Surgical approaches to the orbit

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CHAPTER 53 Surgical approaches to the orbit

Geoffrey E. Rose, David H. Verity

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Introduction

Historically, orbital surgery has been performed by general surgeons, ophthalmic surgeons and, in particular, neurosurgeons; indeed, Walter Dandy – the highly influential neurosurgeon – suggested that, ‘all orbital surgery should be performed through the transcranial route’ and that ‘such surgery results in less morbidity than the commonly-used orbital approach’¹. During the second half of the 20th century there was a shift towards less traumatic techniques for orbitotomy, avoiding craniotomy when a disease was solely intraorbital – this leading to the development of incisions and approaches with much better esthetic results. Clearly, a neurosurgical approach remains imperative where a disease straddles the cranio-orbital junction (such as with lesions passing through the superior orbital fissure or optic canal), and a maxillofacial or head-and-neck surgeon is best experienced to deal with orbital diseases involving the paranasal sinuses or extending widely outside the orbit.

Contemporary orbital surgeons will often assist neurosurgical or maxillofacial colleagues with more extensive cases, but disease confined to the orbit is generally amenable to approaches that can be performed by an ophthalmic surgeon with specialist training in this particular branch of oculoplastic surgery. A series of practical approaches that provide good access to all areas of the orbit will be outlined, but specific individual procedures, such as orbital exenteration, will not be considered.

Practical and anatomical considerations

The orbit is a tetrahedral soft tissue structure surrounded by bone – except anteriorly – and so, in the absence of bone removal or displacement, the size of all surgical routes is constrained by the anterior orbital opening (generally no more than 3 cm) and the breadth of such an incision is limited by the ability to displace the globe. An anterior incision of this size means that the maximum theoretical ‘conoid of view’ for an apex lesion is about 50° by 30° – although in practical terms this conoid may be only about half this size, due to orbital fat spilling into the operative field and the presence of many relatively fixed orbital structures. The conoid of view may be increased by two mechanisms: the first is to move the incision nearer to the site of the lesion – that is, to shorten the conoid ‘depth’ – and this is effective during the outer canthotomy approach to lateral masses. The second method is to displace an orbital wall outwards, this being the main rationale for bone-swinging lateral orbitotomy.

Access from the physiological entrance to the orbit also leads to another surgical difficulty that worsens with increasing depth: namely, the problem of increasingly oblique viewing of many structures – both normal and abnormal – within the depths of the orbit. This obliquity, which can cause problems with both the identification and the handling of structures, may be effectively reduced by shifting the incision towards the lateral canthus or by swinging the lateral wall outwards during orbitotomy.

The risk of injury to orbital function varies significantly at different depths within the orbit, there being variations within each zone. The risk of collateral injury is low during surgery in the anterior one-third of the orbit, alongside the globe – the risk probably being greatest in the trochlear area and to the palpebral lobe of the lacrimal gland. The most feared risk whilst operating in the middle-third of the orbit is the (relatively rare) visual loss due to ischemia of the optic nerve or optic nerve head, but the ciliary ganglion is probably the most susceptible structure in this sector – a persistent mydriasis being a not uncommon inconvenience after removal of retrobulbar tumors. Due to crowding of highly important structures in the orbital apex, operating in the posterior third of the orbit carries a high risk of complication – many being serious or permanent ²; complete visual loss is quite common with removal of ‘peanut’ tumors wedged in the apex, especially where the tumor lies below the optic nerve, alongside the ophthalmic artery. Complete ophthalmoplegia is common after operating near the superior orbital fissure, this often recovering dramatically at about 3 months after surgery, but sometimes leaving a selective neuropraxia.

Preoperative and postoperative counseling

The appropriate risks of surgery should be explained to the patient, together with the risks of choosing not to have surgery. Clearly there is no real choice where malignancy is suggested on imaging. However, for well-defined ‘benign’-looking apical lesions that carry a significant risk of serious complication with surgery, it is advisable to wait for documented evidence of progressive visual deterioration before considering intervention. The risks for surgery in the anterior one-third are low and explanation can reasonably be limited to those that are anatomically relevant – such as ipsilateral sensory loss after surgery along the orbital roof – and a brief mention of the miniscule risk of visual loss. With surgery in the middle third and posterior third, however, the risks are much greater and preoperative counseling should cover the danger of complete or partial visual loss, squint and diplopia requiring further intervention, ptosis, periocular sensory loss, and a permanent mydriasis (with mild photophobia or presbyopia).

