Intraocular Pressure Changes During Cardiopulmonary Bypass Pump and Off-Pump Cardiac Surgeries

The complication of anterior ischemic optic neuropathy (AION) occurs in up to 1.3% of patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). 1 AION’s effects can be devastating—some cases cause unilateral or bilateral blindness. And, unfortunately, no effective treatment for such vision loss is available. The pathogenesis of AION, both in general and during CBP surgery, is most likely multifactoral, but has not been established with certainty. A crowded optic disc, marked hyperopia, diabetes mellitus, hypertension, and severe anemia are known predisposing factors for the development of AION. Ischemic optic neuropathy also has been reported after noncardiac surgeries, including aortobifemoral surgery, spine surgery, and abdominal exploration. 2–4 Severe anemia and hypotension were thought to be the most significant risk factors for postoperative vision loss in these reports. With regard to CPB surgery, intraocular pressure (IOP) increase has been proposed as a factor in the pathogenesis of AION. Imbalance produced by lowering optic nerve perfusion pressure or increasing IOP during CPB might lead to optic nerve ischemia as a result of compromised blood flow. 5–7 But data on this issue is conflicting: Several studies have reported an increase in IOP during CPB surgeries, 5–7 while others have reported a decrease 8 or no change. 9 Hypothermia, hypotension, hemodilution with resulting anemia, microembolization, and CPB pump–related platelet dysfunction also may contribute to the development of AION