Retrobulbar Hemorrhage

Craig D. Lewis; Julian D. Perry

Disclosures

Expert Rev Ophthalmol. 2007;2(04):557-570. 

In This Article

Anatomy

Bony Anatomy

The bony orbit has a volume of approximately 30 cm3. The tight adherence of the orbital septum to the arcus marginalis and the posterior bony confines of the orbit make the orbit particularly susceptible to a compartment syndrome with hemorrhage. Except for numerous small foramina, the bony orbit is a continuous structure, open only anteriorly. The lateral orbital rim is normally at the level of the equator of the globe.[48]

Blood vessels and nerves gain access to the orbit via foramina in the orbital bones ( Table 2 ). The ophthalmic artery and the optic nerve enter the orbit via the bony optic canal, which passes through the lesser wing of the sphenoid bone and ends in the optic foramen.[48]

The oculomotor, abducens and trochlear nerves and branches of the ophthalmic division of the trigeminal nerve, enter the orbit via the superior orbital fissure. Most of the venous drainage of the orbit also exits the superior orbital fissure by way of the superior orbital vein and superior ophthalmic vein to the cavernous sinus. In addition, the orbital branch of the middle meningeal artery and recurrent branch of the lacrimal artery pass through the superior orbital fissure. The superior orbital fissure measures 18 mm in length and is formed by the lesser and greater wings of the sphenoid bone.[48,49]

The inferior orbital fissure transmits branches of the maxillary division of the trigeminal nerve, sympathetic innervation of the lacrimal gland and the inferior ophthalmic veins. The inferior orbital fissure is 20 mm in length and lies between the greater wing of the sphenoid bone laterally and the maxillary and palantine bones medially. It communicates inferiorly with the pterygopalantine fossa and the masticator space.[48,49] Retrobulbar local anesthetic administration can cause bleeding into the buccal fat if the needle extends through the inferior orbital fissue.[50]

The infraorbital groove extends from the inferior orbital fissure and becomes a canal anteriorly in the maxillary bone. The infraorbital nerve and artery pass through the infraorbital canal and exit anteriorly via the infraorbital foramen.[48,49] The orbital perforating branch of the infraorbital artery commonly exits the inferior orbital fissure approximately 14 mm posterior to the rim where it is easily damaged during orbital floor exploration.[51] Laceration of this vessel can lead to retrobulbar hemorrhage.

Anterior and posterior ethmoidal foramina transmit the ethmoidal branches of the ophthalmic artery. The anterior and posterior ethmoidal foramina are located 24 and 36 mm posterior to the anterior lacrimal crest, respectively, along the frontoethmoidal suture. The posterior ethmoidal foramen is approximately 6 mm anterior to the optic foramen.[48] Cauterization of these vessels under direct visualization during medial orbitotomy may decrease the risk of hemorrhage. These vessels may be responsible for orbital hemorrhage during endoscopic sinus surgery.

The zygomaticofacial canal transmits both the zygomaticofacial nerve and artery from the inferolateral orbit to the malar prominence of the zygomatic bone. The zygomaticotemporal canal likewise transmits both the zygomaticotemporal nerve and artery from the superolateral orbit to the temporal fossa.[48,49] The nerves are branches of the maxillary division of the trigeminal nerve and the arteries are branches of the lacrimal artery. During lateral orbitotomy these foramina should be treated with cautery and/or bone wax to achieve hemostasis and prevent hemorrhage.

The meningeal foramen, located along the suture between the frontal and sphenoid bones, transmits the recurrent meningeal branch of the middle meningeal artery.[48,52] Laceration of this vessel can lead to retrobulbar hemorrhage after lateral wall approach orbitotomy. During lateral orbitotomy, careful cautery and/or bone wax in this area can prevent hemorrhage.

Vascular Anatomy

The vascular anatomy of the orbit is complex and varies between individuals.[53]

Arterial Supply. The ophthalmic artery contributes the majority of the arterial blood supply to the orbit. The ophthalmic artery represents the first major branch of the internal carotid artery. In most individuals, the ophthalmic artery arises after the internal carotid artery exits the cavernous sinus and penetrates the dura. The ophthalmic artery usually runs partly in the subdural space with fibrous connections to the surrounding dura. Fine branches of the ophthalmic artery supply the intracanalicular optic nerve and trauma, such as a fracture of the optic canal, may tear these fibrous connections and fine vessels, leading to ischemic optic nerve damage. After exiting the optic foramen, the ophthalmic artery passes over (or under in 13% of individuals) the optic nerve and runs superonasally to the medial wall of the orbit near the anterior ethmoidal foramen, where it is tethered to the medial wall of the orbit.[53]

The central retinal artery branches off the ophthalmic artery approximately 8 mm from the optic foramen and penetrates the ventral dura to enter the optic nerve approximately 18.6 mm from the optic foramen and 8 mm posterior to the globe.[54] The medial and lateral posterior ciliary arteries branch from the ophthalmic artery and together with the central retinal artery supply the remainder of the optic nerve. The optic nerve head is supplied by the posterior ciliary arteries.[53,55]

The external carotid contributes a minor portion of the arterial supply to the orbit via the infraorbital artery and the recurrent meningeal branch of the middle meningeal artery.[53] The infraorbital artery frequently has an orbital branch approximately 14 mm posterior to the orbital rim.[51] This orbital perforating branch is commonly encountered during inferior orbitotomy and should be addressed to prevent hemorrhage.