Apart from difficult access or the encroachment of fat into the operative field, it is intraoperative hemorrhage that creates the greatest difficulty and risk during surgery within the orbital depths; heat generated by the use of bipolar diathermy increases inflammation, the latter probably being contributory to early postoperative visual loss due to vasospasm at the orbital apex ². It is, therefore, very important to take a thorough history for any medications that might affect hemostasis³ – this including over 40 brand-named versions of amino-salicylic acid (ASA) and also many foodstuff and ‘herbal’ remedies. All herbal remedies, garlic, ginger, ginseng and gingko should be avoided completely before surgery. If safe to do so, patients should be encouraged to avoid ASA for at least 3–4 weeks before orbital surgery, non-steroidal anti-inflammatory drugs for at least 2 weeks, and other anti-platelet medications for at least 10–12 days. Special arrangements will be required for patients requiring warfarin anticoagulation for metallic heart valves and for patients with recently implanted arterial stents⁴. Medical conditions, such as systemic hypertension or diabetes, should be well controlled in all patients listed for routine orbital surgery, and a preoperative assessment by the anesthetist is appropriate where hypotensive general anesthesia will be required for surgery.

After surgery, a patient should be nursed semi-recumbent to minimize postoperative swelling and, where accessible, the pupils and vision checked for a few hours after surgery. Early postoperative instruction should insist that medical attention is sought if there is significant and increasing pain, as this can be an important symptom of intraorbital arterial hemorrhage; consideration should be given to urgent release of any sutured closure and drainage of hemorrhage where a ‘rock-hard’ marked proptosis has developed, with poor eye movements and evidence of optic neuropathy. Systemic corticosteroid therapy and, if indicated, antibiotics may be prescribed to limit postoperative inflammation and scarring, or prevent infection.

Patients should be warned that gross swelling of the eyelids is common after deep orbital surgery and that, in some cases, this can take several weeks – or even months – to settle. They can pursue all normal activities, apart from vigorous sports and activities that should be avoided during the first 3 weeks after surgery. New-onset diplopia and (the rare) loss of vision present major practical difficulties and patients will require appropriate counseling in relation to their work and lifestyle.

The six principal orbitotomies

All areas of the orbit can be reached through one of six principal routes, although occasionally a combination of two such routes might be required for more extensive disease.

Intraorbital and subperiosteal abscesses should generally be drained through a skin incision, with placement of a small corrugated drain for a day or two – as dictated by the clinical response to treatment. Inert orbital foreign bodies may be left, but others should be removed when visible in the anterior part of the orbit where reversible visual loss is thought to be present, where there is persistent pain with inflammation, diplopia, or infection; all organic matter should be removed, as it almost always develops chronic infection, and copper-containing metals (including brass) should be removed as they incite suppuration. It is easiest to ‘sound’ the entry track with a blunt-ended probe, prior to excision of the track and drainage of the abscess or foreign bodies by means of an incision that includes the fistular opening.

Anterior orbitotomy through the upper eyelid skin crease

Incisions in the upper eyelid skin crease heal without visible scar and provide access to the upper two-thirds of the orbit, if necessary right back to the superior orbital fissure and orbital apex (Fig. 53.1A). Intraconal lesions lying above or medial to the optic nerve are reached by retracting the superior rectus/levator muscle complex either medially or laterally during the surgery.

Fig. 53.1 (AI,AII,AIII) Fields of exploration that are possible with anterior orbitotomy performed through an upper eyelid skin-crease incision. (B) Upper eyelid skin-crease approach to anterior orbitotomy: risk of injury to the levator aponeurosis can be minimized by avoiding low septal incisions (black arrow). It is better to follow the suborbicularis, preseptal plane upwards and then pass through the septum at a higher point (red arrows) to reach orbital mass.

