Conjunctiva and cornea: pellucid marginal degeneration: 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 · Conjunctiva and cornea: pellucid marginal degeneration

Sample item

A 32-year-old has gradually worsening against-the-rule astigmatism. Slit lamp shows a crescentic band of inferior peripheral thinning with an intact, protruding cornea above it. What is the typical topography pattern?

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

The answer and the reasoning

D. Crab-claw pattern with steepening above the thinning

Pellucid marginal degeneration shows a crescent of thinning 1-2 mm from the inferior limbus, and topography gives a classic crab-claw or butterfly pattern. Unlike keratoconus, the maximum protrusion is above the thinned band.

Option by option

  • A. Central flattening with peripheral steepening

    Central flattening with a steeper periphery is an oblate shape seen after myopic laser.

  • B. Diffuse global steepening

    Diffuse global steepening suggests keratoglobus.

  • C. Inferior steepening with an asymmetric bow tie

    An inferior asymmetric bow tie is the pattern in keratoconus.

  • D. Crab-claw pattern with steepening above the thinning (correct)

    Correct. A crab-claw pattern is characteristic of pellucid marginal degeneration.

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 D, Crab-claw pattern with steepening above the thinning. Pellucid marginal degeneration shows a crescent of thinning 1-2 mm from the inferior limbus, and topography gives a classic crab-claw or butterfly pattern.

Why is "Central flattening with peripheral steepening" not the answer?

Central flattening with a steeper periphery is an oblate shape seen after myopic laser.

Why is "Diffuse global steepening" not the answer?

Diffuse global steepening suggests keratoglobus.

Why is "Inferior steepening with an asymmetric bow tie" not the answer?

An inferior asymmetric bow tie is the pattern in keratoconus.

What concept does this question test?

It tests Conjunctiva and cornea: pellucid marginal degeneration in Ophthalmology. Unlike keratoconus, the maximum protrusion is above the thinned band.

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 Conjunctiva and cornea: pellucid marginal degeneration?

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.