What are the other Names for this Condition? (Also known as/Synonyms)

• Eye Tuberculosis
• Mycobacterium Tuberculosis Infection of Eye
• Ocular TB

What is Ocular Tuberculosis? (Definition/Background Information)

• Tuberculosis (TB) is a contagious infection caused by the bacterium Mycobacterium tuberculosis. The disease is characterized by the formation of nodules (tubercles) in the affected tissues. Compromised immunity due to age or disease, malnutrition, living in unsanitary conditions, poverty, and some pre-existing health conditions are risk factors for being diagnosed with tuberculosis
• The infection may develop in the lungs and spread to other parts of the body, such as the bones and joints, gastrointestinal tract, skin, and larynx, among other regions. This is known as disseminated tuberculosis (or extrapulmonary tuberculosis); when involvement of the eye is noted, it is termed as Ocular Tuberculosis
• It is reported that nearly 60% of disseminated tuberculosis may not present an involvement of the lung; and, Ocular Tuberculosis is frequently not an outcome of pulmonary tuberculosis. Thus, Ocular TB can be either from direct infection of the eye by the tuberculosis bacteria (primary infection), or from spread of the infection through sinus cavity fluids, or via blood from other body regions (i.e., disseminated TB leading to Eye TB; thus termed secondary infection)
• The manifestation of Ocular Tuberculosis is most commonly noted as uveitis (tuberculosis uveitis), an eye condition that can potentially cause severe vision impairment and blindness, if not promptly diagnosed and managed accordingly
• In general, the signs and symptoms of Ocular Tuberculosis may involve several components of the eye and present blurred or decreased vision, eye redness, eye pain, and sensitivity to light. Delayed diagnosis and treatment may result in severe complications, such as formation of nodules or lesions, optic nerve atrophy, and irreversible eye damage
• The treatment for Ocular Tuberculosis is achieved via the universally recommended and standardized antituberculous therapy (ATT), which can bring about a complete recovery from tuberculosis. However, it is important to complete the course of medication that often lasts several months to years
• The prognosis of Ocular Syphilis is dependent upon various factors such as early diagnosis and administration of medication, associated systemic symptoms, and complications; but, the prognosis is generally good with adequate treatment

Who gets Ocular Tuberculosis? (Age and Sex Distribution)

• Ocular Tuberculosis can occur in any age group, but generally older adults and infants are more vulnerable to the disease
• It can affect both males and females and no racial or ethnic predilection is observed
• However, most cases of tuberculosis (over 95% of them) are reported from  the underdeveloped or developing countries of the world - from Asia, Africa, and South American nations

What are the Risk Factors for Ocular Tuberculosis? (Predisposing Factors)

Ocular Tuberculosis develops from the advancement and spread of tuberculosis to the eye in many cases. The risk factors for tuberculosis generally include:

• Elderly adults with weak immune system and infant children
• Individuals with weak immune function such as due to HIV infection or AIDS
• The presence of other health conditions/diseases that make it difficult for the body to fight a bacterial infection (such as uncontrolled diabetes)
• Drug and alcohol abuse
• Poverty, poor standards of living, and overcrowding conditions/settlements
• Malnutrition, especially among children; poor nutrition
• Prolonged stress can weaken the immune system increasing the risk
• Use of immunosuppressant medication

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Ocular Tuberculosis? (Etiology)

• Tuberculosis is a contagious bacterial infection that usually occurs in the lung, but can also occur in other areas of the body; it is a multi-system disease
• It is caused by Mycobacterium tuberculosis (MTB), a pathogenic bacterium, which is acquired through the inhalation of respiratory droplets from the cough or sneeze of an infected individual
• In many, the infection is known to affect the eye and cause Ocular Tuberculosis, even before involvement of the lungs or other body systems and organs are noted

Currently, it is unclear if eye involvement is from a direct bacterial infection or occurring as part of an immunologic hypersensitivity reaction of the body. This is an important consideration for treatment of the disease. Nevertheless, primary infections when the eye is directly affected are quite uncommon.

