February 25, 2009 --
Corneal collagen crosslinking with Riboflavin (CXL) is an experimental treatment for two eye conditions: keratoconus and ectasia. Currently, the conditions have no medical treatment and are responsible for 15 percent of corneal transplants in the United States. Keratoconus is a corneal disease that causes the cornea to weaken and gradually bulge outwards into a cone shape. Normal corneas are round and dome-shaped. The disease is estimated to affect every one of 2,000 individuals in the general population. In the early stages of the disease, blurring of vision and increased sensitivity to glare and light can occur. Symptoms typically first appear when individuals are in their late teens or early 20s. The condition can worsen for 10 to 20 years before stabilizing. Each eye may be impacted differently. Early vision changes from keratoconus, such as nearsightedness and astigmatism, can be corrected with glasses or contacts, but as the cornea continues to change, wearing contacts becomes difficult. In severe cases of keratoconus, corneal transplants may be necessary, where the keratoconus cornea is replaced with donor tissue. Also referred to as iatrogenic keratoconus, ectasia is a condition that causes the cornea to bulge; however, in this condition the change in shape is caused by LASIK vision correction surgery. "These are people who had a propensity to develop keratoconus probably and simply developed it quicker or perhaps when they might not have developed it otherwise after they had LASIK," Doyle Stulting, M.D., Ph.D., an ophthalmologist at Emory University Eye Center in Atlanta, Ga., told Ivanhoe. LASIK penetrates the cornea more than other eye procedures and can cause excessive thinning and structural damage to the cornea. Ecstasia is usually diagnosed within the first two years following surgery.
HOPE IN A DROP: CXL treatment works by increasing collagen crosslinking in the cornea. The crosslinks are responsible for maintaining the cornea's round shape. The procedure is done in the doctor's office and takes only a half hour. CXL first requires removing the corneal epithelium. Then, vitamin B, or riboflavin drops saturate the eye, which is then exposed to ultraviolet light. "During that time there is a reaction between the ultraviolet light and the riboflavin, which joins or links the collagen molecules in the cornea, and in doing so makes it stiffer than it otherwise would be," Dr. Stulting explained.
Although the procedure is still under investigation in the United States, preliminary results have shown CXL effectively stabilizes eyes. International clinical trials have also found CXL can stop the progression of keratoconus and ecstasia and improve vision. The effects appear to be long-term, as some European study participants were followed for up to eight years after they had the procedure. CXL is currently approved in Europe.
"As we move forward, I can envision a day where we will diagnose keratoconus very early, as soon as there are any abnormalities in the shape of the cornea," Dr. Stulting said. "We will crosslink those eyes and then they won't progress." Patients who are at risk for ectasia can be identified before having LASIK, so that they can undergo the CXL treatment and then safely have the eye correction procedure.
FOR MORE INFORMATION, PLEASE CONTACT:
Emory Eye Center
Kathy Wynne, CXL Trial Coordinator