Which condition is primarily characterized by the inability to focus on nearby objects?

The condition primarily characterized by the inability to focus on nearby objects is presbyopia. This condition occurs as people age, typically starting in their mid-40s, and results from a gradual loss of elasticity in the eye’s lens, making it harder to accommodate or adjust focus on close objects.

In contrast, myopia (nearsightedness) involves difficulty seeing distant objects clearly while close objects can be seen well, thus primarily affecting distance vision rather than near vision. Astigmatism is caused by an irregular shape of the cornea or lens, leading to blurred vision at all distances, not solely near vision. Hyperopia, or farsightedness, involves difficulty focusing on nearby objects as well, but it is caused by the eye being too short or the lens being too weak, which is not the same mechanism as presbyopia's age-related changes. Thus, presbyopia is most accurately associated with the difficulty focusing on nearby objects due to its specific characteristics related to aging.