Neuro-ophthalmology and pupils: junction scotoma: 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.

Try it

Ophthalmology · Neuro-ophthalmology and pupils: junction scotoma

Sample item

Perimetry shows a central scotoma in the left eye and a superotemporal field defect in the right eye. Where is the lesion?

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

The answer and the reasoning

C. At the junction of the left optic nerve and the chiasm

A lesion at the junction of one optic nerve and the chiasm gives a central or paracentral scotoma in the ipsilateral eye and a superotemporal defect in the other eye, because inferonasal fibres from the fellow eye loop into the affected nerve.

Option by option

  • A. The left optic radiation in the temporal lobe

    A temporal radiation lesion causes a contralateral superior quadrantanopia.

  • B. The right occipital pole

    An occipital pole lesion causes a congruous homonymous central scotoma.

  • C. At the junction of the left optic nerve and the chiasm (correct)

    Correct. This combination localises to the nerve-chiasm junction.

  • D. The right optic tract

    An optic tract lesion causes an incongruous homonymous hemianopia.

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.

More Ophthalmology questions

Questions about this Ophthalmology question

What is the answer to this Ophthalmology question?

The best answer is C, At the junction of the left optic nerve and the chiasm. A lesion at the junction of one optic nerve and the chiasm gives a central or paracentral scotoma in the ipsilateral eye and a superotemporal defect in the other eye, because inferonasal fibres from the fellow eye loop into the affected nerve.

Why is "The left optic radiation in the temporal lobe" not the answer?

A temporal radiation lesion causes a contralateral superior quadrantanopia.

Why is "The right occipital pole" not the answer?

An occipital pole lesion causes a congruous homonymous central scotoma.

Why is "The right optic tract" not the answer?

An optic tract lesion causes an incongruous homonymous hemianopia.

What concept does this question test?

It tests Neuro-ophthalmology and pupils: junction scotoma in Ophthalmology. The correct option holds because: Correct. This combination localises to the nerve-chiasm junction.

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: junction scotoma?

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.