Optic neuropathy: ethambutol: practice question

A Ophthalmology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Ophthalmology · Optic neuropathy: ethambutol

Sample item

A patient on antitubercular therapy complains of reduced vision and loss of red-green colour discrimination. Which drug is responsible?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. Ethambutol

Ethambutol causes dose-related retrobulbar optic neuropathy, with central scotoma and red-green defects. Visual acuity and colour vision should be checked at baseline and monthly, and the drug stopped at once.

Option by option

  • A. Ethambutol (correct)

    Correct. Ethambutol is the classic cause.

  • B. Pyrazinamide

    Pyrazinamide causes hepatotoxicity and hyperuricaemia.

  • C. Isoniazid

    Isoniazid rarely causes optic neuritis and mostly peripheral neuropathy.

  • D. Rifampicin

    Rifampicin causes orange body fluids.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Ophthalmology question

What is the answer to this Ophthalmology question?

The best answer is A, Ethambutol. Ethambutol causes dose-related retrobulbar optic neuropathy, with central scotoma and red-green defects.

Why is "Pyrazinamide" not the answer?

Pyrazinamide causes hepatotoxicity and hyperuricaemia.

Why is "Isoniazid" not the answer?

Isoniazid rarely causes optic neuritis and mostly peripheral neuropathy.

Why is "Rifampicin" not the answer?

Rifampicin causes orange body fluids.

What concept does this question test?

It tests Optic neuropathy: ethambutol in Ophthalmology. Visual acuity and colour vision should be checked at baseline and monthly, and the drug stopped at once.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Optic neuropathy: ethambutol?

Group the red eye by what to examine and what the pupil does. Then use the flashcards and the other Ophthalmology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.