Layers & Components of the Eyelid 

• Skin
  • thinnest in body, no subcutanous 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 supraorb ital , 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 pump orbital
  • voluntary sphincter (wink, blepharospasm)
  • origin at medial canthal tendon and corrugator supercilius muscle
  • palpebra l (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

• Conjunctiva
  • mucin is produced from goblet cells
  • aqueous is produced from glands of l Krause & Wolfring

• Eyelid Retractors (muscle)
  • Upper lid
    • Levator Palpebrae Superioris
      • starts just above annulus of Zinn, then 40 mm of muscle, then 14-20 mm of aponeurosis.
      • becomes vertical near Whitnall's (superotransverse) ligament (near transition m. to aponeurosis.) which is a fulcrum for vertical lid retraction (lower lid analog is Lockwood's ligament)
      • Whitnall's ligament is condensation of tissue around SR and LPS, helps suspend tissue
      • levator aponeurosis: attaches to lower 1/2 of ant tarsus; lat horn of aponeurosis divides lacrimal gland into orb and palpebral lobes, attaches to lat orb tubercle; medial horn attaches to post lacrimal crest
      • lid crease is formed by attachment of ant portion of aponeurosis w/ septum between the pretarsal orbicular m.'s: here the pretarsal tissues are in close apposition to underlying tarsus
    • Superior Tarsal Muscle of Muller
      • posterior to LPS
      • sympathetically innervated; use neo drops to test function in Ptosis w/u: normal = 2 mm lift
      • origin from under LPS, attaches to upper tarsus, firm attachment to conj
  • Lower Eyelid s
    • Inferior Tarsal muscle
    • Capsulopalpebral Fascia
      • lower lid analog to levator aponeurosis
      • originates from attachments to Inferior rectus ; therefore do vertical m. surgery before lid surgery
      • inserts onto lower tarsal border
      • inferior tarsal m. is analog to Muller's, runs post to Capsulopalpebral Fascia