Laser safety: practical measures and latest legislative requirements.
Lasers are used for a wide range of applications in operating
departments and all persons working in a laser environment are required
to understand the safety issues involved. This article details the
various hazards associated with laser use and the management structure,
procedures and control measures that should be implemented to ensure the
health and safety of staff and patients. Recommendations are made in the
context of the latest guidance and legislative requirements with
reference to common issues that may arise in the workplace.
KEYWORDS Laser safety / Ophthalmology / Laser hazards / Laser protection / Control measures/ Regulations
Lasers in medicine
Lasers in medicine (Environmental aspects)
Health care industry (Safety and security measures)
|Publication:||Name: Journal of Perioperative Practice Publisher: Association for Perioperative Practice Audience: Academic Format: Magazine/Journal Subject: Health; Health care industry Copyright: COPYRIGHT 2011 Association for Perioperative Practice ISSN: 1750-4589|
|Issue:||Date: Sept, 2011 Source Volume: 21 Source Issue: 9|
|Topic:||Event Code: 260 General services Computer Subject: Health care industry|
|Product:||Product Code: 3832848 Lasers for Medicine NAICS Code: 334510 Electromedical and Electrotherapeutic Apparatus Manufacturing SIC Code: 3845 Electromedical equipment; 8000 HEALTH SERVICES|
|Geographic:||Geographic Scope: United Kingdom Geographic Code: 4EUUK United Kingdom|
The first functioning laser was constructed by Theodore Maiman in 1960 using a ruby crystal to produce red laser light. Since then laser technology has been developed to be used in a wide range of applications including industry, communications and the medical sector. Whilst the benefits from the use of lasers are well documented there are a number of hazards associated with their use. Laser safety is essential in order to ensure the health and safety of all persons involved. The principles of laser safety involve assessing the hazards and risks of the work being carried out and ensuring that the proper management structure, administrative procedures, safety mechanisms and control measures are in place to minimise these risks. This article aims to discuss these aspects of laser safety within the operating department environment.
Laser physics and classification
In order to understand the hazards associated with lasers it is first necessary to be aware of the theory behind laser technology. Laser is an acronym for Light Amplification by Stimulated Emission of Radiation. The light produced by lasers is part of the electromagnetic (EM) spectrum of radiation (Figure 1) which encompasses everything from radiowaves and microwaves to X-rays and gamma rays. Laser light is either infra-red, visible or ultra violet, as seen at the centre of the spectrum. Radiation can be represented as waves and the wavelength varies across the EM spectrum. The particular wavelength of a laser determines its effect in body tissue.
[FIGURE 1 OMITTED]
The material inside a laser can be solid, liquid or gas. 'YAG' lasers are a common type of solid laser which are comprised of a crystal of yttrium aluminium garnet (YAG) with small amounts of other materials added. For example, neodymium (Nd) is added to make an Nd:YAG laser or holmium (Ho) to create a Ho:YAG laser. The term YAG does not therefore fully describe a laser as the added material can differ and will determine properties such as the wavelength. Liquid mediums are usually dyes and gas-based lasers include carbon dioxide, excimer and helium-neon (HeNe). Table 2 gives some examples of different surgical lasers with their typical wavelengths, the region of the EM spectrum that they belong in and some common areas of use. An aiming beam is incorporated into the unit. This is a low powered visible laser, such as HeNe, that the surgeon can use to align the beam with the target tissue.
Laser light has a number of important properties that distinguish it from other light sources (Figure 2). Firstly, all the light produced by one laser is of exactly the same colour or 'monochromatic', that is all the light waves have the same wavelength. Secondly, the light is 'coherent' or 'in phase' which means that the peaks and troughs of the waves all coincide with one another. Laser light is also highly 'collimated', that is focused by a lens into a small intense spot for cutting, coagulating or vaporising tissues.
The method by which this special laser light is produced begins with stimulated emission of photons of light from an atom. Figure 3 depicts an atom in its lowest energy or 'ground' state, and also in an excited state where the electron is in a higher energy level further from the centre or nucleus of the atom. During stimulated emission a light photon causes the electron to drop down into a lower energy level nearer to the nucleus and another light photon is produced that is identical to the first. There must be sufficient excited atoms in the laser material to start this process and this is achieved by feeding energy into the laser, usually in the form of electrical energy. The light photons produced are reflected to and fro between mirrors passing through the laser material many times causing further light photons to be emitted. This is known as amplification. When the laser is activated by the user the laser light is allowed to escape through a partially reflecting mirror. This can either be as a continuous beam or in pulses.
