Retina: vitelliform dystrophy electrophysiology: 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: vitelliform dystrophy electrophysiology

Sample item

A 9-year-old boy with a family history of a dominantly inherited macular disease has a well-circumscribed yellow lesion at the fovea, like a sunny-side-up egg. His full-field ERG is normal. Which test is characteristically abnormal?

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

The answer and the reasoning

D. Electro-oculogram with a reduced Arden ratio

Best vitelliform macular dystrophy is dominantly inherited and affects the RPE, so the electro-oculogram light rise is abnormal with a low Arden ratio while the ERG stays normal. The disease is caused by BEST1 mutations. Vision may remain good for years.

Option by option

  • A. Visual evoked potential with delayed P100

    A delayed P100 is seen with optic nerve demyelination, not with a primary macular RPE disorder.

  • B. Goldmann perimetry with a ring scotoma

    Ring scotomas are seen in retinitis pigmentosa and in drug maculopathy, not in this condition.

  • C. Dark adaptometry with a raised rod threshold

    Raised rod threshold on dark adaptometry fits generalised rod disease such as retinitis pigmentosa.

  • D. Electro-oculogram with a reduced Arden ratio (correct)

    Correct. A reduced Arden ratio on EOG with a normal ERG is the hallmark of Best disease.

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, Electro-oculogram with a reduced Arden ratio. Best vitelliform macular dystrophy is dominantly inherited and affects the RPE, so the electro-oculogram light rise is abnormal with a low Arden ratio while the ERG stays normal.

Why is "Visual evoked potential with delayed P100" not the answer?

A delayed P100 is seen with optic nerve demyelination, not with a primary macular RPE disorder.

Why is "Goldmann perimetry with a ring scotoma" not the answer?

Ring scotomas are seen in retinitis pigmentosa and in drug maculopathy, not in this condition.

Why is "Dark adaptometry with a raised rod threshold" not the answer?

Raised rod threshold on dark adaptometry fits generalised rod disease such as retinitis pigmentosa.

What concept does this question test?

It tests Retina: vitelliform dystrophy electrophysiology in Ophthalmology. The disease is caused by BEST1 mutations. Vision may remain good for years.

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 Retina: vitelliform dystrophy electrophysiology?

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.