Ophthalmology Flashcards
what are the top 4 signs of eye pain?
blepharospasm (increased blink rate)
reduced palpebral fissure
ocular discharge/epiphora
hyperaemia (redness)
what are the main local signs of eye pain?
photophobia
miosis
third eyelid protrusion
head-shyness
self-trauma/rubbing
what are the systemic signs of eye pain?
reduced appetite
quiet/subdued
depressed/lethargic
headache?
what are the main streps in triaging eye pain?
identify systemic signs
brief description of ocular signs
establish onset and duration
when should patients with suspected eye pain be assessed?
sam day as identified if possible
what eye condition may affect pain scoring?
blepharospasm, especially in cats/horses - must be taken into account
how can we treat scratchy dry lids?
lubrication with HA drops
how can we treat an acutely painful indolent ulcer?
bandage contact lens
how can we treat cramping spasm uveitis?
atropine/cyclopentolate drops (relieves pressure and relaxes iris)
how can we treat the chronic searing ache of intractable glaucoma?
enucleation - can’t be treated medically
how can we treat the dull ache experienced with orbital swelling?
NSAIDS +/- opioids
how can we treat eye pain with an unknown cause (cannot open eye to examine)?
local/sedation/GA? - cause must be identified
how should we handle patients with reduced vision/blindness/painful/fraglle eyes?
guide carefully, avoiding bumps
talk to them
go slowly, introduce hands to body before head
how can we handle these patients appropriately for examination?
assess temperament - requires proximity to face
keep steady and calm
end of table
reward and reassure
what are the main causes of vision loss?
cataracts
glaucoma
SARDS
toxins
progressive retinal atrophy
brain disease/trauma
what can cause cataracts?
can be inherited or due to diabetes
why does glaucoma occur?
primary - inherited genetic defect
secondary to intraocular neoplasia, uveitis, lens luxation
how is glaucoma managed?
medically managed initially
can have surgical shunt implant, laser TSCP/ECP but will ultimately require enucleation
what is SARDS and how is it diagnosed?
sudden acquired retinal degeneration syndrome
diagnosed via electroretinogram - flat line
how is SARDS treated?
no treatment available
what toxins can cause vision loss?
ivermectin poisoning
enrofloxacin in cats
how does progressive retinal atrophy progress?
night vision is lost first, then day vision
how is progressive retinal atrophy diagnosed?
simple maze test with light off and on
ERG will show rods not responding if night vision is lost
how do patients adapt to vision loss?
usually adapt well - smell and hearing are more important than vision
how can we give advice on owner homecare for patients with vision loss?
online forums can be good
buster collars/guide leads/bump bars in house
doggles/rex-specs to protect eyes
sound/voice commands important
behaviour modification training
lead walks offer more support - act as reverse guide dog
why is it important to treat eye ulcers?
very painful
infection risk
risk of keratomalacia (‘melting’)
perforation –> endophthalmitis –> glaucoma –> phthisis –> blindness
can ulcer heal without treatment?
very simple ulcers generally heal in around 7 days without treatment
what does the cornea consist of?
transparent stratified squamous epithelium
what is the limbus?
transition zone between the cornea and sclera
where are the stem cells located in the eye?
limbus
what is contained in the limbus of the eye?
stem cells
what is the sclera?
fibrous tunic of the eye
what is the role of the sclera?
gives globe rigidity
what are the stages of ulcer formation?
superficial
deep
descemetocoele
perforation
how are ulcers classified?
by depth of stroma affected
what does a descemetocoele look like when stained with fluoroscein?
donut
what % stromal loss is considered fragile eye?
