On Wed, 17 Apr 2019 12:01:12 +0100, NY wrote:

And all that work will no doubt have altered the prescription of
the
lens.

I doubt whether polishing off a few thousandths of an inch from the
surface of the lens which is probably a couple of millimetres thick will
have altered the focal length by a detectable amount.

As they have been attacked witha bit of wet 'n dry and the scratches
from that polished out the amount removed may well be more than a few
thou. It's the refractive index of the material and shape of the
front and back surfaces along with the thickness that give a lens it
properties.

OP doesn't say if these are basic single vision with no other
corrections applied and both eyes more or less the same, made with
"normal" refractive index plastic or something more complicated. I
wouldn't like to say that few thou wouldn't make a difference with
high refractive index lens, it makes a heck of difference to the
required thickness of the lens for the same correction.

It may have taken off the anti-glare coating, though...

No may about it, assuming they had a coating in the first place, most
do these days though.

--
Cheers
Dave.