Question
I've got a few laser pointers: a red one, and a green one. The green laser pointer is much stronger than the red one, it's the type that you can seem the beam if it's dark enough (it's 5mW).
What level of laser output is safe to use for playing with a cat?
Answer
This article from Princeton University deals with laser pointer use and human effect, and it mentions that use of laser pointers that are higher than 5 mW are dangerous and should not be used, so it seems like the green one might be safe, although they recommend that the lower the output the better, as they will be safer.
Like with any laser, avoid pointing it at your cat's eyes, or at reflective surfaces that might reflect the laser into their eyes, and that can cause problems, the same way it can for humans.
Further, though, beyond just the output, another concern is that since the cats cannot "kill" the laser, they are not able to come down from the "high" of hunting, and may redirect that energy in negative ways (excessive grooming, aggression, etc), so it is suggested that at the end of a laser pointer play session, you give the cat something to "kill" such as a stuffed toy or something similar.
Answered By - Ash