> 50%
what makes an eye extremely fragile?
if ulcer down to descemets layer
why should you avoid increasing IOP?
could cause rupture
what could cause a fragile eye to rupture?
increase in IOP
what can cause an increase in IOP?
barking
jugular blood sampling
coughing/vomiting
pulling on collar
firm restraint
which breeds are often affected by fragile eyes?
brachycephalic breeds
how can we handle patients with fragile eyes to avoid raising iop?
avoid pressure on neck or lids
avoid jugular sampling - increased venous pressure = increased IOP
avoid stress, keep calm
question whether need to do STT/IOP/cytology
keep eye area clean
what is a SCCED?
spontaneous chronic corneal epithelial defect
what treatments are available for SCCED?
algar brush, grid
superficial keratectomy (100% success)
what is a superficial keratectomy?
removal of top layer of cornea
what treatments are available for stromal ulcers?
medical or surgical graft
what treatments are available for melting ulcers?
intense medical initially
+/- corneal cross-linking
corneal graft surgery
what treatments are available for desmetocoeles?
structural support imperative
corneo-conjunctival transposition (graft)
what treatments are available for perforation?
suture closed/patch/graft
what is the risk of perforation?
risks endophthalmitis
what are the inpatient considerations for eye surgery?
low stress
smooth pre-surgical preparation
smooth recovery post-op
reversal/repeat of premedicants?
horses - stables dark for atropine
what post-op care should be considered after eye surgery?
harness walks only
no jugular samples
buster/soft collar
closely monitor and treat pain
keep wounds clean and dry
keep patient calm
what types of trauma are ocular emergencies?
sharp trauma
blunt trauma
proptosis
penetrating foreign body
what is proptosis?
eyelids trapped behind globe
what are our priorities with ocular emergencies?
cardiovascular stability - ABC
analgesia
ocular surface support - lubrication
prevent further trauma - stabilise any FBs
buster collar to prevent self-trauma
what injury is common in puppies?
cat claw injuries - puppies don’t develop menace response until 8-12 weeks
what can happen to the eye with cat claw injuries?
corneal laceration
lens puncture/capsular tear
cataract formation
induction of lens-induced uveitis
how can cat claw injuries be treated?
cataract surgery with phaecoemulsification
corneal laceration repair
treat uveitis medically
what does glaucoma look like?
blue cornea, red sclera and conjunctiva
blindness and pain
what does chronic glaucoma look like?
buphthalmic eye. globe is stretched, looks enlarged
what is normal IOP?
10-25mmHg
what is glaucoma IOP?
> 30mmHg
why is glaucoma an emergency?
blindness in 24-48 hours
what could cause exophthalmos?
FB - could go in to orbit and cause retrobulbar abscess/cellulitis
dental work - elevator slip trauma
stick injuries - chewing/running into
what are the signs of retrobulbar mass/exophthalmos?
pain on opening mouth
exophthalmic eye
excessive conjunctiva is visible (esp third eyelid)
what is the function of lubricant eye drops?
protect, soothe, support healing
what is the role of antibiotic eye drops?
treatment or prophylaxis
what classes of anti-inflammatory eye drops are commonly available?
NSAIDs or steroids
what are immune modulator eye drops used for?
treatment of immune-modulate disease
what is the tole of anti-glaucoma drugs?
lower pressure in the eye
what do mydriatic eye drops do?
dilate the pupil e.g. atropine
what are anaesthetic eye drops used for?
diagnostics
pre-op
what classes of eye drops are used in practice?
lubricants
antibiotics
anti-inflammatories
immune modulators
anti-glaucoma drugs
mydriatics
local anaesthetics
what are serum eye drops made from?
fresh frozen plasma or serum - can be patients own or from donor animal (fresh)
what are the steps involved in making serum eye drops?
defrost plasma if frozen
place needle free fluid spike into plasma bag
draw up 3mls and transfer into bottles
what is important to remember when making serum eye drops?
keep process as sterile as possible - gloves, very clean table/sterile drape
where should serum eye drops be kept?
freezer - defrost in pocket for days use, store refrigerated
how long can serum eye drops be kept in the fridge?
max 3 days
what can serum eye drops be used for?
melting ulcers
prevention of keratomalacia
what are the considerations for administering eye drops?
clean any discharge
one drop is enough
leave 10 mins between each drop
leave 60 mins between each gel and ointment
don’t touch surface of eye with nozzle or finger
what is the order of administration of eye medications dependent on?
viscosity
how long should be left between aqueous drops and suspensions?
10 mins
how long should be left between suspensions and gels?
10 mins
how long should be left between gels and ointments?
