Surgical Approaches to the Orbit

Anterior Versus Deep Tumors

The anterior-posterior position of a mass within the orbit is the most important factor to consider in choosing a surgical approach. Tumors anterior to the equator of the eye are most commonly approached from the front of the orbit using a type of anterior orbitotomy. Tumors posterior to the equator of the eye require more advanced deep surgical approaches. The choice of orbitotomy for deep tumors depends on the relationship of the tumor to the optic nerve.

Relationship To the Optic Nerve

A fundamental principle of orbital surgery is

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  Choose an orbitotomy approach that avoids crossing the optic nerve

Following this guideline, deep orbital tumors lateral to the optic nerve are approached with a lateral orbitotomy approach. Removal of the lateral orbital wall provides excellent access to these tumors.

Deep tumors medial to the optic nerve are more difficult to reach because there is no bone that can be easily removed to provide good exposure and access. The surgical spaces of the medial orbit can be reached through deep medial orbitotomy approaches, through either the eyelid or the conjunctiva. Access to the apical medial orbit from these anterior orbitotomy approaches is limited. In unusual situations, the medial orbital wall may be removed and limited access to the deep medial orbit can be obtained ( Figure 15.4 ).

Type of Biopsy

The surgical approach may be influenced by the goal of the operation. It is easier to perform an incisional biopsy through a small incision than it is to perform an excisional biopsy. For example, an incisional biopsy of the optic nerve can be performed through either a transconjunctival anterior orbitotomy or a lateral orbitotomy approach. Excision of the entire optic nerve, however, requires a much wider area of exposure, usually provided only by a transcranial orbitotomy approach. You can see that the intent of the operation is a factor in your choice of orbitotomy approach ( Table 15.1 ).

Surgical Spaces of the Orbit

The surgical spaces of the orbit, already discussed in Chapter 2, Chapter 13 , are

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  Intraconal space

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  Extraocular muscles

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  Extraconal space

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  Subperiosteal space

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  Tenon’s space

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  Extraorbital space

You should already know these spaces ( Figure 15.5 ). This section is intended as an illustration of how you can begin to think of the spaces of the orbit and their relationship to the orbitotomy approach. Don’t memorize the specific pathologic processes and approaches mentioned here. We talk about them again later in this chapter. Just start to get an idea of how you are going to choose the orbitotomy approach, based on the position of the pathologic process and what you have already learned in this chapter.

The extraconal space contains the lacrimal gland, superior oblique muscle and trochlea, and nerves and vessels in the extraconal orbital fat. An enlarged lacrimal gland is often palpable in the upper lid and then is readily accessible through an anterior orbitotomy using the upper lid skin crease approach. Lymphoid tumors are among the most common orbital masses. Because lymphomas tend to occur in the lacrimal gland or elsewhere anteriorly in the extraconal fat, anterior orbitotomy approaches to the extraconal space are commonly used. When a lacrimal gland mass is not palpable (mostly posterior to the globe), a lateral orbitotomy, usually with bone removal, is required. The superior oblique muscle and trochlea are in the medial portion of the extraconal space, but rarely require biopsy. Schwannoma of the frontal nerve may be seen in the superonasal quadrant and can be approached anteriorly, but if the mass extends into the apex, a transcranial approach may be necessary for removal. The anterior portion of the superior ophthalmic vein lies in the extraconal space, but it almost never requires surgical intervention.

The intermuscular septum lies between the anterior portion of the extraocular muscles, separating the intraconal and extraconal spaces. The muscles may become involved in neoplastic or inflammatory processes. The most common condition is thyroid orbitopathy. Painful inflammation of the muscles, myositis, may also occur. Primary neoplasms of the muscles are very rare, but metastatic lesions do occur. Although biopsies are not often performed on the extraocular muscles, the muscles can be approached surgically through anterior orbitotomy incisions if the pathologic lesion is anterior. If the enlargement of the muscle is posterior, you can decide on the best approach for incisional biopsy following the principles described in the previous section. The extraocular muscles are important surgical landmarks to guide your surgical dissection. During lateral orbitotomy approaches, the intraconal space is usually entered between the lacrimal gland and the lateral rectus muscle. We discuss this dissection technique further in the section Approach to Deep Lateral Lesions: The Lateral Orbitotomy.