The position for the main upper lid crease is determined by ‘nudging’ the eyelid upwards and the skin and orbicularis muscle incised for a suitable length along it, with meticulous hemostasis being maintained at all stages. For non-lacrimal masses, the plane between the orbicularis and septum is dissected upwards for 3–5 mm before opening the septum to reveal orbital fat (Fig. 53.1B); this upward dissection prior to entering the orbit avoids later ptosis due to direct damage to the anterior levator complex. The septum is button-holed centrally and then divided medially and/or laterally, according to the quadrant in which orbital exploration is needed – the quadrant determined by imaging and also by gentle intraorbital palpation during the surgery. A closed pair of blunt-tipped scissors should be directed towards the mass, through the fat, and then opened widely to reveal the orbital depths; before withdrawing the scissors, the plane and depth of exploration are maintained by passing a pair of 12–16 mm retractors alongside the opened scissors. The orbital mass is typically revealed after repeating this maneuver several times, the surgical assistant maintaining the space with suitable, but gentle, retraction. If a well-defined mass, it should be carefully separated from surrounding tissues with gentle diathermy and division of any bridging vascular pedicles. Unless debulking is planned, a large incisional biopsy should be taken from ill-defined masses – this preferably being achieved with a single grip of the tissues specimen so as to reduce crush artifacts. A vacuum drain should be placed where there has been surgery within the deep orbit, as accumulation of extracellular inflammatory fluid at the apex may cause a major rise in tissue pressure – with associated risk of optic nerve ischemia and visual loss; to avoid a visible scar, such drains may conveniently be passed through the brow.

For lacrimal gland biopsy, the preseptal plane is followed to the superolateral orbital rim, the arcus marginalis divided for 2 cm above the lateral canthal tubercle, and the orbital lobe of the gland lifted from the lacrimal gland fossa. The outer surface of the gland is then inspected and a suitably large specimen of abnormal tissue taken for biopsy; biopsies of the orbital lobe are much preferred to transconjunctival biopsies of the palpebral lobe, as the lacrimal gland diseases tend to spare the latter and its biopsy carries a major risk of dry eye.

After suitable hemostasis, the orbicularis and skin are closed with a running 6-0 nylon suture that can be removed between 5 and 15 days after surgery or, where a soluble suture is required (as in a child, or with no follow-up) 8-0 polyglactan, and a firm eye-pad applied. In most cases the eye-pad and drain can be removed within 12–24 hours of surgery.

Anterior orbitotomy through the lower lid swinging flaps

The approach to the lower two-thirds of the orbit can be through several routes, of which the direct skin incision in the ‘tear-trough’ is effectively redundant, being sometimes complicated by a prominently visible scar, fistula, or adhesions to the underlying bone. Likewise, the subciliary blepharoplasty incision, whilst useful for removal of excessive lid skin, tends to be unnecessarily vascular, thereby hindering orbital exploration, and scarring ⁵.

The contemporary workhorse for inferior orbitotomy is the lower lid swinging flap ^5,⁶, of which the authors now identify two types: the ‘high’ flap, with the conjunctival incision 1 mm below the inferior border of the lower tarsus (Fig. 53.2A), provides excellent access (via a preseptal plane) to the inferior orbital rim and is suitable for almost all surgery along the orbital floor and medial wall – be it for inferomedial decompression or for repair of fractures. The ‘low’ lower lid swinging flap – whereby the internal incision is based in the depths of the lower fornix (Fig. 53.2B) – enters the postseptal extraconal fat pad and, from here, the surgeon can access all except the superomedial part of both the intraconal and extraconal space (Fig. 53.2C). A fundamental understanding of the two types of lower lid swinging flap, not highlighted in the original description for this approach⁶, leads to a rational application of these highly valuable techniques.

Fig. 53.2 (A) The ‘high’ variant of the lower lid swinging flap, used for extraperiosteal approaches to the orbital floor. (B) The ‘low’ variant of the lower lid swinging flap, used for intraperiosteal exploration of the extraconal or intraconal orbital spaces. (CI,CII,CIII) The surgical fields readily accessible by use of the ‘low’ lower lid swinging flap approach. The dotted red line indicates the internal conjunctival incision, sited in the depths of the lower fornix.