60 mins
what is the role of ocular lubricants?
support healing all ocular surface disease
reduce evaporation
prevent ulceration pre-operatively
replace missing tears in KCS patients
provide comfort
what patient factors should we consider when preparing for ocular surgery?
physical mobility
systemic health - blood required?
conformation/concurrent BOAS
ocular complaint - eye drops required?
where/when should IV catheter be placed?
diabetic - insulin?
what are the anaesthetic induction considerations for ocular surgery?
smooth induction is ideal
monitoring equipment at back end if possible
armoured ET tubes and T connectors - non-kinking
neuromuscular blockade and ventilation may be required
what should be involved in clipping for eyelid surgery?
wear gloves
apply copious amounts of lubricating gel to the eye(s)
use small, clean sharp clippers, sharp scissors for eyelashes
clip area required as close to the skin as possible without causing irritation
flush hairs and lubricant away with saline
is clipping required for globe surgery?
no
what solution should be used for surgical preparation of the eye?
povidone iodine solution
never iodine scrub or tincture
what dilution povidone iodine solution should be used for the globe?
1:50 povidone iodine to sterile saline
what dilution povidone iodine solution should be used for the eyelids?
1:10 povidone iodine to sterile saline
what contact time is required for povidone iodine solution?
2 mins, then flush out with saline
what equipment might be required for ocular surgery?
surgical equipment
patient drapes (varied)
surgeons chair
gown, gloves, chair and equipment drapes
prepared saline flush
what extra equipment might be seen for ocular surgery at referral level?
operating microscope, sterile handles
ventilator and ‘muscle stim’ if NMB used
phaecoemulsification machine for cataract surgery
what surgical kits/consumables might be required for ocular surgery?
lid kit
corneal kit
phaeco kit
suture materials -
8.0 or 9.0 vicryl, spatulated need for cornea
5.0 or 6.0 vicryl for lids
stay suture material
what type of block should be considered for enucleation?
local retrobulbar block
what are the surgical techniques for enucleation?
trans-conjunctival - 2 phase
transpalpebral for en-bloc removal, suture first
what is the oculo-cardiac reflex?
reflex bradycardia on eye pressure (vagus)
why should surgeons avoid traction on the optic chiasm during enucleation surgery?
avulsion can blind fellow eye - especially in cats (shorter nerves)
what are the management options for haemorrhage during ocular surgery?
collagen pads
powders (surgicel snow)
adrenaline
pressure
what surgeries may be done in the general eye area?
entropion
mass removal
rhytidectomy
distichasis/ectopci cilia
media canthoplasty (pugs)
cherry eye surgery
lip to lip transpositions
parotid duct transposition
what surgical technique may be used to treat entropion?
Hotz-celcus technique
what surgical technique may be used for eyelid masses?
wedge excision
what techniques may be used to treat distichasis/ectopic cilia?
cryosurgery or electrolysis
what does distichasis mean?
extra eyelashes
what technique may be used to treat cherry eye?
pocket technique
why might a parotid duct transposition be performed?
for dry eye
what surgery might be used to treat dry eye?
parotid duct transposition
what is the main consideration for corneal surgery?
horizontal eye positioning - central eye often used
ventilator and NMB required
what is the goal of corneal surgery?
removal of damaged cornea
what techniques may be used for corneal surgery?
free or advancement graft e.g. CCT
what is the most common cause of blindness in veterinary patients?
cataracts
can cataracts be inherited?
yes - identifiable via BVA/KC/ISDS eye scheme
how can cataracts be acquired?
through diabetes mellitus
what preparation tests must be done before cataract surgery?
gonioscopy to check for glaucoma risk post-op
ERG to check functional retina before go-ahead
U/S for tumour check/angle check
finances arranged
what does gonioscopy do?
assess drainage angle of eye
what is gonioscopy used for?
looking for signs of inherited glaucoma
how can gonioscopy be performed?
patient conscious
LA drops required
referral level technique
can patients be conscious for ocular ultrasound?
yes
what anaesthetic can be used for ocular ultrasound?
local proxymetacaine
what can be seen with ocular ultrasound?
assessment of structures of eyes
lens structure, cataracts , retinal detachment, retrobulbar mass, foreign body
which lubrication gel is good for eye US?
optilube
what is an electroretinogram?
records retinal response to light stimulus
why is electroretinogram performed?
allows us to assess if the retina is functional
can the patient be conscious for electroretinogram?
can be done conscious or sedated
what is the likelihood of a patient with diabetes developing cataracts?
