​The normal function of leg veins - both the deep veins in the leg and the superficial veins - is to carry blood back to the heart. During walking, for instance, the calf muscle acts as a pump, contracting veins and forcing blood back to the heart. To prevent blood from flowing in the wrong direction, veins have numerous valves. If the valves fail, blood flows back into superficial veins and back down the leg. This results in veins enlarging and becoming varicosed. Varicose and spider veins are the most obvious and visual symptoms of vein disease. If left untreated, varicose veins can sometimes progress to become Chronic Venous Insufficiency with symptoms that may worsen over time. Fortunately, by diagnosing and treating varicose veins you may halt the progression of the disease.