It's not difficult to track eyes consistently using computer vision. It's not difficult to aim a laser beam using a mirror galvanometer. If you're struck in the eye with a UV laser beam, the blink reflex doesn't kick in - by the time you've noticed the pain in your eyes, it's already too late. The beam doesn't have to track with particularly high accuracy to cause certain blindness, especially if there's an array of beams.

A decent hardware hacker could build an area-denial laser turret in a long weekend with a couple of hundred bucks of parts. I hope to god that nobody ever does.

A sufficiently powerful laser - over 0.5W - can cause blindness from diffuse reflection. A 100W laser fired into a room with white walls for a fraction of a second can permanently blind everyone whose eyes were open at the time.

cause

a) you can't see when you're being shot at b) it suffices if there is a sufficiently large (to you invisible) reflection within your field of vision c) you can automatically scan a whole field very quickly, invisibly, silently d) the laser spot gets larger at a distance, so the laser is not a pointer but a shotgun cone with 2m diameter

I think the thing is though that it doesn't. It just has to scatter off of something else in the wrong way, and boom.

Because lasers are usually continuous and even reflections are very dangerous.