Lacrimal gland and tear drainage

Question 1

Where are tears produced?

Answer 1

Lacrimal gland and accessory lacrimal tissues

Question 2

How does congenital nasolacrimal duct obstruction present?

Answer 2

2-4% of newborns
Presents with tearing and mattering
>90% resolve by 1 year
Of those 10% that don’t improve, probing cures 95%

Question 3

What are the common congenital and canalicular abnormalities?

Answer 3

Imperforate puncta
Absent puncta
Punctal and canalicular atresia
Can involve upper and lower

Question 4

Where is the lacrimal gland/sac found?

Answer 4

Superolateral aspect of orbit in lacrimal fossa (anteriorly has thick maxillary bone, posteriorly has thin lacrimal bone)
anterior part of medial orbit in lacrimal sac fossa

Question 5

What is the significance of the posterior lacrimal crest?

Answer 5

Lacrimal bone
Posterior extent of lacrimal sac fossa
Deep/posterior portion of medial canthal tendon inserts here

Question 6

How does the lacrimal bone density vary?

Answer 6

Thicker posterior to posterior lacrimal crest
Significant in DCR as incision into nasal cavity should be through the anterior part of lacrimal bone where it is thinnest

Question 7

Where does the nasolacrimal duct run?

Answer 7

Begins as an opening in the inferoanterior orbital floor
Descends through maxillary bone
Passes posteriorly and laterally towards first molar tooth

Question 8

What are the three layers of the tear film?

Answer 8

Lipid layer
Aqueous layer
Mucinous layer

Question 9

What are the two lobes of the lacrimal gland?

Answer 9

Orbital lobe (superior and larger)
Levator palpebrae superioris lies inbetween
Palprebral lobe

Question 10

How big is the lacrimal gland?

Answer 10

20x 12 x 5mm
Orbital lobe
Palprebral lobe (1/4 of total size)

Question 11

What are the anatomic relations of the lacrimal gland?

Answer 11

Orbital : posterior to orbital septum and preaponeurotic fat pad. Anterior to levator aponeurosis
2-6 ducts travel through orbital part into palpebral part where they form 6-12 ducts which drain into the superolateral conjunctival fornix
Therefore, removal of palpebral portion renders the entire gland non functional

Question 12

Describe the histology of the lacrimal gland

Answer 12

Compound tubuloacinar gland (serous type)
Composes of lobules
Each lobule contains numerous acini
Each acinus is a single layer of cuboidal or columnar cells
Stellate shapes myoepithelial cells surround each acini

Question 13

What are the two types of accessory lacrimal gland?

Answer 13

Glands of Krause

Glands of Wolfring

Question 14

Where are the glands of Krause?

Answer 14

20-40 in superior conjuntival fornix and half that in the lower eyelid.

Question 15

WHere are the glands of Wolfring?

Answer 15

Superior tarsal border
Under sympathetic stimulation
Baseline tear production

Question 16

What is the blood supply to the lacrimal gland?

Answer 16

Lacrimal artery (branch of ophthalmic artery) with contributions from infraorbital artery and recurrent meningeal artery

Question 17

What is the nerve supply of lacrimal gland?

Answer 17

V1 ophthalmic nerve-> frontal nerve-> lacrimal nerve
Runs on top of superior rectus to supply gland
Pierces septum and supplies upper lid and conjunctiva
Parasympathetic sphenopalatine ganglion
Descending autonomic pathways from hypothalamus influence lacrimal system

Question 18

When does reflex crying occur?

Answer 18

Irritation of cornea, conjunctiva and nasal epithlium

Question 19

Describe the excretory system?

Answer 19

Eye lids
Puncta
Canaliculi
Lacrimal sac
Nasolacrimal duct
Nose

Question 20

How do eyelids affect tears?

Answer 20

Eyelids move the tears across the eye from lateral to medial

As we age, the eyelids sag which can cause eye watering

Question 21

How does the medial insertion of orbicularis oculi assist with lacrimal function?

