Final answer:
The age-related vision defect is known as presbyopia, which causes difficulty in focusing on close objects due to the reduced elasticity of the lens and weakening of the eye muscles.
Step-by-step explanation:
The vision defect due to age is known as presbyopia. Presbyopia is a common vision problem associated with aging in which the eye gradually loses its ability to focus on close objects. As people age, the lens in the eye may become less elastic, and the muscles controlling the lens may weaken, resulting in difficulty focusing on objects that are nearby.
Symptoms such as eyestrain, trouble seeing in dim light, and difficulties with reading small print tend to appear between the ages of 40 and 50. Though corrective lenses can be used to help with near vision, surgical options for correcting presbyopia have not been as successful as those for other refractive errors like myopia (nearsightedness) and hyperopia (farsightedness).