What are the Signs and Symptoms of Ocular Tuberculosis?

The signs and symptoms of Ocular Tuberculosis may vary between individuals and occur slowly over a period of time. It may include:

• Reduced vision; progressive vision loss
• Blurred vision
• Light-sensitivity (photophobia)
• Redness of the eyes
• Itching and burning sensation in the eye
• Headache
• Eye floaters: The individuals experience illusions that some small objects such as spots, hairs, or strings are moving in the eye
• Eye pain, in some cases
• Mass-like lesion on the eyelid
• Flashes in the eye: Sudden appearance of ‘flashing’ bright lights
• Uveitis or inflammation of the uvea is most commonly associated with tuberculosis infection. All forms of uveitis - posterior (most commonly), intermediate, anterior, or panuveitis may be noted
• In children and infrequently in adults, orbital involvement is noted
• Both unilateral (one eye) and bilateral (both eyes) involvement are noted; in some cases, the infection moves from one eye to involve the other, over a period of many months and years

The incidence (percentage) of uveitis resulting from TB infection varies from between 0.5% to 11.4% depending on whether it is a developed nation or a developing nation respectively.

When tuberculosis bacterium directly affects the eye, it can result in lesion formations on the eyelid, conjunctiva, cornea, and sclera. Secondary infection of the eye mostly presents the involvement of uvea, retina, and optic nerve.

The symptoms of tuberculosis that involves the lungs may include persistent cough, breathing difficulty, fever and chills, and chest pain.

How is Ocular Tuberculosis Diagnosed?

The diagnosis of Ocular Tuberculosis is reportedly difficult due to the wide-ranging eye presentations that are noted. Besides, many cases of Ocular Tuberculosis are the result of extrapulmonary infections (absence of lung involvement).

Some of the exams and tests that may help the healthcare provider arrive at a diagnosis of Ocular Tuberculosis include:

• Physical examination and analysis of previous medical history including assessment of living conditions, history of any contact with TB infected individuals, infected family members, etc.
• Eye examination by an eye specialist (ophthalmologists)
• Tuberculosis skin and blood tests
• Interferon-gamma release assay (IGRA): Blood test that can help in diagnosing TB infection
• Chest X-ray, if needed
• Other blood tests that may include:
  • To check for the presence of antibodies in blood
  • Blood culture for infections
  • Complete blood count (CBC) with differential
  • Erythrocyte sedimentation rate (ESR)
• Antibody titer in aqueous humor and vitreous humor fluid samples; use of polymerase chain reaction (PCR) techniques
• Tissue biopsy: A tissue biopsy may be performed and sent to a laboratory for a pathological examination. The pathologist examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis
• Fundoscopic (ophthalmoscopic) examination by an eye specialist, who examines the back part of the eye (or the fundus)
• Visual acuity test using a special and standardized test chart (Snellen chart)
• Slit-lamp examination: Examination of the eye structure using a special instrument called a slit-lamp. In this procedure, the pupils are dilated and the internal eye structure is examined
• Tonometry: Measurement of intraocular pressure or eye fluid pressure, especially to detect conditions such as glaucoma
• Fundus fluorescein angiography (FFA): In this technique, the eye blood vessels are examined using a fluorescein dye
• Fundus autofluorescence (FAF): It is a non-invasive diagnostic technique to examine the fundus of the eye without using a fluorescent dye by a specialized fundus camera
• Indocyanine green (ICG) angiography: It is used to examine the blood vessels of the choroid using a dye, called indocyanine green, particularly to study the choroid
• B-scan ultrasonography: Special ultrasound scan of the eye through a non-invasive diagnostic tool, to assess health of eye structures
• Electroretinogram (ERG): It is a technique to measure electrical activities in the retinal cells
• Optical coherence tomography (OCT) of eye: It is an ocular imaging technique to visualize the eye structure

A differential diagnosis may be undertaken to eliminate the following conditions:

• Choroidal granuloma or chorioretinitis due to various infections, such as syphilis, leprosy, varicella zoster, and herpes simplex virus, and non-infectious causes including sarcoidosis and Vogt-Koyanagi-Harada disease
• Granulomatous uveitis that arises from infectious factors, such as syphilis, toxoplasmosis, and fungal etiologies, and non-infectious factors including sarcoidosis and serpiginous choroidopathy

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Ocular Tuberculosis?

