Lower volume linked to higher rate of post-cataract surgery endophthalmitis

This large database review found that fewer years of surgical experience increased the risk of postoperative endophthalmitis.

The authors analyzed data from all Medicare beneficiary claims billed in 2003 and 2004 (3 million) to calculate the precise annual estimates of endophthalmitis, finding on average 1.22 cases per 1,000 surgeries. While this rate is lower than previous annual U.S. estimates, it is higher than studies conducted in Sweden. The authors write that the reason for this difference is uncertain but may be due to surgical procedures, prophylaxis practices, differences in racial or socioeconomic status, or measurement methodology.

Surgeon risk factors included fewer years of surgical experience and lower annual procedure volume. The authors believe that the procedure volume finding has not been previously reported. Other studies – one in Taiwan and one in Canada – have found this to be the case for general postoperative adverse events after cataract surgery. However, none of these studies have shed light on which factors associated with a higher procedure volume may be responsible for the reduced risk of endophthalmitis.

Patient risk factors included older age, male gender and race. The authors speculate the increased risk in black and Native American patients may be related to social disadvantage and poorer general health in these patients.

They note that surgeries performed in 2003 had a higher risk of endophthalmitis compared with surgeries performed in 2004. They write that is unlikely that such a difference is a result of changes in procedure and diagnosis coding because none of the codes utilized in this study changed during this time period, and the short duration makes it unlikely that a meaningful number of providers changed their billing practices during this time. This finding is in agreement with data from Canada and a single academic center in Florida, where more recent surgeries had lower risk. This risk reduction persisted after adjustment for available patient and surgical factors. Information on surgical technique and prophylaxis were not available in this analysis, and it is possible that these factors have changed with time in the United States. The authors are conducting further research in a nationally representative case-control study of endophthalmitis to address these questions.

Finally, they write that although endophthalmitis rates varied across states, 50 percent of states had an adjusted rate between 1.43 and 1.71 cases per 1,000 surgeries, and most states with higher or lower rates had smaller populations, which resulted in wider CIs. Nevertheless, this rate variation suggests an area for future research to elucidate whether potential interventions might reduce disparities. Differences in socioeconomic status and health status across states may well explain part of it.