Focus on target when looking thru the scope. Parallax marked yardage, can be wrong. Ajust to your eye.
Choose glass over plastic lens. Get lined bifocals. Np progressive.
Use the method that gives you 20/20 vision , with or without glasses, adjust eye piece. Then adjust parallax, if scope has it.
Do wear some type of eye protection while shooting.
Astigmatism - glasses are designed to see clearly when looking straight through the center of the lens.
Looking through the lens on any angle will blur vision.
With a rifle scope, on a bench, i am looking through the top of the lens.
When i shoot skeet, i need to pick up the bird comming out of the house with peripheral (side) vision.
The eye is seeing through the lens on an angle.
My frame needs to be square to my face. If angled like a v , blured vision.
Working with my eye doctor, she was able to apply different perscriptions in the same lens.
The frame was made straight. Great for skeet and rifle shooting.
Handguns- get a prescription that lets the eye focus on the front sight or just beyond. Old eyes dont change focus fast enought to see target and sights clearly at the same time.
Or get one of those new fangled red dot sights.
Just how "eye" see it.