Equine Ophthalmology

Question 1

Due to lateral placement of the eyes, horses have a total horizontal visual field of ____ degrees.

Answer 1

350 degrees

Question 2

Horses have a binocular visual field of ____ degrees.

Answer 2

60 degrees

Question 3

What type of retina does the horse have?

Answer 3

Paurangiotic

Question 4

What is unique about the euqine pupil?

Answer 4

Corpora nigra

Question 5

True or False: Fluorescein staining should be performed for every horse eye exam.

Answer 5

TRUE

Question 6

Describe a positive Jones test.

Answer 6

Fluorescent stain at the nares

Question 7

What is the normal IOP in a horse?

Answer 7

15 - 30 mmHg

Question 8

In the horse, a high IOP is suggestive of what?

Answer 8

Glaucoma

Question 9

In the horse, a low IOP is suggestive of what?

Answer 9

Uveitis

Question 10

Tonometry (checking IOP) should be checked at or above the level of what?

Answer 10

Heart

Question 11

Which of the following periocular nerves are sensory: auriculopalpebral, frontal/supraorbital, infratrochlear, lacrimal, zygomatic.

Answer 11

1. Frontal/supraorbital
2. Infratrochlear
3. Lacrimal
4. Zygomatic

Question 12

Which of the following periocular nerves are motor: auriculopalpebral, frontal/supraorbital, infratrochlear, lacrimal, zygomatic.

Answer 12

1. Auriculopalpebral

2. Frontal/supraorbital

Question 13

What is the most common equine eye/adnexal tumor?

Answer 13

Squamous cell carcinoma

Question 14

What are the 4 locations of SCC in the horse eye?

Answer 14

1. Eyelids
2. Conjunctiva
3. 3rd eyelid
4. Cornea

Question 15

What are 2 predisposing factors for SCC in the horse?

Answer 15

1. Lack of periocular pigment

2. Ultraviolet radiation

Question 16

How would SCC present?

Answer 16

1. Initially hyperemia
2. Progresses to ulceration
3. Then to papillomatous and fleshy masses

Question 17

How might you treat SCC in the horse?

Answer 17

Surgical excision: Cryotherapy, CO2 laser, radiofrequency hyperthermia, brachytherapy, chemotherapy, immunotherapy

Question 18

Which types of SCC tumors are most associated with recurrence?

Answer 18

1. Eyelid

2. Third eyelid

Question 19

Describe the therapeutic options for a simple corneal ulcer in a horse.

Answer 19

1. Topical broad spectrum antibiotics (TID - BID)
2. Atropine (SID - BID)
3. Systemic anti-inflammatories (Flunixin meglumine, phenylbutazone)

Question 20

After starting therapy for a simple corneal ulcer, when should you recheck that eye?

Answer 20

Within 3 - 5 days

Question 21

Describe the therapeutic options for a complicated corneal ulcer in a horse.

Answer 21

1. Topical antibiotics (every 1-2 hours)
2. Oral NSAIDs (BID): Flunixin meglumine, Phenylbutazone
3. Atropine (BID)

Question 22

How often would you need to administer antifungal medications for a complicated mycotic-infected corneal ulcer?

Answer 22

Every 2 - 6 hours

Question 23

What are your antiproteinase/anticollagenase options for treating a complicated corneal ulcer in a horse?

Answer 23

1. Serum / plasma
2. EDTA
3. Galardin
4. N-acetylcysteine

Question 24

How often would you need to administer an anti-proteinase for a complicated ulcer?

Answer 24

Every 1 - 2 hours

Question 25

For a complicated ulcer, when would your recheck need to be?

Answer 25

Within 48 hours (weekly thereafter if improving)

Question 26

What is a corneal stromal abscess?

Answer 26

Where an infected ulcer has epithelialized and infectious agents are trapped within the cornea

Question 27

What is the clinical appearance of a corneal stromal abscess?

Answer 27

1. Painfull 2. Corneal vascularization 3. Corneal edema 4. Fluorescein negative

Question 28

True or False: It is acceptable to use steroids with a corneal stromal abscess.

Answer 28

FALSE

Question 29

How would you medical manage/treat a corneal stromal abscess?

Answer 29

1. Antimicrobials (ofloxacin, voriconazole every 3 - 6 hours; fluconazole systemically if vascularized) Reflex uveitis treatment: 2. Atropine (BID - QID) 3. Banamine (BID) +/- prophylactic doses of omeprazole 4. Surgery (conjunctival graft, corneoconjunctival transposition, corneal transplant, keratoplasty)

Question 30

What is the most common cause of equine blindness?

Answer 30

Uveitis

Question 31

What are the clinical signs of uveitis in the horse?

Answer 31

1. Pain (blepharospasm, epiphora, photophobia) 2. Conjunctival hyperemia 3. Corneal changes (edema) 4. Aqueous flare, hypopyon, hyphema, fibrin 5. Miosis 6. Low IOP

Question 32

What infectious agent is uveitis most commonly associated with in the horse?

Answer 32

Leptospira interrogans

Question 33

Which horse breeds are predisposed to equine recurrent uveitis?

Answer 33

1. Appaloosa | 2. Draft breeds

Question 34

Is equine recurrent uveitis a unilateral or bilateral condition?

Answer 34

Unilateral OR bilateral

Question 35

What are the 5 complications associated with ERU?

Answer 35

1. Calcified band keratopathy 2. Blinding cataracts 3. Retinal detachment 4. Secondary glaucoma 5. Vitreal floaters

Question 36

What are your treatment options for ERU?

Answer 36

1. Topical anti-inflammatories 2. Atropine 3. Systemic antibiotics 4 Surgery (vitrectomy, suprachoroidal cyclosporine implant)

Question 37

Describe the prognosis associated with ERU.

Answer 37

Poor long-term