OD and OS are abbreviations used in eye prescriptions to indicate the right and left eye, 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 traditional and have been used for a long time, but some eye care professionals may use modernized prescriptions that replace OD with RE (right eye) and OS with LE (left eye) . Its important to understand these abbreviations when reading your eye prescription, as they indicate which eye the prescription is for.