equine ophthalmic exam Flashcards
List 4 relatively common eye conditions in horses
corneal disease
trauma
uveitis
cataracts
Describe the optic disc in horses
Large Disc with lots of small vessels
all in the non-tapetal fundus (this is different to other species)
List 4 response/ reflexes to test in the eye
menace
PLR
Dazzle
palpebral/ corneal
to block the motor function to the eye in the horse- what block do we do
auriculopalpebral NB
what is slit-lamp ophthalmoscopy useful for assessing
the anterior segment
and depth of lesions
shows opacities in the aqueous
what is a panoptic ophthalmoscope used to assess
Fundic visualization with myosis
Cannot use for superficial layers- e.g. corneal lens
what do mydriatics do- an example of one used in horses
used to dilate the pupil for a thorough exam of the posterior segment
tropicamide- needs 20 mins to dilate the pupil
how to perform indirect ophthalmology in horse
Need to dilate pupil
Arm-length distance
2-3cm from eye
Image upside-down
only for fundic exam- peripheral lesions
how to perform tonometry in horses
Average of 3 separate readings
Normal IOP ~14-22mmHg
perform perpendicular to central corneal
list 2 drusg used for topical anaesthesia in horses for use near eye
Tetracaine
Proxymetacaine (aka proparacaine)
what can cause low intra ocular pressure
leakage
sedation- xylazine or ACP
what can cause high intra ocular pressure
Glaucoma- true
Causes of false high IOP:
Fibrosis, oedema (False elevation)
Higher without palpebral NB
low head position (even with sedation)
what is the normal result of schirmir tear test in horses
Normal wetting >10mm + clinical signs
List 4 signs of eye pain in horses
Myosis
Blepharospasm
Epiphora
± Swelling
List 3 ways to assess integrity of epithelium in eye
Fluorescein- most used
Rose Bengal/Lissamine Green
Seidle test
List 5 things that are routinely done when assessing eyes in first opinion practice
Naked eye examination
Nerve blocks
Fluoroscein/ Rose Bengal dye
Focal light source
Direct ophthalmoscopy
what is the corpora nigra
the black pigmentation at the edge of the irsis in the equine and ruminant eye
what is blepharopasm
blinking or other eyelid movements, like twitching, that you can’t control
Decsribe the palpebral reflex
diagnostic test in which the eye should blink in response to touch to the medial canthus of the eye
Describe the corneal reeflex
blinking in response to corneal stimulation by a cotton wisp
describe indirect PLR
pupil in the contralateral eye constricts in response to light shining in the other eye
do you need sedation to do an equine ophthalmic exam
yes - alpha 2’s and butorphanol is a common combination given
what does the supraorbital nerve block block
sensory feeling to the upper eyelid
what is aqueous flare
turbidity of the aqueous humor caused by increase protein levels and cells - sign of uveitis
why should we not use atropine for a clinical exam
this can last up to 2 weeks and mean the horse will be sensitive to light for a while
