Lacrimal/Nasolacrimal system

Question 1

3 Tear film layers and where they each come from

Answer 1

1. Oily layer Meibomian Gland
2. Watery portion - lacrimal gland and gland of 3rd eyelid
3. Mucus - bulbar, paperbral and 3rd eyelid conjunctiva

Question 2

4 functions of precorneal tear film

Answer 2

1. antimicrobial activity
2. optical clarity
3. oxygen transport
4. waste removal

Question 3

Nerves involved in tearing

Answer 3

afferent ophthalmic branch of CN5, efferent psns fibers of CN7

Question 4

Nasolacrimal ducts and punctae dog

Answer 4

upper and lower palpebral punctae, passes through lacrimal and maxillary bones, exits in the nasal vestibule, lateral to the floor of the vestibule

Question 5

Nasolacrimal ducts and punctae cat

Answer 5

same as dog

Question 6

Nasolacrimal ducts and punctae horses

Answer 6

palpebral punctum similar to dogs, can visualize the nasal punctum in the floor of the nasal vestibule, medially

Question 7

Nasolacrimal ducts and punctae cattle and llama

Answer 7

similar to the horse with the exception that the nasal punctae are more dorsally and laterally located than in the horse

Question 8

Keratoconjunctivitis sicca, what is it?

Answer 8

Decreased tear film, Dry Eyes.
the MOST important nasolacrimal system disorder. It is sight threatening and PAINFUL.
DOGs>cats>others

Question 9

Clinical signs of KCS in Dog

Answer 9

1. Decreased aqueous tear film as measured with a Schirmer tear test (STT) strip
2. PAIN
3. Thick mucous thread, dried ocular discharge around lids due to lack of aqueous tear
4. Corneal and conjunctival changes (dry, reddened, ulcers, neovascularization, pigmentation

Question 10

Clinical signs of KCS in Cat

Answer 10

Schirmer tear test does not work well in cats

cats show little signs like mucus, mild keratitis, repeated bouts of conjunctivitis

Question 11

Breed Predispositions

Answer 11

Brachycephalics: Pugs, Lhasa Apsos, Shih Tzus, Boston Terriers, and English Bulldogs
small terriers such as Cairns and West Highland White
Shelties, Poodles, Golden Retrievers, Spaniels (American, English, Cavalier
Any breed predisposed to atopic dermatitis (above)

Question 12

Cause of KCS in Dog

Answer 12

#1 Immune-mediated/Idiopathic
Congenital
Active infections, Previous infections
CN7 damage (Cocker Spaniels)
Sulfonamides and etodoloc and Loco weed poisoning in cattle out west
Atropine
General anesthesia (why we put lube)
Iatrogenic (3rd eyelid removal or post-radiation)

Question 13

Medical therapy of KCS

Answer 13

Medical therapy can induce natural tear production

1. Cyclosporine-A – works well in predisposed dogs, not in other species (cats). Does not work in drug induced KCS. Tacrolimus also works (other calcineurin inhibitor/T-cell suppressor)
2. Supportive care - artificial tears
3. Abx if indicated
4. Mucolytic agents - acetylcysteine
5. lacrimomimetics - Pilocarpine
6. Corticosteroids - dec. surface inflam. but more prone to infections
7. Good hygiene
8. Oral interferon

Question 14

Surgical Therapy of KCS

Answer 14

1. Temporary - tarsorrhaphy or 3rd eyelid flap
2. Permanent - tarsorrhaphy, medial or lateral
3. Parotid duct transposition for “Last Ditch Effort” when months of medical therapy don’t work but lots of potential complications

Question 15

What is Epiphora?

Answer 15

Epiphora is abnormal flow of tears onto the face. Compared to decreased tear production, this is not near as big a problem to the animal.

Question 16

Causes of epiphora

Answer 16

1. Hypersecretion (infections, irritations, FBs)

2. Poor drainage (congenital, entropion, ectropion, deformities, nasolacrimal obstruction

Question 17

Diagnosis of epiphora

Answer 17

1. Schirmer Tear test, compare eye to normals and eye to eye
2. Fluorescein, see if it comes out nose
3. Flush nasolacrimal duct
4. contrast rads
5. Poodle epiphora – Poodles, Bichon, Maltese, Cocker Spaniels

Question 18

Medical therapy of epiphora

Answer 18

1. Flush nasolacrimal ducts then give anti-inflammatory steroid drop
2. Treat conjunctivitis or other surface disease
3. Oral tetracycline to reduce pigmentation

Question 19

Surgical therapy of epiphora

Answer 19

1. if atresia, can open it with suture and pigtail probe
2. repeatedly plugged ducts, stent a few weeks
3. perm. scarred shut then dacryocystorhinostomy
4. DO NOT REMOVE 3rd EYELID!

Question 20

What is Dacryocystitis?

Answer 20

Infection or inflammation of the nasolacrimal duct system

Question 21

Clinical signs of dacryocystitis

Answer 21

Epiphora PLUS Purulent discharge. May or may not be painful

Question 22

Causes of dacryocystitis

Answer 22

1. congenital atresia (common in horses and llamas)
2. FB obstruction
3. compression due to facial fracture

Question 23

Therapy of dacryocystitis

Answer 23

1. Frequent flushing w/ systemic and topical abx
2. duct catheterization for 2-3 weeks with topical abx/corticosteroid drops
3. Open congenital malformation (horses and llamas)