6.5.3.1 Efficacy Determination
The clinical efficacy of laser hair removal systems is determined by the amount of hair remaining after completing a course of laser treatments. For facial hair, treatment regimens generally range from four to eight treatments given at a 3-6-week interval. Even though dramatic and stable reduction can be achieved, complete hair eradication by laser is rarely possible [25-28]. The hair remaining after treatment and/or any new hair growth tends to be softer, thinner, and less pigmented, which adds to the aesthetic benefits, and thereby results in a high level of subject satisfaction [26,27,29]. To obtain objective data, especially for comparative purposes, the amount of hair is determined by using a manual hair-count method. As hair density is rarely uniform on the whole treatment area, the counts must be performed on the same site before and after treatments to get a valid difference. Natural skin land marks or implanted micro-dot tattoos can be used to get back to the same site during the course of treatment. In conjunction with the hair count, the rate of hair growth after treatment can be used to access efficacy [30]. These objective methods provide a conservative measure of effectiveness, as laser treatment often results in altering the character of the regrowing hair, which is not captured in the hair count or the growth rate difference, but rather adds to the benefits perceived by the subjects. Some researchers count only the terminal hair whose diameter and color is similar to the hair present before the treatment. This is considered a good representation of efficacy, since the sparser, finer, and the lightly pigmented hair remaining generally do not bother the subjects. In addition to these objective measures, the patient satisfaction of the outcome can be used to gauge the treatment benefits [26,27,29]. Though patient satisfaction is an important measure, it is also highly subjective and dependent on the patient’s expectations of the results and the actual results achieved.