Corneal ulcer overview: Difference between revisions
Created page with "{{CMG}} {{Corneal ulcer}} ==Overview== A '''corneal ulcer''', or '''ulcerative keratitis''', is an inflammatory or more seriously, infective condition of the cornea invo..." |
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A '''corneal ulcer''', or '''ulcerative keratitis''', is an inflammatory or more seriously, infective condition of the [[cornea]] involving disruption of its epithelial layer with involvement of the corneal stroma. It is a common condition in humans particularly in the tropics and the agrarian societies. In developing countries, as well as in Florida, corneal ulcer is frequently the cause of great morbidity as well as economic loss to the person and family. Children afflicted by Vitamin A deficiency are at high risk for corneal ulcer and may become blind in both eyes, which may persist lifelong, causing tremendous & avoidable loss to the person and the society. | A '''corneal ulcer''', or '''ulcerative keratitis''', is an inflammatory or more seriously, infective condition of the [[cornea]] involving disruption of its epithelial layer with involvement of the corneal stroma. It is a common condition in humans particularly in the tropics and the agrarian societies. In developing countries, as well as in Florida, corneal ulcer is frequently the cause of great morbidity as well as economic loss to the person and family. Children afflicted by Vitamin A deficiency are at high risk for corneal ulcer and may become blind in both eyes, which may persist lifelong, causing tremendous & avoidable loss to the person and the society. | ||
==Corneal anatomy of the humans== | |||
The cornea is a transparent structure that is part of the outer layer of the [[eye]]. It [[refraction|refract]]s light and protects the contents of the eye. The corneal thickness ranges from 450 to 610 micrometres and on an average 550 µm. thick in caucasian eyes. In Indian eyes, the average thickness is slightly less at 510 µm. The [[trigeminal nerve]] supplies the cornea via the [[long ciliary nerve]]s. There are [[nociceptor|pain receptor]]s in the outer layers and [[mechanoreceptor|pressure receptor]]s are deeper. | |||
Transparency is achieved through a lack of blood vessels, pigmentation, and [[keratin]], and through tight layered organization of the [[collagen]] fibers. The collagen fibers cross the full diameter of the cornea in a strictly parallel fashion and allow 99 percent of the light to pass through without scattering. | |||
There are five layers in the human cornea, from outer to inner: | |||
* [[Epithelium]] | |||
* [[Bowman's membrane]] | |||
* [[Stroma]] | |||
* [[Descemet's membrane]] | |||
* [[Endothelium ]] | |||
The outer layer is the [[epithelium]], which is 25 to 40 µm micrometers and five to seven [[cell (biology)|cell]] layers thick. The epithelium holds the tear film in place and also prevents water from invading the cornea and disrupting the collagen fibers. This prevents corneal [[edema]], which gives it a cloudy appearance. It is also a barrier to infectious agents. The epithelium sticks to the [[basal lamina|basement membrane]], which also separates the epithelium from the [[stroma]]. The corneal stroma comprises 90 percent of the thickness of the cornea. It contains the collagen fibers organized into [[lamella]]e. The lamellae are in sheets which separate easily. Posterior to the stroma is [[Descemet's membrane]], which is a basement membrane for the [[corneal endothelium]]. The endothelium is a single cell layer that separates the cornea from the [[aqueous humor]]. | |||
==References== | ==References== | ||
{{Reflist|2}} | {{Reflist|2}} | ||
Revision as of 18:53, 1 February 2012
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Overview
A corneal ulcer, or ulcerative keratitis, is an inflammatory or more seriously, infective condition of the cornea involving disruption of its epithelial layer with involvement of the corneal stroma. It is a common condition in humans particularly in the tropics and the agrarian societies. In developing countries, as well as in Florida, corneal ulcer is frequently the cause of great morbidity as well as economic loss to the person and family. Children afflicted by Vitamin A deficiency are at high risk for corneal ulcer and may become blind in both eyes, which may persist lifelong, causing tremendous & avoidable loss to the person and the society.
Corneal anatomy of the humans
The cornea is a transparent structure that is part of the outer layer of the eye. It refracts light and protects the contents of the eye. The corneal thickness ranges from 450 to 610 micrometres and on an average 550 µm. thick in caucasian eyes. In Indian eyes, the average thickness is slightly less at 510 µm. The trigeminal nerve supplies the cornea via the long ciliary nerves. There are pain receptors in the outer layers and pressure receptors are deeper.
Transparency is achieved through a lack of blood vessels, pigmentation, and keratin, and through tight layered organization of the collagen fibers. The collagen fibers cross the full diameter of the cornea in a strictly parallel fashion and allow 99 percent of the light to pass through without scattering.
There are five layers in the human cornea, from outer to inner:
The outer layer is the epithelium, which is 25 to 40 µm micrometers and five to seven cell layers thick. The epithelium holds the tear film in place and also prevents water from invading the cornea and disrupting the collagen fibers. This prevents corneal edema, which gives it a cloudy appearance. It is also a barrier to infectious agents. The epithelium sticks to the basement membrane, which also separates the epithelium from the stroma. The corneal stroma comprises 90 percent of the thickness of the cornea. It contains the collagen fibers organized into lamellae. The lamellae are in sheets which separate easily. Posterior to the stroma is Descemet's membrane, which is a basement membrane for the corneal endothelium. The endothelium is a single cell layer that separates the cornea from the aqueous humor.