Speaking on the second day of the 2010 ESCRS Congress in Paris, Dr Jan C. van Meurs of the Rotterdam Eye Hospital and Erasmus University, the Netherlands said: In tertiary referral centres, post-injection endophthalmitis has insidiously become one of the most frequent causes of endophthalmitis. The risk of post-injection endophthalmitis per injection approaches that of cataract surgery, but per patient greatly exceeds the risk of infection after cataract surgery. This phenomenon highlights that the administration of intravitreal injections, in terms of infection prevention, should be approached as real surgery.

Suspected bacterial endophthalmitis is a rare but severe complication of intraocular surgery and a more common one after trauma. It has been best studied after cataract surgery, being the largest and most uniform study population. Suspected bacterial endophthalmitis following an intravitreal injection of gas (SF

), triamcinolon or anti-VGF, appeared to be a relatively rare occasion. However, the number given of the last type of injection has increased exponentially over the last 5 years, with the result that post-injection endophtalmitis may rank among the top two endophthalmitis causes in tertiary  referral centers. In fact, the risk per injection is in the range of the risk after cataract surgery, but the risk per treatment series, therefore per patient, is substantially greater. (W. Mieler, MD, oral presentations 2009, 2010).

Post-injection bacterial endophthalmitis is most likely caused by the introduction of commensal bacteria into the eye, punched into the vitreous by the injection needle. Reflux and an open tract between vitreous cavity and the conjunctival commensal flora, thought to be instrumental in post-transconjunctival vitrectomy endophthalmitis, is a less likely contributor.Damage to the eye is caused by exo or endotoxins of the multiplying bacteria or by bystander damage caused by the inflammatory response mounted by the host. 

The bacteria involved are essentially the same pahogens as in postcataract endophthalmitis (i.e., the commensal flora of the eye), with the most common pathogens coagulase negative staphylococci, staph. aureus and streptococccus species. 

The injected protein anti-VEGF antibodies may incite a immunological inflammatory reaction in the vitreous, possibly more frequently after repeated injections.

The clinical signs of postinjection bacterial or sterile endophthalmitis are:visual loss, sometimes pain, hypopyon, posterior synnechiae, and vitritis.

As in postcataract endophthalmitis, when facing a patient with suspected postinjection endophalmitis, infection or sterile inflammation, the clinician's approach is an empirical one. Clinical signs will seldom establish a firm diagnosis of a sterile endophthalmitis and there is no time to wait for laboratory results. Therefore, we would recommend a modified EVS style approach: early vitreous biopsy by a vitreous cutter, followed by the intravitreal injection of Vancomycin 1 mg and Ceftazidin 1 mg. In our Institution we would inject a lower dose of antibiotics, but twice, and would perform a vitreous biopsy only, in all patients, including those presenting with light perception only. Treatment results are unfortunaly not better than in post cataract endophthalmitis treatment, i.e. two thirds do well, one third do badly.

Dr Jan van Meurs from the Rotterdam Eye Hospital and Erasmus University in The Netherlands presents his view.