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Encyclopedia > Corneal ulcer

A corneal ulcer is an inflammatory condition of the cornea involving loss of its outer layer. It is very common in dogs and cats. It is also known as ulcerative keratitis. The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber and provides most of an eyes optical power [1]. Together with the lens, the cornea refracts light and consequently helps the eye to focus. ... Trinomial name Canis lupus familiaris (Linnaeus, 1758) The dog is a canine mammal of the Order Carnivora. ... Trinomial name Felis silvestris catus (Linnaeus, 1758) This article is about the domestic cat. ...

Large corneal ulcer in a dog
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Large corneal ulcer in a dog

Contents


Corneal anatomy of the dog and cat

The cornea is a transparent structure at the front of the eye. It refracts light and protects the contents of the eye. The cornea is about one-half to one millimeter thick in the dog and cat. The trigeminal nerve supplies the cornea via the long ciliary nerves. There are pain receptors in the outer layers and pressure receptors deeper. To meet Wikipedias quality standards, this article or section may require cleanup. ... // Headline text This article refers to refraction in waves. ... The trigeminal nerve is the fifth (V) cranial nerve, and carries sensory information from most of the face, as well as motor supply to the muscles of mastication (the muscles enabling chewing), tensor tympani (in the middle ear) and other muscles in the floor of the mouth, such as the... A nociceptor is a sensory receptor that responds only after a high level of stimuli or a level enough to hurt the individual. ... A mechanoreceptor is a sensory receptor that responds to mechanical pressure or distortion. ...


Transparency is achieved through a lack of blood vessels, pigmentation, and keratin, and through the 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. Micrograph of stained α-keratin from mouse liver Keratins are fibrous structural proteins; tough and insoluble, they form the hard but nonmineralized structures found in reptiles, birds and mammals (vertebrates), and also the silk of insects and spiders (invertebrates). ... Tropocollagen triple helix. ... In particle physics, scattering is a class of phenomena by which particles are deflected by collisions with other particles. ...


There are four important layers in the dog and cat cornea. The outer layer is the epithelium, which is 25 to 40 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. 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. In zootomy, epithelium is a tissue composed of a layer of cells. ... External, internal, and depth micrometers A micrometer is a widely used device in mechanical engineering for precisely measuring thickness of blocks, outer and inner diameters of shafts and depths of slots. ... A cell is a single unit or compartment, enclosed by a border or wall. ... Edema (BE: oedema, formerly known as dropsy) is swelling of any organ or tissue due to accumulation of excess fluid. ... The basal lamina (often erroneously called basement membrane) is a layer on which epithelium sits. ... Stroma can refer to: 1) The connective supportive framework of a biological cell, tissue, or organ. ... Gill may refer to one of the following. ... A basement membrane that lies between the proper substance and the endothelial layer of the cornea; posterior limiting layer of the cornea. ... Corneal endothelium is the inner most layer of the cornea, the corneal endothelium is actually a monolayer of squamate epithelial cells lining the anterior chamber of the eye. ... The aqueous humour is the clear, watery fluid that fills the complex space in the front of the eye which is bounded at the front by the cornea and at the rear by the front surface or face of the vitreous humour. ...


Corneal healing

An ulcer of the cornea heals by two methods: migration of surrounding epithelial cells followed by mitosis (dividing) of the cells, and introduction of blood vessels from the conjunctiva. Simple, small ulcers heal by the first method. However, larger or deeper ulcers often require the presence of blood vessels to supply inflammatory cells. White blood cells and fibroblasts produce granulation tissue and then scar tissue, effectively healing the cornea. Light micrograph of a newt lung cell in early anaphase of mitosis. ... The conjunctiva is a membrane that covers the sclera (white part of the eye) and lines the inside of the eyelids. ... White blood cells (also called leukocytes or immune cells) are a component of blood. ... A fibroblast is a cell that makes the structural fibers and ground substance of connective tissue. ... Granulation tissue is the tissue that replaces a fibrin clot in healing tissue. ...


