Core of Knowledge inSafe Use of Lasers & IPLsin healthcareMr John Saunderson, Consultant Medical Physicist

Why laser core of knowledge?

Core of Knowledge syllabusUnderstand 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

LightAmplification by theStimulated Emission ofRadiation

Electromagnetic Spectrum

740-620 nm - red620-585 nm - orange585-575 nm - yellow575-500 nm - green500-445 nm - blue445-425 nm - indigo425-390 nm - violet

Light Sources & LasersSpontaneous emissionfilament lampfluorescent lampneon lightsmost LEDsfirefluorescenceIPL (intense pulsed light source)Stimulated emissionlaser

Spontaneous emissionAtom

Energy(e.g. electrical current through filament, or electrical discharge through a fluorescent tube, or UV light on a fluorescent material)

Excited atom

Spontaneous emissionAtomPhoton emittedAny direction.

Spontaneous emission

Stimulated emissionAtom

Energy(e.g. electrical discharge, flash lamp, electrical current)

Excited atom

Stimulated emissionIncoming photon(correct wavelength)

Stimulated emissionTwo photons emittedIF correct wavelength then STIMULATED EMISSIONSame wavelength and same direction

Incoming photon(wrong wavelength)

Scattered photon

LASERTube filled with laser medium (e.g. helium-neon gas for HeNe laser)

LASEREnergy(e.g. electrical discharge, flash lamp, electrical current)

LASERPopulation Inversion or pumpingEnergy(e.g. electrical discharge, flash lamp, electrical current)

LASERSpontaneous emission takes place

LASERSome photons will cause stimulated emission

LASERMirrors at either end reflect those photons travelling along tube

LASERMore simulated emission in same direction along the tube

LASERAmplification

One mirror (output coupler) leaky allowing laser beam to emerge All photons same wavelength (colour)All photons travelling in same directionCan produced extremely short pulses of high energy

Non-coherent vs laser light sourceExtended vs point source 40 Watt incandescent bulb ~2% efficient 0.8 W = 800 mW light energy1 mW laser pointer 800 x less light energy emitted than 40 W bulb

Extended vs point source 800 mW @ 100 cm Irradiance, E = 800 (4 x 1002) E = 0.006 mW/cm2Similar in all directions1 mW pointer, 0.15cm beam diameterIn most direction, E = 0 all distancesIn beam, E = 1 mW ( x 0.152)E = 14 mW/cm2i.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 laserx 91,000,000 @ 1 m

(Note, other effects make this even higher on retina)

Non-coherent vs laser light sourceChromatic AberrationLasers are monochromatic (single wavelength) so minimal chromatic aberration

Non-coherent vs laser light sourceExtended vs Point SourcesObject / SourceImageLens

ImageObject / SourceLens1

Extended source

ImageObject / SourceLens2

Distance objectImage Object / SourceLens

Distance objectImageObject / SourceParallel 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 pointerE(skin) = 14 mW/cm2 (from earlier)1.5 mm beam focussed to 20 microns (1.5/0.020)2 = 5,600 power densityE(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 reflectionsIntrabeamdirectly shone into eyeif focussed by eye, 20 m spot on retina

Intrabeam ViewingIf beam larger than pupil only proportion of beam will be focussed on retinaIf magnifying glass etc used a greater proportion will be focused on retina

Intrabeam ViewingIf beam smaller than pupil diameter, magnifying glass make no difference to retina (would to skin)

Specular reflection= mirror-like reflectionPotentially same hazard as direct intrabeam viewing

Diffuse Reflectione.g. seeing laser spot on wallNot a point source, so not focussed to 20 mMay still be hazardous

Lenses, mirrors & fibresAll produce a divergent laser beamLensMirrorOptical fibre

Lenses, mirrors & fibresConcave mirrors and convex lensesfocal spot - high irradiancebeam then gets broaderif bigger than pupil then hazard reduces with distanceOptical fibrediverges from exiting fibreif bigger than pupil then hazard reduces with distance

Video 1

Types of Medical Laser

UV < 390 390 > visible > 740 740 < infrared

Chart1

01.500

7.950.850.40.4

6.550.80.450.45

4.950.450.60.6

4.50.20.750.75

4.650.150.90.9

4.73011

4.351.37.21.3

4.051.37.21.3

5.751.956.831.95

7.42.36.60

5.62.66.42.6

4.92.96.170

5.636.13

5.43.1563.15

5.753.35.953.3

43.55.70

2.105.553.75

1.850.15.373.95

1.850.25.374

20.855.254.2

2.120.9550

2.280.754.754.5

2.51.44.40

2.62.44.34.9

2.6834.10

2.352.23.85.3

2.232.43.785.4

1.93.73.55.7

2.873.75.95.9

1.8556.26.2

1.876.16.46.4

1.955.16.656.65

6.85.16.86.8

75.777

7.37.47.30

7.95.757.97.9

8.57.758.58.5

8.79.88.70

97.799

9.157.39.159.15

9.47.859.49.4

9.67.79.60

108.31010

10.1810.10

10.38.510.310.3

10.65910.6510.65

10.89.7510.80

119.11111

11.39.111.30

11.79.1511.70

12.29.212.20

Nd:YAG

CO2

Ho:YAG

Ar

200

400

1000

5000

10000

water

HbO2

melanin

HbO2

H2O

Melanin

ticks

Wavelength (nm)

Absorption (log scale)

