It can be difficult to understand your glasses prescription with all the acronyms and numbers. But understanding these components is essential to getting the right glasses for your eyesight requirements.
This step-by-step guide to read glasses prescription will help you navigate the components of a typical prescription, making it easier to understand what each part means and how it affects your vision correction.
Step 1: Understanding the Basic Terms
Before diving into the specifics of your prescription of prescription glasses, it’s important to familiarize yourself with some basic terms:
- OD (Oculus Dexter): Refers to the right eye.
- OS (Oculus Sinister): Refers to the left eye.
- OU (Oculus Uterque): Refers to both eyes.
These Latin terms are standard in optometry and help distinguish between the prescriptions for each eye.
Step 2: Decoding Sphere (SPH)
The sphere value, abbreviated as “SPH,” indicates the lens’s power needed to correct nearsightedness or farsightedness. Here’s what you need to know:
- A positive (+) sign before the number: Indicates farsightedness (hyperopia). For example, +2.00 means you need lenses that converge light rays to help you see nearby objects more clearly.
- A negative (-) sign before the number: Indicates nearsightedness (myopia). For example, -1.50 means you need lenses that diverge light rays to help you see distant objects more clearly.
The higher the number, the stronger the prescription lenses required to correct your vision.
Step 3: Understanding Cylinder (CYL)
The cylinder value, abbreviated as “CYL,” indicates the degree of astigmatism, which is caused by an irregularly shaped cornea. This value can be positive or negative and shows the amount of lens power needed to correct astigmatism.
- No cylinder value: If there’s no number in the CYL column, it means you have no astigmatism or it’s so minimal that correction isn’t necessary.
Step 4: Interpreting Axis
The axis value, represented as a number between 1 and 180, describes the orientation of astigmatism. It indicates where the lens power correction should be applied to correct the irregular curvature of the cornea.
- Horizontal (0 to 180 degrees): The number specifies the position of the cylindrical power on the lens, helping to orient it correctly to improve vision.
For example, if your prescription shows CYL -1.00 and Axis 180, it means that there is a cylindrical correction of -1.00 diopters, and it needs to be positioned at the 180-degree axis.
Step 5: Reading the ADD Value
The “ADD” value, often listed in bifocal or multifocal prescriptions, indicates the additional magnifying power needed for reading or close-up work. This value is usually the same for both eyes and is always positive, even if the SPH values are negative.
Example: If your ADD value is +2.50, this means an additional 2.50 diopters of magnification are needed for near vision.
Step 6: Understanding Prism and Base
In some cases, your prescription may include a prism correction, which is used to address binocular vision issues, such as double vision. The prism value indicates the amount of prismatic power needed, measured in prism diopters, to align your eyes properly.
- Base Direction: The “base” direction indicates the position of the thickest edge of the prism and can be up, down, in (towards the nose), or out (towards the ear).
For example, “2.0 Base Up” means a 2.0 prism diopter correction with the base of the prism positioned upward.
Step 7: Pupillary Distance (PD)
The distance measured between the centers of your pupils is called the pupillary distance, or PD. It is crucial for correctly aligning the lenses in your glasses with your eyes. PD can be:
- Monocular PD: Measured separately for each eye, indicating the distance from the center of the bridge of the nose to each pupil.
- Binocular PD: The total distance between the centers of each pupils is known as the binocular PD.
PD is measured in millimeters and ensures that you are looking through the optical center of the lenses.
Step 8: Other Considerations
Lens Type
Depending on your vision needs, your prescription might indicate a specific type of lens, such as single vision, bifocals, or progressives. Single vision lenses correct for one field of vision (near or distance), while bifocals and progressives correct for both near and distance vision.
Lens Coatings
Your optometrist may also recommend lens coatings, such as anti-reflective (AR) coating, UV protection, or blue light filtering. These coatings can enhance the functionality and comfort of your glasses.
Learn more: Understanding and Exploring What 20/20 Vision Means?
Connect with Vision Gallery
Reading and understanding your glasses prescription is crucial for ensuring you receive the correct lenses to improve your vision. By familiarizing yourself with the terms and values used in the prescription, you can make more informed decisions about your eyewear and better communicate with your optometrist or eyewear provider.
At Vision Gallery, we are dedicated to helping you achieve optimal vision and comfort with the right eyewear. If you have any questions about your prescription or need assistance in choosing the perfect pair of glasses, our experienced team is here to help. Contact Vision Gallery today to schedule an eye exam or consult with our experts about your eyewear needs.
