Refraction: duochrome test: 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.

Try it

Ophthalmology · Refraction: duochrome test

Sample item

During the duochrome test, a patient sees letters on the red background more clearly. What does this suggest?

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

The answer and the reasoning

C. Under-minused or over-plussed, so more minus is needed

Red light is refracted least and focuses behind green. If red is clearer, the overall focus lies in front of the retina, so the lens needs more minus or less plus. The endpoint is equal clarity on both.

Option by option

  • A. Colour blindness

    The test is not a colour deficiency test.

  • B. Perfect correction

    Equal clarity indicates a perfect correction.

  • C. Under-minused or over-plussed, so more minus is needed (correct)

    Correct. Red clearer means the image falls in front of the retina and more minus is needed.

  • D. Over-minused, so more plus is needed

    Green clearer would call for more plus.

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.

More Ophthalmology questions

Questions about this Ophthalmology question

What is the answer to this Ophthalmology question?

The best answer is C, Under-minused or over-plussed, so more minus is needed. Red light is refracted least and focuses behind green.

Why is "Colour blindness" not the answer?

The test is not a colour deficiency test.

Why is "Perfect correction" not the answer?

Equal clarity indicates a perfect correction.

Why is "Over-minused, so more plus is needed" not the answer?

Green clearer would call for more plus.

What concept does this question test?

It tests Refraction: duochrome test in Ophthalmology. If red is clearer, the overall focus lies in front of the retina, so the lens needs more minus or less plus. The endpoint is equal clarity on both.

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 Refraction: duochrome test?

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.