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From OD to PD: A Doctor’s Guide to Understanding Your Eyeglass Prescription

PUBLISHED ON: March 25, 2020 by Berkeley Eye Center
LAST MODIFIED ON: March 9, 2026
POSTED IN: Eyewear & Contacts

What You Need to Know: 5 Quick Takeaways

  • OD means right eye. OS means left eye. These are Latin abbreviations.
  • A minus (-) SPH number means nearsighted. A plus (+) SPH number means farsighted.
  • If CYL and AXIS are blank or show ‘PL/DS,’ you have no astigmatism — that’s perfectly normal.
  • The ADD column indicates presbyopia (age-related reading difficulty) and is used for bifocal or progressive lenses.
  • An eyeglass prescription cannot be used to order contact lenses — they require a separate fitting and prescription.

From OD to PD: A Doctor’s Guide to Understanding Your Eyeglass Prescription

After your eye exam, you’re handed a piece of paper filled with abbreviations, numbers and plus and minus signs. It’s your key to clear vision, but it can feel like you need a secret decoder ring to understand it.

Don’t worry. It’s much simpler than it looks. At Berkeley Eye Center, we believe in empowering our patients with clear information. This guide walks you through every part of your prescription so you know exactly what it says about your unique vision.

Quick Reference: What Every Abbreviation Means

Abbreviation

Stands For

What It Means

OD

Oculus Dexter

Your right eye.

OS

Oculus Sinister

Your left eye.

OU

Oculus Uterque

Both eyes together.

SPH

Sphere

Main lens power for nearsightedness (minus) or farsightedness (plus), measured in diopters.

CYL

Cylinder

Amount of astigmatism correction needed. Blank or ‘PL/DS’ means no astigmatism.

AXIS

Axis

The angle of astigmatism correction, from 1–180 degrees.

ADD

Addition

Extra magnifying power for reading (presbyopia). Used in bifocal and progressive lenses.

PD

Pupillary Distance

Distance in mm between your pupils. Ensures lenses are centered over your eyes.

PL / DS

Plano / Diopters Sphere

Zero — no correction needed in that column.

Prism

Prism

Corrects double vision or eye alignment issues. Less common.

OD and OS: Your Right Eye and Left Eye

OD stands for Oculus Dexter, Latin for right eye. OS stands for Oculus Sinister, Latin for left eye. You may also see OU (Oculus Uterque), which means both eyes. Your prescription is organized in rows by eye, with each column showing a different type of correction.

SPH (Sphere): Your Main Lens Power

SPH, or Sphere, is the primary number on your prescription. It corrects nearsightedness or farsightedness and is measured in units called diopters.

  • A minus sign (−) means you are nearsighted (myopic). You see clearly up close but have difficulty with distance.
  • A plus sign (+) means you are farsighted (hyperopic). While many farsighted patients can see relatively well at both distances — especially when younger — vision may be blurry at near, far or both distances depending on the degree of correction needed.
  • The further the number is from zero, the stronger the prescription.

If SPH reads Plano (PL) or DS, it simply means no sphere correction is needed for that eye — this is completely normal.

read eyeglass prescription

CYL (Cylinder) and AXIS: Your Astigmatism Correction

These two numbers always work together. If you have values in these columns, it means you have astigmatism — a very common condition.

CYL (Cylinder): This number represents the amount of astigmatism correction needed. Astigmatism occurs when the eye, typically the cornea or the lens inside the eye, is not perfectly round, causing blurry or distorted vision. A common way to think of it: a normal eye is shaped like a basketball; an eye with astigmatism is shaped more like a football.

AXIS: This number, ranging from 1 to 180, indicates the angle or orientation of the astigmatism. It tells the lens lab exactly where to place the cylinder correction so it aligns with your eye.

If CYL and AXIS are blank, or if CYL reads ‘PL,’ ‘DS,’ or ‘0.00,’ it means you have no astigmatism in that eye. Many patients have no astigmatism, so blank fields in these columns are not a cause for concern.

ADD (Addition): Your Reading Power

If you see a number in the ADD column, it means you have presbyopia — the age-related loss of near focusing ability that typically begins in the early to mid-40s.

The ADD value is the extra magnifying power needed in the lower portion of your lenses to help you see clearly for reading, using a phone, or other close-up tasks. It is used to make bifocal, trifocal or progressive lenses. In most cases this number is the same for both eyes, though your doctor may occasionally prescribe slightly different ADD values for each eye.

Prism and Base: Eye Alignment Correction

Prism and Base are less common fields. Prism correction is used to help patients who experience double vision or eye alignment issues (such as strabismus). The Base value indicates the direction of the prism. Most prescriptions will have nothing in these columns.

