Ocular tuberculosis is a form of extrapulmonary tuberculosis, meaning it occurs outside the lungs. It results from an infection by Mycobacterium tuberculosis bacteria that affects any part of the eye or its surrounding tissues. The condition can be a direct, active infection in the eye or an immunological reaction to tubercular antigens elsewhere in the body. This disease is a serious condition that can threaten vision and may run a chronic course if untreated, with periods of worsening symptoms and remission.
Manifestations and Symptoms
The presentation of ocular tuberculosis is highly variable because the infection can impact nearly any tissue within the eye. Common complaints include blurred vision, “floaters” or spots in the field of vision, eye pain, redness, and increased sensitivity to light. Some individuals may not experience noticeable symptoms, especially if the infection is in the peripheral areas of the eye.
Because the bacteria can affect different ocular structures, it can lead to several specific conditions. One of the most frequent is uveitis, an inflammation of the uvea, which is the eye’s middle layer. Other presentations include choroiditis, an inflammation of the choroid layer beneath the retina, or retinal vasculitis, which is inflammation of the retinal blood vessels. The wide range of symptoms means ocular TB often mimics other eye diseases, creating a challenge for timely identification.
Connection to Systemic Tuberculosis
Ocular tuberculosis is typically a secondary complication of a tuberculosis infection elsewhere in the body. The eye becomes infected through hematogenous spread, where Mycobacterium tuberculosis travels from a primary site, most often the lungs, through the bloodstream. The bacteria then seed in the highly vascular tissues of the eye. This can occur even when the initial lung infection is latent and not causing respiratory symptoms.
A significant portion of individuals with ocular TB may not have a concurrently diagnosed pulmonary disease, meaning eye symptoms can be the first sign of a widespread infection. The eye infection itself is not contagious and cannot be spread through contact with the eye. However, the affected individual may have an active, contagious form of pulmonary tuberculosis that requires management.
The Diagnostic Process
Diagnosing ocular tuberculosis is complex, as no single test can definitively confirm it. While isolating M. tuberculosis bacteria from an ocular tissue sample is the gold standard, it is often difficult to achieve. Clinicians therefore rely on a “presumptive diagnosis” by evaluating clinical evidence from multiple sources.
The process begins with an ophthalmologic examination to look for characteristic signs of inflammation, like choroidal granulomas or occlusive retinal vasculitis. This exam is combined with tests for systemic TB, such as the tuberculin skin test (TST) or an Interferon-Gamma Release Assay (IGRA) blood test. Imaging tests, like a chest X-ray or CT scan, are also used to find evidence of lung involvement.
Treatment Protocols
The treatment for ocular tuberculosis is the same as the regimen for pulmonary tuberculosis, centered on anti-tuberculosis therapy (ATT). This protocol involves a combination of several antibiotic drugs taken for several months up to a year or more. The extended duration is necessary to ensure the complete eradication of the slow-growing Mycobacterium tuberculosis bacteria.
Alongside ATT, corticosteroids are frequently prescribed as an adjunct therapy to control inflammation within the eye. By reducing swelling and the immune response in ocular tissues, corticosteroids help prevent permanent structural damage and preserve vision. This combined approach is standard for achieving a positive outcome.