What does the abbreviation "O.S." stand for in medical terms?

The abbreviation "O.S." in medical terminology specifically stands for "oculus sinister," which translates from Latin to "left eye." This term is widely used in healthcare, particularly in ophthalmology, to indicate that a particular instruction or observation relates to the left eye of a patient. Medical professionals often use abbreviations to streamline communication and documentation, and understanding these terms is essential for providing accurate care.

In contrast, other options represent different meanings: "right eye" is denoted by "O.D." (oculus dexter), "both eyes" is often represented as "O.U." (oculi unitas), and "ear" typically doesn't have a direct abbreviation of "O.S."—instead, "A" (auris) is used for ears, with specific designations for left and right ears such as "A.S." for the left ear (auris sinister) and "A.D." for the right ear (auris dexter). Therefore, knowing that "O.S." refers to the left eye is crucial for anyone working in healthcare settings, particularly those involved in administering medications or treatments related to vision.