The Zonules of Zinn are thousands of tiny, thread-like ligaments that pull your eye's lens to help you focus.

The Zonules of Zinn are named after German anatomist and botanist Johann Gottfried Zinn, who first described them in detail in his 1755 publication, Descriptio anatomica oculi humani. These delicate fibers are composed primarily of fibrillin, a glycoprotein that provides the elasticity and structural integrity necessary for constant movement. There are approximately 70 to 80 ciliary processes from which these thousands of zonular fibers originate to suspend the crystalline lens in place.The process of accommodation was further clarified by the Helmholtz theory in the mid-19th century. It explains that the ciliary muscle acts like a ring. When it contracts, its internal diameter decreases, which releases the tension on the zonules. This allows the lens to naturally bulge into a more spherical shape due to its inherent elasticity, increasing its refractive power for near vision.As humans reach their 40s and 50s, a condition known as presbyopia typically develops. Research published in journals like Investigative Ophthalmology & Visual Science indicates that this occurs because the lens continues to grow and add layers throughout life, eventually becoming too stiff to be easily manipulated by the zonules. By age 60, the lens has often lost almost all of its accommodative power, requiring external corrective lenses for close-up tasks.