Surgical orbital spaces
After a lesion is identified, characterized, and localized, a careful definition of the surgical goals must be considered. In general, interventions are either diagnostic or therapeutic. Diagnostic biopsies are reserved for lesions that are inadequately characterized clinically or radiographically, are invasive, and are potentially responsive to medical therapy. Diagnostic biopsies must remove a representative portion of the lesion while preserving normal surrounding structures. The specimen may be inspected intraoperatively. Results of the frozen section histology may alter the surgical plan by limiting what was initially planned as a larger resection. Frozen section histopathology is, however, not as diagnostically reliable as permanent histopathology, and, consequently, it is rare that more extensive surgery be performed on the basis of frozen section pathology. Complete excision is reserved for lesions that are well-encapsulated or invasive lesions that are malignant or are likely to result in local recurrence and destruction of normal structures. In cases of an invasive lesion with slow growth, little risk of local destructive behavior, or metastasis, sequential debulking as clinically required is advisable.
Advances in orbital surgery in the past 25 years include noninvasive imaging, the operating microscope, the endoscope, and microdissection instruments. These tools have permitted access to lesions once considered inoperable as well as minimizing the invasiveness of surgery, all resulting in significantly less postoperative functional and cosmetic deformity. This chapter describes by operative approach the various orbital spaces, the typical lesions found in each space, and the surgical procedures that may be used to enter the described surgical space. It is not meant to provide a detailed atlas for orbital surgery but rather a topographic approach, describing with how to reach specific compartments within the pediatric orbit. More detailed information on the specifics of each orbital procedure is available in several cited texts [1–4].
Surgical Approaches to the Anterior Orbit
Anterior approaches to the orbit (Fig. 37.2) provide access to the anterior half of the orbital contents. Both extraconal and the extraperiosteal spaces are accessible via this approach. Typical lesions encountered in these spaces are dermoids of the nasofrontal and frontozygomatic sutures, hemangioma (capillary and cavernous), and lymphangioma. Although any of these incisions can provide access to the anterior orbit, the most commonly used are the lid crease, subciliary, and transconjunctival incisions. The choice of incision is dependent on the quadrant in which the lesion is located. Greater detail on medial, lateral, superior, and inferior orbitotomy will be presented in the section on approaches to the posterior orbit.
Anterior orbitotomy incisions. (a) Sub-brow. (b) Modified lynch. (c) Conjunctival. (d) Lid crease. (e) Lateral. (f) Subciliary
Upper Eyelid Skin Approach
It is generally possible to reach the anterior orbit through a lid crease incision in the upper lid (Fig. 37.3). If greater vertical or temporal exposure is required, the incision may be extended temporally in a lid fold. The lid crease is marked with a methylene blue pen, and the incision is infiltrated with 0.25% Marcaine (bupivacaine) with epinephrine 1:200,000. A silk traction suture is often helpful when placed in the lid margin. The incision is made through the skin. Judicious use of bipolar cautery along the skin edge minimizes wound shrinkage and scarring. Orbicularis muscle is divided and spread bluntly to enter the avascular preaponeurotic plane. In this plane, dissection superiorly will identify the translucent orbital septum. Care should be taken to avoid injury to the underlying levator aponeurosis. Opening the septum reveals the preaponeurotic or postseptal fat (Fig. 37.4). Temporally located is the lacrimal gland, which is paler and firmer than the central or nasal fat pads (Fig. 37.5). Within the substance of the nasal fat pad are the trochlea, the superior ophthalmic vein, and the transverse ligament of Whitnall, which serves as a suspensory support for the levator complex. Whitnall’s ligament also divides the lacrimal gland into its orbital and palpebral portions (Fig. 37.6). All of these structures are obscured by the orbital fat, and care must be taken to avoid injury during dissection. Anterior orbital masses, particularly vascular tumors or malformations, can be reached by this approach (Fig. 37.7). Access to the deeper intraorbital and intraconal spaces is limited to the nasal compartment (Figs. 37.8 and 37.9). Access to the superior subperiosteal space is made by extending the dissection superiorly toward the rim of the orbit. Ultimately, this dissection will carry beneath the brow fat pad. The orbital periosteum may be opened horizontally, and, with a periosteal elevator, blunt dissection in the subperiosteal plane may proceed posteriorly into the orbit (Fig. 37.10).
