Corneal collagen cross-linking (CXL) has increasingly become the hot topic of nearly every conversation amongst corneal experts around the globe. When effective, the procedure provides the best opportunity for arresting or slowing the ectatic progression of the irregular cornea. As the procedure has become more widely accepted by the mainstream medical community, it has placed an increased burden on the referring optometrist to educate, prepare, and manage the irregular cornea patient.

The below questions have been posed to me numerous times over the years. My provided responses, formed from years of engagement in active clinical practice, are not exhaustive. My hope is to provide a level of comfort and knowledge to the co-managing optometrist so that he or she can recommend the procedure with confidence.

What is corneal collagen cross-linking?

It is a procedure during which a chemical reaction occurs between riboflavin (Vitamin B2), ultraviolet light, and corneal collagen fibrils. The procedure results in a stiffening of the fibrils. As one expert describes it, “we harden the cement”.

What is the difference between epi-on and epi-off?

As the name suggests the epithelium is removed in the epi-off procedure but remains in place for the epi-on protocol. Epi-off CXL has gained FDA approval and has been more widely studied. Epi-on CXL may be less effective, although further research will provider greater insight. Adverse events occur less frequently with epi-on CXL, and healing time is quicker compared to epi-off.

Who gets referred?

In my practice patients, 35 years of age and younger diagnosed with keratoconus receive a referral for a CXL consult. Please understand this does not mean that 100% of these patients undergo CXL – internal data suggests approximately 70% of these patients proceed with the actual consult. But given the documented risk of progression in this age range, it was determined that educating the patients in regard to CXL was paramount. Patients between the ages of 35-45 are referred if they exhibit high-risk characteristics, namely noted progression on corneal mapping. Keratoconic patients over 45 years of age rarely require a referral as the condition tends to stabilize.

How is the procedure performed?

CXL can be performed unilaterally or bilaterally. It takes approximately 30-45 minutes. The patient may receive oral medication to relax them during the procedure but otherwise only receives topical anesthetic. Following either the removal or softening of the epithelium riboflavin drops are placed onto the cornea at a prescribed rate. Once riboflavin has been verified to have fully penetrated the corneal structure via examination the ultraviolet light source is switched on.

Is it painful?

The procedure itself is not painful but the recovery can be quite uncomfortable, particularly with epi-off CXL. Due to the intensity of the UV light source, it is not unusual for redness and sunburn-like symptoms to be felt periorbital. Patients should diligently follow their cornea specialist’s instructions to best manage post-operative discomfort.

Are there any special instructions for the patient pre-op?

Very few! Patients should be educated that in most instances CXL sites prefer the patient to be out of his or her contact lenses prior to the consultation and procedure. The length of time varies based on the surgeon’s protocol. While contact lenses will have little effect on the overall effectiveness of the procedure, the ability to measure CXL’s effectiveness relies on the ability to document stability vs. progression. This is best accomplished by scanning a virgin cornea (or a reasonable facsimile).

How do I handle a patient post-operatively?

Most surgical centers will release the epi-off CXL patients back to the referring doctor’s care when re-epithelialization has occurred or when the patient desires to return to his or her contact lenses. In most cases, the patient can return to their previous contact lenses without the need for an immediate refit. Most topographical and refractive changes will occur within 6-24 months following the procedure. Larger changes would be expected to be required in a corneal RGP fit as opposed to a scleral lens fit. This is due to the post-lens tear layer beneath the scleral lens neutralizing a great deal of the refractive changes that occur post-operatively.

Does it work?

It works remarkably well, in fact. Large studies out of Europe have shown >90% effectiveness in halting or slowing progression of the ectatic cornea.

Obviously, this is only an introduction into the world of corneal CXL. I encourage each eye care provider to become familiar with the preferred referral guidelines for the local corneal specialist that provides CXL so that each of us can best serve our patients.