Zonula ciliaris

Zonula Ciliaris or the ciliary zonule (also known as Zonule of Zinn) is a ring of fibrous strands connecting the ciliary body of the eye with the lens of the eye. These fibers are crucial in holding the lens in place and play a significant role in the eye's ability to focus on objects at various distances, a process known as accommodation.

Structure

The zonula ciliaris is composed of fine, transparent fibers that originate from the ciliary body, specifically the ciliary processes, and extend to the lens, attaching around its equator. These fibers are made up of a protein called fibrillin, which provides both strength and elasticity. The zonula ciliaris divides into two main components: the anterior and posterior zonular fibers. The anterior fibers attach to the lens closer to the equator, while the posterior fibers attach more posteriorly, aiding in the stability and positioning of the lens.

Function

The primary function of the zonula ciliaris is to suspend the lens in the eye and maintain its position as the eye focuses on objects at different distances. During the process of accommodation, the ciliary muscle contracts, releasing tension on the zonular fibers, and allowing the lens to become more spherical, increasing its power to focus on near objects. Conversely, when the ciliary muscle relaxes, tension on the zonular fibers increases, flattening the lens for focusing on distant objects.

Clinical Significance

Alterations or defects in the zonula ciliaris can lead to lens dislocation (ectopia lentis), which can significantly affect vision. Conditions such as Marfan syndrome and Homocystinuria are associated with weakened zonular fibers, increasing the risk of lens dislocation. Surgical procedures involving the lens, such as cataract surgery, also require careful manipulation of the zonular fibers to prevent damage and ensure the stability of the lens implant.

See Also

• Ciliary body
• Lens
• Accommodation (eye)
• Cataract surgery
• Marfan syndrome
• Homocystinuria