If you’ve just done an eye exam and received your prescription, you’re likely staring at a piece of paper filled with strange abbreviations and numbers: OD, OS, SPH, CYL, Axis, ADD, PD—what do they all mean?
Don’t worry. Whether you’re buying glasses for the first time or switching brands, this simplified guide will walk you through everything you need to know about interpreting your glasses prescription with confidence.
What Do OD and OS Mean?
These are Latin abbreviations used in optometry:
- OD (Oculus Dexter): Right eye
- OS (Oculus Sinister): Left eye
- Occasionally, you may also see OU (Oculus Uterque), which refers to both eyes.
These labels tell you which measurements belong to which eye.
SPH (Sphere): Correcting Nearsightedness or Farsightedness
- This value shows the lens power needed to correct myopia (nearsightedness) or hyperopia (farsightedness).
- It’s measured in diopters (D).
- A minus sign (-) means you’re nearsighted (you struggle with distance vision).
- A plus sign (+) means you’re farsighted (you struggle with close-up vision).
Example:
SPH -2.00 = Mild to moderate nearsightedness
SPH +1.50 = Mild farsightedness
CYL (Cylinder): Do You Have Astigmatism?
- This number appears if you have astigmatism—an irregularly shaped cornea or lens.
- Like SPH, it’s measured in diopters and can have a + or – value.
- If this box is blank, you likely don’t have significant astigmatism.
Example:
CYL -1.00 means a mild level of astigmatism.
Axis: Direction of Astigmatism Correction
- Always paired with CYL.
- Measured in degrees (0 to 180).
- It tells the orientation of the astigmatism in your eye.
Example:
Axis 90 means the correction is vertical.
Axis 180 means it’s horizontal.
ADD: Extra Help for Reading or Computer Use
- This is an additional magnifying power prescribed for reading glasses or progressive lenses.
- Mostly given to people over 40 experiencing presbyopia (age-related near vision loss).
- ADD is usually a +1.00 to +3.00 range.
Example:
SPH +1.50, ADD +2.00 = You need help with both general vision and reading.
PD (Pupillary Distance): Getting the Lens Alignment Right
- PD is the distance between the centers of your pupils, measured in millimeters.
- It ensures your lenses are properly centered in your frames.
- Adults’ PD ranges from 54mm to 74mm.
- You might see:
- A single PD: for single-vision lenses.
- A dual PD: separate values for right and left eyes, especially in progressive lenses.
- A single PD: for single-vision lenses.
Example:
PD 62mm or PD 31/31 (R/L)
VA (Visual Acuity): Measuring How Well You See
- Sometimes written as 6/6, 20/20, or 6/12, depending on your region.
- A 6/6 (or 20/20) score means normal vision.
- A 6/12 means you need to stand at 6 meters to see what a person with normal vision can see at 12 meters.
How to Read a Full Sample Prescription
| Eye | SPH | CYL | Axis | ADD | VA |
| OD | -2.50 | -1.00 | 180 | +2.00 | 6/6 |
| OS | -2.25 | -0.75 | 175 | +2.00 | 6/6 |
| PD: 62mm |
What it means:
You’re nearsighted in both eyes, with mild astigmatism. You also need extra power for reading. PD ensures lenses align perfectly.
Common Questions First-Time Buyers Ask
1. Can I use the same prescription for contact lenses and glasses?
No. Contact lens prescriptions account for lens curvature and position on the eye. Always get a separate contact lens fitting.
2. How long is my glasses prescription valid?
Usually 1–2 years, depending on your age and eye health. Kids and seniors may need more frequent updates.
3. What if my SPH and CYL values are very different in each eye?
That’s not uncommon. Your optician may recommend custom lenses or high-index materials to ensure balance and comfort.
Tips When Ordering Glasses Online
- Double-check your PD measurement
- Make sure to enter all prescription details correctly
- Ask for anti-glare or blue-light filters if you’re on screens often
- If you have astigmatism, choose lenses with precise axis alignment
FAQs :
- What do SPH and CYL mean in my glasses prescription?
*SPH (Sphere) corrects nearsightedness (-) or farsightedness (+). CYL (Cylinder) indicates astigmatism strength, with Axis showing its orientation (0-180°).* - How do I find my pupillary distance (PD) for glasses?
*PD is the distance between pupils (in mm). Opticians usually measure it, but you can self-measure using a ruler or apps (54-74mm is typical for adults).* - Can I use my glasses prescription for contact lenses?
No—contact lens prescriptions include additional measurements like curvature. Always get a separate fitting for contacts. - What does “ADD” mean on my prescription?
*ADD is extra magnifying power (+1.00 to +3.00) for reading or progressive lenses, typically for presbyopia (age-related near vision loss).* - How long is a glasses prescription valid?
*Usually 1-2 years. Children, seniors, or those with eye conditions may need updates sooner. Check local regulations for expiry rules.*
Final Thoughts: Your Prescription Is Your Blueprint
Understanding your eyewear prescription helps you make smarter choices when selecting lenses—whether you’re ordering online or in-store. It’s not just about numbers; it’s about finding clarity, comfort, and style tailored to your needs.
If you’re unsure which lens suits your prescription and lifestyle best, ask your optician about options like Platinum lenses that offer advanced coatings, digital precision, and lifestyle-based designs.
