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Ch. 20 Uvea

Terms in this set (149)

True/False: Normal anterior uveal development during embryogenesis occurs by invagination of the optic cup resulting in a single layered medullary epithelium.
False: Normal anterior uveal development during embryogenesis occurs by invagination of the optic cup resulting in a bilayered medullary epithelium.
The innermost layer of the optic cup forms what 3 structures?
The outermost layer of the optic cup forms what 3 structures?
Inner: neurosensory retina, nonpigmented CB epithelium, innermost (more vitreal, aka posterior) layer of the iris epithelium
Outer: RPE, pigmented CB epithelium, outermost (away from vitreous, aka anterior) layer of iris epithelium (with dilator & sphincter muscle)
In subalbinotic eyes, which part of the iris still has pigment?
neuroectodermal layer of iris (posterior epithelium)
True/False: Complete albinism is commonly seen in arctic and dilute merle breeds.
False. Complete albinism results in a translucent iris with visible iris vessels. Subalbinism refers to dilution of ocular pigmentation. In contrast to complete albinism, in which the eye lacks all pigment, subalbinism is seen as a blue iris with a red fundus reflex.
List the common anterior segment changes associated with Merling.
heterochromia irides, iris hypoplasia, a black-rimmed pupil from prominent iridal pigmented epithelium, and an eccentric pupil (i.e., corectopia). Both typical and atypical iris colobomata and PPMs are also common findings in merle dogs
How are the coat Merling and Merle ocular lesions inherited in Australian Shepherds?
Coat Merling is dominant.
Ocular lesions are recessive.
When does the fetal pupillary membrane start to regress?
Pupillary membrane is a primitive mesodermal tissue. Normally, the central vascular arcades regress first, beginning during the sixth week of canine development. Peripheral arcade regresses later until 6 weeks post natal (embryology chapter says day 45 to 2 weeks post-natal)
Define a dysplastic pupillary membrane.
iridocorneal or iridolenticular adhesions and can result in significant ocular opacification
Familial PPMs have been described in what breeds? 4
Pembroke Welsh Corgi, Basenji, Chow Chow, and Mastiff breeds
Match Peters anomaly classification with description: Peters anomaly type 1, Peters anomaly type II, Peters plus syndrome
a) central corneal opacity with cataracts or corneo-lenticular adhesions
b) central corneal opacity with iridocorneal adhesions
c) systemic malformations and ocular malformations
Peters anomaly type 1 - central corneal opacity
with iridocorneal adhesions;
Peters anomaly type II - central corneal opacity with cataracts or corneo-lenticular adhesions; and
Peters plus syndrome - Peters anomaly with systemic malformations.
What is the name of a coloboma at the pupillary margin?
notch coloboma
What is the name of a coloboma at the base of the iris?
iridodiastasis
What is the name of a coloboma within the iris body?
pseudopolycoria
What is the location/description of a typical coloboma?
Colobomata in the ventral aspect of the iris occur secondary to failure of closure of the optic fissure. Colobomata in other locations are referred to as atypical colobomata and may be caused by primary abnormalities in the outer layer of the optic cup
What is the difference between dyscoria and corectopia? Microcoria?
Dyscoria is an abnormally shaped pupil, and corectopia is a pupil in an anomalous position. Microcoria is a congenital miosis resulting from absence of the dilator muscle.
What iris abnormality is seen with hereditary tapetal degeneration in Beagles?
Abnormal lightly pigmented irides
What is the suspected reason for iris cyst formation?
failure of fusion of the two layers of the primary optic vesicle because most cysts in dogs form between the two layers of pigmented iris epithelium (embryology chapter says optic cup)
Failure of the two embryonal neuroectodermal layers to fuse allows fluid to accumulate between these otherwise contiguous epithelial layers
Cysts located at the pupillary margin are associated with a persistent or excessive development of the marginal sinus
What embryological layers are involved in anterior segment dysgenesis?
Malformation of mesodermal, surface ectodermal, and neuroectodermal tissues is involved.
A primary defect in formation of the neuroectodermal optic cup is suspected as the cause
What components characterize Anterior segment dysgenesis?
thinned corneal epithelium and stroma, absent Descemet's membrane and endothelium, undifferentiated anterior uveal tissue with lack of iridocorneal angle differentiation, and unencapsulated globules of lens material.
What color change can be seen with senile iris atrophy?
