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Corneal abscess
Corneal abscess, a suppurative form of infectious keratitis appearing as a white corneal opacity, caused by bacteria, fungi, or parasites; diagnosed by corneal scraping or suture sampling, treated with fortified topical antibiotics and sometimes keratoplasty.
Corneal deformities
Corneal deformities (ICD-11 9A78.5) are abnormal corneal shapes, chiefly keratoconus (9A78.50) and corneal staphyloma (9A78.51), causing blurred vision and irregular astigmatism, treated with lenses or keratoplasty.
Corneal degeneration
Corneal degeneration (ICD-10 H18.4, ICD-11 9A78.4) covers acquired corneal changes from aging, metabolism, or inflammation, unlike hereditary dystrophies; examples include arcus senilis, band keratopathy, and Salzmann nodular degeneration.
Corneal endotheliitis
Corneal endotheliitis is inflammation centered on the corneal endothelium, the cell layer keeping the cornea clear, causing corneal edema; most cases are viral, chiefly herpesviruses like cytomegalovirus, and delayed treatment risks irreversible endothelial cell loss.
Corneal reflex
The corneal reflex, also called the blink reflex, closes both eyelids when the cornea is touched, protecting the eye and testing cranial nerves V and VII.
Corneal tattooing
Corneal tattooing, or keratopigmentation, deposits pigment into the corneal stroma to disguise corneal scars, mask iris-defect symptoms, or change eye color; practiced since Galen, modernized by Von Wecker in 1869, with no FDA-approved pigments.
Corneal transplantation
Corneal transplantation (keratoplasty) replaces diseased corneal tissue with donor cornea. First done by Eduard Zirm in 1905; types include PK, DALK, DSAEK, and DMEK; global supply is 1 cornea per 70 needed.
Corneal ulcer
Corneal ulcer (ulcerative keratitis): an open sore on the cornea, usually infectious (bacterial, viral, fungal, Acanthamoeba), an ocular emergency. Contact lens wear is the leading risk factor; treated with intensive topical antibiotics.
Corona of glans penis
The corona of glans penis, or corona glandis, is the rounded projecting border at the base of the glans penis, the widest part of the glans.
Corona radiata
The corona radiata is the fan-shaped sheet of white matter projection fibers going to and from the cerebral cortex, radiating from and converging downward into the internal capsule.
Coronary arterial fistula
Coronary arterial fistula, or coronary artery fistula (CAVF/CAF), is an abnormal coronary-to-chamber or coronary-to-vessel connection bypassing the capillary bed; mostly congenital, causing coronary steal, heart failure, endocarditis, treated by follow-up, surgery, or transcatheter closure.
Coronary arteries
Coronary arteries: the left main and right coronary arteries, first branches of the aorta supplying the heart muscle; LAD, circumflex, dominance, variants (about 1–2% prevalence), and coronary artery disease.
Coronary artery anomaly
Coronary artery anomaly: congenital abnormality of coronary origin, course, termination, or morphology (AAOCA, ALCAPA, fistula, myocardial bridge). Prevalence about 1–2%; interarterial/intramural courses risk sudden cardiac death in young athletes.
Coronary artery bypass surgery
Coronary artery bypass surgery, or CABG, is open-heart surgery grafting a vessel to bypass blocked coronary arteries. Pioneered by Carrel, Kolessov, and Favaloro (1967), it remains the most common cardiac operation, with better long-term survival than PCI in multivessel disease.
Coronary catheterization
Coronary catheterization (cardiac catheterization with coronary angiography) threads catheters from the radial or femoral artery to the heart to image coronary blockages and enable PCI; major complication rate 1.70%, radial access now preferred in ACS.
Coronary circulation
Coronary circulation: the arteries, capillaries, and veins supplying the myocardium, about 5% of cardiac output, with diastolic-dominant flow, high oxygen extraction, autoregulation, collateral vessels, and microvascular dysfunction assessment.
Coronary CT angiography
Coronary CT angiography (CCTA, coronary CTA) is a contrast-enhanced CT test visualizing coronary lumen and wall to rule out obstructive CAD; ESC 2024 prefers it first-line, with reduced MI but more downstream angiography versus stress testing.
Coronary endarterectomy
Coronary endarterectomy (CE) is direct removal of atherosclerotic plaque from a coronary artery, first reported in a patient by Bailey in 1957. Used as an adjunct to CABG for diffuse coronary disease; higher short-term risk, lower graft patency, comparable long-term survival.
Coronary microvascular dysfunction
Coronary microvascular dysfunction (CMD) is impaired blood flow through the heart's smallest arteries, causing chest pain with unobstructed arteries, mostly in women, and raising risks of heart attack and death.
Coronary ostial stenosis or atresia
Coronary ostial stenosis or atresia (COSA), congenital coronary arterial orifice stenosis or atresia: rare congenital partial or total occlusion of a coronary ostium with proximal hypoplasia, left-sided predominance, ischemia risk, surgical repair.
Coronary sinus
Coronary sinus: the 3-5 cm venous channel in the posterior left atrioventricular groove draining most cardiac venous blood to the right atrium; remnant of the left sinus horn, guarded by the Thebesian valve, key route for pacing leads and ablation.
Coronary sinus atresia
Coronary sinus atresia, or coronary sinus ostial atresia (CSOA), is a rare congenital heart defect in which the coronary sinus ends blindly at the right atrium, draining instead via a persistent left superior vena cava; benign alone but critical in cardiac surgery and CRT lead placement.
Coronary vasospasm
Coronary vasospasm (vasospastic angina, Prinzmetal angina) is transient epicardial coronary artery narrowing causing rest ischemia, diagnosed by COVADIS criteria and acetylcholine provocation testing, treated with calcium channel blockers and nitrates.
Coronary vasospastic disease
Coronary vasospastic disease (vasospastic angina, variant or Prinzmetal angina, coronary spastic angina): myocardial ischemia from transient epicardial coronary spasm, diagnosed by acetylcholine provocation testing, treated first with calcium channel blockers.
Corpus callosotomy
Corpus callosotomy, or split-brain surgery, is palliative neurosurgery dividing the corpus callosum for drug-resistant epilepsy, chiefly atonic drop attacks; first done by van Wagenen in 1940, with open, endoscopic, and laser variants.
Corpus callosum
Corpus callosum: the brain's largest white matter commissure, about 190 million axons linking the hemispheres, unique to placental mammals; key biomarker in MS, aging, and agenesis (1:4000 births).
Corpus cavernosum penis
Corpus cavernosum penis: one of two paired dorsal erectile cylinders of the penis, sinusoidal vascular tissue with helicine arteries and tunica albuginea that traps blood during erection; affected by ED, Peyronie's, priapism, fracture.
Corpus luteum
Corpus luteum (yellow body), temporary ovarian endocrine gland formed from the ruptured Graafian follicle after ovulation; secretes progesterone and estradiol, peaks about 6 days post-ovulation, rescued by hCG in pregnancy, otherwise involutes into the corpus albicans.
Correction of Hearing Impairment
Correction of Hearing Impairment (MeSH D012048, aural rehabilitation) covers procedures for correcting hearing disorders: hearing aids, cochlear implants, and aural rehabilitation, with entry terms including Audiologic Rehabilitation and Aural Habilitation.
Cortical blindness
Cortical blindness, also called cerebral blindness, is bilateral vision loss from bilateral striate cortex lesions with normal pupils and normal eyes; common causes are PCA stroke and hypoxia, with Anton syndrome as denial of blindness.