Sheet1

xyxxnormynorm

01.5131.6227766017200.2050.0061595271

10101274.44252040580.001

3.806309.57344480191663.72097420870.001

40.2100001.5848931925706.93720400720.0012743038

4.20.8515848.93192461117.0794578438752.96733089580.0028016261

4.30.9519952.62314968888.9125093813777.09440441760.0031626175

4.50.7531622.77660168385.6234132519827.69261008150.0024818395

4.81.463095.734448019325.1188643151909.83370549210.0054564588

531000001000969.07483847250.0379397737

5.32.2199526.231496888158.48931924611065.24685668010.0143880788

5.73.7501187.2336272735011.87233627271208.4838563010.0886237606

63.710000005011.87233627271328.41508020410.0886237606

6.251584893.192461121000001414.91090240160.4283754369

6.46.12511886.431509591258925.411794171507.03864444781.6248974742

6.65.13981071.70553498125892.5411794171605.16501216030.4835718946

6.85.16309573.44480194125892.5411794171709.6805883220.4835718946

75.710000000501187.2336272731821.00138735961.0006449289

7.37.419952623.149688825118864.31509592001.71950285347.8541709431

7.95.7579432823.4724284562341.325190352418.73956267151.0631590597

8.57.75316227766.01683856234132.51903492922.637794003112.0040575406

8.79.8501187233.6272726309573444.801953112.9367169413144.0045247587

97.7100000000050118723.36272733421.867869351211.2982146879

9.157.31412537544.6227619952623.14968883587.64702423846.9576705068

9.47.852511886431.5095970794578.43841383881.984774302813.5507882765

9.67.73981071705.5349850118723.36272734134.748740788211.2982146879

108.310000000000199526231.4968884690.722222524323.3791528404

10.1812589254117.94171000000004841.025423326316.2524671362

10.38.519952623149.6889316227766.0168385156.234487503129.7921435955

10.65944668359215.096510000000005758.036681007354.611512983

10.89.7563095734448.01955623413251.903516036.9961532115135.5370074874

119.11000000000001258925411.794176430.077317116161.6482424703

12.59.23162277660168.381584893192.4611110320.02892244669.5916591958

&A

Page &P

Sheet1

0.0061595271

0.001

0.001

0.0012743038

0.0028016261

0.0031626175

0.0024818395

0.0054564588

0.0379397737

0.0143880788

0.0886237606

0.0886237606

0.4283754369

1.6248974742

0.4835718946

0.4835718946

1.0006449289

7.8541709431

1.0631590597

12.0040575406

144.0045247587

11.2982146879

6.9576705068

13.5507882765

11.2982146879

23.3791528404

16.2524671362

29.7921435955

54.611512983

135.5370074874

61.6482424703

69.5916591958

Wavelength (nm)

Relative absorption in water

Sheet1 (2)

xyxxnormynorm

01.5131.6227766017200.2050.0061595271

10101274.44252040580.001

3.806309.57344480191663.72097420870.001

40.2100001.5848931925706.93720400720.0012743038

4.20.8515848.93192461117.0794578438752.96733089580.0028016261

4.30.9519952.62314968888.9125093813777.09440441760.0031626175

4.50.7531622.77660168385.6234132519827.69261008150.0024818395

4.81.463095.734448019325.1188643151909.83370549210.0054564588

531000001000969.07483847250.0379397737

5.32.2199526.231496888158.48931924611065.24685668010.0143880788

5.73.7501187.2336272735011.87233627271208.4838563010.0886237606

63.710000005011.87233627271328.41508020410.0886237606

6.251584893.192461121000001414.91090240160.4283754369

6.46.12511886.431509591258925.411794171507.03864444781.6248974742

6.65.13981071.70553498125892.5411794171605.16501216030.4835718946

6.85.16309573.44480194125892.5411794171709.6805883220.4835718946

75.710000000501187.2336272731821.00138735961.0006449289

7.37.419952623.149688825118864.31509592001.71950285347.8541709431

7.95.7579432823.4724284562341.325190352418.73956267151.0631590597

8.57.75316227766.01683856234132.51903492922.637794003112.0040575406

8.79.8501187233.6272726309573444.801953112.9367169413144.0045247587

97.7100000000050118723.36272733421.867869351211.2982146879

9.157.31412537544.6227619952623.14968883587.64702423846.9576705068

9.47.852511886431.5095970794578.43841383881.984774302813.5507882765

9.67.73981071705.5349850118723.36272734134.748740788211.2982146879

108.310000000000199526231.4968884690.722222524323.3791528404

10.1812589254117.94171000000004841.025423326316.2524671362

10.38.519952623149.6889316227766.0168385156.234487503129.7921435955

10.65944668359215.096510000000005758.036681007354.611512983

10.89.7563095734448.01955623413251.903516036.9961532115135.5370074874

119.11000000000001258925411.794176430.077317116161.6482424703

12.59.23162277660168.381584893192.4611110320.02892244669.5916591958

&A

Page &P

Sheet1 (2)

0.0061595271

0.001

0.001

0.0012743038

0.0028016261

0.0031626175

0.0024818395

0.0054564588

0.0379397737

0.0143880788

0.0886237606

0.0886237606

0.4283754369

1.6248974742

0.4835718946

0.4835718946

1.0006449289

7.8541709431

1.0631590597

12.0040575406

144.0045247587

11.2982146879

6.9576705068

13.5507882765

11.2982146879

23.3791528404

16.2524671362

29.7921435955

54.611512983

135.5370074874

61.6482424703

69.5916591958

Wavelength (nm)

