When the human eye loses its power of accomodation, the defect is known as

Analyze the question: The question asks for the name of the eye defect that occurs when the eye loses its power of accommodation. Accommodation is the ability of the eye lens to change its focal length (by the ciliary muscles changing the lens thickness) so that objects at different distances can be focused clearly on the retina.

Explain the concept:

• Short sightedness (myopia): The eye focuses distant objects in front of the retina. It is corrected with a diverging (concave) lens.
• Long sightedness (hypermetropia): The eye focuses near objects behind the retina, usually because the eyeball is too short or the lens is too weak. It is corrected with a converging (convex) lens.
• Astigmatism: The cornea or lens is unevenly curved, so light focuses unevenly. This gives blurred or distorted vision in some directions. It is corrected with a cylindrical lens.
• Presbyopia: The lens becomes less flexible with age and the ciliary muscles weaken, so the eye loses its power of accommodation. Older people find it hard to focus on near objects such as print. It is corrected with bifocal or reading glasses.

Solution:

1. The key phrase is "loses its power of accommodation".
2. Loss of accommodation is caused by the lens hardening and losing elasticity, which usually happens with ageing.
3. This condition is called presbyopia.

Note that option D (long sightedness) is a tricky distractor. Presbyopia produces similar symptoms, since near objects are hard to see. However, long sightedness is caused by the eyeball's shape or lens power, not primarily by loss of accommodation. The question's wording points directly to presbyopia.

Answer: Option B, presbyopia.

Exam tip: Link "presbyopia" with "presbyter" (elder), because it comes with age. Whenever you see "loss of accommodation" or "old age" in an eye question, think presbyopia.