Seven bones contribute to the framework of each orbit. They are the maxilla, zygomatic, frontal, ethmoid, lacrimal, sphenoid, and palatine bones. Together they give the bony orbit the shape of a pyramid, with its wide base opening anteriorly onto the face, and its apex extending in a posteromedial direction. Completing the pyramid configuration are medial, lateral, superior, and inferior walls. The apex of the pyramidal-shaped bony orbit is the optic foramen, while the base is the orbital rim.The orbit communicates posteriorly with the anterior and middle cranial fossae and inferiorly with the pterygopalatine and infratemporalfossa.Orbital rim (4):It is formed by: Superiorly by the frontal bone; Medially by the frontal process of the maxilla; Inferiorly by the zygomatic process of the maxilla and the zygomatic bone; Laterally by the zygomatic bone, the frontal process of the zygomatic bone, and the zygomatic process of the frontal bone. Foramena related to the rim are:Supraorbital notches or foramina, transmitting the arteries and nerves of the same nameSupratrochlear notches transmitting the arteries and nerves of the same nameRoof of orbit (2): It is made up of the orbital part of the frontal bone with a small contribution from the lesser wing of the sphenoid bone that completes the roof posteriorly. Unique features of the superior wall include: anteromedially, the possible intrusion of part of the frontal sinus and the trochlear fovea, for the attachment of a pulley through which the superior oblique muscle passes (about midway between the supra-orbital notch and the frontolacrimal suture) anterolaterally, a depression (the lacrimalfossa) for the orbital part of the lacrimal gland. The lacrimal gland, located in the superolateral part of the orbit, receives its sensory innervation from the lacrimal nerve and its parasympathetic and sympathetic innervation from the greater and deep petrosal nerves. The petrosal nerves join to form the vidian nerve that enters the pterygopalatine ganglion, which sends branches to the zygomatic nerve that anastomoses with the lacrimal nerve to reach the gland.Floor of orbit (3):It is also the roof of the maxillary sinus, consists primarily of the orbital surface of the maxilla, with small contributions from the zygomatic and palatine bones. Posteriorly, the orbital process of the palatine bone makes a small contribution to the floor of the bony orbit near the junction of the maxilla, ethmoid, and sphenoid bones. Beginning posteriorly and continuing along the lateral boundary of the floor of the bony orbit is the inferior orbital fissure. Beyond the anterior end of the fissure the zygomatic bone completes the floor of the bony orbit.Beginning posteriorly and crossing about two-thirds of the inferior orbital fissure, a groove (the infra-orbital groove) is encountered, which continues anteriorly across the floor of the orbit. This groove connects with the infra-orbital canal that opens onto the face at the infra-orbital foramen. The infra-orbital nerve, a branch of the maxillary nerve [V2], and vessels pass through this structure from inferior orbital fissure to exit onto the face through the infraorbital foramen. Medial wall of orbit (4):The medial walls of the paired bony orbits are parallel to each other and each consists of four bones from anterior to posterior Maxilla (the frontal process of the maxilla): Lacrimal: both lacrimal bone and frontal process of maxilla participate in the formation of the lacrimal groove, which contains the lacrimal sac and is bound by the posterior lacrimal crest (part of the lacrimal bone) and the anterior lacrimal crest (part of the maxilla). Ethmoid: The largest contributor to the medial wall is the orbital plate of the ethmoid bone. This part of the ethmoid bone contains collections of ethmoid air cells, which are clearly visible in a dried skull. Also visible, at the junction between the roof and the medial wall, usually associated with the frontoethmoidal suture, are the anterior and posterior ethmoidal foramina. The anterior and posterior ethmoidal nerves and vessels leave the orbit through these openings. Sphenoid bones. Posterior to the ethmoid bone the medial wall is completed by a small part of the sphenoid bone, which forms a part of the medial wall of the optic canal. Lateral wall of orbit (2): It consists of contributions from two bones-anteriorly, the zygomatic bone and posteriorly, the greater wing of the sphenoid bone. It is separated posteriorly from roof of orbit by superior orbital fissure and separated from floor of orbit by inferior orbital fissure.The lacrimal foramen, which transmits the recurrent meningeal branch of the ophthalmic artery, is located anterior to the superior orbital fissure along the superior edge of the lateral wall. The zygomatico-orbital foramina on the anterolateral part of the intraorbital surface of the lateral wall transmit the zygomaticofacial and