Ophthalmology

Question 1

Describe the anatomy of the ruminant eye

Answer 1

Complete bony orbital rim, monocular vision, cornea is elongated horizontally, pupil is oval in horizontal plane

Question 2

Describe an auriculopalpebral nerve block

Answer 2

Motor block (no anesthesia), use 1-2% lidocaine 5-7cm caudal to zygomatic process where nerve crosses zygomatic arch

Question 3

What are the congenital diseases of the orbit?

Answer 3

Anophthalmia, microphthalmia, cyclopia (sheep)

Question 4

Describe microphthalmia

Answer 4

Often combined with other defects, unilateral or bilateral, can be caused by teratogen exposure (selenium/sulfate in sheep) viral disease (blue tongue- sheep, BVDV- cattle), is heritable in Guernseys, Herefords, and Shorthorns

Question 5

What causes cyclopia in sheep?

Answer 5

Maternal ingestion of veratum californicum at day 14 in utero

Question 6

What are causes of exophthalmos in ruminants?

Answer 6

Retrobulbar mass (infection or LSA), glaucoma

Question 7

How are retrobulbar masses treated?

Answer 7

Euthanasia or debulk mass and treat underlying infection

Question 8

Which ruminants are predisposed to entropion?

Answer 8

Sheep

Question 9

How is entropion treated?

Answer 9

Temporary tacking, injectable solutions, Holtz-Celsus procedure

Question 10

What is a corneal dermoid?

Answer 10

Benign congenital tumor of haired skin on the cornea, relatively rare, most common in Herefords

Question 11

Describe the etiology of infectious bovine keratoconjunctivitis

Answer 11

Moraxella bovis (gram negative bacillus) adheres to corneal surface with capsular pili, moraxella ovis and boviculi invade secondarily

Question 12

How is infectious bovine keratoconjunctivitis transmitted

Answer 12

Introduction of new animal, face flies spread infection, may occur with concurrent infections, predisposed by UV light and non-pigmented skin around the eyes

Question 13

What are the clinical signs of infectious bovine keratoconjunctivitis?

Answer 13

Central corneal ulcer with edema, cellular infiltrate, vascularization, perforation, fibrosis, conjunctivitis, epiphora, blepharospasm, mucopurulent discharge, photophobia, miosis

Question 14

How is infectious bovine keratoconjunctivitis diagnosed?

Answer 14

Clinical signs, can swab and culture

Question 15

How is infectious bovine keratoconjunctivitis treated?

Answer 15

Oxytetracycline or tulathromycin, subconjunctival injections of penicillin, protect cornea with temporary tarsorrhaphy

Question 16

What is the treatment for IBK if corneal perforation occured?

Answer 16

Enucleation

Question 17

How is infectious bovine keratoconjunctivitis prevented?

Answer 17

Fly control, segregate affected animals, decrease eye irritation, provide shade, vaccine available (questionable)

Question 18

What is infectious keratoconjunctivitis called in goats and sheep?

Answer 18

Pink eye, heather blindness, blight

Question 19

What are the bacterial agents that infect infectious keratoconjunctivitis in goats and sheep?

Answer 19

Chlamydophila spp., Mycoplasma spp.

Question 20

How is infectious keratoconjunctivitis treated in goats and sheep?

Answer 20

Oxytetracycline (systemic or topical)

Question 21

What is the causative agent of malignant catarrhal fever?

Answer 21

Ovine herpesvirus 2

Question 22

What are the clinical signs of malignant catarrhal fever?

Answer 22

Severe vasculitis (hematuria, peripheral corneal edema, bloody diarrhea, oral ulcers), fever, lymphadenopathy, respiratory disease, death

Question 23

What type of cancer do ruminants get in their eye?

Answer 23

Squamous cell carcinoma

Question 24

What are the predisposing factors for SCC of the eye?

Answer 24

Age, increased hours of sunlight, decreased pigmentation around the eye

Question 25

What are the clinical signs of eye SCC?

Answer 25

Bulbar conjunctiva and cornea usually affected, progresses with small white to pink mass that becomes necrotic and irregular

Question 26

What is a precursor to carcinoma of eyelids?

Answer 26

Keratosis

Question 27

Describe the neoplastic behavior of eye SCC

Answer 27

Locally aggressive, metastasize later in disease to orbital bones, maxilla, submandibular LNs, liver, lungs, pleura, kidneys, LNs

Question 28

How is eye neoplasia diagnosed?

Answer 28

Clinical signs, biopsy and histopathology (not usually necessary)

Question 29

How is eye neoplasia treated?

Answer 29

Curative or debulking surgery, enucleation if in multiple locations within eye, salvage if metastasized

Question 30

Describe the four point block

Answer 30

Curved 3in spinal needle inserted through lids at dorsomedial, ventromedial, ventrolateral, and dorsolateral aspects of the eye, 10mL lidocaine injected at each location

Question 31

Describe the Peterson nerve block

Answer 31

10-15mLs 2% lidocaine injected at the notch between zygomatic arch and supraorbital, numbs CNs II, III, IV, V, VI, can cause death

Question 32

Describe removal of the third eyelid

Answer 32

Has minimal impact on tear production
Perform local anesthesia or four-point block, grasp lid with hemostats to expose base, clamp with large curved hemostats, remove lid with mayo scissors

Question 33

What are indications for enucleation?

Answer 33

Extensive SCC, trauma, ruptured cornea due to pinkeye

Question 34

Describe exenteration

Answer 34

Block the eye, close the lids, dissect intraocular muscles, clamp and ligate optic nerve and vessels or cut and suture lids closed as quickly as possible (simple interrupted, 1 layer closure), apply pressure bandage for 24 hours, antibiotics for 3-5 days, NSAIDs for 2-3 days, remove sutures in 2 weeks, control flies

Question 35

What is hypopyon associated with?

Answer 35

Sepsis and FPT in calves