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