18.2.1 Preoperative Considerations
A thorough history should be taken to identify factors that increase the likelihood of orbital injury, such as preoperative abnormality of the lamina papyracea. These factors include previous orbital trauma or surgery, sinonasal tumor, severe nasal polyposis, or expansile lesions such as sinus mucoceles. It is also worth seeking an ophthalmic history of reduced visual acuity, the presence of amblyopia, or prior squint surgery—this provides a baseline if later orbital evaluation is required and will also alert the operator to potential issues. Ophthalmic signs are also relevant should subsequent events occur—such as pupillary dilation due to accidental contact with intranasal sympathomimetics (e.g., cocaine or adrenaline). 3 The normal latent squint during recovery from general anesthesia may be greater after intraoperative muscle relaxants, and thereby engender unwarranted concern for the surgeon.
Examination may reveal orbital signs—such as proptosis, nonaxial displacement of the globe, or restricted eye movements—or confirm the presence of significant sinonasal disease, and any preoperative abnormalities should be carefully documented.
Preoperative imaging with thin-slice computed tomography (CT) of the paranasal sinuses is mandatory before endoscopic sinus surgery, and the surgeon should not proceed with surgery if the images are not available in the operating theater. Scans should be reviewed not only to assess the extent of disease and any previous surgery, but also to evaluate the lamina papyracea and identify anatomical variants that may increase the risk of orbital complications—such as a hypoplastic maxillary sinus, an anterior ethmoid artery on a mesentery ( ▶ Fig. 18.1a), or a sphenoethmoidal (Onodi) cell ( ▶ Fig. 18.1b; ▶ Table 18.1).
Fig. 18.1 Coronal CT (computed tomography) scans showing (a) bilateral anterior ethmoid arteries on mesenteries (arrows) and (b) bilateral sphenoethmoidal cells (SE), with optic nerve running within the left SE cell (arrow). “S” denotes sphenoid sinus.
Infraorbital (Haller) cell
Anterior ethmoid artery
Sphenoethmoidal (Onodi) cell
Optic nerve dehiscent within lateral wall or within sphenoethmoidal cell
Cerebrospinal fluid leak
18.2.2 Intraoperative Considerations
Complications are more likely to occur in a poor surgical field, and adequate preparation of the nose with topical adrenaline, Co-Phenylcaine spray, or Moffett’s solution (a mixture of adrenaline, cocaine, normal saline, and sodium bicarbonate) provides valuable vasoconstriction of the sinonasal mucosa. 4 Controlled hypotensive anesthesia, with a relative bradycardia, further improves the surgical field 5 and venous oozing is reduced by elevating the head of the operating table or tilting it into the reverse Trendelenburg position. To further improve the surgical field, local anesthetic with adrenaline is sometimes injected into the axilla of the middle turbinate or into the greater palatine foramen—but blindness has been reported due to optic nerve ischemia from arterial spasm, or as a result of retrograde flow of injected solutions from the nasal cavity to the retinal artery. 6, 7
The patient’s eyes should be left uncovered during endoscopic surgery, with lubricant instilled to prevent corneal erosions; this allows both the surgeon and the scrub nurse to monitor the eye for any intraoperative movement under the eyelid (as would occur if the medial rectus muscle was inadvertently pulled) or for the acute development of proptosis in the case of orbital hemorrhage. The eye should also be balloted under direct vision to assess for dehiscence of the lamina papyracea.
18.2.3 Surgical Technique
The nasal endoscope allows excellent visualization of the surgical site, and the tips of surgical instruments should always be visible. Powered instruments, such as microdebriders and drills, are now commonly used in endoscopic sinus surgery and significant injury can occur if they inadvertently enter the orbit through a dehiscent or previously intact lamina papyracea. 8 The microdebrider will suck orbital fat and extraocular muscle into its opening, where the rotating blade cuts at up to 5,000 rpm. Similarly, injudicious use of powered instrumentation in the sphenoid sinus or a sphenoethmoidal cell may lead to optic nerve injury. The blade of such instruments should always be visible, and should be angled away from the orbit to avoid accidentally drawing orbital periosteum or orbital contents into the opening.
The orbital floor is visible through a middle meatal antrostomy, and the lamina papyracea should be identified early, as using these bony orbital walls as anatomical landmarks should help prevent injury. There is some evidence that right orbital injury is more likely with a right-handed surgeon, but equal care should of course be taken on both sides. 9, 10
18.3 Management of Orbital Injury
18.3.1 Breach of the Lamina Papyracea
This is the most common orbital complication of endoscopic sinus surgery. The lamina papyracea may have a preoperative dehiscence, either from the disease process ( ▶ Fig. 18.2a) or from previous surgery or trauma ( ▶ Fig. 18.2b). Such abnormalities do not preclude surgery, but greater vigilance should be taken throughout the procedure—especially with the use of powered instruments—to avoid damage to the underlying orbital periosteum. If the lamina is breached, the extent of the injury should be documented, but surgery can usually be continued without any further injury. The lamina is most commonly injured during anterior ethmoidectomy, or during uncinectomy—particularly if there is a hypoplastic maxillary sinus ( ▶ Fig. 18.3a) or concha bullosa ( ▶ Fig. 18.3b) associated with lateralization of the uncinate process.
