Damage threshold from large retinal spot size repetetive-pulse laser exposures

We have measured the retinal damage threshold for a large spot size, multiple-pulse exposure to a Q-switched, frequency-double Nd:YAG laser (532 nm, 7 ns pulses). A 500 μm diameter retinal beam spot was used. The ED₅₀, expressed as the per-pulse energy, varies only weakly with the number of pulses, n, for this extended spot size. The previously reported threshold for a multiple-pulse exposure for a 900 μm retinal spot size also shows the same weak dependence on the number of pulses. The multiple-pulse ED₅₀ for an extended spot-size exposure does not follow the n^-1/4 dependence exhibited by small spot size exposures produced by a collimated beam.