Ch.39Eye Flashcards
Although tear deficiencies are uncommon in large animals, what is the normal Schirmer tear test?
**can check in 30 seconds
> 20mm is normal
define micropapilla
hypoplasia of the optic disk
define pappilledema
elevation of the optic disk
define cupping of the optic disk
depression
What are the layers of the cornea
1.epithelium
2. Bowmans layer
3. Stroma
4. Descemets membrane
5. Endothelium
**first 3 layers uptake stain
Congenital strabismus is reported in what breeds of cattle
Jersey
shorthorn
Holstein
German Brown Swiss cattle
Causes of enophthalmos
dehydration
loss of retrobulbar fat and/or muscle
congenitally shallow orbit
sympathetic denervation
pain and assoc retraction of globe
microphthalmos
globe rupture
Causes of Exophthalmos
Trauma: hemorrhage, tissue swelling
orbital neoplasia
inflammatory orbital lesion: foreign body, cellulites, abscess, granuloma, cyst, CN VI lesion (loss of retractor bulbi)
Causes of microphthalmos
viral: bovine viral diarrhea (BVD)
Genetic:
Teratogenic
define anisocoria
pupillary asymmetry
Differentials for anisocria
1.primary iridal lesions
2. Neurologic disorders (horners syndrome, oculomotor n dysf)
3. Intraocular dz (uveitis, glaucoma, etc)
4. Dzs involving optic nerve or brain stem
5. Previous use of pharmacologic agents (atropine)
ocular squamous cell carcinomas commonly arise from
nonpigmented tissues of:
-nictating membrane
-lateral limbal region
-eyelid margin
Suspected pathogenesis of damage to optic nerve
1.shearing forces at optic foramen from displacement of the brain after severe head trauma
2. direct contusion or avulsion of the optic nerve
3. loss of blood supply to the nerve and subarachnoid hemorrhage
Traumatic optic nerve atrophy is characterized by:
1.onset of uniltaeral or bilateral blindness
2. dilated fixed pupils
3. lack of menace repsonse
What are delayed clinical findings in a traumatic optic nerve blindness
- w/in 3 to 4 weeks of trauma, examinatin of fundus revealed a pale optic disk
- loss of peripapillary retinal vessels
-depression of optic disk– inc prominence of hte lamina cribrosa
How does acetylcysteine work as a collagenase inhibitor?
binds calcium– inhibiting collagenases and metalloproteinases
Define uveitis
inflammation of the uveal tract
What structures are included in the uveal tract?
iris
ciliary body
choroid
What isolates commonly cause keratoconjunctivitis in goats and sheep?
Mycoplasma conjunctivae- goats and sheep
Mycoplasma mycoides subsp mycoides- goats
Acholeplasma oculusi (oculi)- sheep and goats
Mycoplasma agalactiae and arginini
Differential diagnosis for Mycoplasma keratoconjunctivitis
-Chlamydophila spp (sheep)
-Branhamella spp.
aerobic bacteria
parasites
infectious bovine rhinotracheitis (goats)
noninfectious causes (trauma)
Diagnosis of Mycoplasma keratoconjunctivitis: what is seen on conjunctival scrapings
–>neutrophils, later lymphocytes
–plasma cells and necrotic epithelial cells
–organisms found in epithelial cell cytoplasm in coccobacillary or varied forms
If Mycoplasma conjunctivae is cultured from goat with keratoconjunctivitis, does that mean it is causing disease?
No, a subclinical carrier states exist
Treatment recommendation for Mycoplasma keratoconjunctivitis?
-recover spontaneously in 10 days
- some may have recurring episodes that last several weeks
Most lambs that develop keratoconjunctivitis with this bacterial agent, will also develop polyarthritis
chlamydia pecorum
Treatment of Clamydia pecorum keratoconjunctivitis cases
-usually resolve on own in 2 to 3 weeks
Bacterial keratitis in horses– what bacteria can cause ulcers?
no bacteria are known to initiate corneal ulcers in horses– all opportunistic bacteria
Examples of bacteria that can be normally cultured from the equine eye:
Corynebacterium
Streptococcus
Staphylococcus
Bacillus
rarely Pseudonomas spp
other gram neg bacteria
rods/ Gram negative organisms seen on corneal cytology, which antibiotics should be used
bacitracin-neomycin- polymixin B
aminoglycoside antibiotics (gentamicin, tobramycin)
fluoroquinolones (ciprofloxacin, ofloxacin)
cocci/gram positive organisms seen on corneal cytology, which antibiotics should be used
bacitracin-meonycin polymyxin B
neomycin polymixin B-gramicidin
chloramphenicol
levofloxacin
cefazolin
penicillin or ampicillin
What are the most common fungal organisms cultured from equine cornea?
