Purpose: The vitreous concentration of Hypoxia-inducible Factor-1α (HIF-1α) and Intercellular Adhesive Molecule-1 (ICAM-1) were related to the permeability of retinal vessels and the grades of macular edema in proliferative diabetic retinopathy (PDR). Prior studi es have showed that pan-retinal photocoagulation (PRP) is beneficial in treating PDR. The aim of this study is to determine how pre-treatment with PRP before vitrectomy affect the vitreous level of HIF–1 and ICAM-1 in patients with PDR. Materials and Methods: A randomized clinical trial study was conducted to 22 eyes in Cipto Mangunkusumo National General Hospital, Indonesia. At the beginning of PRP, just before vitrectomy, and at 2, 4, and 12 weeks after vitrectomy, central macular thickness (CMT) was measured using optical coherence tomography (OCT). Undiluted vitreous humour was extracted during vitrectomy to obtain HIF-1 α and ICAM-1 concentration. Results: In the control and the photocoagulation group, the average level of HIF-1α (ng/mL) were 0.152±0.015 and 0.164±0.033 respectively. The average level of ICAM-1 (ng/mL) in control group and pre-treated group were 17,840±14,140 and 27,027±10,452 respectively. No statistically significant difference was seen in the level of HIF-1α and ICAM-1 between each group. The correlation between vitreous ICAM- 1 and HbA1c was statistically signi ficant (r=0.463, p=0.03). No signi ficant differences for CMT at pre-vitrectomy, or 2 and 4 weeks after vitrectomy. Statistically significant difference was observed at 12 weeks after follow-up (p=0.049). The correlation between vitreous level of HIF-Iα and CMT in the control and laser group are r = 0.447 and r = 0.32, respectively. Conclusion: Laser photocoagulation 1-2 weeks prior to vitrectomy did not lower vitreous concentration of HIF-1α and ICAM-1.