LEC 8 - Eyes Flashcards
What are the four possible entry into the cornea?
Destruction of corneal epithelium
Penetration of corneal stroma
Diffusion intro stroma via limbal blood vessels
Injurt to corneal endthelium
What are three examples that cause injury to the corneal endothelium?
Gluacoma
Lens luxation
Leukocyte mediated injury
What is the main method by which there is entry into the uvea?
Hematogenous
What are the three hematogenous routes that go into the uvea?
Toxins
Infectious agents
Neoplastic emboli
What are the methods of defense in the cornea?
Intact corneal epithelium
Leukocytes
What about the corneal epithelium protects the cornea?
Constant washing of corneal surfaces
Tears rich in antimicrobial substances
Surface mucus inhibits bacterial colonization
What are the three antimicrobial substances in tears?
IgA
Lysozyme
Lactoferrin
What are the three mechanisms by which the uvea are protected?
Scelra/Bony orbit
Blood ocular barrier
Anterior chamber immune deviation
What is the blood ocular barrier?
Tight junctions between:
Endothelial cells of iris + Retinal blood vessels
Epitheliaum of non-pigmented ciliary epithelium + RPE
What is ACAID?
Immune response by which infectious agents that enter into the anterior chamber induce a highly controlled immune response
What are the benefits of the ACAID response?
Minimal tissue damage
Very strong response
Why is the uveal tract no protected agains noxious agents in circulation?
It has free communicationwith peripheral blood
When an antigen enters the eye how are T cells activated? Why?
NO lymphoid tissue in eye
APC’s exit normal aqueous outflow and go to marginal zones in the spleen
T lymphocytes are then activated
What does the blood-eye barrier in the retina consist of?
Tight junctions between
RPE cells + Retinal vascular endothelium
What is different about the retina in regards to immune defense compared to the rest of the eye?
No real defense at all against infectious agents, radiation, or noxious chemicals through the vitreous
What are the two major pathological processes in which the cornea responds to injury?
Adaptive cutaneous metaplasia
– and –
Epithelial/Stromal Necrosis
When does adaptive cutaneous metaplasia normally occur with corneal injury?
Mild persistant irritation
What common eyelid disease causes adaptive cutaneous metaplasia in the cornea?
Entropion
What is entropion?
Inversion of the margin of the eyelid
What is adaptive cutaneous metaplasia a combination of? (5 processes)
Keratinization
Epithelial hyperplasia
Epithelial pigmentation
Subepithelial fibrosis
Vascularization
Define: Corneal ulceration
Full thickness epithelial loss
How does edema occur with ulcerations of the cornea?
Water is absorbed from tear film into the anterior stroma
What is the hallmark of corneal ulceration? How does it manifest?
Edema
Opacity
What is the diagnostic technique to diagnosis a corneal ulceration?
Fluorescein dye
What is the severe form of corneal ulceration, that occurs once bacteria is present?
Neutrophil-induced keratomalacia
aka Melting ulcer
What happens to the eye once there is a melting ulceration? Describe.
Desmatocele
Decemet’s membrane bulge anteriorly into defect created
Term: Inflammation of the cornea
Keratitis
What happens if the Decemet’s membrane ruptures?
Can lead to the loss of anterior chamber fluid
– and –
Iris prolapse
What bacteria can cause suppurative keratomalacia in a horse?
Pseusdomonas spp.
What is the process by which suppurative keratomalacia occurs in a horses eye?
Proteolytic destruction of the stroma
Caused by digestive enzymes that are released by the neutrophils in the inflammatory exudate
How does a wound in the eye heal if there is only epithlial damage?
epithelial sliding
– and –
Mititotic regeneration
If there is full thickness destruction in the cornea what do the epithelial cells first release? What do these cause?
IL-1 (cytokine) + PDGF (Growth Factor)
Cause: Necrosis + Apoptosis of Stromal Cells
If there is full thickness destruction in the corneal what do the epithelial cells at the margins of the ulcer release? What do these do?
EGF + KGF + HGF
Stimulated epithelial migration + Proliferation
What is the result of the KGF + HGF + EGF release in a corneal ulceration?
Flattening + Sliding of viable suprabasilar epithelium
Where do the neutrophils in corneal wound healing come from? What do they do?
Come from: Tear film + Limbus
Recruit blood vessels + Fibroblasts
Term: Hypopion
Accumulation of Neutrophils + Fibrin
Settles ventrally in the eye
Term: Anterioir Uveitis
Inflammation within Iris + Ciliary body
Term: Choroiditis
Inflammation only in choroid
Term: Hyalitis
Inflammation in vitreous
Term: Panuveitis
Inflammation throughout uveal tract
Term: Endopthalmatis
Inflammation involving uveal tract + adjacent ocular cavities
Term: Panopthalmatis
Inflammation spreads to scleara
What are the three major causes of uveitis?
Infectious agents
Immune-mediated reactions
Trauma
What does trauma to the uvea cause?
Transient endopthalmatis
What is the most common immune mediated reaction cause by in the Uvea?
Lymphoplasmacytic
What virus in a cat can cause hypopyon?