Foci of hyperpigmentation may be noted as stroma is lost and pigmented epithelium is exposed
Uveal cysts are from what embryological origin?
neuroectoderm
Uveal cysts are most common in what 3 breeds?
Goldens, Labs, Bostons
What breeds have been associated with glaucoma and uveal cyst formation?
Golden Retriever and Great Dane
Define the following: endophthalmitis, panophthalmitis.
Endophthalmitis: inflammation involving the ocular cavities and adjacent structures.
Panophthalmitis is inflammation involving all tunics of the eye
What are the 3 barriers to the blood-aqueous barrier?
Tight junctions between nonpigmented ciliary body epithelial cells, tight junctions and gap junctions in the vascular endothelium, nonfenestrated impermeable capillaries of the iris
Put in order of most stable to least stable blood-aqueous barrier: dogs, primates, rabbits.
Primates > dogs > rabbits (very labile)
What are the 5 signs of the acute phase of inflammation?
Redness, heat, increased mass, pain, loss of function
Name 7 chemical mediators that increase vascular permeability.
Histamine, serotonin, kinins, plasmin, complement, prostaglandins, and peptide growth factor
What is the normal aqueous protein content vs with uveitis? What about flaremetry?
Normal = 21-37 mg/dL
Uveitis = 1200-6000 mg/dL
Flare in normal 1.4-7.0 PC/msec and in uveitis as high as 246
Name the 4 types of exudate.
Serous, fibrinous, sanguinous, purulent
What is granulation composed of? What stage of inflammation does it occur in?
leukocytes, fibroblasts, proliferating vessels
Subacute inflammation
Which has higher aqueous protein content: acute or chronic uveitis?
acute
Where in the eyes are prostaglandins produced?
a) Lens
b) Retina
c) Iris
d) choroid
c) Iris
What prostaglandin is a potent constrictor of the iris sphincter muscle?
a) PGE1
b) PGF2
c) PGE2
d) PGA
b) PGF2
Where is prostaglandin inactivated?
Outside the eye
Limited PG 15-dehydrogenase in the eye.
What 3 pathways can arachidonic acid enter?
Oxidation, lipoxygenase, cyclooxygenase
Where are leukotrienes synthesized in the eye (4)?
cornea, conjunctiva, anterior uvea, lens
T/F: Prostaglandins have greater chemotactic, humor, and cellular activities than leukotrienes.
False - flip leukotrienes and prostaglandin
Why is inhibiting leukotrienes a good and bad idea?
Leukotrienes may be early mechanism for cell migration into inflamed uvea b/c of good chemoattractant abilities. Bad b/c could shunt arachidonic metabolites to COX pathway
What chemical mediator is important in uveitis, more specifically the axonal reflex?
a) Thromboxane
b) Prostacyclin
c) Histamine
d) Substance P
d) Substance P
With paracentesis, does PG or substance P play a bigger role in initiation of inflammatory process?
PG (b/c if use proparacaine to block neuronal reflex, still get inflammation)
What term describes hyperemia of the deep, perilimbal or circumcorneal anterior vessels and is common with deep intraocular inflammation?
Ciliary flush
T/F: miosis in anterior uveitis occurs in response to PGF2 acting directly on the iris dilator muscle.
False; iris sphincter
Aqueous flare is visualized when light scattering from particles suspended in the anterior chamber causes a continuous light reflection. This is also called the ______ phenomenon or effect.
Tyndall effect/phenomenon
At what grade of aqueous flare are iris and lens details hazy?
Grade 3
1+: faint flare (barely detectable)
2+: moderate flare (iris and lens details clear)
3+: marked flare (iris and lens details hazy)
4+: intense flare (fixed, coagulated aqueous humor with fibrin)
Convection currents in the anterior chamber rise along the warm _______ and fall along the cooler ________ that creates the characteristic formation pattern of keratic precipitates. What is that pattern?
Warm iris, cooler cornea. Ventrally in triangle shape
What type of inflammation tends to cause mutton-fat KPs?
granulomatous (deposits are plasma cells and macrophages)
What is eight ball hyphema?
complete hyphema of 5-7 day duration when blood turns from bright red to bluish black
PIFMs will stain positive for which stain on IHC?
a) VEGF
b) COX2
c) Laminin
d) Vimentin
e) SMA
f) All of the above
f) All of the above
How does uveitis cause decreased IOP?
