The lens is the shaping changing structure we need to get this job done. It's a clear flexible biconvex disc that is suspended in space by another important structure, the ciliary body. When we try to focus on objects which are far away the ciliary body relaxes. Because it's a sphincter muscle, this opens it up placing tension on the lens and flattening it out. When we need to focus at a near distance the ciliary body contracts allowing the lens to relax into a more spherical shape.
In addition to its muscular function, the ciliary body is responsible for making the aqueous humor which nourishes structures in the anterior chamber of the eye.
This module begins with a closer look at the anatomy and cellular structure of the ciliary body and the lens. We then turn our attention to the lens entirely to consider the pathologic causes and effects of cataracts, the world's number one cause of reversible blindness.
The ciliary body and lens are anatomical structures which most people never get a chance to observe, however their day-to-day function is essential for our adjustable sight. As most people learn with aging, a decrease in the capacity of these structures to change their shape and maintain transparency can have a significant impact on quality of life.
Issue Date: 08/01/2020