To evaluate the effect of adding imipenem to the irrigation solution during phacoemulsification on the rate of postoperative endophthalmitis.

In this retrospective study, the rate of post cataract surgery endophthalmitis in 2 university-based hospitals by 18 expert surgeons for all surgeries performed between April 2014 and March 2017 were evaluated. The rate and characteristics of acute postoperative endophthalmitis were compared between patients receiving imipenem (50 µg/ mL) in the irrigating bottle and those receiving subconjunctival cefazolin.

The total number of all cataract surgeries were 24284 phacoemulsifications, 9244 had imipenem in the irrigating bottle, and 15040 received subconjunctival cefazolin. The mean age (±SD) of the participants was 64 (±12) years, and 49.2% were male. Vitreous loss occurred in 353 cases (1.45%). The total rate of acute postoperative endophthalmitis was 0.049% (12 cases in 24284 surgeries), all of which were occurred in cases who did not receive imipenem in the irrigating bottle. The calculated risk difference was 0.080% (95% CI: 0.024% to 0.139%; P = 0.0156). Of 12 cases of presumed endophthalmitis, 6 (50%) were culture positive (all bacterial). No complications (such as uveitis, corneal decompensation, retinal infarction, etc.) attributed to the use of imipenem were reported.

Compared to the subconjunctival cefazolin injection, imipenem added to the irrigating bottle could significantly reduce the rate of post- cataract surgery endophthalmitis for at least 2 cases in 10000 operations.