The most common cause of keratitis is injury or infection, but this eye issue may develop for a range of other reasons. Viral, fungal, parasitic and bacterial infections may cause this condition, and an infectious keratitis can happen after an injury to the cornea. However, an injury may also lead to inflammation of the cornea without the presence of a secondary infection.
Secondly, eye infections are also classified according to what's causing them. Ocular histoplasmosis syndrome (OHS), for example, is caused by a fungus (the condition is also called chorioretinitis). It generally attacks the blood supply of the retina, on the inner rear surface of the eye.