The abbreviation OD is frequently used in eye care and has two distinct meanings. When OD is part of your lens prescription, it is the abbreviation for the Latin term Ocular Dexter, which means “right eye.” When OD is written next to your eye doctor’s name, it is the professional abbreviation for Doctor of Optometry.

There are many abbreviations used in eye care, and sometimes it can be difficult to interpret what they all mean. Another abbreviation you may see on your prescription is OS. This is the abbreviation for Ocular Sinister and is Latin for “left eye.” In computer terminology, OS can also refer to an operating system, but this is not what it refers to in eye care. 

Understanding eye abbreviations when you visit your eye doctor will help you to make informed decisions about your eye care.

RELATED READING: What’s the difference between an optometrist and an ophthalmologist?

Eyeglasses prescriptions have unfamiliar abbreviations that can be confusing. Here is a brief summary of some of the terms you may come across on your eyeglasses prescription:

• OD – Right eye. This is the abbreviation for the Latin term Oculus Dexter.
• OS – Left eye. This is the abbreviation for the Latin term Oculus Sinister.
• OU – Both eyes. This is the abbreviation for the Latin term Oculus Uterque.
• SPH –  Sphere. This means that the correction is equal in all meridians; no astigmatism exists.
• Cyl – Cylinder. This is the measurement used for the correction of astigmatism.
• Pl –  Plano. This means that no prescription is needed and is Latin for “flat.”
• D – Diopter. This is the measurement for the optical power of a lens.
• Axis – This provides information on the orientation of the cylinder power.
• Add – This is the reading prescription that corrects for presbyopia.
• Prism – This provides correction for eye misalignment.

READ MORE: How to read your eyeglasses prescription

Contact lenses need extra measurements and have additional terms and abbreviations. Here is a brief summary of some terms you may see on your contact lens prescription:

• BC – Base curve. This is a measurement of how flat or steep a lens is.
• DIA – Diameter. This is the size of the contact lens in millimeters.

The contact lens prescription will also contain information on the power of the contact lens, the brand and type, and the expiration date.

READ MORE: Understanding your contact lens prescription

Lenses are made with many designs and features to optimize vision. Some of the terminology used to describe these features include:

• SV – Single vision. There is only one prescription throughout the lens.
• BF – Bifocal. A lens in which the distance prescription is placed on the top of the lens. The near prescription is placed on the bottom portion of the lens and marked by a line.
• PAL – Progressive addition lenses. These lenses progress from distance to intermediate to near prescription without a distinct line.
• AR – Anti-reflective. This is a coating on lenses that reduces glare.
• PD – Pupillary distance. This is the distance between the center of the pupils of the left and right eyes in millimeters.
• SH – Segment height. This is the distance from the top of the near vision portion of the lens to the bottom of the lens in millimeters.

Glasses can also have tints, such as yellow, amber, brown or red, to filter out diffferent wavelengths of light. 

Transition (or photochromic) lenses lighten or darken the tint in your glasses depending on the light level. Polarized glasses are also an option to prevent glare. 

To make the most out of your visit with the optometrist, it is helpful to recognize and understand the abbreviations you will encounter. Armed with this knowledge, you will know when OD refers to your right eye and when it refers to your eye doctor’s professional degree!