There are two factors predisposing the robotic prostatectomy patient to an increase in IOP: step head-down (Trendelenburg) position and abdominal carbon dioxide (CO2) insufflation. The Trendelenburg position will increase central venous pressure within the thorax, which may reduce the drainage of blood flow from the head, thus increasing IOP. The CO2 insufflation may increase IOP via two mechanisms. First, by increasing intra-abdominal pressure there is a further increase in intrathoracic pressure. Secondly, insufflation the CO2 may increase the carbon dioxide content of the blood, to which the brain reacts by vasodilating and increasing blood volume. Thus while flow into the eye is increased, flow out of the eye is decreased leading to an increase in pressure inside the eye which eventually may reduce the inflow enough to cause retinal or optic nerve ischemia.