Understanding your eyeglass prescription can feel like deciphering a secret code. But don't worry! This comprehensive guide breaks down the terminology and helps you confidently interpret your prescription. Knowing what each part means empowers you to order glasses online or discuss your vision needs effectively with your optician.
Decoding the Numbers and Abbreviations
Your prescription is a precise document detailing your eyes' refractive errors. It's usually divided into sections, each with specific information. Let's examine the key components:
1. OD (Oculus Dexter) and OS (Oculus Sinister)
These Latin abbreviations indicate your right eye (OD) and your left eye (OS). You'll find separate entries for each eye on your prescription.
2. Sphere (SPH)
This refers to your spherical correction, addressing nearsightedness (myopia) or farsightedness (hyperopia).
- Negative numbers (-) indicate myopia (nearsightedness). You can see close objects clearly but have difficulty seeing distant objects.
- Positive numbers (+) indicate hyperopia (farsightedness). You can see distant objects clearly, but struggle with close-up vision.
- 0.00 indicates no spherical correction is needed for that eye.
3. Cylinder (CYL)
This value corrects for astigmatism, an imperfection in the cornea's curvature causing blurry vision at all distances. A 0.00 value indicates no astigmatism correction is needed.
4. Axis (AX)
The axis is paired with the cylinder power and represents the orientation of the astigmatism. It's expressed as a number between 1 and 180 degrees. This value is only relevant if you have a CYL correction (astigmatism).
5. Add
The "Add" power is only present in bifocal or progressive lenses. It represents the additional power added to the distance portion for near vision. It's crucial for comfortable reading and close-up tasks.
6. Prism
A prism correction is rarely needed, used to correct double vision or eye muscle imbalances. It involves both power (e.g., 2 prism diopters) and direction (e.g., base-in, base-out, base-up, base-down).
Example Prescription: Understanding the Details
Let's illustrate with an example:
OD (Right Eye): SPH -1.00 CYL -0.50 AX 100 OS (Left Eye): SPH -0.75 CYL 0.00 AX 000 ADD +2.00 (If this is a bifocal or progressive lens prescription)
This prescription tells us:
- Right Eye (OD): Nearsighted (-1.00 SPH) with slight astigmatism (-0.50 CYL at axis 100).
- Left Eye (OS): Mild nearsightedness (-0.75 SPH) with no astigmatism. The "+2.00 ADD" indicates that this is a bifocal or progressive prescription and the near vision correction is 2 diopters stronger than the distance correction.
Important Considerations
- Your prescription is specific to you. Do not use someone else's prescription.
- Prescriptions expire. Your vision changes over time, so regular eye exams are crucial.
- Consult your eye care professional. If you have any questions or uncertainties about your prescription, always consult your ophthalmologist or optometrist for clarification. They are the best resource to guide you.
By understanding these components, you can navigate your eyeglass prescription with confidence. Remember, though, your eye doctor is always your best resource for any questions about your vision and your prescription. Don't hesitate to contact them if anything seems unclear.
