Stratifying the risk factors for endophthalmitis after cataract surgery

We read with interest the article by Lundström et al.¹ identifying the relative risks for developing postoperative endophthalmitis in the presence of several known risk factors. In their paper, the authors reported that patients who did not receive prophylactic intracameral antibiotics had a higher risk for endophthalmitis. The rate of endophthalmitis among the patients who did not receive intracameral antibiotics was 0.43%, with 0.16% of patients having a visual acuity worse than 20/60.

We fully agree with the authors that administering prophylactic intracameral antibiotics has an important role to play in prevention and in the reduction of infection rates. The evidence of this is seen in many studies of the use of intracameral antibiotics. The ESCRS Endophthalmitis Study² reported a 5-fold reduction in the rates of postoperative endophthalmitis with the use of intracameral cefuroxime. In a study in Singapore³ during the period without the use of intracameral antibiotics, the rate of endophthalmitis was 0.064%. This decreased to 0.01% when intracameral cefazolin was administered routinely at the end of surgery. Garat et al.⁴ similarly described a decrease from 0.63% to 0.055%, while Romero et al.⁵ showed a decrease in incidence from 0.422% to 0.047% after the introduction of intracameral cefazolin.

It was interesting to note that in the study by Lundström et al.,¹ patients aged 85 years or older had a higher frequency of staphylococci (37.5%) and gram-negative organisms (18%). Although gram-negative organisms are a relatively uncommon cause of postoperative endophthalmitis, the rate of gram-negative cultures is higher is some Asian populations.³ In a study in Singapore,³ gram-negative bacteria was seen in approximatelty 25% of culture-positive patients. In addition, the mean age of patients with gram-negative cultures was 76.7 years compared with 66.7 years for those with gram-positive cultures, which is similar to the finding reported by Lundström et al. This could be due to differences in eyelid or conjunctiva flora or variances in drug efficacy between ethnic and age groups.

Lundström et al. also identified the populations at risk for endophthalmitis. We agree that performing cataract surgery earlier will “prevent the development of small pupils, dense cataracts, and loose zonular fibers,” which would reduce the risk for surgical complications, including posterior capsule rupture. In addition, younger patients, having less systemic comorbidities, are less likely to have anesthetic complications as well.

Because patients with perioperative capsule problems have a higher endophthalmitis incidence with gram-positive organisms, of which 15 of 18 cases with Enterococcus were resistant to cefuroxime, it might be worth considering using vancomycin or a fluoroquinolone for these patients and also monitoring them more closely postoperatively.

In summary, we strongly believe that prophylactic intracameral antibiotics play an important role in reducing the rate of endophthalmitis after cataract surgery and congratulate the authors for investigating and identifying the risk factors in developing endophthalmitis.