Color-vision abnormalities among patients undergoing tuberculosis treatment

Abstract

Objective: This study determined the incidence of and risk factors for color-vision abnormalities among Filipino patients undergoing directly observed treatment short-course (DOTS) for tuberculosis.

Methods: A prospective single-cohort study involving newly diagnosed patients with category-1 tuberculosis, recruited from DOTS health centers in Manila, was conducted. All patients were given a fixed-dose combination of rifampicin, isoniazid, ethambutol, and pyrazinamide for 60 days, after which treatment was continued with rifampicin and isoniazid for 4 more months. The participants underwent complete eye evaluation including color-vision testing and were followed up every month up to the conclusion of treatment.

Results: Out of 93 patients initially enrolled, 64 completed the prescribed follow-up and constituted the study group. Baseline color vision was normal. After 1 month of therapy, color vision tested with the Ishihara plates remained normal in all patients, but one failed the Farnsworth Panel D 15 and was classified as tritan while 30 (47.88%) failed the Lanthony Desaturated test. The type of abnormality was unclassified in 20 (66.67 %)patients and tritan in 10 (33.3%). Visual acuity remained unchanged from baseline. Repeat testing after ethambutol and pyrazinamide were stopped showed that color vision was normal using the Ishihara plates and the Farnsworth test, while 5 failed the Lanthony test. Of these, 3 were unclassified and 2 were tritan. In the 3rd to 6th months follow-up, no color-vision abnormalities were noted in the 3 tests. The only risk factor identified was age (p = 0.01) with older patients having a higher risk.

Conclusion: The incidence of color-vision abnormalities among patients undergoing DOTS was 47.88% using the Lanthony Desaturated test after an average of 39.66 days on quadruple anti-TB therapy. Age was the only significant risk factor observed. The color-vision abnormalities returned to normal within an average of 37.85 days after discontinuing ethambutol and pyrazinamide.