Corneal Collagen Crosslinking (CXL)
Collagen cross-linking (CXL) is a method of treating keratoconus, an eye disorder in which the normally globe-shaped cornea loses its ability to hold its shape, resulting in bulging and protrusion of the cornea. The abnormal conical shape of the cornea in keratoconus does not allow for proper focusing of light into the eye. Collagen cross-linking works by strengthening the corneal tissue to stop it from bulging. During this procedure, eye drops containing riboflavin (vitamin B2) are applied to the cornea and activated by ultraviolet light. This process strengthens (crosslinks) the collagen fibers within the cornea. These crosslinks act as corneal anchors, preventing the cornea from further bulging into an irregular shape.
Originally developed in Germany, it has been used in Europe and around the world, successfully for nearly 15 years. CXL was approved by the FDA in the United States in April 2016. Dr. Seth Meskin was part of a small group of doctors in the United States that served as an investigator for one of the recent FDA clinical trials on CXL. As such, Dr. Meskin has performed several CXL treatments on patients as young as 13. He also has worked with colleagues from around the world and has years of experience caring for patients before and after their CXL procedures. Dr. Meskin was the first surgeon in the state of Connecticut to perform Corneal Collagen Crosslinking (CXL) with the FDA approved CXL device made by Avedro in Massachusetts. This CXL device by Avedro is the ONLY CXL device currently approved for CXL in the United States.
Candidates for CXL
In addition to patients who suffer from keratoconus, other patients who may be candidates for corneal crosslinking are individuals who have disorders such as:
- Pellucid marginal degeneration
- Ectasia (corneal weakness occurring after LASIK)
- Corneal instability after radial keratotomy
Certain eye conditions may preclude a CXL procedure.
The CXL Procedure
Prior to the CXL procedure, the ophthalmologist performs a full eye examination to check visual acuity, general eye health, and the thickness of the cornea. A corneal topography, which maps the area, will also be performed. Before beginning the procedure, anesthetic eye drops are administered to the patient. The CXL procedure itself involves administering riboflavin drops to the eyes. These drops flood the cornea, which is subsequently activated by ultraviolet A (UV-A) light for up to 30 minutes.
In most cases, the procedure takes less than 60 minutes to perform. Afterwards, antibiotic and anti-inflammatory eye drops are administered and a bandage contact lens is inserted. The eye is bandaged overnight. There is pain after the procedure, but pain medication may be prescribed and most of the pain subsides within 12 hours.
Although the CXL procedure is not a cure for keratoconus, it is used to prevent the progression of this disease process. Evidence shows that CXL is able to prevent further loss of vision in patients with keratoconus, and if treated early enough, to significantly reduce the risk of needing a corneal transplant. Corrective lenses are still required after CXL and a change in prescription may be needed. In some cases, patients may be required to wear hard contact lenses (RGP, Hybrid, or Scleral Lenses, e.g.) after the surgery.
Types of CXL Procedures
There are two basic types of corneal crosslinking procedures currently in use:
- Epithelium-on (transepithelial)
The epithelium-off procedure, in which the thin top layer of the eye is removed, permits more rapid penetration of the riboflavin. During the epithelium-on procedure, the surface layer remains intact, necessitating a longer penetration time for the riboflavin. Research studies have shown that most patients who have undergone either type of CXL procedure retain stable corneal shape or show significant improvement. There continues to be some debate about which procedure is preferable. Currently, the epithelium off procedure is the only one approved by the FDA in the United States.
Risks of CXL
CXL is a very safe and effective procedure. Like all surgical procedures it has some risk, like infection or inflammation. Your doctor will discuss these risks in more detail during your visit.
Recovery from CXL
Patients undergoing CXL should expect pain during the first 2 days after surgery, as well as sensitivity to light. They may also experience a haze that causes their vision to blur for up to a few months. During recovery, analgesics may be taken to relieve pain. The blurring of vision may make driving or work impossible until the patient is fully recovered.
Normally, a one-time CXL is all that is necessary to preserve vision and the CXL procedure does not interfere with any subsequent eye surgery. The CXL procedure has proven effective in strengthening the cornea, both in the laboratory and in clinical studies. For patients with keratoconus this is extremely important, since, left untreated, the condition may lead to severe vision loss or need for corneal transplant.