Ophthamologic disease in marine mammals

Question 1

T/F: Cetaceans lack a nasolacrimal system

Answer 1

true

Question 2

What are the 5 layers of the cornea?

Answer 2

epithelium, Bowen’s layer, corneal stroma, Descement’s membrane, endotherlium

Question 3

Which cetacean is the only species to NOT have a Bowman’s layer

Answer 3

Pygmy sperm whale (Kogia breviceps)

Question 4

Which component of the tear film is most copious is cetaceans?

Answer 4

mucus layer

Question 5

Which component of the tear film do cetaceans lack?

Answer 5

lipid layer (they don’t have meibomian glands)

Question 6

Which type of keratopathy is the most common in cetaceans (~50% of cases)? What is the primary cause?

Answer 6

(1) Medial keratopathy

(2) UV exposure

Question 7

Which type of keratopathy in cetaceans can be seen secondary to chronic antibiotic use? Which antibiotic class is at fault?

Answer 7

(1) Horizontal keratopathy

(2) fluoroquinolones

Question 8

What medication can be added to ophthalmic drops to aid in penetrating the mucus tear film in cetaceans?

Answer 8

3% acetylcysteine

Question 9

What feature is unique regarding the optic nerve in pinnipeds?

Answer 9

Unmyelinated

Question 10

Describe the features of pinniped keratopathy.

Answer 10

There are 3 stages of disease. This condition is only observed in captivity.

Stage 1 - perilimbal edema +/- ulcer (<10% of cornea affected)
Stage 2 - progression of edema and pigmentation (<20% of the globe), infection in this stage common, +/- ulcer
Stage 3 - opacity covers >20% of the globe, ulcer

Risk factors for development include UV exposure, lack of shade structures, juvenile variant in california sea lions

Question 11

Which pinniped species are prone to lens disease?

Answer 11

Harbor seals (90%) (Phoca vitulina)

Question 12

List risk factors associated with formation of cataracts in pinnipeds (4)

Answer 12

(1) Age (>15 years)
(2) Hx of fighting
(3) Hx of previous ocular disease
(4) lack of shade

Question 13

Harbor seals (Phoca vitulina) are predisposed to what specific post-operative condition after lensectomy for cataracts?

Answer 13

lipid keratopathy

Question 14

What intraoperative complication has been observed with the use of alpha 2 agonists in pinnipeds undergoing ocular surgery?

Answer 14

intraocular hemorrhage leading to hyphema

Question 15

What is the oculocardiac reflex?

Answer 15

traction of extraocular muscles triggers hypoventilation, hypoxemia, acidosis leading to death