How to Read Your Prescription for Glasses
Understanding your eye prescription is essential for choosing the right lenses for your glasses. Here’s a breakdown of the key components you’ll typically find on your prescription:
1. What Does OD and OS Mean?
- OD: This stands for Oculus Dexter, which is Latin for right eye.
- OS: This stands for Oculus Sinister, which is Latin for left eye.
So, the OD (right eye) and OS (left eye) will show separate prescription values for each eye.
2. Key Columns on a Prescription: SPH, CYL, Axis
Most prescriptions feature a table with three columns (from left to right):
- SPH (Sphere): This represents the amount of lens power needed to correct nearsightedness (myopia) or farsightedness (hyperopia).
- CYL (Cylinder): This represents the amount of correction required for astigmatism, which occurs due to an irregularly shaped cornea.
- Axis: This refers to the angle (between 0 and 180 degrees) needed for astigmatism correction.
Note: If you don’t have astigmatism, there won’t be any CYL or Axis values on your prescription.
3. SPH: Sphere (Degree or Power)
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SPH (sphere) is the most common part of your prescription, and it tells you how much lens power is required to correct your nearsightedness or farsightedness.
- Minus (-) SPH value: Nearsightedness (myopia): If the SPH value has a negative sign (e.g., -1.00), it means you are nearsighted and need help focusing on distant objects.
- Plus (+) SPH value: Farsightedness (hyperopia): If the SPH value has a positive sign (e.g., +1.00), it means you are farsighted and have difficulty focusing on close-up objects.
4. CYL: Cylinder (Astigmatism)
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CYL (cylinder) indicates the amount of correction you need for astigmatism. Astigmatism occurs when the curvature of your cornea is irregular, causing blurred or distorted vision.
- If no CYL value appears, you do not have astigmatism.
5. Axis: Angle of Astigmatism
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Axis refers to the angle between 1 and 180 degrees that your astigmatism correction needs. It’s necessary only if you have astigmatism (i.e., if you have a CYL value).
- The Axis value tells the optician the precise angle at which to position the cylinder part of the lens.
6. ADD: Addition (For Multifocal Lenses)
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ADD (addition) is a value used for multifocal lenses, such as bifocals or progressive lenses.
- ADD indicates how much magnifying power you need to see closer objects, like reading a book.
- The ADD value is always a positive number (e.g., +1.25, +2.00), and it’s measured in increments of 0.25 diopters.
7. PD (Pupillary Distance)
- PD refers to the distance between your pupils, measured in millimeters. This is important for aligning the center of your lenses with your pupils for optimal vision.
8. Can Eyeglass Prescriptions Be Used for Contact Lenses?
- No, you cannot use your eyeglass prescription to buy contact lenses, as the correction for glasses and contacts differs. Eyeglasses sit about 12-15 mm away from the eyes, while contacts sit directly on your eyes, so the lens power needed is different.
9. How Long Does It Take to Get Prescription Glasses?
- Phifinery Eyewear typically takes about 3 days to complete standard prescription glasses. However, for complex prescriptions, such as high SPH or CYL values, it may take up to 9 days, as custom lenses may need to be made.