Upper eyelid crease incision
Orbital septum . The lid crease incision has been made and the orbicularis muscle divided. The orbital septum is bluntly opened with curved scissors, revealing orbital fat
Anterior orbital fat. There are two postseptal or preaponeurotic fat pads in the upper eyelid. The nasal and central fat pads are illustrated. The lacrimal gland is vulnerable to damage during dissection in the lateral superior orbit. In the lower eyelid there are three fat pads. The inferior oblique muscle divides the medial and central pads. The lateral fat pad covers the inferotemporal space, which affords the safest access into the intraconal compartment from the inferior approach
Superior orbit with fat pads removed. The trochlea and superior oblique tendon are now visible as is the superior transverse ligament of Whitnall and the lacrimal gland
Anterior orbital lesion. The orbital fat is reflected superiorly with a retractor exposing the levator aponeurosis and revealing a vascular lesion of the anterior superior orbit
Lid crease incision for orbital dermoid. (a) Medial ptosis secondary to orbital dermoid cyst. (b) CT scan of dermoid. (c) MRI scan of dermoid. (d) Exposure of tumor through lid crease incision. (e) Traction with cryoprobe. (f) Closure of skin incision with running 6–0 monofilament suture
Lid crease approach for excision of orbital rhabdomyosarcoma. (a) Mass pushing right globe down and out. (b) Right orbital proptosis secondary to tumor. (c) CT scan with axial view of orbital tumor demonstrating pressure on globe in same patient. (d) Coronal view of same patient. (e) Lid crease approach demonstrating mass in superonasal quadrant. (f) Traction suture elevating tumor; frozen section biopsy confirms rhabdomyosarcoma. (g) Further debulking of tumor assisted by use of cryoprobe. (h) Completion of debulking effort; significant tumor safely removed with care not to damage orbital structures. (i) Two-week post-op appearance. (j) Proptosis reduced at 2 weeks post-op. (k) Post-op CT axial scan at 2 weeks demonstrating reduction of tumor and improved position of globe. Chemotherapy regimen begun to be followed by course of orbital radiation. (l) Post-op coronal CT scan at 2 weeks
Lid crease incision for access to lacrimal gland, subperiosteal space, and mid-orbit
Subciliary Lower Eyelid Approach
A similar procedure can be performed through a subciliary incision in the lower eyelid. A myocutaneous flap is developed, revealing the orbital septum. Three fat pads exist in the lower eyelid: The temporal is the largest, the central is the smallest and borders the belly of the inferior oblique on its medial side, and the nasal is lateral to the lacrimal sac and borders the inferior oblique muscle on its lateral side (Fig. 37.5). Dissection deep into the intraconal space is best accomplished through the inferotemporal space. Inferior dissection in the preseptal space reveals the inferior orbital rim. Horizontal division and reflection of the inferior orbital periosteum allow access to the floor and inferomedial wall of the orbit. This approach provides good visualization of orbital floor, rim, and medial wall fractures. Additional details regarding lower lid approaches to the orbit will be presented in the section on inferior orbitotomy.
Alternatively, the inferior subperiosteal space may be reached through a lower lid transconjunctival approach (Figs. 37.11, 37.12, and 37.13). This approach avoids altogether a scar associated with the skin incision and minimizes the risk of vertical eyelid retraction, which is occasionally encountered with the subciliary approach. In the subciliary approach, a lateral canthotomy and inferior cantholysis are performed to release the lower lid laterally from its attachments to the lateral orbital rim. A 4–0 silk lid margin suture is used to reflect the lid. The conjunctiva is incised horizontally approximately 5 mm inferior to the inferior tarsal border. Using monopolar cautery, the lower lid retractors are incised and blunt retraction used to expose the orbital periosteum, which is opened as described above (Fig. 37.14). This transconjunctival incision can be extended behind the caruncle to provide greater exposure of the medial orbital wall. Care must be taken not to damage the lacrimal sac with this dissection.
Transconjunctival incision. The transconjunctival incision is marked by a dotted line 3 mm below the inferior border of the tarsus. It is an alternative to a subciliary incision for access to the inferior orbit. The incision can be carried laterally to divide the lateral canthal angle in order to provide greater exposure when required. It can also be extended medially as a transcaruncular approach for access to the medial intraconal, extraconal, or subperiosteal spaces
Canthotomy and cantholysis . Further exposure is achieved by performing a canthotomy and cantholysis, which releases the inferior crus of the lateral canthal tendon
Traction suture . A 4–0 silk traction suture is placed beneath the inferior rectus muscle to aid in rotating the globe and identifying the inferior rectus muscle intraoperatively. The conjunctival incision can be made with either blade scissors or a needle point electrocautery
Dissection of the subperiosteal plane . The dissection of the subperiosteal plane is facilitated by use of malleable retractors, which in this case demonstrates prolapsed fat through an orbital fracture
In the above cases, the periosteum is closed with interrupted absorbable sutures, as is the conjunctiva in the transconjunctival approach. The lid is reattached to the posterior lateral orbital periosteum with 4–0 absorbable sutures and the skin closed with absorbable suture material. The orbital septum and orbicularis muscle are not sutured closed, as this may contribute to postoperative lid retraction.
