Optical Terms & Abbreviations

Decoding your eyeglass prescription can feel like cracking a secret code. But don't worry—we’ve simplified it for you! Below is a helpful guide to the abbreviations and terms you’re likely to see on your prescription.

Key Prescription Terms & Abbreviations​​​​​

ADD (or NV-ADD)

• Found on prescriptions for bifocals and progressive lenses, this indicates the extra magnification (additional lens power) needed for close-up tasks like reading or working on a computer.​​​​​

AR (Anti-Reflective)

• A lens coating that reduces glare and reflections, improving clarity and appearance.​​​​​

Axis (x)

• A number between 1 and 180 that specifies the direction of astigmatism correction. It works together with the CYL (cylinder) value to fine-tune the lens for an irregular eye shape.​​​​​

BAL (Balance)

• Used when one eye has little or no vision. BAL means the same prescription is applied to both eyes, creating a balanced appearance and equal lens weight in your glasses.

BC (Base Curve)

• Describes the curvature of a contact lens to ensure a comfortable fit for your eye.​​​​​

BD, BI, BO, BU (Prism Adjustment)

• Symbols for prism correction in cases like double vision or alignment issues.

• BD: Base Down

• BI: Base In

• BO: Base Out

• BU: Base Up​​​​​

CYL (Cylinder)

• Works with the Axis to correct astigmatism.

• If there’s no astigmatism correction, the CYL may be blank, marked as DS or SPH, or simply entered as "0."

DIA (Diameter)

• Specifies the size of a contact lens in millimeters to fit your eye properly.**​​​​​**

DS (Diopter Simplex)

• Appears under CYL (cylinder) when no astigmatism correction is required and can be entered as "0."​​​​​

DV (Distance Vision)

• Indicates the part of your prescription that corrects vision for far-away objects.​​​​​

FT (Flat-Top Bifocal)

• A bifocal lens style with a visible line separating the distance and near vision areas.​​​​​

NV (Near Vision)

• Refers to correction needed for close-up tasks like reading.​​​​​

OD, OS, OU

• OD (Oculus Dexter): Right eye

• OS (Oculus Sinister): Left eye

• OU (Oculus Uterque): Both eyes​​​​​

PAL (Progressive Addition Lens)

• Used as shorthand for progressive lenses, which correct for distance, intermediate, and near vision without visible lines.​​​​​

PD (Pupillary Distance):

• The distance (in millimeters) between the centers of your pupils. Correct PD ensures your prescription aligns with your eyes for clear, comfortable vision.​​​​​

PL (Plano)

• Latin for "flat." Means “no correction” is needed and can be entered as "0."​​​​​

Rx (Prescription)

• Simply shorthand for “prescription.”​​​​​

SPH (Sphere)

• Indicates lens power for correcting nearsightedness or farsightedness:

• Negative (-): Corrects nearsightedness (trouble seeing far away).

• Positive (+): Corrects farsightedness (trouble seeing close-up).

• If listed under CYL, it means no astigmatism correction is needed and can be entered as "0."​​​​​

UV (Ultraviolet)

• UV protection blocks harmful UV rays from the sun—standard on all Zenni lenses!​​​​​

VA (Visual Acuity)

• Measures how well you see with corrective lenses, often noted as a fraction (e.g., 20/20). You won’t need this for ordering glasses.