Chlamydia in the eye is a bacterial infection caused by Chlamydia trachomatis, the same organism responsible for the most common sexually transmitted bacterial infection. This ocular infection, known as chlamydial conjunctivitis or inclusion conjunctivitis, is an inflammatory disease of the eye’s surface. If left untreated, the infection can become chronic, leading to Trachoma, which is the world’s leading infectious cause of preventable blindness.
The Visual Signs of Acute Ocular Chlamydia
The initial appearance of acute ocular chlamydia, or inclusion conjunctivitis, often resembles a persistent case of “pink eye” that does not improve with typical antibiotic drops. The eye usually looks intensely red and irritated, often involving only one eye initially, though it can spread to both. This redness (hyperemia) is generally more pronounced on the tarsal conjunctiva—the membrane lining the inside of the eyelids—than on the white part of the eye.
A thick, sticky discharge, often described as mucopurulent, is commonly present, leading to crusting and the feeling that the eyelids are “stuck together,” especially upon waking. The eyelids frequently appear swollen, and patients may experience tearing, itching, and sensitivity to light (photophobia). A physical examination often reveals enlarged lymph nodes located in front of the ear on the side of the affected eye.
A hallmark sign distinguishing it from other types of conjunctivitis is the presence of small, raised bumps called follicles on the inner surface of the eyelid. These follicles are accumulations of white blood cells responding to the infection. In early stages of Trachoma, the upper inner eyelid shows similar follicular inflammation.
How the Infection Spreads to the Eye
The transmission of Chlamydia trachomatis to the eye occurs through direct or indirect contact with infectious secretions. In developed nations, the most common route is autoinoculation, where the bacteria are transferred from the genital area to the eye via the hands. Genital chlamydia is often asymptomatic, facilitating this transfer. This form of the disease, known as inclusion conjunctivitis, is caused by specific serotypes (D-K) of the bacterium.
The global form of the disease, Trachoma, involves different serotypes (A-C) and is transmitted through contact with eye and nasal discharge. This spread is often linked to poor sanitation and hygiene. The infection is typically carried by young children and transferred via hands, contaminated clothing, and shared towels.
A significant transmission route in endemic, rural communities involves eye-seeking flies, particularly the bazaar fly (Musca sorbens). These flies are mechanical vectors, transferring the bacteria from the eye or nose discharge of one person to another when they feed. The prevalence of this infection is associated with crowded living conditions, inadequate access to clean water, and poor facial cleanliness.
Clinical Diagnosis and Antibiotic Treatment
A physician confirms the diagnosis by testing a sample taken directly from the infected eye once symptoms suggest ocular chlamydia. The most sensitive and specific method is the Nucleic Acid Amplification Test (NAAT), which detects the organism’s genetic material. A clinician gently swabs the inside of the eyelid (the conjunctiva) to collect cells for laboratory analysis.
Treatment requires oral antibiotics, not just topical eye drops, because the infection is systemic and often co-occurs with a genital infection. Standard treatment for adult inclusion conjunctivitis is a single 1-gram dose of oral azithromycin or 100 milligrams of oral doxycycline taken twice daily for 7 to 10 days. The choice of antibiotic depends on factors like patient age and pregnancy status.
Patients must be screened for a co-existing genital infection, and all sexual partners should be tested and treated. Treating the eye alone will not cure the underlying infection and leads to a high risk of recurrence. For Trachoma in endemic regions, a single dose of oral azithromycin is often used in mass drug administration campaigns.
Potential Long-Term Eye Damage
If the ocular chlamydia infection is left untreated or if repeated infections occur, particularly in the case of Trachoma, chronic inflammation can lead to permanent changes in the eyelid structure. This chronic inflammatory response causes the formation of scar tissue within the conjunctiva, especially on the inner surface of the upper eyelid. This is known as conjunctival scarring.
As this scar tissue contracts, it physically distorts the eyelid, causing the eyelid margin to turn inward, a condition called entropion. The mechanical consequence of entropion is trichiasis, where the eyelashes are misdirected and rub constantly against the cornea. This continuous friction causes tiny abrasions and chronic irritation.
The repeated trauma from the in-turned lashes eventually leads to clouding and scarring of the cornea, the clear front window of the eye. This corneal opacification blocks light from entering the eye, resulting in irreversible vision loss and blindness. This progression from inflammation to scarring, trichiasis, and corneal opacity underscores the importance of prompt antibiotic treatment.