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Your prescription
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Decoding Your Eyewear Prescription
Understanding your prescription
Understanding your eye exam prescription is essential for ensuring you get the right vision correction. Here’s a breakdown of the key terms you’ll find on your prescription
Sphere (SPH)
What It Means
Positive or Negative
Positive (+) Numbers: Indicate farsightedness (hyperopia). Distant objects appear clear, but nearby objects are blurry. Glasses with this prescription help you see up close, such as when reading a book.
Negative (-) Numbers: Indicate nearsightedness (myopia). Nearby objects appear clear, but distant objects are blurry. Glasses with this prescription help you see far away, like reading a street sign.
The higher the value of the + or – number, the stronger your prescription is.
Cylinder (CYL) and Axis
What It Means
These values indicate astigmatism, a condition where the eye’s curvature is uneven, causing blurry or distorted vision at any distance. The CYL measures its severity, while the Axis pinpoints the orientation of the irregularity.
Positive or Negative
Proper correction ensures sharp, clear vision by compensating for the uneven curvature. Without it, everyday tasks like reading or driving may become challenging due to persistent blur or distortion.
Add
What It Means
This value indicates the additional lens power needed for near vision, typically for people with presbyopia. It helps address presbyopia, a natural age-related condition that makes focusing on nearby objects more difficult. The Add value is important to make progressive lenses.
Why It Matters
The ADD correction ensures clear, comfortable vision for activities like reading or using a phone. Without it, close-up tasks may cause eye strain or blurred vision, affecting everyday convenience and productivity.
PRISM
What It Means
Prism correction is used when your eyes don’t work together perfectly, such as in cases of eye misalignment. It helps your eyes focus better as a team, reducing double vision and improving overall clarity. The prism strength is indicated by a number, such as “2,” which shows how much correction is needed.
Prism Directions
The letters—like “BO” (base out), “BI” (base in), “BU” (base up), or “BD” (base down)—tell the eye doctor the direction to position the prism in your glasses. This ensures the correction aligns properly, allowing your eyes to work together seamlessly.
Example Prescription Breakdown
In this example
The BASE refers to the position of the thickest edge of the prism and is crucial in correcting double vision.
- The right eye has moderate nearsightedness with mild astigmatism corrected at a 180-degree axis, an additional +2.5 magnification for near vision, and a 2-diopter base-out (BO) prism to assist eye alignment.
- The left eye also has stronger nearsightedness with moderate astigmatism corrected at a 90-degree axis, an additional +2 magnification for near vision, and a 2-diopter base-in (BI) prism to assist eye alignment.
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