2.2.1 The Eyelid Skin

The eyelid skin is the thinnest in the body and unique in having no subcutaneous fat (Fig. 2‑6).

This, along with the color match, makes the upper eyelid an ideal donor site for a small full-thickness skin graft to be used for lower eyelid reconstruction. The skin can be removed easily and quickly and does not need to be thinned, unlike skin harvested from other donor sites. The surgeon must be careful to avoid causing lagophthalmos when using the upper eyelid as a skin graft donor site.

2.2.2 The Orbicularis Oculi Muscle

The orbicularis oculi muscle is divided anatomically into three parts (Fig. 2‑7):

1. 
   

   Orbital

   
   
2. 
   

   Preseptal

   
   
3. 
   

   Pretarsal

The orbital portion of the orbicularis muscle lies over the bony orbital margins. It arises from the frontal process of the maxillary bone in front of the anterior lacrimal crest, from the orbital process of the frontal bone, and from the medial canthal tendon. The fibers of the orbicularis pass around the orbital margins without interruption at the lateral canthus, and the bony insertions lie just below the points of origin.

The palpebral part of the orbicularis muscle extends from the orbital margins to the margins of the eyelids. The muscle fibers pass circumferentially around the eyelids and are fixed medially and laterally at the medial and lateral canthal tendons. The palpebral part of the orbicularis muscle is further subdivided into the preseptal and pretarsal orbicularis muscles.

The preseptal part of the orbicularis muscle lies over the orbital septum in the upper and lower eyelids. Its muscle fibers arise in a perpendicular fashion from the upper and lower borders of the medial canthal tendon. In the upper lid, the muscle arises by anterior and posterior heads. The anterior head is a broad extension from the superior surface of the common part of the medial canthal tendon. The posterior head arises from the superior arm and from the posterior arm of the medial canthal tendon. The inferior preseptal muscle arises as a single head from the whole length of the common medial canthal tendon.

The superior limb of the medial canthal tendon fuses to the fundus of the lacrimal sac by a layer of fibrovascular fascia (Fig. 2‑8). When the deep head of the preseptal muscle pulls on the lacrimal sac via this fascia, it contributes to the lacrimal pump mechanism. The preseptal muscles extend in an arc around the eyelids and insert along the lateral horizontal raphe.

The pretarsal orbicularis muscle lies over the tarsal plates. The fibers of the muscle in both the upper and lower eyelids arise from the medial canthal tendon by means of superficial and deep heads. The superficial heads extend from the eyelid and continue anterior to the upper and lower limbs of the medial canthal tendons. The muscles thicken and surround the limbs of the medial canthal tendon and the canaliculi superiorly, anteriorly, and inferiorly. Contraction of these muscle fibers also contributes to the lacrimal pump mechanism.

Close to the common canaliculus, the deep heads of the pretarsal orbicularis muscle fuse together to form a prominent bundle of muscle fibers referred to as Horner’s muscle, which extends just behind the posterior limb of the medial canthal tendon (Fig. 2‑8). Horner’s muscle continues posteriorly to insert onto the posterior lacrimal crest immediately behind the posterior limb of the medial canthal tendon. A few fibers continue more posteriorly 3 to 5 mm along the medial orbital wall. As Horner’s muscle passes to the posterior lacrimal crest, it is joined by the medial horn of the levator aponeurosis, the posterior layer of the orbital septum, and the medial rectus check ligament.

The pretarsal orbicularis muscle fibers join together along the surface of the lateral canthal tendon and the lateral horizontal raphé. Additional bundles of thin muscle fibers run along the upper and lower eyelid margins. These are referred to as muscles of Riolan. These are firmly fixated to the tarsus. Medially these muscles insert into the puncta and ampullae of the lacrimal drainage system. Some deeper fibers pass posterior to the canaliculi and merge into the deep heads of the pretarsal orbicularis muscle. These muscle fibers run in various directions, unlike the rest of the orbicularis muscle.

Lying between the orbicularis muscle and the orbital septum–levator aponeurosis fascial complex is an avascular fascial plane composed of loose areolar tissue. This fascial plane extends to the margin of the eyelid as the gray line. The gray line itself marks the anatomical separation of the anterior skin muscle lamella from the posterior tarsoconjunctival lamella.

