Surgical Exploration of the Orbit

The orbit comprises the globe and optic nerve surrounded by a complex tangle of muscles, nerves, and vessels, all cushioned in pockets of fat. While surgery in the anterior orbit is readily performed, the challenge increases significantly for deeper orbital pathology because the bony walls on four sides and the eyeball and lid structures anteriorly limit both access and visibility. The apex is a particularly difficult area because so many vital structures converge in its narrow confines. The history and physical examination help narrow the differential diagnosis so that appropriate imaging and special investigations may be arranged. The urgency of these diagnostic tests to allow appropriate medical or surgical intervention is partly determined by the speed of symptom onset and by the presence of significant pain or progressive functional impairment such as vision loss or diplopia. Computed tomography (CT) scans are usually readily available and help define the tissue characteristics and location of an orbital lesion. Reformatting allows coronal, sagittal, and 3-D views without repositioning the patient, although a true coronal CT scan may be requested if a distensible varix is suspected. Contrast CT scans may be useful for assessing the vascularity of the lesion but require an evaluation of renal function. Magnetic resonance (MR) scans may characterize certain soft tissue features better, identifying fluid levels and determining whether a lesion involves normal anatomic structures such as the optic nerve, muscle, or lacrimal gland. They are particularly useful in evaluating lesions of the optic nerve and chiasm. Ultrasounds may help to define certain superficial orbital lesions (distinguishing a lymphoma from a pleomorphic adenoma in the lacrimal gland, for example) and are very useful in assessing intraocular pathology. Positron emission tomography (PET) scans may help determine the presence of recurrent malignancy or lymphoma in a previously operated or treated site and whole body evaluation may be helpful for staging lymphomas. A trained neuroradiologist can help interpret a complex image. In general, well-circumscribed, accessible lesions are excised in toto. Poorly defined, infiltrative lesions and those causing tissue destruction (suggestive of malignancy or aggressive inflammation) usually are biopsied, either by needle or with surgery.