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.
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