Tutorial
Introduction
Preoperative Considerations
Surgical Planning
Technique
Postoperative Considerations
Results
Complications
Conclusion
Bibliography

Slides

Orbital Decompression for Thyroid-Related Orbitopathy

Nattawut Wanumkarng, MD · Karim Punja, MD · Don O. Kikkawa, MD

Introduction

Thyroid-related orbitopathy (TRO) is clinically relevant in approximately 50% of patients with Graves' disease. However, only 3% to 5% of patients develop serious complications that require surgical intervention. In most cases, the onset of the orbitopathy is concomitant with the onset of hyperthyroidism, but eye involvement may precede or follow hyperthyroidism. Typically, orbital surgeons intervene during the stable portion of the disease unless vision-threatening complications develop.

TRO is an autoimmune reaction that leads to the activation of pre-adipocyte fibroblasts and deposition of glycoaminoglycans (GAG) during the acute phase. Orbital fibroblasts are phenotypically unique and in patients with TRO, orbital fibroblasts can be stimulated to secrete GAG at a rate 100-fold higher than normal extraorbital fibroblasts.

As a result, the orbital soft tissues undergo volume expansion. Symptoms may include deep orbital discomfort, tearing, decreased visual acuity, and diplopia. Typical signs are eyelid retraction, periorbital edema, proptosis, and restrictive strabismus. Severe proptosis or crowding of the orbital apex from enlarged extraocular muscles may result in progressive loss of vision from compressive optic neuropathy requiring urgent surgical intervention.

Two clinically distinct subtypes of TRO are recognized: type 1 and type 2. Patients with type 1 disease have increased orbital fat without restrictive myopathy. Patients with type 2 disease have enlarged extraocular muscles, typically with restrictive myopathy. TRO has a spectrum of presentation and although it may be clinically useful to categorize patients as type 1 or type 2, it should be recognized that some individuals may represent a combination of the types.

Three phases exist in the disease:

1. Inflammatory phase (marked by worsening)
2. Regression phase (marked by spontaneous improvement)
3. Stability phase

In the inflammatory phase, the soft tissues and muscles around the eye become swollen and congested. This may last for 12 to 18 months. In the inflammatory phase, the treatment for TRO is observation and medical therapy. If inflammatory findings (e.g., eyelid edema and chemosis) are severe and symptomatic, systemic steroids or orbital radiotherapy should be considered.

The inflammatory response typically abates, with symptoms and signs gradually receding over a 1- to 3-year period. Proptosis, lid lag, and swollen eyelids become less severe. Most of the time, however, a complete regression does not occur. Between 3% to 8% of patients develop severe sight-threatening complications from exposure keratopathy or optic neuropathy.

After regression is a period of stability. In this phase, planned surgical rehabilitation should occur. Factors that dictate more immediate intervention include vision-threatening complications.

Progressive exophthalmos from TRO may result in marked disfigurement and discomfort from deep orbital pressure. The social and psychological impact from this disfigurement rivals the depression seen in severe medical conditions such as cancer.

Orbital decompression is an effective way to reduce exophthalmos. The traditional indications for this operation (i.e., optic neuropathy and corneal exposure) are expanding. Various techniques of both bony and fat decompression have evolved to accomplish this goal while minimizing adverse effects. In experienced hands, the complications of this operation are rare and treatable.

Planned surgical rehabilitation is staged. Orbital surgery is performed first, followed by strabismus surgery, and finally lid surgery. Any step may be skipped if not necessary. Orbital decompression is directed toward two goals - expanding orbital volume (bony expansion) and reducing orbital soft tissue (fat decompression).

Current indications for orbital decompression are:

• Compressive optic neuropathy
• Exposure keratopathy
• Spontaneous globe prolapse
• Disfigurement
• Discomfort due to orbital pressure/pain
• Preparation for strabismus surgery (typically in unilateral cases in which strabismus surgery would cause a worsening of proptosis by allowing the globe to come further forward from muscle recession)
• Preparation for eyelid retraction surgery in which lid retraction repair alone will not suffice in allowing proper globe coverage
• Orbital congestion

Preoperative Considerations

Patients being considered for orbital decompression should have high-resolution orbital computed tomograph imaging in the axial and coronal planes. Several factors should be examined including:

• Presence of sinus disease (sinuses should be clear)
• Size of extraocular muscles (type 1 or type 2 orbitopathy)
• Thickness of bony walls (particularly the deep lateral wall)
• Position/angle of the cribriform plate in relation to the medial orbital wall (this is important if medial wall decompression is to be performed)

Standard preoperative medical clearance should be performed, including thyroid function and coagulation studies.

