Tuberculosis of eye:

Tuberculosis (TB) is a contamination brought about by Mycobacterium tuberculosis, which can cause sickness in different organs all through the body, including the eye. The expression "ocular TB" depicts a disease by the M. tuberculosis species that can influence any piece of the eye (intraocular, shallow, or encompassing the eye), with or without foundational inclusion. "Optional ocular TB" is characterized as ocular contribution because of cultivating by hematogenous spread from a removed site or direct attack by touching spread from adjoining structures, similar to the sinus or cranial hole.

Clinical appearances of ocular TB differ, which represents a test for analysis. The authoritative finding of TB is set up by disconnection of M tuberculosis bacilli from ocular tissues. Notwithstanding, on the grounds that this is hard to accomplish, the determination of ocular TB is regularly assumed within the sight of interesting ocular discoveries in mix with any of the accompanying:

• Fundamental discoveries reliable with TB contamination
• Positive interferon gamma discharge test
• Positive tuberculin skin test in asymptomatic people

Also, clinical reaction to against TB treatment further backings an assumed finding of ocular TB

Symptoms

Hazy vision, and light affectability might be the solitary revealed manifestations. Different grievances may incorporate cerebral pain, redness of the eye, floaters, or glimmers. Patients may likewise be asymptomatic.

Diagnosis

The modern strategy for ocular TB determination is screening for tuberculosis in any uveitis of obscure etiology, repetitive or not reacting to regular treatment; in ocular discoveries profoundly reminiscent of ocular TB and before immunosuppression (especially biologic specialists). TB screening in these cases incorporates tuberculosis skin testing and interferon gamma testing, alongside complete clinical history, ophthalmologic assessment and chest imaging.

Tuberculosis of eye

Ocular TB broadly refers to inflammation in the eye (uveitis) that can be related to infection with the tuberculosis bacilli, Mycobacterium tuberculosis. The ocular inflammation can form various patterns such as retinal vasculitis or serpiginous-like choroiditis (that progresses like a serpent) depending on the eye tissue primarily affected by the infection. Such patterns are also seen in various other forms of infectious and non-infectious diseases.

Causes

Three modes of the disease have been described for ocular tuberculosis:

• Direct ocular infection from an exogenous source, e.g., contact with the lids or conjunctiva (primary ocular TB).
• Hematogenous spread of M. tuberculosis from a pulmonary focus or extrapulmonary site (secondary ocular TB).
• Hypersensitivity reaction in structures of the eye after exposure to TB antigens.

Signs and Symptoms 

Ocular TB is a great imitator of various ocular pathologies. A provider should consider many possible findings. The following are clinical signs of ocular TB described according to the anatomical location:

Extraocular TB

Orbit: The involvement of the orbit is most common in children. Patients may present with proptosis, eyelid swelling, intermittent periorbital swelling, headache, epistaxis, decreased vision, visual field abnormalities, chemosis, Marcus Gunn pupil, epiphora, and increased orbital resistance to retropulsion.

Eyelids: The involvement of the eyelids is also most common in children. Eyelid TB can present as lupus vulgaris with reddish-brown “apple-jelly” nodules. It can also appear as a lid abscess, chronic blepharitis, or atypical chalazion.

Lacrimal Gland: TB involvement presents as symptomatic dacryoadenitis, indistinguishable from other bacterial infections.

Conjunctiva: Primary tuberculous conjunctivitis is a chronic disease that eventually leads to scarring. Patients present with ocular redness, discomfort, and mucopurulent discharge with regional lymphadenopathy.

Cornea: It may present as phlyctenular keratoconjunctivitis (an inflammatory nodule at the limbus) or interstitial keratitis. The phlyctenule is believed to be a hypersensitivity reaction to TB antigen, and it may erode the epithelia and create photophobia, redness, and tearing. Tuberculous interstitial keratitis presents as a unilateral sectoral, peripheral stromal infiltrate with vascularization.

Sclera: Tuberculous scleritis is challenging to diagnose outside the context of active systemic TB. Scleritis is usually chronic, does not respond to anti-inflammatory treatment, can be necrotizing, and usually presents anteriorly; posterior sclera involvement is rare.

Intraocular TB

Anterior Uveitis: It is usually granulomatous, may present as iris granulomas with broad-based posterior synechiae, and Koeppe and Busacca nodules, mutton-fat keratic precipitates on the posterior aspect of the cornea, and/or complicated cataract. In children, band keratopathy can occur.

Intermediate Uveitis: Usually presents with unilateral or bilateral asymmetry and appears similar to par planitis. Features include mild-to-moderate vitritis with snowball, snow banking, peripheral vascular sheathing, and/or peripheral retinochoroidal granulomas.

Posterior Uveitis: It is the most common presentation of ocular TB. Common patterns include a solitary tubercle, multiple tubercles, miliary choroidal tubercles, and multifocal choroiditis . Tubercles are white-yellow nodules that typically reside in the posterior pole. Usually, fewer than five are present but maybe as many as 50 or 60. Non-contiguous, multifocal choroiditis may progress to a diffuse, contiguous pattern called a serpiginous-like lesion. This lesion resembles serpiginous choroiditis (multifocal serpiginous choroiditis); however, in contrast to classic serpiginous choroiditis, it does not extend to the disc, tends to spare the fovea even when the macula is involved, and it is more multifocal and pigmented. The vitreous in tuberculous serpiginous-like choroiditis is usually inflamed, whereas, in serpiginous choroiditis, there is no vitreous inflammation.

Retina: TB of the retina is almost always a result of the choroidal extension. Rarely does hematogenous spread affect the retina before the choroid. Retinal lesions may take the form of either focal tubercles, subretinal abscesses, or diffuse retinitis. Occlusive retinal vasculitis may occur and induce neovascularization. Exudative retinal hemorrhagic periphlebitis with uveitis is highly suggestive of intraocular TB. 

Optic Nerve: Optic neuropathy develops either from direct infection induced by TB or a hypersensitivity reaction to the infectious agent. It may present as an optic nerve tubercle, papillitis, or papilledema. Optic nerve swelling and disk edema have been reported with posterior tuberculous scleritis.

Endophthalmitis: Tubercular subretinal abscesses may burst into the vitreous cavity and present as endophthalmitis or panophthalmitis.

Diagnosis

Clinical manifestations of ocular TB vary, which poses a challenge for diagnosis. The definitive diagnosis of TB is established by isolation of M tuberculosis bacilli from ocular tissues. However, because this is difficult to achieve, the diagnosis of ocular TB is often presumed in the presence of suggestive ocular findings in combination with any of the following:

• Systemic findings consistent with TB infection
• Positive interferon gamma release assay
• Positive tuberculin skin test in asymptomatic individuals

In addition, clinical response to anti-TB treatment (ATT) further supports a presumed diagnosis of ocular TB.

Inactive: Evaluate under §4.88c or §4.89 of this part, whichever is appropriate.