Ординатура / Офтальмология / Английские материалы / Surgical Atlas of Orbital Diseases_Mallajosyula_2009

12 Surgical Atlas of Orbital Diseases

called Whitnall’s tubercle, and becomes continuous with the lateral canthal tendon complex (Figure 1.14).

The normal magnitude of upper lid elevation is approximately 14-16 mm. Elevation of less than 10-12 mm is usually abnormal. Elevation of less than 5 mm is considered severe dysfunction and has important implications in ptosis surgery. Because of the close apposition and fibrous interconnections between the levator and the superior rectus muscle, when the globe is elevated, the upper lid follows. This relationship is not passive, and the levator and superior rectus actually co-contract. Likewise, when the globe is depressed, both muscles relax together and the upper lid moves downward.29

At the transitional zone between the anterior muscular component of the levator and its aponeurosis is a fascial sleeve called Whitnall’s ligament, or the superior transverse ligament. This band runs both over and beneath the levator at this point and behaves as a fulcrum point for the levator where contraction of the muscular portion in the horizontal plane becomes directed in the vertical direction.30-32 However, Whitnall’s ligament is not a stationary fulcrum,29 rather, it acts more as a swinging suspender of the levator.31 Whitnall’s ligament also provides mechanical support for the superior orbital soft tissues. Medially, this structure inserts within the fascial tissue surrounding the superior oblique tendon and the trochlea. Laterally, the ligament inserts within the inner surface of the lateral wall into the periorbita of the lacrimal gland fossa, approximately 10 mm above the lateral orbital

Figure 1.14: The levator superioris complex, including Whitnall's ligament

tubercle, or Whitnall’s tubercle. (Note that despite the shared eponym, Whitnall’s ligament does not directly insert into Whitnall’s tubercle). Prior to its lateral insertion, the ligament courses across and divides the lacrimal gland into a superior orbital lobe and an inferior palpebral lobe.30 (Figure 1.15).

Müller’s muscle is a secondary upper lid retractor, providing approximately 1-2 mm of elevation. It originates just deep to the levator aponeurosis at the level of Whitnall’s ligament and is about 12-14 mm in length. Muller’s muscle inserts at the superior edge of the tarsal plate. An important landmark for

this structure is the peripheral vascular arcade which lies between the levator aponeurosis and Müller’s muscle just above the tarsus. Injury to Müller’s or loss of sympathetic innervation, as occurs in Horner’s syndrome, causes a characteristic mild (1-2 mm) ptosis.33

In the lower lid, the retractor complex is called the capsulopalpebral fascia. This structure is a condensation of fibrous attachments to terminal muscle slips from the inferior rectus which course anteriorly to surround the inferior oblique muscle and fuse with its sheath. From this point, an important component of this fascial complex forms Lockwood’s ligament, which extends across the width of the inferior orbit somewhat like a hammock, inserting laterally at the lateral orbital tubercle and medially into the medial canthal tendon and providing some suspensory support to the orbital soft tissues.34 Anterior to Lockwood’s ligament, the capsulopalpebral fascia send fibers into the inferior conjunctival fornix (thus forming the suspensory ligament of the inferior fornix), while additional fibers continue on to fuse with the septum and to finally insert into the inferior border of the tarsal plate. As in the upper lid, the lower lid retractors work in tandem with the inferior rectus to lower the lid with downgaze.

The analogous lower lid structure to Müller’s muscle in the upper lid is the inferior tarsal muscle. Loss of sympathetic innervation may cause a small amount of “reverse ptosis” of the lower lid, elevating the inferior lid margin by approximately 1 mm above its usual resting position.33

The tarsal plates are comprised of dense connective tissue that act at the structural skeleton of the lids. In both lids, the tarsi are 1 mm in thickness. In the upper lid, the tarsus is approximately 10-12 mm in height at the pupillary axis, while the vertical extent of the lower tarsus is 4 mm. The tarsi contain the oil-producing meibomian glands which open on the margin, just posterior to the lash line. In the upper lid, approximately 2-3 mm from the tarsal margin, lies the marginal arterial arcade. In the lower lid this arcade typically lies within 1 mm of the lashes. Distichiasis is the abnormal growth of lashes from the meibomian gland orifices and may occur as a congenital anomaly or as an acquired state. In the

Applied Anatomy of Orbit 13

latter case, distichiasis is often a result of severe chronic inflammation of the lids35.

