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This is a review of patients undergoing a balanced two-wall and fat orbital decompression to identify risk factors for new onset diplopia. Standard decompression techniques were used, but as the surgery was conducted by ENT surgeons, the medial walls were decompressed via an endoscopic endonasal approach rather than a transcaruncular one, and in some cases part of the medial floor was also removed. Pre-existing diplopia and decompressions involving the medial wall and floor were already known to be risk factors for new onset diplopia in primary gaze (NOD PP), but the authors were keen to find any other risk factors particularly in those without preoperative diplopia in primary gaze. The study included 327 patients (612 orbits) of whom 126 had no preoperative diplopia. Of these, 43 (34%) developed NOD PP, due to worsening of elevation and abduction. New risk factors for the development of NOD included preoperative limitation of extraocular movements, enlargement of the medial rectus, and a greater reduction in proptosis. As medial rectus enlargement also correlated with dysthyroid optic neuropathy, the latter likewise was associated with NOD PP. As expected, those with preoperative diplopia in secondary gaze had a higher incidence of NOD PP than those without. It would be useful to know if those who had no surgery on the orbital floor avoided new-onset vertical diplopia, but this was not analysed by the authors. The study gives useful information regarding the risks of new-onset diplopia which will help in refining informed consent for surgery.

Risk factors for new onset diplopia after graduated orbital decompression.
Stahr K, Eckstein A, Buschmeier M, et al.
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James Hsuan

Aintree University Hospital, Liverpool, UK.

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