How does presbyopia primarily affect vision?

Presbyopia primarily affects vision by causing difficulty in focusing on nearby objects. This condition is a natural part of aging and typically becomes noticeable in individuals around the age of 40 and older. It results from the gradual loss of elasticity in the eye's lens, making it harder to change shape and focus on objects that are close. This loss of flexibility means that tasks which require close-up vision, like reading or sewing, become challenging, requiring the use of reading glasses or similar aids.

The other options do not directly relate to the primary effects of presbyopia. Difficulty seeing at night is more associated with conditions such as night blindness or cataracts. Increased sensitivity to light can be related to various eye conditions or medications, but it is not a hallmark of presbyopia. The appearance of floaters typically occurs due to changes in the vitreous humor of the eye and is not indicative of the focusing issues characteristic of presbyopia. Thus, choice B accurately reflects the core impact of this age-related vision change.