The postorbicularis fascial plane allows slight movement between the orbicularis muscle and the underlying orbital septum while maintaining an integrated lamellar structure. Disruption of the fibrous connections within the postorbicularis fascial plane during upper lid surgery results in an inferior slippage of the anterior lamella after anterior-approach levator advancement surgery or upper lid blepharoplasty surgery. This inferior slippage of the anterior lamella can be prevented by fixating the orbicularis muscle and skin edges to the levator aponeurosis with interrupted 7–0 Vicryl sutures during the skin closure at the end of the procedure.

A deep plane of fat lies posterior to the orbital part of the orbicularis muscle superiorly and inferiorly. The suborbicularis oculi fat (SOOF) lies over the inferior orbital margin. The retro-orbicularis oculi fat (ROOF) lies over the superior orbital margin (Fig. 2‑9).

2.2.3 The Orbital Septum

The orbital septum is a fibrous multilayered membrane of variable thickness that arises from the arcus marginalis, a line of periosteal condensation, along the superior and inferior orbital margins. This is demonstrated in Video 2.1 with a lower lid transconjunctival blepharoplasty. In young patients, the orbital septum is usually relatively thick and quite easily identified at surgery (Fig. 2‑10).

In contrast, the orbital septum may be very thin and dehiscent in older patients. The orbital septum is continuous with the inner layers of the periorbita. Within the orbit the periorbita lines the bony orbital walls and is composed of an outer layer of periosteum and an inner layer continuous with the orbital fascia. These layers separate at the arcus marginalis, with the outer periosteum continuing over the orbital margins as the periosteum of the forehead and facial bones. In the upper eyelid the inner fascial layer separates into two further layers at the arcus marginalis. The superficial layer continues over the brow, where it is continuous with the deep fascia over the frontalis muscle and the galea aponeurotica above the eyebrow. The deep layer becomes the orbital septum in the upper eyelid. In the lower eyelid the inner fascial layer extends into the eyelid as the orbital septum (Fig. 2‑11).

Laterally the orbital septum inserts into the lateral canthal tendon and also passes behind the tendon inserting onto the lateral retinaculum together with the lateral horn of the levator aponeurosis. In the superomedial aspect of the orbit the orbital septum extends inferiorly and posteriorly along the posterior lacrimal crest. Here it inserts just posterior to Horner’s muscle and the posterior limb of the medial canthal tendon. The orbital septum passes around the lip of the lacrimal foramen, where it fuses to the lacrimal sac fascia (Fig. 2‑12). The inferior orbital septum joins the superior orbital septum medially at the anterior lacrimal crest.

Superomedially at the orbital margin the orbital septum thins and becomes dehiscent, allowing for the passage of the infratrochlear neurovascular bundle and branches of the superior ophthalmic vein. In the central aspect of the upper lid, the inferior aspect of the orbital septum fuses with the anterior surface of the levator aponeurosis. The point at which the orbital septum fuses with the levator aponeurosis varies from a position approximately 3 to 5 mm above the superior aspect of the tarsal plate to as far as 10 to 15 mm above the tarsal plate. In the lower eyelid, the orbital septum fuses with the capsulopalpebral fascia a few millimeters below the inferior aspect of the tarsal plate. This common fascial sheet then inserts into the lower edge of the inferior tarsal plate.

The orbital septum can be readily identified during surgery by noting the firm resistance to traction applied to it because of its attachment to the arcus marginalis. The preaponeurotic fat pads lie immediately posterior to the orbital septum in the upper and lower eyelids. It is extremely important not to confuse an extension of the brow fat pad into the postorbicularis fascial plane of the upper eyelid with the preaponeurotic fat pads. The orbital septum may be incorrectly identified as the levator aponeurosis in such patients, and an inadvertent advancement of this septal layer will result in marked lagophthalmos. Likewise, it is important not to advance the capsulopalpebral fascia in the lower eyelid without first separating the orbital septum to prevent a resultant lower eyelid retraction. The orbital septum must not be sutured after eyelid surgery; this would result in inadvertent shortening, resulting in lagophthalmos or eyelid retraction.

If the capsulopalpebral fascia is advanced in the lower eyelid without first opening the orbital septum, lower eyelid retraction may result.

