This is the creation and growth of new capillaries into non-vascularised areas of the cornea. Visible blood vessels penetrate into the cornea 0.13mm by people not wearing contact lenses, and 0.22mm by people wearing hard contact lenses. Soft lenses induce filling of limbal vessels to 0.47mm from daily wear, and 0.51mm from extended wear.
Neovascularisation occurs mainly in patients wearing soft lenses for extended wear. The most common form is superficial neovascularisation. Blood vessels cross to the cornea from the surface perilimbal vascular plexus, which is tissue growing from the limbo to the cornea. Deep neovascularisation is caused by overgrowth of blood vessels from front ciliary arteries.
In connection with contact lenses, there are two types: active pannus is avascular, formed by inflammatory cells. Fibrovascular pannus consists of overgrown collagen and blood vessels. Neovascularisation is rated from 0 to 4. A rating of 0 indicates a physiological finding to 0.2 mm.