Safety of Lasers and Intense Light Professor Laurence J. Walsh © 2012

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Safety of Lasers and Intense Light and glare are concerns Professor Laurence J. Walsh Near infrared Nd:YAG, 810-830 Class 4 diode lasers. © 2012 Invisible. Strong melanin absorption makes retinal injury likely. Laser hazards database www.rli.com Reflections: Curved surface; Concave vs. No eyewear, wrong eyewear! Convex. Mirror-like “specular” reflections Alignment hazard when servicing All high power lasers can cause skin burns. Key points for laser safety At the under five watt level, the heat from the Never look into the direct or reflected beam laser beam will cause a flinch reaction before Wear the correct protective eyewear any serious damage occurs. With higher power Don’t leave the laser or light source running lasers, a burn can occur despite the flinch unattended reaction. These burns can be quite painful and Comply with safety signs and regulations take a considerable time to heal.

Laser Hazards: Eye UV light Dependant on wavelength UVA 280 to 400 nm: increased pigmentation. Visible or not? Blink reflex UVB: erythema (sunburn) Acute exposure can cause corneal or retinal UVC and UVB: Skin cancer and accelerated burns. skin photo-aging. Chronic exposure to excessive levels may cause corneal or lenticular opacities (cataracts) or Middle IR – cornea absorbs retinal injury. Regulatory framework Response of the Human Eye versus wavelength AS4173: Safe use of lasers in health care The eye focuses visible and near infrared light AS2211 series: Laser safety Normal focusing by the eye results in an IEC 60825-1 irradiance amplification of roughly 100,000 A 1 mW/cm2 beam entering the eye will result in 2 Jurisdictional radiation safety legislation, e.g. a 100 W/cm exposure at the retina. Qld, WA This will cause a thermal burn which destroys National harmonized radiation safety the retinal tissue. Since retinal tissue does not legislation regenerate, the damage is permanent. Possession licences Ocular transparency extends into the bear Use licences infrared. Melanin and Hb in retina will absorb Facility certification visible and near IR light Coverage for Class 4 lasers Future: Intense lights such as IPLs – above MPE (Maximum Permissible Exposure) = the certain parameters highest laser energy to which the eye or skin Impacts upon cosmetic medicine, Hair removal, can be exposed for a given laser wavelength Skin rejuvenation

NHZ (Nominal Hazard Zone) = area within which Hazard analysis the MPE is equalled or exceeded Primary hazard: Intense light Laser or IPL NOHD (Nominal Ocular Hazard Distance) = Direct or viewed through an instrument distance along the laser beam axis beyond Focussed or defocussed which is acceptable for eye exposure Reflected off surfaces Acute vs chronic effects MPE values vary by wavelength Eye and skin issues

Visible light esp. green: Frequency doubled Secondary hazards Device related/Direct Nd:YAG, DPSS KTP, argon ion lasers Electrical risks Very high photopic sensitivity so flash blindness Stray pump radiation 2

Laser medium hazards (dyes, compressed before powering the laser on. gases) 9. Check self-test routine completes Application related/Indirect correctly. Fire/ignition 10. Check aiming beam. Plume Procedural risks Servicing To ensure operation at it's optimum level, laser Flash Lamps: Stray radiation systems normally have preventive maintenance performed at regular (6 or 12 month intervals). Secondary Hazards During preventive maintenance the laser field Electrical : Most lasers except diode lasers service engineer will: utilize high voltages that can be lethal. Replace consumables such as HEPA filters or deionizing cartridges. Fire: High voltage circuits or flash lamps may Verify, system calibration and adjust as cause ignition. Flammable materials may be necessary. ignited by direct beams or specular reflections Inspect optics, clean, align as necessary. from high power continuous wave (CW) infrared Perform an all system test, and recommend lasers. repairs as necessary.

Chemical hazards: Dyes, solvents, gases Practical points for safety All windows, doorways, open portals, etc., of an Electrical safety enclosed facility should be covered or restricted The use of high voltages is perhaps the most to reduce any escaping laser beams below dangerous part of servicing, repairing, or appropriate ocular MPE level. working with lasers. While laser radiation can Disable lasers and intense lights when not in cause instant blindness, high voltages can use (remove the key) cause instant death! Adequate safeguards and Spectators and persons unnecessary to the safety practices include: procedure should be kept away. Insulation around exposed parts operating at high potentials; Interlocks on panels Equipment certification: IEC 60825-1 is applicable in Europe and the Fire risks: especially IR Lasers USA. It is recognized in Japan, Australia, Fire starting capability Canada and other countries. All Class 4 lasers are considered to be a fire It is now very much the worldwide laser safety hazard standard for laser manufacturers. Flammables: endotracheal tubes, surgical drapes, (dry) gauze, plastics, alcoholic solutions; Australia Clothing Therapeutics Goods Administration (TGA): Fire prevention: Fire extinguisher (dry powder Lasers (other than Class I) require TGA recommended). registration when used in patient care Use wet gauze as a beam stop. Be aware of special risks in operating theatre Europe environments such as anaesthetic tubes As part of the process of CE marking, all laser (and LED) products sold in Europe must be Basic Checklist certified to EN (IEC) 60825-1. 1. Check warning sign in place. 2. Get key. USA 3. Move laser to position. FDA Center for Devices and Radiological Health 4. Check mains electrical lead and foot Lasers require FDA registration (not LEDs) switch lead for damage. The regulation controlling laser products is 21 5. Check laser for any damage, especially CFR 1040.10 to the delivery system. 6. Close window blinds if needed. Since 2001, FDA has accepted IEC 7. Attach handpiece. classification and labelling. Manufacturers 8. Check protective glasses are in place selling their products in the USA have the choice 3

