Core of Knowledge in
Safe Use of Lasers & IPL’s
in healthcare
Mr John Saunderson, Consultant Medical Physicist
Why laser core
of knowledge?
Core of Knowledge syllabus
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Understand the characteristics of optical radiation emitted from different types of equipment.
Familiar with the intended purpose of the optical radiation equipment.
Aware of the meaning of the warning labels associated with optical radiation equipment.
The effects of exposure and health hazards, including eye, skin and tissue, which can arise from the use of laser, IPL
or other optical radiation equipment.
Equipment related hazards, which can arise from the use of laser, IPL or other optical radiation devices, including
equipment malfunctions.
Management of equipment and the role of personnel, including Controlled Areas and the role of the Laser Protection
Adviser and Supervisor.
The principles and requirements of equipment quality assurance processes and procedures.
Hazards related to individuals through use of optical radiation equipment, including electrical hazards, fire risks and
smoke plume effects.
Hazards to patients associated with optical radiation treatment procedures and methods of minimising risks.
Hazard control procedures, including the use of personal protection.
Hazards from reflections or absorption of the optical radiation beam with respect to instruments or surfaces or other
equipment.
General principles of how to deal with a suspected accidental exposure to optical radiation.
Aware of the basic principles of the maximum permissible exposure levels and the precautions required to ensure
that exposure of unprotected skin and eyes of those present is less than the maximum permissible levels.
Additional precautions that may be necessary when undertaking non-routine activities with the equipment.
The safety procedures and policies governing optical radiation equipment use, including the local rules, Controlled
Area, emergency action and accident reporting procedures.
Understand the role of the Laser Protection Advisor and Laser Protection Supervisor.
Be aware of the relevant legislation and standards that pertain to lasers and IPLs.
Principles of risk assessment.
Be familiar with the basic principles of the administration of safety.
www.hullrad.org.uk
Nature of Laser Radiation
Light
Amplification by the
Stimulated
Emission of
Radiation
Electromagnetic Spectrum
740-620 nm - red
620-585 nm - orange
585-575 nm - yellow
575-500 nm - green
500-445 nm - blue
445-425 nm - indigo
425-390 nm - violet
Light Sources & Lasers
• Spontaneous emission
– filament lamp
– fluorescent lamp
– neon lights
– most LEDs
– fire
– fluorescence
– IPL (intense pulsed light source)
• Stimulated emission
– laser
Spontaneous emission
Atom
Energy
(e.g. electrical current through filament, or electrical discharge
through a fluorescent tube, or UV light on a fluorescent material)
Excited atom
Spontaneous emission
Atom
Photon emitted
Any direction.
Spontaneous emission
Stimulated emission
Atom
Energy
(e.g. electrical discharge, flash lamp, electrical current)
Excited atom
Stimulated emission
Incoming photon
(correct wavelength)
Stimulated emission
Two photons emitted
IF correct wavelength then
 STIMULATED EMISSION
Same wavelength and same direction
Incoming photon
(wrong wavelength)
Scattered photon
LASER
Tube filled with laser medium
(e.g. helium-neon gas for HeNe laser)
LASER
Energy
(e.g. electrical discharge, flash lamp, electrical current)
LASER
Population Inversion or “pumping”
Energy
(e.g. electrical discharge, flash lamp, electrical current)
LASER
Spontaneous emission takes place
LASER
Some photons will cause stimulated
emission
LASER
Mirrors at either end reflect those
photons travelling along tube
LASER
More simulated emission in same direction
along the tube
LASER
Amplification
One mirror (output coupler) “leaky”
allowing laser beam to emerge
•All photons same wavelength (colour)
•All photons travelling in same direction
•Can produced extremely short pulses of high energy
Non-coherent vs laser light source
Extended vs point source
