This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Adverse Drug Effect, Subject name: Pharmacology
Eye defect by anti Tb drug: 
Select and explain. 
A. Ethambutol, B. Pyrazinamide, C. Rifampicin, D. Isoniazid
A: Ethambutol
Answer: A: Ethambutol 
Explanation: Ans. a. EthambutolRef: Goodman Gilman 13th E/P1074Reversible eye defect in the form of optic neuritis and red-green (green>red) colour blindness can be seen with ethambutol.Hence ophthalmological examination for same is mandatory.These intensity of ocular toxicities are both dose and duration dependent.