Purpose
Endophthalmitis is a rare but serious, site threatening complication that may develop secondarily to an intravitreal injection. Antibiotic drops are often administered post injection in hopes to decrease this complication. There are however, no studies to indicate there is truth in this method and limited data available as to whether the practice may be harmful. This study was designed to investigate the effect of repeated, short term prophylactic Moxifloxacin antibiotic drops on the ocular flora post intravitreal Ranibizumab injection for Age Related Macular Degeneration (ARMD).
Methods
This was a non-blinded, randomized controlled trial. Inclusion criteria consisted of newly diagnosed choroidal neovascular membranes subsequent to ARMD in patients over the age of 60 years. Patients were randomized to either a Control(C) group who would not receive antibiotics post intravitreal injection (IVT) or Moxifloxacin(M) group who would receive topical antibiotics post IVT QID for 3 days. Swabs of the inferior fornix were taken at baseline and follow up visits 1,2, and 3. Swabs were sent for culture and sensitivity assay by Kirby-Bauer method.
Results
A total of 57 patients were enrolled in our study. Average age was 81.9 years in both Control and Moxifloxacin group (P=0.997). There were no cases of endophthalmitis. The most common isolate cultured was coagulase negative Staph epidermidis. Positive culture rate over the study was 57.1% There was a significant difference in growth rates seen only on visit 3 (C=67.9% vs M=46.7%, P<0.005). Resistant growth rates were similar at baseline (C=4.8 vs M=11.8 P=0.43). By follow up visit 1, there was a large increase in the rate of resistant cultures seen in the Moxifloxacin group (C=22.2% vs M=58.3%, P=0.04) as well as in follow up visit 2 (C=0% vs M=36.8%, P<0.005) and 3 (C=10.5% vs M=57.1%, P<0.005).
Conclusions
Results demonstrate an immediate increase in the rate of resistance after only three days of prophylactic Moxifloxicin therapy compared to Control group. This was 40% higher than baseline. Given the low rates of endophthalmitis, lack of research showing benefit of post injection antibiotics, and findings suggesting poorer outcomes in endophthalmitis with resistant strains of Staph epidermidis, this research provides evidence that post injection antibiotics may be harmful in repeated IVT injections.
Keywords: 422 antibiotics/antifungals/antiparasitics •
561 injection •
513 endophthalmitis