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Eye, Eyelid, Lacrimal & Orbital Anatomy

Eyelid 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
  • Blood supply
    • 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
  • Orbicularis Muscle
    • 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
  • Septum
    • 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.
  • Tarus
    • 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