Background: The corneal complications of vitreo-retinal surgery are rarely the primary concern of the surgeon operating on a difficult retinal detachment. However, the surgeon should be aware of which procedures are more likely to induce corneal decompensation, because corneal abnormalities are a common cause of visual loss following an otherwise successful surgery[1]. Thus it is important to evaluate corneal endothelial cell changes after PPV. Aim of the work: To evaluate corneal endothelial cell changes in patients undergoing Pars plana vitrectomy with silicone oil (SO) injection. Subjects and Methods: This prospective comparative observational study evaluated the corneal endothelial cell characteristics of 27 SO filled vitrectomizied eyes operated in Zagazig University Hospitals, Ophthalmology department. Endothelial cell densities (ECD), coefficient of variation (CV), central corneal thickness (CCT) and percentage of hexagonal cells (hexagonality) at the corneal center were measured preoperatively, 1 week,1 month and 3 months after surgery using noncontact specular microscopy and were compared pre and post operatively. Exclusion criteria were previous vitreoretinal surgery, aphakia, any degree of anterior chamber inflammation, history of previous eye trauma, SO bubbles in the anterior chamber and increased intraocular pressure in the postoperative period. Results: Three months after pars plana vitrectomy with silicone oil injection, mean ECD was 2032.92±434.41cells/mm2in the vitrectomized eyeswhile mean hexagonality (pleomorphism) was 65.66±8.05. Three months after operation, CV (polymegathism) was 31.03±5.97 while mean CCT was 552.51±32.01μm with no corneal edema reported at the end of the study. Conclusion: Although the presence of SO in the vitreous cavity, PPV was associated with corneal endothelial cell changes in the form of EC loss and pleomorphism. Silicone oil could be a risk factor for increasing endothelial cell loss after pars plana vitrectomy. The percentage of corneal endothelial cell loss was higher in patients with SO injection than those left saline filled, but it was statistically insignificant Thus, removal of SO after reaching the desired tamponade effect is recommended.