I buy as cheap as possible readers, never had any distortion problems with them.
I get them covered in fine scratches in the middle of the lenses over the course of maybe 3 months.
I carry on using them till it gets really obvious that I am moving my head round trying to find a clear bit
of lens to look though.
I got a blue hot lathe chip embedded in the middle of my lens on the second day of my last new glasses

I had real good results with Trivex lenses , they did age darken after about a year. But were very abrasion and chemical resistant. (I ruined two pairs of glasses with figure prints from some chemical that was on my hands, maybe petrol).
Stu