Name the type of lenses required by the persons for the correction of their defect of vision called presbyopia. Write the structure of the lenses commonly used for the correction of this defect giving reason for such designs.
Generated by claude-sonnet-4-6 · 2026-06-15 06:53 · grounding rag
Model Answer
Persons with presbyopia require bi-focal lenses.
A common bi-focal lens consists of both concave and convex lenses. The upper portion is a concave lens (for distant vision) and the lower portion is a convex lens (for near vision). This design is used because presbyopia patients often suffer from both myopia and hypermetropia simultaneously.
Source: Chapter 10, Section 10.2(c) – Presbyopia
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Explanation
- The key term examiners look for is bi-focal lenses — write it clearly.
- Mention both parts of the bi-focal lens with their positions (upper/lower) and functions (distant/near vision). These are two separate marking points.
- The reason (person suffers from both myopia and hypermetropia) earns the logic mark. Don't skip it.