Some vessels are sclero-resistant and do not respond to injections. Because the procedure is non-invasive many people who shy away from injections may now seek treatment. Patients should be examined by a physician prior to treatment. The older the patient, the easier it is to clear leg veins, especially when the patients are older than 65. This is because the epidermis is thinner and forms less of a barrier to the treatment.
Skin color is another significant factor.
Lesions on lighter skinned people generally clear more quickly and with a lower chance of hyperpigmentation.