Anatomy and physiology of the eye: blood-aqueous barrier: 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: blood-aqueous barrier

Sample item

Fluorescein given intravenously does not appear in the normal anterior chamber, although it leaks freely into the stroma of the ciliary body. Where are the tight junctions that keep it out of the aqueous located?

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

The answer and the reasoning

D. Between non-pigmented ciliary epithelial cells

The blood-aqueous barrier is formed mainly by tight junctions between the non-pigmented ciliary epithelial cells, with the non-fenestrated iris vessels contributing. Ciliary body capillaries are fenestrated, so the stroma is permeable. In uveitis this barrier breaks down and protein appears in the aqueous as flare.

Option by option

  • A. Between cells of the trabecular meshwork

    The meshwork is an outflow pathway and does not exclude plasma proteins from the aqueous.

  • B. Between pigmented ciliary epithelial cells

    Pigmented epithelial cells are joined by gap junctions and do not make the barrier.

  • C. Between endothelial cells of the ciliary body capillaries

    Ciliary capillaries are fenestrated and leak, which is why the barrier lies further inward.

  • D. Between non-pigmented ciliary epithelial cells (correct)

    Correct. The non-pigmented epithelium bears the tight junctions that form the barrier.

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, Between non-pigmented ciliary epithelial cells. The blood-aqueous barrier is formed mainly by tight junctions between the non-pigmented ciliary epithelial cells, with the non-fenestrated iris vessels contributing.

Why is "Between cells of the trabecular meshwork" not the answer?

The meshwork is an outflow pathway and does not exclude plasma proteins from the aqueous.

Why is "Between pigmented ciliary epithelial cells" not the answer?

Pigmented epithelial cells are joined by gap junctions and do not make the barrier.

Why is "Between endothelial cells of the ciliary body capillaries" not the answer?

Ciliary capillaries are fenestrated and leak, which is why the barrier lies further inward.

What concept does this question test?

It tests Anatomy and physiology of the eye: blood-aqueous barrier in Ophthalmology. Ciliary body capillaries are fenestrated, so the stroma is permeable. In uveitis this barrier breaks down and protein appears in the aqueous as flare.

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: blood-aqueous barrier?

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.