Major orbital injuries following functional endoscopic sinus surgery: a descriptive case series from an Australian multidisciplinary survey

Introduction

Functional endoscopic sinus surgery (FESS) has become the cornerstone of medically refractory chronic rhinosinusitis (CRS) (1-3). Although increasingly rare, orbital injury remains one of the most feared complications of FESS (4,5). Advances in endoscopic technique and instrumentation have also rapidly expanded the application of endoscopic sinus surgery to encompass infectious, inflammatory, and neoplastic diseases of the paranasal sinuses, orbit, and base of skull (1). Newer generation powered cutting instruments have been shown to reduce bleeding risk, surgical trauma and operative times, but at the expense of higher iatrogenic extraocular muscle damage, particularly if misdirected in the hands of less experienced surgeons (6,7).

The paranasal sinuses have complex anatomy and are in close proximity to the orbit, with the thin lamina papyracea separating the ethmoid sinuses from orbital contents (8). The orbital walls are vulnerable to sinus disease-related erosion and are also at risk of iatrogenic trauma during FESS (7,9,10). Despite the well-established safety and efficacy of FESS, ophthalmic complications are still encountered and can result in serious morbidity (11,12). Ophthalmic complications following FESS can range from minor injuries such as lamina papyracea breaches, periorbital damage, orbital fat exposure, or more serious injuries such as retrobulbar hemorrhage, extraocular muscle injury, optic nerve injuries, or lacrimal duct injury (9,13). While minor breaches of the orbit such as fat prolapse are often manageable, major injuries involving the extraocular muscles or optic nerve can be devastating. However, the true long-term morbidity and predictors of these catastrophic outcomes remain poorly defined. Existing evidence is limited, but suggests there is a very poor prognosis for major orbital complications following FESS, particularly for injuries to the extraocular muscles, and optimal management strategies are poorly described (14,15). Specifically, injury to the superior oblique (SO) muscle is an under-recognised complication possibly associated with frontal drill-outs. Despite anatomical vulnerability of the superior-oblique tendon and tendon-trochlea complex to the frontal recess, where surgical visibility is poor and high-powered drills are used, little is known regarding the longer-term morbidity of these injuries.

The aims of this study are therefore twofold: to present a case series of major orbital injuries drawn from a national Australian multidisciplinary survey, and to describe a case series of superior oblique injuries following FESS.

Methods

Study design

This was a voluntary survey of self-reported cases of major orbital injuries associated with endoscopic sinus surgery collected from members of the Australian Society of Otolaryngology Head and Neck Surgery (ASOHNS), Australian and New Zealand Rhinologic Society (ANZRS), Australia and New Zealand Strabismus Society (ANZSS), and Royal Australian and New Zealand College of Ophthalmologists (RANZCO). This is a descriptive case series drawn from a National Multidisciplinary survey and does not represent a definitive audit or estimation of national incidence. The study is reported according to the STROBE reporting guidelines (available at https://www.theajo.com/article/view/10.21037/ajo-2025-1-82/rc).

Survey development and distribution

We developed a structured survey designed to capture all ocular injuries associated with FESS, reported by ear, nose, and throat (ENT) surgeons and ophthalmologists who had managed or were involved in patient care. The survey was designed to capture all forms of iatrogenic ocular injury following FESS, including but not limited to involvement of the extraocular muscles, optic nerve, lacrimal system, orbital fat, periorbita/lamina papyracea, globe, and retrobulbar space. Orbital complications of FESS may be categorised as minor or major. Major complications are commonly defined according to the classification criteria initially proposed by May et al., which has been widely adopted (16). Under this classification system, major orbital complications include postseptal orbital haematoma, visual loss or blindness, diplopia, and epiphora requiring surgical intervention (dacryocystorhinostomy) (16). We present all survey findings, with particular focus on major orbital complications including extraocular muscle and optic nerve injuries. Survey content was designed by a review of existing literature and in consultation with rhinology and strabismus experts. The instrument comprised 27 items, mainly including multiple-choice and free text responses (Appendix 1). Items collected included respondent information, case information, operative details, and complication details including management approaches and outcomes.

The survey was distributed electronically via Google Forms in August of 2025 to members of four Australian and New Zealand medical societies mailing lists (ASOHNS, ANZRS, ANZSS, and RANZCO). To maximise participation, the survey was distributed to the medical societies twice. Participation was voluntary and anonymous in regard to respondent name, institution, and location. Duplicate case screening was performed due to the distribution of the survey across multiple overlapping societies. Case entries were cross-checked using age, gender, and injury type data. Where complete concordance was observed, one entry was excluded as a presumed duplicate.

Statistical analysis

Data were exported into Excel for cleaning, and descriptive statistics were used to summarise respondent and case characteristics, including medians and interquartile ranges (IQRs) for continuous variables and proportions for categorical variables. Given the small sample size, no inferential statistical analyses were performed.

