How does the eye accommodate for near vision?

The process of accommodation for near vision primarily involves the ciliary muscles. When focusing on objects that are closer, these muscles contract. This contraction releases tension on the zonules (or zonular fibers) that connect the ciliary body to the lens. As a result, the lens becomes thicker and more curved, allowing it to increase its refractive power. This is crucial because near objects require a greater focusing ability than distant objects, which is achieved through this thickening of the lens.

In contrast, other options do not play a direct role in accommodation for near vision. For instance, pupil dilation typically occurs in low-light situations to let more light in, which does not specifically aid in focusing on nearby objects. The retina does not adjust in shape or size to focus; rather, it reacts to the light signals received after the lens has already focused the image. Lastly, the cornea's curvature remains relatively constant and is not adjusted during the accommodation process. Thus, the accurate mechanism for near vision accommodation is the contraction of the ciliary muscles, leading to a thicker lens.