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
The delivery system used depends on the type of laser but a common method is the optical fibre. The laser light is reflected down the centre of the fibre which is designed to minimise the energy lost as the beam travels along. This property of optical fibres means that they are also commonly used in communication systems for transferring information over long distances. Optical fibres can be coupled to various applicators such as a slit lamp, hand held probe or indirect ophthalmoscope. This delivery system cannot be used for all wavelengths of laser; for example, an articulated arm is used for the carbon dioxide laser. This is a flexible jointed arm with mirrors at the bends to reflect the laser beam down the arm.
Lasers are classified between Class 1 lasers, which are not hazardous for continuous viewing, and Class 4 lasers, which can cause serious injuries. Surgical lasers are usually Class 3B or 4. Direct viewing of a Class 3B laser may cause serious eye injuries, even for short accidental exposures. Specular reflections (e.g. from a mirror or shiny surface) can also be hazardous. Class 4 lasers can also cause serious eye injuries even when viewing a diffuse reflection from a non-shiny surface, such as a wall. Lasers of this highest classification can also cause skin burns and may ignite flammable materials.
Laser hazards and risk
A hazard is something with the potential to cause injury. There are a number of hazards associated with laser use in a clinical environment, the most obvious being the laser light itself. Accidental exposure could be caused by a misaligned or misdirected laser beam, laser light escaping from the protective housing of the unit, or a broken or detached optical fibre. Reflections of the light from reflective instruments, surfaces or corneal contact lenses and binocular indirect ophthalmoscope viewing lenses could also constitute a hazard. Such an exposure could cause damage to the eyes, the type of damage inflicted depending on the laser wavelength. For example, the light from some lasers will be absorbed in the cornea and lens whereas for others it will penetrate to the retina. If the fovea or optic nerve is damaged then partial or total loss of vision may occur. For a patient the damage could be particularly severe if they are anaesthetised and unable to react. Skin burns may also be caused by an unintentional exposure. The Nominal Ocular Hazard Distance (NOHD) of a laser is the minimum distance a person would have to be standing from the laser for the beam not to cause eye or skin damage.
Fire hazard is particularly relevant when performing laser procedures close to anaesthetic tubes containing flammable gases. In addition, surgical drapes could also be ignited by a misdirected laser beam or the hot tip of a fibre or probe. Inhalation of the smoke produced during some laser treatments may cause airway irritation and nausea. It has also been suggested that there are other health risks associated with harmful bacteria and viruses contained within particles in the smoke plume as well as carcinogenesis (Alp et al 2006). As for any other electrical equipment the risk of electric shock can also be present with lasers.
Risk is defined as the likelihood of a hazard causing its adverse effect coupled with the severity of that effect. With the proper safety procedures in place the likelihood of laser incidents occurring should be relatively low; however in some situations there is the potential for the severity to be high. Risk assessments are a statutory requirement whose purpose is to identify the hazards associated with a given procedure, consider who might be harmed and how, and evaluate the risks considering the existing precautions. They are the basis for developing safe working procedures or 'local rules'.
Any adverse incident involving a medical device can be reported to the MHRA Adverse Incident Centre. Whilst this is optional, it is a useful register of issues that have arisen in the clinical environment. Certain incidents must also be reported to the Health and Safety Executive (HSE); for example those resulting in temporary or permanent loss of vision, electrical shock leading to unconsciousness or injuries requiring hospitalisation for more than 24 hours. Further guidance on injuries reportable to the HSE is given in the
Reporting of Injuries, Diseases and Dangerous Occurrences Regulations (RIDDOR) SI 1995/3163 (HMSO 1995).
