Medical Laser Risk Assessment
Hazards and risks
We will define a HAZARD as, something that can cause harm.
And RISK as, the probability of the hazard causing harm and the severity of that harm.
For example the laser machine is the hazard and the risk is the probability of damage to the eye and skin from the light emitted from the machines.
Risk to the eye
The eye is at particular risk for the following reasons:
- Damage to the retina (back of the eye) is likely to be irreparable
- Damage can occur at large distances from the laser aperture
- Damage can occur from exposure to very low power lasers
- Even reflections can be hazardous
Even light of relatively low energy can be a hazard to the retina. This is because the lens of the eye focuses light onto a very small point at the back of the eye which greatly increases the intensity.
Who is at risk
It is sometimes helpful to broadly categorise the various 'at risk groups'. These may include;
- Staff: Operators, assisting staff and even those outside the room,
- Patients / Clients,
- Members of the public.
Non-Beam Hazards
In addition to direct eye (and other tissue) damage, the laser equipment may give rise to other hazards, such as;
- Laser Generated Airborne Contaminants (Laser Plume),
- Fire / Explosion,
- Electrocution,
- Hazardous substances within the laser machine,
- Personal safety,
- Treatment related adverse effects,
- Risk of litigation.
These should also be taken into account as part of the risk assessment process.
Risk Assessment Process (medical, cosmetic, dental applications)
The risk assessment is a process designed to identify any hazards, quantify the risks from those hazards and look at appropriate safety controls that may need to be put in place. The risk posed by the laser will vary depending upon a number of factors such as;
a) Wavelength of the laser,
b) Output of the laser (maximum power or energy),
c) How the laser is used (e.g. inside the patient or free-hand.
In essence we will want to find out if it is possible to be exposed to a laser beam of sufficient intensity to cause damage (to the eye or skin). We then would decide if there is a reasonable probability of this happening.
Safe Distance
Since medical and cosmetic lasers are usually designed to have some effect on the human body, it is reasonable to assume that, at source, the beam will exceed the safe intensity (known as the Maximum Permissible Exposure) and will present a hazard.
However, the beam will then diverge to some extent and at some point the intensity will be low enough for the beam to become safe. The distance at which this happens is known as the Nominal Ocular Hazard distance (NOHD).
This hazard distance can be calculated if factors such as the output, divergence and aperture size are known. However, with modern medical laser equipment, this information can usually be obtained from the equipment supplier/manufacturer and is often listed in the user manual.
Knowing the hazard distance will help us decide whether certain controls are needed to ensure the laser light does not escape the confines of the area. Window coverings may be needed if the NOHD is larger than the room dimensions for example. It is not absolutely necessary to know the NOHD however. In practice, many people just assume the NOHD exceeds the room dimensions as this allows any laser to be used in the facility (without costly retrofitting blinds etc.) and a consistent set of procedures followed.
Protective eyewear (laser)
Assuming protective eyewear will be needed (as it usually is), we will also need to know what level of protection is needed. Historically, this is usually taken to be the level of attenuation needed to make the laser 'safe' at a distance of 0.1m from the beam and is expressed as an 'optical density'. Again, the eyewear specification will almost certainly be described in the equipment manual.
Sources of initial information?
Details such as equipment specification, hazard distance and eyewear specification can be obtained from a number of sources;
a) Specialist safety adviser (laser protection adviser),
b) Equipment supplier,
c) Equipment manufacturer,
d) User manual and training materials,
e) Equipment labels.
Who can carry out the risk assessment?
Any competent person can lead the risk assessment process. However, we usually to refer to the 'risk assessment team'. This may include;
a) Safety adviser (laser protection adviser),
b) Laser operator(s),
c) Facility manager.
Documenting the risk assessment?
In UK law, the significant findings of the risk assessment must be documented if the business employs five or more people. It is generally recommended that the risk assessment is documented regardless though, as otherwise there may be no evidence that a risk assessment has actually been done.
When should the risk assessment be revisited?
The risk assessment should undergo review;
a) Periodically,
b) Following any significant changes (equipment, room, treatments),
c) Following any incident,
d) Following any relevant changes in legislation.
Legal requirement for a laser risk assessment
Under the Management Health and Safety at Work Regulations 1999, a suitable and sufficient risk assessment should be undertaken. This is reinforced in The Control of Artificial Optical Radiation at Work Regulations 2010 which also states that the following must be included where applicable:
- measurements or calculations of the levels of optical radiation, if necessary
- consideration of the level, wavelength and duration of foreseeable exposure
- the exposure limit values
- effects of exposure on 'at risk' groups
- consideration of photosensitising chemical substances
- risk of temporary blinding, explosion or fire
- assessment of the availability of alternative equipment to reduce exposure
- appropriate health surveillance information
- manufacturers information
Specialist (laser) health and safety consultants
Specialist medical laser safety advisers are often referred to as Laser Protection Advisers (LPAs). In accordance with Department of Health guidance, it is common practice to use the services of an LPA to help carry out and document the risk assessment.
We offer sensible and proportionate laser safety consultancy services in line with Health and Safety Executive guidelines regarding specialist consultants. There are a number of advantages to appointing a qualified, registered (OSHCR) expert;
Avoid costly 'over-the-top' or unnecessary actions,
Hazards and legal compliance issues will not be missed.
Experienced advisers will have knowledge of a range of solutions to draw upon.
Assurance that all advice is up-to-date with current legislation.
Demonstrates to the regulators that you have obtained the best possible advice.
Gives a strong position with the insurance companies.
For Reference: Definitions of MPE and NOHD
Maximum permissible exposure
Various exposure data has been analysed and international safety committees have been able to publish levels of intense light above which it is deemed that harm will occur.
The Maximum Permissible Exposure (MPE) is defined as,
The level of optical radiation to which, under normal circumstances, persons may be exposed without suffering effects.
The MPE varies depending upon;
a) Wavelength of light
b) Duration of exposure
c) Beam intensity
d) Target tissue (eye or skin)
MPE figures are typically given in terms of energy or power density.
Hazard Distance
All light sources spread out as they propagate away from their origin. At a certain distance the intensity of the light will not be strong enough to cause damage to the eye. This distance is known as the Nominal Ocular Hazard Distance (NOHD).
A technical definition of the NOHD is,
The Minimum distance from the light source at which the exposure to the beam falls below the Maximum Permissible Exposure (MPE)
This is useful when determining the safety controls of a particular facility. It may be of the order of a few centimetres (physiotherapy lasers) or tens of meters. It is mainly determined by the divergence of the beam but wavelength, duration of exposure and output power all have an effect.
Light from an IPL spreads out quickly. In theory, the hazard distance should be relatively short. However, in the absence of manufacturer data, we can often just assume the worst case of "greater than room dimensions".