Decreased AH production with breakdown of BAB.
Increased uveoscleral flow
Match the pathway with products: Oxidation, Cyclooxygenase, Lipoxygenase
a) Fatty acid
b) Thromboxane
c) Leukotrienes
d) Hydroperoxyl
e) Prostaglandins
f) Prostacyclin
g) Hydroxyeicosa-tetraenoic acid
Oxidation - fatty acid
Cyclooxygenase - prostaglandins, thromboxane, prostacyclin
Lipoxygenase - leukotrienes, hydroperoxyl, hydroxyeicosa-tetraenoic acid
How do corticosteroids work against inflammation?
inhibit phosopholipase and release of arachidonic acid
In a paracentesis model, what NSAID was equally as effective as pred acetate?
flurbiprofen
What systemic antibiotic penetrates the normal blood-aqueous barrier more effectively than others?
chloramphenicol
How does atropine stabilize the BAB?
blocking effect of acetylcholine which dilates blood vessels
What kind of association is there b/w cataract and antigens crystalline serum antibodies?
Negative association b/w presence and maturity of cataract and the crystallin antibodies
What type of inflammation is described with phacolytic LIU? Vs phacoclastic LIU?
Phacolytic: Lymphocytic and plasmacytic uveitis. Old dogs (esp mini Schnauzers) with rapidly progressing cataracts can get a phacolytic granulomatous LIU.
Phacoclastic: Lymphocytic-plasmacytic anterior uveitis, perilenticular inflammation that varies from suppurative to lymphocytic, intralenticular neutrophils and perilenticular fibroplasia
What is the avg numbers of days from lens rupture to referral in cases amenable to surgery with lensectomy? Vs not candidates for surgery.
3 days (not candidates at 10 days)
Name potential causes (diseases) for anterior uveitis secondary to corneal and scleral disease
corneal ulceration; necrotizing scleritis
What is the most common clinical sign of anterior uveitis associated with corneal ulceration?
miosis
Name 5 clinical signs of uveodermatologic syndrome.
anterior uveitis or panuveitis, iris or choroidal depigmentation, bullous retinal detachment, poliosis (hair loses pigment) and vitiligo (skin loses pigment)
Which antigen has been found in Akitas to be associated with higher relative risk for UDS? What was the mean age? Name three other breeds that seem more prevalent for this disease?
DQA1*00201; 3 years; Akita, Siberian Husky, Samoyed and Shetland Sheepdog
Why do canine patients not develop neurologic signs in UDS? What reported neurologic signs are seen in humans with this disease?
Lack of melanin in canine meninges; Dysacusis (hearing impairment) and meningitis
What are histopath changes noted in UDS on eye vs skin? Which type of cells are present
Eye: Granulomatous pauveitis with prominent perivascular lymphoid aggregates and melanophages; mostly B-cell and macrophages (Th2 immunity);
Skin: interface dermatitis with primarily lichenoid pattern. Large histiocytic cells, plasma cells, melanophages and small mononuclear cells; mostly lymphocyte by T cells and macrophages (Th1 immunity)
What is the most common type of inflammation with mycoses? Which stain is mostly used to find the organisms?
Granulomatous or pyogranulomatous; Gomori's methenamine-silver or periodic acid-schiff
Where is blastomycosis endemic? Which type of dogs are more commonly affected?
Mississippi, missouri, ohio river valley, mid-atlantic states, quebec, manitoba, ontario;
Young, male of large breed
Where is the infection with blastomycosis centered in the eye?
choriocapillaris of nontapetal choroid with relative sparing of tapetal choroid
Is it better to test for the antigen or antibody for blastomycosis?
antigen (93% sensitivity in urine).
A positive response to therapy for blastomycosis is best in with...
a) anterior uveitis
b) posterior uveitis
c) endophthalmitis
Best with posterior uveitis (76% response).
Response is only 18% with ant uveitis and 13% with endophthalmitis
Where is coccidioidomycosis endemic? Which two breeds may have predilection?
SW USA, Mexico, areas of central and south america; potentially more common in Boxer and Doberman
What % of dogs with coccidioidomycosis had ocular signs alone?
43%
What are potential systemic disease with cryptococcosis?
meningoencephalitis; Respiratory; Cutaneous; Fever; Lymphadenomegaly; Lameness due to lytic bone lesions
Where is histoplasmosis found? What other infection has cross-reactivity with the urine antigen?