The employer is legally responsible for the health and safety of employees and will have established management structures which encompass the safe use of lasers even where these are not expressed in those terms. They are likely to have appointed a Laser Protection Adviser (LPA) to provide advice and support to laser users within an organisation. They should have also appointed a Laser Protection Supervisor (LPS) who would be someone closely involved with laser work in the department and who would be primarily responsible for ensuring that laser work is carried out in accordance with the local rules. A deputy LPS may also be in place. One possible arrangement could be for an experienced doctor to act as a Clinical Laser Expert, assessing the competence of others to use the laser, whilst another member of staff acts as an operational LPS ensuring that local rules are followed, maintaining registers of laser users and records of training, and possibly arranging maintenance and servicing of the laser. There may be safety committees in place where these individuals report activity and concerns.
When thinking about laser safety a hierarchy should be followed. The first consideration should be equipment or engineering-related safety measures, such as safety interlocks on the laser itself (for example key switches), barriers such as room doors, blinds for windows and warning lights. Secondly appropriate administrative controls need to be in place such as local rules, training programmes and designated 'controlled' areas for laser use with appropriate warning signs displayed. Personal protection may be required if these primary hazard control methods are not sufficient, for example protective glasses. Finally contingency arrangements must be made, considering different situations such as working outside of normal hours, accidents and incidents, or other foreseen but unlikely occurrences. The LPA can advise and support these discussions.
The Controlled Area is the region around the laser where people may be present and in which specific systems of work are required in order to control hazards. The LPA will advise on the extent of the Controlled Area based on information such as the NOHD of the laser. This could be a treatment room in an eye clinic or an operating theatre. The boundaries of the area should be marked with warning signs and possibly warning lights and it may be necessary to cover windows or viewing panels in the doors with blinds to protect staff or members of the public from a stray laser beam. Access to the treatment area must be suitably restricted; doors may be locked or it may be sufficient to adhere to common operating theatre practice whereby staff only enter through the anaesthetic room during a procedure. If personal protective equipment is required in the form of eyewear then all persons in the Controlled Area should wear this, with the exception of the surgeon if filters are included in the viewing optics. Spare eyewear could be kept outside the Controlled Area should other staff need to enter during the laser procedure.
Eyewear must be marked with the wavelength of the laser for which it is suitable for use as well as a scale or 'L' number which gives the level of protection provided. The LPA can advise on whether the eyewear is appropriate for the particular laser in use. The glasses should be close fitting with side protection and must be in good condition. Eyewear must comply with The Personal Protective Equipment at Work Regulations SI 1992/2966 (HMSO 1992) and the British Standard BS EN 207:2009 (BSI 2010). In the case of laser eye surgery patients may require contralateral eye protection such as laser eye shields and this would be identified in the risk assessment.
Fire extinguishers should be located close to the Controlled Area and it may be advisable for sterile saline or water to be available during the procedure in the event of a fire on a patient. An optical fibre tip should never be left on a surgical drape during the procedure as the heat could ignite the drape.
With regard to the possible smoke plume hazard, it is recommended that a dedicated smoke evacuation system is used. Masks (including laser surgical masks) should never be used as the primary form of protection and operating theatre evacuation systems are also not suitable for plume removal.
Legislation and guidance
In addition to the RIDDOR 1995 regulations (SI 1995/3163) there are a multitude of regulations that apply to lasers. The Health and Safety at Work Act (HMSO 1974) imposes duties on everyone connected with work; employers have a duty to ensure the wellbeing of employees at work, employees have a duty to take reasonable care and manufacturers have a responsibility to ensure that products are safe through design. The Management of Health and Safety at Work Regulations SI 1999/3242 (HMSO 1999) discusses the requirement for carrying out risk assessments and recording the findings. The Personal Protective Equipment at Work Regulations SI 1992/2966 (HMSO 1992) states that employers must provide suitable and sufficient protection where required and that employees have a responsibility to wear this if provided. Employers must also provide warning signs where needed under The Health and Safety (Safety Signs and Signals) Regulations SI 1996/341 (HMSO 1996). Equipment provided for use at work should also be fit for purpose and maintained, as specified in The Provision and Use of Work Equipment Regulations SI 1998/2306 (HMSO 1998), and should be CE marked under The Medical Devices Regulations SI 2002/618 (HMSO 2002).