At their medial and lateral borders, the tarsi taper. The upper and lower tarsi come together at the canthus to form the deep lateral canthal tendon, which inserts just anterior to the lateral orbital tubercle. Recall that the more superficial components of the lateral canthal tendon extend from the lateral pretarsal and preseptal orbicularis oculi muscles. Similarly, the medial aspects of the upper and lower tarsi contribute to the medial canthal tendon, with larger, more superficial components which arise from the orbicularis oculi.

The conjunctiva comprises the most posterior layer of the lids. Basal tear flow is provided by the accessory lacrimal glands of Krause in the upper conjunctival fornix, and the glands of Wolfring in the lower fornix. Additional mucin-producing glands are distributed within both the orbital and palpebral conjunctivae.

The Lacrimal System

The main lacrimal gland lies in the anterolateral orbital roof, within the lacrimal gland fossa of the frontal bone, and measures roughly 20 × 12 × 5 mm. The gland is separated into a palpebral and an orbital lobe by the lateral levator aponeurosis. The primary suspensory support for the main lacrimal gland comes from the Whitnall’s ligament.1 Damage to the ligament leads to forward and downward prolapse of the gland in the orbit.36 Ducts from both lobes pass through the palpebral lobe to empty into the superolateral fornix. Therefore, ideally, lacrimal gland biopsies should not be performed on the palpebral lobe, since injury here may affect drainage from both lobes37 (Figure 1.15).

Innervation and blood supply are provided by the lacrimal nerve and lacrimal artery, which enter the gland posteriorly. Venous drainage occurs via the lacrimal vein, which empties into the superior ophthalmic vein. Parasympathetic inputs originate from the lacrimal nucleus of the pons. These preganglionic fibers pass through the geniculate ganglion and then travel with the greater petrosal nerve to synapse eventually within the pterygopalatine ganglion. These fibers then directly synapse in the lacrimal gland.38, 39 Additional postganglionic

14 Surgical Atlas of Orbital Diseases

fibers traveling along branches of the maxillary division of the trigeminal nerve that converge with the lacrimal nerve to enter the orbit also innervate the lacrimal gland.40

Tears drain medially via the upper and lower lid puncta, into the canaliculi, and into the lacrimal sac (Figure 1.16). The puncta are approximately 0.3 mm in diameter. The initial segment of each canaliculus extends 2 mm perpendicular to the lid margin then turns roughly 90° medially toward the canthus. These horizontal canalicular segments are approximately 8 mm in length. The lower canaliculus is typically slightly longer than its upper lid counterpart. In 90% of individuals, the upper and lower canaliculi then fuse to form a 2 mm long common canaliculus which lies between the anterior and posterior limbs of the medial canthal tendon and enters the lacrimal sac.41 The valve of Rosenmüller is located at this junction and prevents the reflux of tears from the sac retrograde into the canaliculi. The lengths of each component of the lacrimal drainage system become important when performing probing and irrigation to evaluate the patency of the outflow system.

The lacrimal sac sits within the lacrimal sac fossa. It is 12 mm long and its fundus lies 3-4 mm superior to the valve of Rosenmüller.42 The sac lies just anterior to the middle turbinate of the nose. The inferior sac is contiguous with the nasolacrimal duct which courses in the wall of the lateral nose and empties via the valve of Hasner just below the inferior turbinate. The valve of Hasner may be imperforate in young infants, and is the most common site of nasolacrimal duct obstruction in this age group.

The Nerves of the Orbit

The optic nerve: The optic nerve (the second cranial nerve) is actually part of the central nervous system, extending directly from the brain into the orbit. Like the rest of the central nervous system, the optic nerve is invested within a dural sheath and leptomeninges, surrounded by cerebrospinal fluid, and in part, is covered with myelin. The fact that cerebrospinal fluid surrounding the optic nerve communicates with the fluid surrounding the cerebrum and brainstem is the basis for the seizures and life-threatening cardiopulmonary depression which can occur with

inadvertent perforation of the optic nerve sheath during retrobulbar anesthesia.43

There are four major segments to the optic nerve, including the intracranial, intracanalicular, intraorbital and the intraocular segments. The intracanalicular segment of the optic nerve is tightly surrounded by its dural sheath and tethered within the bone. Because of this, the intracanalicular segment of the optic nerve is particularly susceptible to blunt trauma.44, 45 Once it passes through the optic foramen, the length of the intraorbital portion of the nerve is roughly 24-30 mm as it traverses the 20 mm or so distance to the globe. Thus, the nerve has a slightly serpentine course inside the orbit that allows for movement of the globe and some degree of proptosis. However, severe proptosis puts the nerve on stretch, described radiographically as “globe tenting”.46 The intraocular length of the nerve is approximately 1 mm.

