When examining an eye prescription, many people encounter abbreviations like “OD,” “OS,” and “OU.” These terms can seem confusing at first glance, but they are standard medical abbreviations used by eye care professionals. Understanding these simple terms is the first step in deciphering your vision correction needs.
Defining OD, OS, and OU
“OD” stands for Oculus Dexter, which specifically refers to the right eye. Similarly, “OS” is an abbreviation for Oculus Sinister, designating the left eye. When you see “OU” on a prescription, it signifies Oculus Uterque, meaning both eyes. These terms are universally recognized in the optical industry.
Distinguishing between the right and left eye is important because each eye can have different vision requirements. For instance, one eye might be more nearsighted or farsighted than the other, or have a different degree of astigmatism. Precise measurements for each eye ensure that corrective lenses, whether glasses or contact lenses, are customized to provide optimal clarity and comfort. In cases where both eyes have the exact same prescription, the OU abbreviation may be used to simplify the listing.
The Latin Roots of Eye Terminology
The terms “Oculus Dexter,” “Oculus Sinister,” and “Oculus Uterque” are derived from Latin. “Oculus” means eye, “dexter” means right, “sinister” means left, and “uterque” means both. This Latin origin reflects a historical tradition in medicine and science, where Latin served as a universal language for centuries.
The use of Latin allowed medical practitioners across different regions and languages to communicate precisely and avoid ambiguity in documentation and diagnoses. While modern languages have gained prominence, Latin remains a foundational element in medical terminology for its standardization and precision, aiding global understanding.
Locating These Terms on Your Prescription
On an eyeglass or contact lens prescription, “OD,” “OS,” and “OU” label columns or rows. The measurements for your right eye appear under “OD,” while the details for your left eye appear under “OS.” For example, the spherical power (SPH), which corrects nearsightedness or farsightedness, is specified for each eye.
If you have astigmatism, additional values like cylinder (CYL) and axis will also be listed for the respective eye under OD or OS. These terms help organize the complex numerical data, ensuring that the optician can accurately produce lenses tailored to each eye’s specific needs.