Venous Drainage. The venous system of the orbit varies greatly between individuals, as well as from one side to the other. The orbital veins frequently form venous networks, further confusing the nomenclature.[53] Unlike other parts of the body, the orbital veins do not directly correspond to the orbital arteries, with the exception of the superior orbital vein, which runs along the course of the ophthalmic artery. The superior orbital vein represents the major source of venous drainage from the orbit. It exits via the superior orbital fissure and empties into the cavernous sinus.[48,49,53] The inferior ophthalmic vein normally runs near the floor of the orbit on the surface of the inferior rectus muscle, and it either joins the superior orbital vein in the posterior orbit or directly drains into the cavernous sinus.[49,53] There are normally numerous venous collaterals connecting the superior and inferior drainage systems. The orbital veins also have multiple communications with extraorbital veins, including the facial and frontal veins, the pterygoid plexus and the nasal veins.[49,53] The central retinal vein empties the retinal circulation. It travels along the central retinal artery and exits the optic nerve 1 - 2 mm posterior to the central retinal artery. The central retinal vein may empty into the superior ophthalmic vein, other orbital venous branches or directly into the cavernous sinus.[56]

Fascial Support

Anteriorly, the contents of the orbit are supported by a complex fascial support system that limits the forward projection of the globe by strong attachments to the bony architecture. The orbital septum forms the anterior soft tissue boundary of the orbit. The septum originates from the superior and inferior orbital rims at the thick arcus marginalis, which is continuous with the periorbita. Laterally, the orbital septum fuses with the lateral canthal tendon and attaches to the lateral orbital rim at Whitnall’s tubercle, located 4 - 5 mm behind the orbital rim. Medially, the orbital septum joins the posterior portion of Horner’s muscle to insert on the inferior posterior lacrimal crest.[48] These anterior structures, along with the bony confines posteriorly, limit the distensibility of the orbit.

The orbit is lined by periosteum that attaches firmly at the arcus marginalis, foramina, fissures, suture lines and the posterior lacrimal crest. Between these firm attachments the periosteum is loosely adherent, creating a potential space for accumulation of blood.[48] Subperiosteal hemorrhage may occur after sudden increase in venous pressure during a variety of activities or spontaneously to produce an often limited orbital hemorrhage. The characteristic CT appearance of an acute subperiosteal hematoma is a broad-based extraconal mass that abuts the bony orbit and displaces orbital contents centrally. Radiographically, the mass is high-density, sharply defined, homogeneous and nonenhancing (Figure 3).[57]

Figure 2.

Bilateral traumatic retrobulbar hemorrhage.

The globe and contents of the orbit are surrounded by a complex system of fascia. Posterior to the corneoscleral junction the globe is surrounded by Tenon’s capsule, a fibrous membrane with openings for the extraocular muscles. The muscles are likewise sheathed in fascia that has extensions to the orbital periosteum. The orbital fat is separated into lobules by fibrous septa continuous with this fascial system.[48] This fascial system allows for loculation of blood after hemorrhage, making hematoma evacuation challenging in some cases.

Adipose Tissue of the Orbit

The adipose tissue of the orbit surrounds and cushions the globe, optic nerve and extraocular muscles. Although there are regional differences in the composition of the adipose tissue at different sites in the orbit, the fatty tissue of the orbit is a single continuous entity from the orbital apex to the fat of the eyelids immediately posterior to the orbital septum.[58] The orbital fat is composed of fat lobules separated by connective tissue septa that carry the nerves and vessels of the orbit.[58,59]

The fat of the upper eyelid is connected by a thin fibrous strip to the orbital fat.[58] Clinically, the adipose tissue of the upper eyelid is comprised of a medial and lateral compartment separated by the trochlea and superior oblique tendon.[48,60] The infratrochlear nerve and medial palpebral artery pass through the medial fat pad. The medial palpebral artery is often transected during upper blepharoplasty and can cause hemorrhage. Hemorrhage from blepharoplasty may occur from direct trauma to other vessels of the anterior fat pads or from tearing of deep orbital vessels from traction on orbital fat.[61] The lateral compartment is more yellow in color and part of the preaponeurotic fat that extends behind the lacrimal gland.[60]

The fat of the lower eyelid is continuous with the adipose body of the orbit.[58] Clinically it is usually separated into a medial, central and lateral compartment. The central and medial fat pads are separated by the inferior oblique muscle, and the central and lateral fat pads are separated by the fascial extensions from the inferior oblique muscle to the inferolateral orbital floor.[48,62] Similar to upper blepharoplasty, hemorrhage from lower blepharoplasty may occur from direct or indirect vascular trauma within the orbital fat.[61]

Optic Nerve

The optic nerve, unlike the other cranial nerves, is a CNS tract rather than a peripheral nerve and is surrounded by cerebrospinal fluid within a meningeal sheath.[48,56] The intraorbital portion of the optic nerve measures, on average, 25 - 28 mm in length.[48,54] It is mildly tortuous with approximately 5 - 7 mm of slack that allows free movement of the globe and provides a margin of safety in proptosis. Further proptosis beyond this degree causes stretching of the optic nerve and tenting deformity of the globe.[63] While orbital hemorrhage can lead to optic neuropathy via optic nerve distension, a compressive etiology is more common.

Comments

3090D553-9492-4563-8681-AD288FA52ACE
Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.
Post as:

processing....