How to Read Your Glasses Prescription

How-to10 min read

By Shaheen Arif, Founder and Editor · Editorially reviewed by Talha N. Ch for clarity, sourcing and product-claim accuracy · About us · Updated November 12, 2026

Quick answer

Learning how to read your glasses prescription means matching each abbreviation to what it measures. OD is your right eye and OS is your left eye. SPH shows lens power with a plus or minus sign. CYL and AXIS describe astigmatism correction, ADD covers reading power, and PD is the distance between your pupils. Once you can identify these values, compare them to any frame or lens listing before placing an order.

Confirm OD and OS are clearly labeled and not reversed
Check that SPH values include a plus or minus sign
Look for CYL and AXIS appearing together, or both left blank
Verify a PD number is listed or plan to get one separately
Note the issue date and any expiration date
Check for a prism row if your prescription mentions double vision correction

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Key takeaways

A plus sign on sphere power generally relates to farsightedness and a minus sign to nearsightedness.
Contact lens prescriptions include values like base curve and diameter that do not apply to glasses orders.
Pupillary distance is sometimes measured separately by an optician and may not appear on the printed prescription at all.
Axis numbers only appear when a cylinder value is also listed, since axis describes the orientation of astigmatism correction.
Prism correction, when prescribed, uses its own notation with a direction abbreviation and is less common than sphere or cylinder values.

What you need

A copy of your current eye prescription, printed or as a PDF
A ruler or printed PD tool if pupillary distance is not listed
Your current glasses, for comparing existing frame measurements
A notepad or phone to record values accurately
Internet access if you plan to order frames or lenses online afterward

Step-by-Step Instructions: How to Read Your Glasses Prescription

Common abbreviations found on a glasses prescription
Abbreviation	What it describes
OD	Right eye (oculus dexter)
OS	Left eye (oculus sinister)
SPH	Sphere, the main lens power
CYL	Cylinder, astigmatism correction strength
AXIS	Orientation of astigmatism correction, 1 to 180
ADD	Added power for reading or multifocal lenses
PD	Pupillary distance between pupils

Find the OD and OS rows. Some offices write out "right eye" and "left eye" instead of Latin abbreviations. Confirm which row sits on top before recording any numbers.
Read the SPH column for each eye. Note whether the number has a plus or minus sign, since that sign changes the lens type needed.
Check the CYL and AXIS columns together. If CYL has a value, AXIS should also be filled in. If both are blank, no astigmatism correction was prescribed.
Look for an ADD value. This usually applies to reading or multifocal lenses and is often the same number for both eyes.
Locate your PD. It may be a single number or two numbers split for near and distance vision. If it's missing, you can check our guide to checking glasses frame fit for how PD affects sizing, or ask the issuing office to measure it.
Scan for a prism notation, usually a small number followed by a direction letter. This is less common and applies only if double vision correction was prescribed.
Confirm the issue date and any expiration date printed on the document. Validity periods vary by state and by age, so check this before ordering.
Once every field is recorded, you're ready to shop. Review how to buy prescription glasses online safely before entering your numbers, then browse options such as prescription glasses from Eydology.

Safety checks

Confirm the prescription has not expired before placing an order
Double-check that OD and OS values are not swapped when entering an online order form
Verify the plus or minus sign on SPH carried over correctly from the original document
If CYL or AXIS appears incomplete, contact the issuing office before finalizing an order
Stop and consult an eye care professional if you notice sudden vision changes, since reading an older prescription does not address new symptoms

Common mistakes

Swapping OD and OS: entering left-eye numbers in the right-eye field can result in blurred vision; re-check the row labels before submitting any order.
Dropping the sign on SPH: treating a positive number as negative changes the lens power entirely; copy the sign along with the number every time.
Leaving PD blank: some order forms default to an average value when PD is missing, which may not match your eyes; get PD measured and enter it manually.
Using an expired prescription: lenses made from outdated values may not match your current vision; check the issue and expiration dates first.
Confusing a contact lens prescription with a glasses prescription: values like base curve and diameter apply only to contacts; for lens shopping, use the contact lens options page only when you have a contact-specific prescription.
Missing the ADD row: skipping this field can lead to ordering single-vision lenses when multifocal correction was prescribed; scan the full form, not just the main SPH/CYL grid.
Ignoring prism notation: this specialty correction is easy to overlook if you only check the main columns; review the entire document before ordering.

Troubleshooting

My prescription doesn't list a PD number?

This usually happens when the measuring office didn't record pupillary distance on the printed form. Ask the issuing office for the number, or use a PD measurement method recommended by an optician before ordering frames online.

I can't tell which number is OD and which is OS?

Some offices write "right eye" and "left eye" in full instead of using Latin abbreviations. OD typically appears first or on the top row of most standard prescription layouts, but confirm the order with the issuing office if the form looks unusual.

