Zonules are fibers or small threads that suspend the lens of the eye from the ciliary body and hold it in position. These fibers are arranged in a radial pattern.
Normally when we focus on a close object (such as a book), the muscle pulls on the zonules, which pull on the edges of the lens causing it to become thicker in the center, increasing its power to allow you to read. If changes occur in the zonules, causing them to be moore loose, presbyopia can result.
For more information on presbyopia, Click here.