Sensory innervation of the orbit: Sensory innervation of the periorbital region is carried by the ophthalmic and maxillary divisions of the trigeminal nerve (fifth cranial nerve). Both branch from the trigeminal ganglion which is located within the lateral wall of the cavernous sinus.

The ophthalmic branch further subdivides into three segments: the frontal, lacrimal and nasociliary nerves. The frontal and lacrimal branches enter the

Figure 1.16: The lacrimal drainage system

orbit in the superolateral part of the superior orbital fissure, outside the annulus of Zinn. The frontal nerve courses through the extraconal fat and separates in the anterior orbit into several smaller branches including the supraorbital branch which supplies the scalp, forehead, upper lid, and conjunctiva. The supraorbital nerve exits via the supraorbital notch or foramen and should be carefully avoided during dissection of the superior orbital rim. Injury to the deep, lateral branches of the supraorbital nerve which run beneath the frontalis muscle, as can occur during forehead lift surgery leads to scalp numbness to the vertex.47 The other major division of the frontal nerve, the supratrochlear nerve, exits just above the trochlea to innervate parts of the lower forehead and medial canthal region. The lacrimal nerve travels with the lacrimal artery superolaterally in the extraconal space, along the superior border of the lateral rectus (Figure 1.17). As it travels forward, it is joined by parasympathetic motor fibers within the orbit which began within the nervus intermedius and which

Applied Anatomy of Orbit 15

supply the lacrimal gland, superolateral lid and conjunctiva.37

The nasociliary nerve enters the orbit via the superior orbital fissure within the annulus of Zinn, traversing just under the superior rectus muscle and over the optic nerve medially as it courses forward in the orbit in association with the ophthalmic artery. In the posterior orbit, it subdivides into long posterior ciliary nerves which run medially and laterally toward the globe, giving off sensory fibers which travel through the ciliary ganglion without synapsing. The long ciliary nerves enter the sclera and continue forward, innervating the iris, cornea and ciliary muscles. Additional fibers from the nasociliary nerve travel superomedially and are responsible for sensation from the nasal mucosa and the skin on the medial tip of the nose via the anterior ethmoidal nerve. It is this branch which is responsible for Hutchinson’s sign in cases of herpes zoster ophthalmicus. The final anterior branch of the nasociliary nerve is the infratrochlear nerve, which

16 Surgical Atlas of Orbital Diseases

traverses the orbital septum inferior to the trochlea to supply the medial eyelid skin, lacrimal sac and the caruncle.

The maxillary division of the trigeminal nerve exits the middle cranial fossa via the foramen rotundum to enter the pterygopalatine fossa. From here, the zygomatic branch enters the inferior orbit via the inferior orbital fissure. It further subdivides into the infraorbital, zygomaticotemporal, and zygomaticofacial nerves. The infraorbital nerve exits the orbit via the infraorbital notch or groove to supply the skin of the lower lid, cheek and medial upper lip (Figure 1.2). Injury to this nerve by fractures involving the orbital floor result in hypesthesia over these areas. The zygomaticotemporal and zygomaticofacial nerves provide sensory innervation to the lateral brow and lateral cheek, respectively.

Motor innervation of the orbit: Motor innervation to the orbit involves the oculomotor, trochlear and abducens nerves, or the third, fourth and sixth cranial nerves, respectively. The oculomotor nerve exits the brainstem medially, leaving its dural sheath to enter the superolateral aspect of the cavernous sinus. Here, it divides into superior and inferior divisions which both pass into the orbit through the superior orbital fissure, within the annulus of Zinn. The superior division sends branches to the levator muscle and superior rectus while the inferior division branches into three parts to supply the medial rectus, inferior rectus and inferior oblique. The branch which innervates the inferior oblique also carries parasympathetic fibers which synapse in the ciliary ganglion. Thus, injury due to surgery or trauma to these inferior orbital structures can lead to an efferent pupillary defect and dilation.48

