Retinal Damage and Laser-Induced Breakdown Produced by Ultrashort-Pulse Lasers.
Final rept. Oct 93-May 95,
ANALYTIC SCIENCES CORP SAN ANTONIO TX
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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-ED50 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-ED50 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.
- Anatomy and Physiology
- Lasers and Masers