• 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).