The cornea is the clear part of your eye covering the iris and pupil.
It doesn't normally have any blood vessels in it. Neovascularization
is a medical term that describes the growth of blood vessels where
there previously were none.
So corneal neovascularization is the growth of blood vessels into
the cornea. It's a sign of chronic corneal
oxygen deprivation, usually caused by long-term use of
contact lenses. Eyes afflicted with corneal neovascularization may
become painful, red, extremely light-sensitive, and
intolerant of contact lenses. If the blood vessels grow inward far
enough to extend over the pupil, it may cause permanent visual
The best thing to do, of course, is to stop wearing contact lenses.
After a while, the corneal blood vessels will empty out because the
cornea will be getting sufficient oxygen from exposure to the air.
It's unusual for the new blood vessels to disappear entirely, though,
and they often refill when you start wearing contact lenses again.
If you must wear contact lenses, wear the most permeable ones you can find. Clean them often. Replace them often.
If you're wearing contact lenses right now, take them out at the next
available opportunity. Let your eyes rest for a while. Take care of them. You're unlikely to be getting another pair anytime soon.