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Clarence P. Cain, Cynthia A. Toth, Gary D. Noojin, Val Carothers, David J. Stolarski, Benjamin A. Rockwell; Thresholds for Visible Lesions in the Primate Eye Produced by Ultrashort Near-Infrared Laser Pulses. Invest. Ophthalmol. Vis. Sci. 1999;40(10):2343-2349.
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purpose. To evaluate the effects of near-infrared (near-IR) ultrashort laser
pulses on the retinas of rhesus monkey eyes and to perform threshold
measurements for minimum visible lesions (MVLs) at pulse widths ranging
from nanoseconds to femtoseconds.
methods. Near-infrared single laser pulses were placed within the macular area
of live rhesus monkey eyes for five different pulse widths (7 nsec; 80,
20, and 1 psec; and 150 fsec). One visible wavelength of 530 nm at 100
fsec was also included in the study. Visible lesion thresholds
(MVL-ED50) were determined 1 hour and 24 hours after
exposure. Fluorescein angiography thresholds (FAVL-ED50)
were also determined using a probit analysis of the dosage. Thresholds
were calculated as that dosage causing a 50% probability for damage,
and the fiducial limits were calculated at the 95% confidence level.
results. For all pulse widths, the 24-hour MVL-ED50 was lower than
the 1-hour MVL-ED50, and they both decreased with
decreasing pulse width. Thresholds at the 1-hour reading decreased from
28.7 μJ at 7 nsec to 1.8 μJ at 150 fsec, whereas thresholds at 24
hours decreased from 19.1 μJ at 7 nsec to 1.0 μJ at 150 fsec. The
doubled 1060-nm wavelength of the 530-nm threshold decreased from 0.36
to 0.16 μJ after 24 hours. FAVL-ED50s were much higher
than MVL-ED50s, showing that FA was not as sensitive in
determining damage levels.
conclusions. Laser pulse widths less than 1 nsec in the near-IR are capable of
producing visible lesions in rhesus monkey eyes with pulse energies
between 5 and 1 μJ. Also, the near-IR thresholds for these pulse
widths are much higher than for the visible wavelengths. As with
visible wavelengths, FA is not as sensitive in determining threshold
levels as is visually observing the retina through a fundus
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