What OD and OS mean on eyeglass prescription

17. January 2016


If you just had an eye exam and you were given by your optometrist an eyeglass prescription. The optometrist probably mentioned that you are nearsighted or farsighted, or perhaps that you have astigmatism. We at KSA Vision Clinic will educate in following weeks how to read the prescription 

But what do all those numbers on your eyeglass prescription mean? And what about all those abbreviated terms?, such as OD, OS, SPH and CYL?

 We help you decipher your prescription so next time you can discuss as an expert with an optician when you're buying eyeglasses.

What OD and OS Mean

The first step to understanding your eyeglass prescription is knowing what "OD" and OS" mean. They are abbreviations for oculus dexter and oculus sinister, which are Latin terms for right eye and left eye.

Your eyeglass prescription also may have a column labeled "OU." This is the abbreviation for the Latin term oculus uterque, which means "both eyes."

Though the use of these abbreviated Latin terms is traditional for prescriptions written for eyeglasses, contact lenses and eye medicines, some doctors and clinics have opted to modernize their prescriptions and use RE (right eye) and LE (left eye) instead of OD and OS.

On your eyeglasses prescription, the information for your right eye (OD) comes before the information for your left eye (OS). Eye doctors write prescriptions this way because when they face you, they see your right eye on their left (first) and your left eye on their right (second).