What’s a Zonule?

When we perform cataract surgery, we take natural crystalline lens out of the eye and replace it with an artificial lens implant. I sometimes describe the natural lens of the eye as an M&M: there is an outer “candy shell” with “chocolate” inside. The chocolate represents the cataract itself, and the candy shell represents the capsule of the cataract. By taking out the cataract (chocolate), the capsule (candy shell) is left in place, and the artificial lens implant can be placed inside the capsule. The capsule then holds the cataract in the right place in the eye.

The capsule itself is held in place by a bunch of fibers attached to the wall of the eye. These fibers are called “zonules.” In some conditions and situations, the zonules of the eye are not stable, and that can cause problems with the stability of the capsule. Obviously, if the capsule is not stable, then placing the typical artificial lens implant gets complicated. Therefore, we much prefer cataract surgeries in which the zonules are in great shape.