They may not look particularly trendy, but clip-on sunglasses which flip down over the existing spectacles do help a lot. You also have the option of tinted prescription lenses but these are a lot more expensive.
Polarized lenses are fine for daylight driving but not particularly good for night time so you may need two pairs!!
On deep windscreens I have seen tinted strips fitted across the inside top of glass, but this may defeat the object of having a large windscreen.
You may also find this interesting click here