Layers & Components of the Eyelid  - Eyelid Anatomy

• 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.

• Tarsus

• 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 Eyelids
  • 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

Orbit

Orbital volume  and dimensions: = 30 cc, 35(Height) x 45(Width) x 45 mm(medial wall depth), globe 25 x 25 mm

Bones: (F)rontal, (M)axillary,(Z)ygomatic, (L)acrimal, (E)thmoid, (P)alatine, (S)phenoid



• Roof
• Bones
  • Frontal
  • Lesser wing of sphenoid
• Contents
  • lacrimal gland fossa
  • trochlea 4mm posterior to margin for superior oblique tendon
  • Supraorbital notch/foramen
• Clinical Correlations
  • subperisteal abscess
    
• Medial wall
  • Bones
    • Maxillary
    • Lacrimal
    • Ethmoid - thinnest
    • Sphenoid
  • Contents
    • lacrimal sac fossa
    • cribiform plate is medial to anterior orbit at the level of fronto-ethmoidal suture
  • Clinical Correlations
    • Nasoclacrimal duct obstructions./tumors/DCRs
    • Medial wall fractures
    • subperisteal abscess
    • Orbital cellulitis/proptosis from ethmodial extension

• Floor

  • Bones
    • Maxillary- second thinnest, thins posteriorly
    • Zygoma
    • Palatine
  • Contents
    • infraorbital foramen
    • inferior oblique origin
    • slopes 20 degrees down
    • suspensory ligament of eyeball
  • Clinical Correlations
    • subperiosteal abscess
    • blow-out fractures
      
• Lateral wall
  
  • Bones
    • Zygomatic bone
    • Greater wing of sphenoid
  • Contents
    • lateral orbital tubercle is 11mm below F-Z suture,
      • serves as attachment of check ligament of lateral rectus
  • Clinical Correlations
    • Tripod fractures
    • Ruptured globes
    • Lateral tarsal strips
    • adjacent to middle cranial fossa, temporal fossa, and pterygopalatine fossa
      


• The medial orbital walls are nearly parallel and are 25 mm apart
• The orbit is widest not at its entrance, but 1 cm from the orbital rim
  

Holes & Fissures

• Fissures
  • Superior orbital fissure (SOF):
    • 22 mm long
    • separates greater wing of sphenoid from lesser wing of sphenoid
    • transmits third, fourth, sixth and V1 AND SYMPATHETIC FIBERS
    • lateral rectus origin separates into superior and inferior divisions
      • Superior division transmits lacrimal, frontal and trochlear nerves
      • Inferior division transmits superior and inferior divisions of CN III, nasociliary branch of CN V, CN IV, superior ophthalmic vein, and sympathetic nerve plexus
      • Venous system: superior ophthalmic vein
  • Inferior orbital fissure (IOF )
    • L ocated between lateral orbital wall and the orbital floor
    • Transmits V 2 ( maxillary) , pterygoid nerves  nerve arising from pterygopalatine ganglion
    • infraorbital nerve (a branch of V 2 ) enters the infraobital groove and infraorbital canal for sensation to lower eyelid, cheek, upper lid, upper teeth
    • Venous system inferior ophthalmic vein
• Holes/Notches/Canals
• Nasolacrimal canal Nasolacrimal canal
  • lacrimal sac fossa to the inferior meatus
  • separates greater wing of sphenoid from lesser wing of sphenoid
  • transmits third, fourth, sixth and V1 AND SYMPATHETIC FIBERS
  • lateral rectus origin separates into superior and inferior divisions
    • Superior division transmits lacrimal, frontal and trochlear nerves
    • Inferior division transmits superior and inferior divisions of CN III, nasociliary branch of CN V, CN IV, superior ophthalmic vein, and sympathetic nerve plexus
    • Venous system: superior ophthalmic vein
  • Supraorbital foramen/notch
    • transmits blood vessels
    • supraorbital nerve
    • Anterior/posterior ethmoidal foramen: transmits ethmoidal blood vessels and nerve
    • Zygomatic foramen: transmits zygomaticofrontal and zygomaticotemporal nerves, zygomatic artery
    • Nasolacrimal duct (NLD): exits into inferior meatus
    • Infraorbital canal: transmits infraorbital nerve (V 2 )
  • Ethmoidal foramina
    • anterior ethmoidal artery
    • posterior ethmoidal artery
    • allows infections and neoplasms to enter to orbit from the sinuses
  • Optic Canal
    • 8-10 mm long
    • located within the less wing of sphenoid
    • separated from SOF by OPTIC STRUT
    • Transmits. Ophthalmic nerve, ophthalmic artery, sympathetic nerves
    • Optic foramen is 6.5 mm wide: it may be enlarged in the presence of optic nerve glioma; 1 mm of asymmetry between right and left is abnormal
      



Axial Orbital MRI




Please see Orbital Tumors and Lacrimal Anatomy