Best Answer: O. S. stands for oculus sinister, which is Latin for left eye. O. D. stands for oculus dexter, which is Latin for right eye. Sph. stands for spherical lens. For the best answers, search on this site https://shorturl.im/aw8XR In Contact Lens and Glasses prescription OD means Right Eye and OS means left eye. If u want to remeber this,since in alphbets D comes before S,so first right then left eye. This Site Might Help You.