Corneal pannus is the growth of fine blood vessels onto the clear corneal surface. The treatment depends on the cause. For instance, a common cause of corneal pannus is a poorly fit contact lens. Also, pannus can occur if the contact lens does not allow enough oxygen to the eye. Contact lens may need to be temporarily or permanently discontinued. Sometimes a pannus may represent an old or current infection that is dangerous to vision such as can be caused by herpes simplex.