OD and OS are abbreviations used in eye care to refer to the right and left eyes, respectively. OD stands for "oculus dexter," which is Latin for "right eye," while OS stands for "oculus sinister," which is Latin for "left eye". These abbreviations are commonly used in prescriptions for eyeglasses, contact lenses, and eye medicines. In addition to OD and OS, you might also see the abbreviation OU, which stands for "oculus uterque," meaning "both eyes". Other important abbreviations that you might encounter in an eye prescription include SPH, CYL, Axis, Add, and Prism.