In vivo observations on experimental corneal neovascularization with a newly developed macroscope

The process of corneal neovascularization induced by alkali burns was periodically observed with a newly developed macroscope. The central corneas were burned using filter discs measuring 6 mm in diameter that had been immersed in 1 N NaOH. At 0, 1, 3 and 7 days and at 2, 3 and 4 weeks after injury, the corneas were observed with the macroscope and then examined histologically. At 1 day post-burn, the limbal vascular plexus was engorged but no new vessel formation was detected. By 3 days, many vascular sprouts had arisen from the limbal vascular arcade. At 7 days, the vascular sprouts grew and became fine new vessels. At 2 weeks, the new vessels lengthened further to the central cornea. At 3 weeks, trunk vessels extended and branched like a vascular tree. Blood in the trunk vessels appeared to flow slowly to and fro. The ends of the vessels swelled in a fusiform shape on the application of slight pressure of the macroscope probe. Histological examination revealed that the ends of the vessels consisted of single vascular endothelial cells and the trunk vessels were covered by pericytes. By 4 weeks, the branch vessels around the burned lesion had degenerated and collapsed. Thus, our in vivo study using the new macroscope not only clarified the process of corneal neovascularization from the early to the regressive phases but also provided some valuable new information.