Intravitreal Injections and Endophthalmitis

Stephen J. Kim, MD


Int Ophthalmol Clin. 2015;55(2):1-10. 

In This Article

Risk Factors for Endophthalmitis After IVT Injection

Despite several recent reports of endophthalmitis due to respiratory organisms, the most common source of bacteria causing endophthalmitis after IVT injection is presumed to be the patient's own conjunctiva or eyelids. The Endophthalmitis Vitrectomy Study demonstrated that bacteria cultured from the anterior chamber, the vitreous, or both of eyes with endophthalmitis were genetically identical to bacterial cultured from the patient's own respective eyelid providing compelling evidence of this association.[9] Therefore, potential mechanisms of infection include direct inoculation of ocular surface bacteria into the vitreous at the time of injection or subsequent entry through a wound track potentially mediated by vitreous incarceration. Shockley et al[10] reported that 51 colony-forming units (CFU) of Staphylococcus aureus and 98 CFU of Pseudomonas aeruginosa were required to cause endophthalmitis in aphakic rabbits when injected into the anterior chamber. This was in contrast with only 19 CFU of S. aureus and 6 CFU of P. aeruginosa required to cause endophthalmitis when injected into the vitreous. The anterior chamber therefore seems to possess greater defense mechanisms to eliminate or disable bacteria than the vitreous. This fact underscores the importance of preventing introduction of any size inoculum into the vitreous.