Chronic conjunctivitis can be caused by many infectious, immunological and toxic agents. Also, anatomic aberrations (like ectropion or proptosis) can cause inflammation. In chronic conjunctivitis the epithelium becomes hyperplastic and the goblet cells increase in number. Crypt-like epithelial infoldings can occur, forming sub-epithelial retention cysts. These cysts contain mucus in which calcification can be seen over time. The presence of perivascular infiltrate in the stroma can induce fibrous bands between the epithelium and the tarsus, which can cause surface irregularities, the so-called papillary conjunctivitis. In fact, the epithelial and stromal responses of a papillary conjunctivitis are non-specific and can also be seen in atopic conjunctivitis and, in a more extreme form in individuals wearing contact lenses (giant papillary conjunctivitis) [108, 114]. When lymph follicles are found in the superficial stroma, it is called follicular conjunctivitis. The presence of these follicles is associated with adenoviral infections . It can also be seen in early chlamydial infections , Borrelia burgdorferi infections [60, 132] and in patients using topical medication. In these situations a lymphoma has to be excluded by immunohisto-chemistry [2, 48, 131].
With long-standing inflammation the epithelium can become atrophic, with loss of goblet cells. The epithelium can show keratinisation, resulting in a white appearance (leukoplakia). The long-standing inflammation may result in scarring of the conjunctival stroma.
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