Lens and cataract: aldose reductase in diabetic cataract: 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: aldose reductase in diabetic cataract

Sample item

In a lens exposed to prolonged hyperglycaemia, which enzyme converts excess glucose into sorbitol that leads to osmotic swelling?

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

The answer and the reasoning

D. Aldose reductase

Aldose reductase reduces glucose to sorbitol, which cannot leave the lens cells and is slowly metabolised, so water enters, fibres swell and opacities form. This is the basis for studies of aldose reductase inhibitors.

Option by option

  • A. Hexokinase

    Hexokinase phosphorylates glucose for glycolysis and is saturated, but it does not produce sorbitol.

  • B. Sorbitol dehydrogenase

    Sorbitol dehydrogenase converts sorbitol to fructose and is slow, which allows sorbitol to accumulate.

  • C. Galactokinase

    Galactokinase phosphorylates galactose and is deficient in galactokinase deficiency.

  • D. Aldose reductase (correct)

    Correct. Aldose reductase generates sorbitol and the osmotic effect.

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, Aldose reductase. Aldose reductase reduces glucose to sorbitol, which cannot leave the lens cells and is slowly metabolised, so water enters, fibres swell and opacities form.

Why is "Hexokinase" not the answer?

Hexokinase phosphorylates glucose for glycolysis and is saturated, but it does not produce sorbitol.

Why is "Sorbitol dehydrogenase" not the answer?

Sorbitol dehydrogenase converts sorbitol to fructose and is slow, which allows sorbitol to accumulate.

Why is "Galactokinase" not the answer?

Galactokinase phosphorylates galactose and is deficient in galactokinase deficiency.

What concept does this question test?

It tests Lens and cataract: aldose reductase in diabetic cataract in Ophthalmology. This is the basis for studies of aldose reductase inhibitors.

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 Lens and cataract: aldose reductase in diabetic cataract?

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.