Effect of prophylactic antibiotics and incision type on the incidence of endophthalmitis after cataract surgery

Background: There is controversy as to the efficacy of various measures in the prophylaxis of endophthalmitis after cataract surgery. In addition, it has been suggested that clear-corneal incisions may convey an increased risk of postoperative infection. We performed a retrospective review to assess the effect of prophylactic antibiotics and incision type on the incidence of endophthalmitis after cataract surgery. Methods: A retrospective chart review and surgeon survey were used to collect data for the 13 886 consecutive cataract operations performed between Sept. 1, 1994, and Jan. 31, 1998 by nine surgeons at a hospital-based surgical unit in Saskatoon. All cataract extractions were by phacoemulsification. All cases of endophthalmitis arising from the unit are managed at the hospital except in extenuating circumstances. We assessed the effect of preoperative administration of antibiotic drops, subconjunctival antibiotic injections at the conclusion of surgery and clear-corneal versus scleral tunnel incisions on the incidence of endophthalmitis by means of univariate and multivariate Poisson regression analysis. Results: The incidence of postoperative endophthalmitis was significantly lower with subconjunctival antibiotic injections than without such injections (0.011% vs. 0.179%) (p = 0.009, odds ratio 16.23 [95% confidence interval 1.92 to 137.14]). The difference in the incidence of endophthalmitis with preoperative use of antibiotic drops (0.066%) and with no antibiotic drops preoperatively (0.115%) was not significant. Similarly, the difference in the incidence of endophthalmitis with clear-corneal (0.129%) and scleral tunnel (0.050%) incisions was not significant. Interpretation: Our results suggest that prophylactic subconjunctival antibiotic injections at the conclusion of cataract surgery decrease the incidence of postoperative endophthalmitis.