Researchers have determined that an increased incidence rate of post-cataract surgery anterior ischemic optic neuropathy (AION) occurs in the first year following cataract surgery but that risk doesn’t hold true for the first two months.

The study was conducted over 27 years as the team assessed patients in Olmsted County, Minnesota. During the study period, 102 residents developed AION. The median age was 65 years old and 43.1% were female. In the group, 20 (19.6%) patients had previous cataract surgery, of which two and nine developed AION within two months and one year of surgery, respectively.

The researchers found that the annual incidence rate of post-cataract surgery AION within two months of surgery (8.6 per 100,000) was not significantly greater than the annual incidence rate of spontaneous AION (6.9 per 100,000). However, when they looked at the rates a year after surgery, the data tells a different story. The annual incidence rate of post-op AION within one year of surgery (38.9 per 100,000) was significantly higher than the incidence rate of spontaneous AION.

The study authors admitted that the reason for the incidence discrepancy they observed remains unclear.