The trochlear nerve, the smallest and longest of the cranial nerves, arises from the dorsal midbrain, crosses the midline to emerge adjacent to the superior cerebellar peduncle. It enters the cavernous sinus along its lateral wall, reaching the orbit via the superior orbital fissure, above the annulus (along with the frontal and lacrimal nerves). It travels anteromedially above the levator just inferior to the periorbita, and enters the superior oblique at the muscle belly’s posterior third. The trochlear nerve is unique among the cranial nerves. It is the only cranial nerve innervating an extraocular muscle which does not penetrate the intraconal surface of the muscle it

serves. It is also the smallest cranial nerve, has the longest intracranial component, and is the only cranial nerve to exit dorsally from the brainstem. For these reasons, it is also the most prone to injury with closed head trauma.49

The abducens nerve originates from the pons and enters the cavernous sinus, initially following a course within the sinus near the internal carotid artery before coursing laterally along the wall. It passes into the orbit via the intra-annular portion of the superior orbital fissure, running along the inner surface of the lateral rectus and piercing the muscle belly at its posterior one-third. The intracranial course of the abducens nerve turns sharply as it crosses the petrosphenoidal ligament, making it particularly prone to injury50, 51 with acute increases50 or decreases52 in intracranial pressure.

Sympathetic innervation of the orbit: Sympathetics to the orbit which supply the iris dilator, eyelid muscle, eccrine sweat glands, and blood vessels originate from the superior cervical ganglion. These fibers travel along the internal carotid artery, through the cavernous sinus and into the orbit along the ophthalmic artery, via the superior orbital fissure. The sympathetics pass through the ciliary ganglion (located lateral to the optic nerve at the apex) without synapsing.12

Parasympathetic innervation of the orbit: Parasympathetics innervate the iris sphincter muscle, ciliary muscle, lacrimal gland and orbital blood vessels to produce miosis, lacrimation and relaxation of vascular tone. These inputs originate in the Edinger-Westphal nucleus (third cranial nerve), the salivatory nucleus via the nervus intermedius10 (the parasympathetic nerve fibers originating from the facial nerve), and the parasympathetic ganglia supporting the orbit. Preganglionic parasympathetics course with the oculomotor nerve, along its inferior division, and enter the orbit via the inferior orbital fissure. These fibers run superficially in the oculomotor nerve as it exits the brainstem adjacent to the posterior communicating artery. Thus, aneurysms of the posterior communicating artery may produce a third nerve palsy with an associated dilated pupil. These nerves synapse in the ciliary ganglion and enter the globe as the short posterior ciliary nerves.

The ciliary ganglion lies adjacent to the lateral aspect optic nerve at the orbital apex. The ganglion also contains sympathetics that travel into the orbit via the ophthalmic artery to reach the iris dilator and ocular blood vessels, as well as sensory fibers from the nasociliary nerve which supply intraocular structures. Neither the sympathetics nor the sensory fibers synapse within the ganglion.

Preganglionic fibers from the facial nerve nucleus pass through the geniculate ganglion and then travel with the greater petrosal nerve to eventually synapse within the pterygopalatine ganglion. These fibers course via the infraorbital fissure to the orbit and directly to the lacrimal gland.37, 38 Additional postganglionic fibers travel along branches of the maxillary division of the trigeminal nerve that converge with the lacrimal nerve to enter the orbit.

Applied Anatomy of Orbit 17

Vascular Anatomy of the Orbit: Arterial Supply

The ophthalmic artery, the first intracranial branch from the internal carotid artery, provides most of the blood supply to the orbit and globe. The ophthalmic artery arises just as its parent vessel exits the cavernous sinus, just inferior to the optic nerve and posterior to the anterior clinoid process. It immediately joins the optic nerve along its inferolateral surface, traveling within a common dural sheath, and entering the apex via the optic foramen.53, 54 Once inside the orbit, the artery crosses medially and gives off its major apical branches (Figure 1.18).

The major intraconal vessels include the central retinal artery, branches to the extraocular muscles, and the long and short posterior ciliary arteries. The first branch of the ophthalmic artery is the central

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retinal artery. This vessel typically pierces the nerve inferomedially, at a point approximately 10 mm from the globe, and as it reaches the globe, gives off the end arteries to the retina. Branches to the extraocular muscles show greater individual variation in distribution. Generally, these vessels run within the muscle belly or along their medial surfaces. As they continue to travel anteriorly with the muscles, the terminal branches of these arteries enter the globe at the tendinous muscle insertions, becoming the anterior ciliary arteries. These branches provide anastomoses with the long posterior ciliary arteries to supply the iris, ciliary muscle and other anterior intraocular structures. Because of this contribution of the muscular arteries to the anterior segment, disinserting more than two extraocular muscles from the globe during surgery at one time is generally avoided.