• 40 Watt incandescent bulb
• ~2% efficient
•  0.8 W = 800 mW light energy
• 1 mW laser pointer
• 800 x less light energy emitted
than 40 W bulb
Extended vs point source
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800 mW @ 100 cm
Irradiance, E = 800 ÷ (4 x 1002)
E = 0.006 mW/cm2
Similar in all directions
1 mW pointer, 0.15cm beam diameter
In most direction, E = 0 all distances
In beam, E = 1 mW ÷ ( x 0.152)
E = 14 mW/cm2
i.e. 2,300 x more than 40 W bulb
Compared to 40 W bulb @ 1 m
(assuming 1.5 mm dia beam)
• 1 mW Laser pointer
x 2,300 @ 1 m
• 2W Pascal - 2 W
x 4,600,000 @ 1 m
• 40 W CO2 laser
x 91,000,000 @ 1 m
(Note, other effects make
this even higher on retina)
Non-coherent vs laser light source
Chromatic Aberration
Lasers are “monochromatic” (single wavelength)
so minimal “chromatic aberration”
Non-coherent vs laser light source
Extended vs Point Sources
Image
Object / Source
Lens
Image
Object / Source
Lens
1
Extended source
Image
Object / Source
Lens
2
Distance object
Image
 Object / Source
Lens
Distance object
Image
Object / Source
Parallel rays, non divergence, “collimated” = virtual
point source
All parallel beams will focus to about 20 microns
(0.02 mm)
e.g. for 1 mW laser pointer
E(skin) = 14 mW/cm2 (from earlier)
•1.5 mm beam focussed to 20 microns
 (1.5/0.020)2 =  5,600 power density
E(retina) = 70,000 mW/cm2
(assuming 10% absorption in eye)
•So EYE is at much greater hazard than SKIN for
wavelengths focussed by cornea & lens
•Eye is at greater hazard from LASERS than from other
light sources
•(Lasers also more useful for creating a concentrated
point source)
Intrabeam, specular reflections,
diffuse reflections
• Intrabeam
– directly shone into eye
– if focussed by eye, 20 m spot on retina
Intrabeam Viewing
• If beam larger than pupil only proportion of beam
will be focussed on retina
• If magnifying glass etc used a greater proportion
will be focused on retina
Intrabeam Viewing
• If beam smaller than pupil diameter, magnifying
glass make no difference to retina (would to skin)
Specular reflection
= mirror-like reflection
• Potentially same hazard as direct intrabeam
viewing
Diffuse Reflection
• e.g. seeing laser spot on wall
• Not a point source,
– so not focussed to 20 m
• May still be hazardous
Lenses, mirrors & fibres
• All produce a divergent laser beam
Optical fibre
Mirror
Lens
Lenses, mirrors & fibres
• Concave mirrors and convex lenses
– focal spot - high irradiance
– beam then gets broader
– if bigger than pupil then hazard reduces with
distance
• Optical fibre
– diverges from exiting fibre
– if bigger than pupil then hazard reduces with
distance
Video 1
Types of Medical Laser
melanin
Ho:YAG
Ar
Nd:YAG
scale)
Absorption (log
12.5
CO2
water
HbO2
0
0
200
400
1000
5000
12.5
10000
Wavelength (nm)
UV < 390
390 > visible > 740
740 < infrared
Taken from A Non-Binding Guide to the Artificial Optical Radiation Directive 2006/25/EC, Radiation Protection Division, Health
Protection Agency
http://www.hse.gov.uk/radiation/nonionising/aor-guide.pdf
Relative Absorption Coefficients (log
scale)
12.5
HbO2
H2O
Melanin
ticks
CO2 laser
Nd:YAG laser

0
200
0
400
600
1000
IRA
2000
IRB
Wavelength / nm
4000
IRC
12.5
Relative Absorption Coefficients (log
scale)
12.5
HbO2
H2O
Melanin
ticks
CO2 laser
Nd:YAG laser

Argon laser

0
200
0
400
600
VIBGYOR
1000
2000
Wavelength / nm
KTP-Nd:YAG - frequency doubling to 532 nm (green)
4000
12.5
melanin
Ho:YAG
Ar
Nd:YAG
scale)
Absorption (log
12.5
CO2
water
HbO2
0
0
200
400
1000
5000
12.5
10000
Wavelength (nm)
UV < 390
390 > visible > 740
740 < infrared
Absorption of electromagnetic radiation in the eye (Sliney & Wolbarsht 1980)
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• Continuous beam
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• Single pulse
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• Interrupted pulses
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Laser Safety Classes
Video 2
Laser Device Classes & Hazards
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Class 1
Class 1M
Class 2
Class 2M
Class 3R
Class 3B
Class 4
• Applies to device as a whole.
