Overview:

• Ocular tuberculosis (TB) is a clinical disease caused by Mycobacterium tuberculosis.
• It is known as the "great imitator" of ocular pathologies due to its ability to mimic various eye conditions.

Historical Context:

• Choroidal tubercles were anatomically described in 1855 and identified with an ophthalmoscope in 1867.
• TB was identified in the eye in 1883, one year after the discovery of the organism.
• TB has become rare in Western nations, primarily due to advancements in laboratory diagnostic tests.

Global Impact:

• More than 1.7 billion people are estimated to be infected with TB.
• It is the leading cause of death from a single infectious agent worldwide and the primary cause of death among persons living with HIV.

Modes of Ocular TB:

1. Direct Ocular Infection (Primary Ocular TB):
   • Contact with the lids or conjunctiva from an exogenous source.
2. Hematogenous Spread (Secondary Ocular TB):
   • Spread from a pulmonary focus or another extrapulmonary site via the bloodstream.
3. Hypersensitivity Reaction:
   • Reaction in eye structures following exposure to TB antigens.

Pathogenesis:

• M. tuberculosis spreads by aerosolized droplets and is inhaled into the respiratory alveoli.
• Alveolar macrophages ingest the bacteria, but M. tuberculosis evades eradication by inhibiting the fusion of the phagolysosome.
• Bacteria-laden macrophages spread through the lymphatic and venous systems to oxygen-rich regions like the lungs and eyes.

Epidemiology:

• According to the WHO, about 10.4 million people fall ill, and 1.8 million people die from TB annually.