Anatomy and physiology of the eye: horizontal raphe: 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 · Anatomy and physiology of the eye: horizontal raphe

Sample item

A patient with early glaucoma has an arcuate field defect that stops abruptly along the horizontal meridian on the nasal side, forming a nasal step. Which retinal feature explains the sharp border?

AVariation in lamina cribrosa pore sizeBFoveal avascular zoneCDecussation of nasal fibres at the chiasmDHorizontal raphe separating superior and inferior arcuate nerve fibre bundles

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

The answer and the reasoning

D. Horizontal raphe separating superior and inferior arcuate nerve fibre bundles

Arcuate fibres from the temporal retina arch above and below the fovea and do not cross the temporal horizontal raphe. A defect confined to one bundle therefore respects the horizontal midline. Lamina cribrosa pore size explains susceptibility of the poles, not the horizontal border.

Option by option

A. Variation in lamina cribrosa pore size
Larger pores at the poles explain which areas are damaged first, but not the horizontal step.
B. Foveal avascular zone
The foveal avascular zone is a vascular feature that has no bearing on arcuate bundle borders.
C. Decussation of nasal fibres at the chiasm
Chiasmal decussation produces vertical, not horizontal, field borders.
D. Horizontal raphe separating superior and inferior arcuate nerve fibre bundles (correct)
Correct. The raphe keeps the superior and inferior bundles apart, giving a horizontal edge.

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.

Questions about this Ophthalmology question

What is the answer to this Ophthalmology question?

The best answer is D, Horizontal raphe separating superior and inferior arcuate nerve fibre bundles. Arcuate fibres from the temporal retina arch above and below the fovea and do not cross the temporal horizontal raphe.

Why is "Variation in lamina cribrosa pore size" not the answer?

Larger pores at the poles explain which areas are damaged first, but not the horizontal step.

Why is "Foveal avascular zone" not the answer?

The foveal avascular zone is a vascular feature that has no bearing on arcuate bundle borders.

Why is "Decussation of nasal fibres at the chiasm" not the answer?

Chiasmal decussation produces vertical, not horizontal, field borders.

What concept does this question test?

It tests Anatomy and physiology of the eye: horizontal raphe in Ophthalmology. A defect confined to one bundle therefore respects the horizontal midline. Lamina cribrosa pore size explains susceptibility of the poles, not the horizontal border.

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 Anatomy and physiology of the eye: horizontal raphe?

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.