Concept:Cataract is the eye condition in which the lens becomes cloudy, blocking light and reducing vision.
Explanation:The lens of the eye is normally clear, allowing light to pass through to the retina.
In cataract, the lens tissue changes and forms cloudy areas, making vision blurred or hazy.
This clouding is often caused by aging, injury, or certain genetic conditions.
Presbyopia relates to difficulty focusing on near objects due to loss of lens flexibility.
Glaucoma involves increased pressure in the eye damaging the optic nerve.
Astigmatism is caused by an irregularly shaped cornea or lens.
Therefore, the defect specifically due to cloudy areas in the lens is cataract.
Answer:C. cataract