Sph and Cyl are terms used in eyeglass prescriptions to denote the lens power needed to correct vision. Let's break down what each means:
Understanding Sph (Sphere)
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Definition: Sph, or sphere, represents the degree of nearsightedness or farsightedness. It measures the overall refractive error of your eye.
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Values:
- A negative (-) number (e.g., -1.00, -2.50) indicates nearsightedness (myopia), meaning you see close objects clearly but distant objects appear blurry.
- A positive (+) number (e.g., +1.00, +2.50) indicates farsightedness (hyperopia), meaning you see distant objects clearly but close objects appear blurry.
- A zero (0.00) value means that no spherical correction is needed.
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Strength: The higher the number (regardless of whether it's positive or negative), the stronger the lens required.
Understanding Cyl (Cylinder)
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Definition: Cyl, or cylinder, measures the amount of astigmatism in your eye. Astigmatism occurs when the cornea or lens of the eye is not perfectly spherical, causing blurred vision at all distances.
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Values: The cylinder value will typically be a negative number. A value of zero (0.00) means that there is no astigmatism.
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Axis: The cylindrical power also includes an axis, usually a number between 1 and 180. This axis indicates the orientation of the astigmatism.
How Sph and Cyl Work Together
Your eye prescription will combine these values to provide the best visual correction. A typical prescription might look something like this:
| Sph | Cyl | Axis | |
|---|---|---|---|
| R | -2.00 | -1.00 | 90 |
| L | +1.50 | -0.50 | 180 |
This example shows that:
- Right Eye (R): Requires -2.00 for nearsightedness correction and -1.00 cylinder correction for astigmatism at a 90-degree axis.
- Left Eye (L): Requires +1.50 for farsightedness correction and -0.50 cylinder correction for astigmatism at a 180-degree axis.
Practical Insights
- Regular eye exams are crucial for monitoring changes in your Sph and Cyl values.
- Understanding these values helps you make informed decisions about your eye health and vision correction options.
- The higher the Sph and Cyl values, the stronger the prescription needs to be.
- If you have astigmatism you will always have a cyl and axis number in your prescription