In soil of temperate and subtropical regions. Ohio, Missouri, Mississippi River, but identified in most states
-- Blastomycosis
What is the main route of infection, typical inflammation, and typical stain for fungal diseases?
inhalation
granulomatous or pyogranulomatous
Gomori's methenamine silver, PAS, mucicarmine
Which ocular nematodiasis can be found causing uveitis?
Ocular filariasis: Dirofilaria immitis, angiostrongylus vasorum
Ocular larval migrans: toxocara canis, Onchocercia lineales or O. lupi
What part of the eye do toxocara Canis and Onchocercia like to go to?
Toxocara: retina and vitreous
Onchocerca: masses in conj, nictitans, and sclera
Name potential causes of ophthalmomyiasis
Diptera, oestrus ovis (sheep nasal botfly), hypoderma bovis (cattle warble)
Where is leishmania endemic? What is its intermediate host? Reservoir host?
Mediterranean shore and parts of Africa, India and S America;
Intermediate host: Sandfly (phlebotomus)
Reservoir: domestic and wild canids
What ocular signs can leishmaniasis cause? (5)
blepharitis, keratoconjunctivitis, uveitis, retinitis, endophthalmitis
Which species is the definitive host of toxoplasma gondii?
Cat
What are 3 protozoal diseases that can cause uveitis?
toxoplasma gondii, Neosopora canine, Trypanosoma evansi
How is ehrlichia transmitted?
obligate intracellular parasite transmitted by brown dog tick (rhipichephalus sanguineus)
When do ocular signs of ehrlichia occur?
3 weeks after onset of fever.
What are the 2 most common reported ocular signs of Ehrlichiosis?
Anterior uveitis and exudative retinal detachment
What may be seen on a blood smear with Ehrlichiosis?
Multiple intracytoplasmic subunits of E. canis (i.e., morulae) may be seen within monocytes
What is the primary lesion of Rocky Mountain Spotted Fever?
Vasculitis is the primary lesion caused initially by direct infection of the vascular endothelium and perithelial smooth muscle, and later by immunologic phenomena
What causes RMSF?
Rickettsia rickettsii
What disease causes keratouveitis with corneal edema and why?
Canine Adenovirus-1 (Infectious Canine Hepatitis) - immune-complex deposition / Arthus-type reaction (type 3 hypersensitivity)
What percent of dogs with natural infection with CAV get keratouveitis? What about the vaccine?
20% with natural infection, 0.4% with CAV-1 vax (rare reports with CAV-2 vax)
What breed has a higher susceptibility to reaction after the CAV vaccine?
Afghan hound
What treatment MAY worsen the ocular lesions of CAV post-vaccine reaction?
Corticosteroid therapy is implicated in prolongation of corneal lesions and even blindness in dogs suffering postvaccinal reactions (1965 study). However, anti-inflammatory therapy of postvaccinal keratouveitis may be necessary to prevent severe sequelae and to hasten resolution of ocular disease
Ocular signs occur in ___% of Brucella canis cases and what are the 4 most common ocular signs?
14%, endophthalmitis, chronic uveitis, hyphema, chorioretinitis
Which Bartonella species/subspecies can cause occur signs?
Bartonella vinsonii subspecies berkhoffi
Which of these infectious agents can live inside cells?
a) Ehrlichia canis
b) Rickettsia rickettsii
c) Canine adenovirus
d) Brucella canis
e) Bartonella
f) Leptospira spp.
g) Toxoplasma gondii
A (E. canis is obligate intracellular in monocytes),
c (CAV-1 virus replicates in reticuloendothelial, hepatic parenchymal, and vascular endothelial cells),
d (Brucella can survive in mononuclear cells),
e (Bartonella is intraerythrocytic)
g (Toxoplasma is obligate intracellular parasite)
What is the main clinical sign with Prototheca and what are 2 species that are known pathogens in dogs?
Hemorrhagic diarrhea, P. zopfii and P. wickerhamii
What size particles does the iridial vascular endothelium and nonpigmented ciliary body epithelium normally prevent from entering the aqueous? What size are lipoproteins?
40 Å, lipoproteins are 50 to 250Å - so uveitis must be involved with lipoid aqueous (or lipid causes the inflammation)
Other than lipoid aqueous, what are two other ocular signs you can see with hypercholesterolemia or hypertriglyceridemia?