zygomaticotemporal nerves (branches of maxillary nerve) and exit the orbit external surface of the zygoma at the zygomaticofacial and zygomaticotemporal foramina to reach the skin of the cheek and temple.The optic canal:When the bony orbit is viewed from an anterolateral position, the round opening at the apex of the pyramidal-shaped orbit is the optic canal, which opens into the middle cranial fossa. It is a horizontal elliptical cavity at its cranial side, is circular in its midportion, and a vertical ellipse at the orbital side. The thickest part of optic canal is the distal end near the foramen (at the cranial side). Its dimension is about 4 × 6 (5-20) mm. The tendinous ring (annular tendon) from which the superior, inferior, medial, and lateral rectus muscles arise, is attached to the upper, lower, and medial margin of the optic canal.Its boundaries are:1) Lateral wall: is formed by Junction one of the two roots of the lesser wing of the sphenoid which also serves as the medial margin of the superior orbital fissure. 2) Medial wall: part of ethmoid and sphenoid sinus.3) Roof: formed by lesser wing. Its proximal end covered by falciform process (it is a fold of dura covering the optic nerve at the proximal end of the canal). Part that is covered only by dura in the canal is about 1 mm in length. The cranial dura is redundant at the cranial end of the optic canal where it forms the falciform ligament. It then traverses the canal where the outer layer is continuous with the periorbita, while the inner layer continues as the optic nerve sheath within the orbit. 4) floor: formed by union of optic strut into the sphenoid body.Its content: 1) the optic is superomedial to ophthalmic artery.2) Ophthalmic branch of the internal carotid artery, 3) Sympathetic plexus around the artery. Superior orbital fissure: The superior orbital fissure is located between the roof of orbit (lesser wing of the sphenoid bone) and lateral wall of orbit (greater wing of the sphenoid bone ) on the lateral side of the optic canal. From the orbital side the frontal bone forms a small portion of the lateral apical margin of the fissure, because the greater and lesser wings approach, but do not meet at the narrow lateral apex.It has a somewhat triangular shape, having a wide base medially on the sphenoid body and a narrow apex situated laterally between the lesser and greater wings. The fissure slopes gently downward from its lateral to medial border. The fissure is not oriented in a strictly coronal plane, but is directed forward so that the lateral apex is slightly forward of the medial margin. The junction of the upper and lower segments of the lateral edge (from the orbital side) is the site of a bony prominence that serves as the site of attachment of the lateral edge of the annular tendon, from which the four rectus muscles arise. This bony prominence can vary from narrow and pointed to broad and flat.Passing through the superior orbital fissure from the middle cranial fossa are 1) the superior and inferior branches of the oculomotor nerve [III], 2) the trochlear nerve [IV], 3) the abducent nerve [VI], 4) the lacrimal, frontal, and nasociliary branches of the ophthalmic nerve [V1], 5) the superior ophthalmic vein 6) A recurrent meningeal artery if presentThe annular tendon of Zinn, a fibrous ring that surrounds the central part of the superior orbital fissure and the optic canal, gives attachment to the superior, medial, inferior, and lateral rectus muscles. The superior oblique attaches above the annular tendon and the inferior oblique arises from the inferomedial orbital wall just behind the rim.Inferior orbital fissure; Itis a longitudinal opening separates the lateral wall of the orbit from the floor of the orbit. It is located between the greater sphenoid wing behind and the maxillary and palatine bones anteriorly. The narrow lateral end is formed by the zygomatic bone, and the narrow medial end is formed by the sphenoid body. It is closed by a fibrous tissue and orbital muscle. This long fissure allows communication between: 1) the orbit and the pterygopalatinefossa posteriorly; 2) the orbit and the infratemporalfossa in the middle; 3) the orbit and and the temporal fossaanteriorly. Passing through the inferior orbital fissure are the 1) The zygomatic and the infraorbital and zygomatic branches of the maxillary nerve,2) some branches of the internal maxillary artery, and the branches of the inferior ophthalmic vein, which communicate with the pterygoid plexus.The oculomotor foramen, located inside the annular tendon and through which the oculomotor nerve passes, is located between the upper and lower attachment of the lateral rectus muscle.Occulomotor nerve: Just before passing through the superior orbital fissure and the oculomotor foramen in the annular tendon, the oculomotor nerve divides into an upper division supplying the superior rectus and levator muscles and a lower division