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Orbit Anatomy

  • 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
  • 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

Subcutaneous tissue

  • no fat, loose connective tissue holds fluid in preseptal > pretarsal area b/c less firmly attached
  • main protractor
  • supplied by Cranial Nerve VII, narrows PF, helps lacrimal pump orbital
  • 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

  • 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 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


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