Lipemia retinalis and corneal lipidosis (acrus lipoides corneae)
Pigmentary uveitis or Pigmentary and Cystic Glaucoma are seen in what 2 breeds?
Golden Retrievers (in the US) and Great Dane
While uveitis is seen clinical in pigmentary uveitis, what percentage of cases have uveitis on histopath?
About half with very mild uveitis
What is the most frequently observed early clinical sign of Pigmentary uveitis?
Radial pigment on anterior lens capsule
Are the cysts in Pigmentary uveitis usually thick- or thin-walled?
Thin-walled
How is pigmentary uveitis different between the breeds?
Great Danes have the cysts and glaucoma but don't necessarily have the radial lens pigment like Goldens
Solid intraocular xanthogranulomas were found in what breed with what 3 conditions? What was the main cell type found on histopath?
Miniature Schnauzers (3) that all had diabetes mellitus, hyperlipidemia, LIU with secondary glaucoma
Foamy macrophages
What are 2 causes of Hyperviscosity syndrome and where are the most prominent ocular lesions?
Monoclonal gammopathy (IgG, IgA, IgM), polycythemia vera
Posterior segment - retinal vascular dilatation, tortuosity, microaneurysms, retinal hemorrhage, retinal detachment, chorioretinitis, and papilledema
What are 3 ocular lesions that can be seen with sulfonamide hypersensitivity?
Retinitis, KCS, uveitis (alone or secondary to thrombocytopenia)
What treatment is recommended for phacoclastic uveitis?
Topical and immunosuppressive doses of prednisone and topical atropine
In humans, where do most FBs enter the eye and where are most FBs found?
Corneal entrance but found in the vitreous
What 3 inorganic FBs are nonreactive and what 2 are reactive and likely to cause direct toxicity?
Lead, glass, and plastic are nonreactive.
Iron and copper are reactive.
When plain films are the only diagnostic available to look for an intraocular FB, what can you use to help localize?
Put a metal ring (Flieringa ring) under the eyelids so you can identify the anterior aspect of the globe
T/F: Every effort should be made to remove organic FBs from the globe.
True - organic FBs stimulate a severe often unresponsive endophthalmitis
Where should a FB that is completely in the anterior chamber be removed?
Removed from a site distant from the entrance wound to minimize scarring and damage to endothelial cells. Entrance wound should be closed with reestablishment of IOP prior to creating a new surgical wound through which to remove the FB
Nelms 1993 found that what was the most common cause for hyphema at referral institutions?
Retinal detachment
What are 4 differentials for hyphema in a young dog without a history of trauma?
Collie Eye Anomaly, Persistent Hyaloid Artery, Ehrlichiosis, toxic bleeding disorders
What treatment is suggested for hyphema?
Topical dex or pred acetate +/- systemic pred to reduce and control intraocular inflammation and to reduce the incidence of rebleeding. Mydriatic or miotics are somewhat controversial
TPA is most effective within ____ of clot formation. What is the recommended dose?
With 72 hours of clot formation.
0.1 ml of 25 mg/100ul solution (i.e., you are injecting 25 mg of TPA)
Uncomplicated hyphema usually resolved in what time period?
Within 1 week
What type of glaucoma can occur secondary to hyphema in humans and dogs?
Ghost cell glaucoma
Which breeds have been shown to have abnormal ocular pigment deposition and glaucoma?
Cairn terrier, boxer, labrador retriever; older dogs, called ocular melanosis, hyperpigmentation of iris, CB, choroid,
Are the cells involved in ocular melanosis mostly melanocytes or melanophages?
Melanocytes
*What is the suggested mode of inheritance for ocular melanosis in Cairn Terriers?
Autosomal dominant
T/F: The majority of primary uveal tumors do not metastasize to distant sites
True
What is the most common intraocular neoplasm in the dog?
Melanoma
Where do the majority of canine uveal melanomas arise in the dog?
Anterior uvea (iris and CB both common sites for origin)
What is the mean age of onset of uveal melanomas in the dog?
Older (9 years)
Large studies of populations affected by uveal melanoma list what two breeds as the most commonly affected?
German shepherd and retrievers
What diagnostic can help potentially differentiate limbal melanocytoma from uveal melanoma that has protruded through the limbus?
Gonioscopy; uveal melanoma with extraocular extension usually invades the filtration angle, limbal melanocytoma invades into deep sclera and may compress the angle but less commonly invades it; exceptions to the rule exist!
