- have metal in your body that would make having an MRI scan unsafe such as: cardiac pacemaker, insulin infusion pump, implanted drug infusion device, cochlear or ear implant, transdermal medication patch (nitroglycerine), any metallic implants or objects, body piercing that cannot be removed, bone or joint pin, screw, nail, plate, wire sutures or surgical staples, shunts, cerebral aneurysms clips, shrapnel or other metal embedded (such as from war wounds or accidents or previous work in metal fields or machines that may have left any metallic fragments in or near your eyes). If you have a question about any metal objects being present in your body, you should ask the study doctor.