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Proceedings Paper

Retinal threshold studies for nanosecond and picosecond visible laser pulses
Author(s): William P. Roach; Cheryl Dawn DiCarlo; Gary D. Noojin; David J. Stolarski; Rodney E. Amnotte; Audrey B. Smith; Mark E. Rogers; Clarence P. Cain
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Paper Abstract

Threshold measurements for Minimum Visible Lesions (MVL) at the retina are reported for 60 picoseconds (ps) and 4 nanoseconds (ns), single laser pulses in rhesus monkey eyes using a visible wavelength of 532 nanometers (nm) from a doubled Nd:YAG laser. The 50% probability for damage (ED50) dosages are calculated for 1 hour and 24 hour post exposures using 95% fiducial limits. For both pulsewidths, the threshold values calculated by probit analysis decrease between the 1 hour and 24 hour ophthalmoscopic evaluations. The ED50 value determined for the 60 ps pulsewidth was less than half the value at 4 ns (0.43 (mu) J/60 ps vs. 0.90 (mu) J/4 ns at 24 hours) for both readings. Of the 136 exposures for pulse energies ranging from 0.03 to 5.0 (mu) J no hemorrhagic lesions were produced for either pulsewidth studied. However, at 6.6 (mu) J one intraretinal hemorrhagic lesion was observed for 60 ps. The slope of the probit curve was higher for 60 ps when compared with the 4 ns value (3.03 at 60 ps vs. 2.68 at 4 ns). MVL threshold doses calculated are comparable with those reported in the literature. However, the 4 ns MVL values is less than one order of magnitude (a factor 4.7) above the Maximum Permissible Exposure (MPE) level as defined by the 'American National Standard For The Safe Use Of Lasers', ANSI Z136.1-19932. We present the current MVL data as it compares with previous data obtained for picosecond and femtosecond laser pulse thresholds and provide a preliminary assessment of how the ANSI MPE standard might be amended.

Paper Details

Date Published: 22 May 1995
PDF: 13 pages
Proc. SPIE 2391, Laser-Tissue Interaction VI, (22 May 1995); doi: 10.1117/12.209871
Show Author Affiliations
William P. Roach, Air Force Armstrong Lab. (United States)
Cheryl Dawn DiCarlo, Air Force Armstrong Lab. (United States)
Gary D. Noojin, The Analytical Sciences Corp. (United States)
David J. Stolarski, The Analytical Sciences Corp. (United States)
Rodney E. Amnotte, Air Force Armstrong Lab. (United States)
Audrey B. Smith, The Analytical Sciences Corp. (United States)
Mark E. Rogers, Air Force Armstrong Lab. (United States)
Clarence P. Cain, The Analytical Sciences Corp. (United States)

Published in SPIE Proceedings Vol. 2391:
Laser-Tissue Interaction VI
Steven L. Jacques, Editor(s)

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