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Pathology of the Eye and Ear

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Where do the cornea, lens, and eyelids develop from?
surface ectoderm
Where do the extraocular muscles and vascular endothelium develop from?
mesoderm
What are the 5 layers of the cornea?
anterior epithelium, subepithelial basement membrane, substantia propria, posterior limiting membrane, posterior epithelium
The normal iris of the horse has a pigmented mass on its surface called _______ that may be mistakenly identified as a pigmented neoplasm?
corpora nigra
Ocular disease will result in impairment of vision by what 2 methods?
interfering with the light refracting capacity of the eye, or damaging the neural elements of the retina or optic nerve
What can cause blindness?
alterations in the refractory media of the eye, damage to the nervous tissues of the eye, extraocular lesions on the brain
What are clinical expressions of disease in the eye?
blindness, conjunctival discharge, swelling and pain, sensitivity to light, excessive or decreased lacrimation, opacity, exophthalmos, endophthalmos
What is absence of the eye?
anophthalmos
What is presence of a single globe within a single median orbit, due to ingestion of veratrum alkaloids by the ewe at 14 days of ingestion?
cyclopia
What is incomplete seperation, or early fusion, of paired globes?
synophthalmia
What is an abnormally small eye, and inherited defect in collies?
micropthalmia
What is it called when eyelashes rub against the eye surface?
trichiasis
What is a defect resulting from failure of complete fusion of the lips of the embryonic fissure, a slitlike but normal channel in the floor of the optic cup and stalk through which the vasoformative mesoderm and stromal mesenchyme enter the globe?
coloboma
In what animal is colobama an inherited defect seen mainly in the posterior part of the eye?
charolais cattle
What is an anomaly of the mesenchyme, where there is improper development of the optic cup resulting in abnormal formation of choroid and retina, is an inherited as an autosomal recessive trait?
collie eye anomaly
What is delayed or incomplete atrophy of the anterior perilenticular vascular network that, in fetus, originates from the minor arterial circle of the iris and invests the developing lens?
persistant pupillary membrane
What is complete or partial absence of the eyelid, results in localized corneal dessication followed by cutaneous metaplasia?
eyelid agenesis and coloboma
What is defined as the abnormal or prolonged fusion of adhesion of the eyelids?
ankyloblepharon
What is the inward rollinng of the eyelid margin because of inadequate overall length, causes irritation, very common anomaly in purebred dogs?
entropion
What is created by undue laxity of an excessively long eyelid resulting in an outward gaping of the eyelid margin, causes chronic conjunctivitis?
ectropion
What is the presence of an ectropic row of cilia originating from the ducts of the meibomian glands, usually bilateral, causes corneal irritation?
distichiasis
What is misdirection of the normal cilia, causes corneal irritation leading to keratitis and even ulceration?
trichiasis
What is abnormally placed cilia within the lamina propria of the conjunctiva, their emergence through the palpebral conjunctiva can cause severe corneal irritation?
ectopic cilia
What is supportive adenitis of the adnexal glands of moll or zeis or the meibomian gland?
hordeolum (stye)
What is sterile granulomatous inflammation of the meibomian gland?
chalazion
What are types of diffuse blepharitis?
ulcerative, seborrheic, allergic, actinic, and parasitic
What is the most common tumor of canine eyelids, an exact counterpart of sebaceous adenomas seen elsewhere in skin?
meibomian gland adenoma
What are common causes of conjunctivitis?
local trauma, irritants and toxins, infections
What are some examples of congenital anomalies of the eye?
dermoids, extension of the conjunctiva over the cornea, pterygium
What can cause conjunctivitis?
trauma, mechanical irritants, allergens, toxins, infectious agents
What is the conjunctival counterpart of the eosinophilic keratitis syndrome seen in cats and occasionally horses?
idiopathic eosinophilic conjunctivitis
What is nodular lesion of the conjunctival lamina propria in dogs, seen in lateral limbus and 3rd eyelid?
nodular granulomatous episcleritis
What is an idiopathic "immune-mediated" disease in dogs, can be mistaken for NGE, nodular thickening of the bulbar conjunctiva or underlying posterior to the limbus?
necrotic scleritis
What is the most common neoplasm of the conjunctiva in cattle?
squamous cell carcinoma
What is a faint loss of transparency of the cornea, that can be seen with oblique illumination?
