Although there are many laser systems, all laser cosmetic applications use selective photothermolysis or light that targets a single element in the skin as a means to achieve the desired result. There are ablative laser systems that abrade, as well non-ablative that work without abrading the surface of the skin. These systems are used for Fotofacial, Hair Reduction and Photo Dynamic Therapy.
There are 5 parameters that govern all of these systems. Since these parameters are interdependent, the correct combination is critical to the outcome of a particular treatment
- Pulse width
- Power / Fluence
- Spot size
- Epidermal cooling method
Longer wavelength penetrate deeper into the skin. Melanin, whether in the epidermis or the hair follicle and Hemoglobin, preferentially absorbs light in the infrared spectrum of light and peaks around both 600nm and 1100nm. The Pulse Width governs the length of time in milliseconds over which the laser energy is emitted. This energy has to be delivered quickly and over a short period of time so that it does not dissipate to, and damage, the surrounding tissue. Power/Fluence is the amount of energy delivered to the tissue and is measured in Joules /cm 2. Spot Size is the area over which the energy is applied. As compared to the older lasers, modern ones have larger spot sizes so that faster treatment is possible. Larger spot sizes allow deeper penetration of the energy. Cooling- enhances epidermal protection. There are a number of methods used including a cooling mechanism right on the applicator head to separate system that blows cold air as well as cryogen spray that is fired over the treatment area.