to the medial and inferior rectus and inferior oblique muscles. The oculomotor nerve gives rise to the parasympathetic motor root to theciliary ganglion that lies lateral to the optic nerve. The abducens nerve passes through the oculomotor foramen and enters the medial surface of the lateral rectus muscle. The ophthalmic nerve divides just behind the annular tendon into lacrimal and frontal nerves that pass outside the annular tendon, and the nasociliary nerve that passes through the annular tendon. The ophthalmic nerve gives rise to the long ciliary nerves and the sensory root to the ciliary ganglion; the former conveys the sympathetic pupillomotor fibers and the latter conveys corneal sensation.The trochlear nerve passes above and outside the superomedial edge of the annular tendon.The optic nerve passes superior and medial from the globe to reach the optic canal and divides the retro-orbital space into medial and lateral parts.The maxillary nerve passes through the foramen rotundum to enter the pterygopalatinefossa, where it gives rise the infraorbital and zygomatic nerves and communicating rami to the sphenopalatine ganglion. The infraorbital and zygomatic branches pass through the inferior orbital fissure to course within the orbit. The infraorbital nerve courses along the orbital floor in the infraorbital groove and canal to reach the infraorbital foramen, where its branches are distributed to the cheek. The zygomatic branch passes through the inferior orbital fissure and courses just inside the lateral wall of the orbit, where it divides into zygomaticofacial and zygomaticotemporal branches. These branches enter the zygomatico-orbital foramina on the intraorbital surface of the zygoma and exit the zygoma at the zygomaticofacial and zygomaticotemporal foramina to reach the skin of the cheek and temple, respectively. The main arterial supply to the orbit is by the ophthalmic artery and its branches. This artery courses below the optic nerve in the optic canal, crosses to the lateral side of the nerve at the orbital apex, and then courses from lateral to medial above the optic nerve. The main branches are the central retinal artery and the lacrimal, ciliary, ethmoidal, supraorbital, and dorsal nasal arteries, plus numerous muscular branches. The main venous drainage of the orbit is through the superior and inferior ophthalmic veins that exit the orbit by passing outside the annular tendon and through the superior orbital fissure.
Seven bones contribute to the framework of each orbit. They are the maxilla, zygomatic, frontal, ethmoid, lacrimal, sphenoid, and palatine bones. Together they give the bony orbit the shape of a pyramid, with its wide base opening anteriorly onto the face, and its apex extending in a posteromedial direction. Completing the pyramid configuration are medial, lateral, superior, and inferior walls. The apex of the pyramidal-shaped bony orbit is the optic foramen, while the base is the orbital rim.The orbit communicates posteriorly with the anterior and middle cranial fossae and inferiorly with the pterygopalatine and infratemporalfossa.Orbital rim (4):It is formed by: Superiorly by the frontal bone; Medially by the frontal process of the maxilla; Inferiorly by the zygomatic process of the maxilla and the zygomatic bone; Laterally by the zygomatic bone, the frontal process of the zygomatic bone, and the zygomatic process of the frontal bone. Foramena related to the rim are:Supraorbital notches or foramina, transmitting the arteries and nerves of the same nameSupratrochlear notches transmitting the arteries and nerves of the same nameRoof of orbit (2): It is made up of the orbital part of the frontal bone with a small contribution from the lesser wing of the sphenoid bone that completes the roof posteriorly. Unique features of the superior wall include: anteromedially, the possible intrusion of part of the frontal sinus and the trochlear fovea, for the attachment of a pulley through which the superior oblique muscle passes (about midway between the supra-orbital notch and the frontolacrimal suture) anterolaterally, a depression (the lacrimalfossa) for the orbital part of the lacrimal gland. The lacrimal gland, located in the superolateral part of the orbit, receives its sensory innervation from the lacrimal nerve and its parasympathetic and sympathetic innervation from the greater and deep petrosal nerves. The petrosal nerves join to form the vidian nerve that enters the pterygopalatine ganglion, which sends branches to the zygomatic nerve that anastomoses with the lacrimal nerve to reach the gland.Floor of orbit (3):It is also the roof of the maxillary sinus, consists primarily of the orbital surface of the maxilla, with small contributions from the zygomatic and palatine bones. Posteriorly, the orbital process of the palatine bone makes a small contribution to the floor of the bony orbit near the junction of the maxilla, ethmoid, and