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
large animal nerve blocks - retrobulbar
lidocaine
curved needle between globe and bony orbit, inject at back of eye until the eye feels turgid
sensory and motor to whole eye - only for eye removals, risk of trauma to optic nerve or artery
Schirmer Tear Test
normal range - 15 - 25mm/min
dry eye (keratoconjunctivitis sicca) - under 15mm/min
measures aqueous component of tears
test before putting anything else in
cranial nerves affecting eyes and adnexa
2 - optic - sensory - eye reflexes
3 - oculomotor - motor - most eye muscles
4 - trochlear - motor - other eye muscles
5 - trigeminal - both (Sensory to eye) - corneal pain
6 - abducens - motor - other eye muscles
7 - facial - motor - facial expression muscles (inc eye)
8 - vesibulocohlear - both - balance (so can look like a vision problem)
eye neuro exam
menace response - learned, absent before 8 weeks in puppies and 2 weeks in foals
dazzle reflex - if dazzle but no menace then good chance can get vision back, nervous communication to brain still in tact (eg in cataracts if remove the cataract)
palpebral reflex - can have inability to blink and negative menace because of this rather than blindness
pupillary light reflex - direct and consensual
tonometry
normal pressures -
dog/cat - 15-25mmHg
horse - 16-30mmHg
should be max 5mmHg difference between the two eyes, if more need to work out which one is high/low
glaucoma - high pressure
uveitis - low pressure
false elevation through pressure on eye or jugular vein or position of head too low in relation to heart
measure before dilating pupils
ophthalmic dyes
fluorescein
jones test - fluorescein down nasolacrimal duct (open mouth in brachys)
rose bengal - tear film abnormalities, UV damaged cells, early squamous cell carcinoma
cytology eye
any ulcer with dimples
any fluorescein positive lesion - especially with opacity
any ulcer not holding normal shape
take 2 slides
look for rods, cocci, hyphae, neutrophils, eosinophils
culture and sensitivity
ophthalmic antibiotics
penicillins
aminoglycosides
tetracyclines
chloramphenicol
fusidic acid (isothal)
fluroquinolines
modes of action - protein synthesis, cell wall, cell membrane
ideally based on culture and sensitivity
first line - isothal and chloramphenacol - licensed in dogs, cat’s and rabbtis
melting ulcers - tetracycline - anticollaginase action
aminoglycosides and fluroquinolones - irritant, usually not ophthalmic preparations
ophthalmic antifungals
azoles
polyenes
echinocandins
treatment for fungal keratitis and fungal abscesses
fungal abscesses - white in appearance, painful, can form burrow
expensive and irritant, confirm fungal infection with cytology
not eye preparations - not formulated to pH and osmolarity
fungal culture - 5-7 days minmum
ophthalmic NSAIDs
ketorolac
bromfenac
voltarol
post operative inflammatory management
uveitis
analgesia
instead of or alongside topical steroids
ophthalmic steroids
dexamethasone
prednisolone
indications, uveitis, immune mediated/non ulcerative corneal disease, blepharitis, episcleritis
don’t use on ulcerated cornea or infection - cause slow healing, corneal mineralisation and thinning
fluorescein scheck regularly if on topical steroids
lacrimostimulators
stimulate tear production
ciclosporin
tacrilimus
less frequent use than tear substitues
lacrimomimetics
tear replacements/lubricants
sodium hyaluronic acid
carbomer based gels
ophthalmic pressure modulators
carbonic anhydrase inhibitors
beta blockers
prostaglandin analogs
indications - glaucoma
decrease aqueous humour formation or decrease outflow
side effects - local irritation, photophobia, blepharoconjunctivitis, hypokalemia in cats, miosis, uveitis, conjunctival hyperemia, iris darkening
mydriatics
cholinergic antagonists
tropicamide - visualisation in exam, onset 1 hour, duration 12 hours
atropine - onset 1 hour, duration 3-5 days, 2 weeks in horses - prolonged relief rather than exam
cyclopentate - 1 hour onset, 2-5 day duration (newer)
pupillary dilation and relief of ciliary spasm
avoid in glaucoma
can have profuse salivation and occassional vomiting
birds - neuromuscular blocking agent instead
solution …
drug totally dissolved in solvent
suspension …
solid particles of active ingredient dispersed in liquid (shake before use)
ointment …
semi solid gels and creams
enhanced contact time so less frequent use needed - better for large animals
causes of acutely painful eye
ulcers
abscesses
lacerations/trauma
foreign bodies
uveitis
glaucoma
lens luxation
species differences - enucleation
dog - oculocardiac reflex - acute drop in heart rate from pressure on globe
cat - don’t pull on optic nerve - damage at optic chiasm and contralateral vision loss
horse - standing surgery, nerve blocks
cattle - standing surgery, nerve blocks
rabbits - orbital venous plexus, bleeds a lot
IOP measurement
useful in uveitis - low IOP
digital tonometry - using fingers - very subjective, compare the two eyes and whether fingers sink in
applantation tonometry - tonopen - force required to flatten cornea
indentation tonometry - tonovet - depth of indentation made by small plunger
IOP ranges
dog/cat -
uveitis <10
normal 10-20
borderline 20-25
glaucoma >25
rabbit/horse -
uveitis <15
normal 15-25
borderline 25-30
glaucoma >30
tear duct flushing
usually rabbits with dental disease
flush through duct with IV catheter
opening in medial canthus external to nictitating membrane
flush with saline
normal duct - out through nose
nasolacrimal duct blockage - back out around catheter
risk of corneal trauma or duct rupture
grid or punctate keratotomy
promote corneal healing in indolent ulcers - removes loose and non-vitalised epithelium and stimulate release of inflammatory mediators
local anaesthetic
cotton bud to remove loose epithelium
grid lines with needle
risks of corneal puncture, pushing infection into cornea
contraindicated unless indolent ulcer
wedge resection
removal of eyelid margin masses and ectopic cilia
also for shortening eylid for conformational issues
can be done for eyelid masses up to 30% of eyelid length
v shape for smaller masses, four sided wedge for larger areas
do eyelid margin with figure of 8 suture
hotz-celsus procedure
to correct entropion
parallel cut in eyelid skin then crescent underneath
remove the inbetween skin
should be enough that when the edge are brough together the entropion is corrected
simple interrupted sutures
