RESEARCH ARTICLE Open Access

Retinal vein occlusion (RVO) is a common retinal vascu-lar disorder in which different complications, including macular edema, may develop with a consequent loss of central vision [1]. According to the localization of ven-ous occlusion, central retinal vein occlusion (CRVO) and branch retinal vein occlusions (BRVO) are the most fre-quently occurring and clinically relevant types [2]. Both could result in macular edema, a condition that is char-acterized by the collection of fluid within the retina, resulting from the breakdown of the blood-retinal bar-rier and leakage of fluid from the vasculature [3]. It has been proven that vascular endothelial growth factor (VEGF) plays a crucial role in this pathological process [3]. VEGF expression is up-regulated by hypoxia and a number of other stimuli, and was noted to be elevated in the ocular fluids of patients with CRVO [4]. Moreover, intravitreal VEGF levels were observed to correlate with the severity of clinical findings [5]. Therefore, several anti-VEGF agents, including ranibizumab, bevacizumab, and pegaptanib, have been widely used for treating macular edema [6-9]. * Correspondence