Nasolacrimal System

Question 1

What are the 3 layers of the tear film, where are they from and what is their function?

Answer 1

Outer lipid layer- meibomian glands (palpebral conjunctiva). Decrease evaporation and protective oily barrier

Middle aqueous layer- lacrimal gland (dorsolaterally) +nictitans glands. Provides O2, nutrients, smooth movement and corneal protection

Inner mucin layer- conjunctival goblet cells. Adheres to the cornea, filling depressions, allowing aqueous layer to spread over globe

Question 2

What part of the tear film does STT test?

Answer 2

Aqueous- basal and some reflex

Question 3

What epithelium lines the nasolacrimal system?

Answer 3

Pseudostratified columnar epithelium

Question 4

Apart from the nasal ostium close to the external nares, where else can the nasolarimal duct open?

Answer 4

Hard palate at the level of the canine

Question 5

During KCS the surface epithelium undergoes squamous metaplasia, what does this do?

Answer 5

Reduction in mucin adherence and further tear film destabilisation

Question 6

What size breeds does aplasia/ hypoplasia of the lacrimal gland occur in (congenital)?

What is the treatment?

Answer 6

Toy breeds (Chinese Crested, Yorkies)

Ciclosporin- some respond some don’t
Lubricants
PDT

Question 7

Which endocrine diseases can be related to KCS?

Answer 7

Hypothyroidism
DM
HyperAdrenocorticism
Atopy

Question 8

What is the downside of using hypromellose as a lubricant?

Answer 8

It needs to be applied regularly (hourly)

Question 9

If STT =>2mm/min what % will respond to ciclosporin?

If STT is 1mm/min what % will respond to ciclosporin?

Answer 9

80%

50%

Question 10

How long can it take ciclosporin to work?

Answer 10

Up to 8weeks

Question 11

Before doing a parotid duct transposition (PDT) what is it important to do?
What test can be done?

Answer 11

Check the parotid duct actively secretes saliva.
Check pH of saliva

Put lemon juice/ atropine on the tongue and look for salivation and discharge from the parotid papilla

Question 12

What are possible complications of parotid duct transposition (PDT)?

Answer 12

Overly wet eyes
Periorbital dermatitis
Crystal like deposits on the cornea (usually calcium)

Question 13

What size nasolacrimal cannulas do you use to flush?

Answer 13

0. 76mm D, 32mm L (blue)

0. 91mm D, 32mm L (Pink)

Question 14

Which puncta is normally affected by imperforate/ micropuncta?

• in cats?
• in dogs?

Answer 14

Cats - upper

Dogs - lower

Question 15

What are CKCS prone to if they have a curly coat?

Answer 15

KCS

Question 16

Which breeds are susceptible to immune mediated KCS?

Answer 16

Question 17

Which nerves are involved in innervation to the lacrimal gland?

Answer 17

Facial nerve VII

Trigeminal nerve V

Question 18

What is a normal TBUT?

Answer 18

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