ocular disease in cattle

Question 1

How far back should cattle eyes be easily retropulsed

Answer 1

5cm

Question 2

What cranial nerves does the palpebral reflex test and when might it be absent

Answer 2

Sensation: trigeminal nerve CNV
Motor: facial nerve CN VII

May be absent in first 2 weeks of life; acquired reflex

Question 3

What metabolic change can cause a sluggish palpebral reflex

Answer 3

Elevated D lactate (e.g with acidosis due to diarrhoea)

Question 4

What cranial nerve does the menace reflex ecamine

Answer 4

CNII optic nerve and retina
+ motor from facial nerve (VII)

Question 5

What solution to use to flush eye

Answer 5

5-10% povidine iodine in sterile saline
(recommendation is up to 20%)

Question 6

What can happen if LA is accidentally injected into a vessle e.g while doing retrobulbar injections

Answer 6

Respiratory collapse and sudden death

Question 7

What nerve block is used for eyelid akinesia

Answer 7

Auricular nerve block

Question 8

What does a successful retrobulbar nerve block give

Answer 8

Mydriasis
Lack of globe motility (paralysis of extra ocular muscles)
No corneal reflex

Question 9

What do we need to remember to do having done nerve blocks on the eye

Answer 9

Lubricate eye with ointment since block stops blinking

Also should use local anaesthetic infiltration of eyelid if we want to block sensation to this

Question 10

What is orbit exteneration compared to enucleation

Answer 10

In exteneration remove the tissues around the eye as well as the eye

Do enucleation if no infectino

Question 11

When would a orbit extenteration be especially indicated

Answer 11

With invasive squamous cell carcinoma behind the eye

Question 12

What causes might be implicated in microphthalmia

Answer 12

In utero BVD infection
Toxic causes
Genetic; Guernsey, Holstein + related to cardiac and tail abnormalities

Question 13

What does the individuals we see congenital cataracts in tell us about the cause

Answer 13

If in a group of age matched animals suggests a gestational accident e.g toxicity, deficiency (A, E, Se), BVD infection
If calves from same genetic line, suggests genetic e.g in Jersey

Question 14

Dealing with dermoids

Answer 14

Do surgery to excise; if on the cornea do keratectomy
Topical antibiotic and atropine given for week

Question 15

Cause of orbital cellulitis

Answer 15

Invasion of orbital soft tissue by opportunistic bacteria after puncture wounds or laceration in the area

Question 16

What to do if exophthalmos from orbital cellulitis doesnt stop after 24 hours

Answer 16

DO a temporary tarsorrhaphy to protect the eye

Question 17

Treating orbital cellulitis

Answer 17

Systemic broad spectrum antibiotics for 2 weeks
NSAIDs
Eye massage with gentle retropulsion
Tobical lubricants
Atropine if corneal ulceration

Question 18

Which cattle are predisposed to new forest disease (infectious bovine keratoconjunctivitis)

Answer 18

Young cattle
Herefords esp i.e ones with less periocular pigmentation

Question 19

Cause of infectious bovine keratoconjunctivitis (New Forest disease)

Answer 19

= moraxella bovis
Transmission mediated by flies

Question 20

What things are risk factors for infectious bovine keratoconjunctivitis

Answer 20

Flies
UV light (so to manage can confine animal to avoid UV light)
Trauma/irritation of cornea
Anythings that increased ocular and nasal discharge and so facilitates spread e.g mycoplasma, IBR virus

Question 21

Can we vaccinate for moraxella bovis

Answer 21

No not in the UK

Question 22

Cause of silage eye = bovine iritis

Answer 22

Listeria monocytogenes
In stressed cattle fed improperly prepared big bale silage

Question 23

When do we not want to use steroids in cases of eye issues and when might we

Answer 23

Don’t use in cases of ulceration as will impair immune syste

Do use in silage eye; topical dexamethosone to relieve uveitis

Question 24

Clinical signs of silage eye

Answer 24

Epiphora, conjunctivitis, blepharospams

Progresses to NON-ULCERATIVE keratitis with marked corneal odema, uveitis

Question 25

What is a primary neoplasm of the eye in cattle and which breeds do we see it in

Answer 25

Ocular squamous cell carcinoma
= malignant
Seen in cattle with unpigmented skin on their face e.g herefords, holstein freisan, simmental

Question 26

Stages in development of ocular squamous cell carcinoma

Answer 26

Stage 1 = plaques
2 = keratomas; mainly on lower eyelid
3 = papilllomas
4 = carcinomas; more irregular and nodulat

Question 27

Distribution of squamous cell carcinomas on eye and malignancy

Answer 27

Most on limbus 75%
15% on eyelids
10% on thrid eyelid

Those on third and lower lid are more aggressive and more likely to metastasize

Question 28

What does ammonia or chlorine bleach contact with the eye cause

Answer 28

Severe and permanent corneal opacity due to epithelial necrosis and stromal injury (get stromal scarring)