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The uvea is aka the __________.
What are the 3 regions of the uvea?
iris, ciliary body, choroid
What is the anterior most portion of the uvea?
What are the functions of the iris? (2)
- regulates the amount of light entering the posterior portions of the eye
- blood aqueous barrier
Anterior SEGMENT versus posterior SEGMENT
- anterior segment= everything in front of the lens
- posterior segment= behind the lens (vitreous, choroid, retina)
anterior CHAMBER versus posterios CHAMBER
- anterior chamber= in front of the iris
- posterior chamber= behind the iris
- [both are within the anterior segment]
What are the muscles of the iris? (2)
- sphincter muscle (smooth muscle under involuntary parasympathetic control)
- dilator muscle (smooth muscle under involuntary sympathetic control)
Describe the innervation to the sphincter muscle of the iris.
parasympathetic control from CN III
The iris sphincter muscle can be blocked (causing mydriasis) with ____________, such as... (2)
parasympatholytic agents; topical Tropicamide or atropine
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
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
Where does outflow of aqueous humor occur?
Describe the outflow of aqueous humor.
ciliary epithelium--> between the iris and the lens--> pupil--> anterior chamber--> iridocorneal angle--> trabecular meshwork--. scleral venous plexus
What are the 2 components of the ciliary body?
pars plicata (superior/ dorsal), pars plana (inferior/ ventral)
The ciliary body is located...
posterior to the iris
The ciliary body is under ____________ control; inflammation results in __________.
What are the functions of the ciliary body? (3)
- it gives rise to ciliary processes, which produce aqueous humorblood-aqueous barrier
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
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]
Aqueous humor production by the ciliary processes is by a combination of....
- passive filtration
- active secretion- under the control of carbonic anhydrase
When there is loss of zonular support, it leads to...
The choroid is located...
in the posterior portion of the uvea, from the ciliary body to the optic nerve.
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
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
What is a pathognomonic sign of retinal thinning?
tapetal hyperreflection- tapetum appears much brighter than normal
The tapetum is not __________.
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
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
What is the treatment of persistent pupillary membranes?
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)
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)
What is coloboma?
- a notch defect in the iris, usually in the inferonasal portion of iris
- must differentiate from iris atrophy
Iris cysts are _________ lesions that can occur in... (3)
acquired; dogs, cats, horses
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
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
What is the treatment of iris cysts? (3 options)
none (benign neglect), laser ablation, irrigation/ aspiration
What is the clinical significance of iris cysts in cats?
they cause increased intraocular pressure
Primary iris atrophy is most often seen in __________, and it must be differentiated from ___________ clinically.
small breed old dogs; coloboma
Iris atrophy can be secondary to __(2)__.
uveitis or glaucoma
Iris atrophy leads too...
decreased PLR; differentiate it from neurologic causes of decreased PLR
How is iris atrophy treated?
What are clinical signs of anterior uveitis? (8)
- aqueous flare (continuous beam of light from the cornea to the lens)
- 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
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
When trying to determine the cause of anterior uveitis,...
rule out ocular causes first (only 4 ocular causes of anterior uveitis)
What are primary ocular neoplasias? (3)
- adenoma/ adenocarcinoma originating from the ciliary body
- spindle cell sarcoma (cats only)
What are commonly neoplasias that secondarily go to the eye? (5)
- metastatic carcinoma
- undifferentiated sarcoma (histiocytic sarcoma), hemangiosarcoma, osteosarcoma, etc
In dogs, the majority of systemically caused anterior uveitis is ____________; other causes include.. (2)
idiopathic/ immune-mediated; neoplasia, systemic infectious disease
What is Uveo-dermatologic syndrome, and what are its components?
auto-immue disorder directed against melanin [dogs]; poliosis, vitiligo, uveitis
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
The majority of anterior uveitis in cats is caused by __________; other causes include...
idiopathic/ immune- mediated; systemic infectious disease, neoplasia (least)
What infectious diseases cause uveitis in cats? (6)
FeLV, FIP, Toxoplasma, FIV, Cryptosporidium, Bartonella
Describe the "specific treatment" for anterior uveitis.
- directed towards the inciting cause
- requires correct identification of etiologic agent
- antimicrobials, immunotherapies, chemotherapy, etc
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
What are sequelae of anterior uveitis? (6)
anterior +/- posterior synechia, cataracts, glaucoma, blindness, phthisis bulbi (shrunken, non-functional eye), lens luxation
What is the etiology of equine recurrent uveitis? (1 main, 6 underlying)
- [all postulated, not proven] Leptospira, Onchocerca, viral infection hypersensitivity, Toxoplasmosis, Brucellosis, Streptococcal
What are clinical signs of equine recurrent uveitis? (6)
- same as uveitis+
- chorioretinitis (butterfly lesions around optic nerve)
- atrophy of corpora nigra
- chorioretinal scars
What is the treatment for equine recurrent uveitis? (3)
- Active phase: atropine, prednisolone acetate topical drops, systemic banamine
- Inactive disease: cannot reverse effects
The choroid has extremely __________; therefore...
high blood flow; it is predisposed to blood borne diseases and posterior uveitis (bacteremia, septicemia, mycotic infections, disseminated neoplasia)
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.
The posterior uvea is predisposed to what auto-immune diseases? (2)
- uveo-dermatologic syndrome
Signs of chorioretinitis. (8)
- thinning of retina (tapetal hyperreflection)
- fundic depigmentation
- exudate (granulomatous, non-granulomatous)
- +/- retinal detachment
What is the treatment for posterior uveitis? (2)
- SYSTEMIC MEDICATION
- if infectious, carprofen (SA) or banamine (Eq)
- corticosteroids if etiology does not contraindicate it
What is hyphema?
blood in the anterior chamber of the eye
What are differentials for hyphema? (7)
- coagulopathy/ vascular disorder
- intraocular neoplasia
- sequelae of anterior uveitis
- retinal detachment
- seen with other ocular anomalies (Collie eye)
All eyes with hyphema should have __________ performed.
What is the treatment for hyphema?
treat underlying cause
Prognosis is better with __________ than __________ trauma.
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
Intraocular neoplasia can result in... (6)
- intraocular hemorrhage
- lens displacement
- retinal detachment
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
What are characteristics of adenoma/ adenocarcinoma of the ciliary body?
- may be benign or malignant
- enucleate if mass interferes with normal ocular function
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
Define the fundus.
Everything behind the iris: retina and choroid
What is synechia?
adhesion of the iris to the cornea (anterior synechia) or to the lens (posterior synechia)