Superficial and deep corneal ulcers

Corneal ulcers are one of the most common eye diseases in dogs. They are caused by trauma, detergent burns, and infections. Other eye conditions can cause corneal ulcers, such as entropion, distichia, corneal dystrophy, and keratoconjunctivitis sicca. Superficial ulcers involve a loss of part of the epithelium. Deep ulcers extend into or through the stroma and are can result in severe scarring and corneal perforation. Descemetoceles occur when the ulcer extends through the stroma. This type of ulcer is especially dangerous and can result in perforation. Corneal ulcers are painful due to nerve exposure, and can cause tearing, squinting, and pawing at the eye. Entropion is a medical condition in which the eyelids fold inward. ... A distichia is an eyelash that arises from an abnormal spot on the eyelid of dogs. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Keratoconjunctivitis sicca (KCS), also called keratits sicca, xerophthalmia, dry eye syndrome, or simply dry eyes, is an eye disease caused by decreased tear production or increased tear film evaporation commonly found in humans and small animals. ...


Diagnosis

Diagnosis is through the use of fluorescein stain, which is taken up by exposed corneal stroma and appears green. With descemetoceles, Descemet's membrane will bulge forward and after staining will appear as a dark circle with a green boundary, because it doen not absorb the stain. fluorescein isothiocyanate Fluorescein is a fluorophore commonly used in microscopy, in a type of dye laser as the gain medium, and in forensics and serology to detect latent blood stains. ...


Treatment

Treatment of corneal ulcers includes topical antibiotic therapy to prevent infection and pain medications, including topical atropine to stop spasms of the ciliary muscle. Superficial ulcers usually heal in less than a week. Deep ulcers and descemetoceles may require corneal suturing, conjunctival grafts or conjunctival flaps, soft contact lenses, or corneal transplant. Topical corticosteroids should never be used on any type of corneal ulcer because they prevent healing and will often make them worse. Structure of atropine (hyoscyamine) Atropine is a tropane alkaloid extracted from the deadly nightshade (Atropa belladonna) and other plants of the family Solanaceae. ... The ciliary muscle is a muscle that affects zonules in the eye (fibers that suspend the lens in position during accommodation), enabling changes in lens shape for light focusing. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Cornea Transplant A cornea transplant, also known as a corneal graft or penetrating keratoplasty, is a surgical procedure where a damaged or diseased cornea is replaced by a donor. ... In physiology, corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. ...


Refractory corneal ulcers

Refractory corneal ulcers are superficial ulcers that heal poorly and tend to recur. They are also known as indolent ulcers or Boxer ulcers. They are caused by a defect in the basement membrane. They are recognized by undermined epithelium that surrounds the ulcer and easily peels back. Refractory corneal ulcers are most commonly seen in middle aged or older dogs and often occur in the other eye later. They are similar to Cogan's cystic dystrophy in humans.


Commonly affected breeds

The Alaskan Malamute is a large northern dog breed originally developed for use as a sleddog. ... The American Cocker Spaniel evolved in the United States from spaniels imported from Great Britain. ... The Boston Terrier is a breed of dog originating in the United States of America. ... Boxers are a breed of stocky, medium-sized, short-haired dog with a smooth fawn or brindled coat and square-jawed muzzle. ... The Brussels Griffon is a small dog with a very expressive, monkey-like face and a big heart. ... The Cairn Terrier is a breed of dog of the terrier category. ... The Chesapeake Bay Retriever is a breed of dog that was developed along the Chesapeake Bay to hunt waterfowl under adverse weather and water conditions, often having to break ice during the course of many strenuous multiple retrieves. ... The Dachshund is a short-legged, elongated dog breed of the hound family. ... Country of origin United Kingdom Classification Breed standards (external links) FCI, AKC, ANKC KC(UK), NZKC, UKC The English Bulldog, often called simply the Bulldog, is a medium-sized dog breed that originated in the United Kingdom. ... The German Shepherd Dog (known also as the Alsatian or Schäfer (hund) is an intelligent breed of dog. ... The Golden Retriever is a relatively modern and very popular breed of dog. ... It has been suggested that this article or section be merged with Red Setter. ... Common nickname Peke Classification and breed standards Pekingese is an ancient toy breed of dog, originating in China. ... The Poodle is a breed of dog; specifically, it is a gun dog noted for its ability in the water and bird hunting skills. ... Wikimedia Commons has media related to: Rottweiler A Rottweiler is a medium large, robust and powerful dog breed originating from Germany. ... Common nicknames Country of origin Russia Classification and breed standards The Samoyed dog takes its name from an obsolete term for the Nenets people of Siberia. ... The Australian Silky Terrier is an Australian breed of dog. ... Springer Spaniel refers to two different breeds of dogs, both of which are commonly called simply Springer Spaniel: Welsh Springer Spaniel English Springer Spaniel This is a disambiguation page — a navigational aid which lists pages that might otherwise share the same title. ... Country of origin Germany Classification and breed standards The Weimaraner is a silver-grey breed of dog developed originally both for tracking large game, such as bears, and as a gun dog. ... The Cardigans ears (left) are somewhat larger than the Pembrokes. ... West Highland White Terriers are a breed of dog known for their spirited personality and brilliant white coat; their devotees often call them simply Westies. ... Common nickname Foxie Country of origin England Classification and breed standards The Wire Fox Terrier is a breed of dog, one of many terrier breeds. ...

