Vascular endothelial growth factor (VEGF) is a key player in the development of macular edema (ME) in patients with retinal vein occlusion (RVO). However various other factors influence the development of ME. In a rat model, we observed a fast and transient upregulation of the expression of VEGF, which is dominant for the acute stage of ME. In chronic ME an upregulation of inflammatory factors is presented. The intravitreal drugs reduce the ME, but the mechanism of action differs between steroids and anti-VEGF. Anti-VEGF drugs inhibit the VEGF whereas steroids presents an unspecific anti-inflammatory effect inhibiting the expression of broad spectrum of molecules. The determination of the patients who benefit from each particular treatment would improve the functional results and reduce the possible side effects. In a retrospective study in which we investigated whether BRVO patients benefit more from injection of bevacizumab or triamcinolone if treated according to the duration of ME we found out a better visual gain under treatment with bevacizumab in the first 4 months. In patients with treatment later than 4 months since onset of BRVO no significant differences between bevacizumab and triamcinolone were observed.