PD (Pupillary Distance): The Fitting Measurement

PD is the distance in millimeters between the centers of your pupils. This measurement is critical because it ensures the optical center of each lens is positioned directly in front of your eye, which affects both clarity and comfort.

You may see your PD listed as a single number (binocular PD, measured across both eyes) or as two separate numbers (monocular PD, measured from the center of each pupil to the bridge of the nose). Both formats are correct; two numbers are increasingly common, especially if you are purchasing glasses online. Our opticians take this measurement in-person when you order frames to ensure the highest accuracy.

Putting It All Together: A Sample Prescription

SPH

CYL

AXIS

ADD

OD (Right)

-2.50

-1.00

090

+2.00

OS (Left)

-2.75

PL / DS

—

+2.00

How to read this sample:

  • Right Eye (OD): Nearsighted (−2.50), with astigmatism (−1.00 CYL at 090 degrees), plus +2.00 ADD power for reading.
  • Left Eye (OS): Nearsighted (−2.75), with no astigmatism (PL/DS in CYL column, no AXIS needed), plus +2.00 ADD power for reading.

Notice that the left eye shows ‘PL/DS’ in the CYL column and a dash for AXIS. This is standard notation for no astigmatism — nothing is missing from the prescription.

Why Your Prescription Is Only Half the Story

Your prescription contains the essential optical numbers, but turning those numbers into the perfect pair of glasses takes the skill of a licensed optician. Our opticians take additional measurements, recommend the best lens materials, coatings, and frame styles for your lifestyle, and ensure your finished glasses are not only optically precise but also comfortable to wear all day.

Frequently Asked Questions

A minus sign in the SPH column means you are nearsighted (myopic), which means you see better up close than at a distance. The further the number is from zero — for example, −4.00 vs. −1.00 — the stronger the nearsightedness correction needed.

SPH stands for Sphere and is the primary lens power needed to correct your distance or near vision. It is measured in diopters. A minus value corrects nearsightedness; a plus value corrects farsightedness. If SPH reads ‘Plano’ or ‘PL,’ no sphere correction is needed.

Plano (sometimes abbreviated PL or written as 0.00) means zero; there is no correction needed in that column for that eye. For example, if your CYL column reads ‘Plano,’ it means you have no astigmatism in that eye. Seeing plano on your prescription is not a concern.

There is no single ‘normal’ prescription; vision correction needs vary widely from person to person. A very mild prescription might be −0.50 SPH with no astigmatism. A stronger prescription might be −5.00 SPH with −2.00 CYL. What matters is that the prescription accurately reflects what your eyes need for clear, comfortable vision.

No. An eyeglass prescription and a contact lens prescription are different documents. Because contact lenses sit directly on the surface of the eye, they require additional measurements, including base curve and diameter, that are determined during a separate contact lens fitting exam. Using your eyeglass prescription to order contacts may result in an ill-fitting, uncomfortable, or unsafe lens.

In Texas, eyeglass prescriptions are typically valid for two years for adult patients, though your doctor may recommend more frequent exams depending on your eye health and how quickly your vision changes. It is important to have a comprehensive eye exam regularly, as vision changes can be gradual and easy to overlook.

PD is traditionally considered a fitting measurement rather than part of the prescription itself, which is why it is not always printed on the prescription form. Our opticians measure your PD in person at the time you select frames, which provides the most accurate result for your specific eyewear. If you need your PD for another purpose, ask our staff and they can provide it.

Blank CYL and AXIS fields simply mean you have no astigmatism in that eye. Some prescriptions will write ‘PL,’ ‘DS,’ or ‘0.00’ in the CYL column instead of leaving it blank — both mean the same thing. Many people have no astigmatism, so this is a common and perfectly normal finding.

A binocular PD is a single number representing the total distance between both pupils measured across the bridge of the nose. A monocular PD is two separate numbers, one for each eye, measuring the distance from each pupil center to the midpoint of the nose. Both formats are correct. Monocular PD values are more precise and are increasingly common, particularly for progressive lens orders or online purchases.

Possibly, though it depends on your specific prescription and the reason for your reading glasses. If you wear reading glasses due to presbyopia, the age-related stiffening of the lens inside the eye, LASIK alone will not eliminate that need, since it corrects the cornea, not the lens. Options like Monovision LASIK or Refractive Lens Exchange (RLE) may be better suited. A comprehensive evaluation with one of our surgeons will help determine the right option for you.

Ready to Turn Your Prescription Into the Perfect Pair of Glasses?

Now that you understand what every number means, our expert opticians are ready to bring your prescription to life. Visit any Berkeley Eye Center Optical location to explore our designer frame collections, advanced lens options, and personalized fitting experience.

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