Here is another installment of the Paucis Verbis (In a Few Words) e-card series on the topic of The Red Eye from EM Clinics of North America, Here are some sample images:

Epidemic keratoconjunctivitis (note subtle white precipitates over pupil)

Bacterial conjunctivitis (note injection along inferior fornix)

Episcleritis

Acute angle closure glaucoma (note corneal edema)
PV Card: The Red Eye
Go to ALiEM (PV) Cards for more resources.