As a glasses wearer myself, I'm lucky enough to be able to buy the prescription straight from ZEISS (though, living in the UK, it might take a while). However, it's worth pointing out that prism ...

Visiting an eye doctor is no longer the only way to receive a prescription for glasses. Many online tools ... has a muscle imbalance in their eyes. A PRISM number will often be in fractions ...

Your eyes are identified as Oculus Dexter (OD), your right eye, and Oculus Sinister (OS), your left. There will be two ...