Foreign bodies as a cause of conjunctival pseudomembrane formation.

There are certain pathological features common to all forms of conjunctivitis. Essentially these are the fundamental characteristics of inflammation: hyperaemia, stasis, cellular exudate, and a fibrin-rich oedematous fluid, added to the reaction of the conjunctival tissues themselves. However, when a fibrin-rich exudate is formed on the surface of the conjunctiva, a pseudomembranous conjunctivitis results. This pseudomembrane consists of a close network of fibrin including leucocytes and other exudative products. It is easily peeled off but may soon recur. In membranous conjunctivitis, the exudate is poured onto the surface but also permeates the superficial layers of the epithelium, and it may actually penetrate the conjunctival tissue down to the tarsal plate, with some obliteration and thrombosis of vessels. Later, organization of the membrane may take place with neovascularization and fibroplasia. In pseudomembranous conjunctivitis, the exudate is more superficial and there is no organization of the fibrin matrix. The formation of conjunctival membranes and pseudomembranes may be evoked by a variety of factors, including common bacterial organisms such as various streptococci and, less commonly, mycobacteria and actinomycetes. Viruses have also been implicated, as in epidemic keratoconjunctivitis. Other aetiological factors are allergic, as in vernal catarrh; toxic, as in erythema multiforme; and chemical irritants, such as acids and alkalis, as well as various vegetable and animal irritants (Duke-Elder, I965). The three following case reports exhibit a common factor which is new in our experience as a possible cause for the formation of conjunctival membranes. This factor is a foreign body, found in the membrane itself, with attendant foreign-body cellular reaction demonstrated on histopathological examination.