What are cataracts and what causes them to grow?

The word "cataract" is the historical term to refer to what was once the leading cause of blindness in the world: an opacified natural lens of the human eye, seen as a white pupil. The white lens was mistakenly thought to be due to some sort of turbulence in the fluid of the eye just like in the white water seen when a running stream becomes turbulent as it rushes over rocks and shallows (e.g. the cataracts of the Nile river).

The word is nowadays used in a much looser fashion to describe the end stages of (usually) the natural aging process of the natural lens of the eye. It is not a disease, a "skim," or some sort of membrane over the lens as many people think. When we are young the natural lens is crystal clear and very soft/flexible. As we age into our 40s, the lens becomes progressively harder and more dense, offering increasingly greater resistance to the muscle encircling it and squeezing it into the proper shape for near vision. At some point this becomes bad enough to require supplemental reading glasses. As the lens ages further, it also begins to discolor, turning a yellowish gray. Eventually, when this process gets bad enough to compromise vision, we call the natural lens a "cataract."

Written by J. Trevor Woodhams, M.D. - Chief of Surgery, Woodhams Eye Clinic