Bulbar Transconjunctival Orbitotomy
The bulbar transconjunctival approach (Figs. 37.15, 37.16, and 37.17) provides direct access to the intraconal, sub-Tenon’s, and subarachnoid spaces. Posteriorly located lesions can be more easily reached surgically if the bulbar transconjunctival approach is combined with a lateral orbitotomy (described below). This allows the globe to be rotated temporally into the defect in the lateral wall of the orbit. Lesions in these spaces include cavernous hemangioma, lymphangioma, schwannoma, neurofibroma, metastatic disease, and optic nerve lesions.
Bulbar transconjunctival orbitotomy . A transconjunctival incision is made perilimbal for approximately 90° through both conjunctiva and Tenon’s capsule. This can be extended behind the caruncle for greater exposure to the intraconal, extraconal, and subperiosteal spaces of the medial orbit
Access to the medial intraconal space. The medial rectus muscle is disinserted from the globe, and a suture is placed in a continuous running fashion through the stump of the tendon. Curved scissors are used to open posterior Tenon’s capsule. With the globe rotated laterally and the medial rectus muscle pulled medially, ready access is available to the medial intraconal space
Optic nerve sheath decompression . (a) Using malleable retractors and blunt dissection with cottonoids the optic nerve can be identified. For optic nerve sheath decompression, the sheath is opened with a myringotomy-type sickle or MVR blade. (b) A small muscle hook can then be used to break up any septations between the pia matter and the dura which then can permit better outflow of CSF fluid in order to decompress pressure on the optic nerve. The inset shows a complete window cut in the nerve sheath using neurosurgical micro-scissors and forceps and the aid of an operating microscope. The sickle blade can also be used to make two or three linear incisions
The operation may be performed either nasally or temporally. To reach the intraconal space, insufficient room exists to provide access via the inferior or superior transconjunctival routes.
A lid speculum is placed between the eyelids, and a 90° conjunctival peritomy is performed nasally. Relaxing incisions are made inferonasally and superonasally and the ends of the conjunctiva are marked for easy identification at the conclusion of the case (Fig. 37.15). The medial rectus muscle is isolated on a muscle hook, and a double-armed 6–0 Vicryl suture is passed in a double-locking fashion through the muscle belly approximately 2 mm posterior to the insertion of the muscle to the globe. The muscle is disinserted anterior to the suture and the ends of the suture secured with a seriphine. A 5–0 silk or Mersilene suture (Ethicon) is woven through the insertion of the medial rectus muscle and used to rotate the globe temporally (Fig. 37.16). The lid speculum is removed and the intraconal space entered bluntly with Q-tips and malleable retractors. A variety of self-retaining retractors have been devised for use in this region. We generally do not require their use, but we employ neurosurgical Greenberg retractors when stable retraction is desired.
If anteriorly located in the intraconal space, the tumor may be removed bluntly as classically described with the assistance of a cryoprobe to provide traction; however, we have come to prefer 4–0 silk traction sutures as they produce the same traction but do not obstruct visualization of the small surgical field as can occur when the cryoprobe is employed. We limit the use of sharp dissection to limit injury to surrounding structures. Magnification with a neurosurgical operating microscope is particularly helpful for dissecting less well-encapsulated lesions (i.e., lymphangioma) from the surrounding tissues. When required, a laser may be delivered through the microscope. As mentioned earlier, if more posterior exposure is required, a lateral orbitotomy may be performed to allow the globe to reflect laterally into the temporalis fossa. If access to the optic nerve is required, posterior Tenon’s capsule must be opened with blunt-tipped Westcott scissors and the optic nerve isolated with long Q-tips. Nerve sheath fenestration and biopsies are performed nasally in this fashion (Fig. 37.17).
After the lesion has been removed and hemostasis secured with irrigation and bipolar cautery, the traction suture is removed, the original insertion of the medial rectus muscle is trimmed from the sclera, the medial rectus muscle is reattached to the globe, and the conjunctiva is closed with a fine absorbable suture.
Surgical Approaches to the Posterior Orbit
To access deeper lesions in the orbit when an anterior approach is inadequate, reference to the nearest orbital wall is an important consideration. In such cases, the orbital wall may serve as a guide to reach more posterior portions of the orbital space of concern. One or more orbital walls may also require removal in order to provide sufficient access.