Ethical consideration

The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. Ethical approval was obtained from the Central Adelaide Local Health Network Human Research Ethics Committee (reference No. 21481), and individual consent for this retrospective analysis was waived.

Results

The survey was distributed to members of ASOHNS (n=642), ANZSS (n=221), RANZCO (n=1,736), and ANZRS (n=121), with seven cases included in the final analysis comprising three reported from ASOHNS respondents, two from ANZSS respondents, and two cases from The Queen Elizabeth Hospital. Of the seven included cases, five were reported by ENT specialists and two were reported by ophthalmologists. Structures injured included medial rectus muscle (n=5), superior oblique muscle (n=2), orbital hematoma (n=1), and optic nerve (n=1), as shown in Table 1. There were also a small number of isolated lamina papyracea injuries (n=3) and orbital fat prolapse (n=2) not associated with a major complication reported. Two cases had injury to multiple structures: one case of medial rectus injury with orbital hematoma, and another case of medial rectus and optic nerve injury. Surgery was performed by a consultant ENT surgeon in three cases, by a registrar in two cases, and unknown in two. Surgeons were right-handed in five cases (5/7), with handedness unknown in two (2/7). Most injuries occurred on the right side (3/7), followed by left (2/7) and unknown (2/7). Both cases of superior oblique injury occurred on the right side, by right-handed surgeons. The patients were male in 5/7 cases, with a median age of 56 years (IQR, 44–63 years). The most common indication for surgery was CRS without polyps (n=4), followed by CRS with polyps (n=3), one case of superior oblique injury also had a frontal mucocele. There were 1/7 cases with pre-existing lamina papyracea dehiscence; no other preoperative abnormalities were reported. The most common surgery performed was bilateral full-house FESS (FHFESS) (n=6), followed by frontal drill out (n=2, both combined with FHFESS), and unilateral sphenoidotomy (n=1). Image guidance was used in 2/7 cases, both involving superior oblique injury. The instrument causing injury was most commonly the microdebrider (n=2), followed by through-cutting instruments (n=1), cutting burr (n=1), and unknown (n=3). An intraoperative complication was noted in 3/7 cases, which consisted of orbital fat prolapse in 3/7, orbital hematoma in 1/7, and direct muscle injury with oculocardiac reflex resulting in bradycardia in 1/7. In one case of medial rectus injury, direct intraoperative muscle injury was noted, as shown in Figure 1. An intraoperative ophthalmology consult was acquired in 3/7 cases.

Figure 1 A case of medial rectus muscle injury during FHFESS (Case 2). (A) Intraoperative endoscopic images showing exposed medial rectus muscle (black arrow) at time of injury with microdebrider. (B) Postoperative axial CT orbit displaying complete transection of medial rectus muscle (white arrow). CT, computed tomography; FHFESS, full-house functional endoscopic sinus surgery.

There were 5/7 cases which had immediate postoperative diplopia (one could not be assessed as had concurrent optic nerve injury and complete vision loss), and one case of medial rectus injury had diplopia onset after 1–3 days, as shown in Table 2. This case was thought to be delayed due to medial rectus tethering and entrapment through a medial orbital fracture, causing subsequent muscle ischemia and delayed onset diplopia. There were 5/7 cases with clinical signs postoperatively, which most commonly included ocular motility limitation (n=4) and periorbital swelling/ecchymoses (n=2). One case of concurrent medial rectus and optic nerve injury had periorbital swelling/ecchymosis, vision loss, afferent pupillary defect, orbital compartment syndrome, proptosis, and complete vision loss. Both cases of superior oblique muscle palsy did not have any clinical signs postoperatively, and one case had no evidence of traumatic injury intraoperatively or on postoperative computed tomography (CT) imaging. The other case of superior oblique palsy had evidence of bone dehiscence over the area of the trochlea where the injury occurred, with slight thickening of the affected superior oblique tendon on postoperative imaging (Figure 2). All seven cases were referred to ophthalmology for management, which consisted of corticosteroids in 5/7 (3 intravenous, 2 oral), canthotomy/cantholysis in 2/7, botulinum injection in 1/7, triamcinolone injection in 1/7, and orbital wall reconstruction in 1/7 (a case with concurrent medial rectus injury and orbital wall fracture). The reported cases of minor orbital injury including fat prolapse and lamina papyracea injury (n=5) were all successfully managed with postoperative observation alone, and all patients had complete symptom resolution in less than 1 week postoperatively.

