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The term "laser" is an acronym that stands for "Light Amplification by Stimulated Emission of Radiation". Laser light is a form of non-ionizing radiation. Laser equipment produces and amplifies light that has unique properties that cannot be produced any other way. The light that it produces is monochromatic - it is composed of one single colour at a specific wavelength. Laser radiation can be generated in different parts of the spectrum - ultraviolet (UV), visible light, and infrared (IR).
The color of laser light is usually described in terms of the wavelength of the laser radiation. The most common unit used for the wavelength of laser is a nanometer (nm - one billionth of a metre). Light from other sources is made up of combination of colours at various wavelengths.
Another property of lasers is they are coherent light sources. This means that lasers produce monochromatic light (i.e., with a single or selected wavelength) in which the light “particles” or photons all travel in the same direction. This allows laser beams to be very focused (collimated) so they do not fan out like the light beam of a flashlight. Since the light beam can be contained in a very narrow beam, it has a high radiant power per unit area. These properties enable laser devices to produce powerful laser beams that can even cut metal. Lasers are also used in medicine for cutting, sealing and surgical procedures.
A wide variety of lasers are used in health care facilities. The type of laser depends on the purpose of use. Lasers can be used as knives or probes and for imaging techniques. For example, laser knives can make cuts that do not bleed. They can be used to smooth skin wrinkles or remove skin moles, cysts, tattoos, spider veins, and so forth. Some commonly used lasers are given in the following table.
|Commonly Used Lasers in Health Care|
|Type||Radiation Type/Wavelength in|
|Examples of Application|
|Carbon dioxide (gas laser)||Infrared/ 10,600||Surgery: Incision and excision by vaporization|
|Argon (gas laser)||Visible, blue/ 488||Sealing blood vessels in retina, plastic surgery|
|Argon (gas laser)||Visible, green/ 514||Sealing blood vessels in retina, plastic surgery|
|Krypton KPT 532 (gas laser)||Visible, green/ 532||Surgery: Cutting, coagulation, and vaporization of tissues|
|Nd:YAG* (continuous wave - solid state laser)||Infrared/ 1,064||General surgery|
|Nd:YAG* (Q-switched - solid state laser)||Visible, red/ 632||Ophthalmology: cutting tissues|
|Helium-Neon (gas laser)||Visible, red/ 632||Alignment: for aiming invisible beams|
|Ruby (solid state laser)||Visible, red/ 694||Plastic surgery, Dermatology: Destroying tissues|
|Rhodamine 6G Dye (Tunable - dye laser)||Visible/ 570-650||Treatment of malignant tissues; red (630 nm) commonly used|
*Neodymium-doped Yttrium Aluminum Garnet
There are two types of laser hazards: the laser beam hazards and the non-beam hazards. Laser beam hazards include eye and skin burns which are due to laser beam shining on a person's body. Non-beam hazards are associated with the laser equipment or the hazardous substances released from the laser equipment, and fumes emitted from materials exposed to laser beams, including laser-plumes produced during surgical procedures.
Sources of laser hazards include:
Yes, standards such as the following are available to develop a safe work practice program:
Note: Always check with your local jurisdiction to determine if your workplace must follow a specific standard.
The eye is the most vulnerable to injury from laser beam. The potential for injury depends on the power and wave length of the laser beam (light). Intense bright visible light makes us blink as a reflex reaction. This closing of the eye provides some degree of protection. However, visible laser light can be so intense that it can do damage faster than a blink of an eye. The invisible, infrared laser beam such as carbon dioxide (CO2) laser beam, does not produce a bright light that would cause the blinking reflex or the pupil to constrict and, therefore, chances of injury are greater compared to visible light beam of equal intensity.
The location of the damage depends on the optical nature of the laser beam. Lasers in the visible light and near infrared range focus on retina. Therefore the injuries produced are retinal burns. The infrared radiation is absorbed in the cornea and may cause corneal damage and loss of vision.
Every piece of laser equipment has built-in engineering controls such as protective housing, fail-safe interlocks, master switches, beam stops and attenuators (e.g., light absorbers) to prevent accidental exposure. However, eye protection is needed while using Class 3B or Class 4 type lasers to prevent harmful exposure from reflected and scattered laser beams.
The ability of eye wear to filter the laser beam is expressed in terms of optical density. Optical density, type of laser, and visibility required are all important factors in the selection of protective eye wear. Protective eye wear may not provide the same degree of protection for infrared as for visible light and ultraviolet laser beams. Goggles with side shields are preferred because they provide protection against back reflection and side entrance of stray laser beams.
Consult appropriate standards such as CSA Standard Z94.3.1-16: Guideline for selection, use, and care of eye and face protectorss or American National Standards Institute / International Safety Equipment Association (ANSI/ISEA) Standard Z87.1-2015 for guidance on selecting protective eye wear for your specific application.
Plastic versus glass lenses: Protective eye glasses typically are available with plastic lenses. Plastic lenses are light weight and can be molded into comfortable shapes. However, care is needed because they can be affected by heat, and/or UV radiation which can darken the lens or decrease its ability to absorb laser energy.
Alignment eye wear: This type of eye wear is used for low power visible laser beams. Alignment eye wear should not be worn during the operation of high power or invisible laser beams. Instead, safety eye wear that provides adequate protection should be worn.
The potential for skin damage depends on the type of laser, power of the laser beam, and the duration of exposure. The type of damage may range from localized reddening to charring and deep incision.
Protective clothing (gown, cap, mask), gloves, and safety eye wear may be required for working near a laser. Consult manufacturer's operating procedures and check with the laser safety officer to determine the specific needs for personal protective equipment and clothing.
A fire can be started when laser beam or reflection of the beam strikes a combustible material such as rubber, plastic, human tissues, paper products, skin treated with acetone and alcohol-based preparations, human hair, and intestinal gases. Fire hazards are of particular concern in oxygen-rich atmospheres when oxygen or when nitrous oxide is being used.
Many lasers use high voltage and high current electrical power. The danger of electrical shock or electrocution arises when an untrained or unauthorized person tries to perform maintenance work without following the proper safety procedures. ANSI Standard Z136.3-2018 outlines electrical safety procedures applicable to laser equipment. Electrical safety requirements include the following:
The ANSI Standard Z136.1 recommends a laser safety program for workplaces using class 3B or class 4 lasers. Following are the essential components of a laser safety program:
In workplaces where a class 3B or Class 4 laser is used, a laser safety officer (LSO) must be on staff. The laser safety officer must do the following to ensure safe use of lasers.