Ocular damage thresholds and mechanisms for ultrashort pulses of both visible and infrared laser radiation in the rhesus monkey

Near-Infrared Ultrashort Pulse Laser Bioeffects Studies

“…However, both are about double the 2.2 jJ at 24 hours reported by Taboada and Gibbons [19] for a pulse width of 6 ps, but they are smaller than the 8.7 ^J reported by Goldman et al [13] for a 30-ps pulse width. The threshold for both pulse widths decreased with time and the fiducial limits were reduced m well.…”

“…There are several reported data points for rhesus monkeys for pulse widths <1 ns at near-IR wavelengths as shown in the Figure 6, including Goldman et al, [13] Ham et al, [Ham, 1985 #62] Taboada & Gibbons, [19] Lund & Beatrice. Our data points are shown below all other data points with the exception of the Taboada & Gibbons data for 6 ps.…”

“…In this study we are reporting retinal damage thresholds for single laser pulses of near-infrared wavelengths and comparing our resuhs with those for both near-infi-ared and visible wavelengths previously reported. [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23] We have determined the threshold dosages for ophthalmoscopically minimal visible lesions (MVL-ED50) for pulse widths of 150 femtoseconds (fs), 1, 20, and 80 picoseconds (ps) and 7 nanoseconds (ns) and the fluorescein angiography threshold dosages at one-hour and 24-hours post exposure. We have previously reported retinal injury studies of visible wavelengths for pulse widths down to 90 fs for pigmented rabbit eyes [24], [25] and for rhesus monkey eyes.…”

“…This time dependence in the rate process model is precisely what allows tiie retinal radiant exposure to decrease with increasing retinal image size as reported in the literature. Reductions of more than an order of magnitude in radiant exposure have been measured [28], [20], [13] It must be remembered that the energy deposited within the retina increases proportionally with image size at the visible lesion threshold. Additionally, the time required for the elevated temperature within the exposed area to decrease to the body temperature, increases with larger retinal spot sizes.…”

Visible lesion laser thresholds in Cynomolgus (Macaca fascicularis) retina with a 1064 nm 12-ns pulsed laser

“…Comparative biometric data from cynomolgus monkey, rhesus monkey and human subjects is listed in The damage mechanism for retinal laser exposures in the 10-ns exposure regime is believed to be primarily photomechanical in nature. [8][9][10][11] Damage occurs as a result of the rapid deposition and conversion of laser energy at high peak irradiance levels (typically near the beam focus) into thermally-induced pressure gradients. These rapidly increasing pressure gradients result in the propagation of acoustic, or shock waves in the biological media.…”