Relative absorption in water

powerpoint version

xyxxnormynorm

01.5131.6227766017200.2050.0061595271

10101274.44252040580.001

3.806309.57344480191663.72097420870.001

40.2100001.5848931925706.93720400720.0012743038

4.20.8515848.93192461117.0794578438752.96733089580.0028016261

4.30.9519952.62314968888.9125093813777.09440441760.0031626175

4.50.7531622.77660168385.6234132519827.69261008150.0024818395

4.81.463095.734448019325.1188643151909.83370549210.0054564588

531000001000969.07483847250.0379397737

5.32.2199526.231496888158.48931924611065.24685668010.0143880788

5.73.7501187.2336272735011.87233627271208.4838563010.0886237606

63.710000005011.87233627271328.41508020410.0886237606

6.251584893.192461121000001414.91090240160.4283754369

6.46.12511886.431509591258925.411794171507.03864444781.6248974742

6.65.13981071.70553498125892.5411794171605.16501216030.4835718946

6.85.16309573.44480194125892.5411794171709.6805883220.4835718946

75.710000000501187.2336272731821.00138735961.0006449289

7.37.419952623.149688825118864.31509592001.71950285347.8541709431

7.95.7579432823.4724284562341.325190352418.73956267151.0631590597

8.57.75316227766.01683856234132.51903492922.637794003112.0040575406

8.79.8501187233.6272726309573444.801953112.9367169413144.0045247587

97.7100000000050118723.36272733421.867869351211.2982146879

9.157.31412537544.6227619952623.14968883587.64702423846.9576705068

9.47.852511886431.5095970794578.43841383881.984774302813.5507882765

9.67.73981071705.5349850118723.36272734134.748740788211.2982146879

108.310000000000199526231.4968884690.722222524323.3791528404

10.1812589254117.94171000000004841.025423326316.2524671362

10.38.519952623149.6889316227766.0168385156.234487503129.7921435955

10.65944668359215.096510000000005758.036681007354.611512983

10.89.7563095734448.01955623413251.903516036.9961532115135.5370074874

119.11000000000001258925411.794176430.077317116161.6482424703

12.59.23162277660168.381584893192.4611110320.02892244669.5916591958

&A

Page &P

powerpoint version

0.0061595271

0.001

0.001

0.0012743038

0.0028016261

0.0031626175

0.0024818395

0.0054564588

0.0379397737

0.0143880788

0.0886237606

0.0886237606

0.4283754369

1.6248974742

0.4835718946

0.4835718946

1.0006449289

7.8541709431

1.0631590597

12.0040575406

144.0045247587

11.2982146879

6.9576705068

13.5507882765

11.2982146879

23.3791528404

16.2524671362

29.7921435955

54.611512983

135.5370074874

61.6482424703

69.5916591958

Wavelength (nm)

Relative absorption in water

Sheet1 (4)

xyxxnormynorm

01.5131.6227766017200.2050.0061595271

10101274.44252040580.001

3.806309.57344480191663.72097420870.001

40.2100001.5848931925706.93720400720.0012743038

4.20.8515848.93192461117.0794578438752.96733089580.0028016261

4.30.9519952.62314968888.9125093813777.09440441760.0031626175

4.50.7531622.77660168385.6234132519827.69261008150.0024818395

4.81.463095.734448019325.1188643151909.83370549210.0054564588

531000001000969.07483847250.0379397737

5.32.2199526.231496888158.48931924611065.24685668010.0143880788

5.73.7501187.2336272735011.87233627271208.4838563010.0886237606

63.710000005011.87233627271328.41508020410.0886237606

6.251584893.192461121000001414.91090240160.4283754369

6.46.12511886.431509591258925.411794171507.03864444781.6248974742

6.65.13981071.70553498125892.5411794171605.16501216030.4835718946

6.85.16309573.44480194125892.5411794171709.6805883220.4835718946

75.710000000501187.2336272731821.00138735961.0006449289

7.37.419952623.149688825118864.31509592001.71950285347.8541709431

7.95.7579432823.4724284562341.325190352418.73956267151.0631590597

8.57.75316227766.01683856234132.51903492922.637794003112.0040575406

8.79.8501187233.6272726309573444.801953112.9367169413144.0045247587

97.7100000000050118723.36272733421.867869351211.2982146879

9.157.31412537544.6227619952623.14968883587.64702423846.9576705068

9.47.852511886431.5095970794578.43841383881.984774302813.5507882765

9.67.73981071705.5349850118723.36272734134.748740788211.2982146879

108.310000000000199526231.4968884690.722222524323.3791528404

10.1812589254117.94171000000004841.025423326316.2524671362

10.38.519952623149.6889316227766.0168385156.234487503129.7921435955

10.65944668359215.096510000000005758.036681007354.611512983

10.89.7563095734448.01955623413251.903516036.9961532115135.5370074874

119.11000000000001258925411.794176430.077317116161.6482424703

12.59.23162277660168.381584893192.4611110320.02892244669.5916591958

&A

Page &P

Sheet2

00.001

1.90.01

3.750.1

5.51

7.2510

9.1100

11.21000

&A

Page &P

Sheet2

&A

Page &P

Sheet3

0200

2.15400

3.4600

5.11000

7.32000

9.44000

11.78000

&A

Page &P

Sheet3

&A

Page &P

combined

xMelaninticks

01.5

0.47.950.85

0.456.550.8

0.64.950.45

0.754.50.2

0.94.650.15

14.730

1.34.357.2

1.34.057.2

1.955.756.83

2.37.46.60

2.65.66.4

2.94.96.170

35.66.1

3.155.46

3.35.755.95

3.545.70

3.752.105.55

3.951.850.15.37

41.850.25.37

4.220.855.25

4.32.120.9550

4.52.280.754.75

4.82.51.44.40

4.92.62.44.3

5.052.6834.10

5.32.352.23.8

5.42.232.43.78

5.71.93.73.5

5.92.873.7

6.21.855

6.41.876.1

6.651.955.1

6.85.1

75.7

7.37.40

7.95.75

8.57.75

8.79.80

97.7

9.157.3

9.47.85

9.67.70

108.3

10.180

10.38.5

10.659

10.89.750

119.1

11.39.10

11.79.150

12.29.20

&A

Page &P

combined

01.500

7.950.850.40.4

6.550.80.450.45

4.950.450.60.6

4.50.20.750.75

4.650.150.90.9

4.73011

4.351.37.21.3

4.051.37.21.3

5.751.956.831.95

7.42.36.60

5.62.66.42.6

4.92.96.170

5.636.13

5.43.1563.15

5.753.35.953.3

43.55.70

2.105.553.75

1.850.15.373.95

1.850.25.374

20.855.254.2

2.120.9550

2.280.754.754.5

2.51.44.40

2.62.44.34.9

2.6834.10

2.352.23.85.3

2.232.43.785.4

1.93.73.55.7

2.873.75.95.9

1.8556.26.2

1.876.16.46.4

1.955.16.656.65

6.85.16.86.8

75.777

7.37.47.30

7.95.757.97.9

8.57.758.58.5

8.79.88.70

97.799

9.157.39.159.15

9.47.859.49.4

9.67.79.60

108.31010

10.1810.10

10.38.510.310.3

10.65910.6510.65

10.89.7510.80

119.11111

11.39.111.30

11.79.1511.70

12.29.212.20

&A

Page &P

200

400

600

1000

2000

4000

HbO2

H2O

Melanin

ticks

Wavelength / nm

Relative Absorption Coefficients (log scale)

