A Pharmacokinetic Study: Ranibizumab, Aflibercept and the Effect of Vitrectomy.

To study the effect of pars plana vitrectomy on the intravitreal pharmacokinetics of ranibizumab and to compare the half-life of ranibizumab and aflibercept.

This study is a prospective, pharmacokinetic study comparing ranibizumab clearance in two groups of patients; those with and without prior vitrectomy. Additionally it will compare ranibizumab clearance to aflibercept clearance as well as the effect on systemic circulating inflammatory and safety markers. Patients will already be receiving ranibizumab or aflibercept therapy - the injection is itself administered irrespective of their participation in this study and therefore this study will not alter medical management or the choice of therapy. To estimate ranibizumab and aflibercept clearance, it is important to measure serum concentrations at several intervals within the first 24 hours. Participants will ideally have venous blood sampling at the following times after their ranibizumab or aflibercept injection: * 1 hour * 2 hours * 3 hours * 4 hours * 6 hours * 24 hours * 2 days * 4 days * 1 week\* * 2 weeks * 4 weeks\*