Webster's New World Medical Dictionary

cornea, conical
See 
keratoconus.
corneal abrasion
A scratch or scrape on the
cornea, the clear front window of the eye that trans-
mits and focuses light into the eye. Corneal abrasion
can also be caused by excessive dryness to the eye.
The cornea can become infected and painful as a
result of the abrasion. See also 
cornea.
corneal dystrophy
A condition in which one or
more parts of the cornea lose their normal clarity
due to a buildup of cloudy material. There are over
20 corneal dystrophies that affect all parts of the
cornea.
corneal dystrophy, Cogan
See 
Cogan corneal
dystrophy.
corneal ring, intrastromal
A plastic ring
designed to be implanted in the cornea in order to
flatten the cornea and thereby correct, or reduce
the degree of, nearsightedness (myopia). The ring
is placed in the corneal stroma, the middle of the
five layers of the cornea.
coronal plane
A vertical two-dimensional imagi-
nary slice through the body from head to foot and
parallel to the shoulders.
coronary artery
A vessel that supplies the heart
muscle (myocardium) with blood that is rich in
oxygen. The coronary arteries encircle the heart in
the manner of a crown (in Latin, corona means
“crown”). Like other arteries, the coronary arteries
may be subject to arteriosclerosis (hardening of the
arteries). See also 
artery.
coronary artery bypass graft
See 
bypass,
coronary.
coronary artery disease
Impedance or block-
age of one or more arteries that supply blood to the
heart, usually due to atherosclerosis (hardening of
the arteries). Abbreviated CAD. A major cause of ill-
ness and death, CAD begins when hard cholesterol
substances (plaques) are deposited within a coro-
nary artery. The plaques in the coronary arteries can
lead to the formation of tiny clots that can obstruct
the flow of blood to the heart muscle, producing
symptoms and signs of CAD, including chest pain
(angina pectoris), heart attack (myocardial infarc-
tion), and sudden death. Treatment for CAD
includes bypass surgery, balloon angioplasty, and
the use of stents.