MPE = Maximum permissible exposure
• Class 1
– no risk to eyes (including using optical viewing
instruments)
– no risk to skin
– (either low power device or totally encased)
• Class 1M
– no risk to the naked eye
– no risk to skin
• Class 2
– no risk to eyes for short term exposure
(including using optical viewing instruments)
– no risk to skin
– (visible, so blink response protects)
– (may cause dazzle or flash blindness)
• Class 2M
– no risk to naked eye for short time exposure
– no risk to skin
• Class 3R
– low risk to eyes
– no risk to skin
– (risk for intentional intrabeam viewing only)
– (may be a dazzle hazard)
• Class 3B
– medium to high risk to eyes
– low risk to skin
– (aversion response protects skin, or must be
focussed to such a small spot that pin-prick
effect only)
• Class 4
– high risk to eyes and skin
– diffuse reflection may be hazardous
– (possible fire hazard)
HEYH Trust CP137
Health & Safety at Work Policy
- Lasers -
• Includes safety of class 3B and class 4 lasers
Safety Principles
1. Engineering
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e.g. doors, blinds
2. Systems of work
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e.g. Local Rules, warning signs, etc
3. Personal protective equipment (PPE)
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e.g. Laser safety eyewear
Risk Assessments
Risk Assessments
Laser Safety Structure
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Risk assessment
Controlled Area
Local Rules
Laser Protection Supervisor
Laser Protection Adviser
Authorised Operators and Assistants
Controlled Area
• Must contain the risk
• Need to know nominal ocular hazard
distance/zone (NOHD, or NOHZ)
– i.e. distance where exposure level < MPE
– e.g. Lithotripsy laser - 80 centimetres
– e.g. Surgical CO2 - 40 metres
• Walls, blinds, doors (without gaps), etc.
• Lock doors unless can justify not
• Warning signs at every entrance
Local Rules
(How to work safely in the Controlled Area)
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Specific to each laser
What are hazards?
Controlled area - limit area of hazard - signs
Users & Laser Protection Supervisor
Safety precautions (e.g. eyewear, blinds)
Methods of safe working, etc.
• Adverse incident procedure, LPA, etc.
Warning Signs
LASER
Ultraviolet
RF radiation
Hazardous
magnetic field
IONISING RADIATION
(e.g. X-rays)
Example
Laser Protection Supervisor
Laser Protection Adviser
Authorised Users
Hull and East Yorkshire Hospitals
NHS Trust
L AS E R
SA F ET Y
AUTHORISED LASER OPERATOR (CLINICAL)
Laser:
I have read and understand
 the Trust Laser Radiation Health & Safety Policy,
 the Local Rules & relevant sections of the manufacturer’s instructions for
the above laser
I understand the responsibilities of Authorised Operators towards staff and patients,
and undertake to use the laser in a safe manner, within my clinical competence.
Name:
Position:
Signature:
Date:
If the operator is not a Consultant, this statement should be countersigned by the appropriate
Clinical Coordinator or Consultant:
(This statement should be kept by the Laser Protection Supervisor, and a copy sent to the Laser Protection Adviser).
Authorised Users
Incidents
MDA “One Liners” - Eye risk?
August 2002 (Issue 17)
•MDA has become aware of the use of
inappropriate filters for lasers used in
ophthalmic surgery. This can lead to
permanent eye damage for the operator.
When connecting a laser to a protective system with filters,
ensure that the wavelengths of laser radiation for which the
filter offer protection match the output wavelength of the
laser. If a fault is suspected with the filters, the procedure
should be discontinued and the filters examined by a trained
engineer.
