Opthalmology Flashcards
farm animal - primary eye diseases
infectious bovine keratoconjunctivitis - fly eye (pink eye/new forest disease)
iritis - silage eye
squamous cell carcinoma - cancer eye
foreign body
farm animal - secondary eye disease
eye lesion as a result of other disease
malignant catarrhal fever
IBR
Listeria
farm animal - systemic state indication in eyes
BVD - cataracts - youngstock, no associated blepharospasm or excessive lacrimation
septicemia - hypopyon - pus in anterior chamber (associated with meningitis)
endotoxemia - congested conjunctiva (Red puffy looking)
dehydration - sunken eyes
Fly eye - causes
spread by flies - more common in summer
moraxella bovis (gram -ve)
more common in youngstock
fly eye - signs
lacrymation - serous initially, can become mucopurulent
blepharospasm
varying degrees of keratitis - fluoroscein
ulceration and corneal pannus - vascularisation and reduction in vision
photophobia - can make handling difficult
pain
unilateral or bilateral
fly eye - treatment
topical antibiotic - cloxacillin - always need this
systemic/subconjunctival antibiotic injection - amoxycillin/oxytetracycline, behind eye
suture - local nerve block then either eyelids together or 3rd eyelid to eyelid - protect eye
eye patch
NSAIDs - very painful
fly eye - risk factors
flies
woodland
dust/chaff
UV light
viral pneumonia - reduced immune system and ocular discharge
fly eye - prevention
fly control - pour on, tags, parasitic wasps, slurry management, ventilation
graze away from woodland
good ventilation
vaccination available
Silage eye - causes
big bale silage feeding - listeria monocytogenes in badly bailed silage
could be secondary to trauma
more common in winter
silage eye - signs
miosis - contricted pupil
blepharospasm
corneal opacity - diffuse or multifocal
glaucoma
fibrin accumulation in anterior chamber
corneal vascularisation in advanced cases
differing from fly eye -
signs on inside of cornea
no corneal ulceration - -ve fluorescein
silage eye - treatment
acute - oxytetracycline and dexamethosone into conjunctiva, topical atropine if miosis
chronic - usually not effective, can resolve without treatment but slowly and can have permanent blindness
silage eye - prevention
remove ring feeder - roll out silage
attention to bailing and wrapping of silage - prevent listeria growth
don’t leave bales open too long
cancer eye - risk factors
squamous cell carcinoma
older beef cattle - <5 yo
breed disposition - hereford and simmental
UV exposure - higher incidence in tropics
cancer eye - signs
unilateral
usually 3rd eyelid but anywhere in conjunctiva
swelling as tumour grows
local invasion of tissues
bad smell
cancer eye - management
surgical excision of 3rd eyelid
enucleation
usually just to hold them over to abattoir - reoccurrence high
encucleation
standing surgery - xylazine and retrobulbar block
elliptical incision around orbit
blunt dissection of conjunctival tissue to access retrobulbar space
ligate optic vessels - orbital packing to control haemorrhage
remove eye - cut optic nerves and vessles
suture eyelids together - simple interrupted - leave space to remove packing
packing removed 3-5 days later
foreign bodies - farm animal eye
straw, grass seed etc
can progress to keratitis
local blocks - easier examination
remove irritant and assess damage
antibiotics and pain relief
malignant catarrhal fever - cause
ovine herpesvirus2 - transmitted from contact with sheep or goats
cattle don’t transmit
malignant catarrhal fever - signs
runny eyes and nose
sudden depression, anorexia, and pyrexia
bilateral eye congestion, keratitis, and corneal opacity from outside in
mucopurulent discharge
leads to blindness
nasal discharge and crusting/sloughing off of muzzle
stomatitis
generalised peripheral lymphadenopathy
enteritis –> diarrhoea
malignant catharral fever - prevention and treatment
diagnosis - antibodies in serum, clinical digns, post mortem
no treatment - euthanasia
prevention - avoid contact with sheep/goats
IBR - eyes
bovine herpesvirus1
latent in trigeminal ganglion
vaccine availablae
runny eyes but mot as bad as MCF
pyrexia
conjunctivitis and discharge
corneal oedema
nasal lesions and discharge
tracheitis (differentiates from MCF)
milk yield drop
Sytemic listeriosis - eyes
listeria monocytogenes
infection via trigeminal or facial nerve - neuro damage causing secondary eye damage
encephalitis - circling in one direction
unilateral facial paralysis
depression
pyrexia
abortion
blindness - negative menace test
dry eye –> secondary keratitis (facial paralysis so can’t blink or move eye to move tears around)
large animal eye blocks - palpebral
lidocaine
subcutanrous at crest of rostral zygomatic arch
facial nerve (palpebral branch)
motor only, not sensation
innervation to eyelids
large animal nerve blocks - supraorbital
lidocaine
inject lidocaine over the depression of the supraorbital foramen
trigeminal nerve (supraorbital branch)
sensory
analgesia to upper lids