As a corneal specialist, I treat many patients with keratoconus. Many times, these patients would come into my office in their late teens and while I would do what I could to treat their condition with glasses and contact lenses, by the time they reached their 30th birthday they would need a corneal transplant. Although these patients generally do well with a transplant, it is preferable to have an alternative method of treatment that is less-invasive with a quick recovery time.
This is why I decided to become involved in the U.S. FDA trials for Avedro's corneal cross-linking technology, and once it was FDA approved in spring 2016, I began offering it to my patients that summer.
What is Corneal Cross-Linking?
In April 2016, Avedro received U.S. FDA approval for its corneal cross-linking technology, including the KXL® System, Photrexa® Viscous (riboflavin 5’-phosphate in 20% dextran ophthalmic solution) 0.146%, and Photrexa (riboflavin 5’-phosphate ophthalmic solution) 0.146%.
In the most basic sense, corneal cross-linking is a treatment where riboflavin drops are applied to and absorbed by the cornea. An ultraviolet light treatment is then applied to the eye, causing a reaction within the corneal stroma to create bonds called cross-links. Those bonds stiffen and strengthen the cornea so it stops thinning, weakening and distorting.
How it Works
In a standard cross-linking treatment, the epithelium is removed and Photrexa Viscous is applied one drop every two minutes for 30 minutes. After 30 minutes, we check the cornea to make sure that the Photrexa Viscous has been adequately absorbed into the cornea. We also check corneal thickness — if the corneal pachymetry is less than 400 microns, it is considered too thin to treat at that time. If that happens, we start to administer one or two hypotonic Photrexa drops every minute or so for several minutes until the cornea swells and is safe to treat.
A patient undergoes corneal cross-linking. Photo courtesy Dr. Kenneth Beckman
The eye is then treated with ultraviolet light through the KXL System for 30 minutes. The device has a very precise set-up via a joystick that allows the practitioner to focus the aiming beam directly on the cornea. Once the aiming is set, the doctor only has to hit start and the system will administer the light treatment until a timer shuts it off. At the end of the treatment, I place a bandage contact lens on the eye.
In general, the treatment is more boring for the patient than invasive — the majority of the time the patient remains still. I commonly tell my patients to bring in headphones because they will be sitting still for an hour with nothing to do.
As this is an epi-off procedure, it is very similar to a PRK, and patients will have an epithelial defect for several days. They may be uncomfortable and have some burning and foreign body sensation for the first few days. We have patients use drops regularly, and that usually keeps them comfortable.
Post-treatment, I usually see them at one day and one week, during which I remove the bandage lens. As the procedure takes over an hour, we do one eye at a time. I'll typically treat the second eye after the one-month visit for the first eye. I want to make sure they’re comfortable with their vision in the first eye because they may have to rely on that first eye for a while after we do the second eye.
Patient Benefits
With corneal cross-linking, the greatest patient benefit is preventing corneal transplant surgery. It is amazing to take patients who have a condition with a high surgical risk that would require a lifetime of aftercare and offer them a way to avoid that.
Secondly, you're able to give your keratoconus patients better quality of vision. Through corneal cross-linking, not only can you halt the deterioration of a patient's vision, you also have the potential for regression and improvement for a better quality of life. While they may not see better on the Snellen acuity chart, with treatment their cornea often becomes more spherical and there are less aberrations to their vision, resulting in a subjective improvement in visual quality.
Theoretically, down the road, if the cornea has become stabilized a patient may be able to undergo laser refractive surgery to correct any residual astigmatism.
For the future, Avedro is currently investigating using corneal cross-linking as a refractive procedure for the non-invasive treatment of low myopia. Called the PiXL™ Procedure (Photorefractive Intrastromal Corneal Cross-Linking), last fall Avedro announced promising preliminary findings for two European studies on the treatment, including positive safety and efficacy results and a high patient satisfaction rate.
Additionally, doctors in Europe are currently using corneal cross-linking in combination with LASIK. Called LASIK Xtra, through this procedure the cornea is stabilized at the same time they are receiving LASIK to help prevent the risk of ectasia.
Rethinking Patient Management
Corneal cross-linking provides practitioners with a new option for treating keratoconus patients. It requires a new way of thinking, and we now need to retrain primary eyecare providers — both ophthalmologists and optometrists — to rethink management of these patients.
When the only other option was corneal transplant surgery, eyecare providers merely monitored these patients for as long as they could until they needed surgery. Now that crosslinking is available, it is critical to address the issue as soon as the diagnosis is made because corneal cross-linking is at its best when their vision is still good, to prevent further vision loss.
If managing keratoconus patients is a big part of your practice, then corneal cross-linking could be a great addition to your practice. As a referral corneal practice, I now have a treatment to offer patients that the rest of the world has been using for many years. The key is early diagnosis early and having patients sent early for evaluation, because when time is wasted, you potentially lose vision. Vision loss is a lot easier to prevent than it is to restore.
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