Cataract

n. cascade, waterfall, downpour; clouding of the lens of the eye (Medical)

A cataract is an opacity that develops in the crystalline lens of the eye or in its envelope. Early on in the development of age-related cataract the power of the crystalline lens may be increased, causing near-sightedness (myopia), and the gradual yellowing and opacification of the lens may reduce the perception of blue colours. Cataracts typically progress slowly to cause vision loss and are potentially blinding if untreated. Moreover, with time the cataract cortex liquefies to form a milky white fluid in a Morgagnian Cataract, and can cause severe inflammation if the lens capsule ruptures and leaks. Untreated, the cataract can cause phacomorphic glaucoma. Very advanced cataracts with weak zonules are liable to dislocation anteriorly or posteriorly. Such spontaneous posterior dislocations (akin to the historical surgical procedure of couching) in ancient times were regarded as a blessing from the heavens, because it restored some perception of light in the bilaterally affected patients.
See more at Wikipedia.org...

Cataract /cat·a·ract/ an opacity of the crystalline lens of the eye or its capsule.catarac´tous after-cataract a recurrent capsular cataract. [more]Cataract - Community and Resources

Noun
1. clouding of the natural lens of the eye
(hypernym) eye disease
2. a large waterfall; violent rush of water over a precipice
(hypernym) waterfall, falls

n. cataract, cascade, waterfall, downpour; clouding of the lens of the eye (Medical)