if you read gunnars product description it specifically states that tints that they apply to their lenses reduce UV light. But they specifically have outdoor eye wear products, as I don't think the glasses meant for indoor use would provide comparable benefit outdoors.
So, I guess the answer you're looking for, you will need to get 2 separate pairs of glasses.
Not to be a nag, since this is your money after all, but I'd like caution you with regard to companies like these. If you're concerned about your eyes and PC usage, turn down your monitor brightness and take frequent breaks. No eyeglasses will eliminate the strain on your eyes, they might decrease it, but they don't solve the problem entirely. If you notice the wording on their website, all of it is supposition, because otherwise they'd get sued for false advertising. Basically, take all of their fancy text with a grain of salt, see if any of your local stores have these on sale (I bet they don't) and try them for yourself before you buy.
Gunnar markets what essentially amount to shooting lenses and golfing lenses that do not make the cut in those regards, usually due to image distortion. Unless you like the style of the glasses themselves in terms of fashion which is up to you, there is no reason to buy them.
no, those are not sunglasses, think of them as rx glasses with some lens treatment. It might sound silly, but point of the matter is, not all people are using their computers in perfect lighting conditions, angle, intensity, etc. In other words if one is too stupid to figure those simple things out, one can get these expensive glasses that will solve some of those issues for them.
It is like hair brushes for beard. You don't really need them but people will buy them because they are misinformed.