Vascularization
Without blood vessels, the cornea has a weak oxygen supply. Different conditions may decrease the amount of oxygen reaching the cornea and if not addressed, nearby blood vessels may actually grow into the cornea to supply more oxygen as shown in this photo. Blood vessels are not transparent so if growth continues, vision will be affected. Insufficient oxygen may also cause the cornea to swell (edema) which increases myopia (nearsightedness) over time.

