equine ophthalmic exam

Question 1

List 4 relatively common eye conditions in horses

Answer 1

corneal disease
trauma
uveitis
cataracts

Question 2

Describe the optic disc in horses

Answer 2

Large Disc with lots of small vessels
all in the non-tapetal fundus (this is different to other species)

Question 3

List 4 response/ reflexes to test in the eye

Answer 3

menace
PLR
Dazzle
palpebral/ corneal

Question 4

to block the motor function to the eye in the horse- what block do we do

Answer 4

auriculopalpebral NB

Question 5

what is slit-lamp ophthalmoscopy useful for assessing

Answer 5

the anterior segment
and depth of lesions
shows opacities in the aqueous

Question 6

what is a panoptic ophthalmoscope used to assess

Answer 6

Fundic visualization with myosis
Cannot use for superficial layers- e.g. corneal lens

Question 7

what do mydriatics do- an example of one used in horses

Answer 7

used to dilate the pupil for a thorough exam of the posterior segment

tropicamide- needs 20 mins to dilate the pupil

Question 8

how to perform indirect ophthalmology in horse

Answer 8

Need to dilate pupil
Arm-length distance
2-3cm from eye
Image upside-down

only for fundic exam- peripheral lesions

Question 9

how to perform tonometry in horses

Answer 9

Average of 3 separate readings
Normal IOP ~14-22mmHg
perform perpendicular to central corneal

Question 10

list 2 drusg used for topical anaesthesia in horses for use near eye

Answer 10

Tetracaine
Proxymetacaine (aka proparacaine)

Question 11

what can cause low intra ocular pressure

Answer 11

leakage
sedation- xylazine or ACP

Question 12

what can cause high intra ocular pressure

Answer 12

Glaucoma- true

Causes of false high IOP:
Fibrosis, oedema (False elevation)
Higher without palpebral NB
low head position (even with sedation)

Question 13

what is the normal result of schirmir tear test in horses

Answer 13

Normal wetting >10mm + clinical signs

Question 14

List 4 signs of eye pain in horses

Answer 14

Myosis
Blepharospasm
Epiphora
± Swelling

Question 15

List 3 ways to assess integrity of epithelium in eye

Answer 15

Fluorescein- most used
Rose Bengal/Lissamine Green
Seidle test

Question 16

List 5 things that are routinely done when assessing eyes in first opinion practice

Answer 16

Naked eye examination
Nerve blocks
Fluoroscein/ Rose Bengal dye
Focal light source
Direct ophthalmoscopy

Question 17

what is the corpora nigra

Answer 17

the black pigmentation at the edge of the irsis in the equine and ruminant eye

Question 18

what is blepharopasm

Answer 18

blinking or other eyelid movements, like twitching, that you can’t control

Question 19

Decsribe the palpebral reflex

Answer 19

diagnostic test in which the eye should blink in response to touch to the medial canthus of the eye

Question 20

Describe the corneal reeflex

Answer 20

blinking in response to corneal stimulation by a cotton wisp

Question 21

describe indirect PLR

Answer 21

pupil in the contralateral eye constricts in response to light shining in the other eye

Question 22

do you need sedation to do an equine ophthalmic exam

Answer 22

yes - alpha 2’s and butorphanol is a common combination given

Question 23

what does the supraorbital nerve block block

Answer 23

sensory feeling to the upper eyelid

Question 24

what is aqueous flare

Answer 24

turbidity of the aqueous humor caused by increase protein levels and cells - sign of uveitis

Question 25

why should we not use atropine for a clinical exam

Answer 25

this can last up to 2 weeks and mean the horse will be sensitive to light for a while