Keratitis is in inflammation of the cornea, the dome shaped window in the front of the eye.
Herpes viruses (some of these cause cold sores in the mouth, others cause chicken pox and shingles) is a frequent cause of keratitis, and has a particular appearance on examination.
Almost all keratitis is infectious.
One common type of keratitis is a corneal ulcer, when immune cells attack a microbe that has invaded the cornea. This condition usually affects contact lens wearer.
Infectious keratitis requires frequent eyedrop and or systemic (pills) therapy.