The invention of the laser has led to many advancements in the electronic and medical device industries. In the beauty arena, new and improved lasers are entering the market every few months. This rapid development is leaving the classification criterion to continually be redefined. Therefore, the following information is deemed to be a guideline and is not considered to be a definite and extensive description.
Lasers in apply by medical practitioners ordinarily have low outputs of energy and power, and are thus placed in ANSI (American National Standards Institute) Class 2 category. Another essential organization is the LIA (Laser Institute of America). The majority of medical lasers fall into the ANSI Class 3 or 4 categories with many surgical lasers being in ANSI Class 4. A lot of medical and surgical lasers are classified by the Food and Drug Administration (Food and Drug Administration) as Class II or Class III medical devices.
Class 1: This class of lasers is considered not to pose any hazard when operated under and according to normal operating conditions. This category includes lasers that are completely enclosed like CD players, fiber-optics systems, or laser printers. These devices which cannot have emissions exceeding the maximum permitted coverage (MPE) under any conditions are considered to be class 1 systems.
A potential hazard can occur during the repair of such devices if the repair process involves operating the laser outside of the enclosure case.
The placement of hazard or warning labels are essential for this class inside the unit or underneath cover panels where the person performing the repair can be adequately warned of a potential hazard.
Class 2a: Not many lasers qualify for this class of low-power, visible light lasers. Any laser in this class is considered to not pose a threat if the beam of light is directly viewed for periods of time much less than 1000 seconds (about 16 minutes). Any visible light laser with a total output power less than 1 milliwatt, but greater than a few microwatts, could be class 2.
Class 2
This class of lasers includes visible light lasers that are intense enough that viewing the beam into a human eye can trigger the normal “aversion response”. An aversion response is when the eyelids close, or the head moves in order to avoid the light. It can occur within .25 seconds and includes the blink reflex time.
Class 3a: This class of lasers includes those emitting ultraviolet or infrared light too as those emitting visible light. All systems falling within the Class 1 AEL (Allowed Exposure Level) with laser output between .18mm and 1mm fall in this class. A lot of laser pointers are class 3a laser devices.
Class 3b: This class of lasers includes the same laser output spectrum as class 3a, but increases the output level to which of Class 2 AEL.
Class 4: This class of lasers includes any which exceeds the Class 2 AEL. Almost all every laser that produces an excess of .5 watts is in this class.
Laser Effect on Tissue
Lasers differ from other conventional sources of light because they are coherent, collimated, and monochromatic and they will be used in a pulse mode.
Coherence is demonstrated in both time and space and is defined by a rhythm with a logical pattern. Collimation is the emission of a powerful and narrow beam of light that travels almost completely in one direction and does not expand. Monochromaticity is an emission of one wavelength of a single coloring of light. Pulse mode is defined as short emission times (rather than one long wave) measured in milliseconds (10-3) on the aesthetic laser. Pulse modes have the ability to deliver an extremely high amount of power in a very short time.
All laser energy often is reflected, scattered, transmitted, or absorbed. The effect of laser light on human tissue can be a result of its interaction with which particular tissue. In order for a laser to be efficacious on the target tissue, it must be absorbed.
As lasers penetrate tissue, they could have a thermal (heat) effect. The optical light from the laser emits heat which is then transferred to the skin which, in turn, causes a reaction in the tissue. Obviously, the amount of reaction in the tissue is directly proportional to the temperature of the heat and how long the tissue is exposed to the heat source. The higher the temperature and the longer the epidermis is exposed can result in tissue destruction. In certain medical lasers, this phenomenon is useful for surgery or destruction of growths, like tumors. If lasers are used improperly, having said that, they have the unfortunate ability to produce unwanted burns and scarring.
As optical light passes through tissue it is frequently diffused by particles or changed by molecules. This phenomenon is termed optical scatter. With the longer wavelengths of the electromagnetic spectrum (red and near infrared) are weakly absorbed and, therefore, penetrate deeper into the tissue resulting in much less optical scatter. In the near and far infrared wavelengths, water in the tissue is the substance that absorbs light with a very superficial effect.
In order for lasers to be efficient in treating various pigmentation disorders or vascular lesions, the optical light needs to penetrate tissue. Within the tissue are light-absorbing substances called chromophores. The dominant chromophores present in epidermis are hemoglobin, melanin, water and collagen. These substances each respond differently to the colors of optical light in the electromagnetic spectrum. Melanin and hemoglobin are found to be very responsive in absorption of a broad spectrum of wavelengths. An adverse response to this phenomenon is that darker dermis types may just be at chance of hypopigmentation and decreased efficacy of vascular lesion procedures. Water absorbs wavelengths in the low ultraviolet and infrared spectrums (650-1200nm: near-red and infrared) and will absorb the deepest penetration of any wavelength.