Orbital Tumors - Anatomy
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- thinnest in body, no subcutaneous fat
- upper lid crease (fold) = levator . attachment to pretarsal orbicularis and skin; located at level of sup border of tarsus
- upper puntca is more medial
- mucocutaneous border is post to meibomian gland level
- gray line = muscle of Riolan (superficial orbicularis)
- Zeis, sebaceous glands (holocrine) with cilia
- Moll glands (only apocrine gland on lid) with skin
- 100 lashes on upper lid, 50 on lower
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- extensive anastamosis between supraorbital, lacrimal branches of ophthalmic a. (from internal carotid) and angular and temporal a. (from ext carotid)
- venous drainage: pretarsal, poatarsal
- NO lymphatics for the orbit except in conjunctiva
- eyelid medial lymphatics drain to submandibular nodes and laterally to preauricular nodes
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- main protractor
- supplied by Cranial Nerve VII, narrows PF, helps lacrimal pumporbital
- voluntary sphincter (wink, blepharospasm)
- 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
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- 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.
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- 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 may possibly 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
- Becker model: closure--upper half lateral move = lower pressure, lower half medial move with higher pressure
- fistulas develop inferior to medial canthal tendon b/c tendon itself is tough
Procedures
