Neuro-ophthalmology and pupils: pharmacological mydriasis: 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 · Neuro-ophthalmology and pupils: pharmacological mydriasis

Sample item

A nurse has a unilaterally dilated pupil of 8 mm that does not react to light. Ptosis and eye movements are normal. After instillation of 1 percent pilocarpine, the pupil stays dilated. What is the cause?

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

The answer and the reasoning

C. Pharmacological blockade by an anticholinergic agent

A pupil that fails to constrict to 1 percent pilocarpine, with normal lid and movements, shows muscarinic blockade of the sphincter, for example from atropine or scopolamine. In a third nerve palsy the denervated sphincter constricts. Adie pupils constrict to dilute pilocarpine.

Option by option

  • A. Adie tonic pupil

    An Adie pupil shows supersensitivity and constricts to dilute pilocarpine.

  • B. Third nerve palsy

    A third nerve palsy would also cause ptosis and a down and out eye, and the pupil would constrict.

  • C. Pharmacological blockade by an anticholinergic agent (correct)

    Correct. Failure to constrict to strong pilocarpine means the sphincter receptors are blocked.

  • D. Horner syndrome

    Horner syndrome gives a small pupil with ptosis.

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, Pharmacological blockade by an anticholinergic agent. A pupil that fails to constrict to 1 percent pilocarpine, with normal lid and movements, shows muscarinic blockade of the sphincter, for example from atropine or scopolamine.

Why is "Adie tonic pupil" not the answer?

An Adie pupil shows supersensitivity and constricts to dilute pilocarpine.

Why is "Third nerve palsy" not the answer?

A third nerve palsy would also cause ptosis and a down and out eye, and the pupil would constrict.

Why is "Horner syndrome" not the answer?

Horner syndrome gives a small pupil with ptosis.

What concept does this question test?

It tests Neuro-ophthalmology and pupils: pharmacological mydriasis in Ophthalmology. In a third nerve palsy the denervated sphincter constricts. Adie pupils constrict to dilute pilocarpine.

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 Neuro-ophthalmology and pupils: pharmacological mydriasis?

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.