Anatomy Animation

Mechanics of Lens Movement

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Accomodation is the ability of the Lens to adjust in order to keep objects focused on the Retina.

The process of Accomodation contains three main components:

Lens
Ciliary Muscle
Suspensory Ligaments

The Ciliary Muscle is part of the ciliary body which is a special extension of the Choroid layer. The Ciliary Body is made up of two major components:

Ciliary Muscle
a capillary network that produces the Aqueous Humor.

The Ciliary Muscle is a ring of smooth muscle to which the suspensory ligaments are attached. The suspensory ligaments connect the Lens to the muscle. When the Ciliary Muscle is relaxed the ligaments are taut, and the Lens is at its weakest. In a normal eye a weak Lens is needed in focusing on distant objects. When the ciliary muscle is contracted the suspensory ligaments become less taut. This produces a rounder, stronger Lens. In a normal eye a strong Lens is needed to bring near objects into focus.

The autonomic nervous system controls the contraction and relaxation of the Ciliary Muscle. Sympathetic nerve fiber stimulation causes relaxation of the muscle, whereas parasympathetic stimulation causes muscle contraction.