Lens and cataract: IOL power after myopic LASIK: 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 · Lens and cataract: IOL power after myopic LASIK

Sample item

A 60-year-old had myopic LASIK 12 years ago. Cataract surgery uses an IOL power from standard keratometry, and on day 1 the refraction is +2.5 D. What explains the surprise?

AAxial length was measured too shortBPosterior capsule opacificationCCorneal ectasiaDKeratometry overestimated corneal power, so the lens was too weak

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

The answer and the reasoning

D. Keratometry overestimated corneal power, so the lens was too weak

After myopic LASIK the central cornea is flattened and the usual anterior-to-posterior curvature ratio is changed, so standard keratometry overestimates power. The formula then selects an IOL that is too weak, giving a hyperopic surprise. Special formulae or corneal topography data are required.

Option by option

A. Axial length was measured too short
A short axial length would give a hyperopic error but is not the established cause here.
B. Posterior capsule opacification
Capsule opacification blurs vision and does not alter spherical error.
C. Corneal ectasia
Ectasia would steepen the cornea and cause myopia, not hyperopia.
D. Keratometry overestimated corneal power, so the lens was too weak (correct)
Correct. Overestimated corneal power led to a weaker IOL and hyperopia.

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.

Questions about this Ophthalmology question

What is the answer to this Ophthalmology question?

The best answer is D, Keratometry overestimated corneal power, so the lens was too weak. After myopic LASIK the central cornea is flattened and the usual anterior-to-posterior curvature ratio is changed, so standard keratometry overestimates power.

Why is "Axial length was measured too short" not the answer?

A short axial length would give a hyperopic error but is not the established cause here.

Why is "Posterior capsule opacification" not the answer?

Capsule opacification blurs vision and does not alter spherical error.

Why is "Corneal ectasia" not the answer?

Ectasia would steepen the cornea and cause myopia, not hyperopia.

What concept does this question test?

It tests Lens and cataract: IOL power after myopic LASIK in Ophthalmology. The formula then selects an IOL that is too weak, giving a hyperopic surprise. Special formulae or corneal topography data are required.

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 Lens and cataract: IOL power after myopic LASIK?

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.