O.D / Right Eye – O.D stands for Oculus Dexter, which means right eye.

O.S / Left Eye – O.S stands for Oculus Sinister, which means left eye. Don’t ask us why it sounds like “evil eye”.

Power / Sphere / Sph – Your power is the strength of your prescription. + means you are far-sighted, – means you are near-sighted (myopia).

B.C / Curve / Base Curve – Your base curve measures the curvature of your eye. The larger the number, the flatter your eye. An incorrect base curve may cause irritation or your lens to not sit properly in your eye.

Diameter / Dia / D – The diameter of your lens in millimeters. A correct diameter ensures proper vision and comfort for you.

Add power/ Add / Addition – Add power is for us folks with presbyopia, and are found in multifocal lenses. It may be a number or a “low/medium/high” word with a max add. rating.