Cornea Disorders (Lec 3 Pt 1) PDF

cornea disorders Prof.Dr. Mahmoud Hussein Elkammar  cornea The cornea is the most powerful refracting surface of the eye and is completely transparent  Anatomy of the cornea Cornea is the anterior transparent segment of the external fibrous layer of the globe. In most domes...

cornea disorders Prof.Dr. Mahmoud Hussein Elkammar  cornea The cornea is the most powerful refracting surface of the eye and is completely transparent  Anatomy of the cornea Cornea is the anterior transparent segment of the external fibrous layer of the globe. In most domestic animals the horizontal diameter is greater than the vertical diameter. It is horizontally elliptical or pear-shaped in equine and bovine and nearly circular in dog and cat.  Anatomy of the cornea The thickness of the cornea varies among species. It varies between 0.5-2mm and differs from the center and at the periphery. The canine and bovine corneas are thickest at the center while the equine cornea is thickest at the limbus. The corneal thickness has obvious clinical importance in surgery and disease.  Anatomy of the cornea Histologically the cornea consists of: 1- Epithelium consists of a basal lamina, basal cells, wing cells and superficial squamous cells. Normal epithelium of the cornea is constantly desquamated at the surface and is completely replaced every 4-8 days.  Anatomy of the cornea Histologically the cornea consists of five layers: 2- Bowman's layer: Anterior limiting membrane  Anatomy of the cornea Histologically the cornea consists of four layers: 3- Stroma or substantia propria; is composed of collagenous fibers arranged in lamellae, fibroblast cells (keratocytes) and ground substance. It forms 90% of the thickness of the cornea.  Anatomy of the cornea Histologically the cornea consists of four layers: 4- Descemet's membrane or posterior limiting membrane; basement membrane of endothelium.  Anatomy of the cornea Histologically the cornea consists of four layers: 5- Endothelium; it is a single layer of cuboidal cells lining the inner surface of the cornea. Congenital Disorders of Cornea  Microcornea It is abnormally small cornea. q Macrocornea It means large cornea in a globe. q Dermoids It is an ectopic piece of skin present on the cornea and /or conjunctiva. Superficial keratectomy is the successful method of treatment. q Coloboma of the cornea It means absence of a full segment of the cornea. It is a very rare condition. Acquired Disorders of Cornea  A. Keratitis It means inflammation of the cornea. Symptoms (A) Subjective symptoms Pain of the cornea, exhibited by photophobia and blepharospasm. Ocular discharge, are slight or severe depending on the type of keratitis.  Keratitis B) Objective symptoms 1. Conjunctival and ciliary injection of the blood vessels v Conjunctival & ciliary blood vessels around cornea become engorged with blood. v Conjunctival blood vessels appear bright red, dilated, tortuous and movable. v Ciliary blood vessels are darker in color, straight and not movable.  Keratitis B) Objective symptoms 2. Loss of corneal transparency v Usually results either from corneal edema or due to inflammatory exudate which is usually leucocytic infiltration.  Keratitis B) Objective symptoms 3. Vascularization of the cornea v The normally avascular cornea may be invaded by different blood vessels as a defensive mechanism against disease or injury.  Keratitis B) Objective symptoms 4. Ulceration of the cornea v Corneal ulceration may be superficial or deep and spreading or localized. v Extend of ulceration is easily determined by fluorescein dye which stains green all ulcerated and abraded areas.  Keratitis B) Objective symptoms 5. Pigmentation of the cornea It is a nonspecific response to inflammation of the cornea, either mild or severe. The pigments are deposited in the epithelium or stroma. 6. Hypopyon It means accumulation of inflammatory exudate at the anterior chamber of the eyeball. Classification of keratitis  1. Superficial keratitis a) Superficial punctate keratitis  Epithelial and subepithelial lesions range in size between fine circular to large white opacities.  No clinical signs or ocular inflammation are present.  it may be associated with long standing keratoconjunctivitis or due to virus infection. Treatment: Topical corticosteroids, antibiotics and/or yellow mercuric oxide may be helpful in treatment.  