HomeOcular involvement is a rare manifestation of EPTB. Although commonly encountered in the context of disseminated disease, ocular TB more typically occurs without clinically apparent systemic disease.255,302 In low TB-incidence settings such as Canada, ophthalmologist evaluation of uveitis of unknown etiology with positive immune markers for TB infection (identified through a tuberculin skin test (TST) or interferon-gamma release assay (IGRA)) often leads to a TB center referral for consideration of empiric anti-TB therapy.303,304
TB can affect all parts of the eye and may result from hematogenous spread or adjacent structure extension. Ocular TB can be subcategorized by involvement of the peri-ocular, superficial and intra-ocular structures of the eye, which may occur in isolation or overlap. Intra-ocular TB (IOTB) is the most common form of ocular TB and predominantly manifests as uveitis, primarily involving the vascular posterior portion of the eye (choroid). IOTB may occur in one or both eyes, with variable symptoms ranging from blurred vision to ophthalmalgia, conjunctivitis and vision loss.302 The pathophysiology of IOTB remains incompletely characterized but is posited to involve direct infection of the eye or immune-mediated hypersensitivity reaction triggered by TB infection elsewhere in the body.305
The clinical overlap between IOTB and other, more common infectious and noninfectious causes of uveitis pose a significant diagnostic challenge. Whereas ophthalmic exam findings of choroidal granulomas, occlusive retinal vasculitis and multifocal serpiginoid choroiditis have been proposed as specific to IOTB in high TB-incidence settings, the transferability of these findings to low-incidence setting has been questioned.302,306 Confirmation of IOTB (culture, molecular or pathologic) is rarely achieved, given the risks associated with ocular sampling and generally low diagnostic yield of such samples when obtained.307,308 Therefore, a presumptive diagnosis of IOTB is often made based upon ophthalmic exam findings, epidemiologic risk factors for TB exposure and positive immune markers of TB infection (TST and/or IGRA) in the absence of alternate cause.309,310 This approach will over-estimate those with IOTB compared with those diagnosed based on polymerase chain reaction (PCR) ocular sampling (46.9% vs 37.7%) or TB culture confirmation at another site (3.8%).310–313
3.9.1. Ocular TB treatment
Consensus guidance has recently been published summarizing clinical evaluation and treatment of ocular TB.311 Given the treatable nature of ocular TB and risk of vision loss with treatment delay, initiation of anti-TB therapy should not be delayed once adequate work-up is complete.304,312 Given that IOTB diagnosis is typically indirect and highly dependent on eye exam findings, clear communication with the TB care provider regarding ophthalmic findings and degree of clinical suspicion for IOTB is essential to ensuring timely and appropriate management.
While 9 or more months of therapy has been proposed to reduce relapse, particularly with evidence of persistent inflammatory changes, intra-ocular inflammatory response to effective therapy may be delayed and ongoing infection indistinguishable from hypersensitivity-associated inflammation.303,304,310,312–317
The role of ocular or systemic anti-inflammatories remains controversial and, when used, should be under the guidance and follow-up of an ophthalmologist.304,318 TB preventative therapy should only be used when alternate etiology of ocular disease has been confirmed and is otherwise indicated.311 EMB can be safely used as part of standard anti-TB therapy for intra-ocular TB, assuming close follow-up to monitor for signs of optic neuropathy, particularly in those with risk factors.311,319
Recommendation
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We conditionally recommend 6 months of standard anti-TB therapy for drug-susceptible (suspected or confirmed) intra-ocular TB (poor evidence).
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