Visual field changes in patients receiving antitubercular therapy

Objective
Tuberculosis is a global health challenge with one-third of the world's population infected by it. Although ocular side effects of Anti-tubercular drugs are well known, the patients generally report late in the course which can result in irreversible vision loss. The purpose of this study was to study the visual field changes during the time course of anti-tubercular therapy(ATT).
Methods
A total of 48 patients were studied in this prospective type of study. All patients newly diagnosed with TB and started on treatment were included in the study. Baseline examination which included visual acuity, color vision, anterior segment, IOP, Amsler grid, fundus, and visual field test were performed before starting ATT and at 6-month follow-up.
Results
The mean age of the study population was 35.90 ± 10.2 years. 35 (72.9%) were males and 13 (27.1%) females. 32(66.6%) had pulmonary TB and the rest 16 (33.3%) had extrapulmonary TB. MDR TB was diagnosed in 27 (56.3%) of the patients with the rest 21 (43.8%) being drug sensitive. The baseline examination was normal in all 48 patients. 3(6.3%) out of 45 patients presented with visual complaints after the treatment initiation. Altogether 7 patients out of 48, had visual field defects at the 6-month follow-up. The incidence of visual field defects in our study was 14.6% with the value being significant (0.016). 8.3% had peripheral constriction of visual fields, 2.1% with Severe generalized depression of visual fields and 2.1% with central scotoma. Out of the 45 patients with no visual complaints at 6-month follow-up, 4 (8.33%) showed peripheral field constriction.
Interpretation
Visual field defects caused by ATT can precede clinical symptoms. Visual field evaluation can be an important tool for the early detection of optic neuropathy in patients receiving ATT in clinical settings where Visual evoked potential testing and RNFL-OCT are not available.
Keywords: Mycobacterium tuberculosis, Drug toxicity, DOTS, visual field defects, toxic optic neuropathy, Ethambutol, Linezolid