1. Superficial keratitis b) Superficial abscesses  abscess formation at superficial layers of cornea due to trauma, scratches or presence of a foreign body.  A green yellowish swelling is usually observed and varies in size from few millimeters to 20mm. Treatment  Opening of abscess & suction of its content followed by curettage will correct the condition.  Superficial keratectomy has provided a satisfactory result in most cases.  1. Superficial keratitis c) Pannus chronic diffuse inflammatory condition affecting superficial layers of cornea characterized by subepithelial connective tissue infiltration &vascularization of cornea. It is a primary condition in German shepherd breed and termed degenerative pannus. Causes Unknown, breed predisposition is suggestive. The condition is potentiated by ultraviolet light.  1. Superficial keratitis Symptoms The condition is bilateral  Begins as a grayish haze at the temporal limbus then starts at the nasal limbus and grows to cover the whole cornea.  Superficial vascularization derived from conjunctiva.  Pigmentation continues to spread over the cornea.  If the condition is untreated, blindness may result in many cases.  1. Superficial keratitis Treatment Early cases; treated by topical application of corticosteroid 4-6 times daily until improvement, then 2-3 times daily. Dexamethasone solution is used 4 times a day then the dose is decreased gradually if response has been observed. In moderately advanced cases; subconjunctival corticosteroids is indicated.  1. Superficial keratitis Treatment In advanced cases; with minimal scarring Beta radiation is performed. Chemical cauterization; with pure carbolic acid may be applied to the pannus area. Superficial keratectomy; in advanced cases with severe scarring. Periotomy; conjunctival blood vessels are destroyed at the limbus by heat or electrocauterization.  1. Superficial keratitis d) Keratoconjunctivitis sicca It is a diffuse superficial keratitis secondary to lacrimal gland insufficiency.  1. Superficial keratitis e) Exuberant granulation tissue It builds up on the surface of the cornea as a result of injury. Superficial vascularization can be observed crossing cornea to the area of granulation. Treatment Periotomy. Surgical removal of the granulation tissue.  2. Pigmentary keratitis It means deposition of pigments in the cornea as a response to an irritating factors or a form of stress. Deposition of pigments may be superficial in the epithelium and superficial stroma or deep at the deeper layers of stroma.  2. Pigmentary keratitis-Causes Trichiasis and distichiasis. Exophthalmia and large palpebral fissure. Entropion and prominent nasal folds. Keratoconjunctivitis sicca. Diffuse superficial keratitis (pannus). Following corneal injuries. Anterior synechia (congenital or acquired). Persistent pupillary membrane.  2. Pigmentary keratitis-Symptoms  Pigments may be present superficially at the epithelium and superficial layers of stroma or deep at the deeper parts of the stroma.  It may accompanied by opacities of the cornea and vascularization according to the cause.  2. Pigmentary keratitis-Treatment  Elimination of the cause, as correction of distichiasis or trichiasis, removal of nasal folds, reduction in the size of palpebral fissure  Removal of the pigments: If the pigments not interfere with the animal vision, treatment is not indicated, but if the pigments have already resulted in visual impairment, it can be removed by superficial keratectomy.  3. Interstitial or deep keratitis Interstitial keratitis indicates inflammation of stroma, Descemet's membrane and endothelium.  3. Interstitial or deep keratitis Causes Extension of infection from superficial layer of cornea or sclera or secondary to anterior uveitis. Extension of infection from a focus in animal body as; diseased tooth, gingivitis, tonsillitis or prostatitis. Systemic disease such as canine distemper & infectious hepatitis in dogs, leptospirosis in horses & pink eye disease in cattle. Traumatic injuries. Neoplasia.  3. Interstitial or deep keratitis Symptoms Corneal opacity due to edema and cellular infiltration. Deep vascularization of the cornea Conjunctival and ciliary injection of blood vessels is usually evident. Hypopyon may be present.  3. Interstitial or deep keratitis Treatment Topical application of atropine sulfate 1% solution. Corticosteroids locally and systematically. Be sure that ulceration of the cornea is absent. Broad spectrum antibiotics locally and systematically especially when bacterial infection is suspected.  