Neuro-ophthalmology and pupils: light-near dissociation compared: 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: light-near dissociation compared

Sample item

Two patients show light-near dissociation. One has small irregular pupils after neurosyphilis. The other, a teenager with a pineal tumour, has mid-dilated pupils and impaired upgaze. How does the second pupil picture differ from the first?

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

The answer and the reasoning

A. The pupils are larger than in Argyll Robertson pupils

Both conditions spare the near response while the light reflex is lost, but the pretectal damage in the dorsal midbrain leaves the pupils mid-dilated. Argyll Robertson pupils are small and irregular. Upgaze palsy and convergence-retraction nystagmus accompany the midbrain lesion.

Option by option

  • A. The pupils are larger than in Argyll Robertson pupils (correct)

    Correct. Dorsal midbrain pupils are mid-dilated, whereas Argyll Robertson pupils are small.

  • B. The pupils are always unequal

    Anisocoria is not required for the dorsal midbrain picture.

  • C. The pupils do not constrict to near

    Constriction to near is preserved in both conditions.

  • D. The pupils react briskly to light

    A brisk light reaction would contradict light-near dissociation.

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, The pupils are larger than in Argyll Robertson pupils. Both conditions spare the near response while the light reflex is lost, but the pretectal damage in the dorsal midbrain leaves the pupils mid-dilated.

Why is "The pupils are always unequal" not the answer?

Anisocoria is not required for the dorsal midbrain picture.

Why is "The pupils do not constrict to near" not the answer?

Constriction to near is preserved in both conditions.

Why is "The pupils react briskly to light" not the answer?

A brisk light reaction would contradict light-near dissociation.

What concept does this question test?

It tests Neuro-ophthalmology and pupils: light-near dissociation compared in Ophthalmology. Argyll Robertson pupils are small and irregular. Upgaze palsy and convergence-retraction nystagmus accompany the midbrain lesion.

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: light-near dissociation compared?

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.