Week 1 - Equine Opthamology: Corneal Disease

Question 1

What is corneal ulceration in horses likely related to?

Answer 1

• Generally traumatic in origin
• Usually infected
• often associated with secondary changes

Question 2

How might a corneal ulcer present?

Answer 2

• Blepharospasm
• Epiphora
• Reddened conjunctiva
• Corneal oedema
• Swollen eyelids

Question 3

Give 5 ways you might diagnose a corneal ulcer

Answer 3

• Sedation…anaesthetics…nerve blocks
• Fluorescein dye
• Rose bengal dye
• Cytology
• Culture

Question 4

What is an auriculopalpebral nerve block?

Answer 4

Motor nerve block (facial n. VII) to the orbicularis
oculi muscle.
* Prevents closure of the eyelids.
* Usually the only block necessary for diagnostic
evaluation of the eye

Question 5

Where is the auriculopalpebral nerve block located?

Answer 5

Nerve palpated along the dorsal edge of the
zygomatic arch, just anterior to its highest point.
* 23G 1inch needle
* 1-2mL local anaesthetic (Lidocaine or mepivacaine).

Question 6

What are the treatment aims for corneal ulceration?

Answer 6

• address any underlying causes
• treat or prevent infection
• slow the breakdown/ dissolution of corneal collagen
• address secondary uveitis
• provide structural support
• analgesia

Question 7

What antimicrobials would you use to help treat corneal ulcers?

Answer 7

• Antimicrobials: Topical (q2-4hrs)
• Antibacterial: Chloramphenicol, Gentamicin, ciprofloxacin)
• Antifungal: Enilconazole, voriconazole

Question 8

What medication might you use to slow the breakdown of corneal collagen?

Answer 8

• Proteinase inhibitors: Topical
• Serum
• EDTA solution

Question 9

What medication would you use to treat secondary uveitis?

Answer 9

Atropine topical q24h

Question 10

What analgesics would you use for corneal ulcers?

Answer 10

Anti-inflammatories: Systemic
* NSAIDS usually Flunixin 1.1mg/kg iv initially then oral

Question 11

What is a subpalpebral lavage?

Answer 11

Not difficult to place.
* Simplify treatment.
* Painful eyes are hard to treat.
* Easy for vet to demonstrate medicating eye when have
sedated horse and used AP nerve block!
* Place in lower eyelid as less likely to slip and further damage
cornea

Question 12

What is a grid keratotomy?

Answer 12

• Scratch surface of cornea.
• Stimulates healing.

Question 13

What is the Diamond Burr Treatment?

Answer 13

• Debrides surface of cornea.
• Stimulates healing.
• May need repeated treatments.

Question 14

What is Tarsorrhaphy?

Answer 14

Stops blinking which may
disrupt early healing.
* Administer tx via SPL.
* Only perform once stable.
* Keep in place for ~1week.

Question 15

What is a conjunctival pedicle flap?

Answer 15

Suture portion of conjunctiva over
the defect under GA.
* Leave for 2weeks.
* Protects site.
* Improves blood flow
* Can cause scarring and blind spot.

Question 16

What is an ammnion graft/ patch?

Answer 16

Piece of amniotic membrane to
repair defect.
* Usually under GA.
* Proteinase inhibiting properties
* Antifibrotic properties

Question 17

What condition is associated with non-healing ulcers?

Answer 17

PPID may be associated with poor ulcer healing:
* Total serum cortisol may be normal but may have
elevations in cortisol in tear film.

Question 18

What is immune mediated keratitis?

Answer 18

• Primary clinical feature is the absence of anterior uveitis in the presence of keratitis.
• Typically unilateral.
• Corneal oedema, cellular infiltration and vascularisation
• Absence of profound ocular pain.

Question 19

What are the three categories of immune mediated keratitis?

Answer 19

• Superficial IMMK
• Mid-Stromal IMMK
• Endothelial IMMK

Question 20

How might you diagnose immune mediated keratitis?

Answer 20

Based on clinical presentation and exclusion of DDx

Question 21

What are the potential treatments for IMMK?

Answer 21

Glucocorticoids
* Dexamethasone/Polymixin B/Neomycin (Maxitrol)
* Prednisolone (PredForte) TID/QID
* NSAIDs
* Used when GCs contraindicated.
* Immunosuppressive agents
* Cyclosporin (Optimmune) BID

Question 22

How does eosinophillic keratitis usually present?

Answer 22

• Often bilateral.
• Seasonal occurrence: increased incidence in summer and autumn.
• Signs of ocular pain: blepharospasm, epiphora and conjunctival
  hyperaemia.

Question 23

what is localised non-progressive eosinophilic keratitis?

Answer 23

• Minimal corneal involvement or ocular pain.
• Small, white plaque sometimes seen.

Question 24

What is progressive/ Extensive eosinophillic keratitis?

Answer 24

• Marked ocular pain.
• Extensive corneal lesions.
• White plaque formation and secondar infectious ulceration.

Question 25

What is superficial/ multifocal eosinophilic keratitis?

Answer 25

• Rare.
• Multiple caseous yellow foci spread over the corneal surface.
• Moderate to severe corneal oedema.

Question 26

How might you treat eosinophillic keratitis?

Answer 26

Glucocorticoids
* Dexamethasone/Polymixin B/Neomycin (Maxitrol)
* Prednisolone (PredForte) TID/QID
* (NB use with care if secondary bacterial ulceration)
* Immunosuppressive agents
* Cyclosporin (Optimmune) BID
* Antihistamines
* Oral cetirizine (0.4mg/kg BID)
* Superficial keratectomy to remove plaques and/or inflammatory debris.

Question 27

What causes tear-deficient keratopathies?

Answer 27

• Keratoconjunctivitis sicca.
• Deficiency of aqueous portion of tear film- vestibular disease, stylohyoid fx, head trauma.
• Evaporative dry eye.
• Enhanced evaporative loss- eyelid abnormalities and/or reduced blinking (Facial nerve paralysis)

Question 28

What is the clinical presentation of tear-deficient keratopathy?

Answer 28

Blepharospasm
* Mucopurulent discharge
* Dull cornea.

Question 29

How might you diagnose tear-deficient keratopathies?

Answer 29

Schirmer tear test <10mm/min
* Fluorescein/rose Bengal dye.