If you've ever worn glasses, you've probably seen the jumble of letters and numbers that make up your prescription. While these look like mysterious codes, they actually hold the key to crafting the perfect lenses for your eyes. Let's delve into what each part of your prescription means.
Sample prescription form with key areas highlighted
On your prescription, you'll notice two main acronyms, one for each eye:
These terms have a bit of Latin flair, making them sound more complex than they are!
The "Sphere" or SPH column specifies the lens power required to correct your vision. Here's how to interpret it:
Lens power is measured in diopters, denoted as D. For instance, if you see −9.00 D in the SPH field, you have 9 diopters of nearsightedness. Imagine this as a number line, with zero being perfect vision. The farther you stray from zero, the stronger your prescription needs to be.
The CYL number relates to astigmatism, a condition where the eye's curvature isn't perfectly round. Picture a normal eye as a basketball, maintaining the same curve no matter how you rotate it. An eye with astigmatism resembles an egg or a North American football—having different curves along different axes. The CYL value adjusts for this discrepancy, giving you clear vision.
The Axis is a number between 1 and 180 that pinpoints where astigmatism is located on your cornea. It tells you the angle at which the astigmatism lines up, guiding the correction to where it's needed.
The Add field is where additional lens powers are listed. For those over 40 who don't want to juggle multiple pairs of glasses, bifocals are a popular choice. The lower portion of these lenses assists with reading, providing clarity for close-up tasks.
Some prescriptions include a section for prism, a specialized correction for individuals experiencing double vision (seeing two images of the same object). The prism merges these images into one, offering a clear, singular view.
Contact lenses require a different prescription than eyeglasses because they sit directly on the eye. A contact lens prescription includes specific measurements for size and brand, ensuring a proper fit. Before getting contacts, you'll need a "contact lens fitting" to determine the best options for your eyes.
Our optical experts are here to help you understand your prescription and find the perfect frames.
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