Optic Nerve Injury

Abstract

In Response: We appreciate the interesting comments from Drs. Roth and Roizen. However, we would like to address some of the issues they raised. 1) They discuss the proposal that the blood supply to the optic nerve is governed by autoregulation similar to that in the rest of the brain. However, the autoregulatory response appears to be decreased in aged primates fed an atherosclerotic diet [1]. The implication for elderly humans with atherosclerosis could be a possible risk of ischemic optic neuropathy (AION). While autoregulatory mechanisms have been identified in the circulations of the retina and optic nerve of primates, the prelaminar tissue of the optic disk, which is the site of ischemic damage in AION, has not been independently studied well enough to rule out an absence or relative inadequacy of such mechanisms. 2) We agree with their assertion that prolonged accidental pressure on the eye is likely to result in retinal dysfunction as well as optic nerve damage. We did state that in these cases retinal edema would be revealed by fundoscopic examination [2]. 3) We disagree that AION is as rare as Drs. Roth and Roizen believe. A recent survey of two academic centers reported four cases over a 2-yr period in patients undergoing prolonged spinal surgery [3], with another similar case being reported in the neurosurgical literature [4]. There has been no systematic study of the incidence of AION in patients undergoing general anesthesia, and since the onset of the disease may initially go unnoticed by the patient, it is not unreasonable to assume that cases occur without being detected during the immediate postoperative period. We still advocate that, when there is a probability of significant intraoperative blood loss and/or hypotension, particularly in patients reluctant to receive blood transfusion, the possibility of visual loss should be discussed preoperatively. 4) With respect to the postoperative visit, especially with patients who have sustained intraoperative blood loss and hypotension, a simple question such as "Can you see all right?" should be sufficient to ascertain any major visual changes. If the patient indicates there is a problem, early consultation may help to exclude other correctable causes and to reassure the patient that his or her concerns are being addressed adequately, although there is no known effective treatment for postoperative AION. 5) Regarding the results of the multicenter trial of optic nerve decompression, 42% of the patients with untreated AION did exhibit moderate improvement but not complete resolution [5]. We still believe that anesthesiologists need to be aware of this unpredictable and devastating complication for which there is no treatment. E. Lynne Williams, MB,BS, FRCA William M. Hart, Jr., MD, PhD Rene Tempelhoff, MD Department of Anesthesiology Washington University School of Medicine St. Louis, MO 63110-1093