Endophthalmitis Risk Low After Intravitreal Injection

Troy Brown, RN

July 21, 2016

Only 30 cases of endophthalmitis occurred after 90,339 intravitreal injections, and prophylactic antibiotics did not decrease the rate of infections, a recent study suggests.

Most physicians no longer use prophylactic antibiotics in these patients, the authors say. "Such practice patterns have been supported by recent large clinical trials including those performed by the Diabetic Retinopathy Clinical Research Network. Recent guidelines by an expert panel also agreed insufficient evidence exists to endorse the use of antibiotics to decrease the rate of endophthalmitis," the researchers write.

Alexa L. Li, BS, from Retina Consultants of Houston, Texas, and colleagues report their findings in an article published in the July issue of Retina.

Intravitreal injections are a common treatment for retinal pathologies including neovascular age-related macular degeneration, retinal vein occlusion, and diabetic macular edema. Patients usually tolerate these procedures well, but can develop a rare but potentially disastrous infection known as endophthalmitis. In the past, many physicians have prescribed topical antibiotics in the peri-intravitreal injection period, but this practice has fallen out of favor; 90.5% of 2015 respondents to the Preferences and Trends survey reported that they do not use antibiotics with these injections.

In the current study, Li and colleagues retrospectively identified patients who underwent intravitreal injections at all offices of a large retina-only practice from January 1, 2011, to December 31, 2014. Clinicians used prophylactic antibiotics from January 1, 2011, through December 2011 and did not use them from January 1, 2013, to December 31, 2014. Clinicians phased out use of the antibiotics during 2012, and the researchers considered this year to be the transition period.

The study's primary outcome measures were incidence of endophthalmitis, microbiology results, treatment strategies, and visual outcomes.

Medications used for the injections included ranibizumab, bevacizumab, aflibercept, dexamethasone implant, preservative-free triamcinolone, ocriplasmin, and pegaptanib.

A total of 30 cases of clinically suspected endophthalmitis occurred postinjection and were treated, for a rate of 0.033% (95% confidence interval [CI], 0.021% - 0.045%), or about one case for every 3011 intravitreal injections. Per year, the number of identified and treated endophthalmitis cases was six in 2011, 13 in 2012, seven in 2013, and four in 2014.

"Owing to the nature of performing intravitreal injections, there is a risk of contamination with nasopharyngeal flora including streptococcal organisms. Masks were not a part of the standard protocol in the current series," the authors write. "Most retina specialists recommend either wearing a surgical mask or minimizing talking while preparing and administering intravitreal injections."

Endophthalmitis occurred in 13 eyes (43%) that received prophylactic peri-intravitreal injection topical antibiotics compared with 17 (57%) eyes that did not receive antibiotics. Endophthalmitis rates did not differ significantly during the period in which patients received prophylactic antibiotics (6/16,984, or 0.035%; 95% CI, 0.007% - 0.064%) compared with the period in which patients did not receive prophylactic antibiotics (11/53,345, or 0.021%; 95% CI, 0.008% - 0.033%; P = .261).

Of the patients who developed endophthalmitis, 12 (40%) had diabetes mellitus.

Among patients who developed endophthalmitis, the intravitreal injections were given for treatment of neovascular age-related macular degeneration (n = 19; 63%), diabetic macular edema (n = 7; 23%), retinal vein occlusion (n = 2; 7%), cystoid macular edema secondary to uveitis (n = 1; 3%), and retinal neovascularization (n = 1; 3%).

Patients presented with endophthalmitis a mean of 5 days (range, 1 - 14 days) after injection; 11 (37%) presented within the first 3 days, and two (7%) presented more than 7 days after injection.

Sixteen (53%) of the 30 patients with endophthalmitis had positive microbial cultures and 14 (47%) had negative cultures.

The two most frequently isolated organisms were coagulase-negative staphylococci (10/30; 33%) and Streptococcus mitis (2/30; 7%). Haemophilus influenzae (1/30; 3%), Kocuria kristinae (1/30; 3%), Micrococcus species (1/30; 3%), and Moraxella atlantae (1/30; 3%) were also isolated.

"Prophylactic peri-intravitreal injection topical ophthalmic antibiotic use did not seem to affect the rate of endophthalmitis," the authors conclude.

The authors have disclosed no relevant financial relationships.

Retina. 2016;36:1349-1356. Abstract

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