An experimental study has been directed toward determining the retinal damage thresholds induced by picosecond pulses emited in the visible spectrum. The results were obtained on the rabbit retina for a single pulse (610 nm, 7 ps) and for repetitive pulse trains (590 nm, 7 ps per pulse) varying from 100 to 200 000 pulses. The pulse repetition frequency (PRF) used were 10 kHz, 100 kHz and 1 MHz. The ED50 obtained with fluorescein angiography for a single pulse was 0.8 μJ. The data concerning the multiple laser pulses exposures obtained with 1 Mhz PRF support the present limit values based on the total exposure duration of the train. The empirical multiple-pulse formula N−1/4 seems still acceptable for picosecond pulses delivered with a high repetition rate but does not describe with accuracy the mechanism of the repetitive-pulse injury.

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