Feline infectious peritonitis
What are the eight types of delayed responses to injury in the uvea?
Synechiae
Iris bombe
Retinal detachment
Cataracts
Corneal endothelialitis
Preiridal fibrovascualr membrane
Hyphema
Phthisis bulbi
Term: Phthisis bulbi
Shrunken disorganized endstage globe
Term: Hyphema
hemorrhage within the anterior chamber
Term: Preiridal fibrovascular membrane
Layer of granulation tissue of the anterior surface of the eye
What can happen if preiridal fibrovascular membrane migrates across the anterior surface of the lens?
Pupillary block occurs
Secondary gluacoma occurs
What can happen if preiridal fibrovascular membrane migrates across the anterior surface of the filtration angle?
Anterior synechiae
Term: Corneal endothelialitis
Inflitration of neutrophils + lymphocytes into corneal endothelium
How does corneal endothelialitis manifest as?
Corneal edema
aka blue eye
What are some causes of corneal endothelialitis?
Cats = FIP
Dogs = Canine adenoviral hepatits
Term: Cataracts
Lens opacity due to drop in production of aqueous humor
What is an important job of the aqueous humor?
Provide nutrients to the lens
What is cataracts a sequela to?
Uvetitis
What is retinal detachment a sequlae to?
Uveitis
– and –
Endopthalmititis
What are the two mechanisms that retinal detachment can occur?
Exudative
– and –
Tractional
Describe exudative detachment of the retina
increased vascular permeability within the choroid
Leads to:
Effusion of fluid + cells into the subretinal space
Describe tractional detachment of the retina?
Replacement of fibrinous exudate by fibrous tissue within vitreous
Term: Iris bombe
Bowing of iris due to increased pressure within posterior chamber in the presence of circumferential synchiae
Term: Synechiae
Adhesion between the inflammation between the inflammed sticky and either the lens or the cornea
What is invovled in a anterior synechiae?
cornea
What is involved in a posterior synechiae?
Lens
What is the progression of the adhesions in Synechiae?
Fibrinous to fibrous
What happens when synechiae becomes extensive?
Impairment of aqueous outflow from posterior to anterior chamber
= Pupillary block –> Secondary gluacoma
Term: Hematogenous retinal detachment
Leakage of liquefied vitreous subretinal space
Term: Anopthalmia
No detectable development of even primary optic vesicle
Noramlly bilatteral
Term: Micropthalmia
Minature, disorganized globe in an orbit of normal size
What are possible causes of micropthalmia?
Exogenous injury to the globe
Utero trauma + Ischemia injury + Infections
Term: Cyclopia
Failure of division of very primative optic primordium into paired symmetirc optice stalks + vesicles
Term: Synopthalmia
Cyclopia
with replication of intraocular structures
(ie. retina or lens)
What can cause cyclopia in ewes?
Veratrum californicum
Day 15 gestation
Term: Coloboma
Defect in closure of the optic fissure
Retina grows outwardly
What is coloboma a hallmark of?
Collie eye abnomaly
Describe the process of glaucoma.
Increase in intraocular fluid pressure
Detrimental to health of optic nerve + retina
What are the end results of glaucoma?
Decrease in vision
Evenutally blindness
What causes primary glaucoma?
Ocurring without any known aquired intraocular disease
Developmental errors
What is one malformation that can cause primary glaucoma?
Goniodysgenesis
Term: Goniodysgenesis
Imperfect developemnt of trabecular meshwork
What are three examples of things that can cause secondary glaucoma?
pupillary block
trabecular occulsion
tumors
How can a trabecular occulsion occur?
Infiltration of neoplastic cells
Peripheral iridiocorneal adhesions
mechanical compression of the base of the iris
What are two tumors in dogs that can cause secondary gluacoma?
Anterior uveal melanocytoma
– and –
Metastatic lymphoma
What are two tumors in cats that cause secondary glaucoma?
iris melanoma
– and –
Metastatic lymphoma
What are the eight secondary changes with glaucoma?
Bupthalmos
Corneal edema
Corneal striae
Atrophy of iris + ciliary processes
Cataracts
Lens luxation
Retinal degeneration
Optic nerve changes
Term: Buphthalmos
Stretching of the globe secondary to increased intraocular pressure
Term: Corneal striae
breaks in the Descement’s membrane secondary to corneal scratching
Why is there atrophy of the iris and cilliary process with glaucoma?
Due to chronic pressure induced ischemia
What is the clinical sign that there has been atrophy of the iris?
Permanent dilation of the eye
Define: Lens luxation
Due to stretching of the zonules secondary to ocular enlargement.
Pressure induced degenerative changes in zonules
What is the most important secondary change with glaucoma? Why?
Retinal degeneration
This is where most glaucoma treatments are targeted
What are the contribution factors in glaucoma that cause retinal degeneration?
Pressure induced ischemia changes
Interference with ganglion cell nutrition
Direct damage to ganglion cells by elevation local production of excitatory AA’s
What causes the optic nerve changes in glaucoma?
Posterior displaced of lamina cribosa
– and –
Cupping of optic disc
How is a dermoid formed?