Answer 21

Orbicularis oculi inserts medially which encases the lacrimal sac
Horner’s muscle (deep head of preseptal orbicularis oculi) contributes to lacrimal pump and moves eyelids medially
Provides active passage of tears during blinking

Question 22

Describe the movement of tears from the tear meniscus to lacrimal sac

Answer 22

Both active and passive
Passive: gravity and capillary action
Active: medial canthus blinking. When eyelids close the puncta meet, squeezing the tears already in the ampulla, pushing them into the horizontal portion of duct

Question 23

Describe the puncta

Answer 23

0.1-0.2mm diameter
Surrounded by ring of fibrous tissue
Lacrimal papillae are surrounded by orbicularis oculi fibres creating a tiny sphincter
Can close by meeting other puncta or individually by its own sphincter -therefore surgically important not to damage the puncta by cutting it open

Question 24

Describe the caniliculi

Answer 24

Short vertical 2mm
Longer horizontal 8-10mm
Lower longer than upper
Curve posteriorly and medially towards lacrimal sac
Pass behind medial canthal tendon and meet at an angle 25 degrees forming the common canaliculus

Question 25

Does everyone have a common canaliculis?

Answer 25

90% of adults

2% completely separate upper and lower canaliculi

Question 26

What are the two distinct parts of the lacrimal sac?

Answer 26

Portion 3-5cm above common opening= fundus

Portion9-12cm below common opening =body

Question 27

Describe the histology of the lacrimal sac

Answer 27

Fibroelastic tissue arranged in a helical pattern

Lumen lined by non keratinized stratified columnar epithelium

Question 28

Why does the lacrimal sac expand laterally and anteriorly as it enlarges (eg in mucocoele)?

Answer 28

Below the medial canthal tendon, the sac is only covered by lacrimal fascia, orbicularis oculi and skin
The tendon and sac limit superior sac expansion

Question 29

What is the blood supply of the lacrimal sac?

Answer 29

Ophthalmic artery:
dorsalis nasi, medial palpebral artery
External maxillary artery:
angular branch of the facial artery
Internal maxillary artery:
Infraorbital branch

Question 30

What is the nerve supply of the lacrimal sac?

Answer 30

Infratrochlear branch of nasociliary nerve

Question 31

Which other duct is the lacrimal sac continuous with?

Answer 31

Nasolacrimal duct lies inferior and is continuous with lacrimal sac
It runs posteriorly in relation to the nasal canal

Question 32

What is the name for the inferior opening of the nasolacrimal duct into the nose?

Answer 32

Valve of hasner

Question 33

What is the embryological origin of the lacrimal gland?

Answer 33

Ectodermal buds invade underlying mesenchyme
10th week: tendon of LPS develops
Tears begin 3 months after birth
Development of gland continues until 3-4 years old

Question 34

What is the sympathetic nerve supply to the lacrimal gland?

Answer 34

From superior cervical ganglion
Travel through sphenopalatine ganglion (but do not synapse)
Joins maxillary nerve
Then lacrimal nerve

Question 35

What are the two different types of mucin present in the mucoid layer of the tear film?

Answer 35

Muc1/4: maintains hydration of ocular surface +stabilises tear film
MUC5AC: traps pathogens and debris to be cleared by blinking

Question 36

What is contained in the aqueous layer of the tear film?

Answer 36

Secreted by lacrimal and accessory lacrimal glands

Contains water, electrolytes, lysozymes (eat bacteria) and lactoferrin (eats iron)

Question 37

What is contained in the lipid layer of the tear film?

Answer 37

Secreted by meibomian glands

Prevents evaporation of tear film and smooth ocular surface during blinking

Question 38

What is posterior blepharitis?

Answer 38

Meibomian gland dysfunction
Risk factors; age, smoking, associated with rosacea
Presents with dry eye symptoms and oily Meibomian glands visible
Inferior staining with lisssamine green is suggestive of incomplete blink
Treated with warm compress, doxycycline and omega 3 supplements