Equine and farm ophthalmology Flashcards
What is different about the shape of equine eyes
Oval globe, corneal and pupil
Corpora nigra function
Unclear - could relate ti shading eye from light from above
What is different about the blood vessels in the equine fundus
Fundus is ‘paurangiotic’
- Blood vessels only spread away from optic disc ~an optic disc diameter; so see pink oval
What are stars of Winslow
Choroidal vessels coming through tapetum to take blood to choriocapilaris
Things to remember with using atropine in the horse
Need lots to cause dilation
Risk of colic; so should auscultate the abdomen at the same time
What is a habrenema granuloma
When flies uptake gut worm larvae and land on eyes
What could we use to treat periocular sarcoids
Excision, cryo, heavy metal injfection, BCG injection to stimulate immune response
In which type of horse do we see congenital cataracts
In Morgan horse
= dominant
What is mucupurulent discharge a sign of in young vs old horses
Young; inperforate nasolacrimal punta
Old; squamous cell carcinoma
How could we treat an ocular squamous cell carcinoma
Excision, radiotherapy using strontium 90, cryo, 5-fluorourical, mitomycin
What can cause equine recurrent uveitis
Main one is leptospira
Ochocerca
Brucella
toxoplasma
(or idiopathic)
Treatment for equine recurrent uveitis
Topical atropine, steroids, surgery to remove fibrin and breakdown synechiae
Can inject plasminogen activating factor into eye
What signs on a prepurchase exam could indicate horse has suffered from equine recurrent uveitis and may be at risk again
Synechiae between iris and lens
Anterior cataract
Butterfly lesion around optic disc may be related
What is aniridia
Virtually no iris due to defect in corneal stem cell population; probably related to pax-6 homeo
Which horses might we see melanoma in the eye of
Grey
When might we see iris hypoplasia
in colour filute equids
his iris can billow forward due to aqueous pressure and look like an iris cyst
Is glaucoma common in horses and what might cause it
No not common
Could occur secondary to uveitis or a tumour
What can be normal in an equine fundus but may look worrying
Nibbles out of the fundus that looks like colobomas
If we see a dot in the lens during equine vetting which areas are likely to develop into cataract and which aren’t
If in nucleus or epithelium; probably won’t cause an issue
If in the stroma, more likely to cause an issue as it can grow as the lens grows
Proliferative vs exudative optic neuropathy
Proliferative: see slowly growing white mass on the optic disc; doesn’t affect vision
Exudative: similar sign but due to disc swelling from optic neuritis and will lead to blindness
What is the cause of infectious bovine keratoconjunctivitis (New forest eye)
Moraxella bovis
- Piliated form (pilli can attach to corneal surface)
Mycoplasma coinfection may be involved
Treatment for new forest eye
Long acting antibiotics either subconjunctival (painful)
or IM
What signs do we see with silage eye (listeriosis)
Corneal oedema
Uveitis (because bacteria go deep)
What might anophthalmos be assocaited with
Vit A deficiency in utero
May also see caudal spinal defects
Which type of cows do we see a squint in (esotropia)
Kerry blue
What does it mean about aetiology of a cataract if it is found in nucleus
It has had it since in utero
Which cattle breed is optic disc coloboma inherited in
Charolais
Which cattle breed gets corneal oedema due to endothelial degeneration
Kerry blue
What can cause periocular hair colour changes (cattle)
Copper toxicity
Which cattle breeds are predisposed to squamous cell carcinoma
Those with depigmented periocular regions e.g Hereford and Hereford crosses
How does lymphoma in the eye of cattle with BLV present
Orbital tumour with gradual exophthalmos
Which sheep type do we see eyelid coloboma and where
Jacob sheep
Middle of lid
What is bright blindness
Bracken asscaited retinal degeneration in sheep
Due to toxic agent Ptaquiloside (can also cause anaemia)
Signs of infectious bovine keratoconjunctivitis
Conjunctival hyperaemia
Corneal ulceration; can lead to perforation
