Figure 5-7 Conjunctival foreign-body granuloma. A, Clinical appearance on the bulbar conjunctiva. B, Histologic analysis of the specimen from a different patient under polarized light shows multiple foreign fibers of various colors, with surrounding foreign-body granulomatous reaction, including multiple giant cells (arrowheads). (Part A courtesy of Anthony J. Lubniewski, MD; part B

courtesy of George J. Harocopos, MD.)

Chlamydiae are obligate intracellular pathogens that may cause follicular conjunctivitis. Chlamydia trachomatis is a major cause of ocular infection (trachoma), particularly in the Middle East. Serotypes A, B, and C are associated with trachoma; serotypes D through K cause neonatal and adult inclusion conjunctivitis. Exfoliative cytology of ocular surface epithelium (Giemsa stain) or tissue biopsy may demonstrate these intracellular organisms (Fig 5-8).

When the conjunctiva alone is infected, fungi are rarely the inciting pathogen. Fungal ocular surface infections typically involve the cornea (see Chapter 6).

Microsporida, a group of obligate intracellular parasites, may cause conjunctivitis, keratitis, or keratoconjunctivitis, particularly in patients with acquired immunodeficiency syndrome (AIDS). Rhinosporidium seeberi, which may cause an isolated conjunctivitis (typically affects the palpebral/forniceal conjunctiva), is seen most often in areas such as India and Southeast Asia but has also been reported in the southeastern United States. Infection is typically associated with exposure to stagnant water. This organism was initially classified as a fungus but has been reclassified as a protozoon. The protozoon Acanthamoeba occasionally causes an isolated conjunctivitis but typically also infects the cornea (see Chapter 6). This diagnosis should be considered in chronic unilateral conjunctivitis unresponsive to standard therapy; exfoliative cytology may be helpful in establishing the diagnosis.

Noninfectious Conjunctivitis

As discussed previously, most papillary conjunctivitis, some forms of granulomatous conjunctivitis, and toxic follicular conjunctivitis are associated with noninfectious etiologies. See the sections Papillary Versus Follicular Conjunctivitis and Granulomatous Conjunctivitis for specific examples.

Ocular cicatricial pemphigoid (OCP) is a form of cicatrizing conjunctivitis that is of autoimmune etiology. It typically also involves other mucous membranes and sometimes involves the skin. When this diagnosis is suspected clinically, conjunctival biopsy is performed to establish the diagnosis. Half of the specimen should be submitted in formalin for routine histology, and half submitted in Michel medium or saline for immunofluorescence analysis. Histology shows bullae of the epithelium and a subepithelial band of chronic inflammatory cells, predominantly plasma cells (Fig 5-9).

Immunofluorescence demonstrates IgG, IgM, and/or IgA immunoglobulins, and/or complement (C3) positivity in the epithelial basement membrane zone. The clinician must bear in mind that the sensitivity of immunofluorescence may be as low as 50% (particularly in long-standing cases with severe cicatrization). Thus, a negative result does not rule out the possibility of OCP. See also BCSC Section 8, External Disease and Cornea.