Lasers are classed in terms of their potential damage to humans, amongst other things like power output. Class 4 lasers are the worst and can be invisible to humans. That means if there’s one shining in your eyes, you won’t know about it until the damage has been done.
I deal with lasers which work to shoot down missiles heading towards our aircraft. It overloads the missile with electromagnetic energy and causes it to explode away from the aircraft. But there’s also development being done all over the world in the field of laser weapons. There are lasers which can cause damage from hundreds of kilometres away. They can blind you permanently within a matter of seconds.