An accurate exophthalmometry reading, preferably with the Hertel and Naugle devices, should be obtained. The Naugle device makes measurements based on the superior and inferior orbital rims and is useful if surgery is performed to advance the lateral orbital rims.

External photographs should be taken, including the nine positions of gaze, full face and profile views, and a view from above and below showing the amount of globe protrusion.

A thorough discussion of risks, benefits, and alternatives to the planned surgery should be undertaken. The risk of surgically induced diplopia varies with different studies. It has been quoted to be anywhere from 10% to as high as 60%. Blindness has been reported but is rare. Hypesthesia, sinusitis, infection, and bleeding should also be mentioned.

Surgical Planning

Orbital decompression can be categorized into three types:

• Removal of bone from one or more walls of the orbit
• Removal of orbital fat, including intraconal fat
• A combination of bony and fat removal

In our experience, the indications for fat decompression only are few. In some patients with type 1disease with mild proptosis, fat only decompression can be useful. Most of the orbital decompressions that we perform combine fat and bony removal.

Our approach to orbital decompression is based on several factors. The most important determining factor is the amount of proptosis. Absolute and relative proptosis are important. Absolute proptosis readings refer to the amount in millimeters present preoperatively. Relative proptosis refers to cases of unilateral disease and also the amount relative to patients in their normal state. It is unfortunate that, for most people, pre-disease measurements in bilateral cases are not routinely measured, so the clinician must rely on photographs or tables of "normal values."

Historically, orbital decompression was believed to reduce proptosis measurements by approximately 2 mm per wall. Traditionally, the orbital floor and medial orbital wall were the first walls removed. Recently, a trend toward deep lateral wall decompression as the first choice in bony removal has occurred.

The benefit of lateral wall removal is less induction of strabismus. If further decompression is required, then the medial wall is removed in a balanced fashion to symmetrically retroplace the orbital tissues from each side, thereby in theory also reducing the induced strabismus by balancing the muscle pull.

If further proptosis reduction is necessary, then the orbital floor is addressed. In our opinion, orbital floor removal is associated with some of the most severe complications (e.g., globe ptosis, worsening hypotropia, supraduction deficit, and infraorbital hypesthesia) and we reserve it as the last wall to be removed.

Presently, our approach is as follows:

• For exophthalmometry less than 22 mm, we perform lateral wall and fat decompression.
• For exophthalmometry between 22 mm and 25 mm, we perform lateral wall, fat, and medial wall decompression.
• For exophthalmometry greater than 25 mm, we perform lateral wall, fat, medial wall, posterior orbital floor decompression, and lateral rim advancement.

Technique

Patients undergoing decompressions are under general anesthesia. For lateral wall decompression, an upper lid crease incision is made within the pre-existing lid crease. A sub-periosteal dissection plane is created. A high-speed 3-mm diamond burr is used to remove portions of the greater wing of the sphenoid. Lesser amounts can also be removed from the area surrounding the inferior orbital fissure and the lacrimal gland fossa. The dura is routinely exposed but not penetrated.

For medial wall decompression, access is gained via a transcaruncular incision. The inferior oblique is tagged and disinserted if necessary. Lamina papyracea is removed along with portions of the anterior, middle, and posterior ethmoidal air cells. Sphenoidotomy is performed if necessary to completely decompress the orbital apex. Communication from the ethmoid sinus to the nasal cavity is maintained to prevent postoperative sinusitis.

Orbital floor decompression is performed via the inferior fornix/transconjunctival approach. The posterior one-half of the orbital floor is removed laterally to the level of the infraorbital nerve and medially to join the medial wall decompression. Anteriorly the maxillary-ethmoidal strut is maintained. The lower lid retractors are recessed primarily in patients with pre-existing lower lid retraction.

For fat decompression, this is performed after fenestrating the lateral periorbita. Intraconal fat is removed. If a transcaruncular/transconjunctival approach is used for the medial wall or floor, additional orbital fat can be removed from the inferomedial quadrant of the orbit. Approximately 4 mL of fat can be removed (particularly in type 1 patients).

Postoperative Considerations

Presently, my colleagues and I perform orbital decompression unilaterally as an outpatient procedure. Patients are discharged after several hours of observation and checked the next day. Routine postoperative medications include oral antibiotics, steroids, analgesics, and ointment. Cold compresses are used. Patients and family members are taught vision checks and are informed to call immediately with signs of worsening vision, increased bleeding, or pain.

