Conjunctiva and cornea: Demodex blepharitis: 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: Demodex blepharitis

Sample item

An elderly patient has chronic itching of the lid margins. Slit lamp shows waxy cylindrical sleeves clasping the base of the lashes, with lash misdirection but no ulceration. Which organism is implicated?

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

The answer and the reasoning

A. Demodex folliculorum

Demodex mites inhabit the lash follicles, and their waste produces the characteristic cylindrical dandruff, waxy sleeves at the lash base. Lid scrubs with tea tree oil preparations are used for treatment.

Option by option

  • A. Demodex folliculorum (correct)

    Correct. Waxy cylindrical sleeves at the lash roots point to Demodex folliculorum.

  • B. Staphylococcus aureus

    Staphylococcal blepharitis gives brittle fibrinous scales, collarettes and possible ulcers with lash loss, but not waxy sleeves clasping the lashes.

  • C. Moraxella lacunata

    Moraxella causes angular blepharoconjunctivitis with maceration at the canthi.

  • D. Phthirus pubis

    Phthirus pubis causes pubic lice infestation of the lashes with visible nits and adult lice and may cause blood-stained debris.

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 A, Demodex folliculorum. Demodex mites inhabit the lash follicles, and their waste produces the characteristic cylindrical dandruff, waxy sleeves at the lash base.

Why is "Staphylococcus aureus" not the answer?

Staphylococcal blepharitis gives brittle fibrinous scales, collarettes and possible ulcers with lash loss, but not waxy sleeves clasping the lashes.

Why is "Moraxella lacunata" not the answer?

Moraxella causes angular blepharoconjunctivitis with maceration at the canthi.

Why is "Phthirus pubis" not the answer?

Phthirus pubis causes pubic lice infestation of the lashes with visible nits and adult lice and may cause blood-stained debris.

What concept does this question test?

It tests Conjunctiva and cornea: Demodex blepharitis in Ophthalmology. Lid scrubs with tea tree oil preparations are used for treatment.

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 Conjunctiva and cornea: Demodex blepharitis?

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.