Common Ocular Conditions in Horses

Question 1

What should be done with eyelid lacerations?

Answer 1

• Surgical repair
  (lower + lateral = best)

Question 2

What are masses of eyelids? Tx?

Answer 2

• Melanoma
• SCC of third eyelid
• Lymphoma
• Tx = removal / reconstructive surgeries

Question 3

What are clinical signs of ulcerative keratitis / corneal ulcers?

Answer 3

• Pain
• Blepharospasm
• Epiphora
• Photophobia

Question 4

What is treatment of corneal ulcers?

Answer 4

• Fluorescein + flush with saline to assess damage
• Superficial ulcers = heal w no complications = topical antimicrobial +/- topical atropine (no scar)
• Deeper ulcer = same for non-complicated, but longer time + scarring

Question 5

What is keratomalacia? What should be done?

Answer 5

• Keratomalacia = melting ulcer
• Activation +/or production of proteolytic enzymes by =
  -corneal epithelial cells
  -Leucocytes
  -Microbial organisms (Pseudomonas)
• Tx = early + aggressive =
  -topical Serum
  -topical EDTA
  -topical acetylcysteine
  -topical tetracycline / doxycycline
  -systemic NSAIDs (flunixin)

Question 6

What is a descemetocele? What should be done?

Answer 6

• Ulcer extending all the way to the decemet’s membrane = fluorescein neagtive
• Tx = aggressive therapy, may need surgical tx
  -conjunctival flap

Question 7

What can occur with full thickness corneal laceration?

Answer 7

• Iris prolapse

Question 8

What should be done with stromal abscesses?

Answer 8

• Medical therapy = AB
• Surgery = debridement / corneal grafting techniques

Question 9

What causes viral keratitis? Tx?

Answer 9

• EHV 2
• Tx = topical idoxuridie, trifluorothymidine, aciclovir, interferon gamma, cortiosteroid

Question 10

What is treatment of fungal keratitis?

Answer 10

• Slow to resolve
• Surgery = keratectomy +/- conjunctival flap
• Topical miconazole/itraconazole, amphoctericin B, VORICONAZOLE

Question 11

What is seen with immune mediated keratopathies?
Treatment?

Answer 11

• Usually unilateral
• Slight ocular discomfort
• Vary from Irregular corneal surface to deep bullae formation, vascularisation + oedema
• Tx = medical = topical steroid, cyclosporine A / doxycycline
  -Surgical = keratectomy, cyclosporine A implant

Question 12

What is uveitis? What can it lead to?

Answer 12

• Inflammation of uvea (iris, ciliary body + choroid)
• Can lead to blindness if untreated

Question 13

What can uveitis be secondary to?

Answer 13

• Eye ulcer
• Rhodococcus
• Immune mediated
• Leptospira spp

Question 14

What are clinical signs of anterior uveitis?

Answer 14

• Pain - blepharospasm + epiphora
• Chemosis - red eye
• Constricted pupil
• Aqueous flare = milky appearance of anterior chamber
• Blood (hyphaema), pus (hypopyon), or fibrin in anterior chamber

Question 15

What are clinical signs of posterior uveitis?

Answer 15

• Subtle
• Variable pain - often mild
• Vitritis
• Retinal changes

Question 16

What is treatment of uveitis?

Answer 16

• Topical corticosteroid (if no ulcer)
• Topical NSAID (if ulcer)
• Topical AB
• Topical atropine (c/4h until pupil dilates)
• Systemic NSAID = Flunixin
• Surgery =
  -suprachoroidal cyclosporine A implant
  -Pars plana vitrectomy
  -Enucleation

Question 17

What are long term complications of Uveitis?

Answer 17

• Atrophy granula iridica
• Synechiae
• Cataracts
• Glaucoma
• Retinal pathology
• Blindness
• Phthisis bulbi

Question 18

What can cause cataracts?

Answer 18

• Acquired / secondary cataracts =
  -uveitis
  -trauma
  -tumour
• Developmental opacities, including congenital cataracts

Question 19

How would you examine the lens in horses?

Answer 19

• Retroillumination - light reflected from tapetum w focal light source at arm’s length (opacities appear dark)
• Direct focal illumination (transillumination) = direct beam light at 45o angle into lens (cataracts = white)

Question 20

What are different types of cataracts?

Answer 20

• Capsular cataract
• Nuclear cataract
• Perinuclear (lamelar) cataract
• Equatorial cataract
• Sutural cataract
• Complete cataract

Question 21

How are cataracts treated?

Answer 21

• Most do not require treatment - or treat primary cause if secondary
• Surgery in young foals (<4m/o) - phacoemulsification

Question 22

What is normal intraocular pressure?

Answer 22

• 15-30mmHG

Question 23

What are signs of glaucoma?

Answer 23

• Hydrophthalmos / buphthalmos
• Corneal oedema
• Corneal striae
• Lens luxation
• Blindness

Question 24

How is Glaucoma diagnosed?

Answer 24

• Signs
• Tonometry
• Ultrasound

Question 25

What is treatment of glaucoma?

Answer 25

• Carbonic anhydrase inhibitors
• Beta-blockers - timolol
• Anti-inflammatories (NSAIDs +/or steroids)
• NOT prostaglandin derivatives in horses
• Surgical =
  -laser destruction of ciliary body
  -aqueous shunts
  -enucleation
• Chemical ciliary body destruction

Question 26

On histology what colour are different layers of the eye?

Answer 26

– Neurosensory retina = cling film
– Retinal Pigmented Epithelium = black
– Tapetum = blue, green, amber…
– Choroid = red
– Sclera = white