Aspergillus and Fusarium spp
**many other spp of other genera also have bene cultured
Natamycin may be used as a topical antifungal, however what is its caveat?
and what is a good alternative?
It does not penetrate intact cornea
voriconazole– penetrates an intact cornea
What is a good drug to use when yeast is causing a fungal keratitis?
amphotericin B– howver it is irritating to the eye
Viral agents in horses that cause keratitis?
EHV-2 and -5
Besides ocular disease (conjunctivitis), what other manifestations of disease will occur with BHV-1
upper respiratory tract signs: rhinitis, dyspnea, pyrexia, dec in milk yield
abortion
BHV-1 conjunctivitis results in lymphoid hyperplasia, which is visible as
white plaques
Prion proteins of scrapie can be found in what ocular structure and may allow antemortem diagnosis of scrapie?
nictitating membrane
What is the most common orbital neoplasia in cattle?
bovine lymphosarcoma
– unilat or bilat exopthalmos
Differential considerations for progressive exopthalmos in cattle include:
bovine lymphosarcoma (orbital)
orbital cellulitis (actinomycosis or actinobacillosis)
frontal or maxillary sinusitis
nasal or orbital neoplasia (SCC)
Tuberculosis in cattle caused by Mycobacterium bovis may cause what lesions in affected eyes?
granulomatous lesions of uveal tract (initially)
What are clinical signs of infectious Bovine keratoconjunctivitis (IBK)?
corneal ulceration
corneal edema
photophobia
blepharospasm
lacrimation
Is there a genetic association with formation of infectious bovine keratoconjuncitivitis?
yes
–hereford fresian cross bred calves with full eyelid pigmentation had lower incidence of IBK vs calves with less than total pigmentation
-5 signal nucleotide polymorphisms on bovine chromosome 20 that are significantly assoc with IBK have also been identified
What bacteria has been associated with infectious bovine keratoconjunctivitis?
Moraxella bovis
–other agents: infectious bovine rhinotracheitis (IBR) virus and mycoplasma spp
What are risk factors for infectious bovine keratoconjunctivitis?
flies
solar irradiation
mechanical trauma form plant awns
What has been shown to reduce infectious bovine keratoconjunctivitis within a herd?
insecticide-impregnate ear tags or back and face rubbers to reduce fly populations
What is the difference between pathogenic and nonpathogenic moraxella bovis?
pathogenic- hemolytic
nonpathogenic-non-hemolytic
What are the 2 major the Moraxella bovis proteins that have been linked to its pathogenicity?
pili– (type IV, N-methylphenylalanine type) allows bacteria to adhere to corneal epithelium
cytotoxin
Moraxella bovis cytotoxin plays what role in its pathogenecity?
pore-forming protein
– lytic activity is calcium depedent formation of transmembrane pores in target cell membranes
Moraxella bovis is susceptible to what antibiotics?
penicillin-subconjunctively
parenterla oxyttetracycline
florfenicol IM/SC
tulathromycin
Ceftiofure CFA
Type 1 hypersensitivity is manifested in the eye as
conjunctivitis– IgE mediated mast cell inflammatory increase in vascular permeability, constrict smooth mm, dilate blood vessels and activate luekocyte chemotaxis and complement cascade
Type II hypersensitivity (cytotoxic/cytolytic) has what 2 basic effector pathways that lead to cell destruction?
- opsonization, with INC efficiency of phagocytic destruction
- ab-dependent cellular cytotoxicity, inducing the release of enzymes capable of destroying cells and digesting basement membranes
- lysis of immunoglobulin bearing cells
Type III (immune complex) hypersensitivity may be associated with clinical signs seen in which diseases?
-pemphigus foliaceus
-post vaccine influenza– intraocular inflamm
-uveitis (implicated)
Diagnosis of allergic blepharoconjunctivitis is often presumptive, and elimination of other causes such as:
-trauma
-orbital inflammation
-neoplasia
-mechanical irritants
-conjunctival parasites
-other infectious agents (ocular and systemic)
In support of allergic etiology to blepheroconjunctivitis, what would be seenon cytology
eosinophils
What are ocular manifestations of pemphigus?
ulceration or crusting of eyelids
mucoid ocular discharge
conjunctival hyperemia with erosions
What is diagnostic of eosinophilic keratoconjunctivitis on cytology?
eosinophils
What is the believed mechanism of eosinophilic keratitis ?
toxic effect of eosinophilic major basic protein on the corneal epithelium leading to chronic corneal ulceration
Ceterizine (zyrtec) may be beneficial for use in treatment of eosinophilic keratitis for what mechanism?
H1 antagonist that may be useful in decreasing the migration and adherence of eosinophils
What treatments decrease the duration of eosinophilic keratitis?
oral steroids
-tx with oral ceterizine does not decrease treatment time, but were less likely to have recurrence
Superficial keratectomy in the treatment of eosinophilic keratitis will enhance healing time because
removal of the eosinophil-granule major basic protein
Although the stimulating antigen is unknown, what is the underlying immunological mechanism for ERU?