4. Ulcerative keratitis It means inflammation of the cornea with formation of corneal ulcer. Corneal ulcer is a lesion in which the epithelium and a variable amount of stroma have been lost. It is usually accompanied by infection of the cornea and the ulcer is chronic and heals slowly or do not heal.  4. Ulcerative keratitis-Causes 1- Mechanical causes Abrasions. Trichiasis, distichiasis and ectopic cilia. Foreign body injury. Exopthalmia and exposure keratitis. Entropion. Tumor of the lid margin.  4. Ulcerative keratitis-Causes 2- Infectious causes Bacterial;S treptococci, Staphylococci, E. coli, and Moraxella. Viral; Canine distemper and herpes virus in dog and cat. Mycotic. Chlamydial.  4. Ulcerative keratitis-Causes 3- Metabolic causes Vitamin A deficiency. Senility. Keratoconjunctivitis sicca. 4- Neurotrophic causes Paralysis of the ophthalmic branch of the trigeminal may be the cause.  4. Ulcerative keratitis-Causes 5- Allergic causes It is very rare and the ulcer usually present near the limbus. 6- Hereditary causes Certain breeds of dogs especially those having prominent eyes have a hereditary predisposition for corneal ulceration. 7- Burns  4. Ulcerative keratitis-Symptoms q Severe pain is manifested by blepharospasm & photophobia with partial or complete closure of eyelids.  Serous, mucopurulent or purulent discharge.  Loss of transparency of the cornea.  Corneal opacity due to edema or cellular infiltration is usually observed around the ulcer or affects all cornea.  4. Ulcerative keratitis-Symptoms  Vascularization of cornea is the natural response to corneal damage. Superficial & deep vascularization is observed according to type of ulcer.  Presence of ulcer its self is diagnostic. The contour of cornea is changed.  Deep ulcers are easily seen but superficial one needs fluorescein dye for staining.  4. Ulcerative keratitis-Diagnosis 1- Clinical symptoms 2- Staining with nonvital stain as fluorescein, impregnated papers are used or 0.5 - 2% solution. Fluorescein is water soluble and will not penetrate the intact corneal epithelium. If the epithelium is disrupted, fluorescein will stain the corneal stroma with green color.  4. Ulcerative keratitis-Treatment  Elimination of the possible cause.  Control of infection. In bacterial infection, broad spectrum antibiotics as gentamycin neomycin or polymyxin and bacitracin. In viral infection, is treated by idoxuridine drops 0.1% every 1-2 hours or 0.5% ointment 3-4 times daily. In Mycotic infection, is corrected by pimaracin. In chlamydial infection, use erythromycin and gentamycin.  4. Ulcerative keratitis-Treatment  Atropine 1% solution 3-4 times daily to relieve pain.  Cauterization by using tincture of iodine or phenol for sterilization of the ulcer. It is important to cauterize the ulcer and 1 mm area of surrounding margin.  Third eyelid flap and /or conjunctival flap.  Superficial keratectomy. Keratitis with chemosis and Superficial corneal mucoid discharge in cat vascularization in a dog with keratoconjunctivitis sicca. Deep corneal ulcerin a dog. Note also the superficial vessels and diffuse corneal edema.  “Pannus” (chronic immune-mediated Superficial vascularization (pannus) in keratoconjunctivitis syndrome) in a dog. a dog Pigmentary keratitis Pigmentary keratitis with healed corneal ulcer in a cow Superficial punctate keratitis in a dog. Deep corneal ulcer in a dog Deep stromal ulcer with diffuse corneal edema, deep Úlcera corneal vascularization, and stromal white blood cell corneal perforada infiltration. There is also hypopyon ventrally. en un Boston terrier.  hypopyon Deep corneal stromal abscess. Stromal abscess Note the superficial corneal formation. vascularization, ventral anterior chamber hypopyon, diffuse corneal edema.  Corneal epithelial cyst Dendritic corneal ulcers in a cat. These Corneal sequestrum in a cat. Note also the lesions are considered pathognomonic surrounding corneal edema and for feline herpesvirus infection. vascularization. Uso de fluoresceína para demostrar ulceración corneal. Corneal ulcer Note that the fluorescein stain adheres only to the walls of the ulcer; the center of the ulcer fails to take up stain Corneal granuloma due to corneal Corneal granuloma in a erosion dog  Sequellae of Corneal Ulceration  1- Scar formation Corneal scars are termed nebula, macula and leucoma according to its size and density. Treatment In most cases no treatment has been recommended as the scar does not interfere with vision. In large leucomas, corneal graft is the treatment of choice.  