Zonule of Zinn

The Zonule of Zinn, also known as the ciliary zonule, is a ring of fibrous strands connecting the ciliary body with the crystalline lens of the eye. These fibers are essential for maintaining the position of the lens and enabling the eye to focus on objects at various distances, a process known as accommodation.

Anatomy

The zonule of Zinn is composed of numerous fine fibers that extend from the ciliary body to the lens capsule. These fibers are primarily made of fibrillin, a glycoprotein that provides structural support. The zonules are divided into two main groups: the anterior and posterior zonules. The anterior zonules attach to the anterior surface of the lens, while the posterior zonules attach to the posterior surface.

Function

The primary function of the zonule of Zinn is to hold the lens in place and facilitate accommodation. When the ciliary muscle contracts, it reduces the tension on the zonules, allowing the lens to become more convex and increasing its refractive power for near vision. Conversely, when the ciliary muscle relaxes, the tension on the zonules increases, flattening the lens for distant vision.

Clinical Significance

Disorders of the zonule of Zinn can lead to various ocular conditions. For example, Marfan syndrome, a genetic disorder affecting connective tissue, can weaken the zonules, leading to lens dislocation or subluxation. Other conditions, such as homocystinuria and Weill-Marchesani syndrome, can also affect the integrity of the zonules.

History

The zonule of Zinn is named after the German anatomist Johann Gottfried Zinn, who first described these fibers in the 18th century. His contributions to the understanding of ocular anatomy have been significant, and his name is also associated with the Zinn's annulus, a ring of fibrous tissue surrounding the optic nerve.

See Also

• Ciliary body
• Crystalline lens
• Accommodation (eye)
• Marfan syndrome
• Homocystinuria
• Weill-Marchesani syndrome