The ‘high’ lower lid swinging flap

For both types of flap, the lower lid is disconnected with a slightly downward-directed lateral canthotomy and cantholysis and the medially directed conjunctival incision placed either 1 mm below the lower tarsal edge (for a ‘high’ flap) or along the lowest point in the inferior fornix (for the ‘low’ flap).

For floor or medial wall surgery through a ‘high’ flap, the cornea may usefully be protected by hitching the cut edge of the lower conjunctiva to the upper lid margin with a 4-0 nylon suture on a bow. The periosteum is opened along the orbital rim and the extraperiosteal space exposed as widely as required; for periosteal elevation across the whole floor, it is necessary to coagulate and divide the artery bridging between the infraorbital canal and the orbit. Upward dissection of the extraperiosteal space is limited by the anterior and posterior ethmoidal neurovascular bundles, which are generally very evident at the time of surgery.

Repair of orbital fractures necessitates freeing of all tissues from the fracture site and bridging of the bone defect with a suitable implant; in many cases this implant can be ‘locked’ into place just behind the inferior orbital rim. For some large fractures involving the medial wall and floor, access can be enhanced by continuing the conjunctival incision to become a retro-caruncular incision (see below) and, if necessary, the origin of the inferior oblique muscle divided. Although – because of the high risk of new diplopia – floor decompression should be avoided in all except extreme proptosis, inferomedial decompression can be achieved by out-fracture of the orbital floor and lamina papyracea with piecemeal removal of bone and ethmoid cells.

The swinging flaps are repaired by closure of the lateral end of the conjunctival incision with a 6-0 polyglactan suture, and then a layered repair of the outer canthus – using gray-line and lash-line alignment sutures, sutures between the end of the lower tarsus and the upper limb of the canthal tendon, and finally closure of the skin incision.

The ‘low’ lower lid swinging flap

This postseptal route provides excellent access to the lateral, inferior, and – if needed – medial extraconal space and may be used to biopsy or resect large inflammatory masses, tumors, and vascular anomalies in these areas (Fig. 53.3). Masses straddling an expanded inferior orbital fissure may also be debulked right back and into the pterygo-palatine fossa.

Fig. 53.3 Acute intraconal hemorrhage causing proptosis and optic neuropathy, with drainage and excision of underlying vascular anomaly via a ‘low’ lower lid swinging flap.

Intraconal masses, such as cavernous hemangiomas, can be removed by entering the intraconal fat-space between the inferior and lateral recti – these recti being the most widely spaced. The optic nerve can be reached through the same route, for biopsy or resection; for example, where a solely orbital optic nerve tumor is causing major proptosis of a blind eye, the whole of the intraorbital optic nerve may be removed through this approach. Masses within the posterior one-third of the inferior rectus may be biopsied through this route, as the extreme obliquity of viewing through the anterior transconjunctival approach renders high quality atraumatic tissue biopsy very difficult.

Lateral canthotomy approach to anterior orbitotomy

Biopsy of a tissue or tissues lying in the lateral half of the orbit may be achieved through a lateral canthotomy incision, without disconnection of either the upper or lower limbs of the canthal tendon (Fig. 53.4); this has the advantage of a completely hidden scar, no major disturbance of the lateral fixation of either lid, and a very short operative time.

Fig. 53.4 (A–C) Lateral canthotomy approach to the orbit and corresponding surgical fields that may be reached.

The outer canthus is divided 1–1.5 cm horizontally (to the bone) with a pair of scissors and a traction suture placed through the lateral end of the upper and lower eyelid, creating a rhomboid entry site, without division of the upper or lower lid attachments to the orbital rim. Using the ‘spreading scissors and retractors’ technique as described for anterior orbitotomy (see above), it is possible to explore the extraperiosteal fat plane and obtain biopsy in many cases; if necessary, access may be enhanced by dividing forniceal conjunctiva for a short distance or by raising the lateral fixation of the canthal tendons from the underlying bone tubercle. The incision is repaired in a similar fashion to the outer canthus after lower lid swinging flap.

