The Facts
Many of the viruses, bacteria, parasites, and fungi that can invade the
human body are also capable of attacking the surface or interior of the eye.
In fact, there's no such thing as an "eye bug" that attacks only the
eye.
Infectious eye diseases can be categorized in two ways.
Firstly, doctors normally talk about the part of the eye that's infected or
inflamed. Conjunctivitis, for example, is an inflammation of the conjunctiva,
the membrane of the inner eyelid and the inner corner of the eye's surface.
Other possible locations of inflammation include the eyelid (blepharitis),
the cornea (keratitis), the liquid inside the eye (vitritis),
the retina and the blood vessels that feed it (chorioretinitis), or the
optic nerve (neuroretinitis). These are just a few examples - the eye
is a complex organ of many parts.
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.
The most common eye infection is conjunctivitis caused by an adenovirus
(a type of common cold virus). This type of infectious conjunctivitis
is sometimes called "pinkeye" and is most common in children. There
are, however, other causes of infectious conjunctivitis such as bacteria like
Staphylococcus aureus. Bacterial causes tend to result in longer-lasting
cases of pinkeye.