Question

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).

Assertion (A) : Bilateral cataract is very common in patients with uncontrolled diabetes mellitus.
Reason (R) : It occurs due to glycosylation of \(\alpha\)-crystallin protein of lens.

In light of the above statements, choose the correct answer from the options given below.

• A. Both (A) and (R) are true and (R) is the correct explanation of (A).
• B. Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
• C. (A) is true but (R) is false.
• D. (A) is false but (R) is true.

Hint:

Diabetic cataracts develop via a dual mechanism: osmotic damage (sorbitol accumulation) and structural protein damage (non-enzymatic glycation of lens crystallin proteins).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Chronic, poorly controlled hyperglycemia in diabetes mellitus results in secondary vascular, neurological, and ocular complications.

Step 2: Detailed Explanation:
1. Assertion (A): Patients with poorly controlled diabetes mellitus are highly susceptible to developing bilateral cataracts at an earlier age due to the metabolic stress on the lens. Thus, Assertion (A) is true.
2. Reason (R): Under chronic hyperglycemia, glucose enters the lens cells and undergoes two deleterious processes:
- Conversion to sorbitol (via the polyol pathway), which causes osmotic swelling and cell lysis.
- Non-enzymatic glycosylation (glycation) of lens structural proteins, particularly \(\alpha\)-crystallin.
This glycation causes the proteins to undergo conformational changes, cross-link, and form insoluble aggregates, causing the lens to lose its optical transparency and develop a cataract.
Thus, the glycation of \(\alpha\)-crystallin directly explains the pathogenesis of diabetic cataracts. Both (A) and (R) are true, and (R) is the correct explanation of (A).

Step 3: Final Answer:
The correct option is 1, which corresponds to both statements being true and (R) being the correct explanation of (A).