The defect of the eye lens which occurs as a result of weak ciliary muscles is called

Analyze the question: We need the eye defect caused by weak ciliary muscles (and loss of lens flexibility).

Concept: The ciliary muscles change the shape of the eye lens so it can focus on objects at different distances (accommodation). When we look at near objects, the ciliary muscles contract and the lens becomes thicker (more curved). With age, the ciliary muscles weaken and the lens becomes less elastic, so the eye cannot accommodate for near objects.

Checking each option:

• A. Astigmatism: The cornea or lens is unevenly curved, so lines in one direction are focused differently from those in another. It is not caused by weak muscles.
• B. Hypermetropia (long-sightedness): The eyeball is too short or the lens is too weak in power, so near objects are blurred. It is usually present from birth or due to eye shape, not specifically weak ciliary muscles.
• C. Myopia (short-sightedness): The eyeball is too long or the lens too powerful, so distant objects are blurred.
• D. Presbyopia: An age-related defect where the ciliary muscles weaken and the lens hardens, so the eye cannot focus on near objects. This matches the question.
• E. Spherical aberration: A lens defect where rays through the edges and the centre focus at different points. It is not a defect of the eye caused by muscles.

Answer: Presbyopia, option D.

Correction: Reading glasses with converging (convex) lenses, or bifocals, correct presbyopia.

Exam tip: Link "Presbyopia" with "Elderly" (both start with P-E... "Presbyter" means elder). If an age-related weakening of the muscles is mentioned, choose presbyopia. Remember too: myopia is corrected with a diverging lens, and hypermetropia with a converging lens.