Fig. 18.2 Preoperative axial CT (computed tomography) scans showing (a) breach of the right lamina papyracea due to eosinophilic fungal rhinosinusitis and (b) posttraumatic disruption of the right lamina papyracea.
Fig. 18.3 Anatomical variants that may predispose to orbital injury during endoscopic intranasal surgery. Coronal CT scans showing (a) hypoplastic left maxillary sinus (M) with lateralization of the uncinate process. (b) Left concha bullosa (arrow) associated with narrowing of the middle meatus.
Periorbital ecchymosis and a large subconjunctival hematoma may be evident after intraoperative orbital hemorrhage ( ▶ Fig. 18.4a), and serial visual checks should be performed in the early postoperative period. No other specific management is required, but patients should be advised not to blow their nose for 7 to 10 days after surgery. The risk of developing surgical emphysema of the orbit ( ▶ Fig. 18.4b) or periorbital region should be explained to them, and they should be advised to seek immediate review if they develop periorbital swelling, pain, or visual symptoms.
Fig. 18.4 (a) Postoperative orbital hematoma characterized by a tense orbit, reduced eye movements, and a large subconjunctival hemorrhage without visible posterior extent. (b) Multiple subconjunctival air bubbles (“emphysema”) after nose blowing with a breach of the ethmoid lamina, as viewed on slit-lamp biomicroscopy.
18.3.2 Surgical Emphysema
Most cases of postoperative surgical emphysema ( ▶ Fig. 18.4b), usually resulting from a breach in the lamina papyracea, do not require specific management apart from reassurance that it will resolve over several days. If the emphysema is extensive, visual acuity should be checked and ophthalmic review is advisable.
A breach of the lamina papyracea may go undetected, or there may be a natural dehiscence such as that found in the young or elderly. Because of this, oil-based ointments should be avoided within the surgical cavity as they can be forced into the adjacent orbital soft tissues where they may cause a granulomatous reaction, or myospherulosis, which is cosmetically noticeable and difficult to treat.
18.3.3 Breach of the Orbital Periosteum
Orbital fat will be visible if the orbital periosteum is breached, and the fat may prolapse into the sinonasal cavity, sometimes associated with periorbital bruising. The eye should be balloted under direct vision to observe for movement of the lateral nasal wall and/or intranasal prolapse of orbital contents. In most cases, a small amount of prolapsed fat will not prevent completion of the procedure, and a neuropatty or piece of Surgicel may be placed over the periosteal breach to prevent further injury. If there is any concern that continued surgery would lead to further orbital injury, then surgery should be stopped on that side.
Surgicel may be laid over any exposed orbital tissues at the end of the operation and nasal packing (absorbable or otherwise) may be considered, depending on the extent of the breach, to minimize surgical emphysema and prevent enophthalmos. Serial visual checks should be performed in the early postoperative period. Patients should be advised to avoid nose blowing for 7 to 10 days after surgery, and they should seek immediate review if they develop periorbital swelling, pain, or visual symptoms. Typically, the injured orbital periosteum heals rapidly and with no long-term sequelae.
18.3.4 Intraorbital Hemorrhage
Intraorbital bleeding from a transected anterior ethmoidal artery is regarded as the commonest cause of an iatrogenic intraorbital hemorrhage during endoscopic surgery. The posterior ethmoid artery, running anterior to the face of the sphenoid, is rarely responsible for this complication as it tends to run within the bone of the skull base and mucosa is less often stripped in this region. The anterior ethmoidal artery runs on the skull base in approximately 60% of sinuses and is therefore relatively protected ( ▶ Fig. 18.5a); when it lies within a mesentery, it is more at risk ( ▶ Fig. 18.5b). 11 Intraorbital arterial hemorrhage causes pain, with rapid onset of proptosis and increased intraorbital pressure that may cause optic nerve ischemia. The ischemia is probably caused by both compression and stretching of the optic nerve, with consequent blindness if not identified and treated promptly. Animal studies have reported permanent visual loss after 90 minutes of ophthalmic artery ischemia, but there are clinical reports of this occurring within 1 hour. 8, 9
Fig. 18.5 Anterior ethmoid artery (arrow; a) on the skull base and (b) within a mesentery.