If you suffer from problems related to varicose veins and spider veins you are not alone! Venous insufficiency, also known as venous reflux disease, is the most common cause of varicose veins and affects nearly 30 million adults in the United States. Veins serve an important function bringing blood back to the heart. We have two sets of veins in our legs, deep veins and superficial veins. These veins have one-way valves that normally direct blood flow in one direction, toward the heart. When these valves fail blood can flow the wrong way and pool, increasing the pressure in the veins.