2.2.4 Tarsal Plates

The tarsal plates are made up of dense fibrous tissue that provides the main structural integrity to the eyelids. The upper and lower tarsal plates are approximately 25 mm in length horizontally and are gently curved. They are approximately 1 to 1.5 mm thick; centrally the vertical height of the tarsal plate varies from 8 to 12 mm in the upper lid and 3.5 to 4 mm in the lower eyelid. The medial and lateral aspects of the tarsal plates taper to 2 mm high as they pass into the medial and lateral canthal tendons. A row of approximately 25 meibomian glands lie within the upper lid tarsus, and approximately 20 are positioned in the lower tarsus. The meibomian glands are multilobulated holocrine sebaceous glands that empty into a tiny central duct. The duct opens onto the posterior eyelid margin behind the gray line. These glands produce the lipid layer of the precorneal tear film.

2.2.5 Canthal Tendons

The tarsal plates continue into fibrous bands medially and form the crura of the medial canthal tendon. These crura lie between the orbicularis muscle anteriorly and the conjunctiva posteriorly. The superior and inferior crura fuse to form a common medial canthal tendon. This tendon inserts onto the adjacent bones by means of three arms: the anterior, posterior, and superior arms. The anterior arm inserts onto the orbital process of the maxillary bone anterior and above the anterior lacrimal crest (Fig. 2‑12).

The width of the tendon on insertion is approximately 4 to 5 mm. The anterior arm provides the main support for the medial canthal angle. The posterior arm arises from the common tendon close to the junction of the superior and inferior crura and passes posteriorly between the superior and inferior canaliculi. The posterior arm continues along the posterolateral aspect of the lacrimal sac. It continues posteriorly, fanning out to form a broad sheet between 6 and 9 mm in vertical height. The posterior arm inserts onto the posterior lacrimal crest just anterior to Horner’s muscle. The posterior arm serves to direct the vector forces of the canthal angle posteriorly to maintain a close apposition of the lids to the globe.

The superior arm of the medial canthal tendon originates at the anterior and posterior arms and passes superiorly 7 to 10 mm, inserting onto the orbital process of the frontal bone (Fig. 2‑8). The superior arm may provide vertical support to the canthal angle and may also play a role in the lacrimal pump mechanism.

Laterally the tarsal plates extend into less-well-defined fibrous strands that become the superior and inferior crura of the lateral canthal tendon. The lateral canthal tendon measures approximately 5 to 7 mm long. It is approximately 3 mm wide at the point where the superior and inferior crura unite but broadens to approximately 6 to 7 mm as it inserts into the lateral orbital tubercle (Fig. 2‑13a) 1.5 mm inside the lateral orbital margin. The lateral horn of the levator aponeurosis blends with the superior border of the lateral canthal tendon. The lateral canthal tendon and the lateral horn of the levator aponeurosis extend superiorly to a position 4 to 5 mm below the frontozygomatic suture line, forming a broad tendon-like insertion (Fig. 2‑13b).

The inferior crus of the lateral canthal tendon is divided during the course of a lateral tarsal strip procedure and for a rapid orbital decompression for the management of an acute retrobulbar hemorrhage. Division of the superior crus of the lateral canthal tendon can be associated with significant morbidity because of the proximity of important adjacent structures (i.e., the lateral horn of the levator, Whitnall’s ligament, and the lacrimal gland; Fig. 2‑9).

The fibers of the crura continue posteriorly along the lateral orbital wall, fusing with fibers of the lateral check ligament. Along with the lateral canthal tendon complex, the inferolateral fibers of Whitnall’s superior suspensory ligament and the lateral portion of Lockwood’s inferior suspensory ligament insert onto the lateral tubercle, forming the lateral retinaculum (Fig. 2‑14).

A small lobule from the precapsulopalpebral fat pad extends superiorly between the orbital septum and the lateral canthal tendon. This is referred to as Eisler’s pocket. This is believed to act like a bursa, allowing some independent movement of the lateral canthal tendon during eyelid movement, particularly on lateral gaze.

2.2.6 Preaponeurotic Fat Pads

The preaponeurotic fat pads in the upper eyelid and the precapsulopalpebral fat pads in the lower eyelid are anterior extensions of the extraconal orbital fat. The fat pads are enveloped by thin fibrous sheaths that represent forward continuations of the anterior orbital septal system. The individual lobules of fat within the fat pockets are surrounded by fine interlobular septa. The fibrous sheaths surrounding the fat pads are connected to the overlying orbital septum and the underlying levator aponeurosis by very fine fibrous bands. The eyelid fat pads are important surgical landmarks that assist in the identification of the eyelid retractors, which lie immediately posterior to the fat pads (Fig. 2‑2).