Results

In our study published in Ophthalmology in July 2002, we found that the average proptosis reduction was:

1. Lateral wall and fat decompression: 4.8 mm
2. Lateral wall, medial wall, and fat decompression: 6.0 mm
3. Lateral wall, medial wall, floor and fat decompression with lateral rim advancement: 8.9 mm

SLIDE 1

SLIDE 2

Surgical outcomes vary among surgeons. The reasons are numerous, and it is impossible to extrapolate the results of one surgeon to others unless similar techniques are used. Even in one practice, many variables exist and hence the slides represent averages. Some of the variables are:

• Predominate type of disease (type 1 versus type 2). Patients with type 1 disease will have a greater proptosis reduction than patients with type 2 disease. It is thought that fat will occupy the expanded space easier than enlarged extraocular muscles, hence leading to a greater decompressive effect.
• Amount of extraocular muscle fibrosis. Patients with severely limited ductions generally have more fibrosis of their muscles and will also have less expansion into the newly created space.
• The size of the bony orbit. Some patients have shallow orbits with less bone to remove. This can be particularly true of the deep lateral wall that relies on the amount of bone removed and not on the adjacent air space of the sinus cavity.

Complications

Complications after orbital decompression are rare. In our study, no patients had optic neuropathy. Reported complications include:

• Postoperative diplopia and globe displacement
• Chronic sinusitis
• Cerebrospinal fluid leak (if detected intraoperatively, this is best sealed with fibrin glue)
• Meningitis
• Optic neuropathy
• Orbital cellulites
• Orbital hypesthesia/pain
• Hemorrhage
• Nasolacrimal duct obstruction
• Inadequate proptosis reduction

Conclusion

Orbital decompression surgery is a highly effective operation to reduce the symptoms associated with globe protrusion. A graded approach will lead to greater predictability of results in experienced hands. The preference of which wall to approach first appears to have swung in the direction of lateral first, then medial, then floor. Most of the complications are rare and treatable. Careful patient selection and improved surgical technique have led to a broadening of the indications for this rarely used procedure.

Bibliography

1. Fatourechi V, Garrity JA, Bartley GB, et al. Graves ophthalmopathy. Results of transantral orbital decompression performed primarily for cosmetic indications. Ophthalmology. 1994; 101:938-942.
2. Garrity JA, Fatourechi V, Bergstralh EJ, et al. Results of transantral orbital decompression in 428 patients with severe Graves' ophthalmopathy. Am J Ophthalmology. 1993; 116:533-547.
3. Goldberg RA, Kim AJ, Kerivan KM. The lacrimal keyhole, orbital door jamb, and basin of the inferior orbital fissure. Three areas of deep bone in the lateral orbit. Arch Ophthalmol. 1998; 116:1618-1624.
4. Kalmann R, Mourits MP, van der Pol JP, Koornneef L. Coronal approach for rehabilitative orbital decompression in Graves' ophthalmopathy. Br J Ophthalmol. 1997; 81:41-45.
5. Kikkawa DO, Pornpanich K, Cruz RC Jr, Levi L, Granet DB. Graded orbital decompression based on severity of proptosis. Ophthalmology. 2002: 109:1219-1224.
6. Kulwin DR, Cotton RT, Kersten RC. Combined approach to orbital decompression. Otolaryngol Clin North Am. 1990; 23:381-390.
7. Leone CR Jr, Piest KL, Newman RJ. Medial and lateral wall decompression for thyroid ophthalmopathy. Am J Ophthalmol. 1989; 1:160-166.
8. Lyons CJ, Rootman J. Orbital decompression for disfiguring exophthalmos in thyroid orbitopathy. Ophthalmology. 1994; 101:223-230.
9. McCord CD Jr. Current trends in orbital decompression. Ophthalmology. 1985; 92:21-33.
10. Olivari N. Transpalpebral decompression of endocrine ophthalmopathy (Graves' disease) by removal of intraorbital fat: Experience with 147 operations over 5 years [see comments]. Plast Reconstr Surg. 1991; 87:627-641; discussion 42-43.
11. Seiff SR, Tovilla JL, Carter SR, Choo PH. Modified orbital decompression for dysthyroid orbitopathy. Ophth Plast Reconstr Surg. 2000; 16:62-66.
12. Shepard KG, Levin PS, Terris DJ. Balanced orbital decompression for Graves' ophthalmopathy. Laryngoscope. 1998; 108:1648-1653.
13. Shorr N, Seiff SR. The four stages of surgical rehabilitation of the patient with dysthyroid ophthalmopathy. Ophthalmology. 1986; 93:476-483.
14. Trokel S, Kazim M, Moore S. Orbital fat removal. Decompression for Graves' orbitopathy. Ophthalmology. 1993; 100:674-682.