Not an aviation thing, but I was lit up by some idiot with one of these devices about three years back from a range of 30 feet while at work. After around 20 minutes, I had a gritty type feeling in one eye and shortly after that, went to the local A&E as the pain increased markedly.
No serious damage done as if turned out and the eye was back to normal the morning after, when the drops had worn off, but it gives me an appreciation of what it can be like to get illuminated. I wouldn't want to be crewing an aircraft and have it happen.