I find a pair of Ray Bans works for me, plus I can keep them on when I get out the car and look super fly... in my head anyway 
but this relates to sun from the side, and poor coverage of the sun visor when over the driver's window. Sunglasses help for frontal sun, but not that from the side.
They do work if you wear wraparounds like Oakleys...
Not if you wear glasses though.
In response to @dubber36 in reply #2, I’ve quite a few years to go before I reach 80, but I often swivel the sun visor to the side window on one of my regular routes to block out the sun when it’s at that annoying height, as being a glasses wearer, wraparound sunglasses aren’t an option for me. I also liked the mini sun visor that VW fitted behind the rear view mirror in the mk4 Golf, to help block the sun shining into your eyes through the gap between the two sun visors.
I can remember in the 1970’s / early 1980’s that the Fiat 132 had two additional sunvisors; one above each of the front doors for the driver and front seat passenger. It meant the front occupants of the car had the benefit of two sun visors each; one forward facing and one side facing. I thought it was a great idea, but presumably it didn’t catch on, otherwise it would still be a feature on some modern day cars.