nebula
What is a light gray spot on the cornea, that can be visualized in natural light?
macula
What is any dense white spot in the cornea that may indicate moderate to severe corneal disease?
leukoma
What is most pigmentation of the cornea is the result of melanin accumulation, is associated with several conditions, or it may be congenital condition?
melanosis
What are ulcers that become contaminated with bacteria or fungi, that prone to suppurative destructive keratomalacia. Most of the stromal dissolution is the result of bystander injury from neutrophils recruited because of infection?
suppurative keratomalacia
What are portals of entry for corneal injury?
destruction of corneal epithelium, penetration of the corneal stroma, diffusion into stroma from limbal blood vessels, injury to corneal endothelium
What are congenital, developmental anomalies affecting the mucous membrane of the conjunctiva or cornea, it reflects the failure of the fetal ectoderm to undergo complete corneal metaplasia so that a portion of the cornea remains as skin?
ocular dermoid
What is defined as an outpouching of the cornea that is lined by uveal tissue. The lesion generally appears dark brown or black and is probably a result of an embryogenic defect?
congenital anterior staphyloma
What is due to entrapment of groups of epithelial cells in the developing cornea, the lesion is typically opaque white and cystic enlargement may occur?
congenital inclusion cyst
Regardless of cause, keratitis follows sterotyped sequence?
edema, leukocyte immigration from tears and distant limbic venules, corneal stromal vascularization, fibrosis, epithelial metaplasia with pigmentation
What are examples of non-ulcerative keratitis?
epithelial keratitis and stromal keratitis
What type of nonulcerative keratitis is transient and mild, consists of multiple fine epithelial opacities that are foci of epithelial hydropic change, intercellular fluid accumulation is often seen with this?
epithelial keratitis
What can cause ulcerative keratitis?
trauma, dessication, infection, feline herpes virus, immune mediated disease, primary degeneration of the corneal epithelium
What is it called when proteases and collagenases of microbial, leukocytic, or corneal origin liquefy the corneal stroma?
keratomalacia
What is it called when neutrophils may encircle the liquefying focus as a thick wall of live and fragmented cells?
ring abscesses
Stromal liquefaction that reaches the Descemets membrane results in its forward bulging known as?
descemetocele or keratocele
In the case of corneal ulcer perforation, the iris flows forward to plug the defect and subsequently becomes incorporated into the corneal scarring, this defect is a permanent anterior synechia, called?
anterior staphyloma
What is usually due to the opportunistic contamination of corneal wounds by fungi, predisposing factors are alteration of the corneal defenses or the normal microbial environment by prolonged use of antibiotics?
equine keratomycosis
What is the commonest form of keratitis in which there is diffuse blue-gray clouding of the cornea associated with inflammatory changes in deep ulcer layers, usually due to iridocyclitis, and it characterized by deep vascularization?
non-ulcerative keratitis
What form of nonulcerative keratitis has no ulceration but pigmentation is marked, cell mediated injury following prolonged exposure to UV light?
superficial stromal keratitis
What results from extension from anterior uveitis or from endothelial damage by uveitis, trauma, or glaucoma, common in horses which have suffered one or more bouts of equine recurrent opthalmitis?
deep stromal keratitis
What is congenital lack of lacrimal secretion; senile atrophy?
primary keratoconjunctivitis sicca
What is destruction or denervation of lacrimal or accessory lacrimal gland following orbital inflammation, infections, trauma, neoplasia, toxicity, occlusion of lacrimal ducts, hypovitaminosis A?
secondary keratoconjunctivitis sicca
What are corneal dystrophies?
inborn errors of metabolism
What results from previous corneal disease or as incidental manifestations of systemic metabolic abnormalities that have "overflowed" into the cornea?
acquired corneal deposits
What results in milky or crystalline stromal deposits or serum lipids within the corneal stroma, as in an animal very high serum lipid concentration?
corneal lipidosis
What types of corneal foreign bodies are there?
penetrating or nonpenetrating
Why are alkalis chemical burns the most serious to the cornea?
becuase the topical application of an alkali to the cornea results in the immediate death of the corneal and conjunctival cells
What are the portals of entry for uveal injury?
hematogenous, penetrating injury into one or more ocular chambers, via aqueous or vitreous
What is failure of growth of the future iris epithelium, more frequent in horses?
