Ocular Damage From Multiple-Pulse Laser Exposures*

Funduscopically observable damage thresholds were determined for rhesus retinae exposed to repetitively-pulsed (10 Hz), Q-switched (16nsec) Nd:YAG laser radiation. Threshold energy per pulse for trains of 10 and 100 pulses were compared with the single-pulse thresholds for both 1064- and 532-nm radiation. When the beam was collimated, both macular and paramacular exposures showed a cumulative effect in accord with the predicted relation EDSymbol = n-1/4 EDSymbol When the beam was made divergent to produce large (900 ˆm) retinal images, the cumulative effect was not observed. This indicates that current multiple-pulse laser safety standards do not necessarily apply to extended source cases.