There's a dash or blank space in the CYL or AXIS columns?

A blank CYL or AXIS field generally means no astigmatism correction was prescribed for that eye. This is normal and does not indicate an incomplete prescription.

The ADD column only shows one number?

A single ADD value commonly applies to both eyes equally. Use that same number for each eye when entering your prescription into an online order form, unless the document specifies otherwise.

Limitations and checks

Prescription formats vary between eye doctors, states, and clinics, so always verify unfamiliar abbreviations with the issuing office rather than guessing. Expiration rules for glasses prescriptions also vary by state and by patient age, and this article cannot confirm the specific rule that applies to your situation. This content offers general education and is not a substitute for a professional eye exam or individualized advice from an eye care provider. It also cannot confirm how any particular retailer's order form will interpret your entered values, so review the retailer's instructions and double-check your entries before completing a purchase. No hands-on testing of any linked frames took place; verify current specifications, fit, and policies directly on each retailer page.

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Products and prices from Eydology, checked on November 12, 2026. Prices and availability can change; confirm on the retailer's page.

Verified product details

Copied from each retailer's product data on November 12, 2026. We did not test these products. Confirm sizes, compatibility, included accessories and other specifications on the official product page before you buy.

Retailer-listed details for the products in this guide
Model	What the retailer lists	Price checked	Official page
Gage - Black - Non-Prescription Blue Light	Not listed in the retailer product data	$9.99	Check Gage - Black - Non-Prescription Blue Light at Eydology
Gage - Tortoise - Non-Prescription Blue Light	Not listed in the retailer product data	$9.99	Check Gage - Tortoise - Non-Prescription Blue Light at Eydology
Naomi - Black - Non-Prescription Blue Light	Not listed in the retailer product data	$20.95	Check Naomi - Black - Non-Prescription Blue Light at Eydology
Quentin - Black - Non-Prescription Blue Light	Not listed in the retailer product data	$20.95	Check Quentin - Black - Non-Prescription Blue Light at Eydology

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Bottom line

Reading a glasses prescription comes down to matching a short list of abbreviations, OD, OS, SPH, CYL, AXIS, ADD, and PD, to what each one measures, then checking the issue date before you order anything. Once you've recorded every value correctly, you're ready to compare frame measurements or shop lens options with confidence. For a next step, review frame fit basics, then browse prescription-ready options like Dina or Shena, or check the broader Dima Eyewear best sellers list if you want more styles to compare against your recorded numbers.

Frequently asked questions

What does OD and OS mean on a glasses prescription?

OD stands for oculus dexter, meaning right eye, and OS stands for oculus sinister, meaning left eye. These labels appear as row or column headers on most prescription forms, and keeping them straight matters because lens powers are usually different for each eye.

What's the difference between SPH and CYL?

SPH, or sphere, is the main lens power used to correct overall nearsightedness or farsightedness. CYL, or cylinder, is an additional value that corrects astigmatism, and it only appears alongside an AXIS number when astigmatism correction is needed.

Why doesn't my prescription have a PD listed?

Not every eye care office measures pupillary distance as part of a standard exam, since it is sometimes handled separately when fitting frames in person. If PD is missing, ask the issuing office for the measurement or use a PD tool before ordering glasses online.

Can I use my contact lens prescription to buy glasses?

No, a contact lens prescription includes values like base curve and diameter that apply only to contacts and do not translate directly to glasses lens power. Use a glasses-specific prescription when ordering eyeglasses, and a contact lens prescription only for contact lens purchases.

How long is a glasses prescription valid?

Validity periods vary depending on the issuing state and the patient's age, with some prescriptions valid for a year or two. Check the expiration date printed on your document, and if none appears, confirm the valid period directly with the issuing office.

What does ADD mean on a prescription?

ADD refers to added magnifying power used for reading or multifocal lenses, separate from the main sphere correction. It typically appears as a single positive number and is often the same value for both eyes.

What if my axis number is missing?

A missing axis number is expected when the CYL field is also blank, since axis only applies when astigmatism correction is prescribed.

Is a negative or positive sphere worse?

Neither sign indicates a more serious condition on its own; a minus sign generally relates to nearsightedness and a plus sign to farsightedness. The number itself, not the sign, reflects the strength of correction needed, and only an eye care professional can interpret what a specific value means for your vision.

Sources and further reading

Independent references on topics covered in this guide. We are not affiliated with these organizations.

Official product pages: manufacturer and retailer pages for the specifications above. These are partner links: we may earn a commission.

Eydology: Gage - Black - Non-Prescription Blue Light product page
Eydology: Gage - Tortoise - Non-Prescription Blue Light product page
Eydology: Naomi - Black - Non-Prescription Blue Light product page
Eydology: Quentin - Black - Non-Prescription Blue Light product page

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