What is Keratoconus and Corneal Collagen Cross-Linking?
Corneal Collagen Cross-Linking (CXL) is an in-office procedure that treats patients suffering from keratoconus. Keratoconus is a progressive eye disease where the typically round cornea (the front clear window of the eye) thins, beginning to bulge and steepen, creating more of an irregular cone shape. The change in shape disables light from entering the eye properly. The cone shape deflects light as it enters the eye, causing distorted vision. As the shape of the cornea becomes more irregular due to the keratoconus, your vision will continue to worsen, resulting in frequent changes in your prescription. Typically, keratoconus begins during the teenage years and early 20s and often these patients require a new prescription for their contacts and glasses at each yearly exam. Keratoconus can occur in one or both eyes.
Until recently, the only treatment for keratoconus was custom contact lenses. While custom contact lenses correct vision for keratoconus patients, they do not treat the disease itself. Until recently, most keratoconus patients in the United States had to have a corneal transplant to correct their keratoconus. In April 2016, Avedro, a pharmaceutical and medical device company, announced that it received FDA approval for its KXL System. Their KXL System is used in corneal collagen cross-linking for the treatment of progressive keratoconus. Neel R. Desai, MD, Cornea, Cataract, Refractive and LASIK Surgeon at The Eye Institute of West Florida was a Principal Investigator during Avedro’s clinical trial for FDA approval of their KXL System.
How Does Corneal Cross-Linking Work?
Normal, healthy corneas consist of cross-links between the collagen fibers. These crosslinks keep the cornea strong and maintain the normal, round shape of the cornea. A cornea with keratoconus is weak and the cross-links are not strong enough to keep the cornea’s normal shape, thus it begins to bulge and become cone-shaped. Corneal cross-linking adds more cross-links to the cornea, stabilizing and holding its shape. The new cross-links stop the cornea from continuing to thin, thus preventing further loss of vision and decreasing or eliminating the need for a corneal transplant at some point.
- Creates new corneal collagen cross-links
- Results in a shortening and thickening of the collagen fibrils
- Leads to the stiffening of the cornea
Riboflavin (vitamin B2) is important for body growth, red blood cell production, and assists in releasing energy from carbohydrates. Its food sources include dairy products, eggs, green leafy vegetables, lean meats, legumes, and nuts. Bread and cereals are often fortified with riboflavin.
Under the conditions used for corneal collagen cross-linking, riboflavin 5’-phosphate, vitamin B2, functions as a photo enhancer which enables the cross-linking reaction to occur.
Ultra-Violet A (UVA)
UVA is one of the three types of invisible light rays given off by the sun (together with ultraviolet B and ultra-violet C) and is the weakest of the three. A UV light source is applied to irradiate the cornea after it has been soaked in the photo enhancing riboflavin solution. This cross-linking process stiffens the cornea by increasing the number of molecular bonds, or cross-links, in the collagen.
What are the Benefits of Corneal Collagen Cross-Linking?
Major advantages of corneal collagen cross-linking to treat Keratoconus are:
- The treatment is permanent
- Stops the progression of Keratoconus
- It is a simple, outpatient procedure that typically takes about an hour
- Quick recovery
- Eliminates the need for a corneal transplant
- No injections or stitches
- No major precautions
What happens after corneal cross linking?
- One week after the procedure the patient is seen in the clinic and a bandage contact lens that was placed during corneal cross linking is removed. Vision one week after the procedure is poor
- One month after the procedure vision has most likely returned to prior to surgery status and the efficacy of the treatment is evaluated (how successful corneal cross linking was) by evaluating metrics such as the demarcation line. At this visit, the patient will most likely be instructed to receive a specialty contact lens fitting or a new glasses prescription in order to maximize his/her vision. Usually, specialty contact lenses provide the best vision
- The patient is then followed 3, 6, and 12 months after the procedure, and then the follow up is once per year.
- In case both eyes require corneal cross linking, the second eye is scheduled 1 month after the first eye.
Is Cross-Linking Right for Me?
Patients over the age of 14 who have been diagnosed with progressive keratoconus or corneal ectasia following refractive surgery should ask their doctor about corneal cross-linking.
The Eye Institute of West Florida is proud to offer patients in our practice the first and only therapeutic products for corneal cross-linking, which have been FDA approved to treat progressive keratoconus. This approval offers an effective treatment for patients who, until recently, had no therapeutic options to limit the progression of this sight-threatening disease.