The risk of blindness caused by spinal fusion has dropped almost 3-fold since the late 1990s, according to a study published in the journal Anesthesiology.
“While there are significant complications that can result from spinal-fusion surgery, it seems that blindness, a catastrophic and devastating complication, is one that has become far rarer in recent years,” said Steven Roth, MD, University of Illinois at Chicago College of Medicine, Chicago, Illinois.
Nearly 480,000 spinal fusions are performed in the United States each year, with an incidence of blindness placed between 1 in 1,000 and 1 in 10,000. Because most studies on the operation have been very small, it has been difficult to devise guidelines for patients and surgeons in decision-making.
“We wanted to know if rates of blindness as a result of these surgeries were stable, increasing or decreasing over time,” he said.
Using data from the Nationwide Inpatient Sample, the researchers estimated the number of spinal fusions and cases of blindness caused by the surgery between 1998 and 2012. They looked for procedure codes for spinal fusion surgery and diagnosis codes for ischaemic optic neuropathy occurring during or directly after the surgery.
They estimated that 2,511,073 spinal fusions were performed, resulting in 257 instances of ischaemic optic neuropathy, or 1.02 per 10,000 surgeries. But over that time-span, the risk decreased by 60%.
The researchers noted that significantly increased risk for ischaemic optic neuropathy during spinal fusion surgery came with age over 50, male gender, receiving a blood transfusion during the procedure, and obesity.
Roth attributes the decline in risk to the increasing use of minimally invasive surgical techniques.
“The characteristics of the patients undergoing spine fusion haven’t changed all that much over the years, although the population has aged,” said Dr. Roth, “So the variables that must be contributing to the decline in blindness caused by spine fusion surgery are most likely the result of changes made in how the surgery is performed.”
Dr. Roth believes that changes in anaesthesia practice may also be driving the decrease in risk of blindness. Many anaesthesiologists now set a stricter limit for how low they will allow blood pressure to drop during surgery, he said, which may help reduce the risk for ischemic optic neuropathy.