In the upper eyelid, there are two fat pads: one medially and one centrally (Fig. 2‑15). These are separated by fine fascial bands, which are continuous with the trochlea. The medial fat pad is paler than the central fat pad and contains thicker and more abundant interlobular septa. In the lateral aspect of the upper eyelid, the lacrimal gland is located in the lacrimal gland fossa just posterior to the orbital margin (Fig. 2‑13b).

The lacrimal gland is isolated within its own fascial compartment. If this fascial support system of the lacrimal gland becomes loose, the gland may prolapse into the lateral aspect of the eyelid, where it must not be mistaken for preaponeurotic fat (Fig. 2‑16).

The appearance of the lacrimal gland is a quite distinctive pink color (Fig. 2‑17). It is also firm, unlike preaponeurotic fat.

There are three fat pads in the lower eyelid, each of which is separated by fibrous septa, which are continuous with the orbital connective tissue system (Fig. 2‑18).

The central and lateral fat pads are separated by a connective tissue band referred to as the arcuate expansion, which extends from Lockwood’s ligament to the inferolateral orbital margin (Fig. 2‑19).

The inferior oblique muscle runs between the medial and central fat pads (Fig. 2‑20).

2.2.7 Eyelid Retractors

The levator palpebrae superioris muscle arises from the lesser wing of the sphenoid bone just above the annulus of Zinn and superolateral to the optic canal (Fig. 2‑21).

The muscle is approximately 35 mm long. At its origin it is approximately 4 mm wide, broadening to approximately 8 mm in the midsection of the orbit. As the muscle passes forward, it lies in intimate contact with the superior rectus muscle (see Fig. 2‑2). The levator and the superior rectus muscles are connected by fine fibrous strands of the superior orbital fascial system. Extensive fibrous tissue strands connect the sheath of the levator muscle with the superior rectus muscle below and with the superior conjunctival fornix and Tenon’s capsule just behind Whitnall’s ligament.

These fibrous tissue strands function as check ligaments but permit coordinated movement of the upper eyelid with alterations in the vertical ocular gaze position. The levator muscle widens to approximately 18 mm just posterior to the superior orbital margin. In this location, a condensation of variable thickness and density is seen running along the muscle sheath in a horizontal direction. This is Whitnall’s superior transverse ligament (Fig. 2‑22).

Whitnall’s ligament attaches to the fascia adjacent to the trochlea medially and laterally inserts into the lacrimal gland capsule and the periorbita of the lower aspect of the frontal bone (Fig. 2‑14).

The ligament is firmly attached to the levator muscle sheath medially and laterally but only very loosely attached to the levator muscle centrally. A very thin sheet of fascia passes from Whitnall’s ligament to insert into the superior orbital margin.

Whitnall’s ligament appears to function as a check ligament against posterior movement of the levator and superior rectus muscles. Whitnall’s ligament forms a circumorbital fascial ring in conjunction with Lockwood’s ligament. During ptosis surgery Whitnall’s ligament should be maintained intact wherever possible. If Whitnall’s ligament is severed, the levator muscle prolapses. This loss of support results in the need for a greater resection than would otherwise be required. The ligament can also be used as an internal sling during ptosis surgery.

The levator muscle attaches to the fibrous levator aponeurosis in close proximity to Whitnall’s ligament (Fig. 2‑2). The levator aponeurosis continues inferiorly approximately 15 to 20 mm to inserts onto the superior two thirds of the anterior tarsal surface (Fig. 2‑2). Delicate fibers also continue forward from the levator aponeurosis to insert onto the septum of the pretarsal orbicularis muscle and the skin (Fig. 2‑2). The delicate fibers from the levator aponeurosis retract the pretarsal skin and muscle and orbicularis muscle, preventing an overhang of these structures on elevation of the eyelid. The superior limits of the attachment of these layers are marked by the upper lid skin crease. This relationship is disturbed by a dehiscence of the levator aponeurosis, which results in an apparent superior displacement of the upper lid skin crease (Fig. 2‑23).

The levator aponeurosis widens to form the medial and lateral levator horns as it passes inferiorly from Whitnall’s ligament (Fig. 2‑24).

The medial horn is more tenuous and accounts for a lateral shift of the superior tarsus in older patients. The surgeon must be careful to avoid causing further intraoperative damage to the medial horn, which will result in a further lateral shift of the superior tarsus and an unsatisfactory temporal displacement of the peak of the eyelid. The lateral horn, which is a better-defined structure, separates the lacrimal gland into orbital and palpebral lobes (Fig. 2‑25).