Figure 2 A case of superior oblique palsy following FHFESS and frontal drill out (Case 7). (A) Preoperative sinus CT demonstrating right mucocele formation with dehiscent bone over the roof of the orbit (arrow); however, with intact bone over the trochlear. (B,C) Postoperative coronal and axial CT imaging demonstrating the postoperative appearance of a frontal drill-out. Note the dehiscent bone over the location of the trochlea where the injury occurred. (D) T1-weighted MRI demonstrating oedema over area of bone dehiscence. (E) Coronal T2-weighted sequence demonstrating slight thickening of right superior oblique when compared with left (4 vs. 2 mm). CT, computed tomography; FHFESS, full-house functional endoscopic sinus surgery; MRI, magnetic resonance imaging.

Of patients with extraocular muscle injury, 5/7 had no or partial symptom improvement and are still symptomatic after 12 months, and the remaining 2/7 had complete symptom resolution after 3–6 months.

Discussion

Orbital injury remains one of the most feared complications of endoscopic sinus surgery. To our knowledge, this is the first nationwide survey distributed to Australian surgeons attempting to capture cases of major orbital injury since the widespread adoption of endoscopic approaches for sinus surgery. Although data from other international studies inform on the rarity of orbital complications following FESS, our study cannot estimate the national prevalence of major orbital complications amongst Australian and New Zealand surgeons and should instead be interpreted as a descriptive case series derived from a national survey (17,18). When major orbital complications are encountered, particularly those with damage to the extraocular muscles, there is significant morbidity despite rapid and intensive management approaches. Of note, we report two cases of superior oblique muscle injury, a complication reported rarely in existing literature, both of which remained symptomatic despite treatment.

Major complications of endoscopic sinus surgery, including orbital injuries, large volume epistaxis, carotid artery injury and base of skull injury, are reported at around 1% in large database reviews, with orbital complications specifically at 0.07–0.74% (4,5,19). Earlier systematic reviews reported slightly higher rates of orbital complications, including orbital hematoma (0.15%), orbital penetration and fat exposure (2.1%), and postoperative diplopia with extraocular muscle injury (0.3%) (20). Reductions in the rates of orbital injuries likely reflect improvements in surgical technique, experience and familiarity, as well as increased understanding of high-risk anatomical features on preoperative CT (17). Importantly, previous estimates on major orbital complication incidence are drawn from large administrative databases or systematic reviews, unlike our study, which focuses on voluntary survey responses, which precludes any conclusions drawn regarding national Australian complication rates. Although the prevalence of major orbital complications in practice is low, the large volumes of FESS performed annually amounts to a clinically meaningful number of cases. More importantly though is the significant morbidity for most major orbital injuries, particularly those to the optic nerve and extraocular muscles, which can result in permanent vision loss, strabismus or disabling diplopia despite aggressive management (15,21,22). Sohn et al. described 10 extraocular muscle injuries following endoscopic surgery, with no patient regaining normal extraocular muscle movement following attempts at surgical repair (23). Ben Artsi et al. reported six cases of diplopia post-FESS, most due to direct medial rectus injury, in which only one patient achieved complete symptom resolution despite undergoing prompt surgical intervention (11). The authors concluded that immediate recovery procedures to reattach muscles in cases of proven transection are largely futile. In our series, over two-thirds of patients with extraocular muscle injury showed no to minimal recovery, while the remainder improved only gradually and after multiple interventions.

Although the medial rectus is most commonly injured extraocular muscle during FESS due to its anatomical proximity, the superior oblique muscle has been reported as the second most affected in multiple series (23-25). A retrospective review of 15 cases of extraocular muscle injury after FESS found superior oblique muscle damage in 4 cases (26.7%), due to direct trauma, nerve damage, or contusion (12). Superior oblique injury, like other extraocular muscle injuries during FESS, is known to occur in conjunction with other extraocular muscle or optic nerve injuries; however, it can also occur in isolation (12,26). Lin et al. described a case of isolated superior oblique palsy following direct endoscopic probe penetration of the lamina papyracea during extensive sinus surgery including bilateral frontal sinusotomy, which resulted in persistent diplopia (27). Importantly, some cases of extraocular muscle injury can arise from non-traumatic mechanisms, which have been suggested to occur as a result of microvascular nerve palsies secondary to intraoperative hypotension, damage to the cranial nerves due to adjacent ethmoid tissue manipulation, or from perineural oedema (28-30). In our series, one case of medial rectus injury occurred likely via an ischemic mechanism whereby a fractured medial orbital wall led to medial rectus muscle herniation and entrapment, with delayed onset diplopia. Another case of superior oblique muscle palsy had no intraoperative trauma and an unremarkable postoperative orbital CT. Some reports suggest monopolar cautery in the region of the trochlear attachment as a potential mechanism of injury in superior oblique palsy (31). Owing to its rarity, there are few reports on the treatment strategies for these patients, such as rescue strabismus surgery (11).

