Trachoma is a chronic infectious keratoconjunctivitis caused by infection with Chlamydia trachomatis.
Etiology
Chlamydia trachomatis was isolated using chicken embryo cultures in 1955. It can be classified into 12 immunotypes based on antigenic properties: A, B, Ba, C, D, E, F, G, H, I, J, and K. Endemic and epidemic trachoma is largely caused by antigenic types A, B, Ba, or C. Types D through K are primarily associated with genitourinary infections and inclusion conjunctivitis. Trachoma is a bilateral condition transmitted through direct contact or indirectly via contaminated objects, with arthropod vectors also serving as carriers. The acute phase is more contagious than the scarring phase. Risk factors include poor hygiene, malnutrition, hot and dusty climates, and its spread is favored in tropical and subtropical regions or during dry seasons.
Clinical Manifestations
Trachoma usually affects both eyes, though the severity can vary. The incubation period after Chlamydia trachomatis infection is 5–14 days. Children with trachoma often experience mild symptoms that may resolve spontaneously without leaving sequelae. Adults tend to have a subacute or acute onset, with complications appearing early in the disease course. Initially, trachoma presents as follicular chronic conjunctivitis, which progresses gradually to conjunctival scarring.
Acute symptoms include photophobia, tearing, a foreign body sensation, and abundant sticky or mucopurulent discharge. Eyelid swelling, marked conjunctival hyperemia, papillary hypertrophy, and follicles distributed across the conjunctiva of the upper and lower fornices may occur. Diffuse epithelial keratitis of the cornea and preauricular lymphadenopathy may also be present.
In the chronic stage, discomfort is often mild, presenting only as eye itching, a foreign body sensation, dryness, and a burning sensation. Conjunctival congestion decreases, while the conjunctiva shows a dirty and thickened appearance, with papillary and follicular proliferation. Lesions are pronounced in the conjunctiva of the upper fornices and the upper edge of the tarsal plates. This stage may also involve pannus formation, characterized by a curtain-like array of corneal blood vessels. Over time, the conjunctiva becomes replaced by fibrous tissue, forming scars. The earliest scarring typically appears in the sulcus subtarsalis of the upper eyelid conjunctiva, known as the "Arlt Line," and gradually progresses into a reticular pattern, eventually becoming white and smooth scars. Scarring of limbal follicles results in depressions known clinically as "Herbert Pits." Characteristics unique to trachoma include trachomatous pannus and tarsal conjunctival scarring.
Late-stage complications include entropion, trichiasis, eyelid ptosis, symblepharon, corneal opacities, cicatricial conjunctivitis, and chronic dacryocystitis, all of which can significantly impair vision or even result in blindness.
Diagnosis
The diagnosis of trachoma is often based on specific clinical features such as papillae, follicles, epithelial keratitis, pannus, limbal follicles, or Herbert Pits. However, as papillary hypertrophy and follicular formation on the tarsal conjunctiva are not specific to trachoma, diagnosing early-stage trachoma can be challenging when clinical findings are incomplete. In some cases, a "suspected trachoma" diagnosis may be made, with confirmation requiring laboratory testing. The World Health Organization (WHO) diagnostic criteria require the presence of at least two of the following:
- Five or more follicles on the upper tarsal conjunctiva;
- Typical tarsal conjunctival scarring;
- Limbal follicles or Herbert Pits;
- Widespread pannus on the cornea.
In addition to clinical signs, inclusion bodies within the cytoplasm surrounding the nucleus may be identified in conjunctival scrapings stained with Giemsa. Modified Diff-Quik staining can shorten the detection time for inclusion bodies to just a few minutes.
Treatment
Treatment involves both systemic and topical medications as well as management of complications. For the active stage of trachoma, a six-week course is recommended using 1% tetracycline eye ointment twice daily, or levofloxacin eye drops four times daily, along with a single oral dose of 1 g azithromycin. Alternatively, erythromycin eye ointment twice daily may also be used. Surgical correction of trichiasis and entropion is critical in preventing blindness resulting from late-stage trachomatous scarring.
Prevention and Prognosis
Trachoma is a prolonged chronic condition, and with appropriate treatment and improved hygiene conditions, symptoms may alleviate or resolve. Promoting good hygiene practices, avoiding contact with sources of infection, and improving sanitation in service industries are essential for prevention.