Cheap green 523nm lasers are especially dangerous. They are marketed as Class III <5mW, but with a laser power meter they are frequently 30mW-80mW or higher.
It's not that 5mW lasers can't cause permanent damage to the retina, but rather that within 200ms the blink reflex will typically kick in and stop continued exposure.
Green lasers are typically DPSS diode lasers— which means they have a high power infrared laser diode that passes through a frequency doubling crystal to achieve green. Cheap laser pointers often skip the IR filter and will pass through a lot of IR light— which is especially dangerous because it doesn't trigger the blink reflex.
The NOHD (nominal ocular hazard distance— the distance at which there's a 50% chance of some minimally detectable permanent lesion on the retina) for a green laser pointer can be hundreds-to-thousands of feet.
The (temporary) flashblindness threshold is some multiple of that. Given the distances involved, I'm guessing it's temporary, unless someone was using some obscenely powerful (e.g. 1W) laser.
It's not that 5mW lasers can't cause permanent damage to the retina, but rather that within 200ms the blink reflex will typically kick in and stop continued exposure.
Green lasers are typically DPSS diode lasers— which means they have a high power infrared laser diode that passes through a frequency doubling crystal to achieve green. Cheap laser pointers often skip the IR filter and will pass through a lot of IR light— which is especially dangerous because it doesn't trigger the blink reflex.
The NOHD (nominal ocular hazard distance— the distance at which there's a 50% chance of some minimally detectable permanent lesion on the retina) for a green laser pointer can be hundreds-to-thousands of feet.
The (temporary) flashblindness threshold is some multiple of that. Given the distances involved, I'm guessing it's temporary, unless someone was using some obscenely powerful (e.g. 1W) laser.