combined (2)

xMelaninticks

01.5

0.47.950.85

0.456.550.8

0.64.950.45

0.754.50.2

0.94.650.15

14.730

1.34.357.2

1.34.057.2

1.955.756.83

2.37.46.60

2.65.66.4

2.94.96.170

35.66.1

3.155.46

3.35.755.95

3.545.70

3.752.105.55

3.951.850.15.37

41.850.25.37

4.220.855.25

4.32.120.9550

4.52.280.754.75

4.82.51.44.40

4.92.62.44.3

5.052.6834.10

5.32.352.23.8

5.42.232.43.78

5.71.93.73.5

5.92.873.7

6.21.855

6.41.876.1

6.651.955.1

6.85.1

75.7

7.37.40

7.95.75

8.57.75

8.79.80

97.7

9.157.3

9.47.85

9.67.70

108.3

10.180

10.38.5

10.659

10.89.750

119.1

11.39.10

11.79.150

12.29.20

&A

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combined (2)

01.500

7.950.850.40.4

6.550.80.450.45

4.950.450.60.6

4.50.20.750.75

4.650.150.90.9

4.73011

4.351.37.21.3

4.051.37.21.3

5.751.956.831.95

7.42.36.60

5.62.66.42.6

4.92.96.170

5.636.13

5.43.1563.15

5.753.35.953.3

43.55.70

2.105.553.75

1.850.15.373.95

1.850.25.374

20.855.254.2

2.120.9550

2.280.754.754.5

2.51.44.40

2.62.44.34.9

2.6834.10

2.352.23.85.3

2.232.43.785.4

1.93.73.55.7

2.873.75.95.9

1.8556.26.2

1.876.16.46.4

1.955.16.656.65

6.85.16.86.8

75.777

7.37.47.30

7.95.757.97.9

8.57.758.58.5

8.79.88.70

97.799

9.157.39.159.15

9.47.859.49.4

9.67.79.60

108.31010

10.1810.10

10.38.510.310.3

10.65910.6510.65

10.89.7510.80

119.11111

11.39.111.30

11.79.1511.70

12.29.212.20

&C&"Comic Sans MS,Regular"&28Horses for Courses

Page &P

Nd:YAG

CO2

Ho:YAG

Ar

200

400

1000

5000

10000

water

HbO2

melanin

HbO2

H2O

Melanin

ticks

Wavelength (nm)

Absorption (log scale)

Sheet5

&A

Page &P

Sheet6

&A

Page &P

Sheet7

&A

Page &P

Sheet8

&A

Page &P

Sheet9

&A

Page &P

Sheet10

&A

Page &P

Sheet11

&A

Page &P

Sheet12

&A

Page &P

Sheet13

&A

Page &P

Sheet14

&A

Page &P

Sheet15

&A

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Sheet16

&A

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Taken from A Non-Binding Guide to the Artificial Optical Radiation Directive 2006/25/EC, Radiation Protection Division, Health Protection Agencyhttp://www.hse.gov.uk/radiation/nonionising/aor-guide.pdf

CO2 laserIRAIRBIRCNd:YAG laser

CO2 laserNd:YAG laserArgon laserVIBGYORKTP-Nd:YAG - frequency doubling to 532 nm (green)

UV < 390 390 > visible > 740 740 < infrared

Chart1

01.500

7.950.850.40.4

6.550.80.450.45

4.950.450.60.6

4.50.20.750.75

4.650.150.90.9

4.73011

4.351.37.21.3

4.051.37.21.3

5.751.956.831.95

7.42.36.60

5.62.66.42.6

4.92.96.170

5.636.13

5.43.1563.15

5.753.35.953.3

43.55.70

2.105.553.75

1.850.15.373.95

1.850.25.374

20.855.254.2

2.120.9550

2.280.754.754.5

2.51.44.40

2.62.44.34.9

2.6834.10

2.352.23.85.3

2.232.43.785.4

1.93.73.55.7

2.873.75.95.9

1.8556.26.2

1.876.16.46.4

1.955.16.656.65

6.85.16.86.8

75.777

7.37.47.30

7.95.757.97.9

8.57.758.58.5

8.79.88.70

97.799

9.157.39.159.15

9.47.859.49.4

9.67.79.60

108.31010

10.1810.10

10.38.510.310.3

10.65910.6510.65

10.89.7510.80

119.11111

11.39.111.30

11.79.1511.70

12.29.212.20

Nd:YAG

CO2

Ho:YAG

Ar

200

400

1000

5000

10000

water

HbO2

melanin

HbO2

H2O

Melanin

ticks

Wavelength (nm)

Absorption (log scale)