The subperiosteal space is the potential space between the orbital bones and the periorbita. A hematoma may collect in this space from an adjacent fracture. A collection of pus, a subperiosteal abscess, may collect medially from an adjacent ethmoid sinus infection. For drainage of a subperiosteal abscess, you usually approach the medial subperiosteal space anteriorly through the skin and conjunctiva with elevation of the periorbita from the orbital rim and dissection posteriorly along the medial orbital wall (frontoethmoidal and transcaruncular anterior orbitotomy). Repair of orbital floor fractures begins with surgical approaches to the subperiosteal space using transconjunctival or transcutaneous lower eyelid anterior orbitotomy techniques. Similarly, you can approach medial wall fractures using the transcaruncular anterior orbitotomy technique.

The Tenon’s space lies between the eye and the fibrous capsule, or Tenon’s capsule, which surrounds all but the anterior portion of the eye. You may have already operated in this space when performing an enucleation or scleral buckle procedure. Although we usually don’t think of it, these operations start with a transconjunctival anterior orbitotomy. Tenon’s space is rarely involved in pathologic processes; one example is the extraocular extension of a choroidal melanoma.

The extraorbital space includes all the tissues surrounding the orbit: bone, brain, sinus, nasal tissues, skin, and conjunctiva. You are already familiar with some of the many problems that originate in these tissues and involve the orbit secondarily. For many of these tissues, the surgical approach is obvious, whereas for others, decisions require input from other surgical specialties for which interdisciplinary cooperation is essential to the success of the operation.

We talk about the orbital spaces in the context of the orbitotomy procedures again and again throughout this chapter; so start thinking of these spaces in the context of orbitotomy approaches.

Names of Orbitotomy Approaches

There is no consistent nomenclature or classification of orbitotomy approaches. Most of the names used in this text and by other surgeons are descriptive. You shouldn’t memorize these terms because they can mean different things to different people. Some commonly used descriptive terms and my interpretation of them are

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  Anterior orbitotomy means that the approach is from the front of the orbit, usually through the eyelid or conjunctiva. In general, an anterior orbitotomy approach does not involve bone resection.

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  Lateral orbitotomy means that the approach is from the lateral side of the orbit. In general, the term lateral orbitotomy implies that the lateral rim will be removed. A lateral orbitotomy can be performed through a small skin incision at the lateral canthus without any bone removal.

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  The terms anterior and deep are opposite. The term superficial orbital tumor is not used. Anterior tumors are palpable and accessible by the anterior approaches. Deep is usually used to describe posterior tumors in the orbit.

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  Anatomy accessible only via transcranial orbitotomy includes the posterior one third of the orbit, superior orbital fissure, sphenoid wing, and chiasm.

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  Deep tumors are posterior to the globe. I use the term deep medial anterior orbitotomy for approaches to intraconal tumors medial to the nerve. As we discussed above, the lateral orbitotomy is used for approaches to deep tumors lateral to the nerve.

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  Apical implies the posterior one third of the orbit. I use the term orbitocranial to describe tumors involving the orbital apex and optic canal, chiasm, superior orbital fissure, or other intracranial structures. The transcranial orbitotomy is used to approach apical or orbitocranial tumors. The terms superotemporal orbitotomy and panoramic orbitotomy are types of transcranial orbitotomy approaches.

Room Setup

You should have a plan for the setup of the room and any specialized equipment required. If you anticipate using an operating microscope, it should be positioned and adjusted while the patient is being prepared. Any pathology requisitions should be filled out before you start the surgery. You should discuss the plan for operation with the nursing staff before beginning the procedure.

Orbital Instruments

Specialized orbital instruments are used ( Box 15.1 ). Retraction of skin is necessary, using small (Storz double-fixation forceps) or large (Joseph) skin hooks and suture retractors (4-0 silk). Retraction of the orbital fat is facilitated with Sewall and malleable ribbon retractors of various lengths. Neurosurgical cottonoids placed under the retractors prevent fat prolapse into the surgical wound. A variety of periosteal elevators should be available, including Freer, Joseph, and Dean elevators. Bone removal equipment, including a power saw, drill, and bone rongeurs, is necessary if deep orbitotomy procedures with bone removal are anticipated. A microplating system is useful to repair complex orbital bone cuts. A Freer elevator or a long cotton-tipped applicator is a useful orbital dissection tool. Small neurosurgical dissectors can be helpful.