This approach is particularly valuable where a diffuse process – such as inflammation or lymphoma – is involving multiple tissues and biopsy is required from muscle, fat, and lacrimal gland.

It is also possible to perform a large decompression of the lateral wall through this incision, typically giving a 3–7 mm reduction in proptosis. After undermining the tissues widely, both above and below the canthotomy, the periosteum overlying the lateral orbital rim is exposed and the superficial temporal fascia divided along the posterior edge of the lateral orbital rim. The periosteum is raised forwards over the orbital rim, past the arcus marginalis, and raised widely across the lateral wall of the orbit – dividing the vascular bridges as necessary. The lateral orbital wall is then fenestrated back to the marrow space of the greater wing of the sphenoid, either with preservation of an anterior bar of the lateral rim or – less desirably – by complete removal of the lateral wall. The orbital periosteum is incised widely just behind the arcus marginalis (Fig. 53.5), with three posteriorly directed incisions – one superomedial and one inferolateral to the orbital lobe of the lacrimal gland (thereby allowing the orbital lobe to prolapse back into the upper part of the decompression window) and the third at the lowest part of the fenestration. The fat septa in the inferotemporal quadrant are disrupted widely to encourage a marked prolapse of intraconal and extraconal fat into the area of bone removal, and the periosteum is then closed around the remaining bone rim and to the superficial temporal fascia. A vacuum drain is placed into the intraconal space and subtemporalis space, and the canthotomy is repaired in layers with soluble sutures.

Fig. 53.5 Opening of lateral periosteum behind the arcus marginalis, to permit widespread prolapse of the orbital lobe of the lacrimal gland and the orbital fat.

Bone-swinging lateral orbitotomy

Moving the lateral orbital wall outwards during surgery (lateral orbitotomy) allows an increased access to the orbital apex, with a wider and less oblique view of this area, and with a shorter path length. With advent of the ‘low’ lower lid swinging flap, the need for lateral orbitotomy to remove retrobulbar lesions – such as mid-orbital cavernous hemangiomas – has markedly decreased; lateral orbitotomy remains, however, valuable for the intact removal of large lacrimal gland lesions and for removing ‘peanut lesions’ wedged into the orbital apex. Many past techniques were based on an extended brow incision ⁷, but the laterally extended upper lid incision gives excellent access⁸ through a much shorter incision, with better cosmesis and no thinning of the brow hairs as was frequent after an incision based in the eyebrow. In addition, most contemporary surgeons recognize that it is sufficient to swing the orbital wall out laterally on the temporalis muscle, rather than completely remove the bone during surgery; this former technique has the advantages of retaining a vascular supply to the bone, having a quicker closure, and avoiding any risk of dropping the bone fragment outside the surgical field during surgery.

A skin-crease incision in the lateral two-thirds of the upper lid is extended for about 1–1.5 cm into the inferolateral rhytid and the preseptal plane followed out to the orbital rim. The periosteum is incised 6–7 mm outside the rim, from the lateral one-third of the upper rim to the level of the inferior orbital rim, and the periosteal leaf raised anteriorly, over the orbital rim and backwards across the lateral orbital wall (dividing any vascular bridges as necessary). Two parallel antero-posterior saw cuts are made at the upper and lower ends of the lateral osteotomy, drill holes placed either side of the cuts and, using the same drill, the inner aspect of the lateral wall fragment weakened 1 cm behind the rim. With a large retractor in place to protect the orbital contents, the lateral fragment is out-fractured on the temporalis muscle, with relieving incisions being made (superiorly along the superficial temporalis fascia and inferiorly into the muscle) to facilitate this outward swinging of the bone (Fig. 53.6A). The remaining ragged posterior edge is trimmed with bone-nibblers to increase the access posteriorly and to facilitate replacement of the mobilized bone fragment, and the sphenoidal marrow space treated with bone-wax if there is significant bleeding.

