Pupil: Horner testing: 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 · Pupil: Horner testing

Sample item

A patient with suspected Horner syndrome has no dilatation on 4 percent cocaine drops and also none on hydroxyamphetamine. Where is the lesion?

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

The answer and the reasoning

C. Postganglionic (third order) neuron

Cocaine fails to dilate any Horner pupil, confirming the diagnosis. Hydroxyamphetamine releases noradrenaline from intact postganglionic terminals, so failure to dilate localises the lesion to the postganglionic neuron.

Option by option

  • A. Parasympathetic pathway

    The parasympathetic pathway is not involved.

  • B. Preganglionic neuron

    Pre-ganglionic lesions dilate with hydroxyamphetamine.

  • C. Postganglionic (third order) neuron (correct)

    Correct. No response to hydroxyamphetamine indicates a postganglionic lesion.

  • D. Central first order neuron

    Central lesions also dilate with hydroxyamphetamine.

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 C, Postganglionic (third order) neuron. Cocaine fails to dilate any Horner pupil, confirming the diagnosis.

Why is "Parasympathetic pathway" not the answer?

The parasympathetic pathway is not involved.

Why is "Preganglionic neuron" not the answer?

Pre-ganglionic lesions dilate with hydroxyamphetamine.

Why is "Central first order neuron" not the answer?

Central lesions also dilate with hydroxyamphetamine.

What concept does this question test?

It tests Pupil: Horner testing in Ophthalmology. Hydroxyamphetamine releases noradrenaline from intact postganglionic terminals, so failure to dilate localises the lesion to the postganglionic neuron.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Pupil: Horner testing?

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.