Neuro-ophthalmology and pupils: Uhthoff phenomenon: 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: Uhthoff phenomenon

Sample item

A 30-year-old woman recovering from optic neuritis notices that her vision blurs after a hot bath and during exercise, and clears when she cools down. What is this phenomenon called?

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

The answer and the reasoning

B. Uhthoff phenomenon

Uhthoff phenomenon is transient worsening of vision with a rise in body temperature in demyelinated optic nerves, because conduction in damaged fibres fails with heat. It is common in multiple sclerosis. It is not a new relapse.

Option by option

  • A. Purkinje shift

    Purkinje shift is the change in colour sensitivity as light fades.

  • B. Uhthoff phenomenon (correct)

    Correct. Heat-induced temporary blurring after demyelination is Uhthoff phenomenon.

  • C. Marcus Gunn phenomenon

    Marcus Gunn phenomenon is the pupillary defect or the jaw-winking ptosis.

  • D. Pulfrich phenomenon

    Pulfrich phenomenon is an illusion of depth from unequal conduction delay between the eyes.

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 B, Uhthoff phenomenon. Uhthoff phenomenon is transient worsening of vision with a rise in body temperature in demyelinated optic nerves, because conduction in damaged fibres fails with heat.

Why is "Purkinje shift" not the answer?

Purkinje shift is the change in colour sensitivity as light fades.

Why is "Marcus Gunn phenomenon" not the answer?

Marcus Gunn phenomenon is the pupillary defect or the jaw-winking ptosis.

Why is "Pulfrich phenomenon" not the answer?

Pulfrich phenomenon is an illusion of depth from unequal conduction delay between the eyes.

What concept does this question test?

It tests Neuro-ophthalmology and pupils: Uhthoff phenomenon in Ophthalmology. It is common in multiple sclerosis. It is not a new relapse.

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 Neuro-ophthalmology and pupils: Uhthoff phenomenon?

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.