keratoconus (redirected from Keratoconus posticus circumscriptus)

keratoconus /ker·a·to·co·nus/ (-ko´nus) conical protrusion of the central part of the cornea.

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ker·a·to·co·nus (kr-t-kns)

n.

A conical protrusion of the center of the cornea caused by noninflammatory thinning of the stroma and usually affecting both eyes. Also called conical cornea.

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Keratoconus

An eye condition in which the cornea bulges outward, interfering with normal vision. Usually both eyes are affected.

Mentioned in: Corneal Transplantation

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keratoconus

[ker′ətōkō′nəs]

Etymology: Gk, keras + konos, cone

a noninflammatory protrusion of the central or paracentral region of the cornea. It is worse in allergy sufferers and may result in marked irregular astigmatism. It is also associated with Down syndrome. Gas permeable contact lenses often significantly improve visual acuity as compared with spectacles, although a corneal transplant is indicated in about 15% of patients with this condition. The cause of the condition is unknown, but it likely has a genetic basis.

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keratoconus

conical protrusion of the central part of the cornea.

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keratoconus (KC)

A developmental anomaly in which the central portion of the cornea becomes thinner and bulges forward in a cone-shaped fashion. Two types of cones are commonly described: a round cone and an oval (or sagging) cone. It usually appears around puberty, is bilateral, although one eye may be involved long before the other. Other corneal signs may be Vogt's striae, Fleischer's ring, scarring and corneal hydrops, as well as myopia and irregular astigmatism. The condition may be associated with osteogenesis imperfecta, ectopia lentis, aniridia, retinitis pigmentosa, Down's syndrome, Ehlers-Danlos syndrome, Marfan's syndrome. The main symptom is a loss of visual acuity due to irregular astigmatism and myopia. Correction is usually best achieved with contact lenses, especially rigid gas permeable, but if these cannot be worn or the condition is very severe, a corneal transplant is carried out (Fig. K1). Syn. conical cornea. See central corneal clouding; pellucid marginal degeneration; corneal ectasia; acute hydrops; keratoscope; combination lens; piggyback lens; lenticonus; blue sclera; Munson's sign; Rizzuti's sign; stria; corneal topography.

Fig. K1 Schematic diagram of a keratoconus cornea

Table K1 Differential diagnosis between keratoconus and related thinning disorders. (Adapted from Krachmer JH, Feder RS, Belin MW. Surv Ophthalmol 1984; 28:293-322)
		keratoconus		pellucid marginal degeneration		keratoglobus		posterior keratoconus
frequency		most common		less common		rare		least common
laterality		usually bilateral		bilateral		bilateral		usually unilateral
age of onset		puberty/early adulthood		Age 20 to 40s		usually at birth		birth
corneal thinning		central or paracentral		inferior crescent-shaped band 1-2 mm wide		generalized and slightly more in periphery		paracentral posterior excavation
protrusion		apical		above band of thinning		generalized		none
iron line (Fleischer's ring)		common		rare		none		occasional
scarring		common		only after hydrops		rare		common
progression		yes		yes		usually no		no
induced astigmatism		irregular		high, irregular and varies with location		none		very slight effect

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Patient discussion about Keratoconus posticus circumscriptus.

Q. Has anyone had experience with a corneal transplant because of keratoconus?

A. my uncle had to do a transplant- it took 5 weeks until he could see anything , another year to get his vision straightened up. but now he is fine! i know that he looked for information in the "National Keratoconus Foundation". they were very helpful (and nice!), they have a website with information on all forms of treatment:
http://www.nkcf.org/

good luck :)