Common equine ocular conditions

Question 1

How does an eyelid laceration prognosis vary with location?

Answer 1

Lower better (upper affects tear film distribution)
Lateral better (tear ducts at medial canthus)
LL

Question 2

Eyelid lacerations heal well due to being very vascular. What should you use to clean the wound?

Answer 2

Iodine

Never chlorhexidine - topic to cornea

Question 3

What is the most common eyelid tumours of the horse?

Answer 3

Sarcoid
SCC
Lymphoma
melanoma

Question 4

Ulcerative keratitis is very common in horses and causes pain, blepharospasm, epiphora and photophobia. What is the treatment for superficial ulcers?

Answer 4

Topical antimicrobial

+/- topical atropine

Question 5

What is the treatment for a deeper ulcer seen with superficial keratitis?

Answer 5

Antimicrobials
+/- topical atropine
(Same as superficial ulcer but longer time period - scarring likely)

Question 6

What is keratomalacia?

Answer 6

Melting ulcer (with Pseudomonas)
Complication of deep ulcer

Question 7

What is the treatment for keratomalacia?

Answer 7

Topical serum 
EDTA
Acetylcysteine (artificial tears)
Topical anti-microbials - tetracycline, doxycycline
SYSTEMIC NSAIDs - flunixin

Question 8

How are desmetoceles treated?

Answer 8

Surgery (conjunctival flap)

Question 9

Full thickness corneal lacerations cause what to prolapse. The prolapse is good, but what is a negative prognostic factor?

Answer 9

Iris prolapse

Blood in anterior chamber (hyphaema)

Question 10

Stromal abscesses show up fluorescein negative. How are they treated?

Answer 10

Medical therapy: chloramphenicol (gentamicin useless as hydrophilic!)
May require surgical debridement/corneal graft

Question 11

What is the possible cause of viral keratitis?

Answer 11

EHV-1

Question 12

How does viral keratitis (EHV-1) present?

Answer 12

Multiple superficial white opacities

Painful

Question 13

Viral keratitis (EHV-1) is difficult to diagnose. How may it be diagnosed?

Answer 13

Virus isolation

PCR

Question 14

What is the treatment for viral keratitis?

Answer 14

Topical antivirals (aciclovir, idoxuridine, trifluorothymidine)
Topical interferon gamma

Question 15

Fungal keratitis is rare in the UK. What are the risk factors for this condition in the USA?

Answer 15

Hot, humid states

Previous antibacterial or corticosteroid administration

Question 16

Fungal keratitis may initially be fluorescein negative. How is it diagnosed?

Answer 16

Rose bengal positive

Culture/cytology essential - visible hyphae

Question 17

How is fungal keratitis treated?

Answer 17

Topical antifungals

May need surgery - keratectomy +/- conjunctival flap

Question 18

Immune mediated keratopathies are usually insidious onset. Are they uni or bilateral?

Answer 18

Unilateral

Question 19

What is the treatment for immune-mediated keratopathies?

Answer 19

Medical immunosuppression: cyclosporin, corticosteroids, doxycycline
Surgery: ciclosporin A implant, keratotomy

Question 20

Uveitis is very common in horses. What 3 structures make up the uvea?

Answer 20

Iris
Choroid
Ciliary body

Question 21

Uveitis can be primary or secondary. There is a strong immune mediated component. Give an example of a secondary condition that can cause uveitis

Answer 21

Rhodococcus

Question 22

Recurrence of uveitis is likely. What are the long term complications of uveitis?

Answer 22

Atrophy of corpora nigra/granula iridica
Synechia (iris adheres to cornea or lens)
Cataracts
Glaucoma
Retinal pathology, blindness
Pthisis bulbs - shrunken non-functional eye

Question 23

A horse presents with blepharospasm, pain, epiphora, chemises, constricted pupils and aqueous flare. There is also some hyphaema and hypopyon. What is your diagnosis?

Answer 23

Anterior uveitis

Question 24

Posterior uveitis causes subtle clinical signs and is often diagnosed late in the disease cause. What may be seen?

Answer 24

Vitritis

Retinal changes

Question 25

How can uveitis be treated in horses? How long for?

Answer 25

Topical: Corticosteroids (if no ulcer!), NSAIDs, antimicrobial, atropine
Systemic flunixin
Surgery ciclosporin, enucleation, injection gentamicin into eye (destroys ciliary body)

Question 26

Why should you be careful when giving horses topical atropine?

Answer 26

Risk of colic

Question 27

Why might a horse have a subchoroidal ciclosporin A implant?

Answer 27

Uveitis

Immune mediated keratopathies

Question 28

Cataracts are any opacities in the lens. They are common in horses. They can be acquired/ secondary or developmental. Give examples of each

Answer 28

Acquired/secondary: uveitis, trauma, tumour

Developmental: congenital

Question 29

How do opacities appear on retroillumination? What about transillumination?

Answer 29

Retroillumination - dark

Transillumination - appear white

Question 30

What is the treatment for cataracts?

Answer 30

Most don’t require treatment
Aspirin
Phacoemulsification surgery

Question 31

Can all horses with cataracts have phacoemulsification surgery?

Answer 31

Mainly young foals <4 months

Contraindicated if uveitis

Question 32

Glaucoma is relatively uncommon in horses. What is the normal intraocular pressure of a horse?

Answer 32

15-30mm/Hg

Question 33

What are the symptoms of glaucoma?

Answer 33

Buphthalmos (enlarged eye)
Corneal oedema
Corneal striations
Lens luxation
Blindness

Question 34

What is the medical treatment for equine glaucoma (rarely used as often too late by presentation?

Answer 34

Carbonic anhydrase inhibitors - ending -amide
Topical beta blockers - timolol
Anti-inflammatories - topical or systemic
PROSTAGLANDIN ANALOGUES CONTRAINDICATED

Question 35

What surgery can be used to treat glaucoma?

Answer 35

Laser destruction of ciliary body (or chemical - gentamicin)
Aqueous shunts
Enucleation

Question 36

What does a normal equine optic nerve look like?

Answer 36

Oval shaped (rounder in foals)
Salmon pink
3-5mm vertical, 5-8mm horizontal

Question 37

What is the Star of Winslow?

Answer 37

Avascular area of retina