What is the recommended treatment for ocular tuberculosis?

Treatment of Ocular Tuberculosis

Ocular tuberculosis should be treated with a standard 4-drug anti-tuberculosis regimen consisting of isoniazid, rifampin, pyrazinamide, and ethambutol for 2 months, followed by isoniazid and rifampin for an additional 4 months, for a total duration of 6 months. 1

Initial Phase (First 2 Months)

The intensive phase must include all four first-line drugs 1, 2:

• Isoniazid (5 mg/kg, up to 300 mg daily) 3
• Rifampin (10 mg/kg, up to 600 mg daily) 3
• Pyrazinamide (35 mg/kg, up to 2 g daily) 3
• Ethambutol (15 mg/kg daily) 1, 3

The fourth drug (ethambutol) can only be omitted if drug susceptibility testing confirms full susceptibility to isoniazid and rifampin, or in previously untreated patients from areas with documented low isoniazid resistance (<4% primary resistance) 1, 4. However, given that 71% of UK ocular TB patients were born outside the UK, ethambutol should routinely be included until susceptibility results are available 5.

Continuation Phase (Months 3-6)

After completing the initial 2-month phase, continue with 1:

• Isoniazid and Rifampin daily for 4 additional months

This brings the total treatment duration to 6 months for standard ocular tuberculosis 1, 2.

Treatment Duration Modifications

Extend treatment to 9 months if 1:

• Pyrazinamide cannot be tolerated or was not included in the initial phase
• In this case, give ethambutol for the initial 2 months with isoniazid and rifampin, then continue isoniazid and rifampin for 7 additional months

Extend treatment to 12 months if 6, 3:

• The patient has cerebral tuberculoma (a specific form of CNS involvement)
• Use the same 4-drug initial phase for 2 months, then rifampin and isoniazid for 10 additional months

Corticosteroid Adjunctive Therapy

Oral corticosteroids should be considered as adjunctive therapy 5, 2:

• In the UK prospective study, 60% of ocular TB patients received a reducing course of oral steroids with good outcomes (83% complete resolution at 1 year) 5
• While evidence for ocular TB specifically is limited, corticosteroids have demonstrated clear benefit in tuberculous pericarditis and CNS tuberculosis 1, 6
• A reasonable approach is prednisolone 60 mg daily initially, with gradual tapering over several weeks 6, 3

Special Considerations

Drug-Resistant Tuberculosis

For isoniazid-resistant TB: Add a later-generation fluoroquinolone (such as moxifloxacin or levofloxacin) to a 6-month regimen of rifampin, ethambutol, and pyrazinamide 1, 6

For rifampin-resistant TB: Use a 9-month regimen of isoniazid, streptomycin, pyrazinamide, and ethambutol for 2 months, followed by isoniazid, streptomycin, and pyrazinamide for 7 months 1

For multidrug-resistant TB (resistant to both isoniazid and rifampin): Consultation with a TB expert is mandatory, and treatment must include at least 5 effective drugs, typically including a later-generation fluoroquinolone and an injectable agent (preferably amikacin or streptomycin, not kanamycin) 1

Monitoring

Clinical and ophthalmologic monitoring should occur 2:

• At the end of the initial 2-month phase
• At the end of treatment (6-9 months)
• Visual acuity should be monitored throughout due to ethambutol's potential ocular toxicity 1

Diagnostic Approach

Before initiating treatment, screen for tuberculosis in any patient with 2:

• Uveitis of unknown etiology
• Recurrent uveitis not responding to conventional therapy
• Ocular findings highly suggestive of TB (such as choroidal tubercles, serpiginous-like choroiditis)

Screening includes tuberculin skin testing, interferon-gamma release assay (IGRA), chest imaging, and complete medical history 2.

Common Pitfalls

• Do not omit ethambutol in the initial phase unless drug susceptibility is confirmed, as this risks treatment failure with resistant organisms 1, 4
• Do not use shorter than 6-month regimens for ocular TB, as this is an extrapulmonary manifestation requiring full-duration therapy 1, 4
• Do not delay treatment while awaiting culture results if clinical suspicion is high, as delay can result in permanent vision loss 2
• Monitor for ethambutol toxicity with regular visual acuity and color vision testing, particularly at the 15 mg/kg dose 1