There are many other examples of such legislation, however a set of regulations recently came into force which directly apply to lasers: The Control of Artificial Optical Radiation at Work Regulations SI 2010/1140 (HMSO 2010a). These regulations cover all artificial lights, including those in offices and operating theatres, as well as lasers. Risk assessments are discussed and these must be carried out with the results recorded. In addition Exposure Limit Values (ELVs) are given which are levels of radiation that must not be exceeded in order to ensure that no injury occurs. Any area where there is the potential for someone to be exposed to radiation levels above the ELV must be demarcated and measures taken to reduce access to staff as much as is reasonably practicable. This area is referred to in other documentation as the Controlled Area. The regulations also discuss provisions for reducing risks and require that appropriate information and training is provided.
Many people will also be aware of the recent requirement for premises in England carrying out surgery using Class 3B or 4 lasers to register with the Care Quality Commission (CQC) under The Health and Social Care Act 2008 (Regulated Activities) Regulations SI 2010/781 (HMSO 2010).
Users of non-surgical Class 3B or 4 lasers for the regulated activity 'treatment of disease, disorder and injury' (Schedule 1 of the Regulations) must also register. Non-surgical cosmetic laser use is no longer regulated by the CQC. Registrations had to be completed in 2010 and a new guidance document Essential Standards of Quality and Safety (CQC 2010) sets out the requirements under the registration. The standards do not refer to legislation as these are already enforceable, but the MHRA guidance on the Safe Use of Lasers, Intense Light Source Systems and LEDs in Medical, Surgical, Dental and Aesthetic Practices (MHRA 2008) is included in the Schedule of Applicable Publications and is therefore expected to be followed.
British Standards and MHRA guidance
In addition to legislation there are a number of British Standards that cover lasers as well as the MHRA guidance document (MHRA 2008). The guidance gives useful advice covering many of the legislative requirements in a format that is easy to read. The document lays out the required safety management structure and the responsibilities of various persons from the employer to the laser users.
Laser users are referred to in the guidance as Authorised Users and may be anyone who operates the laser. Training for Authorised Users must be three-fold and must cover: equipment based training in the use of the laser possibly from the LPS or manufacturer/supplier, safety training, and clinical or procedural training. Records of all training must be available in case of inspection and may be collated in a laser folder or individual staff training files. The anticipated knowledge level of an Authorised User includes understanding of the nature of optical radiation, health hazards, hazard control procedures, local rules and contingency plans. Any other staff present during laser use should have received basic safety training, possibly from the LPS, and have read the local rules. All individuals have key responsibilities to keep the patient and their colleagues safe.
It is recommended that, in addition to routine servicing by the manufacturer or supplier, the hospital should also ensure that appropriate quality assurance tests are carried out on the laser. These local checks would be carried out on a more frequent daily/weekly basis and might include:
* checking laser output termination
* checking alignment of the aiming and treatment beams
* ensuring that any warning lights are operational
* visually inspecting eyewear or filters in equipment for damage or scratches
* checking that protective blinds, windows and doors are functioning correctly and are undamaged.
The guidance also includes details of administration requirements such as risk assessments and local rules, as well as recommendations on controlling hazards.
Laser safety documentation
A risk assessment must be carried out prior to commencing laser work and this should be reviewed regularly, in particular following any changes in laser use. Hazards and risks have been discussed previously and these must be considered for the individual situation as differences in environment, type of equipment and procedures being carried out could affect the findings of the assessment. For example, the risk of a misdirected laser beam causing an eye injury to a member of staff has a lower likelihood if the laser is being used via a slit lamp in an eye clinic room as opposed to an optical fibre in an operating theatre. In addition, if a room has windows or viewing panels in the doors, there is a risk of a misdirected beam causing an eye injury to other staff or members of the public outside the treatment room. Existing control measures might include blinds that cover the windows, otherwise the need to install these should be included as an action point from the risk assessment. Hospitals/clinics often have their own format for a risk assessment and risks identified need to be evaluated in terms of their likelihood and severity according to local policy.
The findings of the risk assessment should be considered when writing the local rules. Local rules are part of the employer's means of complying with the Health and Safety at Work Act and should ensure that all employees are working in a safe environment and that patients are treated safely. They need to be in place for each laser and must cover any situation in which a particular laser could be used, for example a laser could be used in the eye clinic as well as operating theatres and may be used with different delivery systems. The following areas should be covered in the local rules:
* Details of the laser system
* Brief description of hazards to persons
* Description of the Controlled Area and access restrictions (including all areas used)
* The management safety structure, including responsibilities of various persons such as the employer, theatre manager, LPS, Clinical Laser Expert, LPA and Authorised Users.