Typically, there are two or three posterior ciliary arteries which branch from the ophthalmic artery near the apex and run medially and laterally within the orbit. Some of these vessels divide into 15-20 short posterior ciliary arteries which enter the posterior aspect of the sclera to supply the choroid and the optic nerve head. Others, the two long posterior ciliary arteries, continue to travel anteriorly within the sclera, entering the globe medially and laterally to supply the anterior segment and anastomosing with terminal branches of the muscular arteries.

The major extraconal, apical branches of the ophthalmic artery include the lacrimal and posterior ethmoidal arteries. The lacrimal artery, along with the lacrimal nerve, runs above the superior border of the lateral rectus to reach the lacrimal gland and lateral upper lid. It anastomoses with the middle meningeal artery via the recurrent meningeal artery, and the temporal arteries. The posterior ethmoidal courses medially, along the frontoethmoidal suture to exit via the posterior ethmoid foramen where it gives off branches supplying the sinus and nasal mucosa and the frontal dura.54, 55

As the ophthalmic artery continues forward in the orbit, it then gives rise to the anterior ethmoidal artery and finally, its terminal branches. The anterior ethmoidal vessel exits via the anterior ethmoidal foramen to supply frontal dura and ethmoid and frontal sinus mucosa. Anastomoses from this circulation and branches of the external carotid

provide blood flow to the nose and septum. The frontoethmoidal suture, along which the anterior and posterior ethmoidal arteries and associated branches of the nasociliary nerve run, is an important landmark for the roof of the ethmoid, or fovea ethmoidalis which lies just beyond this line. Penetration of the medial wall above this suture would allow communication between the anterior cranial fossa and the orbit. Additionally, the posterior ethmoidal foramen characteristically lies 6 mm anterior to the optic canal and 12 mm posterior to the anterior ethmoidal foramen.2

The terminal branches of the ophthalmic artery are the supraorbital, supratrochlear, dorsal nasal and the medial palpebral arteries. The supraorbital and supratrochlear arteries provide the blood supply to the forehead and medial lids, while the dorsal nasal and medial palpebral arteries supply the medial lids and nose. The supraorbital artery travels above the levator via the supraorbital notch or foramen and should be carefully avoided during surgical dissection of the orbital roof. All of these vessels anastomose extensively with external carotid branches to the face.

It is clear that there is great degree of collateral flow to the orbit and lids between the internal and external carotid circulation. Therefore, a review of relevant branches of the external carotid artery, namely branches of the maxillary artery, is also important. Superiorly, the superficial temporal artery provides blood supply to the forehead, anastomosing with the circulation of the supraorbital and suprotrochlear arteries. The angular artery provides anastomoses with the dorsal nasal and palpebral arteries medially. Within the orbit itself, the sphenopalatine artery, like the ethmoidal circulation, supplies the nasosinus mucosa and nasal septum. The superficial branches of the infraorbital artery anastomose with the inferomedial palpebral arteries, while the deeper branches anastomose with the muscular arteries. The anastomosis between the lacrimal artery and the middle meningeal artery has already been discussed. This occurs via the recurrent meningeal artery, which enters the orbit through the sphenoid, through a foramen superolateral to the superior orbital fissure or directly via the fissure itself.2

Vascular Anatomy of the Orbit: Venous Outflow

The venous drainage pathways of the orbit run independently of the arteries and are a completely valveless system. There are three major outflow systems, involving the cavernous sinus, pterygoid plexus, and an anterior venous system which drains via the facial vein (Figure 1.19). The superior ophthalmic vein provides outflow from the superifical, superior periorbital and orbital regions, via the supraorbital, nasofrontal and angular veins. It can be divided into three segments as it runs anterior-posteriorly. The first segment courses adjacent to the trochlea and along the medial edge of the superior rectus. The second passes inferior to the muscle and into the cone. This segment receives the ciliary and superior vortex veins from the globe. The third portion of the superior orbital vein travels

Applied Anatomy of Orbit 19

along the lateral edge of the superior rectus and exits the orbit via the extra-annular superior orbital fissure to drain into the cavernous sinus.

