Differential diagnosis of endophthalmitis after intravitreal drug injection for age related macular degeneration: sterile vs. infectious

The recent release of brolucizumab and the development of new antiangiogenic molecules as abicipar pegol has increased the interest towards inflammatory complications after intravitreal drug injection. Those drugs are associated to a higher rate of inflammatory adverse events compared to classic drugs. In this context it is essential to differentiate between sterile and infectious cases for a fast and effective treatment. The clinical similarities between infectious and sterile cases, the high rate of culture negative patients and the heterogeneity in the terminology used are obstacles for a correct diagnosis and report of these complications. Sterile cases appear early after the injection, before 48 h; or 20 days after in brolucizumab-related vasculitis cases. Infectious cases show up around the third day after injection and up to a week after it. A severe visual impairment, severe pain, severe hyperemia, hypopyon and a more severe intraocular inflammatory process are signs of a likely infectious origin. If the cause of the inflammation is uncertain we must follow up the patient closely or "tap and inject" antimicrobial agents in order to prevent the eventual complications of an infectious endophthalmitis. On the other hand, sterile endophthalmitis might be observed in mild cases or treated with steroids according to the severity of the inflammation.