Treatment

Refractory corneal ulcers can take a long time to heal, sometimes months. Topical antibiotics are used continually to prevent infection. Pain medications are given as needed. Loose epithelium is removed with a dry cotton swab under topical anesthesia. This is in order to allow production of normal basement membrane and division of normal epithelium. Often further treatment is necessary, such as a keratotomy, which is superficial cutting or piercing of the cornea. There are two main types used in dogs: multiple punctate keratotomy (MPK) and grid keratotomy (GK). MPK involves making small superficial punctures into the cornea with a needle. GK is more commonly used and involves making parallel and perpindicular scratches in the corneal surface. Usually only topical anesthesia is necessary. By scoring the corneal surface, anchoring points are provided for attachment of new epithelium. Of course, these procedures should only be performed by a veterinarian, particularly one with some experience in this treatment. A topical eye anesthetic is a topical anesthetic that is used to numb the surface of the eye. ... To meet Wikipedias quality standards and appeal to a wider international audience, this article may require cleanup. ...


Melting ulcers

Melting ulcers are a type of corneal ulcer involving progressive loss of stroma in a dissolving fashion. This is most commonly seen in Pseudomonas infection, but it can be caused by other types of bacteria or fungi. These infectious agents produce proteases and collagenases which break down the corneal stroma. Treatment includes antibiotics and collagenase inhibitors such as acetylcysteine and blood serum. Surgery may be necessary. Species P. fluorescens P. putida etc. ... Subgroups Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular: bacterium) are a major group of living organisms. ... Divisions Chytridiomycota Deuteromycota Zygomycota Glomeromycota Ascomycota Basidiomycota Fungus growing on a tree in Borneo A fungus (plural fungi) is a eukaryotic organism that digests its food externally and absorbs the nutrient molecules into its cells. ... Proteases (proteinases, peptidases or proteolytic enzymes) are enzymes that break peptide bonds between amino acids of proteins. ... N-acetylcysteine is a chemical, commonly called NAC, produced by the body that enhances the production of the molecule glutathione, a powerful antioxidant. ...


Corneal ulcers in cats

Corneal ulcers in cats can be caused by trauma, detergent burns, infections, and other eye diseases. One common cause not seen in dogs is infection with feline herpesvirus-1 (FHV-1). FHV-1 causes ulceration by direct infection of the epithelial cells. Lesions appear as dendritic (branching) ulcers. FHV-1 also suppresses healing of the cornea. Symptoms include conjunctivitis, squinting, eye discharge, and blood vessels on the cornea. It can cause severe scarring. Treatment is with topical antiviral drugs. Genera Subfamily Alphaherpesvirinae    Simplexvirus    Varicellovirus    Mardivirus    Iltovirus Subfamily Betaherpesvirinae    Cytomegalovirus    Muromegalovirus    Roseolovirus Subfamily Gammaherpesvirinae    Lymphocryptovirus    Rhadinovirus Unassigned    Ictalurivirus The Herpesviridae are a family of DNA viruses that cause diseases in humans and animals. ... Antiviral drugs are a class of medication used specifically for treating viral infections. ...


References

  • Gelatt, Kirk N. (ed.)(1999). Veterinary Ophthalmology (3rd ed.). Lippincott, Williams & Wilkins. ISBN 0-683-30076-8

 
 

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