Ocular, Pt. 2 Flashcards
What part of the uvea layer contains vasculature?
choroid - darkly pigmented with melanocytes
What is included in anterior uveitis? Posterior uveitis?
iritis (iris) and cyclitis (ciliary body) = iridocyclitis
choroiditis (commonly an extension from anterior uveitis)
What is endophthalmitis? Panophthalmitis?
inflammation of the chamber, commonly due to leakage from uvea
inflammation of the sclera, cornea, and retina
What results from the increased vascular permeability resulting from uveitis?
- iris = diffusion into aqueous humor (aqueous flare)
- ciliary body = distension and cysts
- choroid = edema
- retinal pigment epithelium (RPE) = exudative retinal detachment
What is aqueous flare?
uveitis increases the permeability of the iris, leading to leakage of proteins, fibrin, cells, and blood into the anterior chamber
What is the result of fibrin exudation caused be uveitis?
formation of sticky adhesive membranes (synechiae) that block the filtration barrier and cause glaucoma
Uveitis:
- swollen and edematous cornea
- cloudy vitreous humor due to protein and precipitation
Uveitis:
- fibrin and proteinaceous accumulation causes the thickening of lens and cornea
- pupillary block
- retinal detachment
How does uveitis affect the cornea? What does this commonly result in?
edema (opacity) and keratic precipitates of leukocytes and fibrin
anterior synechiae where the iris adheres to the cornea
What does uveitis commonly cause the formation of? What causes this?
pre-iridal fibrovascular membranes - fibroblasts and vessels in anterior chamber that obliterates the filtration angle
vasogenic compounds
How does uveitis affect the lens and retina?
alters the aqueous humor (malnutrition) causing cataracts
detaches due to membrane traction and subretinal exudation
In what animals is lens-induced uveitis common? What are the 2 clinical syndromes?
dogs
- phacolytic: intact capsule with diffusion of soluble antigenic lens proteins (LEAKAGE)
- phacoclastic: ruptured capsule (BLAST) causes the exposure of lens epithelium and fibers
How does phacolytic uveitis commonly present? What are some complications?
cataracts due to the swelling, edema, and protein leakage —> capsule remains intact!
corneal vascularization, PIFM, synechiae, secondary glaucoma
What is phacoclastic uveitis? What are 3 common causes? What is characteristic?
sudden release of lens contents into chambers due to ruptured capasule
- spontaneous - intumescent cataracts
- trauma - blunt, penetrating
- infection - encephalitozoonosis in rabbits
intense lens-centered inflammation - suppurative, fibrinous, (pyo)granulomatous
Phacoclastic uveitis:
- abnormally shaped lens
- necrosis and fiber breakdown
- ruptured capsule with eosinophilic protein and fibers
Phacoclastic uveitis:
fibrin and proteins in lens
Phacolytic vs phacoclastic uveitis:
What is uveodermatological syndrome? In what animals is it most common?
Vogt-Koyanagi-Harada-like syndrome, an autoimmune bilateral cellular and humoral response against melanin
canine arctic breeds, like Akitas, Siberian Huskies, Samyoeds, and Alaskan malamutes
What is characteritic of uveodermatological syndrome? How does this specifically affect the eyes?
depigmentation of the choroid, iridociliary epithelium, skin/hair, and mucous membranes
granulomatous choroiditis causes exudative retinal detachment, diffuse uveitis/endophthalmitis, PIFM and glaucoma
Uveodermatologic (VKH) syndrome:
- uveal thickening
- macrophage invasion
- retinal detachment
Uveodermatologic (VKH) syndrome:
macrophages invading the uvea (choroid, iris, ciliary body)
What is the most common uveitis in cats? What is thought to be the cause? What is the most common sequelae?
feline lymphoplasmacytic uveitis
non-specific immune reactions to Toxoplasma, Bartonella, FeLV, or FIV
glaucoma
What non-specific changes are seen in feline lymphoplasmacytic uveitis? What is a gross indication?
- perivascular infiltrates of lymphocytes and plasma cells mostly within the anterior uvea
- changes of glaucoma
Busacca nodules indicative of the lymphocyte and plasma cell accumulations
Feline lymphoplasmacytic uveitis:
- Busacca nodules = lymphocytes + plasma cells
- inflammatory cells obstruct filtration angle
What causes equine recurrent uveitis? What is the most common sign? How does it affect the horse?
immune-mediated disease due to hypersensitivity to Leptospira interrogans serovar Pomona
bilateral uveitis resulting in glaucoma and cataracts (blue eye due to corneal edema)
causes blindness and pain
Equine recurrent uveitis:
- white material = inflammatory cells and fibrin
- cloudy vitreous
- amyloid-like accumulations thickening the ciliary body
Equine recurrent uveitis:
- abnormal ciliary body
- fibrin and inflammatory cells in anterior chamber
What is characteristic on histology of equine recurrent uveitis?
amyloid-like material covering ciliary body stains positive with Congo Red and is birefringent green
What commonly causes viral uveitis in cats? What kind of inflammation does it cause? How does it affect the eye?
feline infectious peritonitis virus
lymphoplasmacytic or pyogranulomatous uveitis
systemic vasculitis causes fibrinous exudate to leak into the aqueous and vitreous chambers and coagulate the fluids and blood vessel necrosis
FIP, uveitis:
inflammation in iris
What is a common cause of viral uveitis in dogs? What causes it? What is the most common cause?
canine adenovirus-1
type III hypersensitivity to infection or vaccination with live modified virus
diffuse corneal edema (blue eye)
What is the most common cause of viral uveitis in cows? What does this cause? How does this affect the eyes?
bovine malignant cararrhal fever (MCF), ovine herpesvirus-2
systemic vasculitis with lymphoid proliferation and necrosis
endophthalmitis du to arterial fibrinoid necrosis and lymphoplastic perivascular infiltration
What are the 2 causes of bacterial uveitis/endophthalmitis? What is commonly seen on histology?
