Ophthalmology - Lacrimal System

Question 1

What are the layers of the tear film?

Answer 1

• lipid (outermost)
• aqueous (middle)
• mucinous (innermost)

Question 2

What is the source of the aqueous layer?

Answer 2

lacrimal gland and gland of the third eyelid

Question 3

What are the possible causes of quantitative KCS?

Answer 3

• immune mediated destruction of lacrimal tissue
• excision of third eyelid gland
• PSNS lesions
• canine distemper
• drugs

Question 4

What are the clinical signs associated with quantitative KCS?

Answer 4

• blepharitis
• mucoid/mucopurulent discharge
• keratoconjunctivitis
• corneal pigmentation
• can be blinding if severe

Question 5

How is quantitative KCS treated?

Answer 5

• topical cyclosporine

- if no response: Tacrolimus

Question 6

What is neurogenic KCS?

Answer 6

loss of parasympathetic innervation to the lacrimal gland and ipsilateral nostril

Question 7

What are the possible causes of neurogenic KCS?

Answer 7

trauma
severe otitis interna
neoplasia
idiopathic

Question 8

How is neurogenic KCS treated?

Answer 8

Pilocarpine

- stimulates PSNS

Question 9

Which virus causes KCS in dogs?

Answer 9

Canine Distemper virus

Question 10

What is the surgical option for treating KCS?

Answer 10

parotid duct transposition

• moves parotid salivary duct to the lower conjunctival fornix
• saliva replaces tears

Question 11

What are the disadvantages/complications of parotid duct transposition?

Answer 11

• reaction to higher pH of saliva
• moist pyoderma from overproduction
• mineral deposition in cornea and eyelids

Question 12

What is the source of the lipid layer?

Answer 12

meibomian glands

Question 13

What is the function of the lipid layer?

Answer 13

stabilize the aqueous layer and prevent evaporation

Question 14

What test results indicate quantitative KCS?

Answer 14

• superficial corneal and conjunctival inflammation (keratoconjunctivitis)
• shirmer tear test < 15 mm/min (sicca)

Question 15

What test results indicate qualitative KCS?

Answer 15

superficial keratoconjunctivitis with a normal shirmer tear test

Question 16

What is the source of the mucin layer?

Answer 16

conjunctival goblet cells

Question 17

What is the function of the mucin layer?

Answer 17

creates surface tension that anchors the aqueous and lipid layer to the cornea

Question 18

What test/result indicated mucin deficiency?

Answer 18

Tear Film Breakup Time

• time it takes for fluroecein stain to beak up on the ocular surface
• abnormal < 20 seconds

Question 19

What is the underlying cause of qualitative KCS?

Answer 19

lipid or mucin deficiency

Question 20

What are the clinical signs associated with qualitative KCS?

Answer 20

• blepharospasm, epiphora, hyperemia, superficial conjunctivitis and keratitis, and corneal fibrosis
• corneal fibrosis: whitish hazy appearance

Question 21

How is qualitative KCS treated?

Answer 21

• replace the tears (lubrication)

- immunomodulation: cyclosporine

Question 22

Describe the anatomy of the nasolacrimal drainage system

Answer 22

• lacrimal gland on lateral upper lid
• two lacrimal puncta on the medial canthus
• puncta come together at lacrimal sac
• continue to the nasal punctum

Question 23

What is epiphora?

Answer 23

overflow of tears on the face

Question 24

What are possible causes of epiphora?

Answer 24

• poor drainage (hypoplastic puncta, entropion)

- blockage (FB, neoplasia, inflammation)

Question 25

What is the Jones test?

Answer 25

• looking at patency of the nasolacrimal drainage system

- fluorescein in the eye, hold nose down, look for stains in the nares

Question 26

What are the clinical signs associated with Dacryocystitis?

Answer 26

• mucopurulent discharge
• epiphora
• swelling in the medial canthal region

Question 27

What is Dacryocystitis?

Answer 27

inflammation of the nasolacrimal drainage system

Question 28

What are the possible causes of Dacryocystitis?

Answer 28

foreign bodies
infection
trauma