1. MGH Wellman Center for Photomedicine Laser Safety
A laser can project more energy at a single wavelength within a narrow beam than can be obtained from more powerful conventional light sources

2. Electromagnetic Waves
Light is a small segment of the electromagnetic spectrum that extends from radio waves to g-rays. The only difference among the different waves is the wavelength (frequency).

3. Electromagnetic Waves (Light) Transport Energy
Radiant power or Radiant flux:
Total power emitted in the form of radiation (Watt)
Irradiance:
Power carried per unit area (W/cm2)
Radiant exposure:
Energy delivered per unit area (Joule/cm2)

4. LASER
Light Amplification by Stimulated Emission of Radiation
Differences between lasers and conventional light sources:
Laser Conventional sources
Monochromatic Many wavelengths
Collimated Emitted in many directions
Coherent Incoherent

5. Cross Section of a Common Laser
Ruby Laser

6. Lasers vs. Conventional Light Sources
LED (Light Emitting Diode)
Nd:YAG
Laser
Source: Google

7. Lasers vs. Conventional Light Sources( a
Apparent visual angle
laser source
A collimated beam can be focused to a
small spot on the retina
Conventional light source
info.tuwien.ac.at/iflt/safety/section1/s1_body.htm

8. Light-Tissue Interactions Tissue Absorbers

9. Light-Tissue Interactions Selective Photothermolysis
Medical procedures can only be initiated by absorption of light
Effects can be controlled by choosing the appropriate wavelength

10. Widely-Used Lasers Wavelength of Operation
Source: Shore Laser Center

11. Standards for Safe Use of Lasers Federal and State Agencies
OSHA
FDA (Center for Devices and Radiological Health)
The Commonwealth of Massachusetts:
Department of Public Health

12. Laser Beam Hazards
Eye hazard
Skin hazard

13. Laser Hazard Classification Accessible Emission Limit (AEL)
Lasers and laser systems are classified on the basis of the laser radiation accessible outside the laser during the intended use
and to which the human eye or skin is possible to be exposed

14. Laser Hazard Classification
Class 1 laser:
Low power; Considered safe
Class 2 laser:
Eye protection afforded by the eye blink response
Class 3 laser:
Medium power; Hazard to the eye from direct exposure
Class 4 laser:
High power; Hazard to the eye and skin from direct and reflected exposure; Fire hazard

15. Beam Hazards Eye Hazard
Cornea/lens hazard: nm and ,600 nm
Retinal hazard region: nm
Eye entering the eye is focused. The irradiance on the retina can be increased as much as 100,000
One central fovea laser hit can cause blindness

16. Eye Injury Nd:YAG (1064 nm) - Permanent damage
Individual saw a white flash, heard a click, then immediately a dark spot in visual field (

17. How do you know if you have an eye injury?
Exposure to infrared high-power laser causes a burning pain to the cornea or sclera
Exposure to visible lasers causes a bright color flash of the emitted wavelength and an after image of a complementary color
Exposure to short pulsed infrared lasers may go undetected or may cause a popping sound followed by visual disorientation

18. Beam Hazards Skin Hazard
Visible and infrared high-power lasers can cause permanent skin damage or damage to underlying organs
Examples of skin response to laser exposure:
Mild to severe reddening
Blisters and charring
De-pigmentation
Ulceration
Scarring

19. Maximum Permissible Exposure MPE
Irradiance (Radiant Exposure) to which a person can be exposed without hazard to eye or skin
MPE values may cause discomfort

20. Maximum Permissible Exposure
The MPE depends on the following parameters:
Laser wavelength
Duration of exposure
The MPE for eye exposure is much lower than the MPE for skin

21. Warning Signs Example: Class 2 Laser

22. Warning Signs Example: Class 4 Laser

23. Protective Eyewear Goggles

24. Protective Eyewear

25. Protective Eyewear
The protection wavelength(s) and the corresponding attenuation are scribed on the eyewear
The attenuation is given in Optical Density (OD). An OD of 4 means that the irradiance of the beam passing through the eyewear is attenuated by 10,000 times

26. Non-Beam Hazards
Fire:
Ignition of materials can occur from direct or intense reflected or scattered beams
Electrical:
Most deaths caused by lasers are caused by electrocution. Laser capacitors can retain high energy charges even when the power is off

27. Non-Beam Hazards
Laser-generated airborne contaminants:
Chemical fumes, aerosols of biological contaminants including viable viruses and other biohazards can and do exist in the laser plume
Chemical:
Laser dyes, solvents and gases used may be toxic, explosive or carcinogens

28. Credentialing Procedure Certification to Operate a Particular Type of Laser
It is the policy of the Massachusetts General Hospital that all medical staff utilizing a laser for any procedure must be credentialed. The credentialing process must be followed for each type (wavelength) of laser for which privileges are requested

29. Credentialing Procedure Certification to Operate a Particular Type of Laser
Attendance at an approved didactic course
Supervised operation with the particular laser in at least 3 patients.
For new or experimental lasers, the laser manufacturer can provide hands-on instruction
Application for laser credentials to Laser Safety Committee
A baseline fundoscopic eye examination that notes apparent pre-existing abnormalities is recommended