MODEL RELEASED. Varicose vein surgery. Close-up of a surgical tool being used in an operation to remove varicose veins from a patient's legs. The surgeon is about to use a scalpel to make an incision in the patient's skin, using the guide markings placed there before the operation. Varicose veins form due to defective valves in veins, usually those of the legs. As blood is circulated around the legs, these valves prevent it from sinking to the feet. As the valves stop working, blood pools downwards, distending the veins. Surgical removal is carried out in severe cases, allowing the blood to flow through other veins instead. Photographed in the UK.