Opthalmology Flashcards
where are the medial and lateral canthus of the eye located?
medial is the meeting point of the upper and lower eyelids on the medial aspect of the eye
the lateral canthus of the eye is on the lateral aspect
what is the conjunctiva formed of?
connective tissue
what is the iris of the eye formed of?
muscle
where does the nasolacrimal duct open?
into nose and mouth
what is the limbus of the eye?
area where cornea meets sclera
what is the sclera?
tough protective outer covering of the eye
what is the retina?
area at the back of the eye with photo-receptor cells
what is the choroid of the eye?
vascular layer of the eye below the retina
what shape should normal dog eyes be?
almond
what is the palpebral fissure?
gap between eyelids
where should sclera be seen in healthy eyes?
small amount medially and laterally
none D/V
what equipment is required for an ophthalmic exam?
dark room pen torch direct ophthalmoscope 20D condensing lens tonometer consumables including Fluorescein, Schirmer tear test strips
how should a patient be restrained for ophthalmic exam?
minimal is best
calm and confident
patient seated at the edge of the table or on floor against nurses legs if large
one hand over the back and round to the chest
one hand supporting under the chin to hold head horizontal
how should fractious patients be managed for ophthalmic exam?
muzzled
towel
chemical restraint if necessary (will alter some ophthalmic parameters)
how should blind/visually impaired patients be handled?
talk before you approach them
go slowly
guide them carefully while walking to prevent them walking into things
how should patients with painful/fragile eyes or raised intraoccular pressure (IOP) be restrained?
no pressure on the neck harness not lead gentle handling low stress minimise barking avoid temperature checks sedation needed to place IV smooth anaesthetic recovery
where should the IV be placed in patients with painful/fragile eyes or riased IOP?
saphenous vein
what are the steps involved in an ophthalmic exam?
history distant examination and close examination Schirmer tear test (sample collection) neuro-ophthalmic exam close direct ophthalmoscopy indirect ophthalmoscopy
what should questioning about history in an ophthalmic patient be focused around?
overall health then narrow down to presenting complaint
what questions should be involved in the history part of the ophthalmic exam?
signalment
general history
known illness or any other signs
previous occular conditions and any treatment
current occular complaint and any treatment
how good is animals vision (do they bump into things)
what is involved in general history questioning during an ophthalmic exam?
vaccination
travel
other animals
what is involved in the distance and close exam stage of the ophthalmic exam?
animals attitude body condition face eyelids eyeballs observation of pupil use of direct ophthalmoscope for retro-illumination
what is assessed about the face during the distance and close exam stage of the ophthalmic exam?
symmetry
any occular discharge
what is assessed about the eyelids during the distance and close exam stage of the ophthalmic exam?
palpebral fissure (size, does it close)
size of eyelids
colour
swelling
what is assessed about the eyeballs during the distance and close exam stage of the ophthalmic exam?
position size direction movements retropulsion
what is assessed about the pupil during the distance and close exam stage of the ophthalmic exam?
static - symmetry, size and shape
dynamic - PLR
what is retro-illumination?
ophthalmoscope is shone at eye from a distance to look at tepetum and anything that may block the reflection from it
why are the diagnostic tests performed early in the ophthalmic exam?
before the eye is irritated by the more invasive exams
what is involved in the neuro-ophthalmic examination?
reflexes and tests of vision
what are the reflexes tested during the neuro-ophthalmic exam?
PLR dazzle reflex menace response tracking response visual placing maze test (bright and dim light)
what are you looking for during PLR tests?
bilateral pupil contraction
what is the dazzle reflex?
shining a bright light into the animals eye to look for eyes to close
what is the tracking response?
animal should follow something that is dropped in front of them with their eyes (not food as may follow nose)
what is the maze test?
obstacle placed in animals way and they have to navigate it to reach owner - if they knock into it it indicates their vision is affected
what is close direct ophthalmoscopy used for?
magnification to look at detail of the ocular structures
what is involved in indirect ophthalmoscopy?
ophthalmoscope used as light source with the condensing lens placed in front of the eye
what is indirect ophthalmoscopy used for?
examination of retina
what is needed for indirect ophthalmoscopy?
large pupil - may need midriatic agent e.g. atropine
what are the common diagnostic tests used in ophthalmology?
