Orbital decompression is the partial or complete removal of one or more, of the four walls of the orbit (eye socket). This procedure is primarily performed for Graves' disease (thyroid eye disease). Graves' disease frequently includes some combination of thyroid disease, bulging of the eyes (exophthalmos), lid lag, retraction of the eye lids and double vision (diplopia).
These findings are due to a lymphocytic infiltrate involving the eye muscles and fat. As this process progresses, the fixed orbital walls are unable to accommodate the enlarging eye muscles and fat. More rarely, the expansion of the orbital contents in the posterior eye socket, also known as the orbital apex, compresses the optic nerve. As the optic nerve is compressed the patient first looses color vision, followed by loss of peripheral vision, and finally blindness (Schaefer, 2003).
Axial CT scan of a patient with thyroid eye disease. Several of the elements of this disease are evident on this image: 1) exophthalmos or protrusion of the eye ball from the orbit, and 2) enlargement of the extraocular muscles, including the medial rectus (mr). Also seen are some less common variations of sinus anatomy. Specifically, a posterior ethmoid cell (EC) has extended into the sphenoid bone to pneumatize the area around the optic nerve.
Early and mild thyroid eye disease is often successfully treated by suppression of the primary thyroid disease with medications and/or radioactive iodine (I131), and oral steroids. As the disease worsens, the cornea is exposed by retraction of the eyelids. At this point, treatment is directed towards protecting the eye and many ophthalmologists will first recommend surgical lengthening of the eyelids. With exophthalmos, the patient often finds their appearance unacceptable and orbital decompression should be considered. In our opinion, once double vision or compromise of vision has occurred, orbital decompression is clearly indicated (Schaefer, 2003). We reserve radiation therapy of the orbit for those patients who refused surgery or are unable to tolerate surgical treatment (Gorman, 2002).
Four types of orbital decompression have evolved over the past century. These consist of:
- Removal of the lateral wall or Kronlein procedure,
- Removal of the superior wall or Naffziger procedure
- Removal of the medial wall or Sewell procedure, and
- Removal of the floor of the orbit by either an external or transantral (via the maxillary sinus or Walsh-Ogura procedure) approach.
More recently, orbital decompression may be performed via an intranasal endoscope route with removal of one or more walls of the eye socket (Kennedy, 1990; Metson, 1994; Schaefer, 2003).
Coronal cadaver section illustrating the four types of orbital decompression. These are: (1) removal of the superior wall (Naffziger), (2) medial wall removal (Sewell), (3) lateral wall removal (Kronlein), and (4) removal of the floor of the orbit.
Optic nerve decompression is the partial or complete removal of the bone surrounding the optic nerve. This procedure is controversial, and is primarily employed for trauma to the optic nerve resulting in compromised vision. Even less frequent, partial optic nerve decompression is utilized in thyroid eye disease with optic neuropathy.
The results of optic nerve decompression vary with the indications, the experience of the surgeon, the length of time between visual compromise and the indications for the surgery (Sofferman, 1991; Schaefer, 2003).