Contributor: Gordon K. Klintworth
Conjunctivitis may be acute [conjunctivitis - acute] or chronic [conjunctivitis - chronic]. It  can be classified into several different types based on the nature of the inflammatory reaction: acute purulent conjunctivitis [conjunctivitis - acute purulent], hyperacute conjunctivitis [conjunctivitis - hyperacute], acute catarrhal conjunctivitis [conjunctivitis - acute catarrhal], chronic catarrhal conjunctivitis [conjunctivitis chronic catarrhal], membranous conjunctivitis [conjunctivitis - membranous], pseudomembranous conjunctivitis [conjunctivitis - pseudomembranous], acute follicular conjunctivitis [conjunctivitis - acute follicular], chronic follicular conjunctivitis [conjunctivitis - chronic follicular],  ophthalmia neonatorum, and Parinaud oculoglandular syndrome. Causes of conjunctivitis include a variety of bacteria [conjunctivitis - bacterial] (Brucella [brucellosis], Corynebacterium diphtheriae [diphtheria], Neisseria gonorrhoeae [gonorrhea], Neisseria meningitidis, Haemophilus influenzae, Streptococcus sp. [streptococcal infection], Staphylococcus sp. [staphylococcal infection], Francisella tularensis, Mycobacterium tuberculosis [tuberculosis], Listeria monocytogenes [listeriosis], Haemophilus ducreyi, Yersinia sp, Treponema pallidum [syphilis], Bartonella henselae [cat scratch disease]) and viruses [conjunctivitis - viral]. Most of these organisms reach the conjunctiva from the tissue surface, but in some infections the conjunctivitis is part of a systemic disease in which the bacteria are acquired by an endogenous route (as secondary syphilis [syphilis - secondary]). An uncommon and rarely diagnosed type of conjunctivitis is self-inflicted conjunctivitis [conjunctivitis - self-inflicted].