Schirmer tear test bacterial swab for cytology, culture and sensitivity Fluorescein staining intraoccular pressure measurement gonioscopy occular ultrasound electroretinogram CT and MRI
what is involved in the Schirmer tear test?
paper placed over lower eyelid with the end touching the cornea
dye will move along paper as tear are absorbed
what is the Schirmer tear test result for a normal dog?
15-25mm over 1 minute
what are the main pieces of equipment used for IOP measurement?
Schoitz tonometer
Tonopen
Tonovet
what must be used with Schiotz tonometer and the tonopen?
topical anaesthetic
what is normal IOP?
10-25 mmHg
what may high IOP indicate?
glaucoma
what may low IOP indicate?
uveitis
what is the indication for performing gonioscopy?
patients with a risk of developing inherited glaucoma
patient with confirmed glaucoma (raised IOP)
what is applied prior to performing gonioscopy?
local anaesthetic
what is tested on an electroretinogram?
function of the retina by monitoring electrical signals from cranial nerves
what are CT and MRI used for in ophthalmology?
exophthalmos
what are the main reasons for exophthalmos?
retrobulbar abscess
retrobulbar neoplasia
foreign body
what is Fluorescein used for?
detection of ulcers
what is the purpose of gonioscopy?
use a lens to view the drainage angle of aqueous humor from the eye
what does OS stand for?
occular sinister - left eye
what does occular sinister mean?
left eye
what does occular dexter mean?
right eye
what doe OD stand for?
occular dexter - right eye
what does OU stand for?
occular uterque - both eyes
what does occular uterque mean?
both eyes
what is essential when giving eye drops?
do not touch surface of the eye with the nozzle or you finger
describe the process of administering eye drops
- 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)
what are the signs of occular pain?
increased blink rate blepharospasm increased lacrimation and overflow redness photophobia rubbing miosis third eyelid protrusion
what is suggested by third eyelid protrusion?
retraction of the globe due to pain
how can animals with eyes removed be assessed for occular pain?
view response to contact with the head / eye area
look for flinching/moving away
look for other general pain signs e.g. depression
what are the main types of topical medication used for ophthalmology?
lubricants mydriatics topical antibiotics topical NSAIDs carbonic anhydrase inhibitor prostaglandin analogue
what are lubricants used for in ophthalmology?
Provide a protective layer to the eye Support patients with dry eye Soothes eyes Lubricant Post op
what are mydriatics used for in ophthalmology?
Short term pupil dilation for detailed ophthalmic exam
Long term muscle spasm release for uveitis
Comfort
what are topical antibiotics used for in ophthalmology?
treatment and prevention of bacterial infection
what are topical NSAIDs used for in ophthalmology?
Treat inflammation within the anterior portion of the eye
what are carbonic anhydrase inhibitors used for in ophthalmology?
treatment of glaucoma
Reduce IOP by decreasing the production of aqueous humor and so reducing pressure in the eye
what are prostaglandin analogues used for in ophthalmology?
Increase aqueous outflow to help with glaucoma
what are common examples of ophthalmic lubricants?
Lubrithal
Optixcare
what are common examples of ophthalmic mydriatics?
Tropicamide
Atropine
what are common examples of ophthalmic topical antibiotics?
Isothal
Chloramphenicol
what are common examples of topical NSAIDs?
Acular
what are common examples of carbonic anhydrase inhibitors?
Trusopt
Cosopt
what are common examples of prostaglandin analogues?
Latanoprost
Monoprost
what should be done pre-anaesthesia for a ophthalmic procedure?
physical exam to assess for systemic issues and to assign ASA grading
pre-anaesthetic blood tests if indicated
eye drops needed?
IV catheter
what insulin requirements does the patient have if diabetic
when should eye lubrication be used?
GA and sedation
any opioid use
where can IV catheters be placed in ophthalmic surgery?
saphenous vein to reduce venous pressure increase which will affect IOP
IV placed after sedation
when should clipping be performed for occular surgery?
yes for eyelid
no for corneal or intraoccular
what should be used to prep the area for ophthalmic surgery?
povidone iodine solution
what should never be used to prep for occular surgery?
scrub or tincture should never be used
what dilution of iodine should be used for the globe?
1 part povidone iodine to 50 parts sterile saline
what dilution of iodine should be used for the eyelids?