Where should you check for melanoma that can met to the eye? Where to check for mets of melanoma from the eye?
To the eye: oral cavity, nail beds, foot pads
From the eye: thoracic and abdominal viscera
What stain can be used to help diagnose a poorly pigmented or differentiated melanoma?
Melan A; can also use antibody markers in rare instances
T/F: the Callender classification system used for human ocular melanomas is appropriate to also use for canine melanomas
False; many canine tumors are benign, mixed or epithelioid cell type, plump cells not seen in uveal melanoma in people so not appropriate
According to Giuliano et al 1999, what percentage of uveal melanomas histopathologically remained inside the sclera, invaded the sclera, or had extra scleral extension?
inside the sclera 7%,
invaded the sclera 56%
extra scleral extension 28%
Heavily pigmented uveal tumors tend to be benign or malignant melanomas? What % of intraocular melanocytic tumors is considered malignant?
Benign; malignant are less heavily pigmented and comprise 20% of intraocular melanocytic tumors
What criterion is considered superior for determining malignancy of uveal melanocytic tumors?
Mitotic index; <2/10 HPF is typical of melanocytomas, >4/10 HPF and usually higher in malignant tumors; COX-2 expression not representative as expressed equally in malignant and benign
How is sphincterotomy performed and what would indicate it?
Incise 1-3 mm of pupil margin, usually at 2-4 positions in quadrants with iris scissors; used when inadequate mydriasis in cataract surgery
What is the indication for iridotomy?
Pupillary block due to annular posterior synechia; forms holes in iris peripheral to synechiae so AH can bypass normal route through pupil and go directly from posterior to anterior chamber
What is the reported metastasis rate for uveal melanomas in dogs?
4% and 10% according to 2 studies from the 80s (4% from melanocytomas and 25% from malignant melanomas)
What is the second most common primary intraocular tumor in the dog?
Iridociliary epithelial tumors; most common in middle age to older dogs
List the identifying criteria of a primary iridociliary epithelial tumor.
Have one of the following: noninvasive epithelial growth extending into AC adjacent to iris or CB, pigmented epithelial cells, or thick basement membrane structures on cell surface
What proportion of iridociliary epithelial tumors are malignant?
50%; distant metastasis is rare, adenocarcinomas can extend through iris base or pupil and may met; adenomas more commonly limited to CB
What are the histopathological characteristics of adenoma/carcinomas?
Adenoma: sheets and cords of well differentiated epithelial cells with tendency to form adenoidal structures with eosinophilic secretory substance; Carcinoma: fewer adenoidal structures, less secretory substance, and variable cellular pleomorphism and numbers of mitotic figures
What stains can be used to diagnose adenoma/adenocarcinoma?
Most positive for vimentin, S100, and neuron-specific enolase; alcian blue stains secreted hyaluronic acid
What is the typical site of origin for medulloepitheliomas? What is the classic sign on histopath? Prognosis?
Ciliary body; these are congenital tumors arising from inner layer of optic cup; mostly benign
- Rosette formation
- Most are benign
What stains can be used to diagnose spindle cell tumors of blue eyed dogs? Most common breed?
Positive for vimentin and S-100, variably positive for GFAP
-Siberian Husky
What is the most common secondary uveal neoplasm? How common are ocular signs with this neoplasm?
Lymphosarcoma, with ocular signs (37%) second most common clinical sign after lymphadenopathy
Describe the characteristic appearance of keratitis caused by lymphoma.
Corneal edema and vascularization followed by perilimbal corneal infiltrates of neoplastic lymphocytes (dense white band) 2-3 weeks later
T/F: Bone marrow involvement is more common in dogs with lymphosarcoma associated ocular signs than those with lymphosarcoma and no ocular signs
True
How far caudally is the ora ciliaris retinae in each quadrant of the globe?
Superior and temporal 8 mm, 4 mm inferior and medial
Which step of a sector iridectomy has the most chance for hemorrhage?
most hemorrhage when cut base of iris because major arteriolar circle present in iris in 50% of dogs
What is the maximum degree of iris and ciliary body that should be removed in an iridocyclectomy?
90 degrees or can cause phthisis bulbi
What are the selection criteria for laser photocoagulation for iris melanoma?
Lesions isolated to iris with no evidence of complicating factors
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