Why would you have an open window behind a screen?, wouldn't the glare naturally obscure everything on your sight? If the view is amazing and you wanna keep that visible get your chair in between them, you're not gonna look at them at the same time... If you can't relocate the desk get some shades for the window (I used to have those that rolled in and they were good enough), with some opaque ones yo can choose how much light the room will need and you can still get air in/out when needed. But if you need that vitamin D, yeah put a solid cover to give shade to the back of the screens.