Corneal Collagen Cross-Linking (CXL)
Keratoconus is a corneal disease that occurs when the normally round dome-shaped cornea (the clear outer area of your eye) progressively thins, causing a cone-like bulge to develop. Keratoconus is typically diagnosed during adolescence and early adulthood with a variable rate of progression. The bulging or "cone-shaped" protrusion is caused by the normal pressure of the eye pushing out on the thinned and structurally weaker areas of the cornea. Since the cornea is responsible for refracting most of the light coming into your eye, an abnormal-shaped cornea can create reduced visual acuity and affect the way you see. This reduced visual acuity can make even simple daily tasks, such as driving, watching television or reading, difficult to perform. The actual cause of keratoconus is not yet known, but there have been studies to suggest a genetic and inherited link to the disease. Other reported risk factors include eye rubbing, ocular allergy, connective tissue disease, long term rigid contact lens wear, and family history of keratoconus. Recent statistics estimate an incidence of greater than 1 in 1,000. It affects male and female in equal proportion and occurs in both eyes in over 90% of patients. Prior to use of corneal collagen cross-linking, up to 20% of keratoconus patients eventually require a corneal transplant.
Corneal Collagen Cross-linking With Riboflavin & UVA (CXL-UVA)
So far there has not been a successful way to stop the progression of keratoconus. With current methods using rigid contact lenses, or Intra Corneal Ring Segments, only the refractive error can be corrected. These treatments have no effect on the relentless progression of the disease, and ultimately a corneal transplant may be required. A new treatment for keratoconus, which has shown great success, is CXL-UVA. The Riboflavin, when activated by approximately 30 minutes with UV-A light, increase the collagen cross-links within the cornea. This allows for some restoration of the cornea's mechanical strength. The procedure is induced by the combined mechanisms of action of a photosensitive/photoabsorbent agent (Riboflavin) with UV-A light rays. The method works by increasing collagen cross linkings, which are the "anchors" within the cornea. These "anchors" form links between nearby filaments of collagen, preventing the cornea from bulging out and becoming steep and irregular. The procedure has been performed in Europe since 1998. Clinical studies have demonstrated the safety and effectiveness of CXL-UVA.
Data to date obtained mostly by physicians outside Canada has strongly suggested this treatment stabilizes the cornea. Many patients have had a lasting effect (no progression) over 5 years after their initial treatment.
Description of CXL-UVA
The procedure is performed under a topical anesthetic (numbing eye drops). It involves gently removing the protective layer on the surface of the eye, the epithelium. A special formulation of Riboflavin eye drops are applied to the surface of the eye for approximately 30 minutes. The eye is then exposed to a safe amount of UV-A light for 30 minutes. After the treatment antibiotics and other eye drops are used, and a protective bandage contact lens is inserted for four to five days. Postoperative instructions are given.
- Enhance corneal rigidity
- Increase the corneal resistance and biomechanical stability of the cornea
- Prevent disease progression
- May defer the need for a corneal transplant procedure
- May reduce the nearsightedness and astigmatism associated with keratoconus
- Enhance contact lens wear
- Reduce risk of progressive ectasia after excimer laser treatment