50% develop within 6 months
75-80% within a year
what are the risks of diabetic cataracts?
risk of lens capsule rupture and lens induced uveitis
does diabetes have to be well controlled before cataract surgery?
no
what is the advantage of performing cataract surgery?
restores vision - success rates often 85%+
what type of surgery is cataract surgery?
intra-ocular surgery
what is involved in pre-op work-up for cataract surgery?
electroretinogram
high frequency U/S of drainage angle and screen for detached retina/masses etc
gonioscopy to assess glaucoma risk
full blood and workup to check for comorbidities
what are the disadvantages of cataract surgery?
high post-op commitment
expensive - £5000 both eyes
impact of aftercare on home life - lifelong meds
lifelong rechecks q3m
what is phaecoemulsification surgery used to treat?
glaucoma
what is involved in post-op care after phaecoemulsification?
medications - up to 12x daily in first week
keep quiet for 2 weeks
topical steroids and NSAIDs to control uveitis
abs until wounds heal
lubricants for comfort
what are common anaesthesia risk factors for the ophthalmic patient?
mostly tend to be older patients
co-morbidities common
brachys are 25% caseload at referral
cardiac
what are the options for analgesia for ophthalmic patients?
topical proxymetacaine - diagnostic only
local - skin line or retrobulbar
systemic NSAIDs/opioids/CRI
why might a neuromuscular blockade be used in ocular surgery?
to achieve a central eye - paralysis of extra-ocular muscles
why are ophthalmic patients often on ventilators under GA?
neuromuscular blockade also paralyses intercostals –> paralyses breathing
what NMB is commonly used in ocular surgery?
atracurium
how is the duration of action of atracurium?
15-35 mins
how is atracurium given?
dilute in saline and give slowly IV to prevent histamine release
what should be monitored closely in patients who have had NMB for ocular surgery?
avoidance of hypothermia, acidosis and hypokalaemia (prolongs)
what is the advantage of using atracurium in ophthalmic surgery?
non-cumulative, so safe in heptic and renal patients
what abnormalities are seen with brachycephalic ocular syndrome?
lower medial entropion
shallow orbit
macropalpebral fissure
lagopthalmos
medial carancular trichiasis
pigmentary ketasis
epiphora from kinking of the N-L canaliculi
what does lagophthalmos mean?
sleeping with lids incompletely closed
what can epiphora in brachycephalic ocular syndrome be exacerbated by?
other concurrent issues such as dry eye disease or distichiasis
what are the considerations for diabetic patients having ophthalmic surgery?
monitor glucose throughout day - starve AM and withhold insulin
avoid hypoglycaemia
elevated fluid requirement
what are the risks with diabetic patients undergoing ocular surgery?
increased risks of:
systemic hypertension
dry eye
delayed healing
infection
how can we improve client communication and efficiency with regards to ophthalmic care?
educating owners about conditions
training clients to be effective with drops and training dog with rewards
habituation of brachy puppies to daily lubricants
easy tests to monitor or start tear supplements earlier
support medication compliance
what are the 3 layers of the tear film?
lipid layer
aqueous layer
mucus layer
what is the function of the lipid layer of the tear film?
prevents evaporation
aids distribution
what is the function of the aqueous layer of the tear film?
supplies corneal nutrition
antibacterial properties
removal and remodelling - proteases and antiproteases
what is the function of the mucus layer of the tear film?
lubrication
refractive properties
anchors aqueous layer to cornea
what is keratoconjunctivitis sicca?
deficiency of aqueous tear
does KCS develop quickly?
no - insidious onset
what breed groups are predisposed to KCS?
terriers
brachys
spaniels
bloodhounds, samoyeds
what quantitative tests are available for KCS?
schirmer tear tests and concurrent clinical signs
what is the normal range for the STT?
15-25mm/min
at what STT reading might we start to suspect KCS?
10-14mm/min
what STT reading is considered moderate KCS?
6-10mm/min
what STT reading is considered severe KCS?
0-5mm/min
what are the common clinical signs of KCS?
strings of adherent mucus
poor corneal clarity
poor corneal shine/poor Purkinje reflex
low STT reading
