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The uvea is aka the __________.
vascular tunic
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What are the 3 regions of the uvea?
iris, ciliary body, choroid
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What is the anterior most portion of the uvea?
the iris
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What are the functions of the iris? (2)
- regulates the amount of light entering the posterior portions of the eye
- blood aqueous barrier
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Anterior SEGMENT versus posterior SEGMENT
- anterior segment= everything in front of the lens
- posterior segment= behind the lens (vitreous, choroid, retina)
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anterior CHAMBER versus posterios CHAMBER
- anterior chamber= in front of the iris
- posterior chamber= behind the iris
- [both are within the anterior segment]
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What are the muscles of the iris? (2)
- sphincter muscle (smooth muscle under involuntary parasympathetic control)
- dilator muscle (smooth muscle under involuntary sympathetic control)
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Describe the innervation to the sphincter muscle of the iris.
parasympathetic control from CN III
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The iris sphincter muscle can be blocked (causing mydriasis) with ____________, such as... (2)
parasympatholytic agents; topical Tropicamide or atropine
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Describe Horner's Syndrome. (1 cause, 6 signs)
sympathetic denervation of the eye--> miosis, ptosis, enophthalmos, prolapsed third eyelid, ocular hyperemia, (horses only) unilateral sweating
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What is the corpora nigra?
aka granula iridica; in herbivores, these are the extension of the posterior epithelium into the pupil and appear as pigmented, irregular masses; normal finding
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Where does outflow of aqueous humor occur?
iridocorneal angle
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Describe the outflow of aqueous humor.
ciliary epithelium--> between the iris and the lens--> pupil--> anterior chamber--> iridocorneal angle--> trabecular meshwork--. scleral venous plexus
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What are the 2 components of the ciliary body?
pars plicata (superior/ dorsal), pars plana (inferior/ ventral)
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The ciliary body is located...
posterior to the iris
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The ciliary body is under ____________ control; inflammation results in __________.
parasympathetic; contraction
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What are the functions of the ciliary body? (3)
- it gives rise to ciliary processes, which produce aqueous humor
- blood-aqueous barrier
- accommodation
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The vascular core of the ciliary body is covered by __________, which is one site of the ____________; when this is disrupted, ___________ results clinically.
2 layers of epithelium; blood-aqueous barrier; aqueous flare
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The ciliary body gives rise to the ____________, which...
lenticular zonules; attach to the lens, so when the ciliary body contracts, tension on the zonules is relaxed, allowing the lens to thicken [accommodation]
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Aqueous humor production by the ciliary processes is by a combination of....
- passive filtration
- diffusion
- active secretion- under the control of carbonic anhydrase
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When there is loss of zonular support, it leads to...
lens luxation.
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The choroid is located...
in the posterior portion of the uvea, from the ciliary body to the optic nerve.
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What is the function of the choroid? (2)
- provides nutrition for the outer portions of the retina (rods and cones) in dogs, cats, and cows; provides nutrition to the entire retina in horses
- cools the highly metabolically active retina
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What is the tapetum lucidum?
- shiny part of the choroid (in the vascular tunic) that reflects and amplifies light, allowing animals to see in the dark
- cellular in carnivores and fibrous in herbivores
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What is a pathognomonic sign of retinal thinning?
tapetal hyperreflection- tapetum appears much brighter than normal
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The tapetum is not __________.
pigmented
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All red eyes, painful eyes, blind eyes, eyes with anisocoria, and eyes with anterior uveitis should have...
- intraocular pressures taken
- Normal 10-20mmHg
- Glaucoma > 30mmHg
- Anterior Uveitis <7-10mmHg
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What are persistent pupillary membranes? (5 principals)
- congenital hereditary (autosomal recessive in basenjis)
- remnants of fetal iridal vascular arcades, which originate from the collarette zone of the iris
- fail to regress
- attach to corneal, iris, or lens
- must r/o synechiae
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What is the treatment of persistent pupillary membranes?
none
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What is heterochromia?
- part or all of the iris stroma lacks pigment, resulting in a variation of color within or between the irises
- associated with dilute coat color (blue merle, siamese, harlequin)
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What is the clinical significance of heterochromia?
alone it has no significance, but it can be associated with other ocular or systemic abnormalities (deafness, blindness)
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What is coloboma?
- a notch defect in the iris, usually in the inferonasal portion of iris
- must differentiate from iris atrophy
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Iris cysts are _________ lesions that can occur in... (3)
acquired; dogs, cats, horses
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What is an iris cyst?
cystic accumulation of aqueous humor within a layer of the posterior iris or ciliary body epithelium; can be attached or break free and float around
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How can you differentiate an iris cyst from a ocular mass on exam?
a cyst allows light to pass through it (transilluminates), while a melanoma mass will not
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What is the treatment of iris cysts? (3 options)
none (benign neglect), laser ablation, irrigation/ aspiration
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What is the clinical significance of iris cysts in cats?
they cause increased intraocular pressure
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Primary iris atrophy is most often seen in __________, and it must be differentiated from ___________ clinically.
small breed old dogs; coloboma
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Iris atrophy can be secondary to __(2)__.
uveitis or glaucoma
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Iris atrophy leads too...
decreased PLR; differentiate it from neurologic causes of decreased PLR
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How is iris atrophy treated?
it's not
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What are clinical signs of anterior uveitis? (8)
- miosis
- aqueous flare (continuous beam of light from the cornea to the lens)
- redness
- photophobia
- pain - epiphora, blepharospasm, rubbing eyes
- keratic precipitates- accumulations of protein and mononuclear cells, usually indicate granulomatous anterior uveitis
- hypotony- decreased intra-ocular pressure
- diffuse corneal edema
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What are etiologies of anterior uveitis? (9)
- Ocular: corneal ulceration, lens induced (hypermature cataract), ocular trauma, primary ocular neoplasia
- Systemic: bacteremia, viremia, septicemia, autoimmune, secondary to metastatic neoplasia
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When trying to determine the cause of anterior uveitis,...