sphenoid bones. Beginning posteriorly and continuing along the lateral boundary of the floor of the bony orbit is the inferior orbital fissure. Beyond the anterior end of the fissure the zygomatic bone completes the floor of the bony orbit.Beginning posteriorly and crossing about two-thirds of the inferior orbital fissure, a groove (the infra-orbital groove) is encountered, which continues anteriorly across the floor of the orbit. This groove connects with the infra-orbital canal that opens onto the face at the infra-orbital foramen. The infra-orbital nerve, a branch of the maxillary nerve [V2], and vessels pass through this structure from inferior orbital fissure to exit onto the face through the infraorbital foramen. Medial wall of orbit (4):The medial walls of the paired bony orbits are parallel to each other and each consists of four bones from anterior to posterior Maxilla (the frontal process of the maxilla): Lacrimal: both lacrimal bone and frontal process of maxilla participate in the formation of the lacrimal groove, which contains the lacrimal sac and is bound by the posterior lacrimal crest (part of the lacrimal bone) and the anterior lacrimal crest (part of the maxilla). Ethmoid: The largest contributor to the medial wall is the orbital plate of the ethmoid bone. This part of the ethmoid bone contains collections of ethmoid air cells, which are clearly visible in a dried skull. Also visible, at the junction between the roof and the medial wall, usually associated with the frontoethmoidal suture, are the anterior and posterior ethmoidal foramina. The anterior and posterior ethmoidal nerves and vessels leave the orbit through these openings. Sphenoid bones. Posterior to the ethmoid bone the medial wall is completed by a small part of the sphenoid bone, which forms a part of the medial wall of the optic canal. Lateral wall of orbit (2): It consists of contributions from two bones-anteriorly, the zygomatic bone and posteriorly, the greater wing of the sphenoid bone. It is separated posteriorly from roof of orbit by superior orbital fissure and separated from floor of orbit by inferior orbital fissure.The lacrimal foramen, which transmits the recurrent meningeal branch of the ophthalmic artery, is located anterior to the superior orbital fissure along the superior edge of the lateral wall. The zygomatico-orbital foramina on the anterolateral part of the intraorbital surface of the lateral wall transmit the zygomaticofacial and zygomaticotemporal nerves (branches of maxillary nerve) and exit the orbit external surface of the zygoma at the zygomaticofacial and zygomaticotemporal foramina to reach the skin of the cheek and temple.The optic canal:When the bony orbit is viewed from an anterolateral position, the round opening at the apex of the pyramidal-shaped orbit is the optic canal, which opens into the middle cranial fossa. It is a horizontal elliptical cavity at its cranial side, is circular in its midportion, and a vertical ellipse at the orbital side. The thickest part of optic canal is the distal end near the foramen (at the cranial side). Its dimension is about 4 × 6 (5-20) mm. The tendinous ring (annular tendon) from which the superior, inferior, medial, and lateral rectus muscles arise, is attached to the upper, lower, and medial margin of the optic canal.Its boundaries are:1) Lateral wall: is formed by Junction one of the two roots of the lesser wing of the sphenoid which also serves as the medial margin of the superior orbital fissure. 2) Medial wall: part of ethmoid and sphenoid sinus.3) Roof: formed by lesser wing. Its proximal end covered by falciform process (it is a fold of dura covering the optic nerve at the proximal end of the canal). Part that is covered only by dura in the canal is about 1 mm in length. The cranial dura is redundant at the cranial end of the optic canal where it forms the falciform ligament. It then traverses the canal where the outer layer is continuous with the periorbita, while the inner layer continues as the optic nerve sheath within the orbit. 4) floor: formed by union of optic strut into the sphenoid body.Its content: 1) the optic is superomedial to ophthalmic artery.2) Ophthalmic branch of the internal carotid artery, 3) Sympathetic plexus around the artery. Superior orbital fissure: The superior orbital fissure is located between the roof of orbit (lesser wing of the sphenoid bone) and lateral wall of orbit (greater wing of the sphenoid bone ) on the lateral side of the optic canal. From the orbital side the frontal bone forms a small portion of the lateral apical margin of the fissure, because the greater and lesser wings approach, but do not meet at the narrow lateral apex.It has a somewhat triangular shape, having a wide base medially on the sphenoid body and a narrow apex situated laterally between the lesser and greater wings. The fissure slopes gently downward from its lateral to medial border. The fissure is