Sheet1

xyxxnormynorm

01.5131.6227766017200.2050.0061595271

10101274.44252040580.001

3.806309.57344480191663.72097420870.001

40.2100001.5848931925706.93720400720.0012743038

4.20.8515848.93192461117.0794578438752.96733089580.0028016261

4.30.9519952.62314968888.9125093813777.09440441760.0031626175

4.50.7531622.77660168385.6234132519827.69261008150.0024818395

4.81.463095.734448019325.1188643151909.83370549210.0054564588

531000001000969.07483847250.0379397737

5.32.2199526.231496888158.48931924611065.24685668010.0143880788

5.73.7501187.2336272735011.87233627271208.4838563010.0886237606

63.710000005011.87233627271328.41508020410.0886237606

6.251584893.192461121000001414.91090240160.4283754369

6.46.12511886.431509591258925.411794171507.03864444781.6248974742

6.65.13981071.70553498125892.5411794171605.16501216030.4835718946

6.85.16309573.44480194125892.5411794171709.6805883220.4835718946

75.710000000501187.2336272731821.00138735961.0006449289

7.37.419952623.149688825118864.31509592001.71950285347.8541709431

7.95.7579432823.4724284562341.325190352418.73956267151.0631590597

8.57.75316227766.01683856234132.51903492922.637794003112.0040575406

8.79.8501187233.6272726309573444.801953112.9367169413144.0045247587

97.7100000000050118723.36272733421.867869351211.2982146879

9.157.31412537544.6227619952623.14968883587.64702423846.9576705068

9.47.852511886431.5095970794578.43841383881.984774302813.5507882765

9.67.73981071705.5349850118723.36272734134.748740788211.2982146879

108.310000000000199526231.4968884690.722222524323.3791528404

10.1812589254117.94171000000004841.025423326316.2524671362

10.38.519952623149.6889316227766.0168385156.234487503129.7921435955

10.65944668359215.096510000000005758.036681007354.611512983

10.89.7563095734448.01955623413251.903516036.9961532115135.5370074874

119.11000000000001258925411.794176430.077317116161.6482424703

12.59.23162277660168.381584893192.4611110320.02892244669.5916591958

&A

Page &P

Sheet1

0.0061595271

0.001

0.001

0.0012743038

0.0028016261

0.0031626175

0.0024818395

0.0054564588

0.0379397737

0.0143880788

0.0886237606

0.0886237606

0.4283754369

1.6248974742

0.4835718946

0.4835718946

1.0006449289

7.8541709431

1.0631590597

12.0040575406

144.0045247587

11.2982146879

6.9576705068

13.5507882765

11.2982146879

23.3791528404

16.2524671362

29.7921435955

54.611512983

135.5370074874

61.6482424703

69.5916591958

Wavelength (nm)

Relative absorption in water

Sheet1 (2)

xyxxnormynorm

01.5131.6227766017200.2050.0061595271

10101274.44252040580.001

3.806309.57344480191663.72097420870.001

40.2100001.5848931925706.93720400720.0012743038

4.20.8515848.93192461117.0794578438752.96733089580.0028016261

4.30.9519952.62314968888.9125093813777.09440441760.0031626175

4.50.7531622.77660168385.6234132519827.69261008150.0024818395

4.81.463095.734448019325.1188643151909.83370549210.0054564588

531000001000969.07483847250.0379397737

5.32.2199526.231496888158.48931924611065.24685668010.0143880788

5.73.7501187.2336272735011.87233627271208.4838563010.0886237606

63.710000005011.87233627271328.41508020410.0886237606

6.251584893.192461121000001414.91090240160.4283754369

6.46.12511886.431509591258925.411794171507.03864444781.6248974742

6.65.13981071.70553498125892.5411794171605.16501216030.4835718946

6.85.16309573.44480194125892.5411794171709.6805883220.4835718946

75.710000000501187.2336272731821.00138735961.0006449289

7.37.419952623.149688825118864.31509592001.71950285347.8541709431

7.95.7579432823.4724284562341.325190352418.73956267151.0631590597

8.57.75316227766.01683856234132.51903492922.637794003112.0040575406

8.79.8501187233.6272726309573444.801953112.9367169413144.0045247587

97.7100000000050118723.36272733421.867869351211.2982146879

9.157.31412537544.6227619952623.14968883587.64702423846.9576705068

9.47.852511886431.5095970794578.43841383881.984774302813.5507882765

9.67.73981071705.5349850118723.36272734134.748740788211.2982146879

108.310000000000199526231.4968884690.722222524323.3791528404

10.1812589254117.94171000000004841.025423326316.2524671362

10.38.519952623149.6889316227766.0168385156.234487503129.7921435955

10.65944668359215.096510000000005758.036681007354.611512983

10.89.7563095734448.01955623413251.903516036.9961532115135.5370074874

119.11000000000001258925411.794176430.077317116161.6482424703

12.59.23162277660168.381584893192.4611110320.02892244669.5916591958

&A

Page &P

Sheet1 (2)

0.0061595271

0.001

0.001

0.0012743038

0.0028016261

0.0031626175

0.0024818395

0.0054564588

0.0379397737

0.0143880788

0.0886237606

0.0886237606

0.4283754369

1.6248974742

0.4835718946

0.4835718946

1.0006449289

7.8541709431

1.0631590597

12.0040575406

144.0045247587

11.2982146879

6.9576705068

13.5507882765

11.2982146879

23.3791528404

16.2524671362

29.7921435955

54.611512983

135.5370074874

61.6482424703

69.5916591958

Wavelength (nm)

