Oh this was the Arizona rally on the 12th..wonder what they got exposed to that did not affect anyone else..only those sitting behind Trump, really weird, I would think at first the sunlight and perhaps reflection from the teleprompter caused blurred vision but not sure..heck that is why I wear sunglasses when Im outside, I cant be without it otherwise I get a bad headache
Based on the symptoms this sounds to me like a targeted IR laser attack. Because the laser is infrared its not visible without night vision but that does not mean its not doing damage.
Another possibility would be a microwave weapon. Either of these could result in the injuries described.
Both would be hard to detect unless you were specifically looking for them. That's my two sense.