- Zonules, or zonule of Zinn is a group of thin, tightly drawn, jellylike fibers that hold the lens in place in the eye. Although each zonule is weak by itself, the suspending framework of thousands is amazingly strong. Zonules are attached to the ciliary muscle and work with it to change the shape of the lens. In order to focus on objects at different distances, the lens must adjust or accommodate. To focus on a near object, the lens must thicken and bulge forward. The ciliary muscle contracts, allowing the zonule to slacken and the lens to thicken and protrude forward. To focus on a distant object, the lens must flatten. The ciliary muscle expands, the zonule is pulled taut, and the lens flattens. Severe or repeated head trauma, as that suffered by boxers or those playing contact sports as well as from automobile accidents, is often enough to dislodge the lens from its normal position. Cataracts are often the result of such trauma.
