Maybe it is possible, but some optician would refuse to repllace the lenses for bifocals because it is difficult to complete them. Getting a new pair of bifocal sunglasses is much easier and cheaper than replace the lenses for bifocal lenses. Hope this can help you. Good luck.
Maybe not.If you want it to become bifocal glasses,the lenses should be replaced.But generally the lens of bifocal are much bigger than regular ones,so there is no way to put them in the frame. You need to get a new pair of bifocal glasses.