The problem is with your LCD screens, not your sunglasses. Sunglasses have to be polarized to block light reflected off the water and ground, otherwise they are worthless. Most new LCD screens are polarized on the diagonal, so they'll go black when your head is tilted on a 45 degree angle to the screen but can be viewed in both portrait and landscape orientation (depending on how the electronics manufacturer designs the instrument). Some of the older screens are polarized vertically or horizontally, so they can either be viewed in portrait or landscape, but not both. If you've got one of those, not much you can do except get new electronics. The GPS unit that came with our boat was like that. I had to turn my head sideways or take off my glasses to see the thing. It was replaced very quickly.