Diabetic retinopathy (DR) is the most common cause of vision loss among people with diabetes mellitus (DM) [
1]. According to the data from a global pooled analysis, the overall prevalence was 34.6% for any DR, 6.96% for proliferative DR (PDR), and 6.81% for diabetic macular edema [
2]. More seriously, 20.1% of type 1 DM cases and 25.4% of type 2 DM cases experienced vision loss within 10 years [
3]. Vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) are known to play important roles in the pathogenesis of PDR by inducing pre-retinal neovascularization and disrupting the blood–retinal barrier [
4]. Anti-VEGF drugs, such as bevacizumab, ranibizumab, and aflibercept, were developed as new approaches to treat PDR [
5]. However, they still have some unsatisfactory aspects. In November 2013, the China Food and Drug Administration (CFDA) approved conbercept (KH902; Chengdu Kanghong Biotech Co., Ltd., Sichuan, China), a new drug comprising VEGFR fusion proteins, which can specifically bind to VEGF-A, VEGF-B, and PlGF, for treatment of wet age-related macular degeneration [
4]. In several previous studies, intravitreal conbercept (IVC) injection was proved to be an effective and safe treatment for patients with diabetic macular edema and retinopathy of prematurity [
6]. On the other hand, the anti-VEGF drugs have been proved to be beneficial to vitrectomy procedures by reducing the chances of intraoperative bleeding owing to decreased concentrations of VEGF and PlGF [
7]. Therefore, determining the concentration of VEGF and PlGF is important. Low concentrations of VEGF and PlGF would reduce the risk of intraoperative hemorrhage. In this study, we for the first time evaluated the concentrations of VEGF and PlGF in the aqueous and vitreous humor after patients received an IVC injection.