Abstract: We identified two randomised trials eligible for inclusion in the review. There was significant variability between the trials for interventions, methodology and outcome measures and therefore meta-analysis was not performed. One study suggested that the transantral approach and endoscopic transnasal technique had similar effects in reducing exophthalmos but that the endoscopic approach may be safer, relating to fewer complications. This study had short-term follow-up and lacked information on our primary outcome (success or failure of treatment). The second study provided evidence that intravenous steroids may be superior to primary surgical decompression in the management of compressive optic neuropathy requiring less secondary surgical procedures, although it relates more frequently to transient side effects. This study was weakened by a small sample size. Until more credible evidence is available recommendations as to best treatment cannot be reliably made. A single study showed that the transantral approach for orbital decompression was related to more complications than the endoscopic transnasal technique which is preferred by Ear, Nose and Throat (ENT) surgeons, usually as an adjunctive procedure. Intravenous steroids were reported in a single trial to be the most efficient intervention for dysthyroid optic neuropathy. The majority of published literature on orbital decompression for thyroid eye disease consists of retrospective, cohort, or case series studies. Although these provide useful descriptive information, clarification is required to show the relative effectiveness of each intervention for various indications. The two RCTs reviewed are not robust enough to provide credible evidence to our understanding of current decompressive surgery and to support recommendations for clinical practice. There is evidence from currently available uncontrolled studies that removal of the medial and lateral wall (balanced decompression) with or without fat removal may be the most effective surgical method related to only a few complications. There is a clear need for randomised studies evaluating the balanced two-wall, three-wall and orbital fat decompression techniques. Comparison with other surgical techniques for orbital decompression or with immunosuppression in cases of compressive optic neuropathy would also be important. These studies should primarily address the reduction of exophthalmos, disease severity, complication rates, quality of life and cost of the intervention.

Plain-language summary: Two eligible studies were included in the review. These studies vary significantly in interventions, methodology and reported outcomes. One study reported that removal of the inferior wall through the antrum and removal of the medial wall through the nose had similar effects in reducing exophthalmos but the latter had fewer complications. This study was disadvantaged by short-term follow-up and did not report on our primary outcome measure (success or failure of treatment). The second study suggested that intravenous corticosteroids achieve better visual recovery (56%) than surgical decompression (17%) as a first line treatment for optic neuropathy. It suggested that fewer secondary surgical procedures were required when treated with intravenous corticosteroids but their use related more frequently to side effects with short duration. This study was weakened by the small number of participants involved. Until more evidence is available we cannot recommend any particular intervention. This review has identified a need for more randomised controlled trials to provide further reliable evidence on the effective use of orbital decompression for thyroid ophthalmopathy. These trials should review the balanced two-wall, three-wall and orbital fat decompression techniques. These studies should address the reduction of exophthalmos, disease severity, complication rates, quality of life and cost of the intervention.