According to the Proto web store all Proto switch lenses provide UV protection. Dye's I4 promotional video also says all their thermal lenses have the UV protection coating.
I'm thinking the JT lenses don't have UV protection since I've experienced that eye strain too after a long day of paintballing. I use a flex with smoke lens as my primary mask but it doesn't happen all the time.
Sly Profits also are UV protecting
Stuff to come