A couple of observations.
If you wear prescription glasses most of the time, you will find most sunglasses look and feel like rubbish.
If you don't wear prescription glasses you may tollerate any old carp.
Ive picked up my wifes sunglasses and those of friends and relatives and simply cant understand how they tolerate them, they cant fit and the optics are horrible.
It may also be that the prescription versions of the fancy sunglasses may be more accurate.
My wife has just come to the point of needing prescription sunglasses and she got a pair of spotters.....she now understands what i have been saying all this time....she is simply gob smacked with the clarity and penetration compared to the rubbish she has been wearing for 30 years.
Unfortunatly my eyes are at a certain point ( getting old) and I am waiting for some stuff to sort out before I cough up for some prescription sunnies.
I wore prescription photo cromatics all day everyday for years...... but the current photo cromatics simply dont work as well as what I was wearing 10 years ago.
As someone who wears glasses almost every waking hour.
I can tell you..you must get a frame that fits your head, and you must get the frames adjusted properly.
If not preasure on you nose or ears can cause you problems and if your eyes are not in the right place in the lenses.....even without prescription that can cause you problems.
when i get new frames or I cop a blow to the head

....It takes me a week to a fortnight to get the frames just right.
If you get the frame to fit properly some of the fatigue and other problems may go away.
cheers