Accession Number : ADA321306

Title :   'Ultrashort Laser Pulse Effects in Ocular and Related Media: Laser-Induced Shock Wave Propagation and Retinal Damage'.

Descriptive Note : Final rept. 15 Apr 93-14 Oct 96,

Corporate Author : HARVARD MEDICAL SCHOOL BOSTON MA

Personal Author(s) : Deutsch, Thomas F. ; Doukas, A. ; Flotte, T. ; Lee, S.

PDF Url : ADA321306

Report Date : DEC 1996

Pagination or Media Count : 7

Abstract : The overall objective of this project was to study the role of mechanical effects in producing retinal injury as part of a larger Air Force program on ultrashort laser pulse ocular injury. Laser-induced stress transients were generated by the ablation F of a polyimide target by an excimer laser in order to study damage due only to waves, excluding confounding factors such as cavitation. The model for ocular injury consisted of retinal pigment epithelium (RPE) cells in vitro. The response of RPE cells to compressive waves has been determined using a dye exclusion assay to deter- mine cell killing. The susceptibility of RPE cells to damage by stress waves varies with cell line. Transformed retinal pigment epithelium cells are more susceptible than normal ones. Saturation of damage versus number of stress wave pulses is observed, and a threshold-like behavior of cell killing versus stress is found. A system for generating purely tensile stress waves was developed and initial results showing that tensile stress waves are far more damaging to RPE cells than compressive ones were obtained. In order to characterize the propagation of stress waves in ocular media we have used picosecond transient grating spectroscopy to determine the acoustic attenuation and the sound velocity of the vitreous and the lens of the bovine eye in the 925-1020 Mhz range. These experiments indicated that at this frequency the sound velocity of bovine vitreous can be well approximated by that of water, but the acoustic attenuation coefficient is much higher than would be extrapolated from published low-frequency data.

Descriptors :   *PULSED LASERS, *RETINA, *EYE, *LASER DAMAGE, PROPAGATION, MECHANICAL PROPERTIES, EPITHELIUM, SPECTROSCOPY, WATER, TENSILE STRESS, SHOCK WAVES, IN VITRO ANALYSIS, GRATINGS(SPECTRA), LASER APPLICATIONS, COEFFICIENTS, WOUNDS AND INJURIES, DYES, ACOUSTIC ATTENUATION, PIGMENTS, CELLS(BIOLOGY), BOVINES, ACOUSTIC VELOCITY, EXCIMERS, LOW FREQUENCY, AIR FORCE OPERATIONS, STRESS WAVES, COMPRESSIVE PROPERTIES, MINES(ORDNANCE), CAVITATION, MECHANICAL WAVES, POLYIMIDE RESINS.

Subject Categories : Anatomy and Physiology
      Lasers and Masers
      Optics

Distribution Statement : APPROVED FOR PUBLIC RELEASE