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The lateral nasal/Lynch approach to the orbit permits access to the medial wall of the orbit from the frontoethmoidal suture to the ethmoidal-maxillary suture and as far posterior as the sphenoid sinus if the ethmoid air cells are removed (Fig. 37.18). Both the subperiosteal and extraconal spaces may be entered through this approach. The most common lesion encountered in the subperiosteal space of the nasal orbit is a subperiosteal abscess. Less common are lesions arising from the ethmoid sinus (i.e., mucocele, osteomas, neuronal tumors, and hemangiopericytomas).
Modified lynch incision . The central “V” reduces the chance of web formation in the medial canthal region
A more recently described approach to the medial orbit is via the transcaruncular incision. This transconjunctival approach provides equal access to the medial surgical space when compared to the Lynch incision without the cutaneous scar. The incision begins approximately 1 cm more posteriorly than the Lynch incision and thereby limits the surgical dissection required. The only clinical scenario, which may favor a Lynch approach, is an orbital abscess that requires postoperative drainage. In this case, percutaneous drainage through the conjunctival incision is impractical. Both procedures are described below.
An alternative approach to the medial orbit is trans-nasally via endoscopy (see Chap. 8). This can be combined with oculoplastic approaches to the inferior, lateral, and superior orbit as in orbital bone decompression for thyroid ophthalmopathy.
A vertical curvilinear incision is marked along the thick skin of the lateral aspect of the nose and injected with 0.5% Lidocaine with epinephrine. A skin incision is made with a #15 blade, and the muscle is divided with a coagulating Bovie cautery. The periosteum is incised with a blade, and a periosteal elevator is used to bluntly develop the subperiosteal plane (Fig. 37.19) (see also Chap. 8). A subperiosteal abscess is easily drained in this fashion (Fig. 37.20). Care should be taken not to damage the medial canthal tendon or, if dissection is carried superiorly, the trochlea. If either tendon is reflected with its associated periosteum, simple closure of the periosteum at the conclusion of the case will restore normal function to both structures. Approximately 20 mm posterior to the orbital rim is the anterior ethmoid artery, followed 10 mm still further posterior by the posterior ethmoid artery. Both should be carefully cauterized or ligated with clips prior to division. The arteries also serve as important landmarks of the cribriform plate.
Periosteal incision. The dissection is carried through the skin and orbicularis muscle, and the angular vessels are reflected or cauterized. The periosteum is incised and reflected with a periosteal elevator
Subperiosteal abscess opened and drained
Ethmoidectomy is performed by entering the anterior ethmoid air cells with either a drill or more commonly a curved clamp. The air cells are then removed in sequence from an anterior to posterior direction with pituitary forceps. If required, the frontal sinus may also be entered. Unless the wall of the sinus has been destroyed by a tumor or mucocele, a drill is generally required to penetrate the bone. In both cases drainage into the nose after sinus resection is advisable to prevent recurrent sinus infection. This is produced by introducing a clamp or rongeur through the sinus into the nasal antrum. To maintain patency of the opening, a drain is kept in place postoperatively for several days.
If access to the extraconal space is required through this incision, this can be achieved by incising the periosteum. To avoid injury to the medial rectus muscle, it is helpful to have a suture beneath the belly of the muscle. Traction on the muscle will produce a dimple in the orbital periosteum and help to identify the location of the muscle. The periosteal incision should be made in the horizontal plane either superior or inferior to the belly of the muscle. Dissection then proceeds bluntly with Q-tips and malleable retractors within the intra- and extraconal spaces.
At the completion of the surgery, the deep and superficial periosteal layers are closed with interrupted absorbable sutures. The skin is closed in two layers.
Transconjunctival (Retrocaruncular) Incision for a Medial Orbitotomy
To access the medial wall via the conjunctival , an incision is made either just posterior to the caruncle or by splitting the caruncle as initially described. With the caruncle on traction, a Westcott scissor is used to make a curvilinear incision of the conjunctival to the superior and inferior nasal quadrants. Again with the caruncle on traction, a curved Stephens scissor is used to bluntly dissect to the medial wall of the orbit in the avascular plane just posterior to the lacrimal sac to expose the periosteum just behind the posterior lacrimal crest. The periosteum is incised and reflected with a periosteal elevator (Fig. 37.21). The perforating anterior and posterior ethmoidal neurovascular bundles can be cauterized and divided as described above. Access from the subperiosteal space to the intraorbital extraconal and inferior or superior intraconal spaces are accessible upon dividing the periosteum longitudinally. After completion of the surgical procedure, closure is accomplished simply with 8–0 Vicryl sutures.