Accession Number : ADA315588

Title :   Retinal Damage and Laser-Induced Breakdown Produced by Ultrashort-Pulse Lasers.

Descriptive Note : Final rept. Oct 93-May 95,

Corporate Author : ANALYTIC SCIENCES CORP SAN ANTONIO TX

Personal Author(s) : Cain, Clarence P. ; DiCarlo, Cher I. ; Rockwell, Benjamin A. ; Kennedy, Paul K. ; Roach, W. P.

PDF Url : ADA315588

Report Date : SEP 1996

Pagination or Media Count : 12

Abstract : In vivo retinal injury studies using ultrashort-pulse lasers at visible wavelengths for both rabbit and primate eyes have been completed, and the results are presented herein for laser-induced breakdown (LIB) and bubble generation. Results of previous measurements for the millimum visible lesion (MVL) threshold doses for both primate and rabbit eyes were reported earlier for pulsewidths from 4 nanoseconds (ns) to as low as 90 femtoseconds (fs). We have recorded on video the first in vivo LIB in vitreous using both albino (New Zealand white) and pigmented (Dutch-belted) rabbit and rhesus monkey eyes with 580-nanometer (nm), 120-fs pulses. We believe the phenomena responsible for bubble generation to be LIB because of the extremely high irradiances within the focused beam and because of the very low absorption properties of the vitreous humor. The laser-generated LIB-ED(50) bubble threshold for the monkey eye was 0.56 uJ at 120 fs. Results of our nonlinear modeling and calculations for self-focusing within the eye and for LIB thresholds are presented and are compared with our experimental results. Data is presented which show that LIB thresholds cannot be reached with MVL-ED(50) doses until the pulsewidth drops to <600 fs and the retinal image diameter is close to 10 micrometers (um). Self-focusing and LIB are the two nonlinear effects shown to affect the visible lesion thresholds, and our results also explain why it is so difficult to produce hemorrhagic lesions in either the rabbit or primate eye with visible 100-uJ, 100-fs laser pulses.

Descriptors :   *THRESHOLD EFFECTS, *PULSED LASERS, *WOUNDS AND INJURIES, *RETINA, *EYE, *IN VIVO ANALYSIS, FREQUENCY, DIAMETERS, DAMAGE, MODELS, NONLINEAR SYSTEMS, RADIANCE, IMAGES, BUBBLES, VISIBILITY, DOSAGE, ABSORPTION, PRIMATES, LESIONS, RABBITS, RHESUS MONKEYS, MONKEYS, HEMORRHAGE, NEW ZEALAND.

Subject Categories : Anatomy and Physiology
      Lasers and Masers
      Optics

Distribution Statement : APPROVED FOR PUBLIC RELEASE