* Training requirements
* Restrictions of use including safe keeping and issue of the laser key. A list of Authorised Users should be kept
* Methods of safe working and operating procedures
* Personal protective equipment
* Pre-use safety checks and instructions
* Emergency procedures.
The local rules should be displayed clearly in the treatment room or kept with the laser. As for the risk assessment, local rules should be reviewed regularly. All staff involved in the use of the laser or who are present in the room during laser use should have read the local rules and signed a declaration to acknowledge that they have read, understood and will adhere to them.
There have been a number of recent and significant changes to laser safety legislation including the first set of regulations dedicated to the use of artificial optical radiation in the workplace. This has underlined a number of the requirements already detailed in standards and guidance. The importance of carrying out and reviewing risk assessments cannot be over emphasised. This is the starting point for identifying the hazards and risks for the specific working environment, laser and clinical procedures being carried out. It ensures that the control measures and local rules put in place are relevant to the local situation and are therefore useful and practical. Whether developing a framework of laser safety from scratch or trying to improve current systems in place, the Laser Protection Adviser should always be consulted and will be able to provide practical advice based on the local situation. It should not be forgotten that the Authorised Users have a key role in the safe use of any laser and must be trained and competent to carry out their roles, maintaining an awareness of the safety issues at all times.
I would like to thank Debbie Peet, LPA and Head of Radiation Protection, Royal Surrey County Hospital for her expert advice.
No competing interests declared
Provenance and Peer review: Commissioned by the editor; Peer reviewed; Accepted for publication July 2011.
Alp E, BijL D, Bleichrodt R P, Hansson B, Voss A 2006 Surgical smoke and infection control Journal of Hospital Infection 62 1-5
British Standards Institution 2010 BS EN 207:2009 Personal eye-protection equipment. Filters and eye-protectors against laser radiation (laser eye-protectors) London, BSI
Care Quality Commission 2010 Essential standards of quality and safety London, CQC
Her Majesty's Stationery Office 1974 Health and safety at work Act c.37 London, HMSO
Her Majesty's Stationery Office 1992 The personal protective equipment at work regulations SI1992/2966 London, HMSO
Her Majesty's Stationery Office 1995 The reporting of injuries, diseases and dangerous occurrences regulations SI1995/3163 London, HMSO
Her Majesty's Stationery Office 1996 The health and safety (safety signs and signals) regulations SI1996/341 London, HMSO
Her Majesty's Stationery Office 1998 The provision and use of work equipment regulations SI1998/2306 London, HMSO
Her Majesty's Stationery Office 1999 The management of health and safety at work regulations SI1999/3242 London, HMSO
Her Majesty's Stationery Office 2002 The medical devices regulations SI 2002/618 London, HMSO
Her Majesty's Stationery Office 2010a The control of artificial optical radiation at work regulations SI 2010/1140 London, HMSO
Her Majesty's Stationery Office 2010b The health and social care Act 2008 (regulated activities) regulations SI 2010/781 London, HMSO
Medicines and Healthcare products Regulatory Agency 2008 Guidance on the safe use of lasers, intense light source systems and LEDs in medical, surgical, dental and aesthetic practices DB2008(03) London, MHRA
Correspondence address: Mary Simon, Regional Radiation Protection Service, Royal Surrey County Hospital, Egerton Rd, Guildford, Surrey, GU2 7XX. Email: firstname.lastname@example.org
About the author
BSc (Hons), MSC, MIPEM
Medical Physicist, Regional Radiation Protection Service, Royal Surrey County Hospital, Guildford
Table 2 Examples of surgical lasers, with reference to MHRA guidance (MHRA 2008) Laser material Wavelength Region of EM Examples of surgical uses Carbon dioxide, 10,600 Infrared ENT, gynaecology, maxillofacial Ho:YAG 2100 Infrared Urology Nd:YAG 1064 Infrared Ophthalmology, gynaecology Diode 810-980 Infrared Ophthalmology, varicose veins HeNe 633 Red Aiming beam KTP 532 Green gynaecology, urology, ophtalmology, ENT Dye 400-700 Visible Urology, dermatology Excimer 160-350 Ultraviolet Ophthalmology
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