Which part connects the crystalline lens to the ciliary muscles?

The suspensory ligaments, also known as zonules, are the structures that connect the crystalline lens to the ciliary muscles. These fine fibers play a crucial role in the process of accommodation, which is the lens's ability to change shape for focusing on objects at varying distances.

When the ciliary muscles contract, they reduce tension on the suspensory ligaments. This allows the lens to become thicker and more rounded for near vision. Conversely, when the ciliary muscles relax, the tension on the ligaments increases, causing the lens to flatten for distance vision. This mechanism is vital for clear vision across different distances and is an important function of the eye.

The other options do not serve this function: the optic nerve transmits visual information from the retina to the brain, retinal neurons are responsible for processing visual signals, and corneal fibers relate to the cornea's structure and sensation but do not have a direct connection to the lens or ciliary muscles. This makes the suspensory ligaments the correct answer for the question regarding the connection between the crystalline lens and the ciliary muscles.