not oriented in a strictly coronal plane, but is directed forward so that the lateral apex is slightly forward of the medial margin. The junction of the upper and lower segments of the lateral edge (from the orbital side) is the site of a bony prominence that serves as the site of attachment of the lateral edge of the annular tendon, from which the four rectus muscles arise. This bony prominence can vary from narrow and pointed to broad and flat.Passing through the superior orbital fissure from the middle cranial fossa are 1) the superior and inferior branches of the oculomotor nerve [III], 2) the trochlear nerve [IV], 3) the abducent nerve [VI], 4) the lacrimal, frontal, and nasociliary branches of the ophthalmic nerve [V1], 5) the superior ophthalmic vein 6) A recurrent meningeal artery if presentThe annular tendon of Zinn, a fibrous ring that surrounds the central part of the superior orbital fissure and the optic canal, gives attachment to the superior, medial, inferior, and lateral rectus muscles. The superior oblique attaches above the annular tendon and the inferior oblique arises from the inferomedial orbital wall just behind the rim.Inferior orbital fissure; Itis a longitudinal opening separates the lateral wall of the orbit from the floor of the orbit. It is located between the greater sphenoid wing behind and the maxillary and palatine bones anteriorly. The narrow lateral end is formed by the zygomatic bone, and the narrow medial end is formed by the sphenoid body. It is closed by a fibrous tissue and orbital muscle. This long fissure allows communication between: 1) the orbit and the pterygopalatinefossa posteriorly; 2) the orbit and the infratemporalfossa in the middle; 3) the orbit and and the temporal fossaanteriorly. Passing through the inferior orbital fissure are the 1) The zygomatic and the infraorbital and zygomatic branches of the maxillary nerve,2) some branches of the internal maxillary artery, and the branches of the inferior ophthalmic vein, which communicate with the pterygoid plexus.The oculomotor foramen, located inside the annular tendon and through which the oculomotor nerve passes, is located between the upper and lower attachment of the lateral rectus muscle.Occulomotor nerve: Just before passing through the superior orbital fissure and the oculomotor foramen in the annular tendon, the oculomotor nerve divides into an upper division supplying the superior rectus and levator muscles and a lower division to the medial and inferior rectus and inferior oblique muscles. The oculomotor nerve gives rise to the parasympathetic motor root to theciliary ganglion that lies lateral to the optic nerve. The abducens nerve passes through the oculomotor foramen and enters the medial surface of the lateral rectus muscle. The ophthalmic nerve divides just behind the annular tendon into lacrimal and frontal nerves that pass outside the annular tendon, and the nasociliary nerve that passes through the annular tendon. The ophthalmic nerve gives rise to the long ciliary nerves and the sensory root to the ciliary ganglion; the former conveys the sympathetic pupillomotor fibers and the latter conveys corneal sensation.The trochlear nerve passes above and outside the superomedial edge of the annular tendon.The optic nerve passes superior and medial from the globe to reach the optic canal and divides the retro-orbital space into medial and lateral parts.The maxillary nerve passes through the foramen rotundum to enter the pterygopalatinefossa, where it gives rise the infraorbital and zygomatic nerves and communicating rami to the sphenopalatine ganglion. The infraorbital and zygomatic branches pass through the inferior orbital fissure to course within the orbit. The infraorbital nerve courses along the orbital floor in the infraorbital groove and canal to reach the infraorbital foramen, where its branches are distributed to the cheek. The zygomatic branch passes through the inferior orbital fissure and courses just inside the lateral wall of the orbit, where it divides into zygomaticofacial and zygomaticotemporal branches. These branches enter the zygomatico-orbital foramina on the intraorbital surface of the zygoma and exit the zygoma at the zygomaticofacial and zygomaticotemporal foramina to reach the skin of the cheek and temple, respectively. The main arterial supply to the orbit is by the ophthalmic artery and its branches. This artery courses below the optic nerve in the optic canal, crosses to the lateral side of the nerve at the orbital apex, and then courses from lateral to medial above the optic nerve. The main branches are the central retinal artery and the lacrimal, ciliary, ethmoidal, supraorbital, and dorsal nasal arteries, plus numerous muscular branches. The main venous drainage of the orbit is through the superior and inferior ophthalmic veins that exit the orbit by passing outside the annular tendon and through the superior orbital fissure.