Relative absorption in water

powerpoint version

xyxxnormynorm

01.5131.6227766017200.2050.0061595271

10101274.44252040580.001

3.806309.57344480191663.72097420870.001

40.2100001.5848931925706.93720400720.0012743038

4.20.8515848.93192461117.0794578438752.96733089580.0028016261

4.30.9519952.62314968888.9125093813777.09440441760.0031626175

4.50.7531622.77660168385.6234132519827.69261008150.0024818395

4.81.463095.734448019325.1188643151909.83370549210.0054564588

531000001000969.07483847250.0379397737

5.32.2199526.231496888158.48931924611065.24685668010.0143880788

5.73.7501187.2336272735011.87233627271208.4838563010.0886237606

63.710000005011.87233627271328.41508020410.0886237606

6.251584893.192461121000001414.91090240160.4283754369

6.46.12511886.431509591258925.411794171507.03864444781.6248974742

6.65.13981071.70553498125892.5411794171605.16501216030.4835718946

6.85.16309573.44480194125892.5411794171709.6805883220.4835718946

75.710000000501187.2336272731821.00138735961.0006449289

7.37.419952623.149688825118864.31509592001.71950285347.8541709431

7.95.7579432823.4724284562341.325190352418.73956267151.0631590597

8.57.75316227766.01683856234132.51903492922.637794003112.0040575406

8.79.8501187233.6272726309573444.801953112.9367169413144.0045247587

97.7100000000050118723.36272733421.867869351211.2982146879

9.157.31412537544.6227619952623.14968883587.64702423846.9576705068

9.47.852511886431.5095970794578.43841383881.984774302813.5507882765

9.67.73981071705.5349850118723.36272734134.748740788211.2982146879

108.310000000000199526231.4968884690.722222524323.3791528404

10.1812589254117.94171000000004841.025423326316.2524671362

10.38.519952623149.6889316227766.0168385156.234487503129.7921435955

10.65944668359215.096510000000005758.036681007354.611512983

10.89.7563095734448.01955623413251.903516036.9961532115135.5370074874

119.11000000000001258925411.794176430.077317116161.6482424703

12.59.23162277660168.381584893192.4611110320.02892244669.5916591958

&A

Page &P

powerpoint version

0.0061595271

0.001

0.001

0.0012743038

0.0028016261

0.0031626175

0.0024818395

0.0054564588

0.0379397737

0.0143880788

0.0886237606

0.0886237606

0.4283754369

1.6248974742

0.4835718946

0.4835718946

1.0006449289

7.8541709431

1.0631590597

12.0040575406

144.0045247587

11.2982146879

6.9576705068

13.5507882765

11.2982146879

23.3791528404

16.2524671362

29.7921435955

54.611512983

135.5370074874

61.6482424703

69.5916591958

Wavelength (nm)

Relative absorption in water

Sheet1 (4)

xyxxnormynorm

01.5131.6227766017200.2050.0061595271

10101274.44252040580.001

3.806309.57344480191663.72097420870.001

40.2100001.5848931925706.93720400720.0012743038

4.20.8515848.93192461117.0794578438752.96733089580.0028016261

4.30.9519952.62314968888.9125093813777.09440441760.0031626175

4.50.7531622.77660168385.6234132519827.69261008150.0024818395

4.81.463095.734448019325.1188643151909.83370549210.0054564588

531000001000969.07483847250.0379397737

5.32.2199526.231496888158.48931924611065.24685668010.0143880788

5.73.7501187.2336272735011.87233627271208.4838563010.0886237606

63.710000005011.87233627271328.41508020410.0886237606

6.251584893.192461121000001414.91090240160.4283754369

6.46.12511886.431509591258925.411794171507.03864444781.6248974742

6.65.13981071.70553498125892.5411794171605.16501216030.4835718946

6.85.16309573.44480194125892.5411794171709.6805883220.4835718946

75.710000000501187.2336272731821.00138735961.0006449289

7.37.419952623.149688825118864.31509592001.71950285347.8541709431

7.95.7579432823.4724284562341.325190352418.73956267151.0631590597

8.57.75316227766.01683856234132.51903492922.637794003112.0040575406

8.79.8501187233.6272726309573444.801953112.9367169413144.0045247587

97.7100000000050118723.36272733421.867869351211.2982146879

9.157.31412537544.6227619952623.14968883587.64702423846.9576705068

9.47.852511886431.5095970794578.43841383881.984774302813.5507882765

9.67.73981071705.5349850118723.36272734134.748740788211.2982146879

108.310000000000199526231.4968884690.722222524323.3791528404

10.1812589254117.94171000000004841.025423326316.2524671362

10.38.519952623149.6889316227766.0168385156.234487503129.7921435955

10.65944668359215.096510000000005758.036681007354.611512983

10.89.7563095734448.01955623413251.903516036.9961532115135.5370074874

119.11000000000001258925411.794176430.077317116161.6482424703

12.59.23162277660168.381584893192.4611110320.02892244669.5916591958

&A

Page &P

Sheet2

00.001

1.90.01

3.750.1

5.51

7.2510

9.1100

11.21000

&A

Page &P

Sheet2

&A

Page &P

Sheet3

0200

2.15400

3.4600

5.11000

7.32000

9.44000

11.78000

&A

Page &P

Sheet3

&A

Page &P

combined

xMelaninticks

01.5

0.47.950.85

0.456.550.8

0.64.950.45

0.754.50.2

0.94.650.15

14.730

1.34.357.2

1.34.057.2

1.955.756.83

2.37.46.60

2.65.66.4

2.94.96.170

35.66.1

3.155.46

3.35.755.95

3.545.70

3.752.105.55

3.951.850.15.37

41.850.25.37

4.220.855.25

4.32.120.9550

4.52.280.754.75

4.82.51.44.40

4.92.62.44.3

5.052.6834.10

5.32.352.23.8

5.42.232.43.78

5.71.93.73.5

5.92.873.7

6.21.855

6.41.876.1

6.651.955.1

6.85.1

75.7

7.37.40

7.95.75

8.57.75

8.79.80

97.7

9.157.3

9.47.85

9.67.70

108.3

10.180

10.38.5

10.659

10.89.750

119.1

11.39.10

11.79.150

12.29.20

&A

Page &P

combined

01.500

7.950.850.40.4

6.550.80.450.45

4.950.450.60.6

4.50.20.750.75

4.650.150.90.9

4.73011

4.351.37.21.3

4.051.37.21.3

5.751.956.831.95

7.42.36.60

5.62.66.42.6

4.92.96.170

5.636.13

5.43.1563.15

5.753.35.953.3

43.55.70

2.105.553.75

1.850.15.373.95

1.850.25.374

20.855.254.2

2.120.9550

2.280.754.754.5

2.51.44.40

2.62.44.34.9

2.6834.10

2.352.23.85.3

2.232.43.785.4

1.93.73.55.7

2.873.75.95.9

1.8556.26.2

1.876.16.46.4

1.955.16.656.65

6.85.16.86.8

75.777

7.37.47.30

7.95.757.97.9

8.57.758.58.5

8.79.88.70

97.799

9.157.39.159.15

9.47.859.49.4

9.67.79.60

108.31010

10.1810.10

10.38.510.310.3

10.65910.6510.65

10.89.7510.80

119.11111

11.39.111.30

11.79.1511.70

12.29.212.20

&A

Page &P

200

400

600

1000

2000

4000

HbO2

H2O

Melanin

ticks

Wavelength / nm

Relative Absorption Coefficients (log scale)

