Anytime I see someone mention hacking on magnetrons, I feel it my duty to remind us that the back of your eyeballs don't have pain receptors. If you were to power up thatagnetron outside of the microwave and point it at your face, it's possible you'd blind yourself before you even realized you were in danger.
Just wanted to add something. Itching is the first sign. If you feel itching in your eyes, turn the damn thing off immediately. I nearly blinded myself when I was an idiot undergrad. Kids, take the idiot adult's advice and don't play with it before you understand the theory and working principles extremely well.
And the front (cornea) has more pain receptors per surface area than any other part of your body. Not that this would necessarily help prevent cataracts if you expose your eyes to a magnetron.
I didn't realise this until I had laser surgery to correct a cornea problem. Oh dear, two days in a dark room on morfin, before I could even think straight again, no fun. But now I can see better again.
It's also a problem that there is no blood flow through your lenses. If you heat them via microwave radiation, they're going to stay hot for an alarmingly long time.
