The most common cause of chronic follicular conjunctivitis is infection with the organism Chlamydiae trachomatis. This infection takes two clinical forms: trachoma and inclusion conjunctivitis.
Trachoma is the leading cause of corneal blindness in the world. It is highly endemic in many developing areas of the world, with the prevalence of the disease related to poor sanitation. Flies are believed to be an important vector for the spread of the disease. The high level of morbidity, in contrast to inclusion conjunctivitis, is likely related to multiple recurrences of infection, as well as frequent concurrent bacterial superinfections.
Trachoma causes a follicular conjunctivitis where the follicular response is predominant in the superior conjunctiva. Superior pretarsal follicles can become as large as those seen in the conjunctival fornix, in which case they are termed "mature" (Figure 7). Follicles can also occur at the limbus; necrosis of limbal follicles leads to depressed limbal scars called "Herbert's pits", a finding that is pathognomonic for trachoma. A vascular pannus most marked along the superior limbus is frequently seen. With progression of the disease, trachoma is a cicatrizing as well as a follicular conjunctivitis, with development of linear subepithelial scarring affecting the pretarsal conjunctiva. A dense linear scar superior to the upper lid margin is called an "Arlt's line" (Figure 8). Conjunctival scarring causes cicatricial entropion and trichiasis, which leads to the corneal scarring that can result in blindness.
Inclusion conjunctivitis is the most common form of ocular chlamydial infection in the developed world. It is a sexually transmitted disease. C trachomatis is the most prevalent cause of nonspecific urethritis in men and cervicitis in women and reaches the eye by genital-ocular transmission. While inclusion conjunctivitis can sometimes be diagnosed during the acute stage (<3 weeks duration), nontreated or inadequately treated infections will persist well longer than 3 weeks. Symptoms include redness of the eye and a mucopurulent discharge. Clinical findings are those of a follicular conjunctivitis, with the lower palpebral conjunctiva being most severely affected on exam (the upper forniceal conjunctiva is likewise affected, but is not visible on examination without double-eversion of the upper eyelid). Follicles in the bulbar conjunctiva and semilunar fold are frequently present. Follicles in chlamydial infection are significantly larger than those seen in viral conjunctivitis. Follicles do occur on the upper tarsal conjunctiva, but they appear as slightly elevated whitish lesions, never becoming mature as in trachoma. A small, nontender preauricular lymph node is usually palpable in all forms of chronic follicular conjunctivitis. Subepithelial corneal infiltrates are often seen, but they tend to be more peripheral and less diffuse than those seen in epidemic keratoconjunctivitis (EKC).
Diagnosis of trachoma and inclusion conjunctivitis is usually made based on clinical findings. Inclusion conjunctivitis gets its name from the basophilic inclusions capping the epithelial cell nucleus seen on Giemsa-stained conjunctival scrapings, which can be seen with either form of chlamydial infection. More important than identification of inclusions, however, is the predominant type of inflammatory cell, as chlamydial infection is the only form of chronic follicular conjunctivitis where PMNs predominate. This test, however, is rarely done any more because of extremely low sensitivity, especially in adults. The diagnosis can be confirmed by chlamydial culture, direct fluorescent antibody staining, or PCR techniques.
Neither form of adult chlamydial infection responds to topical antibiotics. In addition, inclusion conjunctivitis is a systemic disease and the genital infection must be treated as well. Appropriate treatment is an adequate course of an oral antichlamydial antibiotic, the most effective being azithromycin or doxycycline. Various treatment regimens exist, including azithromycin 1 gram single dose, doxycycline 100 mg bid for 7 days, tetracycline 250 mg qid for 7 days, or erythromycin 500 mg qid for 7 days. In addition, treatment of regular sexual contacts is important to prevent recurrent infection. Periodic mass administration of antichlamydial antibiotics in endemic areas can reduce the overall morbidity of trachoma in treated communities.