Tuberculosis is an infectious disease that is prevalent throughout the world, and the infection with highest annual rate of mortality (now just behind COVID 19) with 9.9 million people infected in 2020 (WHO). Caused by the Mycobacterium tuberculosis bacteria, which is airborne (inhalation of micro-droplets), the infection is not, however, tantamount to illness: it is estimated that one quarter of the global population is infected but is not sick, which means they are not infectious. Between 5 and 10% of infected people will develop the illness throughout their lives due to risk factors such as malnutrition, smoking, diabetes, a chemotherapy-weakened immune system, and, above all, HIV.

Active tuberculosis fundamentally affects the lungs (85%), but it can impact any organ. In immunocompetent individuals, extrapulmonary tuberculosis accounts for only 15 to 20% of cases.

Ocular Tuberculosis

Ocular tuberculosis is very uncommon: 2 to 30% of cases of TB cases are due to blood borne dissemination of the germ. Only 60% of patients with ocular tuberculosis get a positive QuantiFERON-TB test or a chest X-ray showing lesions from the disease. Tuberculosis can affect any part of the eye's structure, from the eyelids to the optic nerve. Common symptoms include scleritis and uveitis (which resist corticosteroid treatment) and choroiditis. The disease’s mechanism is twofold: through being directly infected by the germ or by a persistent immune reaction without the actual presence of the germ.

Getting a diagnosis is complex. To do so, an attempt is made to isolate the bacteria using microbiological techniques (such as PCR) from the aqueous humour or vitreous sample, although with poor results. The ophthalmologist’s experience and skill are key when it comes to a suspected diagnosis of the disease, which often needs to be treated without further positive results. It is a diagnosable and curable disease in the right hands.

In the Pulmonology and/or Internal Medicine Departments we make the guidelines for the systemic study and treatment, we provide antituberculosis drugs and, if the disease persists due to immunoallergic mechanisms we use appropriate immunosuppressive treatments.

Dr. Ramón Rey, internist at the Barraquer Ophthalmology Centre