The main objective of this study is to determine the safety of Ex Vivo Cross Linking (CXL) of donor corneal tissue in participants who have undergone high-risk penetrating keratoplasty.

This is a randomized, double-masked, multi site clinical trial to determine the safety of Ex Vivo CXL of donor corneal tissue in 96 participants who have undergone high-risk penetrating keratoplasty.

Participants will be randomized to receive either a corneal tissue that has been untreated vs. a corneal tissue that has been treated with Photrexa® Viscous & Photrexa® and UV light. The tissue will be prepared by a Corneal Tissue Bank under Current-Good-Tissue-Practice (CGTP) and delivered to the respective institutions for transplantation. Participants will be monitored up to 24 months post-transplantation to assess for adverse events of the randomized tissue.

Inclusion Criteria:

• Age 18 and older
• Willing and able to provide written informed consent
• Willing and able to comply with study assessments for the full duration of the study
• Patients undergoing high-risk penetrating keratoplasty, defined as corneal neovascularization (NV) in 1 or more quadrants ≥2 mm from the limbus or extension of corneal NV to the graft-host junction in a previously failed graft
• Superficial vessels are defined as those within the anterior one-third of the cornea and deep vessels within the posterior two-thirds of the cornea (i.e., deep stroma).

Superficial CNV involving ≤2 quadrants (equivalent to ≤6 clock hours) without deep CNV are classified as mild. CNV with >2 quadrants of superficial vessels (>6 clock hours) or 1 quadrant of deep vessels (>3 clock hours) as severe (36).

Exclusion Criteria:

• History of Stevens-Johnson syndrome or ocular pemphigoid
• Ocular or periocular malignancy
• Non-healing epithelial defect of at least 0.5x0.5 mm in host corneal bed lasting ≥6 weeks preoperatively
• Uncontrolled glaucoma
• Change in topical corticosteroid regimen within 14 days of transplantation
• Use of systemic immunosuppressive for indication other than corneal graft rejection
• Participation in another simultaneous medical investigation or trial
• Pregnancy (positive pregnancy test) or lactating
• Pre-menopausal women not using adequate contraception (Reliable intrauterine devices, hormonal contraception or a spermicide in combination with a barrier method)
• Ocular infection within 30 days prior to study entry.
• Presence of anterior chamber intraocular lens
• Active uveitis within 90 days prior to the study entry.
• No ocular surgery or procedure within 90 days prior to the study entry or concomitant to the study procedure.