origin at medial canthal tendon and corrugator supercilius muscle
palpebral (pretarsal & preseptal)
reflex blink and involuntary
pretarsal origin at post lacrimal crest (most important to keep lid apposed to globe to let punctum lie in tear lake ) & ant limb of med canthal tendon; deep head of pretarsal m. (Horner’s tensor tarsi) encircles canaliculi to facilitate tear drainage
upper & lower segments of pretarsal orb m. fuse to become lateral canthal tendon
pretarsal muscle firmly adherent
pretarsal muscle of Riolan = gray line = superficial orbicularis
extension of periosteum
in non-Asians, upper lid septum fuses w/levator aponeurosis. 2-5 mm above sup tarsal border; in lower lid it fuses w/capsulopalpebral fascia at or just below inf tarsal border
passes medially in front of trochlea
barrier to hemorrhage and infection between lid and orbit
orb fat can herniate through septum into lids causing bags
central orb fat pad lies behind septum, in front of levator aponeurosis.
dense connective tissue, attach med & lat to periosteum
1 x 29 x 11 mm upper lids, 4 mm vertical height in lower lids
meibomian glands are modified holocrine glands
in upper lid marginal arcade lies 2 mm sup to lid margin, ant to tarsus
peripheral art arcade is sup to tarsus, between levator aponeurosis, Muller’s
Lacrimal Anatomy
Lacrimal Gland
separated from orbit by fibroadipose tissue
divided by LPS aponeurosis, smaller palpebral portion visible, larger orbital half hidden
blood vessels, lymph, nerve, and excretory ducts pass from orbital part through palpebral section
don’t biopsy or remove palpebral lobe which might significantly reduce tearing
ducts empty 5mm above superior tarsal border
reflex tear arc: afferent from V stimulates tear production from lacrimal gland; efferent complicated (with parasympathetics from VII, sympathetics not understood)
exocrine gland, acinar and myoepithelial cells, lacrimal artery
Accessory Glands of Krause and Wolfring
no neural control, basal tear production (BST)
located in sup fornix & above sup border of tarsus
Canalicular System
puncta sit in tear lake, approx 6mm from canthus, then 2 mm ampulla, then canaliculi extend medially 8-10 mm to common canaliculus (in 90% of population), then to lat wall of tear sac
dilation prior to sac: sinus of Maier, enters sac superior and posterior
valve of Rosenmuller prevents reflux from sac into common canaliculus during tear pump
sac lies btw ant and post crura of med canthal tendon in lacrimal sac fossa
puncta/lids move medially with lid closure
deep heads of preseptal orbicularis (Horner’s muscle) inserts on post lacrimal crest, lateral half of superior lacrimal sac, encircles canaliculi to help pump
Bony System
interosseos direction of Nasolacrimal Duct = inferior and slightly. lateral, posterior
Nasolacrimal Duct is approx 12 mm long, intranasal ostium high up in inf turbinate, covered by valve of Hasner, approx 2.5 cm post to naris on lat wall
lacrimal bone very thin, therefore aim posteriorly in DCR
ethmoid air cells are at superior and deeper parts of fossa, but might extend under entire fossa
mucosa of ethmoid cells gray, thin, and friable
Lacrimal Pump Model
orbicularis actively pumps tears from lake
Rosengren-Doane model: orb m contraction > pressure in lacrimal sac > tears forced into nose > lids open, move laterally > - pressure in sac helped by closed valve of Hasner > lids open fully and puncta pop open, with - pressure drawing tears into ampulla and canaliculi
Jones model: closure--lateral move = negative pressure