Seven bones contribute to the framework of each orbit. They are the maxilla, zygomatic, frontal, ethmoid, lacrimal, sphenoid, and palatine bones. Together they give the bony orbit the shape of a pyramid, with its wide base opening anteriorly onto the face, and its apex extending in a posteromedial direction. Completing the pyramid configuration are medial, lateral, superior, and inferior walls. The apex of the pyramidal-shaped bony orbit is the optic foramen, while the base is the orbital rim.The orbit communicates posteriorly with the anterior and middle cranial fossae and inferiorly with the pterygopalatine and infratemporalfossa.Orbital rim (4):It is formed by: Superiorly by the frontal bone; Medially by the frontal process of the maxilla; Inferiorly by the zygomatic process of the maxilla and the zygomatic bone; Laterally by the zygomatic bone, the frontal process of the zygomatic bone, and the zygomatic process of the frontal bone. Foramena related to the rim are:Supraorbital notches or foramina, transmitting the arteries and nerves of the same nameSupratrochlear notches transmitting the arteries and nerves of the same nameRoof of orbit (2): It is made up of the orbital part of the frontal bone with a small contribution from the lesser wing of the sphenoid bone that completes the roof posteriorly. Unique features of the superior wall include: anteromedially, the possible intrusion of part of the frontal sinus and the trochlear fovea, for the attachment of a pulley through which the superior oblique muscle passes (about midway between the supra-orbital notch and the frontolacrimal suture) anterolaterally, a depression (the lacrimalfossa) for the orbital part of the lacrimal gland. The lacrimal gland, located in the superolateral part of the orbit, receives its sensory innervation from the lacrimal nerve and its parasympathetic and sympathetic innervation from the greater and deep petrosal nerves. The petrosal nerves join to form the vidian nerve that enters the pterygopalatine ganglion, which sends branches to the zygomatic nerve that anastomoses with the lacrimal nerve to reach the gland.Floor of orbit (3):It is also the roof of the maxillary sinus, consists primarily of the orbital surface of the maxilla, with small contributions from the zygomatic and palatine bones. Posteriorly, the orbital process of the palatine bone makes a small contribution to the floor of the bony orbit near the junction of the maxilla, ethmoid, and sphenoid bones. Beginning posteriorly and continuing along the lateral boundary of the floor of the bony orbit is the inferior orbital fissure. Beyond the anterior end of the fissure the zygomatic bone completes the floor of the bony orbit.Beginning posteriorly and crossing about two-thirds of the inferior orbital fissure, a groove (the infra-orbital groove) is encountered, which continues anteriorly across the floor of the orbit. This groove connects with the infra-orbital canal that opens onto the face at the infra-orbital foramen. The infra-orbital nerve, a branch of the maxillary nerve [V2], and vessels pass through this structure from inferior orbital fissure to exit onto the face through the infraorbital foramen. Medial wall of orbit (4):The medial walls of the paired bony orbits are parallel to each other and each consists of four bones from anterior to posterior Maxilla (the frontal process of the maxilla): Lacrimal: both lacrimal bone and frontal process of maxilla participate in the formation of the lacrimal groove, which contains the lacrimal sac and is bound by the posterior lacrimal crest (part of the lacrimal bone) and the anterior lacrimal crest (part of the maxilla). Ethmoid: The largest contributor to the medial wall is the orbital plate of the ethmoid bone. This part of the ethmoid bone contains collections of ethmoid air cells, which are clearly visible in a dried skull. Also visible, at the junction between the roof and the medial wall, usually associated with the frontoethmoidal suture, are the anterior and posterior ethmoidal foramina. The anterior and posterior ethmoidal nerves and vessels leave the orbit through these openings. Sphenoid bones. Posterior to the ethmoid bone the medial wall is completed by a small part of the sphenoid bone, which forms a part of the medial wall of the optic canal. Lateral wall of orbit (2): It consists of contributions from two bones-anteriorly, the zygomatic bone and posteriorly, the greater wing of the sphenoid bone. It is separated posteriorly from roof of orbit by superior orbital fissure and separated from floor of orbit by inferior orbital fissure.The lacrimal foramen, which transmits the recurrent meningeal branch of the ophthalmic artery, is located anterior to the superior orbital fissure along the superior edge of the lateral wall. The zygomatico-orbital foramina on the anterolateral part of the intraorbital surface of the lateral wall transmit the zygomaticofacial and zygomaticotemporal nerves (branches of maxillary nerve) and exit the orbit external surface of the zygoma at the zygomaticofacial and zygomaticotemporal foramina to reach the skin of the cheek and temple.The optic canal:When the bony orbit is viewed from an anterolateral position, the round opening at the apex of the pyramidal-shaped orbit is the optic canal, which opens into the middle cranial fossa. It is a horizontal elliptical cavity at its cranial side, is circular in its midportion, and a vertical ellipse at the orbital side. The thickest part of optic canal is the distal end near the foramen (at the cranial side). Its dimension is about 4 × 6 (5-20) mm. The tendinous ring (annular tendon) from which the superior, inferior, medial, and lateral rectus muscles arise, is attached to the upper, lower, and medial margin of the optic canal.Its boundaries are:1) Lateral wall: is formed by Junction one of the two roots of the lesser wing of the sphenoid which also serves as the medial margin of the superior orbital fissure. 