Corneal Collagen Crosslinking with Riboflavin (CXL)
A developing keratoconus and ectasia treatment is Corneal Collagen Crosslinking with Riboflavin (CXL), which has been shown outside of the US to strengthen a weakened corneal structure. This treatment is also known as CCR, CCL and KXL. This method works by increasing collagen crosslinking, which are the natural “anchors” within the cornea. These anchors are responsible for preventing the cornea from bulging out and becoming steep and irregular, as seen in advanced keratoconus.
Keratoconus is a disease of the cornea that makes the cornea become weak and may gradually bulge outward. Most often, this bulging is in the lower half of the cornea and first presents as astigmatism, however not all astigmatism is due to keratoconus. In mild or early stages of keratoconus (forme fruste keratoconus), eyeglasses may correct the astigmatic vision.
The corneal crosslinking treatment is performed in the doctor’s office and takes 30-60 minutes. During the treatment, riboflavin eye drops are applied to the cornea, which are then activated by ultraviolet light. This process has been shown in laboratory and clinical studies to increase the amount of collagen cross-linking in the cornea and strengthen the cornea. The corneal epithelial layer is often removed in order to increase penetration of the riboflavin into the corneal stroma. In published European studies, such treatments were proven safe and effective in patients.
The abnormal curvature of the cornea due to keratoconus changes the cornea’s refractive error producing moderate to severe blurriness of vision. As keratoconus advances, rigid gas-permeable (RGP) contact lenses maybe the only non-surgical way to achieve clear vision. If keratoconus continues to advance, scarring of the central cornea may occur. Approximately half of keratoconus patients have no negative lifestyle effects beyond corrective lenses. The cornea stabilizes after a few years without ever causing severe vision problems. For others, the only resolution to keratoconus has been corneal transplant surgery, with a long healing period and unpredictable refractive error. Even after corneal transplant PKP, keratoconus can reoccur in the new donor cornea. Collagen crosslinking provides a much less invasive method of treatment as compared to corneal transplant surgery. Collagen cross-linking can also be utilized in conjunction with intracorneal ring segments or Intacs to improve corneal asymmetry or optical refraction. In these cases, corneal crosslinking treatments stabilize keratoconus from getting worse as well as help the Intacs reverse the keratoconus steepening that had already occurred. Corrective lenses are normally required after these treatments but with smaller, more normalized prescriptions. Increased corneal symmetry allows for more comfortable contact lens wear, often of daily disposable lenses. These newer methods may have an important role in limiting deterioration of vision, increasing unaided/uncorrected vision, providing patients additional non-invasive options, and reducing the need for corneal transplantation.
Clinical trials are ongoing, but corneal crosslinking is seeing increasing adoption by the ophthalmological community, and has shown success in retarding or stopping progression of the disease. The procedure, with epithelium removed, is approved for use throughout Europe, and commenced clinical trials in the USA in 2008. Over 300 patients have now been treated in the United States in those trials, which are composed of two randomized, controlled, multi-site clinical trials for the treatment of progressive keratoconus and post LASIK ectasia.