Example
• Laser
• 520-575 nm Green, 2 W
• 568-575 nm Yellow, 1 W
• 670 nm Red (aim), < 5 mW
• Goggles labelled
• 560-570 nm OD>4
• 570-580 nm OD>5
• 580-650 nm OD>6
Example
• Laser
• 520-575 nm Green, 2 W
• 568-575 nm Yellow, 1 W
• 670 nm Red (aim), < 5 mW
• Goggles labelled
• 560-570 nm OD>4
• 570-580 nm OD>5
• 580-650 nm OD>6
MDA “One Liners” - Hind Sight?
March 2000 (Issue 8)
Two separate incidents reported to MDA
involving faulty laser equipment resulted in
permanent retinal damage (one to a patient
and one to the operator). In both cases, the
operator had noticed that the equipment was
behaving unusually but carried on with the
procedure.
Abnormal performance of any equipment should be
questioned immediately.
Laser Safety Eyewear
Laser Eyewear Labelling
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DI 1060 L7 X Z
620 TO 700 nm OD 2
CARBON DIOXIDE, O.D. 10 @ 10600 NM
DIR 690 - 1290 L4
D 1064 L7, IR 1064 L8, DIR 1350 - 1400 L7,
DIR > 1400 - 1580 L5, DI 2090 - 2100 L5, DI
2900 - 2940 L5
D = continuous wave laser, I = pulsed laser (0.1 ms - 100 ms)
R = giant pulsed laser (1 ns - 10 s), M = mode-coupled pulse laser (< 1 ns)
Wavelength
• Number before the L in nanometres
• “Colour” of beam
• May be single number (e.g. 10600) or a
range (e.g. 2090 – 2100)
• Wavelength on laser should fall within
range on eyewear
Optical Density
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Number after the L
Strength of filter
OD 1 – only 1/10th of laser light transmitted
OD2 - 1/100th,
OD3 - 1/1000th, etc.
Local rules should say strength required.
Note – higher ODs may be very dark
DIR 690 - 1290 L4
1
/10000th of 690-1290 nm laser light
transmitted
Laser
Wavelength
Suitable?
CO2
10600 nm
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Ho:YAG
2100 nm
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Nd:YAG
1060 nm

LaserTripter
504 nm
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Argon
477 or 515 nm
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1047 - 1400 DI L7
1047 - 1350 R L8
> 1350 - 1400 R L7
>1400 - 1580 DI L5
2090 - 2100 DI L5
2900 - 2940 DI L5
10600 DI L5
Laser
Wavelength
Transmission
CO2
10600 nm
1/100,000
Ho:YAG
2100 nm
1/100,000
Nd:YAG
1060 nm
1/10,000,000
LaserTripter
504 nm
?
Argon
477 or 515 nm
?
Laser Safety
Eyewear
• Must match the laser in use (whether
specs or filter)
• Must be cleaned in accordance with
manufacturer’s instructions
• If damaged, take out of service
• Consider protection of patient’s eyes
Other Hazards
• Fire
• Anaesthetic gas ignition
• Plumes
• Electrical hazard
Can be fatal
Electrical Hazard
• Big capacitor used to drive laser, so
dangerous even when unplugged
• Several fatalities from lasers
• DON’T OPEN OR DISMANTLE LASER
• Don’t let anyone else do so unless they are
suitably qualified and trained.
Plume
• Mostly steam, carbon particles, cellular
products - average 0.3 m particles
• May contain formaldehyde, hydrogen
cyanide, hydrocarbons, mutagens
• Human papilloma DNA identified in plume
from surgery to remove of papillomas
• Use smoke extraction with filter (<0.1m) (not
hospital vacuum)
• Staff and patients should wear well-fitting
high filtration face masks where plume
hazard identified.
Odds and ends
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Maintenance
Reflections of polished instruments
Check fibre. Fibre breaks.
Oxygen hazard.
And finally ....
Example of laser accident
• Dr. C. David Decker
• Nd:YAG, 6mJ, 10 ns pulse
• Goggles available, but
– Tunnel vision
– Clouded up
– Uncomfortable
– So not worn
• Reflection beam hit eye
• Pop!
Goldman-Fields Scan of Dr Decker’s
damaged eye 4 months after accident
• Damage under highintensity illumination
(red)
• Damage under lowintensity illumination
(blue)
• Laser induced
blind spots (pink)
• Optic nerve blind spot
(orange)
fin