rule out ocular causes first (only 4 ocular causes of anterior uveitis)
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What are primary ocular neoplasias? (3)
- melanoma
- adenoma/ adenocarcinoma originating from the ciliary body
- spindle cell sarcoma (cats only)
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What are commonly neoplasias that secondarily go to the eye? (5)
- lymphosarcoma
- metastatic carcinoma
- undifferentiated sarcoma (histiocytic sarcoma), hemangiosarcoma, osteosarcoma, etc
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In dogs, the majority of systemically caused anterior uveitis is ____________; other causes include.. (2)
idiopathic/ immune-mediated; neoplasia, systemic infectious disease
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What is Uveo-dermatologic syndrome, and what are its components?
auto-immue disorder directed against melanin [dogs]; poliosis, vitiligo, uveitis
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What systemic infectious diseases can cause uveitis in dogs? (8)
Ehrlichia canis, Blastomycosis dermatitidis, Crypto, Histoplasmosis, Rocky Mountain Spotted Fever, Dirofilaria immitis, Lyme Disease, Leishmaniasis
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The majority of anterior uveitis in cats is caused by __________; other causes include...
idiopathic/ immune- mediated; systemic infectious disease, neoplasia (least)
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What infectious diseases cause uveitis in cats? (6)
FeLV, FIP, Toxoplasma, FIV, Cryptosporidium, Bartonella
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Describe the "specific treatment" for anterior uveitis.
- directed towards the inciting cause
- requires correct identification of etiologic agent
- antimicrobials, immunotherapies, chemotherapy, etc
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What are the non-specific treatments for anterior uveitis? (3)
- Topical atropine (parasympatholytic): reduce pain by dilating pupil
- topical corticosteroids or NSAIDs (not with an ulcer!): reduce discomfort and inflammatory mediators
- systemic NSAIDS: only with involvement of posterior uvea, if there's an ulcer, or if no response to topical
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What are sequelae of anterior uveitis? (6)
anterior +/- posterior synechia, cataracts, glaucoma, blindness, phthisis bulbi (shrunken, non-functional eye), lens luxation
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What is the etiology of equine recurrent uveitis? (1 main, 6 underlying)
- IMMUNE-MEDIATED
- [all postulated, not proven] Leptospira, Onchocerca, viral infection hypersensitivity, Toxoplasmosis, Brucellosis, Streptococcal
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What are clinical signs of equine recurrent uveitis? (6)
- same as uveitis+
- chorioretinitis (butterfly lesions around optic nerve)
- synechia
- atrophy of corpora nigra
- cataract
- chorioretinal scars
- blindness
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What is the treatment for equine recurrent uveitis? (3)
- Active phase: atropine, prednisolone acetate topical drops, systemic banamine
- Inactive disease: cannot reverse effects
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The choroid has extremely __________; therefore...
high blood flow; it is predisposed to blood borne diseases and posterior uveitis (bacteremia, septicemia, mycotic infections, disseminated neoplasia)
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The __________ is one of the few places in the body where you can directly view blood vessels; therefore,...
choroid; the eye is an excellent location to look for vasculitis and bleeding disorders.
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The posterior uvea is predisposed to what auto-immune diseases? (2)
- SLE
- uveo-dermatologic syndrome
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Signs of chorioretinitis. (8)
- thinning of retina (tapetal hyperreflection)
- fundic depigmentation
- hemorrhage
- vasculitis
- edema
- transudate
- exudate (granulomatous, non-granulomatous)
- +/- retinal detachment
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What is the treatment for posterior uveitis? (2)
- SYSTEMIC MEDICATION
- if infectious, carprofen (SA) or banamine (Eq)
- corticosteroids if etiology does not contraindicate it
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What is hyphema?
blood in the anterior chamber of the eye
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What are differentials for hyphema? (7)
- coagulopathy/ vascular disorder
- trauma
- intraocular neoplasia
- hypertension
- sequelae of anterior uveitis
- retinal detachment
- seen with other ocular anomalies (Collie eye)
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All eyes with hyphema should have __________ performed.
intra-ocular pressures
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What is the treatment for hyphema?
treat underlying cause
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Prognosis is better with __________ than __________ trauma.
sharp; blunt
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Iris prolapse is always associated with ___________; principals of treatment include...
- anterior uveitis
- avoid topical ointments until the fibrous tunic is repaired (will cause granulomatous inflammation in the eye), atropine, antiinflammatories, surgical repair
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Intraocular neoplasia can result in... (6)
- intraocular hemorrhage
- uveitis
- lens displacement
- cataracts
- glaucoma
- retinal detachment
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What are differences in ocular melanoma between dogs and cats?
- Dogs- usually benign, enucleate only if mass interferes with normal ocular function, young retrievers are predisposed (hereditary)
- Cats- usually metastasizes, all tumors should be enucleated
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What are characteristics of adenoma/ adenocarcinoma of the ciliary body?
- may be benign or malignant
- enucleate if mass interferes with normal ocular function
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What are the tunics of the eye and the components of each?
- Fibrous tunic: cornea and sclera
- Vascular tunic: uvea (iris, ciliary body, choroid)
- Nervous tunic: retina
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Define the fundus.
Everything behind the iris: retina and choroid
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What is synechia?
adhesion of the iris to the cornea (anterior synechia) or to the lens (posterior synechia)
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