A wide range of conditions from simple corneal abrasion to blindness have been reported. Corneal abrasion is by far the most common and transient eye injury. The ASA Closed Claims Project identified a small number of claims for abrasion, in which the cause was rarely identified (20%) and the incidence of permanent injury was low (16%). It also identified a subset of claims for blindness that resulted from patient movement during ophthalmological surgery. These cases occurred in patients receiving either general anesthesia or monitored anesthesia care.
Although the cause of corneal abrasion may not be obvious, securely closing the eye lids with tape after loss of consciousness (but prior to intubation) and avoiding direct contact between eyes and oxy-gen masks, drapes, lines, and pillows (particularly during monitored anesthesia care, in transport, and in nonsupine positions) can help to minimize the possibility of injury. Adequate anesthetic depth (and, in most cases, paralysis) should be maintained to prevent movement during ophthalmological sur-gery under general anesthesia. In patients scheduled for MAC, the patient must understand that move-ment under monitored care is hazardous and, thus, that only minimal sedation may be administered to ensure that he or she can cooperate.
Ischemic optic neuropathy (ION) is a devas-tating perioperative complication. ION is now the most common cause of postoperative vision loss. Postoperative vision loss is most commonly reported after cardiopulmonary bypass, radical neck dissec-tion, and spinal surgeries in the prone position. Both preoperative and intraoperative factors may be contributory. Many of the case reports implicate preexisting hypertension, diabetes, coronary artery disease, and smoking, suggesting that preoperative vascular abnormalities may play a role. Intraopera-tive deliberate hypotension and anemia have also been implicated (in spine surgery), perhaps because of their potential to reduce oxygen delivery. Finally, prolonged surgical time in positions that compro-mise venous outflow (prone, head down, compressed abdomen) have also been found to be factors in spine surgery. Symptoms are usually present immediately upon awakening from anesthesia, but have been reported up to 12 days postoperatively. Such symp-toms range from decreased visual acuity to complete blindness. Analysis of case records submitted to the ASA Postoperative Vision Loss Registry revealed that vision loss was secondary to ION in 83 of 93 cases. Instrumentation of the spine was associ-ated with ION when surgery lasted more than 6 hr and blood loss was more than 1 L. ION can occur in patients whose eyes are free of pressure secondary to the use of pin fixation, indicating that direct pressure on the eye is not required to produce ION.
Increased venous pressure in patients in the Trendelenberg position may reduce blood flow to the optic nerve.
It is difficult to formulate recommendations to prevent this complication because risk factors for ION are often unavoidable. Steps that might be taken include: (1) limiting the degree and duration of hypotension during controlled (deliberate) hypo-tension, (2) administering a transfusion to severely anemic patients who seem to be at risk of ION, and discussing with the surgeon the possibility of staged operations in high-risk patients to limit pro-longed procedures.
Of note, postoperative vision loss can be caused by other mechanisms as well, including angle closure glaucoma or embolic phenomenon to the cortex or retina. Immediate evaluation is advised.
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