ocular disease in cattle Flashcards
How far back should cattle eyes be easily retropulsed
5cm
What cranial nerves does the palpebral reflex test and when might it be absent
Sensation: trigeminal nerve CNV
Motor: facial nerve CN VII
May be absent in first 2 weeks of life; acquired reflex
What metabolic change can cause a sluggish palpebral reflex
Elevated D lactate (e.g with acidosis due to diarrhoea)
What cranial nerve does the menace reflex ecamine
CNII optic nerve and retina
+ motor from facial nerve (VII)
What solution to use to flush eye
5-10% povidine iodine in sterile saline
(recommendation is up to 20%)
What can happen if LA is accidentally injected into a vessle e.g while doing retrobulbar injections
Respiratory collapse and sudden death
What nerve block is used for eyelid akinesia
Auricular nerve block
What does a successful retrobulbar nerve block give
Mydriasis
Lack of globe motility (paralysis of extra ocular muscles)
No corneal reflex
What do we need to remember to do having done nerve blocks on the eye
Lubricate eye with ointment since block stops blinking
Also should use local anaesthetic infiltration of eyelid if we want to block sensation to this
What is orbit exteneration compared to enucleation
In exteneration remove the tissues around the eye as well as the eye
Do enucleation if no infectino
When would a orbit extenteration be especially indicated
With invasive squamous cell carcinoma behind the eye
What causes might be implicated in microphthalmia
In utero BVD infection
Toxic causes
Genetic; Guernsey, Holstein + related to cardiac and tail abnormalities
What does the individuals we see congenital cataracts in tell us about the cause
If in a group of age matched animals suggests a gestational accident e.g toxicity, deficiency (A, E, Se), BVD infection
If calves from same genetic line, suggests genetic e.g in Jersey
Dealing with dermoids
Do surgery to excise; if on the cornea do keratectomy
Topical antibiotic and atropine given for week
Cause of orbital cellulitis
Invasion of orbital soft tissue by opportunistic bacteria after puncture wounds or laceration in the area
What to do if exophthalmos from orbital cellulitis doesnt stop after 24 hours
DO a temporary tarsorrhaphy to protect the eye
Treating orbital cellulitis
Systemic broad spectrum antibiotics for 2 weeks
NSAIDs
Eye massage with gentle retropulsion
Tobical lubricants
Atropine if corneal ulceration
Which cattle are predisposed to new forest disease (infectious bovine keratoconjunctivitis)
Young cattle
Herefords esp i.e ones with less periocular pigmentation
Cause of infectious bovine keratoconjunctivitis (New Forest disease)
= moraxella bovis
Transmission mediated by flies
What things are risk factors for infectious bovine keratoconjunctivitis
Flies
UV light (so to manage can confine animal to avoid UV light)
Trauma/irritation of cornea
Anythings that increased ocular and nasal discharge and so facilitates spread e.g mycoplasma, IBR virus
Can we vaccinate for moraxella bovis
No not in the UK
Cause of silage eye = bovine iritis
Listeria monocytogenes
In stressed cattle fed improperly prepared big bale silage
When do we not want to use steroids in cases of eye issues and when might we
Don’t use in cases of ulceration as will impair immune syste
Do use in silage eye; topical dexamethosone to relieve uveitis
Clinical signs of silage eye
Epiphora, conjunctivitis, blepharospams
Progresses to NON-ULCERATIVE keratitis with marked corneal odema, uveitis
What is a primary neoplasm of the eye in cattle and which breeds do we see it in
Ocular squamous cell carcinoma
= malignant
Seen in cattle with unpigmented skin on their face e.g herefords, holstein freisan, simmental
Stages in development of ocular squamous cell carcinoma
Stage 1 = plaques
2 = keratomas; mainly on lower eyelid
3 = papilllomas
4 = carcinomas; more irregular and nodulat
Distribution of squamous cell carcinomas on eye and malignancy
Most on limbus 75%
15% on eyelids
10% on thrid eyelid
Those on third and lower lid are more aggressive and more likely to metastasize
What does ammonia or chlorine bleach contact with the eye cause
Severe and permanent corneal opacity due to epithelial necrosis and stromal injury (get stromal scarring)
