Glaucoma: ISNT rule: 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 · Glaucoma: ISNT rule

Sample item

In a healthy optic disc, which is the correct order of neuroretinal rim thickness from thickest to thinnest?

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

The answer and the reasoning

B. Inferior, superior, nasal, temporal

The ISNT rule states that the rim is thickest inferiorly, then superiorly, nasally and thinnest temporally. Violation of the rule suggests glaucomatous rim loss.

Option by option

  • A. Temporal, nasal, superior, inferior

    This reverses the order.

  • B. Inferior, superior, nasal, temporal (correct)

    Correct. This is the ISNT order.

  • C. Nasal, temporal, inferior, superior

    This arrangement is not the normal pattern.

  • D. Superior, inferior, temporal, nasal

    This arrangement is not the normal pattern.

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, Inferior, superior, nasal, temporal. The ISNT rule states that the rim is thickest inferiorly, then superiorly, nasally and thinnest temporally.

Why is "Temporal, nasal, superior, inferior" not the answer?

This reverses the order.

Why is "Nasal, temporal, inferior, superior" not the answer?

This arrangement is not the normal pattern.

Why is "Superior, inferior, temporal, nasal" not the answer?

This arrangement is not the normal pattern.

What concept does this question test?

It tests Glaucoma: ISNT rule in Ophthalmology. Violation of the rule suggests glaucomatous rim loss.

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 Glaucoma: ISNT rule?

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.