Q1. [1] § 10.2 DEFECTS OF VISION AND THEIR CORRECTION
An old person is suffering from an eye defect caused by weakening of ciliary muscles and diminishing flexibility of the eye lens. If the defect of vision is 'a' which can be corrected by lens 'b', then 'a' and 'b' respectively are :
- (A) hypermetropia and convex lens
- (B) presbyopia and bifocal lens
- (C) myopia and concave lens
- (D) myopia and bifocal lens
Previously asked in CBSE board exam
2025 31/1/1 Q14
Generated by claude-sonnet-4-6 · 2026-06-15 06:51 · grounding rag
Model Answer
(B) presbyopia and bifocal lens
Presbyopia is caused by gradual weakening of ciliary muscles and diminishing flexibility of the eye lens (in old age), and it is corrected using bifocal lenses.
Source: Chapter 10, Section 10.2(c) – Presbyopia
Explanation
The question directly describes the cause of presbyopia — weakening of ciliary muscles and reduced flexibility of the eye lens. The textbook states this defect is corrected by bifocal lenses (containing both concave and convex portions). Options A and C describe different defects entirely; Option D incorrectly pairs myopia with bifocal lenses.
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