Eyeglasses Prescription

Eyeglasses Prescription

Getting a spectacles prescription is the first step towards improving your vision. After an eye examination, your optometrist might mention that you are long-sighted, short-sighted, or you have astigmatism. So what do the numbers on the Eyeglasses Prescription mean? What do the abbreviated terms mean in full? In this post, you will learn how to decipher the various parts of a spectacles prescription so that you can discuss the prescription knowledgeably with an optical shop or optician near you when buying glasses.  


What are OD and OS On Eyeglasses Prescription?

Understanding your eyeglasses prescription starts with decoding the abbreviations. The primary ones are OD and OS, which stand for oculus dexter and oculus sinister, respectively, representing the right and left eyes. Additionally, you might encounter OU, denoting oculus uterque for both eyes.

These Latin abbreviations are customary in eyeglasses prescriptions for various optical corrections, including those for contact lenses and spectacles.

Here’s a breakdown of other crucial details found in an eyeglasses prescription:

  1. SPH (Sphere): Indicates the lens power measured in diopters (D), addressing conditions like nearsightedness or farsightedness. A plus sign indicates farsightedness, while a minus sign signifies nearsightedness. The term “Sphere” denotes a uniform correction across all meridians of the eye.

  2. CYL (Cylinder): Specifies lens power for correcting astigmatism. Absence in this column suggests no or minimal astigmatism requiring correction. The “Cylinder” refers to the non-spherical lens power needed for astigmatism correction. The sign (plus or minus) indicates the type of astigmatism being corrected, following the SPH value in the prescription.

  3. Axis: Indicates the meridian of the lens without cylinder power. It ranges from 1 to 180, with 90 representing the vertical meridian and 180 the horizontal. When astigmatism correction is present, the axis value follows the CYL power, often denoted by an ‘X.’

  4. Add: Reflects additional magnifying power for multifocal lenses in correcting presbyopia. The number is always positive, typically ranging from +0.75 to +3.00 D, and remains consistent for both eyes.

  5. Prism: Measures prismatic power in prism diopters (p.d.) or indicated by a superscript triangle. It addresses issues with eye alignment, though it’s included in only a small percentage of prescriptions. Prism direction is abbreviated as BD (base down), BU (base up), BO (base out), and BI (base in).

These values are typically expressed in increments of 0.25 D for SPH, CYL, and ADD, while the axis represents whole numbers. Prism diopters may appear as decimals, with one digit following the decimal point.

It’s important to note that eyeglasses prescriptions differ from contact lens prescriptions. Spectacle prescriptions are tailored for purchasing glasses exclusively, while contact lenses require a separate prescription.

Following an eye examination, your optometrist will furnish you with your eyeglasses prescription. Should you require assistance, feel free to reach out to us at Optician on Wheels, where we provide convenient lens and frame solutions delivered directly to your home or office. Contact us today to learn more about our services.

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