A surgical instrument and method are disclosed for enhancing the overall performance of arterial occluders, by allowing the repetitive obstruction of blood flow to a targeted organ or tissue, while reducing the potential for side effects such as gangrene or infarction and for post-implantation movement of the occluder during ischemia. An annular peripheral optical zone that is substantially outside the diameter of the pupil is formed around the central optical zone with greater refractive power than that of the central zone so that oblique rays entering the eye through the peripheral optical zone will be brought to focus at a focal plane that is substantially on or anterior to the peripheral region of the retina. The platform is connected by a flexible metallic cable to an electrically operated winch.