- EXOGENOUS: penetrating wounds, progression from corneal ulcers
- ENDOGENOUS: R. equi and strangles common in horses
hypopyon due to neutrophil accumulation in the chambers and subretinal space +/- fibrin accumulation
Bacterial uveitis, hypopyon:
neutrophils in anterior chamber
What are the 4 most common causes of fungal uveitis/endophthalmitis? How does it typically reach the eyes?
- Blastomyces dermatitidis
- Cryptococcus neoformans
- Coccidioides immitis
- Histoplasma capsulatum
inhalation —> hematogenous —> extends from CNS
What clinical and histologic lesions are seen in fungal uveitis/endophthalmitis?
- plasmoid aqueous/vitreous, exudative retinal detachment
- (pyo)granulomatous endophthalmitis —> increased choroid/subretinal space
What is pre-iridal fibrovascular membranes (PIFMs) secondary to? What is its pathogenesis?
uveitis, retinal detachment, trauma, glaucoma, intraocular neoplasia
- hypoxic retina or neoplastic cells secrete vasogenic factors (VEGF)
- as vascular buds arise from iris stroma and matures into a fibrous membrane
- membrane proliferates over tissue surfaces of the anterior and posterior iris, ciliary body, lens capsule, and pectinate ligament
Normal iris vs PIFM:
- NORMAL: melanocytes on anterior surface
- PIFM: fibroblasts and vasculature
What are 4 complications of pre-iridal fibrovascular membranes (PIFMs)?
- outflow obstruction
- secondary glaucoma
- synechiae
- intraocular hemorrhage due to the leakage of immature vessels (hyphema)
What is the most common intraocular neoplasm? What parts of the eye are most affected? How does it typically progress?
canine uveal melanocytoma
anterior uvea and choroid
slowly grows into adjacent tissue and chambers causing tissue necrosis and distortion (mass-occupying!)
Canine uveal melanocytoma:
- inflammation obliterates filtration angle
- L = uveal
- R = choroid
What is a common result from canine uveal melanocytoma? How does the new progression compare to the original neoplasia?
uveal malignant melanoma (more commonly found in anterior uvea)
- less pigmented (amelanotic)
- anaplastic: anisokaryosis, pleomorphism, large nucleoi
- high mitosis count
- some metastasis
What is the most common malignant uveal neoplasia in cats? How does it present? What does it cause? Why is early treatment recommended?
feline diffuse iris melanoma
golden or brown hyperpigmentation that is confined to the anterior surface of the iris and can coalesce and thicken over months to years —> obstructs filtration angle = glaucoma
enucleation - risk of metastasis to liver, lung, and kidney
Feline diffuse iris melanoma progression:
multifocal to coalescing —> diffuse
Feline diffuse iris melanoma:
- thick iris
- subtypes
What is the function of the lens? How must it be structurally to be able to do this?
refractive power sends light to retina
TRANSPARENT - avascular, no pigmentation, dehydrated (nutrition depends on aqueous humor)
What is the function of the lens epithelium? What kind of metabolism does it rely on?
pumping water out of lens
passively absorbs glucose from the aqueous humor (avascular!) and performs anaerobic glycoysis (hexokinase pathway)
What happens to the lens upon inflammation? How is the lens kept in place?
proteins sequestered from the immune system are released
zonular ligaments connect it to ciliary bodies
What are the 2 major components of the lens?
- capsule - secreted by lens epithelial cells
- epithelial cells - cuboidal to columnar, only present in the anterior, form lens fibers
What are the 2 aging changes seen in the lens?
- nuclear/lenticular sclerosis - inner lens fibers condense, causing haziness (not true opacity) and may affect vision depending on viscosity
- senile cataracts - cortical cataractous changes result in opacity and tend to affect vision
What are cataracts? How care they classified?
pathologic opacification (fibers and/or capsule)
- onset (congenital/juvenile, developmental/senile)
- progression
- extent (incipient, immature, mature, hypermature)
What are the 4 characteristics of cataract histopathology?
- Morgagian globules - smooth hyalinized spheres of denatured proteins that cause the lysis of lens fiber cell membranes
- bladder cells - swollen nucleated lens epithelial cells
- mineralization
- capsular wrinkling due to cortical liquefaction of hypermature cataract
What is the most common etiology of cataracts?
anything that causes a decrease in quality of aqueous humor
- anterior uveitis: inflammatory cells in AH
- congenital
- trauma
What are the 3 most common causes of cataracts in dogs?
- systemic metabolic disease (DM) - glucose is taken up by the lens, increasing the uptake of water
- retinal disease - retinal cells secrete inflammatory cells into AH
- hereditary/juvenile cataracts*
What primary infection commonly causes cataracts? What does infection cause?
Encephalitozoon cuniculi in rabbits
active penetration and proliferation of the fungus within the lens destroys lens fibers and causes phacoclastic uveitis
What is lens luxation? What does it commonly lead to?
separation of lens from zonular ligament from the ciliary body, displacing it anterior or posterior to the iris
glaucoma - obstructs outflow of AH
What is the most common type of lens luxation? What are 5 causes?
secondary
- chronic intraocular inflammation disrupts zonules
- chronic glaucoma causes buphthalmos, which stretches and breaks the zonular ligaments
- hypermature cataract
- senile degeneration of zonular ligaments
- trauma
Anterior lens luxation:
- lens should be slightly posterior to iris
- thin choroid and sclera
