<prompt> Colour blindness in ethambutol toxicity:Red blueRed greenBlueRed green blue  <response>: Ans. b Red greenRef : A.K. Khurana 6th ed. 1329 Optic neuritis, the most serious adverse effect reported due to ethambutol toxicity, typically presents as reduced visual acuity, central scotoma, and loss of the ability to see green or, less commonly, red. Please refer to pharmacology section for detailed discussion on ATT and their side effect. 