Lacrimal System Flashcards
Tear flow
- Secretion by the lacrimal gland onto the ocular surface
- Channeled medially by the orbicularis pump mechanism
- Drainage into the nasolacrimal system via the upper and lower puncta
- Flow through the upper and lower canaliculi into the common canaliculus
- Common canaliculus → Nasolacrimal sac → Nasolacrimal duct → inferior nasal meatus
Thinnest and most superficial layer of the tear film
lipid layer
prevents evaporation of the tear film
produced by meibomian gland
thickest layer of the tear film
aqueous layer
Produced by lacrimal gland
has an immune function
Deepest layer of the tear film
Mucin layer
Produced by conjunctival goblet cells
Spreads film evenly and keeps it stable
Lacrimal gland innervation
Sensory innervation → lacrimal nerve (branch of CNV1)
Lacrimation (secretomotor) → Parasympathetic (CN7)
accessory lacrimal glands
krause and wolfring
Krause glands
found at the conjunctival fornices and are more abundant in the upper fornix
Wolfring glands
less numerous but bigger. They are found at the tarsal plate.
Eyelash associated glands
The glands of Moll and Zeis
Moll galnds
apocrine (modified sweat glands)
Zeis glands
holocrine (sebaceous)
Schrimers test description
Filter paper placed under the lower lid. Amount of moisture measured after 5 mins
TBUT test description
Eye is stained with fluorescein dye and the time taken for the first dry spot to appear on the cornea is measured
Jones test description
Jones 1 -
Dye squirted onto the conjunctiva and cotton bud placed in the inferior meatus.
Jones 2 -
Dye syringed into the nasolacrimal system and cotton bud placed in the inferior meatus.
Dacryocystography
Radiological evaluation using injected fluorescent contrast to evaluate the nasolacrimal system morphology