Six-months Versus Nine-months ATT for Ocular TB

1. Tubercular uveitis (TBU) is a major cause of intraocular inflammation in TB-endemic countries. It has several clinical manifestations affecting nearly every tissue in the eye. Histopathological studies of TBU have revealed presence of paucibacillary mycobacterial infection and granulomatous infection in enucleated eyes. Unlike TB in other organ systems, microbiological evidence of TB is rarely found in ocular fluids that are sampled from TBU eyes. Hence, the diagnosis of TBU is based on presence of characteristic clinical signs, ancillary evidence of systemic TB infection and exclusion of non-TB entities. Active pulmonary TB, however, is rarely found in TBU patients.
2. While there are no agreed management guidelines for TBU, several studies, both from TB-endemic and non-endemic countries, have supported the utility of anti-TB therapy (ATT) in the resolution of ocular inflammation, and prevention of recurrence. Delay in initiation of ATT has led to chronic inflammation and prolonged visual impairment in TBU [6]. These studies have typically been retrospective and have included patients with wide range of clinical presentations, based on diagnostic criteria, described above. Majority of these studies have used adjunctive corticosteroids and/or immunosuppressants along with ATT. The duration of ATT in these studies have varied from 6-24 months. A meta-analysis of these studies revealed that 84% (95% CI 79-89) of the patients receiving ATT had no recurrence of inflammation during the follow-up period.

AIM of the study: To compare the efficacy of 6-month with that of 9-month ATT, for the treatment of clinically diagnosed tubercular posterior uveitis (TPU).

Study design: An international, multicenter, prospective, randomized, observer masked-study in three centres spread across India, Myanmar and Thailand.

Patient assesment: This included detailed history of ocular and systemic illnesses, history of TB contact in past, ETDRS best corrected visual acuity (converted from Snellens, if ETDRS unavailable), intraocular pressure by Goldmann applanation tonometry, slit lamp biomicroscopy, and indirect ophthalmoscopy. Fundus photography (seven-field or wide-field, if available) was performed for all patients. Other ocular imaging such as fluorescien angiography, fundus autofluorescence, optical coherence tomography (OCT), OCT-angiography or indocyanine green angiography, were performed as per specific requirements in individual cases. All patients with clinical signs compatible with TPU, were investigated for complete blood counts, erythrocyte sedimentation rate, HIV, VDRL, TST and contrast enhanced computed tomography (CECT) of thorax. If CECT is not available at a centre, then a digital X-ray of the chest was considered in lieu of it. IGRA was performed in conjunction with TST, or in patients with strong suspicion of TPU but negative TST. Additional investigations were performed at the discretion of the investigator to rule out non-TB diagnosis.

Follow-up evaluation were done at 2 weeks, 1 month (+/-1 week), 2 months (+/-2 weeks), 4 months (+/-2 weeks), 6 months (+/-4 weeks), 9 months (+/-4weeks), and then 3 monthly (+/-4 weeks), till one year after completion of ATT. The one-year cut-off limit has been chosen, since most recurrences have been known to occur within one year after the completion of ATT (at least in case of pulmonary TB). Ocular and systemic evaluation, including ocular imaging (as described above), will be performed for each visit.