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R.J. Hope, J.P. Pasternak, K.S. Bower, D.H. Sliney, E.D. Weber; Scattered UV Irradiation During VISX Excimer Laser Keratorefractive Surgery . Invest. Ophthalmol. Vis. Sci. 2006;47(13):553.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the potential occupational health hazards associated with scattered ultraviolet laser radiation during keratorefractive surgery with the VISX excimer laser system.
Intraoperative radiometric measurements were made with the Ophir Optronics Ltd. Power / Energy Monitor (Laserstar with silicon photodiode detector PD–10). The average energy per pulse was measured using the Laserstar in data log mode. The ambient light level was measured in background mode and subtracted from the collected data. Measurements made during laser calibration and PRK procedures were evaluated using a worst–case scenario and then compared to the American Conference of Government Industrial Hygienists (ACGIH) Threshold Value Limits (TLV) to perform a risk/hazard analysis.
The maximum average UV scattered radiation level for PRK measured at 20.3 cm was 248.3 nJ per pulse. During the study the maximum ablation time was 52 seconds with a pulse frequency of 8 Hz. Therefore at the detector the maximum exposure would be (ablation time x pulse frequency x energy per pulse) / detector area (0.7854 cm2) = (52 x 8 x 248.3) / 0.7854 = 0.132 mJ / cm2. Assuming a 20 patient / day work load (40 eyes) the worst case exposure for an operating room technician situated 80 cm from the patient would be, assuming the inverse square law, equal to (40 x energy at the measurement distance) / (R/r)2) where R is the distance of the operator and r is the distance of the measurement = (40 x 0.132) / (80/20.3)2 mJ / cm2 = 0.34 mJ / cm2. Under these worst–case conditions the cumulative occupational exposure for an operating room technician 80 cm from the patient would be 0.34 mJ / cm2 for an 8–hour operating day. This is well below the existing TLV of 3mJ / cm2 for an 8–hour exposure in a 24–hour period.
Scattered UV radiation from the VISX Eximer Laser does not pose an occupational health risk for operating room personnel during PRK refractive surgery.
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