Good News: But Why Is the Incidence of Postoperative Ischemic Optic Neuropathy Falling?

The number of patients undergoing spinal fusion surgery in the United States is the highest in the world. Developing perioperative visual loss as a result of ischemic optic neuropathy (ION) is a rare complication. Patients undergoing either cardiac or spinal fusion surgery are at risk of developing ION; hence, it becomes relevant to uncover the risk factors and preventive measures for such rare but serious complications. The purpose of this study was to determine trends in ION occurrence in spinal fusion and risks in a nationwide administrative hospital database. Between 1998 and 2012, procedure codes for posterior thoracic, lumbar, or sacral spine fusion and diagnostic codes for ION were identified in the Nationwide Inpatient Sample. Ischemic optic neuropathy was studied over 3-year periods between 1998 and 2000, 2001 and 2003, 2004 and 2006, 2007 and 2009, and 2010 and 2012. Trend weights in a statistical survey procedure were used to arrive at national estimates. The assessed trends and risk factor data were analyzed using univariate and Poisson logistic regression. It was estimated that between 1998 and 2012 there were 2,511,073 thoracic, lumbar, and sacral spinal fusion surgeries nationally. Ischemic optic neuropathy was estimated to develop in 257 patients (1.02/10,000). The incidence rate ratio (IRR) for ION significantly decreased between 1998 and 2012 (IRR, 0.72 per 3 years; 95% confidence interval [CI], 0.58–0.88; P = 0.002). There was no significant change in the incidence of retinal artery occlusion. Factors significantly associated with ION were age (IRR, 1.24 per 10 years of age; 95% CI, 1.05–1.45; P = 0.009), transfusion (IRR, 2.72; 95% CI, 1.38–5.37; P = 0.004), and obesity (IRR, 2.49; 95% CI, 1.09–5.66; P = 0.030). Female sex was protective (IRR, 0.30; 95% CI, 0.16–0.56; P = 0.0002). It was found that the risk of ION increased significantly with age, male sex, transfusion, and obesity. This study demonstrated a significant decrease in ION following spinal fusion. The incidence has been reduced by a third (2.7-fold) between 2010–2012 and 1998–2000. There was not any change in the occurrence of retinal artery occlusion in the same periods, implying that the processes resulting in these 2 complications are not the same. Clear conclusions could not be drawn by the authors about the reasons behind the decrease in ION. It is possible they are a result of perioperative surgical and/ or anesthetic practice changes following national practice advisories and recommendations. Further studies are recommended.