Failure of the fetal ectoderm to undergo corneal metaplasia
What causes superficial stromal sequestration?
Injury to corneal epithelium followed by increase in amount of superficial stromal apoptosis
In dogs and horses, what is the result of superficial stromal apoptosis?
Inability of sliding corneal epithelium to properly adhere to underlying stroma, meaning full epithelial regeneration cannot occur
In cats, what is the result of superficial stromal apoptosis?
Stromal devitalization is normally greater
Imbition of brown-colored pigemnt into dead stroma
What is the pathognomonic feature of corneal sequestrum in a cat?
Brown-colored pigment
What are the four common systemic mycoses that affect the eye?
Blastomycosis
Cryptococcosis
Histoplasmosis
Saprophytic fungi
What species of blastomycse?
Dermatitidis
What species of cryptococcus?
neoformans
What species of histoplasma?
capsulatum
What species of saprophytic fungi?
Aspergillus + Candida
What does balstomyces cause?
Dogs
Severe diffues pyogranuloatous endopthalmitis
What does cryptooccus neoformans cause in the eye?
Lesions mostly in the retina + choroid + optic nerve
Minimal granulomatous response
Cats + Dogs
What does histoplasmosis capsulatum cause?
Diffuse granulomatous + lymphocytic choroditis with little suppuration
When causes lens induced uveitis?
Cataracts
How do cataracts cause uveitis?
lens proteins begin disintegrate + leak through intact lens capsule
= Phacolytic uveitis
What is seen in dogs with phacolytic uveitis?
Suppurative to pyogranulomatous reaction centered around the lens
What animals are uveal neoplasms most common?
Dogs and Cats
What are the primary tumors of the eye?
Melanocytic
– and –
Iridiocillary epithelail tumors
What is the most common canine primary uveal tumor?
Canine aterior uveal melanocytoma
What does anterior uveal melanocytoma arise from?
Melanocytes within the stroma of the iris + ciliary body
What is the clinical presentation of feline diffuse iris melanoma?
Unilateral coalescing hyperpigmentation of iris
Slowly progressing to thickening + secondary glaucoma
Where do irdiociliary tumors come from?
neuroectoderm of posterior iris or ciliary body
What causes feline primary ocular sarcoma?
Spindle cell neoplasm
Arises from lens epithelium that espcased through ruptured capsules
What is normally the end result of a completely dislocated lens?
Cataract
Why does a cataract result from the complete dislocation of the lens?
inadequate access to aqueous humor
What causes a primary lens luxation?
Occurs without any known trauma
Developmental error that causes abnormal or insufficent zonules
What causes a secondar lens luxation?
Blunt trauma
Avulsion of zonules
– or –
Excess stretching of zonules
What is thought to be the reason for diabetic cataracts?
Excessively high level of glucose within the aqueous humor
What is the basic reason for equine keratomycosis for occurring?
Opportunistic contamination of corneal wounds by fungi
What is the most common fungus to cause equine keratomycosis?
Aspergillus
What are the the two different things that can occur with equine keratomycosis?
Infection of dead superficial stroma by large amount of hyphae with almost no inflammation
– or –
Deep stromal infection that evokes intense suppurative keratomalacia
If keratomalacia occurs with equine keratomycosis what can it lead to?
Corneal perforation
– and –
Iris prolapse
What is Equine recurrent uveitis?
Unpredictable episodes of severe uveitis
Increase in frequency
Immunologic reaction against intraocular leptopsiral antigens
What is the cause of infectious bovine keratoconjunctivitis?
Moraxella bovis
What is the vector for moraxella bovis?
Flies
– or –
Fomites
Why does moraxella bovis cause infectious bovine keratoconjunctivitis?
Have capsular pili that are hemolytic
How does infectious bovine keratoconjunctivitis present?
Shallow corneal ulcers
With severe conjunctival hyperemia
–> Circumferential superfical vascular growth
What is the presentation of bovine malignant catarrhal fever-associated uveitis?
Peripheral midstromal corneal vascularization
– and –
Anterior Uveitis
What breed of dog tends to get canine pannus keratitis?
German shephards
Where does canine pannus keratitis begin? How does it spread?
Starts at lateral limbus
Moves to axial cornea
What is uveodermatologic syndrome?
Facial dermal depigmentation
– and –
Severe bilateral uveitis
What breeds are affected by uveodermatologic syndrome?
Akitas
Siberian Huskies
Samoyeds
What is the histologic appearance of uveodermatologic syndrom?
Destructive granulomatous endophtalmitis
Abundant dispersal of melanin
Consequence of T-lymphocyte mediated destruction of melanin producing cells
What virus causes feline herpetic keratitis?
Feline herpesvirus 1
What occurs with feline herpetic keratiits?
Acute to chronic keratitis
Shallow intraepithelial branching tracts of nerocis
= Dendritic ulcers
What is the physical characteristic of eosinophilic keratitis?
Granular, white proliferative lesion extending inward along corneal surface from medial to lateral limbus
What is seen on histologic examimination of eosinophilic keratitis?
Nonulcerative superfical stromal infiltration of:
Eosinophils
Plasma cells
Mast cells
Macrophages
