Surgical Conditions of the Eye Flashcards
which part of the eye has the photoreceptor cells?
retina
what are the corners of the eye called?
medial and lateral canthus
what is the junction between the sclera and the cornea?
limbus
what is the choroid?
vascular layer which supplies nutrients to the eye
what is the sclera?
protective covering which circles most of the entire eyeball
what is the cornea?
the transparent part of the eye that covers the iris and the pupil and allows light to enter the inside
what is the iris?
coloured part of the eye, controls pupil size
which part of the eye changes the shape of the lens?
ciliary muscle within the ciliary body
what does the lens do?
focuses light onto the retina
what is the pupil?
hole made by the iris, permits light onto the retina
what is the “normal” shape of a dogs eye?
almond shaped
how much sclera should you be able to see in a dog?
small amount medially and laterally
abnormal to see any ventrally or dorsally
what equipment is required for an ophthlamic exam?
dark room
pen torch/flashlight
direct ophthalmoscope
20D condensing lens
tonometer
consumables (fluorescein, schirmer test strips)
what is considered appropriate restraint for ophthalmic examination?
minimal is best, calm and confident
patient seated at edge of table
place one hand over back towards chest and one hand supporting under the chin
may need muzzle/towel/chemical restraint for fractious patients
what considerations should be made when restraining a blind/potentially blind dog?
talk to them before you approach
go slow
guide them carefully when walking
what considerations should be made when restraining a blind/potentially blind dog?
talk to them before you approach
go slow
guide them carefully when walking
what considerations should be made if a patient has a painful/fragile eye or increased IOP?
no neck leads, gentle handling
keep stress/barking to a minimum
no jugular samples or temperature checks
may need to sedate prior to placing IV catheter
ensure smooth recovery from anaesthesia
what are the 7 main steps of an ophthalmic exam?
- history
- distant and close examination
- schirmer tear test
- sample collection if required
- neuro-ophthalmic examination
- close direct opthalmoscopy
- indirect ophthalmoscopy
how should history be taken during an ophthalmic exam?
start broad then narrow down to presenting ophthalmic complaint
signalment, general history
known illness/signs of other illness
previous ocular conditions/any treatment
current ocular complaint/any treatment
what is assessed during the distant and close examination?
animals attitude, body condition
face - symmetry, ocular discharge
eyelids - palpebral fissure, size, colour, swelling
eyeballs - positions, size, direction, movements, retropulsion
observation of pupils - static and dynamic
use of direct ophthalmoscope (retro-illumination)
which tests are involved in the neuro-ophthalmic examination?
pupillary light reflex (bilateral constriction) dazzle reflex menace response tracking response visual placing maze test
what is close direct ophthalmoscopy?
looking at the detail of the ocular structures
what is indirect ophthalmoscopy?
use of a 20D condensing lens to see structures at the back of the eye
what is the schirmer tear test?
placement of test strips in the lower eyelid to assess tear production
normal dog = 15-25mm over 1 minute
what other common diagnostic tests might be part of the ophthalmic examination?
bacterial swab for cytology/culture and sensitivity
fluorescein staining
IOP measurement
gionoscopy
ocular ultrasound
electroretinogram
CT/MRI
how is IOP measured?
with a schiotz tonometer/tonopen/tonovet
topical anaesthetic required for tonometer/tonopen
what is normal IOP?
10-25 mmHg
what is high pressure in the eye called?
glaucoma
why might there be low pressure in the eye?
uveitis (intraocular inflammation)
what is gonioscopy?
evaluation of the internal drainage system of the eye - use of a special lens and LA
what are the indications for a gonioscopy?
patients with confirmed glaucoma/a risk of developing inherited glaucoma
what does an electroretinogram do?
test the function of the retina (non-invasive)
why might a CT/MRI of the eye be perfomed?
investigation of exophthalmos
main differentials are retrobulbar abscess/neoplasia or foreign body
what is the term for left eye?
ocular sinister (OS)
what is the term for right eye?
ocular dexter (OD)
what is the term for both eyes?
ocular uterque (OU)
what are the steps for administering drops to a patients eye?
