In this issue of the Journal, Liao and Huang describe their results from a prospective study involving orbital fat decompression in 22 patients (44 orbits) with thyroid eye disease (TED). They found predictable results in terms of proptosis reduction related to volume of resected fat and postoperative volume changes noted on computed tomography scanning. They conclude by stating that fat decompression can reduce a reasonable degree of proptosis in patients with disfiguring TED. We can now ask the question: Is a fat decompression a valid consideration for everyone with TED?

To better appreciate some of the complexities associated with management of patients with TED, one should consider some generalities. In a broad sense, many of the symptoms and signs of TED are related to a discrepancy between the amount of swelling of the retrobulbar tissues and the fixed volume of the bony orbit. The retrobulbar swelling can radiographically manifest primarily as an expanded fat compartment, an expanded extraocular muscle compartment, or, more commonly, expansion of both compartments. Efforts to prevent or reduce swelling of the retrobulbar tissues may fall short, and many times we still rely on either the possibility of spontaneous improvement, based on the natural course of the disease which can be associated with spontaneous improvement or various decompressive procedures to alleviate symptoms.

Decompressions are either bony decompressions or fat decompressions. The literature is more robust regarding bony decompressions. In general, the amount of proptosis reduction is proportional to the number of bony walls decompressed. The operation provides immediate relief of intraorbital pressure and reduces proptosis (approximately 4–5 mm for a 2-wall antral-ethmoidal decompression ). Surgery can be, and is probably most often, performed when TED is “active.” Indications for surgery include optic neuropathy, corticosteroid dependency, “inflammation” (persistent disease activity), pain, and the desire to reduce excess proptosis prior to strabismus surgery, in some instances prior to eyelid surgery, or in certain cases of disfiguring proptosis.

The side effects of bony decompression are well known and most notably include temporary infraorbital nerve hypesthesia (virtually 100%), cerebrospinal fluid leaks (<3%), and new-onset diplopia (up to 64%). While all side effects must be considered in light of intended benefits, it was notable that in our series of 428 orbital decompressions, 34 (8%) were done for disfiguring proptosis. Perhaps not surprisingly, this subgroup had the highest patient satisfaction results (unpublished data) despite the subsequent strabismus surgery that most required, giving further support to the impact that disfiguring proptosis has on quality of life.

Fat decompressions, by definition, are not associated with any bone removal, and therefore their potential for side effects such as infraorbital nerve hypesthesia, cerebrospinal fluid leaks, and diplopia are theoretically minimized. The quintessential indication for fat decompression is excess proptosis. The best candidate is a patient with inactive disease and an expanded fat compartment noted on neuroimaging. Fat decompression has also been performed for optic neuropathy. Kazim and associates reported favorable results from 5 patients with varying severity of optic neuropathy with an expanded fat compartment in whom extraocular muscle enlargement was not the sole cause of optic neuropathy. This group had also failed either orbital radiation therapy or a course of oral corticosteroids. Postoperatively, all cases had resolution of optic neuropathy with 1-year follow-up. One would not expect much of a therapeutic response in patients with primarily expansion of the extraocular muscle compartment with minimal expansion of the fat compartment.

Despite the claim that diplopia incidence is lessened with fat decompressions, diplopia is still a side effect of the procedure. In the largest series of fat decompressions (1635 patients) to date, Richter and associates noted temporary (lasting up to 6 months) new-onset diplopia in 29% of patients (127/440), and beyond 6 months eventually 20% of patients (89/440) underwent strabismus surgery, which was described thus: “The ensuing squint surgery in these cases showed adhesions between the extraocular muscles and the periosteum and indurated fibrotic extraocular muscles.” Indeed, we recently performed strabismus surgery on a patient with disabling, new-onset diplopia who had undergone fat decompression elsewhere and we noted similar findings regarding adhesions. Additionally, there were adhesions between the orbital fat and the globe itself. In our opinion, the diplopia seen in association with this procedure seems to be “different” in that the disrupted intermuscular septa cause more extensive restriction than that seen with bony decompressions and the diplopia is more difficult to fix.

Is it possible to ask too much of this procedure? Now that it has been shown that proptosis reduction is related to the amount of fat removed, can too much be removed? Also, does it make a difference (both for clinical effect and exposure to side effects) if it is retro-equatorial extraconal or intraconal fat removed? When should we consider perhaps removing less fat but adding bone decompression of the lateral wall? Koornneef elegantly demonstrated the existence of the intermuscular septae. Clinicians are acutely aware of the diplopia induced by orbital blow-out fractures, with prolapsed orbital fat (but not the muscle itself) causing diplopia. Our strabismus surgery colleagues assiduously avoid interfering with orbital fat for fear of inducing “fat adherence” syndromes. One must also recall that the intraconal orbital fat transmits numerous vessels and nerves capable of being injured in fat debulking surgery that may be too aggressive.

The mere fact that there are so many options for type and method of orbital decompression underscores that there is no single, best method. Orbital fat decompressions deserve a place in the therapeutic armamentarium, especially for patients with disfiguring proptosis and an expanded fat compartment, but as with any invasive procedure, benefits must be weighed against potential side effects. Fat decompressions are not for everyone.