Astronut,
Welcome! to Birdforum. When considering eye relief, there's also the issue of useable eye relief vs. the manufacturer's listed eye relief, which can vary a bit or considerably, depending on the brand and model.
Some optics companies measure eye relief from the top EP lens to the point where the image focuses. That measurement doesn't take into consideration the 2-3mm recession of the EP lens below the top of the EP housing (to give enough clearance for curved eyeglass lenses) and the 2-3mm taken up by the twist-up eyecups sitting on top of the EP housing. So you could use up to 4-6mm useable eye relief between the lens recession and eyecup thickness.
As Phil commented, you have to minus the distance your glasses sit back from your eyes, you also the thickness of your glasses. Polycarbonate glasses are thinner than glass and some people's prescriptions are thicker than others. When you add in those factors, 15mm is cutting it pretty close, but some eyeglass wearers do get by with that much.
The only way to know if the listed 15mm ER on the Meopta 10x42 HD is going to work for your glasses/face is to try the bin yourself.
There's a Cabela's in MA in East Hartford, and they're opening a new store in Berlin, MA next year. You could also check out Cabela's 10x42 Euro HD, which is the same bin as Meopta's, but $100 cheaper.
Brock