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