A few complications of Ocular Tuberculosis include:

• Vitreitis or vitreous inflammation, which may result in the development of epiretinal membranes
• Formation of granulomas (benign nodules) is associated with anterior uveitis that slowly affects the iris and cornea too
• Involvement of the choroid may result in nodule formation (single or multiple), multifocal choroiditis (inflammation of the choroid), subretinal abscess, and endophthalmitis (infectious inflammation of the vitreous and aqueous fluid regions)
• Optic nerve atrophy: A permanent visual impairment that occurs when the optic nerve is damaged
• Cystoid macular edema
• Peripheral retinal neovascularization: It can result in loss of partial vision
• Retinal detachment: An eye condition wherein the retina gets separated from the eye structures that holds the retinal layers together
• Peripheral retinal vasculitis: Inflammation of the retinal arterioles (small blood vessels)
• Keratoconjunctivitis due to corneal infection, presenting pain and enlargement of local lymph nodes
• Scleritis: Inflammation of the sclera causing severe eye injury and vision loss
• Neovascular glaucoma: A condition that can cause blindness due to higher intraocular pressure
• Cataract formation: When the lens of the eye becomes clouded and cause vision loss
• Vitreous hemorrhage or the leakage of blood into the vitreous humor
• Severely impaired vision and complete blindness
• Medication side effects from long-term treatment

Complications observed due to the underlying (pulmonary) tuberculosis infection, if any present, may include coughing-up blood, meningitis (mostly in children), and lung damage.

How is Ocular Tuberculosis Treated?

Prompt, early diagnosis and appropriate treatment is very important for Ocular Tuberculosis. This can help decrease the risk for complications and further progression of tuberculosis. An important consideration for treatment is whether the disease developed due to a direct involvement of eye by the infectious pathogen or from a delayed hypersensitive response of the body.

The following treatments may be considered by the healthcare expert:

• Antituberculous therapy (ATT): Administration of a combination of antibiotics for a period determined by the healthcare provider
• Symptomatic and supportive therapy for tuberculosis, if needed
• Use of oral or systemic corticosteroids: Administration of corticosteroids is currently being debated by the scientific community. It is considered based on each individual’s specific case; steroid therapy may help improve or worsen the condition, or even lead to its recurrence. Systemic steroids should only be started after 24-48 hours after starting ATT
• Symptomatic treatment of eye manifestations
• Long-term follow-up may be necessary to prevent recurrent infections, in some cases

How can Ocular Tuberculosis be Prevented?

To reduce the incidence of Ocular Tuberculosis, the following preventative measures may be considered for tuberculosis:

• Avoiding close physical contact with untreated individuals with tuberculosis (TB); getting treated, in case of contact with tuberculosis-infected individuals
• Undertaking early diagnosis and treatment of tuberculosis
• Getting vaccinated against TB
• Healthcare workers and individuals in close contact with the TB patients should follow strict hygiene and preventative measures
• Getting treatment for any underlying medical condition(s) that may decrease immunity in the individual

Regular medical screening at periodic intervals with tests and physical examinations are crucial and highly recommended (for prevention and early diagnosis of recurrences).

What is the Prognosis of Ocular Tuberculosis? (Outcomes/Resolutions)

The prognosis of Ocular Tuberculosis depends on the early recognition and appropriate treatment of tuberculosis.

• With early diagnosis and treatment (including completing the prescribed medication course), the infection may be completely resolved and vision restored
• However, the overall prognosis is also dependent on the underlying condition and the severity of the symptoms and complications presented
• In individuals with poor immune function, the prognosis may be guarded

Additional and Relevant Useful Information for Ocular Tuberculosis:

Please visit our Eye & Vision Health Center for more physician-approved health information:

http://www.dovemed.com/health-topics/vision-center/