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“cataracts”
The loss of transparency of the lens of the eye or a partial or complete opacity on or in the lens or capsule of one or both eyes which impairs vision or even causes some degree of blindness: A cataract usually doesn't cause complete blindness because even a densely opalescent lens that shows various colors will still transmit light; however, with the increasing loss of transparency, the clarity and detail of images will be progressively lost.
Cataracts usually occur in both eyes; however, in most cases one eye is more severely affected than the other eye.
Most people over the age of 65 have some degree of cataracts; but, usually the opacification is minor and it is often confined to the edges of the lens, or lenses, where it doesn't interfere with vision.
The term cataract came many centuries ago from the idea that the whiteness behind the pupil, or lens, was a kind of waterfall descending from the brain.
In fact, the appearance of the whiteness is a result of the changes in the delicate protein fibers within the lens in a way that is similar to what occurs in eggs when they are boiled.
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cata-, cat-, cath-, kata-
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