My only concern is related specifically to eyeglasses. The geometry and clarity of a Dial Indicator is not absolutely critical, lenses for your glasses is another story.
Mothers is fine, although I typically use 3M products when possible. Mother's vs Meguiar's is essentially the Ford vs Chevy of the car detailing world. Both companies tend to sell their version of California Special Sauce, and their product descriptions can be entirely too vague at times. 3M on the other hand tends to be in the business of selling Fucking Chemicals and their products tend to be labeled accordingly.
Anyway, opinion: If I was dead set on polish, then the Mothers mag/aluminum polish (or something similar, in the 2000 - 3000 range) would probably be a starting point. I'd probably then consider going over it again with a finer compound.
The problem, in general, with polishing is that you're supposed to start with a compound that has an abrasive roughly the same size as the scratch itself and work your way up. In reality, to make that scratch fuck off entirely from polishing, you're going to fundamentally alter the geometry of the lens.
There is allegedly an alternative out there that I looked into 5+ years ago. I don't know what it is called or how to find it, but I recall seeing something that was essentially Bondo for glasses. You clean the lens, apply the compound to fill the scratch, and then buff out any excess. It could be too good to be true, I don't know as we didn't end up going that route.