Orbital decompression may be performed under local or general anesthesia depending on the patient's preference, the surgeon's experience, the health and age of the patient, and the complexity of the proposed procedure.
Surgery begins with a careful examination of the nose. Total ethmoidectomy and antrostomy are first performed to expose the medial wall of the orbit or lamina papyracea, and to provide drainage of the maxillary sinus. The latter is necessary to avoid the subsequent obstruction of the maxillary sinus drainage by herniation of orbital contents into this sinus after removal of the orbital floor.
The entire lamina papyracea is then removed with a combination of micro-forceps, curettes and other instruments designed for this purpose. In our experience, at minimum patients undergo removal of both the medial wall and floor of the orbit.
The removal of the floor of the orbit can be accomplished either through an endoscopic, or transconjunctival (through an incision between the eyelids and eyeball frequently used for cosmetic eye surgery), approach. If the former approach is utilized, the next step in the decompression is removal of the floor of the orbit. If the latter is used, the endoscopic decompression is completed and the transconjunctival surgery is then performed.
In both approaches, a strut of bone at the junction of the medial wall and floor of the orbit is maintained to lessen the likelihood of over correction of exophthalmos. Finally, the periorbita or periosteal membrane separating the orbital contents from the sinuses is incised. This permits the orbital fat to expand into the ethmoid and maxillary sinuses, thus reducing the volume of fat within the eye socket and decompressing the orbit.
Intra-operative photo showing removal of the lamina papyracea during medial wall decompression of the left eye for Graves' disease. This patient has also undergone the removal of the anterior wall of the sphenoid sinus (SS) or sphenoidotomy to expose the orbital apex.
As this patient is also undergoing removal of the medial wall of the left optic canal, bone removal is continued into the sphenoid sinus (SS).
After completion of all bone removal, the periorbita is incised (arrow) to permit herniation of orbital fat into the ethmoid sinus. This step should always be performed after removal of all orbital bone because the fat would otherwise reduce visualization of the remaining bone.
Fat (arrow) is shown herniating through the incised periorbita into the ethmoid sinus. As the fat expands from the orbit into the sinus, the pressure or crowding of muscles and fat, is reduced.
Optic nerve decompression is performed with or without orbital decompression, depending on the etiology of the optic neuropathy. In those individuals undergoing orbital decompression, we recommend removing all bone comprising the medial wall of the orbit and optic nerve before incising the periorbita as illustrated.
As the optic canal is within the lateral wall of the sphenoid sinus, the anterior wall of this sinus must be removed to visualize the optic canal. A self-irrigating diamond burr is used to thin or "eggshell" the bone over the medial optic canal. The remaining bone is carefully removed to avoid injury to the optic nerve using the same techniques that have been developed for decompression of the facial nerve for trauma induced paralysis.
Self-irrigating diamond burr is shown thinning the bone over the medial optic canal (arrow) in optic nerve decompression. Immediately posterior or behind this site is the internal carotid artery which is a major arterial supply to the brain. Therefore, such surgery is performed with great care.
Optic nerve decompression is complete with the removal of the remaining thinned bone over the optic nerve with micro-curette or other instruments designed for this purpose. We do not recommend removing all of the bone with a diamond burr because of potential injury to the optic nerve by the burr.
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