2) Medial wall: part of ethmoid and sphenoid sinus.3) Roof: formed by lesser wing. Its proximal end covered by falciform process (it is a fold of dura covering the optic nerve at the proximal end of the canal). Part that is covered only by dura in the canal is about 1 mm in length. The cranial dura is redundant at the cranial end of the optic canal where it forms the falciform ligament. It then traverses the canal where the outer layer is continuous with the periorbita, while the inner layer continues as the optic nerve sheath within the orbit. 4) floor: formed by union of optic strut into the sphenoid body.Its content: 1) the optic is superomedial to ophthalmic artery.2) Ophthalmic branch of the internal carotid artery, 3) Sympathetic plexus around the artery. Superior orbital fissure: The superior orbital fissure is located between the roof of orbit (lesser wing of the sphenoid bone) and lateral wall of orbit (greater wing of the sphenoid bone ) on the lateral side of the optic canal. From the orbital side the frontal bone forms a small portion of the lateral apical margin of the fissure, because the greater and lesser wings approach, but do not meet at the narrow lateral apex.It has a somewhat triangular shape, having a wide base medially on the sphenoid body and a narrow apex situated laterally between the lesser and greater wings. The fissure slopes gently downward from its lateral to medial border. The fissure is not oriented in a strictly coronal plane, but is directed forward so that the lateral apex is slightly forward of the medial margin. The junction of the upper and lower segments of the lateral edge (from the orbital side) is the site of a bony prominence that serves as the site of attachment of the lateral edge of the annular tendon, from which the four rectus muscles arise. This bony prominence can vary from narrow and pointed to broad and flat.Passing through the superior orbital fissure from the middle cranial fossa are 1) the superior and inferior branches of the oculomotor nerve [III], 2) the trochlear nerve [IV], 3) the abducent nerve [VI], 4) the lacrimal, frontal, and nasociliary branches of the ophthalmic nerve [V1], 5) the superior ophthalmic vein 6) A recurrent meningeal artery if presentThe annular tendon of Zinn, a fibrous ring that surrounds the central part of the superior orbital fissure and the optic canal, gives attachment to the superior, medial, inferior, and lateral rectus muscles. The superior oblique attaches above the annular tendon and the inferior oblique arises from the inferomedial orbital wall just behind the rim.Inferior orbital fissure; Itis a longitudinal opening separates the lateral wall of the orbit from the floor of the orbit. It is located between the greater sphenoid wing behind and the maxillary and palatine bones anteriorly. The narrow lateral end is formed by the zygomatic bone, and the narrow medial end is formed by the sphenoid body. It is closed by a fibrous tissue and orbital muscle. This long fissure allows communication between: 1) the orbit and the pterygopalatinefossa posteriorly; 2) the orbit and the infratemporalfossa in the middle; 3) the orbit and and the temporal fossaanteriorly. Passing through the inferior orbital fissure are the 1) The zygomatic and the infraorbital and zygomatic branches of the maxillary nerve,2) some branches of the internal maxillary artery, and the branches of the inferior ophthalmic vein, which communicate with the pterygoid plexus.The oculomotor foramen, located inside the annular tendon and through which the oculomotor nerve passes, is located between the upper and lower attachment of the lateral rectus muscle.Occulomotor nerve: Just before passing through the superior orbital fissure and the oculomotor foramen in the annular tendon, the oculomotor nerve divides into an upper division supplying the superior rectus and levator muscles and a lower division to the medial and inferior rectus and inferior oblique muscles. The oculomotor nerve gives rise to the parasympathetic motor root to theciliary ganglion that lies lateral to the optic nerve. The abducens nerve passes through the oculomotor foramen and enters the medial surface of the lateral rectus muscle. The ophthalmic nerve divides just behind the annular tendon into lacrimal and frontal nerves that pass outside the annular tendon, and the nasociliary nerve that passes through the annular tendon. The ophthalmic nerve gives rise to the long ciliary nerves and the sensory root to the ciliary ganglion; the former conveys the sympathetic pupillomotor fibers and the latter conveys corneal sensation.The trochlear nerve passes above and outside the superomedial edge of the annular tendon.The optic nerve passes superior and medial from the globe to reach the optic canal and divides the retro-orbital space into medial and lateral parts.The maxillary nerve passes through the foramen rotundum to enter the pterygopalatinefossa, where it gives rise the infraorbital and zygomatic nerves and communicating rami to the sphenopalatine ganglion. The infraorbital and zygomatic branches pass through the inferior orbital fissure to course within the orbit. The infraorbital nerve courses along the orbital floor in the infraorbital groove and canal to reach the infraorbital foramen, where its branches are distributed to the cheek. The zygomatic branch passes through the inferior orbital fissure and courses just inside the lateral wall of the orbit, where it divides into zygomaticofacial and zygomaticotemporal branches. These branches enter the zygomatico-orbital foramina on the intraorbital surface of the zygoma and exit the zygoma at the zygomaticofacial and zygomaticotemporal foramina to reach the skin of the cheek and temple, respectively. The main arterial supply to the orbit is by the ophthalmic artery and its branches. This artery courses below the optic nerve in the optic canal, crosses to the lateral side of the nerve at the orbital apex, and then courses from lateral to medial above the optic nerve. The main branches are the central retinal artery and the lacrimal, ciliary, ethmoidal, supraorbital, and dorsal nasal arteries, plus numerous muscular branches. The main venous drainage of the orbit is through the superior and inferior ophthalmic veins that exit the orbit by passing outside the annular tendon and through the superior orbital fissure.
