Laser Bioeffects Defence IQ s DEW 09

2. AFRL Directed Energy Bioeffects Linkages Joint Service Collaboration on Laser, RFR Bioeffects Close collaboration with DEW developers Health & Safety Standard Setting Communities Executive Agent for Non-Lethal Weapons - USMC International: UK, NATO, TTCP, WHO Professional Societies: Members, Leaders, Fellows

3. Policy Acceptability Press Public DoD decision-makers Health & Safety Counter-Personnel DEWs development relies heavily on bioeffects

4.

5. Ultrashort Laser Accident On August 16, 1994 a laser accident occurred in our laboratory. A researcher working on the alignment of the compressor for a femtosecond Ti:Sapphire laser system was struck in the eye by a portion of the spectrally dispersed laser beam. The resulting split-second exposure to a 1-kHz train of broadband 20-ps pulses of at most 50 micro Joule centered at 800 nm, caused irreversible, permanent retinal damage in the eye. The person in question lost vision over a thin strip right in the middle of the central vision. While the brain may adapt to correct for this loss of vision, the injury itself cannot be remedied.

6. Define �Safety� for System Occupational Standards: Laser communities has established their safe exposure limits � maximum permissible exposure (MPE) - with safety margin �built in� Scientific Basis: Minimal visible lesion data Mechanisms of Action DEW may not be �safe� as defined by a safety standard!

7. Determine Bioeffects (1) Ex-Vivo Modeling 

8. Determine Bioeffects (2) Human or Animal studies investigating effectiveness and injury Effectiveness Assessment of Laser Bioeffects Safety Margin Evaluated Mechanism(s) for Action Initiate Assessment for CONOP Effectiveness

9. Example- In Vitro Retinal Cells

11. Laser bioeffect trends

12. Laser Wavelength Regimes Ultraviolet- C (UV-C) 0.180- 0.280 �m UV-B 0.280- 0.315 �m UV-A 0.315 - 0.400 �m Visible 0.400 � 0.700 �m Infrared- A (IR-A) 0.700- 1.4 �m IR 1.4 �m � 1 mm 400 nm = 0.4 �m = 750 THz (vacuum) 1,000 nm = 1.0 �m = 300 THz 10,000 nm = 10.0 �m = 30 THz

13. Wavelength Regimes of Laser Bioeffects EYE Corneal Burn Cataract Photo-retinitis Retinal Burns Corneal Burn SKIN Erythema Thermal Skin Burns

14. Laser-Bioeffects of the Skin

15. Structure of the Skin

16. Light Absorption in the Skin

19. Not Only Absorption

25. Retinal Laser Bioeffects

26. The Retina

27. Traditional Thermal Understanding

28. Thermal Damage - Short Pulse

29. Single Pulse MPE and MVL

30. Contributors to Retinal Damage Threshold

31. Chromatic Aberration in the Eye

32. Focal Plane Shifts With Wavelength

33. Spot Size on Retina with Wavelength

34. MVL and MPE versus Wavelength

35. Spot Size MVL Comparison

36. Multiple Pulse Trends

37. Summary of MVL Trends Single Exposure Pulse width: As Pulse Duration Decreases, MVL TIE Decreases Wavelength: Longer Wavelengths Produce Larger Spots and Absorb Less in RPE and Have Higher MVL TIE Macular/Paramacular: Ratio of 1.6 Consistent With Previous Studies Retinal Spot Size: Increase Spot Size Decrease Retinal Radiant Exposure Multiple Pulse: n-1/4 (BUT Ultrashort Shows Decrease in MVL Between 1 - 10 Pulses, No Drop for 10 - 10,000 Pulses)

38. Retinal Lesion Mechanisms for Damage

39. Single Pulse MPE (2007) and MVL

40. Laser Bioeffects Summary Occupational Safety Standard Follows Biological Response Retinal Damage from Laser Exposure Single Pulse (Pulse Width) Wavelength Retinal Spot Size Number of Pulses Complex Issues Related to Laser-Tissue Interaction for many pulse parameters

41. Questions