Iris hypoplasia
What is associated with inadequate pigmentation of the retinal pigment epithelium and choroids, is also part of significant developmental anomaly involving the choroid, retina, optic nerve, and sclera?
Choroidal Hypoplasia
What are different causes of uveitis?
ocular trauma, toxicity, neoplasia, immune-mediated, infections, corneal injury, lens induced uveitis
What is a very common mild lymphoplasmacytic anterior uveitis occuring in animals with cataracts in which the lens protein is beginning to disintegrate and leak through the intact lens capsule?
phacolytic uveitis
What is an immune mediated disease in response to the release of large amounts of intact lens protein through a traumatically ruptured lens capsule?
phacoclastic uveitis
In iridocyclitis (anterior uveitis) the presence of fibrin and inflammatory cells in the aqueous may cause it to appear cloudy and the exudate may settle to the bottom of the anterior chamber to produce floccular sediment called?
hypopyon
What is it called in iridocyclitis, where neutrophils adhere to the corneal endothelium producing a stippled appearance?
keratitis punctata
What is often characterized by "mutton fat" keratic precipitates (accumulations of epithelioid and histiocytic cells) and a localized exudative response?
granulomatous uveitis
What is it called when the iris adheres to the cornea?
anterior synechia
What is it called when the iris adheres to the lens?
posterior synechia
Complete posterior synechia involving the circumference of the iris results in blockage of the papillary flow of aqueous with resultant rise in posterior chamber, and the iris bows forward, which is called what?
iris bombe
What is a worldwide and important cause of blindness in horses and mules, blindness results from repeated attacks of the anterior uveitis, causing damage to the choroid, retina, and optic nerve?
equine recurrent opthalmitis (moon blindness)
What is a useful marker for ERU?
presence of eosinophilic hyaline membrane that lies within the apical cytoplasm of the nonpigmented ciliary epithelium and resemble amyloid.
What is the most common histologic pattern seen in uveitis?
idiopathic lymphonodular uveitis
What is a consequence of T lymphocyte mediated destruction of melanin producing cells of the RPE and uvea, causes facial dermal depigmentation and severe bilateral uveitis?
uveodermatologic syndrome in dogs
What is a sustained increase in IOP and usually associated with a decreased draining of aqueous humor, increase production of aqueous can also cause this?
glaucoma
What type of glaucoma is inherited, bilateral disease, usually no ocular disease but malformation of the filtration angle?
primary
What type of glaucoma is due to anything capable of obstructing the flow of aqueous through the pupil or its exit through the trabecular meshwork?
secondary
What are portals of entry into the retina for retinal disease?
hematogenous, traumatic, vitreous, choroid, retinal pigment epithelium, optic nerve, genetics
What is faulty differentiation of the retina, especially photoreceptor cells, and proliferation of one or more of its constituent elements?
retinal dysplasia
Etiology of secondary retinal dysplasia can be from what?
in utero viral infections, vitamin A deficiency, x-ray irradiation, certain drugs, intrauterine trauma
What is it called when there may be focal or diffuse areas of neuronal degeneration with accompanying gliosis and perivascular cuffing?
retinitis
What are specific examples of chorioretinitis with retinal detachment?
thromboembolic meningoencephalitis in cattle, mycobacterial infections in cats and horses, systemic mycoses, protothecosis, and ocular migration of certain ascarids.
What is degenerative changes in the retina (loss of photoreceptors and other retinal neurons) and the formation of spaces within the retina?
retinal degeneration
What are the nutritional deficiencies involved in retinal degeneration?
hypovitaminosis A, taurine deficiency in cats, hypovitaminosis E
What is it called when photoreceptors never reach morphologic or physiologic maturity, and is inherited as a simple autosomal recessive defect?
Generalized progressive retinal atrophies
What is an abnormality in RPE, that occurs in later onset, and is involved in photoreceptor degeneration?