combined (2)

xMelaninticks

01.5

0.47.950.85

0.456.550.8

0.64.950.45

0.754.50.2

0.94.650.15

14.730

1.34.357.2

1.34.057.2

1.955.756.83

2.37.46.60

2.65.66.4

2.94.96.170

35.66.1

3.155.46

3.35.755.95

3.545.70

3.752.105.55

3.951.850.15.37

41.850.25.37

4.220.855.25

4.32.120.9550

4.52.280.754.75

4.82.51.44.40

4.92.62.44.3

5.052.6834.10

5.32.352.23.8

5.42.232.43.78

5.71.93.73.5

5.92.873.7

6.21.855

6.41.876.1

6.651.955.1

6.85.1

75.7

7.37.40

7.95.75

8.57.75

8.79.80

97.7

9.157.3

9.47.85

9.67.70

108.3

10.180

10.38.5

10.659

10.89.750

119.1

11.39.10

11.79.150

12.29.20

&A

Page &P

combined (2)

01.500

7.950.850.40.4

6.550.80.450.45

4.950.450.60.6

4.50.20.750.75

4.650.150.90.9

4.73011

4.351.37.21.3

4.051.37.21.3

5.751.956.831.95

7.42.36.60

5.62.66.42.6

4.92.96.170

5.636.13

5.43.1563.15

5.753.35.953.3

43.55.70

2.105.553.75

1.850.15.373.95

1.850.25.374

20.855.254.2

2.120.9550

2.280.754.754.5

2.51.44.40

2.62.44.34.9

2.6834.10

2.352.23.85.3

2.232.43.785.4

1.93.73.55.7

2.873.75.95.9

1.8556.26.2

1.876.16.46.4

1.955.16.656.65

6.85.16.86.8

75.777

7.37.47.30

7.95.757.97.9

8.57.758.58.5

8.79.88.70

97.799

9.157.39.159.15

9.47.859.49.4

9.67.79.60

108.31010

10.1810.10

10.38.510.310.3

10.65910.6510.65

10.89.7510.80

119.11111

11.39.111.30

11.79.1511.70

12.29.212.20

&C&"Comic Sans MS,Regular"&28Horses for Courses

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Nd:YAG

CO2

Ho:YAG

Ar

200

400

1000

5000

10000

water

HbO2

melanin

HbO2

H2O

Melanin

ticks

Wavelength (nm)

Absorption (log scale)

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Absorption of electromagnetic radiation in the eye (Sliney & Wolbarsht 1980)

__________________________Continuous beam __Single pulse

__ __ __ __ __ __ __ Interrupted pulses

Laser Safety Classes

Video 2

Laser Device Classes & HazardsClass 1Class 1MClass 2Class 2MClass 3RClass 3BClass 4Applies to device as a whole.

MPE = Maximum permissible exposure

Class 1no 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 eyeno risk to skin

Class 2no 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 2Mno risk to naked eye for short time exposureno risk to skin

Class 3Rlow risk to eyes no risk to skin(risk for intentional intrabeam viewing only)(may be a dazzle hazard)

Class 3Bmedium to high risk to eyeslow risk to skin(aversion response protects skin, or must be focussed to such a small spot that pin-prick effect only)

Class 4high risk to eyes and skindiffuse reflection may be hazardous(possible fire hazard)

HEYH Trust CP137Health & Safety at Work Policy- Lasers -Includes safety of class 3B and class 4 lasers

Safety PrinciplesEngineeringe.g. doors, blinds

Systems of worke.g. Local Rules, warning signs, etc

Personal protective equipment (PPE)e.g. Laser safety eyewear

Risk Assessments

Risk Assessments

Laser Safety StructureRisk assessmentControlled AreaLocal RulesLaser Protection SupervisorLaser Protection AdviserAuthorised Operators and Assistants

Controlled AreaMust contain the riskNeed to know nominal ocular hazard distance/zone (NOHD, or NOHZ)i.e. distance where exposure level < MPEe.g. Lithotripsy laser - 80 centimetrese.g. Surgical CO2 - 40 metresWalls, blinds, doors (without gaps), etc.Lock doors unless can justify notWarning signs at every entrance

Local Rules (How to work safely in the Controlled Area)Specific to each laserWhat are hazards?Controlled area - limit area of hazard - signsUsers & Laser Protection SupervisorSafety precautions (e.g. eyewear, blinds)Methods of safe working, etc.Adverse incident procedure, LPA, etc.

Warning SignsIONISING RADIATION(e.g. X-rays)Ultraviolet RF radiationHazardous magnetic fieldLASER

Example

Laser Protection Supervisor

Laser Protection Adviser

Authorised Users

Hull and East Yorkshire Hospitals

NHS Trust

LASER SAFETY

AUTHORISED LASER OPERATOR (clinical)

Laser:

I have read and understand

the Trust Laser Radiation Health & Safety Policy,

the Local Rules & relevant sections of the manufacturers 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).

[vgln02 : c:\a~1.joh\non_ioni\stmnt3-c.doc : 20/09/2010]

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.

