Strategies of Intravitreal Injections with Anti-VEGF: "Pro re Nata versus Treat and Extend"

The goal of this report is to provide a review on different strategies for the use of pro re nata (PRN) and treat and extend (T&E) regimens with intravitreal anti-VEGF agents (bevacizumab, ranibizumab or aflibercept) in patients with retinal diseases such as neovascular AMD, diabetic macular oedema and macular oedema due to retinal vein occlusion. The main focus is to present the effectiveness and visual outcomes of both PRN and T&E regimens in the main pivotal trials and studies based on currently available evidence. We also discuss the advantages and disadvantages of both regimens, as well as monitoring and treatment of the disease, including treatment intervals and injection frequency. Currently there is increasing interest in establishing a regimen which offers the best visual outcome with lower injection frequency, and with reduced treatment burden by individualising treatment intervals and minimising the number of clinic visits and costs. Studies have shown that the PRN regimens in a clinical setting are insufficient in assuring the best visual outcome. The PRN regime requires frequent clinic visits to monitor disease status and intravitreal treatment if needed in a reactive approach. Individualised T&E regimens can improve visual outcome and require fewer injections than those administered in a monthly regimen and fewer monitoring visits than those in a PRN regimen.