the cornea) to the amount of steepening achieved over the flattest area (usually at the 12 o'clock position).

10 diopters of corneal flattening

The procedure takes 1 hour and is done on site in the Wellington Eye Clinic’s facilities at the Beacon Medical Campus in Sandyford. One eye is done at a time and the time interval between two eyes is normally 6 months but depending on individual circumstances, it can be done 3 months apart. The procedure involves gently peeling back the corneal epithelium (surface cells) and then dropping the Riboflavin drops onto the cornea for approximately 20 minutes until the cornea is saturated. Once saturation is achieved, then a light is directed onto the cornea for 30 minutes while continuing to drop the Riboflavin drops onto the cornea. Once this is done, a bandage contact lens is placed on the eye for a period of 5 days before it is removed at the clinic during your post-operative visit. The first day directly after the surgery can be sore with the comfort of the eye improving each day and by the time the contact lens is removed, the eye is generally very comfortable.

Your own contact lenses can be worn again after approximately 1 month following the CXL.

The vision in the eye that has been treated tends to fluctuate after the surgery. The improvements that may occur continue for about 9 months in our experience but may show continued improvement for up to 3 years according to the studies with longest follow-up. During this period, your glasses may no longer have the correct prescription for the eye and we do not recommend changing the glasses until there is relative stability in the corneal shape and the refraction.

Unfortunately at this stage the health insurers in Ireland do not cover the procedure. The FDA in the USA has started its trial into CXL in January 2008 and once the procedure is FDA approved (hopefully around summer 2010), the local health insurers will consider covering the costs. There is a tax rebate available on the Med-1form (available in the clinic) of 20% of the costs.

The costs are as follows:
CXL: € 1500-00 per eye.
SimLC: € 2400-00 per eye

If you have any further queries, please contact the WEC on (01) 293 0470 or speak to one of the staff at the clinic to arrange an appointment with Dr. Cummings or Dr.Corkin.

For further information please visit The Global Keratoconus Foundation

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