ExampleLaser520-575 nm Green, 2 W568-575 nm Yellow, 1 W670 nm Red (aim), < 5 mWGoggles labelled560-570 nm OD>4570-580 nm OD>5580-650 nm OD>6

ExampleLaser520-575 nm Green, 2 W568-575 nm Yellow, 1 W670 nm Red (aim), < 5 mWGoggles labelled560-570 nm OD>4570-580 nm OD>5580-650 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 LabellingDI 1060 L7 X Z620 TO 700 nm OD 2 CARBON DIOXIDE, O.D. 10 @ 10600 NMDIR 690 - 1290 L4D 1064 L7, IR 1064 L8, DIR 1350 - 1400 L7, DIR > 1400 - 1580 L5, DI 2090 - 2100 L5, DI 2900 - 2940 L5D = 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)

WavelengthNumber before the L in nanometresColour of beamMay be single number (e.g. 10600) or a range (e.g. 2090 2100)Wavelength on laser should fall within range on eyewear

Optical DensityNumber after the LStrength of filterOD 1 only 1/10th of laser light transmittedOD2 - 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

(

Ho:YAG

2100 nm

(

Nd:YAG

1060 nm

(

LaserTripter

504 nm

(

Argon

477 or 515 nm

(

1047 - 1400 DI L71047 - 1350 R L8> 1350 - 1400 R L7>1400 - 1580 DI L52090 - 2100 DI L52900 - 2940 DI L510600 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 EyewearMust match the laser in use (whether specs or filter)Must be cleaned in accordance with manufacturers instructionsIf damaged, take out of serviceConsider protection of patients eyes

Other HazardsFireAnaesthetic gas ignitionPlumesElectrical hazard

Can be fatal

Electrical HazardBig capacitor used to drive laser, so dangerous even when unpluggedSeveral fatalities from lasersDONT OPEN OR DISMANTLE LASERDont let anyone else do so unless they are suitably qualified and trained.

PlumeMostly steam, carbon particles, cellular products - average 0.3 m particlesMay contain formaldehyde, hydrogen cyanide, hydrocarbons, mutagensHuman papilloma DNA identified in plume from surgery to remove of papillomasUse smoke extraction with filter (

Odds and endsMaintenanceReflections of polished instrumentsCheck fibre. Fibre breaks.Oxygen hazard.

And finally ....Example of laser accidentDr. C. David DeckerNd:YAG, 6mJ, 10 ns pulseGoggles available, but Tunnel visionClouded upUncomfortableSo not wornReflection beam hit eyePop!

Goldman-Fields Scan of Dr Deckers damaged eye 4 months after accidentDamage under high-intensity illumination (red)Damage under low-intensity illumination (blue)Laser induced blind spots (pink)Optic nerve blind spot (orange)

f i n

Visible 390-740 nm400-1400 nm retinal hazard region

Visible 390-740 nm400-1400 nm retinal hazard region

The following text was printed in "Laser Focus", august 1977. Accident victim's viewBecause laser injuries to eyes are rare, workers tend to discount the importance of safety precautions. The following dramatic account by Dr. C. David Decker, a victim of such an accident earlier this year was prepared in the hope that his experience may increase vigilance among his collegues. The necessity for safety precautions with highpower lasers was forcibly brought hme to me last January when I was partially blinded by a reflection from a relatively weak neodymium-yag laserbeam. Retinal damage resulted from a 6-millijoule, 10-nanosecond pulse of invisible 1,064-nanometer radiation. I was not wearing protective goggles at the time, although they were available in the laboratory. As any experienced laser researcher knows, goggles not only cause tunnel vision and become fogged, they become very uncomfortable after several hours in the laboratory. When the beam struck my eye I heard a distinct popping sound, caused by a laser-induced explosion at the back of my eyeball. My vision was obscured almost immediately by streams of blood floationg in the vitreous humor, and by what appeared to be particulate matter suspended in the vitreous humor. It was like viewing the world through a round fishbowl full of glycerol into which a quart of blood and a handful of black pepper have been partially mixed. There was local pain within a few minutes of the accident, but it did not become excruciating. The most immediate response after such an accident is horror. As a Vietnam Veteran, I have seen several terrible scenes of human carnage, but none affected me more than viewing the world through my bloodfilled eyeball. In the aftermath of the accident I went into shock, as is typical in personal injury accidents. As it turns out, my injury was severe but not nearly as bad as it might have been. I was not looking directly at the prism from which the beam had reflected, so the retinal damage is not in the fovea. The beam struck my retina between the fovea and the optic nerve, missing the optic nerve by about three millimeters. Had the focused beam struck the fovea, I would have sustained a blind spot in the center of my field of vision. Had it struck the optic nerve, I probably would have lost the sight of that eye. Eye damage caused by laserpulse is shown in this plot of field of view under high-intensity illumination (red line) and under low-intensity illumination (blue line). Outer circles show field of view; the two small regions inside the field (pink) of view are blind spots produced by laser damage. The blind spots are larger than the lesion and occupy a larger area under low illumination. The optic nerve blind spot is orange, close to the lesions.The beam did not strike so close to the optic nerve, however, that it wevered nerve-fiber bundles radiating from the optic nerve. This has resulted in a cresentshaped blind spot many times the size of the lesion. The diagram is a Goldman-Fields scan of the damaged eye, indicating the sightless portions of my field of view four months after the accident. The small blind spot at the top exists for no discernible reason; the lateral blind spot is the optic nerve blind spot. The effect of the large blind area is much like having a finger placed over one's field of vision. Also I still have numerous floating objects in the field of view of my damaged eye, although the blood streamers have disappeared. These "floaters" are more a daily hinderance than the blind areas, because the brain tries to integrate out the blind area when the undamaged eye is open. There is also recurrent pain in the eye, especially when I have been reading too long or when I get tired. The moral of all this is to be careful and to wear protective goggles when using highpower lasers. The temporary discomfort is far less than the permanent discomfort of eye damage. The type of reflected beam which injured me also is produced by the polarizers used in q switches, by intracavity diffraction gratings, and by all beamsplitters or polarizers used in optical chains.C. DAVID DECKER