1 part povidine iodine to 10 parts sterile saline for the eyelids
how should surgical prep for the eyelid be performed?
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
what is the role of the lubricating gel on the eyes during prep?
protects the eyes from hair
why is it essential that clipper irritation is reduced in ophthalmic surgery?
will cause post-op irritation
why does the povidine iodine need to be removed from the globe?
prevent corneal toxicity
how should the eye be prepped for corneal or occular surgery?
wear gloves
prep the globe with 1:50 povidine iodine solution
after 3 minutes flush with sterile saline to prevent corneal toxicity
how should theatre be set up for ophthalmic surgery?
damp dust all surfaces and equipment, mop the floor
set up arterial line, operating microscope, phacoemulsification machine (if cateract surgery)
ventilator set up if required
prepare kit and consumables
why may neuromusular blocking agents be needed in ophthalmic surgery
prevents the eye rotating ventromedially under GA which facilitates surgery
how should microsurgery instruments be cased for?
very delicate so handle with care
how should microsurgical instruments be cleaned immediately after surgery?
remove any gross material with distilled water and soft nail brush / tooth brush
check instruments for damage
place in ultrasonic cleaner for 5-10 mins in neutral pH cleaning solution
how should micro surgical instruments be placed in the ultrasonic cleaner?
on a finger mat, not touching each other to prevet damage
how should microsurgical instruments be dried?
air dry not towel
how should micro surgical instruments be autoclaved?
on micro surgical tray in silicone finger mat not touching
TST strip, double wrap
what should you ensure has happened to micro surgical instruments before they are stored after autoclaving?
allow to dry throughly
what is involved in the post op care of ophthalmic patients?
harness not collar and lead no jugular samples buster / soft collar recognise and monitor main analgesia eye medication keep wounds clean keep patient calm to prevent raised IOP
what effect does increased venous pressure have on IOP?
increase
what is a complication associated with intraoccular surgery?
glaucoma
what are some common ocular conditions seen commonly in practice?
exopthalmos globe proptosis entropion keratoconjunctivitis sicca (KCS) conjunctivitis corneal ulcer uveitis cataract retinal detatchment
what is exophthalmos?
abnormal protrusion of the eyeball (rostrally)
what can cause exophthalmos?
FB
abscess
neoplasia
what is globe proptosis?
eyelids trapped behind globe and eye then pushed forwards out
what advice should be given to owners of pets with globe proptosis?
keep eye moist and come in quickly
what is entropion?
eyelids are inverted so skin of eyelid rubs on the cornea
what are the reasons for entropion?
primary
secondary - trauma or eyelid surgery
what is keratoconjunctivitis sicca (KCS)?
dry eye
what causes keratoconjunctivitis sicca (KCS)?
inadequate tear production lets occular surface become very dry
thought to be immune mediated
how is keratoconjunctivitis sicca (KCS) diagnosed?
assess tear production via Schirmer test
how is keratoconjunctivitis sicca (KCS) treated?
topical medication to treat (optimmune and lubricants) for life
what is conjunctivitis?
inflammation of conjunctiva
what are the causes of conjunctivitis?
many
what causes a corneal ulcer?
erosion of surface of cornea
how are corneal ulcers diagnosed?
Fluorescein dye
what is uveitis?
painful inflammation of the eye
what is cataract?
opacity of the lens
what is a hypermature cataract?
complete opacity of lens
what is retinal detachment?
retina moves away from its attachment point at the back of the eye
what are some of the main causes of retinal detachment?
systemic hypertension
CKD
what are some of the signs of retinal detachment?
mydriasis
unresponsive to light
what is normal IOP?
10-25 mmHg
what causes glaucoma?
Eye pressure is to high as aqueous humour cannot drain out of normal drainage angle properly
how does fluroscein show corneal ulcers?
Fluroscein only sticks to stroma of eye so will go green as epithelium will be gone and dye can stick
what must be done after fluroscein has been used in the eye?
flush
what is needed for culture and sensitivity tests on the eye?
sterile swab
what are the punctae of the eye?
opening of nasolacrimal duct in eye
what covers the sclera?
conjunctiva
what is the role of the suspensory ligament of the eye?
attaches lens to cilliary body
what is the role of the choroid?
supplies nutrients to retina