Figure 1: Here we see the optic canal (12 in the figure), which is of course medial to the tip of the superior orbital fissure and which is captured in this scan more laterally. Figure 2: Number 7 here demonstrates the superior orbital fissure. This is most commonly mistaken for the optic canal. However, note that this opening is oriented laterally from the midline plane not medially. This is a key clue to the correct identification. Compare to the image of the CT scan that captures the optic canal below Figure 3: CT scan above the opening for the nasolacrimal duct in the lacrimalfossa and includes the inferior orbital fissure. 4. zygoma 5. inferior orbital fissure (note that the fissure is oriented medially and narrows slightly posteriorly). 6. greater wing of the sphenoid 7. nasolacrimal duct 8. inferior rectus muscle
Inferior orbital fissure Orbital roof Posterior ethmoidal cells Maxillary bone
Pterygomaxillary fissure Inferior orbital foramen Orbital apexPlanumsphenoidal Greater wing of sphenoid Nasal septum
Pterygomaxillary fissure Inferior orbital foramen Orbital apexPlanumsphenoidal Greater wing of sphenoid Nasal septum
Pterygomaxillary fissure Inferior orbital foramen Orbital apexPlanumsphenoidal Greater wing of sphenoid Nasal septum
Squamo us suture
A, Fracture of the sphenoid bone extending through the optic canal. Axial CT image shows the fracture line (large black arrowhead ) extending across the sphenoid. The lucency of one of the fracture lines (black arrow) extends across the optic canal itself. Compare this with the normal intact cortices of the optic canal on the left side (small black arrowhead ). B, Coronal CT bone algorithm shows the fracture (arrow) as a lucency extending along the region of the optic canal. The lesser wing of the sphenoid may be slightly displaced. C, A small bony fragment (arrow) is seen within the medial aspect of the optic canal itself. A displaced fragment impinging on the nerve can significantly compromise the visual pathway.
Medially positioned carotid artery impressing into the sphenoid sinus. The carotid artery (arrow) bulges into the sphenoid sinus. The bony plate separating the artery from the sinus may be thin or dehiscent. Optic canal (arrowhead ).
Enlargment of foramen rotundum
F, Coronal bone algorithm shows enlargement of the foramenrotundum (black arrowhead ) and the Vidian canal (open black arrow). This indicates tumor extension along bothnerves.
Coronal scan shows the tumor (T) scalloping and eroding the sphenoid sinus and dorsum sella. Again, it extends to but not through the foramen ovale. Note the maintenance of the normal fat (black arrowhead ) just beneath foramen ovale.D, Coronal bone algorithm. The foramen ovale between the small black arrowheads is enlarged even though the tumor did not extend through this foramen. Compare with the foramen ovale opposite (large black arrowhead ).
Metastatic renal carcinoma to the sphenoid triangle (greater wing of the sphenoid). A, The tumor is seen replacing the bone of the sphenoid triangle and extending into the orbit, temporalisfossa, and middle cranial fossa. B, Coronal CT postcontrast image
Fibrous dysplasia (FD) shows a typical ‘‘ground glass’’ appearance. The Vidian canal (small black arrowhead ) and the groove for the second division of the trigeminal (large black arrowhead ), just posterior to the foramen rotundum, have been incorporated or displaced by the expanding abnormality.
