What is the meaning of OS when prescribing eye medications?

When prescribing eye medications, the abbreviation "OS" stands for "oculus sinister," which is Latin for "left eye." This terminology is commonly used in medical prescriptions and documentation to specify that the medication should be administered specifically in the left eye.

Understanding such abbreviations is crucial for accurate medication administration, especially in ophthalmology, where precise dosing and application to the correct eye are necessary for effective treatment and to avoid complications. Other abbreviations used in this context include "OD" for "oculus dexter" (right eye) and "OU" for "oculi unitas" (both eyes), which further clarifies the directionality of the medication administration.