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Differences Between FDA-Approved, Off-Label, and Unapproved Cross-Linking.

Access to Cross-Linking in the U.S.

Epi-off cross-linking requires the removal of the epithelium, the outermost layer of the cornea, to assure penetration of the prescription eye drops. This protocol has been rigorously tested and is the only cross-linking procedure approved by the US Food and Drug Administration (FDA) when performed with Photrexa Viscous, Photrexa and the KXL System.


Epi-on cross-linking is a procedure where the epithelium is left intact. In the U.S., there are currently no epi-on cross-linking procedures that are FDA approved.

The use of any drug(s) other than Photrexa® Viscous and Photrexa® or any device other than the KXL® System for corneal cross-linking is not FDA approved, except as part of an investigational new drug (IND) study.

FDA Approved Cross-Linking

Which Corneal Cross-Linking
Procedures Are Currently FDA
Approved in the US?

Epi-off cross-linking performed with Photrexa® Drug Formulations, Photrexa® Viscous, Photrexa® and KXL® System is the only cross-linking procedure approved by the FDA.

The FDA approval letters for these cross-linking products can be found here:

Treatment of Corneal Ectasia Following Refractive Surgery

FDA-approved cross-linking is performed with drug products that have been rigorously tested and are specifically controlled and manufactured in an FDA-registered facility and in compliance with FDA guidelines.

Corneal Cross-Linking: A New Standard of Care for Progressive Keratoconus

Corneal collagen cross-linking is an innovative therapy that has transformed the treatment of progressive keratoconus. Historically, as many as 1 in 5 patients with progressive keratoconus have required a corneal transplant, with more than half needing multiple transplants within 20 years.1, 2

Photrexa® Viscous, Photrexa® and the KXL® System are the first and only therapeutic products for corneal crosslinking which have been FDA approved to treat progressive keratoconus, offering an effective treatment for patients who had no therapeutic options to limit the progression of this sight-threatening disease. The epi-off cross-linking procedure with Photrexa® Viscous, Photrexa® and the KXL® System is FDA-approved, clinically proven, safe and effective.

As with most procedures, adverse events such as corneal haze can occur, and your doctor should monitor you for risks of infection.

1Pramanik S, Musch DC, Sutphin JE, Farjo AA. Extended long-term outcomes of penetrating keratoplasty for keratoconus. Ophthalmology 2006;113(9):1633-8.

2Maharana PK, Agarwal K, Jhanji V, Vajpayee RB. Deep anterior lamellar keratoplasty for keratoconus: a review. Eye Contact Lens 2014;40(6):382-9.

Is Corneal Cross-Linking Covered by Insurance?

Insurance coverage for FDA approved cross-linking with Photrexa® Viscous, Photrexa® and the KXL® System is now widely available. Greater than 95% of the commercially insured population has access to this potentially sight-protecting treatment. For additional information on insurance coverage and to view the latest list of insurers that are known to have policies that cover cross-linking, visit the Insurance Information page.

What Can I Expect During the Corneal
Cross-Linking Procedure?

  • After numbing drops are applied, the epithelium (the thin layer on the surface of the cornea) is gently removed.
  • Photrexa® Viscous (riboflavin 5’-phosphate in 20% dextran ophthalmic solution) eye drops will be applied to the cornea for at least 30 min;
  • Depending on the thickness of your cornea, Photrexa® (riboflavin 5’-phosphate ophthalmic solution) drops may also be required.
  • The cornea is then exposed to UV light for 30 minutes while additional Photrexa Viscous drops are applied.