Kerat: From 1 Different Sources
(kerato-) combining form denoting 1. the cornea. Example: keratopathy (disease of). 2. horny tissue, especially of the skin.
Inflammation of the cornea.... keratitis
The substance of which horn and the surface layer of the skin are composed.... keratin
Inflammation of the cornea and the conjunctiva.... keratoconjunctivitis
Softening of the cornea due to a severe vitamin A de?ciency (see EYE, DISORDERS OF).... keratomalacia
See CORNEAL GRAFT.... keratoplasty
Also known as actinic keratosis; a rough, scaly area on exposed skin caused by chronic solar damage from exposure to sun. The face and backs of the hands are most commonly affected. (See also MELANOMA; PHOTODERMATOSES.) CRYOTHERAPY is e?ective, but prevention by appropriate clothing and sun-blocking creams is a better strategy.... keratosis
A type of harmless skin nodule that commonly occurs in elderly people, most often on the face or arm. The cause is unknown, but many years of exposure to strong sunlight or long-term use of immunosuppressant drugs may be factors. Initially, the nodule resembles a small wart, but it grows to 1–2cm across in about 8 weeks. Although the nodule usually disappears gradually after this, surgical removal is often recommended to prevent scarring.... keratoacanthoma
An inherited disorder of the eye in which the cornea becomes gradually thinned and conical. The condition affects both eyes and usually develops around puberty, giving rise to increasing myopia and progressive distortion of vision that cannot be fully corrected by glasses. Hard contact lenses improve vision in the early stages, but when vision has seriously deteriorated and contact lenses are no longer helpful it generally becomes necessary to perform a corneal graft.... keratoconus
A surgical treatment for astigmatism, myopia, and hypermetropia, in which areas of the cornea are shaved away by laser.... photorefractive keratectomy
Deposition of KERATIN in cells, in particular those in the skin. The cells become horny and ?attened and lose their nuclei, forming hair and nails or hard areas of skin.... keratinisation
Persistent dryness of the cornea and conjunctiva caused by deficiency in tear production. The condition is associated with autoimmune disorders such as rheumatoid arthritis, Sjögren’s syndrome, and systemic lupus erythematosus. Prolonged dryness may lead to blurred vision, itching, grittiness, and, in severe cases, the formation of a corneal ulcer. The most effective treatment is frequent use of artificial tears (see tears, artificial).... keratoconjunctivitis sicca
a curved incision made in the periphery of the cornea. It is usually performed in the region of greatest curvature of the cornea in order to flatten it and hence reduce *astigmatism.... arcuate keratotomy
(ALK) excision of the outer layers of the cornea using an automated *keratome. It is usually used as part of a surgical procedure, to alter the shape of the cornea to correct errors of refraction.... automated lamellar keratectomy
the deposition of calcium in the superficial layers of the cornea, usually as a horizontal band starting peripherally and moving centrally. It is associated with chronic eye disease, e.g. chronic *uveitis, particularly juvenile chronic uveitis. It is treated by application of EDTA (see edetate) or with an *excimer laser.... band keratopathy
a pathological condition of the cornea of the eye due to failure in the functioning of its endothelium. It results in corneal oedema, seen as small blisters in the cornea that cause blurring of vision. See Fuchs’ endothelial dystrophy.... bullous keratopathy
an operation to correct severe degrees of myopia (short-sightedness). A disc of corneal tissue (from the *stroma of the cornea) is removed, frozen, and remodelled on a lathe, then replaced into the cornea to alter its curvature and thus reduce the myopia. *Excimer laser treatment, which is easier to perform, has now replaced this (see LASIK).... intrastromal keratomileusis
n. pain arising from the cornea.... keratalgia
n. bulging of the cornea at the site of scar tissue (which is thinner than normal corneal tissue).... keratectasia
n. an operation in which a part of the cornea is removed, usually a superficial layer. This procedure is now frequently done by an *excimer laser, either to correct refractive errors (myopia, hypermetropia), by reshaping the surface of the cornea (photorefractive keratectomy; PRK), or to remove diseased corneal tissue (phototherapeutic keratectomy). See also automated lamellar keratectomy.... keratectomy
(cornification) n. the process by which cells become horny due to the deposition of *keratin within them. It occurs in the *epidermis of the skin and associated structures (hair, nails, etc.), where the cells become flattened, lose their nuclei, and are filled with keratin as they approach the surface.... keratinization
n. a type of cell that makes up 95% of the cells of the epidermis. Keratinocytes migrate from the deeper layers of the epidermis and are finally shed from the surface of the skin.... keratinocyte
(descemetocele) n. outward bulging of the base of a deep ulcer of the cornea. The deep layer of the cornea (Descemet’s membrane) is elastic and relatively resistant to perforation; it therefore bulges when the overlying cornea has been destroyed.... keratocele
(fibroblast) n. a cell, derived from *mesenchyme, of the corneal *stroma. Such cells are normally quiescent but can readily respond to injury and change into repair types.... keratocyte
(megalocornea) n. a congenital disorder of the eye in which the whole cornea bulges forward in a regular curve. Compare keratoconus.... keratoglobus
n. any instrument designed for cutting the cornea. The simplest type has a flat triangular blade attached at its base to a handle, the other two sides being very sharp and tapering to a point. Power-driven keratomes have oscillating or rotating blades. An automated keratome is used in *automated lamellar keratectomy. See also microkeratome.... keratome
(ophthalmometer) n. an instrument for measuring the radius of curvature of the cornea. Usually the vertical and horizontal curvatures are measured. All keratometers work on the principle that the size of the image of an object reflected from a convex mirror (in this case, the cornea) depends on the curvature of the mirror. The steeper the curve, the smaller the image. The keratometer is used for assessing the degree of curvature of the cornea in different meridians. —keratometry n.... keratometer
n. see intrastromal keratomileusis; LASIK.... keratomileusis
n. an optically clear prosthesis that is implanted into the cornea to replace an area that has become opaque. Due to its poor success rate, it is used only as a last resort in an attempt to restore some sight to patients with severe disease where corneal transplantation (see keratoplasty) is unlikely to succeed.... keratoprosthesis
(Placido’s disc) n. an instrument for detecting abnormal curvature of the cornea. It consists of a black disc, about 20 cm in diameter, marked with concentric white rings. The examiner looks through a small lens in the centre at the reflection of the rings in the patient’s cornea. A normal cornea will reflect regular concentric images of the rings; a cornea that is abnormally curved (for example in *keratoconus) or scarred reflects distorted rings. Modern keratoscopes can print out a contour map of the corneal surface.... keratoscope
an abnormal build-up of *keratin and dead skin cells within the ear canal that can block the canal, cause conductive hearing loss (see deafness), and erode the bone of the ear canal. It is associated with *bronchiectasis and chronic sinusitis.... keratosis obturans
n. an incision into the cornea. See arcuate keratotomy; radial keratotomy.... keratotomy
n. inflammation involving both the cornea (see keratitis) and the uvea (see uveitis).... keratouveitis
see keratectomy.... phototherapeutic keratectomy
an operation for short-sightedness (myopia). Deep cuts into the tissue of the cornea are placed radially around the outer two-thirds of the cornea; this flattens the curvature of the central part of the cornea and reduces the myopia. This procedure is now rarely performed, having been superseded by *excimer laser treatment.... radial keratotomy
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