29. Periorbital Anatomy
Jason K. Potter, Grant Gilliland
SKELETAL AND SURFACE ANATOMY1
KEY SKELETAL LANDMARKS OF THE PERIORBITAL REGION (Fig. 29-1)
Fig. 29-1 Bony anatomy of the orbit.
■ Superior orbital rim: Fixed landmark to assess brow position
■ Inferior orbital rim: Position relative to anterior surface of globe; important in determining positive versus negative vector of orbit
■ Temporal ridge: Delineates lateral border of forehead from temporal fossa
■ Supraorbital notch: Delineates location of supraorbital neurovascular bundle
EYEBROW SURFACE ANATOMY
UPPER FOREHEAD ARRANGED IN WELL-DEFINED LAYERS
■ Skin
■ Subcutaneous tissue
■ Galea aponeurosis
■ Loose areolar tissue
■ Periosteum
• At origin of frontalis muscle, the galea splits into a superficial and deep layer to encase the muscle.
• The deep layer splits again at the midforehead level to surround the galeal fat pad, and again caudal to the fat pad to form the glide plane space of the brow.
• The subgaleal space, deep layer of the galea, and periosteum fuse in the lower forehead and are firmly attached to the frontal bone.
• Movement of the brow is produced through the action of brow elevators and depressors and is enhanced by the presence of the galeal fat pad, glide plane space and subgaleal space.
• The periosteum of the frontal bones is reflected at the arcus marginalis to become the periorbita of the periorbital bones. The arcus marginalis is a thick condensation of periorbita as it enters the orbit.
EYELID SURFACE ANATOMY1,2 (Fig. 29-2)
Fig. 29-2 Sagittal view of the periocular layers.
■ Protects the eye from injury and excessive light and prevents desiccation of the cornea.
■ Provides nutrients to the avascular cornea, distributes oil throughout the tear film, debrides the ocular surface of foreign matter, and secretes antiinflammatory substances onto the cornea
■ Promotes drainage from the lacrimal system
■ Consists of two lamellae:
1. Skin/orbicularis oculi
2. Tarsoconjunctival layer
■ Palpebral fissure: Aperture between upper and lower eyelids (Fig. 29-3)
Fig. 29-3 Typical topographical measurements of the periorbita. (PFH, Palpebral fissure height; PFW, palpebral fissure width.)
• 8-12 mm vertically, 28-30 mm horizontally
■ Upper lid margin rests 0.5-1.0 mm below the upper limbus.
■ Lower lid margin lies at the level of the lower limbus.
SKIN
■ Eyelid skin is the thinnest on the body.
• Minimal subcutaneous fat
■ Adjacent brow and malar skin are notably thicker.
■ Surgical incisions within the skin of the eyelid generally heal with almost imperceptible scarring.
■ Age-related changes in the skin include decreased type I collagen and increased dermal collagenase activity.
MUSCLES
■ Frontalis
• Originates from the galea aponeurosis and inserts into the dermis of the lower forehead
• Interdigitates with procerus and orbicularis at its insertion
• Elevates brow, produces transverse forehead rhytids
■ Corrugator supercilii (Fig. 29-4)
Fig. 29-4 Comprehensive corrugator supercilii muscle dimensions.
• Corrugators start 3 mm lateral to midline and end about 85% of distance to lateral orbital rim.3
• Oblique head: Originates from the superomedial orbit and inserts into the dermis of the medial brow
• Transverse head: Originates from superomedial orbit and inserts into dermis superior to the medial third of the medial brow
• Depresses and medializes the medial brow, produces vertical glabellar rhytids
• Lies deep to frontalis muscle
■ Depressor supercilii
• Originates from superomedial orbit and inserts into the dermis of the medial brow, medial to the insertion of the orbicularis
• Lies superficial to the corrugator
• Depresses the medial brow
■ Procerus muscle
• Originates from fascia covering lower part of nasal bone
• Inserts onto glabellar dermis
• Depresses the glabella
■ Orbicularis oculi (Fig. 29-5)
Fig. 29-5 Muscular anatomy of the periorbital region. A, View from outside the orbit. B, View from inside the orbit. C, Complex insertion of the orbicularis muscle at the medial canthus.
• Encircles the periorbital region
• Primary constrictor of the lids
• Innervated by the facial nerve (CN VII)
► Runs on the deep surface of the muscle
• Pretarsal fibers lie over the region of the tarsal plate.
► Responsible for involuntary blink
• Preseptal fibers overlie the orbital septum.
► Assist with blink
♦ Both voluntary and involuntary fibers
• Orbital fibers overlie the orbital rims.
► Produce voluntary, forceful closure
NOTE: Age-related changes in the orbicularis oculi are secondary to muscle relaxation and increasing ptosis.
NOTE: Changes result in visibility of the inferior muscle border with formation of a malar crescent4
■ Muscle of Riolan: Portion of the pretarsal orbicularis comprising the “gray line” in the eyelid margin. Promotes secretion from the meibomian glands.
■ Horner tensor tarsi muscle: Portion of the pretarsal orbicularis attaching to the posterior lacrimal crest. Encircles the canaliculi and promotes lacrimal drainage.
■ Jones muscle: Posterior preseptal orbicularis muscle fibers that insert on the posterior lacrimal crest and promote tear drainage.
■ Eyelid retractors
• Upper lid (Fig. 29-6)
Fig. 29-6 Levator muscle and Müller muscle relationship.
► Levator muscle
♦ Origin at the posterior orbit on the annulus of Zinn
♦ Insertion onto the superior tarsal border
♦ Insertion through the orbicularis onto the subdermal skin at the lid crease (in whites, lower insertion or none at all onto subdermal pretarsal skin in Asians)
► Müller muscle (Fig. 29-7)
Fig. 29-7 Müller muscle after the levator muscle is cut away.
♦ Innervated by the sympathetic nervous system
♦ Arises from the inferior surface of the levator approximately 10-12 mm above the upper border of the tarsal plate and inserts onto the superior edge of the tarsus
♦ Loss of function results in 2-3 mm of ptosis.
► Levator palpebrae superioris
♦ Innervated by the superior division of CN III
♦ Originates from the lesser wing of the sphenoid above the optic foramen at the annulus of Zinn and extends forward to insert onto the superior edge of the tarsus; also, attaches to the posterior lacrimal crest through the medial horn of the levator tendon, the lateral orbital tubercle, and the pretarsal skin forming the eyelid crease
• Lower lid
► Inferior tarsal muscle is analogous to Müller muscle in the upper eyelid (Fig. 29-8).