The lateral levator horn inserts onto the lateral orbital tubercle of the zygomatic bone at the level of the lateral retinaculum (Fig. 2‑14). It also joins with fibers of the capsulopalpebral fascia of the lower eyelid.

The medial horn of the levator aponeurosis inserts onto the posterior limb of the medial canthal tendon and the posterior lacrimal crest (Fig. 2‑24). The medial and lateral levator horns help to distribute the forces generated by the levator muscle along the levator aponeurosis, allowing the central aspect of the eyelid to elevate to the greatest extent. The lateral levator aponeurosis horn is severed during levator aponeurosis recession procedures undertaken for the management of thyroid-related eyelid retraction. In contrast, during surgery to advance to the levator aponeurosis for the management of a blepharoptosis, the levator horns should be preserved wherever possible.

Müller’s muscle is joined to the overlying levator aponeurosis by a very loose connective tissue layer. This avascular plane can usually be dissected easily during ptosis surgery procedures (Fig. 2‑26).

Müller’s muscle originates from the undersurface of the levator muscle at a point just distal to Whitnall’s ligament (Fig. 2‑2). Müller’s muscle runs inferiorly posterior to the levator aponeurosis. It is approximately 8 to 12 mm long and has a variable thickness of 0.1 to 0.5 mm. Müller’s muscle inserts onto the anterior edge of the superior border of the tarsus (Fig. 2‑2). There is a small fat pad within the medial aspect of the muscle that should not be mistaken for the fatty degeneration of the muscle seen with increased age and in patients with thyroid eye disease (Fig. 2‑27).

Müller’s muscle is innervated by sympathetic nerve fibers, which pass to the orbit via the internal carotid plexus. These sympathetic nerve fibers originate in the hypothalamus (Fig. 2‑28). Disruption of the sympathetic innervation of Müller’s muscle results in the ptosis seen in Horner’s syndrome.

In the lower eyelid, the capsulopalpebral fascia is a fibrous sheet that arises from Lockwood’s ligament and the inferior rectus and inferior oblique muscle sheaths (Fig. 2‑2). As it passes superiorly the fascia fuses with the orbital septum approximately 4 to 5 mm below the inferior border of the tarsal plate (Fig. 2‑2). From this position, a common fascial sheet passes superiorly and inserts onto the inferior border of the tarsus (Fig. 2‑2). Fine fibers pass anteriorly from this fascial sheet to the orbital septum and the skin creating the lower eyelid crease in a manner analogous to that of the upper eyelid.

Smooth muscle fibers analogous to Müller’s muscle in the upper eyelid lie posterior to the capsulopalpebral fascia, forming a very thin muscular layer (Fig. 2‑2). These fibers are also innervated by the sympathetic nervous system. For this reason, disruption of the sympathetic innervation of these muscle fibers results in the slight rise in the lower eyelid seen in Horner’s syndrome (Fig. 2‑29). A combination of the blepharoptosis and the rise in the lower eyelid is responsible for the apparent enophthalmos seen in patients with Horner’s syndrome.

2.2.8 Conjunctiva

The conjunctiva is a mucous membrane that can be arbitrarily divided into palpebral, forniceal, and bulbar portions. The palpebral portion is very closely attached to the posterior surface of the tarsus in the upper and lower eyelids, from which it cannot be separated. This portion is also in close approximation to Müller’s muscle in the upper lid and the equivalent smooth muscle fibers in the lower lid (Fig. 2‑3).

The palpebral portion continues into the forniceal portion. The superior fornix is situated approximately 10 mm above the superior corneal limbus. The superior fornix is supported by a fine fibrous suspensory ligament, which arises from the fascia of the levator muscle and the superior rectus muscle. The inferior fornix is situated approximately 8 mm below the inferior corneal limbus and is supported by a fine suspensory ligament that arises from Lockwood’s ligament. This is situated just posterior to the capsulopalpebral fascia and functions to retract the fornix inferiorly during downgaze.

The conjunctiva contains a series of small accessory lacrimal glands. Lymphatic blood vessels and sensory nerves run in the conjunctival submucosa. A small, elevated structure consisting of sebaceous glands, sweat glands, and fine hairs lies within the medial canthal angle. This is the caruncle. A vertical fold of conjunctiva, the plica semilunaris, lies just lateral to the caruncle. The medial wall of the orbit can be accessed via an incision made between these two structures (e.g., a transcaruncular approach to the drainage of a medial subperiosteal orbital abscess complicating orbital cellulitis).

