Preop antibiotics may not be needed to prevent endophthalmitis after intravitreal steroid use

A low rate of endophthalmitis can be achieved after intravitreal triamcinolone injection without the use of antibiotic prophylaxis on the pretreatment days, said Abdhish R. Bhavsar, MD, at the annual meeting of the American Society of Retina Specialists.

His statement was based on an analysis of data from two randomized clinical trials comparing laser photocoagulation with intravitreal triamcinolone acetonide injections. Treatment in those studies, as of Dec. 21, 2006, comprised 2,009 total injections delivered to 839 eyes, and a single case of postinjection endophthalmitis was reported (0.05%; 95% confidence interval, 0.001% to 0.277%).

"In published studies, the risk of endophthalmitis after intravitreal injections has been reported to range from 0.1% to 1.6%, although the risk with triamcinolone may be higher, up to 1.4% including sterile cases, possibly because the steroid or its vehicle interferes with the immune system response to infectious organisms. However, significant controversy exists with respect to strategies for endophthalmitis risk reduction for these procedures," said Dr. Bhavsar, director of clinical research at the Retina Center, PA, Minneapolis.

"Topical antibiotics are often used for several days prior to injection, even though there is no Level I evidence of their efficacy. Our data suggest a more minimalist approach may be reasonable," he said. "However, the low rate of endophthalmitis found in these trials must be interpreted in the context of the standardized injection methods that included the use of triamcinolone in a prefilled syringe, povidone-iodine preparation, and a sterile eyelid speculum."

Two studies
The two studies included in the analysis were the Diabetic Retinopathy Clinical Research Network (DRCRnet) trial comparing intravitreal triamcinolone and laser photocoagulation for diabetic macular edema (DME) and the Standard Care Versus Corticosteroid for Retinal Vein Occlusion (SCORE) trial. In both studies, triamcinolone 1 mg or 4 mg injections were administered through the pars plana using preservative-free formulations specially prepared and packaged in prefilled syringes by Allergan. Both studies also used an identical preparation protocol that involved instillation of three doses of topical gatifloxacin 0.3% (Zymar, Allergan) over 15 or more minutes prior to injection and topical proparacaine for anesthesia dosed immediately before the injection.

Additional anesthesia methods were allowed at the investigator's discretion and included use of a cotton-tipped applicator soaked in topical anesthetic, topical lidocaine gel, or subconjunctival anesthetic.

The surgical site also was prepared for injection with application of povidone-iodine, using either a cotton-tipped applicator soaked in a 5% solution or commercially available, 10% povidone-iodine swabs (Swabstick, Triad Disposables). In some eyes, that step was preceded by application of two or three drops of 5% povidone-iodine in the lower fornix or an ocular surface flush with a 5% povidone-iodine forced stream from an angiocatheter. Prior to injection, a sterile eyelid speculum was placed. Post-treatment, patients used gatifloxacin four times daily for 3 days.

Data analyzed
Data were analyzed as of Dec. 31, 2006, for the DRCRnet intravitreal triamcinolone DME trial. In that study, 1,378 intravitreal injections were administered in 538 eyes by 162 ophthalmologists. In SCORE, 631 injections were administered in 301 eyes by 159 ophthalmologists.

The isolate in the one case of endophthalmitis that developed after the 2,009 total injections was coagulase-negative Staphylococcus.

"Of note, there were no cases of sterile endophthalmitis in the more than 2,000 intravitreal injections of triamcinolone," Dr. Bhavsar said.

Because a topical antibiotic was administered routinely for 3 days post-treatment in the two studies, he added, it cannot be determined from the analysis whether postinjection antibiotic prophylaxis is necessary.

"However, the DRCRnet is actively altering the preparation protocol and antibiotic regimen in its clinical trials to help achieve a more minimalist injection approach and potentially to provide evidence to support the elimination of antibiotic prophylaxis pre- and post-injection.

"The current injection protocols for the DME and proliferative diabetic retinopathy trials evaluating ranibizumab or triamcinolone with laser photocoagulation [LRT trials] do not require antibiotics pre- or post-injection of ranibizumab. We look forward to reporting outcomes from those studies in the future," he said.

The data Dr. Bhavsar presented recently were published (Am J Ophthalmol 2007;144:454-456). He has collected data on the risk of endophthalmitis in 1,000 intravitreal injections administered without pre- or post-injection antibiotics in his own practice and plans to present the data later this year.