The inferior ophthalmic vein drains the inferior orbit, including tributaries from the inferior rectus and oblique muscles and from the inferior vortex veins. The inferior ophthalmic vein anastomoses with a branch of the superior ophthalmic vein. A portion of the outflow is directed into the pterygoid plexus and the rest directly into the cavernous sinus. Anteromedially, venous drainage occurs mainly via the angular and facial veins. Because of the high degree of anastamoses and absence of valves, some degree of venous obstruction can be redirected within the system. However, acute thromboses, particularly of the cavernous sinus, cause marked orbital congestion and subsequently, exophthalmos.

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Paranasal Sinuses

There are four pairs of paranasal sinuses: the frontal, ethmoid, sphenoid and maxillary sinuses which directly neighbor the orbital roof, medial wall, and floor. Knowledge of their anatomy is useful since these spaces can share disease processes with the orbit such as infection and tumors, and can also provide surgical access to the orbit and lacrimal system.

The frontal sinus overlies the anterior portion of the orbital roof and drains into the frontonasal duct which travels though the anterior portion of the ethmoid sinus (ethmoid infundibulum) to empty into the middle meatus within the nose. This sinus develops in childhood and is usually difficult to appreciate radiographically until age 7 or so. Pneumatization is typically completed by early adulthood.56 The frontal sinus is a common site for mucocele formation.57

The ethmoid sinuses lie between the medial orbital walls and immediately posterior to the nose. The lateral wall of this sinus is comprised of the very thin lamina papyracea, which is easily fractured in surgery or trauma, or compromised by local infection. A frequent source of orbital cellulitis is ethmoid sinusitis which spreads secondarily. The ethmoid roof, or fovea ethmoidalis, is located just beneath the anterior cranial fossa and just medial to the frontoethmoidal suture line within the orbit. The most medial portion of the ethmoid roof is the cribriform plate, which overlies the nasal cavity (Figure 1.20). The sinuses themselves are comprised of many individual, thin-walled air cells and can be

Figure 1.20: Computed axial tomography illustrating the relationship between the anterior cranial fossa, orbit and ethmoid sinus

divided into three groups. The anterior and middle air cells drain into the middle meatus while the posterior air cells empty into the superior meatus of the nose. In performing dacryocystorhinostomy to create a passage between the lacrimal sac and nose, the ethmoid air cells are frequently encountered extending anterior to the posterior lacrimal crest.58,59

The sphenoid sinuses are located midsagittally and posterior to the ethmoid air cells. Like the frontal sinuses, they pneumatize relatively late in life and do not reach full size until adolescence. Drainage occurs via the sphenoethmoid recess located in the anterior sinus wall. Because the contents of the orbital apex and nearby cavernous sinus exit the orbit through the sphenoid bone, the walls of the sphenoid lie in close proximity to a number of critical structures. Anteriorly and superolaterally, the optic nerve and intracavernous portion of the internal carotid artery run along the lateral sinus walls. Severe sphenoid sinusitis can therefore cause optic nerve injury.60 Likewise, congenital dysplasia of the sphenoid, as can occur in neurofibromatosis type 1, can produce pulsatile proptosis.61, 62 The sphenoid sinus also provides a useful surgical approach to the pituitary fossa which is located posteriorly to the sinus.63

The maxillary sinus underlies the orbital floor and is the largest of the paranasal sinuses. Drainage from this sinus occurs via the maxillary ostium into the middle meatus. The ostium is located high within the medial sinus wall, close to the level of the orbital floor. Thus, trauma to the orbital floor (i.e. orbital fracture or inferomedial decompression) can obstruct drainage from the sinuses. Inside the medial walls of the maxillary sinus, lie the bony nasolacrimal canals. The posterior most aspect of the sinus extends from the area of the infraorbital fissure, and the infraorbital nerve and artery run along the maxillary roof within the infraorbital canal. Behind the maxillary sinus is located the pterygopalatine fossa and the maxillary artery runs in its posterior wall.

Conclusion

The orbit and its surrounds represent a complex anatomical space, incorporating critical ocular, neural, and vascular structures. The purpose of this chapter has been to provide an overview of orbital anatomy, as well as basic anatomy of the eyelids, lacrimal

system, and paranasal sinuses. A detailed understanding of this anatomy is fundamental to oculoplastic surgery and the management of orbital disease.

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