Retina: cone dystrophy: 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 · Retina: cone dystrophy

Sample item

A 20-year-old has slowly progressive central vision loss, photophobia and poor colour vision with a nearly normal fundus early on. The ERG shows a reduced photopic response with a preserved scotopic response. What is the diagnosis?

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

The answer and the reasoning

D. Cone dystrophy

Cone dystrophy causes loss of central acuity, colour vision and photophobia, with an abnormal photopic ERG. Retinitis pigmentosa affects rods first and causes night blindness. Optic neuritis gives pain and an afferent defect with a normal ERG.

Option by option

  • A. Retinitis pigmentosa

    Retinitis pigmentosa gives night blindness and a reduced scotopic ERG.

  • B. Congenital stationary night blindness

    Congenital stationary night blindness is a nonprogressive night vision problem.

  • C. Optic neuritis

    Optic neuritis has a normal ERG and a different time course.

  • D. Cone dystrophy (correct)

    Correct. Reduced photopic ERG with preserved scotopic response indicates cone dysfunction.

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 D, Cone dystrophy. Cone dystrophy causes loss of central acuity, colour vision and photophobia, with an abnormal photopic ERG.

Why is "Retinitis pigmentosa" not the answer?

Retinitis pigmentosa gives night blindness and a reduced scotopic ERG.

Why is "Congenital stationary night blindness" not the answer?

Congenital stationary night blindness is a nonprogressive night vision problem.

Why is "Optic neuritis" not the answer?

Optic neuritis has a normal ERG and a different time course.

What concept does this question test?

It tests Retina: cone dystrophy in Ophthalmology. Retinitis pigmentosa affects rods first and causes night blindness. Optic neuritis gives pain and an afferent defect with a normal ERG.

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 Retina: cone dystrophy?

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.