Photrexa Viscous and Photrexa are the photoenhancers developed to be used with the KXL system in corneal collagen cross-linking to treat progressive keratoconus, which is a progressive thinning and distortion of the cornea.

The approval was based on data from three prospective, randomized, parallel-group, open-label, placebo-controlled and 12-month trials carried out in the US.

The trials were designed to determine the safety and effectiveness of Photrexa Viscous and Photrexa when used for performing corneal cross-linking in eyes with progressive keratoconus.

Avedro recruited 58 patients with progressive keratoconus in the study one, while around 147 patients with progressive keratoconus in the study two.

Avedro chief operating and financial officer Brian Roberts said: "We’re excited to provide ophthalmologists in the United States with these tools to treat this orphan disease.

"We plan to begin taking orders for the KXL System immediately, and plan to begin shipping our Photrexa products in the next few months as we ramp up our drug manufacturing."

Avedro chief medical officer Rajesh Rajpal said: "Avedro and I look forward to working with US ophthalmologists to raise awareness of our new FDA-approved treatment for progressive keratoconus."