How to Read an Eyeglass Prescription and Understand SPH, CYL and AXIS
If your prescription shows OD, OS, SPH, CYL, AXIS and ADD, do not look for one number and call it your entire prescription. Each field describes a different part of the correction, so copy the values exactly as written.
Keep the original prescription beside you before opening LensCode Eyeglasses. If a field is unclear, use the current prescription-submission options instead of guessing.
Read the prescription in this order
- Confirm OD and OS, or R and L.
- Read SPH with its + or - sign.
- If CYL appears, read AXIS with it.
- Check ADD if present.
- Treat PD as a fitting measurement, not lens power.
- Transfer numbers and signs exactly.
How do you read an eyeglass prescription?
Start with the eye label, then SPH, CYL and AXIS where present, followed by ADD, PD and any Prism entry. Keep the prescription open while using LensCode's online pre-order checks.
Start with OD and OS
OD means right eye and OS means left eye. Some prescriptions use R / Right and L / Left; OU may refer to both eyes. Check the labels rather than assuming the row order.
What does SPH mean and why does the plus or minus sign matter?
SPH means Sphere: spherical lens power in diopters. Minus commonly relates to myopic correction and plus to hyperopic correction. The sign is part of the value: -2.00 is not +2.00. A plus SPH does not automatically mean “reading glasses.”
SPH
Spherical power.
Not the whole prescription alone.
CYL
Cylinder power when prescribed.
Not the AXIS value.
AXIS
Cylinder orientation.
Not astigmatism strength.
What does CYL mean?
CYL means Cylinder: cylindrical power where astigmatic correction is prescribed. It can appear in minus- or plus-cylinder notation, so professionally transposed prescriptions can look different while representing equivalent correction. Do not transpose it yourself; enter the version you were given.
What does AXIS mean?
AXIS gives the orientation of the cylinder correction, usually from 0 to 180 degrees. AXIS 180 is not stronger than AXIS 90. CYL gives cylindrical power; AXIS gives its orientation.
Why do SPH, CYL and AXIS work together?
A prescription may not have one single “eye number.” If CYL and AXIS are present, SPH alone is incomplete. If a new pair feels wrong, do not change values from symptoms; use the new-glasses recheck guide.
What does ADD mean?
ADD means Near Addition: extra near power when applicable. It may appear with Reading, Progressive, Bifocal or other multifocal correction. ADD is not automatically the finished reading-glasses prescription and should not be used for DIY calculations.
What does PD mean and is it part of lens power?
PD, or Pupillary Distance, helps centre the lenses horizontally. It is not refractive power like SPH, CYL or ADD. Some prescriptions include it and some dispensing processes record it separately. Do not guess PD when it is required.
ADD
Additional near power.
Not a complete reading Rx alone.
PD
Lens-centration measurement.
Not prescription strength.
Prism / Base
Prismatic correction and direction.
Do not modify it yourself.
What do Prism and Base mean?
Prism records prescribed prismatic correction; Base describes its direction. Copy both exactly if shown. VA, or Visual Acuity, may also appear, but it records acuity information rather than lens power.
| Field | Meaning | How it appears | Key warning |
|---|---|---|---|
| OD / OS | Right / left eye | Eye rows | Do not swap |
| SPH | Spherical power | + or - D | Keep sign |
| CYL | Cylinder power | + or - | Do not transpose |
| AXIS | Cylinder orientation | Degrees | Not strength |
| ADD | Near addition | Extra value | Not full Rx alone |
| PD | Pupillary distance | mm | Fitting measure |
| Prism / Base | Prism / direction | Dedicated fields | Do not guess |
Example of how to read an eyeglass prescription
For education only — not a prescription to use.
SPH -2.00
CYL -0.75
AXIS 90
ADD +1.50
SPH -1.50
CYL -0.50
AXIS 80
ADD +1.50
The example only shows where each field belongs. It does not recommend lenses.
Prescription values vs fitting measurements
SPH, CYL, AXIS, ADD and Prism describe correction. PD, fitting height and design-specific positioning data relate to fitting and centration. Keep those decisions separate with the Office Glasses guide and Prescription vs Computer Glasses.
Do not confuse PD with 52-18-140 frame measurements
52-18-140 usually describes lens width, bridge width and temple length. It is not PD. Use the frame-size guide for that separate topic.
Can an eyeglass prescription be used for contact lenses?
No. A contact-lens prescription can include fitting and product parameters such as BC and DIA. Do not copy an eyeglass Rx directly into a contact-lens order. Use LensCode's Prescription Contact Lenses guide before browsing contact lenses.
| Term | Belongs to | Part of eyeglass Rx? |
|---|---|---|
| SPH | Optical correction | Yes |
| ADD | Near correction | When prescribed |
| PD | Fitting / centration | May appear with it |
| Frame Size | Frame dimensions | No |
| BC | Contact-lens fitting | Not normally |
| DIA | Contact-lens diameter | Not normally |
How to enter your prescription through LensCode
LensCode currently lets customers upload a prescription image on the eyeglass product journey or send it to the optician through WhatsApp. The FAQ confirms the route, while the Terms place responsibility on the customer for accurate prescription details.
Before sending your prescription to LensCode
- OD and OS are correct.
- SPH keeps its sign.
- CYL keeps its sign if present.
- AXIS matches the original.
- ADD is copied only if shown.
- PD is not guessed.
- 52-18-140 is not used as PD.
- A glasses Rx is not used for contacts.
- Attach the prescription image when useful.
- Review values before checkout.
If something remains unclear, use LensCode support instead of entering a likely value, then repeat the final order check.
Common mistakes when copying a glasses prescription
Frequently asked questions about eyeglass prescriptions
What does SPH mean?
Spherical lens power in diopters, including its sign where applicable.
What do CYL and AXIS mean?
CYL is cylinder power; AXIS is its orientation.
Is AXIS astigmatism strength?
No. AXIS is orientation; CYL records cylindrical power.
What does ADD mean?
Additional near power when prescribed, not a complete reading Rx by itself.
What does PD mean?
Pupillary Distance helps centre lenses; it is not prescription power.
Is a glasses Rx the same as a contact-lens Rx?
No. Contact-lens prescriptions can include BC, DIA and other fitting or product data.
Check your prescription in under a minute
Confirm OD / OS
↓
Copy SPH with its sign
↓
CYL present? Copy CYL + AXIS
↓
ADD present? Copy it exactly
↓
PD required? Do not guess
↓
Check the original prescription
↓
Enter details in LensCode
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Review the order
Once the fields are clear, choose your frame and submit the prescription exactly as written, or use the current upload route before reviewing the order.
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