- Ensure that you have the correct medication for the correct eye
- Clean any discharge
- Hold the bottle/tube between your thumb and first two fingers of your dominant hand
- With your other hand, support the chin and lift it upwards slightly, holding the muzzle gently if required
- Come from behind the head towards the eye
- Using your finger, gently lift the upper eyelid and squeeze the bottle to apply one drop of the medication
- Rest the hand that is holding the medication on your patient’s head (this will decrease the risk of accidental injury to the eye from the nozzle)
- If tolerated, remain in that position for a few seconds, lifting the chin slightly allowing the drop to stay within the eye and disperse
what are the signs of ocular pain?
increased blink rate/blepharospasm
increased lacrimation and overflow
redness photophobia rubbing miosis third eyelid protrusion
what are the commonly used topical drugs in ophthalmology?
lubricants mydriatics topical antibiotics topical NSAIDs carbonic anhydrase inhibitors prostaglandin analogues
what do mydriatics do?
pupil dilation, muscle spasm release (uveitis), comfort
what do topical NSAIDs do?
treat inflammation within the eye
what do carbonic anhydrase inhibitors do?
reduce IOP
decrease production of aqueous humour
what do prostaglandin analogues do?
increase aqueous outflow (used in glaucoma treatment)
what should be considered on the pre-anaesthetic checklist?
physical examination
pre-anaesthetic blood tests
eye drops prior to surgery - most patients
IV catheter - hindlimb preferable (OIP considerations)
diabetics - insulin vs no insulin
which types of eye surgery do we clip for?
clip for eyelid surgery, not for corneal/intraocular
what is used for ocular preparation pre-surgery? what strength?
povidone iodine solution
1: 50 iodine/sterile saline for globe
1: 10 for eyelids
list the steps involved in surgical preparation for eyelid surgery.
1 .Wear gloves.
- Apply copious amounts of lubricating gel to the eye(s) e.g. Lubrithal, Viscotears.
- Use small, clean sharp clippers
- Clip area required as close to the skin without causing irritation
- Use gauze swabs and sterile saline to remove the gel and hair from the eye(s)
- Prep the globe first with 1:50 povidone iodine solution
- Then prep the eyelids (adnexa) with 1:10 povidone iodine solution
- After 3 minutes, flush the globe with sterile saline to prevent corneal toxicity
list the steps involved in prep for corneal/intraocular surgery/
- wear gloves
- prep globe with 1:50 povidone iodine solution
- after 3 minutes, flush the glove with sterile saline to prevent corneal toxicity
what is involved in setting up theatre for ocular surgery?
damp dust all surfaces, mop floor
arterial line set up, ventilator may be required if using neuromuscular blockers
prepare kit and consumables
referral setting: operating microscope, phacoemulsification machine
how do you clean microsurgical instruments?
remove any gross material with distilled water and soft nail/toothbrush
check instruments for damage
place in ultrasonic cleaner for 5-10 mins using a neutral pH cleaning solution
allow to air dry
place in microsurgical tray - in matting - should not touch one another
TST strip, double wrapped, sterilise by autoclave and allow to dry thoroughly
store flat
what temperature should the autoclave be for cleaning microsurgical instruments?
134-137°C
why are neuromuscular blocking agents used during ocular surgery?
keeps patient still
prevents normal rotation of eye during anaesthesia
what are the post-op care considerations for ocular surgery?
harness, no collar/lead walk no jugular samples buster/soft collar recognise and monitor pain administer pain relief and eye medication keep wounds clean keep patient calm
what is exophthalmos?
abnormal protrusion of the eyeball
e.g. due to orbital foreign body, tumour, abscess
what is globe proptosis?
eyelids trapped behind globe - emergency, can quickly develop into corneal ulcer
what is entropion?
inverted eyelids
can be primary or secondary (e.g. due to trauma or eyelid surgery)
what is keratoconjunctivitis sicca (KCS)?
lack of tears due to immune-mediated
destruction of the gland which produces tears
assessed via tear test
how is keratoconjunctivitis sicca treated?
topical medication - Optimmune and lubricants (life-long)
what is conjunctivitis?
inflammation of the conjunctiva
many causes
how are corneal ulcers visualised?
with fluorescein staining
what is uveitis?
inflammation within the eye - very painful
what is a cataract?
opacity of the lens
what is a common cause of retinal detachment in cats?
systemic hypertension (secondary to chronic renal failure)
