Dilated superior ophthalmic veins and posterior ischemic optic neuropathy after prolonged spine surgery. 
A 55-year-old man developed bilateral posterior ischemic optic neuropathy after prolonged prone position lumbar laminectomy.  Brain MRI performed 19 hours after the procedure revealed markedly dilated superior ophthalmic veins, a finding that had disappeared on a comparable study performed 5 months later.  This first report of dilated superior ophthalmic veins present in the immediate postoperative period but not later may be important in suggesting that an increase in orbital venous pressure during surgery contributes to the development of postoperative posterior ischemic optic neuropathy (PION).