Physicians are often warned in training to use antibiotics sparingly for fear of increasing bacterial resistance. But here’s another reason to drop that particular drop prior to intravitreal injections: they don’t work—at least, not for this specific set of patients. In fact, according to research published in Eye, not only does antibiotic prophylaxis following intraviteral injection not reduce the rate of endophthalmitis—a condition so severe patients may lose their whole eye because of it—the medication may potentially be associated with an increased risk of infection.

In the retrospective study of records up to June 2016, the Italian research team identified one randomized and 12 nonrandomized studies that reported 74 cases of endophthalmitis in 147,203 intraviteral injections using antibiotic prophylaxis and compared them with 55 cases in 211,418 intravitreal injections with no prophylaxis.
The team then used a meta-analysis to compute the odds ratio of endophthalmitis with antibiotic prophylaxis compared with no prophylaxis and conducted subgroup analyses to compare the efficacy of different regimens and classes of antibiotics on endophthalmitis rates. The overall odds ratio of endophthalmitis for antibiotic prophylaxis vs. no prophylaxis was 1.33.

The researchers note that no difference in endophthalmitis rates were associated with any other factor, including type of antibiotic, intravitreal injected or antibiotic prophylaxis regimen.