My first thought is that one cannot rely on what you see on the LCD to really determine if your image is truly sharp even if you don't wear glasses - Yes, if you take the time, you can magnify the small LCD image on your camera and see if it appears sharp, or use a Hoodman magnifying device, but long experience has taught me that I only truly know when I get the image on my large 30 inch monitor. I have been fooled by what I thought were sharp LCD images that weren't when examined on my monitor at home.
And frequently, when I am shooting wildlife, I don't have the time to check my LCD as I am too busy capturing images. I can only chimp when the action slows down. I do try to verify the accuracy of the AF system of each camera body periodically, so that I can have complete trust in them when push comes to shove.
I do wear bifocals, and I have for many years, so I am aware of the aggravation that presbyopia causes. If your bifocals lenses are correct, you should be able to see the image on the LCD sharply with them, and if spectacles are correct for distance, you should be able to see that AF is working through the view finder through the distance portion of your lenses.
Yes, if cataracts are the source of your frustration, glasses aren't going to fully resolve that until you have cataract surgery.
I don't like to wear sunglasses ( or Transition lenses that get dark in sunlight ) when photographing - I think they do really interfere with seeing well in the viewfinder, especially when the ambient light is dim - before sunrise, after sunset, etc - I carry a spare set of bifocals without any tint for that reason, The lenses corrections for distance and near in my transparent glasses are the same as my Transition lens glasses that I use for driving, only the color of the lenses is different.
Modern AF systems are truly remarkable, being able to capture birds in flight after sunset is truly an incredible optical task -
If you have a large distance correction in your glasses, doing without your glasses as some have suggested won't work for you - you will have to adjust to wearing your bifocals ( progressive lenses are bifocals ) to look through the viewfinder - if you cannot see your LCD with your glasses you may need to have your bifocal lens heights adjusted. If you cannot get this resolved on your own, discuss it with your optician or optometrist - they should be able to help you get this resolved. If you wear contact lenses, your distance vision should be correct, but you may have difficulty with near - bifocal contact lenses exist, but they require many compromises from the user I think.
One other suggestion, carry a microfibre cloth and some lens cleaning solution in a pocket or your camera bag - I find my glasses get smeary, caught between my viewfinder and my eye lids and lashes - and cleaning them does help me see better when needed.