corneal ectasia

(redirected from corneal degeneration)

ker·a·to·ec·ta·si·a

(ker'ă-tō-ek-tā'zē-ă),
A bulging forward of the cornea.

ectasia, corneal

A forward bulging and thinning of the cornea. It may result from a disease of the cornea (e.g. keratoconus), trauma, atrophy, raised intraocular pressure or as a complication of photorefractive surgery in which the corneal stroma has been left thinner than about 250 μm. If uveal tissue is included in the protrusion, the condition is called a staphyloma. If the ectasia is limited to a peripheral part of the cornea, it is called Terrien's disease or Terrien's marginal degeneration. It is due to degeneration of marginal corneal tissue with superficial vascularization and lipid deposition. It affects adult males more commonly than females and the eye has progressive astigmatism, typically against the rule. Therapy includes rigid contact lenses and occasionally keratoplasty. Syn. keratectasia; keratoectasia; kerectasis. See pellucid marginal degeneration; keratoglobus; staphyloma.

corneal

pertaining to the cornea. See also keratitis, keratopathy.

corneal anomaly
includes microcornea, coloboma, megalocornea, dermoid, congenital opacity.
corneal black body
see corneal sequestrum (below).
corneal coloboma
an uncommon congenital defect in the continuity of the cornea; may have concurrent herniation of the uveal tract. See also coloboma.
corneal dystrophy
a developmental condition, inherited in some breeds of dogs and cats. May cause corneal edema and ulceration. See also keratopathy.
corneal ectasia
corneal edema
occurs when fluid accumulates in the corneal stroma, disrupting the normal lamellar structure and causing a loss of transparency. Commonly called blue eye.
corneal erosion syndrome
see refractory ulcer.
feline focal corneal necrosis
see corneal sequestrum (below).
corneal hyaline membrane
an abnormal, semitransparent membrane on the posterior surface of the cornea, attached to the endothelium. Can be associated with persistent pupillary membrane. Caused by inflammation or a developmental defect.
corneal inflammation
inherited corneal opacity
congenital opacity of the cornea occurs in cattle. The animals are not completely blind and the rest of the eye is normal. Both eyes are affected. The lesion is an edema of the corneal lamellae.
corneal laminae
the limiting membranes that separate the bulk of the cornea from the covering epithelia; the anterior is Bowman's, the posterior is descemet's membrane.
corneal lipidosis
cholesterol crystals and lipid vacuoles may be found in the corneal stroma as a result of persistent hypercholesterolemia or chronic stromal inflammation.
melting corneal
see collagenase ulcer.
corneal mummification
see corneal sequestrum (below).
corneal opacity
corneal pigmentation
results from chronic irritation. The melanin is in the superficial stroma and the basal layer of the corneal epithelium. See also superficial pigmentary keratitis.
corneal reflex
a reflex action of the eye resulting in automatic closing of the eyelids when the cornea is stimulated. The corneal reflex can be elicited in a normal animal by gently touching the cornea with a wisp of cotton. Absence of the corneal reflex indicates deep coma or injury of one of the nerves carrying the reflex arc.
corneal ring abscess
an infected corneal ulcer in which there is a surrounding zone of liquefaction encircled by a zone of neutrophils.
corneal scar
corneal opacity.
corneal sequestrum
a central, focal, dark necrotic plaque on the cornea of cats, especially Persians, associated with chronic ulcerative or inflammatory disease of the cornea. Called also focal superficial necrosis, corneal mummification, keratitis nigrum.
corneal shield
protection used in the treatment of corneal ulcers or wounds; commercial products consisting of collagen which is dissolved in the tear film are claimed to enhance healing.
corneal stromal depositions
minerals, lipids or pigment deposited in the stroma following injury.
superficial corneal erosion
see refractory ulcer.
corneal tattooing
done mainly in horses to obscure unsightly scarring of the cornea.
corneal transparency
the quality of being able to see objects through the cornea; partly the result of the strict horizontal lamellal distribution of its collagen fibers, parallel to the corneal surface.
corneal transplantation
corneal ulcer
a defect in the corneal epithelium and some amount of stroma; may be caused by trauma, chronic irritation as from distichiasis, entropion or keratitis sicca, or infectious agents. Deep ulcers can lead to rupture of the cornea, the escape of aqueous humor and often prolapse of the iris with a secondary uveitis and endophthalmitis. See also ulcer.
Enlarge picture
Corneal ulcer in a horse. By permission from Knottenbelt DC, Pascoe RR, Diseases and Disorders of the Horse, Saunders, 2003
corneal vascularization
results from inflammation of the cornea, the vessels growing in from the limbus. It is a necessary repair process but it reduces visual acuity.
References in periodicals archive ?
Material is in sections on corneal degeneration and dystrophy, external eye disease and tumors, infection, contact lenses, trauma, and postoperative issues.
John's corneal degeneration, who reads Henry James through a glass
Such stem cells also are being studied for treatments for corneal degeneration, heart disease, stroke, Parkinson's disease and Alzheimer's.
Early clinical studies also suggest that they can helped avert corneal degeneration and restore vision in cases of blindness, can help to restore proper cardiac function to heart attack sufferers and can improve movement in spinal cord injury patients.
Table 1 lists some of the common corneal degenerations and these are discussed below.
For undergraduates, postgraduate trainees, fellows, and ophthalmologists, Basak (cataract, cornea, external diseases and eye bank services, Disha Eye Hospitals and Research Center, India) provides a mini atlas of about 600 color photos and descriptions of common corneal conditions, such as congenital anomalies, corneal edema and bullous keratopathy, keratitis, corneal degenerations and dystrophies, and graft-related, refractive surgery-related, and contact lens-induced problems, along with the basics of anatomy and evaluation.

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