Central progressive retinal atrophies
What is the seperation of the neurosensory retina from the RPE, this expands the potential space between the 2 portions of the retina?
retinal detachment
What is nonattachment of the neurosensory retina as in microphthalmia?
congenital types of retinal detachment
What is the neurosensory retina attached to the vitreous is pulled away as the vitreous shrinks?
tractional type of retinal detachment
What happens when fluid or inflammatory exudate accumulated within the subretinal space?
exudative type of retinal detachment
What happens when the peripheral neurosensory retina tears away from the ora ciliaris retinae?
rhegmatogenous type of retinal detachment
In the developing embryo, deficiency in vitamin A is caused by?
improper growth of cranial bones, increased intracranial pressure, compression of the optic nerves by stenotic optic foramina
What is toxic retinal degeneration seen in sheep grazing hill pasture infested with bracken fern?
bright blindness
In disease of the lens, what are portals of entry?
radiation, perforation, blunt trauma, and via aqueous humor
What is the most common disorder of the lens defined as lenticular opacity, is permanent opacity of the lens resulting from increased hydration due to alterations in nutrition, metabolism, or osmotic balance of the lens?
cataract
What is congenital cataracts due to?
adherence of embryonal vasculature/structures to the posterior lens capsule or fetal BVD infection
What occurs without any known trauma or other ocular diseases, it may be congenital or seen later in life?
primary lens luxation
What almost always follows blunt trauma that causes avulsion of the zonules or excessive stretching of zonules within a globe that has become greatly enlarged secondary to glaucoma?
secondary lens luxation
What is the most common intraocular tumor and is usually malignant?
uveal tract melanoma
What type of adenoma/adenocarcinoma arise from the eyelids and constitute about 50% of eyelid tumors in dogs?
meibomian gland adenoma/epithelioma
What are congenital anomalies in the diseases of the external ear?
macrotia, microtia, anotia, polyotia, atresia, persistant meatul plug
What are different causes of auricular hematoma?
trauma, intrachondral fracture of the pinnal cartilage, predisposition
What is the commonest of the various ear diseases?
otitis externa
What are different causes of otitis externa?
parasite, bacteria, fungi, foreign bodies, hypersensitivity from bites, metabolic disorders, chronic inflammation, autoimmune diseases
The lipid rich environment of the ear canal favors what as the primary pathogen in the causation of canine otitis externa?
lipophilic malassezia
What are different causes of auricular (ear tip) necrosis?
frostbite, ergot poisoning, thrombosis during the course of septicemia, trauma
What are examples of auricular lesions of dermatologic disease?
marginal auricular dermatosis or ear margin seborrhea, auricular alopecia in dogs and in siamese cats, feline solar dermatitis, equine aural plaques
What can be caused by extension of infection through the tympanic membrane from the external ear, or from the nasopharynx in association with upper respiratory infections?
otitis media
What are bacteria that are most often isolated in middle ear disease?
arcanobacterium, pyogenes, pasturella, pseudomonas
What is accumulation of purulent exudate within the guttural pouch following upper respiratory tract infection?
empyema
What is the most dangerous consequence of middle ear disease?
potential for spread to structures of inner ear via round and oval windows
What can be caused by suppurative infection arising as a complication of otitis media or URT infections, or can be spontaneous hematogenous bacterial infections?
otitis interna
What are the consequences of otitis interna?
impaired hearing or deafness due to destruction of organ of corti, loss of balance and nystagmus associated with disturbed vestibular function
What may be due to absence or degeneration of sensory cell hairs in the organ of corti, may be inherited as an autosomal recessive trait and is often associated with white hair coat color?
congenital/hereditary deafness
The hearing defect may be associated with inheritance of what gene?
merling gene
What is a lesion involved in congenital deafness, that is collapse of walls of the cochlear and saccular membranous labyrinth?
cochleosaccular degeneration
What are the types of acquired deafness?
conductive or neurologic
What are examples of etiology of peripheral deafness (lesions involving the cochlea)?
hereditary, toxic, acoustic, inflammatory, neoplastic, senility, storage diseases
What are major examples of causes of otoxicity?
aminoglycoside antibiotics, diuretics, aspirin, hygromycin B, antiseptic savlon
What is characterized by head tilt and falling forward toward affected side, ataxia without weakness and nystagmus?
vestibular dysfunction
What are examples of etiology of vestibular dysfunction disease?
uncontrolled otitis media, labyrinthitis, trauma, invasive neoplasia, drugs, congenital, idiopathic
What is the commonest neoplasm of the ear?
adenoma or adenocarcinoma of the ceruminous glands
What is a tumor arising from the nerve sheath of the 8th cranial nerve?
acoustic neurinoma