2- Descemetocele (keratocele) Protrusion of the Descemet's membrane through the floor of a deep corneal ulcer forming a small transparent vesicle.  Due to the pressure of the aqueous humour and not ruptured due to its elasticity.  Sometimes the protruded membrane is covered by fibrinous exudate and corneal epithelium.  2- Descemetocele (keratocele) Treatment  Reposition of protruded membrane back with an iris spatula or blunt instrument then wound is sutured by one or two interrupted stitches.  When the cause is a deep ulcer, paracentesis of anterior chamber is required to relieve pressure over the membrane.  Nictitating membrane flap is placed over cornea for 10 - 14 days.  Topical antibiotic and 1% atropine ointments.  3- Iris prolapse Protrusion of iris through ruptured corneal ulcer or penetrating corneal wound. The iris is carried forward into the corneal defect by the escaping aqueous humour.  3- Iris prolapse Treatment  The wound is flushed with boric acid solution and the iris is re-deposited into the anterior chamber or it amputated if it appears unhealthy.  The corneal wound can be sutured after trimming of the edges of the wound.  Third eyelid flap is applied for 10-14 days  Topical antibiotics and atropine ointments are applied for several successive days.  4- Iris staphyloma Protrusion of a part of the iris through the ruptured corneal ulcer and the protruded part is covered with fibrin and layer of epithelium. Adhesion usually present between the protruded part of iris and the edges of corneal wound.  4- Iris staphyloma Treatment  Protruded part of iris is excised & iris spatula is used to free adhesions between iris and edges of the ulcer.  Wound edges are trimmed with care and then are apposed with simple interrupted sutures.  Sterile saline solution and air is injected into the anterior chamber to restore it.  A nictitating membrane flap is then performed.  Topical antibiotic and atropine is applied.  5- Hypopyon Accumulation of inflammatory exudate at the ventral part of the anterior chamber. It usually occurs in cases of severe corneal ulceration with secondary iridocylitis. Treatment Paracentesis and aspiration of the inflammatory exudate, or injection of alfapsin enzyme intracameral. Hypopyon, due to acute anterior uveitisin a Hypopyon due to severe uveitis in cat, note the intraocular hemorrhage, and a horse the iris has intense congestion and edema Hypopyon in the ventral anterior chamber in a dog Iris staphyloma in a cow  6- Anterior synechia Adhesions between the iris and corneal endothelium. Treatment Application of atropine 1% may relieve the condition. Surgery may be recommended to remove the adhesions.  7- Panophthalmitis Severe purulent inflammation of the eyeball. Treatment Enucleation; removal of eyeball only, leaving extra-ocular muscles and surrounding structures intact (subconjunctival ablasion). Removal of eyeball is sometimes accompanied by removal of part of eyelid, third eyelid, and conjunctiva (transpalpebral enucleation). Exenteration; removal of all contents of orbital cavity (globe, conjunctiva, extra-ocular muscles, and all surrounding structures within the orbit) In case of extensive neoplastic and septic conditions of the globe and orbit (retrobulbar neoplasms and panophthalmia). Evisceration; removal of the contents of the globe. For insertion of ocular prothesis  B. Lipid corneal degeneration deposition of lipid in corneal stroma in association with elevated serum level of lipid and systemic metabolic lipid disturbances. The opacities may occur in any area of the cornea and seldom progress to cause total blindness.  B. Lipid corneal degeneration The cause is not understood and the condition is commonly occurs in adult dogs. It is unilateral or bilateral phenomena. A few cases are associated with hypercholesterolemia and hyperlipemia. Treatment is not usually indicated except in severe cases, Superficial keratectomy is the treatment of choice. C. Corneal wounds and lacerations Corneal wounds and lacerations are quite common in domestic animals and fortunately the majority does not perforate. Causes Cat scratches. Accidents, fighting or contusion to the eye. Striking of the eye against a whip, stick or other objects. C. Corneal wounds and lacerations Corneal wounds and lacerations are quite common in domestic animals.  