Fig. 53.6 (A) Lateral osteotomy: out-fracture of the lateral orbital wall fragment, with the bone being retained on a temporalis muscle pedicle. One of the drill holes, created prior to out-fracture of the bone, is indicated (arrow). (B) Swinging-bone lateral orbitotomy to remove a massive intraconal dermoid cyst. (C) Pre-placed drill holes (arrows) have enabled soluble 4/0 gauge sutures (dotted lines) to be placed to refix the mobilized bone fragment.

The orbit is opened by incision of the periosteum immediately behind the arcus marginalis and with a posteriorly directed incision just inferior to the lower border of the lacrimal gland. The orbital procedure is performed – typically either intact excision of a large pleomorphic adenoma of the lacrimal gland or dermoid (Fig. 53.6B), or resection of an apical tumor or large intraconal mass – and meticulous hemostasis achieved with bipolar diathermy. The laterally-displaced bone is swung back into place and fixed with a 4-0 absorbable suture passed through the drill holes (Fig. 53.6C), a vacuum drain positioned into the depths of the orbit and the drain taken exteriorly through the lateral brow-line. The periosteum and deep tissues are closed with a 4-0 or 5-0 absorbable suture and the skin incision closed with a running 6-0 nylon suture.

Retrocaruncular medial orbitotomy

Although frequently described as a transcaruncular approach ^9,¹⁰ to the medial part of the orbit, the retrocaruncular approach provides excellent access to the ethmoid sinuses, the medial half of the orbital floor, and extraconal structures within the medial part of the orbit (Fig. 53.7A); as this approach avoids mobilization of the lacrimal sac, is rapid in access and closure, and has no visible scar, it is vastly superior to the Lynch incision that was commonly used in the past. The retrocaruncular approach is particularly valuable where inferomedial orbital decompression is required for compressive optic neuropathy; indeed, in patients with major systemic medical disease it is even possible to perform this procedure under local anesthesia, without any form of sedation.

Fig. 53.7 (AI,AII,AIII) The two main transconjunctival approaches to anterior orbitotomy: the retrocaruncular incision (blue line) provides good access to the whole of the medial orbital wall and the extended peritomy incision (yellow line) is valuable for intraconal or extraconal lesions medial to the optic nerve. (B) Medial intraperiosteal approach to the medial intra- and extraoconal spaces; the medial rectus muscle is gently retracted superiorly to gain access to the medial intraconal space, while the extraconal space is reached with blunt dissection through medial adipose tissue (yellow). (C) Retrocaruncular approach to the medial orbital wall, indicating the position of the posterior lacrimal crest (blue dot); to reach the extraperiosteal space and the ethmoid sinuses, the orbital periosteum should be opened a few millimeters behind the crest. (DI,DII) Medial extraconal orbital lesion and its excision through a retrocaruncular, intraperiosteal approach.

Gentle conjunctival diathermy is applied to the back edge of the caruncle and continued for 1 cm into the inferior fornix, caution being taken to avoid damage to the inferior canaliculus. The conjunctiva is opened along the incision, and closed scissors are directed 45° posteromedially, along the under surface of the posterior lacrimal fascia, to reach the posterior lacrimal crest (Fig 53.7B). At this stage the plane of dissection is intraperiosteal (see Fig. 53.7B) and, for ethmoidectomy or repair of fractures, the extraperiosteal plane has to be entered at a point about 5 mm behind the posterior lacrimal crest (Fig. 53.7C); a 12–16 mm malleable retractor, bent to slightly more than a right angle, provides retraction of the orbital fat and periosteum. Bipolar diathermy is used to tease the fat away from the anterior part of the lamina papyracea (and orbital floor if necessary), and then the periosteum is opened about 5 mm behind the posterior lacrimal crest, so that the extraperiosteal space is gained more posteriorly; the upper limit for peeling periosteum from the underlying bone is clearly defined by the anterior and posterior neurovascular bundles, and the lower limit can be taken as far laterally as the infraorbital nerve canal.

The appropriate intraorbital procedure, for example resection of medial orbital dermoid (Fig. 53.7D), repair of fracture, or decompression may be performed, although fat encroachment into the operative field can prove to be very awkward in some patients. The conjunctival incision is readily closed with two 7-0 soluble sutures, one at the upper and one at the lower border of the caruncle.