of using classification and labelling to IEC Skin may be burned at the higher levels of 60825-1 or 21 CFR 1040.10. In both cases the power output. products must be registered with the FDA. E.g. Low level laser unit used to promote wound healing Classification labels All lasers including class I except if laser is Class 4 lasers Class 1 even when all housings have been Power output >0.5 watts. stripped away. Visible OR invisible Cause eye damage. Class I laser Cause materials to burn on contact as well as No known biological hazard. skin and clothing to burn. The light is shielded from any possible viewing The reflected beam should be considered as by a person and the laser system is interlocked dangerous as the primary beam. to prevent the laser from being on when exposed. Hence the device produces no known Laser protective eyewear biological hazard. Polycarbonate, or Glass e.g. CD/DVD players, laser printers, enclosed Australian Standard AS2211 laser welders European PPE Directive under standard EN 207 CD, DVD, Blue Ray etc Role of Enclosures Major suppliers Issues with Window glass: Glass windows will Uvex not provide any significant protection for the Glendale (Zeiss) majority of visible and near infrared laser types Lasermet (e.g. argon ion, KTP, Nd:YAG, diode). However, Coherent glass does provide high attenuation at mid-far LaserVision infrared wavelengths, especially beyond 5 www.lasermet.com microns www.uvex-safety.com Glass may shatter if subjected to excessive www.glendale-laser.com heating from a concentrated beam. Polycarbonate Class 2 laser  Extremely lightweight Visible light  More comfortable to wear than heavier Power up to 1 milliwatt. glass filter eyewear, however, comfort is Blink reflex will limit ocular damage (0.25 also very dependent on the frame style. seconds)  Less expensive Eye damage could occur for greater times or if  May not be available in sufficiently high viewed through an optical instrument L number (OD). No known skin exposure hazard and no fire  Generally have a lower Visible Light hazard. Transmission (VLT) than glass E.g. small laser pointer  Will break if accidentally sat upon. NB Parallel beam from a laser pointer gives a very high retinal irradiance Glass  Offers higher protection levels than Class 3R laser (previously termed 3A) polycarbonate filters for the same laser. Power output between 1 milliwatt and 5 Often the L numbers are greater by 2 or milliwatts. 3 for the D marking (CW or average These lasers can produce spot blindness under power density rating), which means that the right conditions and other possible eye it can withstand 100 or 1000 times as injuries. much power density. No known skin hazard or fire hazards exist.  Higher Visible Light Transmission (VLT)

gives higher visibility Class 3B laser  More robust and less likely to break than Power output from 5 milliwatts to 500 milliwatts polycarbonate eyewear if accidentally (0.5 watts). sat upon. Definite eye hazard 4

 More expensive - 1200 nm (which includes the Nd:YAG  Heavier wavelength of 1064 nm),

Labelling of eyewear The maximum power or energy densities which Modern laser eyewear is normally certified to these glasses would withstand are 2 European Standard EN 207 “Personal eye- (D) CW 1 MW/m L5 2 protection. Filters and eye-protectors against (I) Long Pulse 500 J/m L5 2 laser radiation (laser eye-protectors)”. (R) Q Switched 5 kJ/m R L6 2 (M) Femtosecond 1.5 J/m L4 For the USA, Optical Density is usually the only protective information required. EN 207 takes account of both the Optical Wavelength specific eyewear for patients Density and the damage threshold of the Universal Opaque eyewear for patients eyewear. EN 207 breaks down the L number according to three wavelength ranges, 180-315 Protective eyewear for guardians and nm, 315-1400 nm and 1400-1,000,000 nm accompanying persons in the NOHD

OD means optical density – the higher the OD Laser hazard sign (remembering that it is a LOG scale in base 10), Laser hazard: starburst symbol the greater the protection. OD 4 means 1 part in 10,000 is transmitted Warning light OD 5 means 1 part in 100,000 is transmitted OD 6 means 1 part in a million is transmitted Class 4 laser systems MUST have:  key switch, e.g. For a 10 Watt laser with a 1 square  emergency off switch centimeter beam (power density 10 W/cm2), the  cover removal switches (interlocks), transmitted power density should be 0.0001  emission indicators, 2 W/cm (or 0.1 milliwatt per square centimeter).  mechanical shutters,  warning labels affixed to the laser. For pulsed lasers the eyewear must have both the correct I, R or M specification (depending on In Qld (and WA), Class IV lasers require the pulse length) and the correct D specification, licences for possession and use in patient care to ensure that it is suitable for the laser. as well as an approved Radiation Safety The D, I, R and M refer to CW or different pulse Protection Plan (RSPP). lengths as follows: One key on the ring D = Continuous Wave (CW) I = Pulsed with pulse length > 100 ns, 'Long Warning triangles: All lasers above Class 1 Pulse‘ Aperture labels: e.g. Class 3R, 3B, and 4 lasers R = Pulsed with pulse length > 1 ns and < 100 ns, 'Q-switched‘ Product information labels: All lasers exceeding M = Pulsed with pulse length < 1 ns, Class 1 'Femtosecond‘ Emission indicator Note that pulsed dental lasers such as Erbiums Warning signs on housings would all be >50 sec (“long pulse”), and thus Protective housing labels the “I” parameter is relevant, rather than R or M. On all panels or connections which when removed, opened or displaced will give access Example to radiation in excess of Class 1. Eyewear sold with an Nd:YAG laser was marked as follows: Interlocked housing labels DI 750 - 1200 L5 An all interlocked panels which when opened R 750 - 1200 L6 will give access to radiation in excess of Class 1 M 750 - 1200 L4 when the interlock is overridden.