2.2.9 Sensory Nerve Supply of the Eyelids

The sensory innervation of the eyelids is provided by branches of the ophthalmic and maxillary divisions of the trigeminal nerve. The upper eyelid is innervated by the supraorbital, supratrochlear, and lacrimal nerves (Fig. 2‑30).

The medial aspect of the upper and lower eyelids is supplied by the infratrochlear nerve. Branches of the infratrochlear nerve also supply parts of the adjacent eyebrow, forehead, and nose (Fig. 2‑30). The lateral aspect of the upper eyelid and temple is supplied by the zygomatico-temporal branch of the maxillary nerve (Fig. 2‑30). The central aspect of the lower eyelid is supplied by infraorbital nerve, a branch of the maxillary nerve, and the lateral aspect of the lower eyelid is supplied by the zygomaticofacial branch of the maxillary nerve. (A more detailed description of the periorbital sensory nerve supply is outlined later in this chapter.)

2.2.10 Vascular Supply to the Eyelids

The eyelids have a very rich blood supply with multiple anastomoses (Fig. 2‑31a).

The anterior lamellae of the eyelids are supplied by branches of the external carotid artery, namely the transverse facial, superficial temporal, and angular arteries in conjunction with multiple anastomoses with vessels passing through the orbit (Fig. 2‑31). The posterior lamellae of the eyelids are supplied by vascular arcades. In the upper eyelid, a marginal arcade runs horizontally about 2 mm above the eyelid margin (Fig. 2‑31). A more peripheral arcade runs along the superior border of the tarsus between the levator aponeurosis and Müller’s muscle (Fig. 2‑26 ; Fig. 2‑31b).

These arcades are supplied medially by the superior medial palpebral artery, a terminal branch of the ophthalmic artery; laterally the arcades are fed by the superior lateral palpebral artery, a branch of the lacrimal artery (Fig. 2‑31). (A more detailed description of the periorbital vascular supply is outlined later in this chapter.)

2.2.11 The Lymphatic Channels in the Eyelids

The lymphatic drainage channels are extensive and well developed and lie anterior to the orbital septum. Lymph from the lateral two thirds of the upper eyelid and the lateral one third of the lower eyelid drains laterally and inferiorly into the deep and superficial parotid and submandibular lymph nodes. Lymph from the medial one third of the upper eyelid and the medial two thirds of the lower eyelid drains medially and inferiorly into the anterior cervical lymph nodes (Fig. 2‑32). Extensive disruption of these lymphatic channels results in lymphedema.

2.5.1 The Bony Orbit

In an adult, the bony orbit is pyramidal in shape. The volume of the orbit in the average adult is approximately 30 cm³. The globe contributes approximately 7.5 cm³. The anterior entry to the orbit forms an approximate rectangle 4 cm in width by 3.5 cm in height. The widest dimension of the orbit is attained approximately 1 cm posterior to the anterior orbital margin. The anteroposterior axes of the orbits form a 45-degree angle between them. The lateral orbital walls form a 90-degree angle between them (Fig. 2‑39).

The dimensions of the orbit vary from patient to patient. For this reason, a surgeon cannot rely on any specific measurements as a guide to the precise location of the optic canal or of the superior orbital fissure. Great care should therefore be taken when injecting fat, for example, into the posterior orbit of an anophthalmic patient, because the cannula could penetrate the intracranial cavity.

The precise location of the anterior and posterior ethmoidal foramina cannot be determined accurately before surgical dissection. Therefore great care must be taken in undertaking dissections in the medial and posterior orbit during an orbital decompression procedure or during the exploration of a medial orbital wall blowout fracture. The inferior orbital fissure may lie within 10 to 15 mm of the anterior orbital margin. It should be noted that the floor of the orbit ends at the posterior wall of the maxillary sinus and does not extend to the apex of the orbit (Fig. 2‑40).

Related posts:

1 Surgical Principles 3 Lower Eyelid Entropion 13 The Use of Autologous Grafts in Ophthalmic Plastic Surgery 27 Zygomatic Complex Fractures 10 Eyelid and Periocular Tumors 23 Secondary Anophthalmic Socket Reconstruction

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