Superficial wounds  Deep wounds  Perforating wounds Causes Cat scratches. Accidents, fighting or contusion to the eye. Striking of the eye against a whip, stick or other objects.  D. Infectious bovine keratoconjunctivitis (IBK) IBK is one of the most common diseases in cattle throughout the world and is of major economic importance in beef and milk producing animals. The disease is characterized by excessive lacrimal discharge, conjunctivitis, and keratitis. It is also called pinkeye, contagious ophthalmic and new forest disease.  D. Infectious bovine keratoconjunctivitis (IBK) Causes  Moraxella bovis( transmission by direct contact as well as by mechanical vectors such as flies (house fly, face fly and stable fly)  In Egypt, other microbial agents have been isolated such as mycoplasma, rickettsia, viruses and listeria.  Older cattle appears more resistant than younger cattle.  Cattle less than two years old have the highest morbidity.  D. Infectious bovine keratoconjunctivitis (IBK) Symptoms  The earliest signs of the disease are epiphora, blepharospasm and photophobia. Conjunctival hyperemia and chemosis particularly of the bulbar conjunctiva occur.  After two days the affected eye may exhibit a white pale spot near the center of the cornea. The opaque area enlarged and elevated within the next 2 days or slough leaving a shallow ulcer.  D. Infectious bovine keratoconjunctivitis (IBK) Symptoms  Corneal opacity appears around the ulcer and a mild to severe anterior chamber aqueous humour flare and iridocyclitis is usually detectable.  By the ninth day a typical picture of the disease is clear include a well defined ulcer, annular area of corneal opacity and corneal vascularization.  D. Infectious bovine keratoconjunctivitis (IBK) Symptoms  The repair process starts after 10-15 days and acute symptoms subside. The corneal opacity tends to clear from the periphery to the center. The ulcer fills with granulation tissues and heals leaving a slightly raised dense scar.  After one to two months a faint localized corneal scar is formed and surrounded by complete corneal transparency in uncomplicated cases.  D. Infectious bovine keratoconjunctivitis (IBK) Treatment:  Treatment is better to be started early to avoid the progressive corneal changes.  Flushing of the eyeball with cleansing solution.  Topical and subconjunctival injection of antibiotics. Chloramphenicol is effective in eliminating M. bovis from the affected eyes. Also sulfadimidine given intravenously is effective for treatment.  D. Infectious bovine keratoconjunctivitis (IBK) Treatment:  Nictitating membrane flaps are very useful in the treatment especially when a deep ulcer is present. The flap provides mechanical support to the diseased cornea and may help close and seal perforated corneal ulcer.  D. Infectious bovine keratoconjunctivitis (IBK) Treatment:  Complete temporary tarsorrhaphy is indicated over the third eyelid flap and is achieved by closure of the eyelids with 4-6 interrupted horizontal mattress sutures using nonabsorbable suture material.  Isolation of the affected animals, quarantine measures and disinfection of the stables are important.  E. Corneal edema It is a rare condition in animals and not specific disease Causes Endothelial decompensation it may be non inflammatory due to persistent pupillary membrane, congenital glaucoma, penetrating foreign body and post surgical interference or inflammatory due to infectious hepatitis, post vicinal hepatitis reaction, iridiocyclitis and episcleritis.  E. Corneal edema Causes Increased intra ocular pressure in acute and chronic glaucoma. Epithelial discontinuity: due to mechanical trauma and physiochemical damage such as exposure radiation, hypotonic solution, drugs and burns.  E. Corneal edema Treatment 1. Medical therapy: Includes topical corticosteroids and osmotherapy. 2. Sugical therapy: includes conjunctival flap and partial keratoplasty..  F. Corneal tumors Primary tumors of the cornea are rare. Most of them are secondary extensions from other ocular structures. Melanoma, hemangiosarcoma, epithelioma, Fibrosarcoma, viral papillomatosis and histocytoma are the most common recorded tumors. Treatment 1. Superficial keratectomy. 2. Corneal - scleral transplantation. 3. keratoplasty.