Understanding your eyeglass prescription might seem daunting at first, but it's a valuable skill that empowers you to communicate effectively with your eye care professional and ensure you get the right glasses. This guide breaks down the common components of an optical prescription, helping you decipher the numbers and abbreviations.
Deciphering the Jargon: Key Components of Your Prescription
Your prescription contains several crucial pieces of information, all essential for accurate lens fabrication. Let's dissect them:
1. OD (Oculus Dexter) and OS (Oculus Sinister):
These abbreviations refer to your right eye (OD) and your left eye (OS) respectively. Your prescription will list the details for each eye separately.
2. Sphere (SPH):
This indicates the power of the lens needed to correct your myopia (nearsightedness) or hyperopia (farsightedness).
- Negative numbers (-) correct myopia (nearsightedness). The higher the negative number, the stronger the correction needed.
- Positive numbers (+) correct hyperopia (farsightedness). The higher the positive number, the stronger the correction needed.
- 0.00 indicates no correction is needed for spherical refractive error.
3. Cylinder (CYL):
This value addresses astigmatism, a refractive error causing blurred vision at all distances. It represents the power of the cylindrical correction needed to counteract the uneven curvature of your cornea. A value of 0.00 means you don't have astigmatism.
4. Axis (AXIS):
The axis is used in conjunction with the cylinder power. It specifies the orientation of the astigmatism correction on the lens, expressed in degrees (ranging from 1 to 180). This is crucial for precise correction.
5. Add:
This value is only present in bifocal or progressive lens prescriptions. It indicates the power added to the distance portion of the lens for near vision correction (reading).
Example Prescription and Explanation:
Let's consider a sample prescription:
Right Eye (OD):
- SPH: -2.00
- CYL: -0.75
- AXIS: 170
Left Eye (OS):
- SPH: -1.50
- CYL: 0.00
- AXIS: —
Interpretation:
- Right Eye (OD): This eye has moderate myopia (-2.00) and mild astigmatism (-0.75 at 170 degrees).
- Left Eye (OS): This eye has mild myopia (-1.50) but no astigmatism.
Beyond the Basics: Other Prescription Details
Your prescription might also include other details, such as:
- Prism: Corrects for double vision.
- Pupillary Distance (PD): Measures the distance between the centers of your pupils. This is crucial for proper lens alignment. It's often split into right and left PD measurements (e.g., Right PD: 30mm, Left PD: 32mm, Total PD: 62mm).
Why Understanding Your Prescription Matters:
Knowing how to interpret your prescription allows you to:
- Verify the accuracy of your glasses. Double-check the values against your prescription to ensure your new glasses match the specifications.
- Communicate effectively with your eye doctor or optician. This facilitates clear communication and ensures you receive the appropriate eyewear.
- Order glasses online safely (although we always recommend getting an in-person eye exam)