-delayed hypersensitivity reaction
-recurrent inflammatory episodes
Describe Chorioretinal scars, commonly referred to as peripapillary “butterfly” lesions and what disease they are associated with
multifocal depigmented or hyperpigmented foci on either side of the optic disk sequalae of chorioretinitis
ERU
Chronic recurrent uveitis is characterized by:
widespread posterior synechiae
iris depigmentation or hyperpigmentation
iris atrophy
Findings on ocular exam that are indicators of inflmamation that should be observed before a presumptive diagnosis of ERU
corneal edema or vascularization
synechiae (typically posterior)
iris color change
corpora nigra atrophy or “polishing”
lens capsular pigmentation
cataract
lens luxation or subluxation
vitreious opacities or traction bands
retinal detachment
peripapillary scarring
What breed is more likely to develop ERU?
Appaloosa
ocular disease caused by Onchocerca cervicalis is a result of
aberrant migration of noninfective microfilariae into the palpebral, conjunctival and corneal tissues
ocular onchocerciasis occurs mostly in what age group?
adult horses
Definitive diagnosis of onchocerca keratoconjunctivitis is made via
corneal or conjunctival biopsy
onchocerca corneal lesions:
-wedge shaped– base of triangle at the limbus characterized by varying degrees of superficial and deep neovascularization and cellular stromal infiltrates
Equine ocular habronemiasis occurs when larvae from what spp are deposited on ocular tissues?
Habronema muscae
Habronema microstoma
Draschia megastomas
Diagnosis of equine ocular habronemiasis?
demonstration of larvae in the granulomatou slesions or fistulous tracts
What is the treatment of choice for habronemiasis?
oral ivermectin or modixdectin– kills both adults and larvae in teh stomach
What parasite in the conjunctival sac of large animals are considered commensal but can cause clinical ocular idsease?
Thelazia spp nematodes
Ocular thelaziasis treatment
flushing/manual removal from nasolacrimal duct
–>ivermectin or doramectin– cattle
“sore head” is a disease of sheep that is caused by what nematode?
Elaeophora schenideri
How do sheep develop sore head or ocular elaeophoriasis?
- microfilariae produced and migrate into the capillaries of the face and head of deer
- biting flies (Hybomitra and tabanus) transmit the microfliariae to new hosts
ocular Elaeophoriasis is seen in sheep in what area of the United States?
Western US where sheep are grazed at high altitudes
What is the most common intraocular parasite in horses and donkeys?
Setaria
– other filarides found free in anterior chamber include Dirofilaria immitis and O. cervicalis
What is the most economically important neoplasm of cattole?
bovine ocular squamous cell carcinoma “cancer eye”
What is the economic impact of bovine ocular squamous cell carcinoma?
carcass condemnations
production losses
treatment expenditures
management costs
What is the difference in appearance of malignent vs pre-malignant bovine ocular squamous cell carcinoma?
pre-malignant: sm, white, superficial and elevated hyperplastic plaques or papilloma-like structures with verrucous surfaces
malignant: irregular, nodular, pink, erosive, invasive in nature, accomanying necrosis, foul odor
Differentials for bovine ocular squamous cell carcinoma
conjunctival follicular hyperplasia
dermoid
fibroma
fibrosarcoma
granulation tissue
infectious bovine keratoconjunctivitis
lymphosarcoma
mastocytoma
Although ocular squamous cell carcinoma has been reported ina wide variety of cattle breeds, what breed i smost often diagnosed and why?
Hereford breed
– result of common use of breed as a range animala nd strong genetic trait for a white face
Differentials for ocular SCC in the horse
adenocarcinoma
adenoma
angiosarcoma
basal cell tumor
conjunctival follicular hyperplasia
dermoid fibroma
fibrosarcoma
grnaulation tissue
habronemiasis
lymphosarcoma
mastocytoma
plasma cell tumors
sarcoid
sschwannoma
Treatments for ocular SCC in horses
-excsision of corneolimba or corneal SCC via keratectomy with adjunctive therapy:
radiation therapy
cryonecrosis (liquid nitrogen)
radiofrequency hyperthermia
intralesional cisplatin or carboplatin
What is the most common neoplasm of dairy cattle?
bovine lymphosarcoma
Equine lymphosarcoma is usually a manifestation of
multicentric lymphoma
What is the second most common eyelid tumour of horses?
-sarcoids
What has been detected in association with equine sarcoidosis?
bovine papillomavirus (BPV-1 and BPV-2)
What breeds are predisposed to development of sarcoids?
Highest risk:
Quarter horses
Appaloosas
Arabians