The finding that both reported superior oblique injuries in this series occurred during frontal drill-out procedures is possibly important, which may point to a specific, high-risk mechanism of injury. However, our series is limited in the conclusions drawn given there were only two cases of superior oblique injury, which precludes definitive causal mechanisms or procedural associations. Frontal drill-out procedures are not routine FESS procedures; they are technically demanding surgeries reserved for extensive or recalcitrant disease. Such procedures require aggressive bone removal with high-speed burrs at the absolute limits of the surgical field, fundamentally altering the anatomy of the frontal recess. This brings powerful instrumentation into immediate proximity with the superior oblique tendon and trochlea, possibly providing a mechanistic basis for injury warranting further exploration in much larger nationwide cohorts. Despite prompt ophthalmology referral and subsequent management, neither of these cases showed complete recovery at 12 months, suggesting the prognosis of this injury type may be poor. This underscores the importance of having good landmarks for the superior oblique tendon when performing a frontal drill-out, something which is currently lacking in existing literature. A single cadaveric study has quantified the diagonal vector between the first olfactory neuron and the trochlea; however, these geometric measurements offer limited practical applicability and are difficult to translate into reliable surgical landmarks to help identify and prevent superior oblique tendon injury (31).

Mitigating orbital complications is best achieved through preoperative and intraoperative preventative strategies. An interesting observation in our series was that most injuries occurred on the right side, performed by right-handed surgeons. While our small sample size precludes any firm conclusion, it raises the question of whether surgical ergonomics and instrument trajectory could contribute to laterality of risk, a point worthy of future investigation. Preoperative high-resolution CT (HRCT) is essential in providing surgically relevant anatomical information and can identify features increasing the risk of orbital complications, some of which include maxillary sinus hypoplasia, infraorbital nerve dehiscence, lamina papyracea dehiscence, small anterior ethmoid air cells, an acute angle of uncinate process with lamina papyracea and anterior ethmoidal artery displacement, which can lead to intra-orbital hematoma if injured (32). The lamina papyracea, located just superior to the maxillary antrostomy, can be breached either through iatrogenic harm, estimated to occur with orbital fat exposure in up to 6.3% of surgeries, or through pre-existing dehiscence, which is present in 0.76–10% of the general population (33-35). Preoperative lamina papyracea dehiscence, identifiable on imaging, may represent an anatomic risk factor and could warrant management by surgeons experienced in complex sinus surgery. By contrast, intraoperative breach of the orbital compartment represents a procedural complication rather than a pre-existing risk factor and cannot be anticipated in the same manner. Several cases in our series had documented intraoperative breach. Once the lamina papyracea and corresponding periorbita are violated, herniation of orbital contents, possibly including extraocular muscle, can occur in up to 60% of cases (33,36).

Strengths and limitations

This study has several strengths, including its national scope and multidisciplinary representation from members of four major surgical societies, attempting to capture both ENT surgeons and ophthalmologists across Australia and New Zealand. However, several limitations should be acknowledged. Most significantly, the study relied on a voluntary survey with an overall low participation rate across the societies, which limits the ability to infer national practice patterns or estimate complication incidence. The absence of a ‘null response’ option prevents accurate estimation of the true incidence of adverse orbital events among those with no reported complications. The marked under-representation of reported cases of lamina papyracea and orbital fat exposure in the survey, although not a priority, also suggests substantial reporting and selection bias. Additionally, although cases were screened for duplicate reporting, this cannot be entirely excluded due to potential inaccuracies in respondent recall. No defined timeframe for case inclusion was specified in the survey. Respondents were therefore able to report cases from any stage of their career, introducing the potential for recall bias and variability in case detail and completeness which cannot be verified independently against clinical records. Given these findings, our study should be interpreted as a descriptive case series of major orbital complications drawn from national survey findings, not a representative dataset of orbital complication prevalence.

Conclusions

Major orbital injuries following FESS, while uncommon, typically have poor outcomes. Injuries to extraocular muscles frequently result in permanent, debilitating diplopia in the majority of cases despite aggressive postoperative interventions. In this series, superior oblique injuries were observed following frontal-drill-out procedures, suggesting a possible procedure-specific cause for catastrophic injury. However, our findings should be interpreted with caution given the small case numbers. Further research to define reliable intraoperative landmarks for the superior oblique tendon during frontal drill-out procedures is warranted to improve surgical safety.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://www.theajo.com/article/view/10.21037/ajo-2025-1-82/rc

Data Sharing Statement: Available at https://www.theajo.com/article/view/10.21037/ajo-2025-1-82/dss

Peer Review File: Available at https://www.theajo.com/article/view/10.21037/ajo-2025-1-82/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://www.theajo.com/article/view/10.21037/ajo-2025-1-82/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. Ethical approval was obtained from the Central Adelaide Local Health Network Human Research Ethics Committee (reference No. 21481), and individual consent for this retrospective analysis was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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