> Granted it's within a spectrum of choices such as it's -1.5 or -2, not -1.66421 (right?)
Usually right, typically in 0.25 steps. Then there's Zeiss i.Scription [0], with lenses produced not only to weird numbers, but also to correct higher order deviations than just spherical and cylindrical.
I haven't tried those yet, seeing slightly changing test results on the needed standard correction, so I assume that higher order correction would be a short term improvement only.
Usually right, typically in 0.25 steps. Then there's Zeiss i.Scription [0], with lenses produced not only to weird numbers, but also to correct higher order deviations than just spherical and cylindrical.
I haven't tried those yet, seeing slightly changing test results on the needed standard correction, so I assume that higher order correction would be a short term improvement only.
[0] https://www.zeiss.com/vision-care/us/eyeglass-lenses-from-ze...