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How To Read Your Glasses Prescription

If you just left the eye doctor and you’re looking at a glasses prescription, it might look like complete gibberish. It’s not just the dilated pupils you might have — the notations your doctor may have made are likely full of abbreviations and numbers that probably won’t make sense unless you have a background in ophthalmology.

Luckily, we’re here to crack the code on your eyeglass prescription. Read on for a breakdown of the most common elements in a prescription, as well as what your diagnosis might mean.

What Are the Elements in a Glass Prescription?

In order to truly understand your diagnosis, you’ll need to learn to read your glasses prescription. This way, you can see exactly what sort of correction your eye doctor has recommended for you based on your eye exam.

OD vs. OS Eye

One of the first things you’ll notice on your eyeglasses prescription is something called OD and OS Eye. These stand for oculus dexter, or right eye, and oculus sinister, or left eye.

It may come as a surprise that your eyes each have a different prescription, but it’s actually quite common to have a strong eye and a weak eye. This is usually because there might be a slight difference in the shape or size of your eyes.

Sphere (SPH)

If you see a sphere on your eyeglasses prescription, your ophthalmologist will be using a sphere for your vision correction. If you’re just nearsighted or farsighted, you’ll likely need a sphere-shaped correction on your lens.

You’ll also see some numbers along with your SPH prescription. These numbers mean you’ll need extra lens power to correct your vision.

Sphere can be either positive or negative, depending on your prescription. A positive sphere means that you’re farsighted, while a negative sphere means that you’re nearsighted.

Lens power is measured in diopters and written using a plus or minus sign. For instance, your prescription may read +7.00 D. This would mean that you have seven diopters of farsightedness. If your prescription reads -5.00 D, this would mean that you have five diopters of nearsightedness.

Cylinder (CYL)

A cylinder is something that is used for astigmatism correction. This condition is usually caused by an oddly shaped cornea.

Normally, a cornea (the outermost, clear part of the eye) is supposed to be completely round and equal in all directions, like a sphere. However, sometimes, corneas can be shaped less like a sphere and more like a football. Having a cylinder on your prescription means that your vision will need a cylindrical correction, not a spherical correction.

Axis (AX or X)

If you have astigmatism, you might also have an axis on your eyeglasses prescription. This number describes exactly where your astigmatism is on your cornea. This way, the glasses manufacturer knows where to put the cylinder on your lens.

The axis is measured on a scale of 1 and 180 degrees, and this number shows where the astigmatism lines up in your eye.


This is where your optometrist will note any additional lens power you might need. For instance, maybe you have age-related presbyopia, and you’d like a section of your glasses to have extra magnifying power so you can ditch your reading glasses. This section is where your eye doctor will make a note of that additional information.


If you’re just farsighted or nearsighted, you probably won’t see a prism on your prescription. However, if you have double vision, a prism correction can help with that.

Double vision is when you see two of the same object, no matter what you’re looking at. A prism can help combine these two images so that you can see clearly. The prismatic power will also be measured in diopters.

If you have double vision, your doctor will also note where the prism should be added to your lens, as well as how thick the prism should be. This will be noted using some abbreviations.

These could include:

  • BU: Base up
  • BD: Base down
  • BI: Base in
  • BO: Base out

Other Abbreviations

Although these are the most common elements you might see in a prescription, there are some other abbreviations your eye doctor might use when making notes about your vision.

Here are some of the other common abbreviations and what they mean:

  • OU: Oculus uterque. This is based on the Latin term for “both eyes.”

  • NV: Near vision. This describes your vision with up-close objects.

  • DV: Distance vision: This describes your vision as it relates to far-away objects.

  • PD: Pupillary distance. This describes the distance between your pupils. This measurement doesn’t have any effect on your vision — in fact, it’s actually used to make sure your eyeglass lenses line up properly with your eyes.

What Is Astigmatism?

Astigmatism describes an eye that is not completely spherical. Either the eye can be too tall (vertical astigmatism), or it can be too wide (horizontal astigmatism).

With astigmatism, the light that enters your eye does not properly hit your retina, which makes your vision blurry at a distance and up close. This can also cause you to see halos around lights, and you may not be able to see clearly at night due to the interference from street lights, traffic lights, and car lights.

Astigmatism is mostly hereditary, which means that if you have it, you likely inherited it from your mom or dad. However, it can also be caused by eye disease, eye injury, or eye surgery. If you’ve heard that astigmatism is caused by looking at screens or reading in the dark, don’t worry — that’s a myth. Currently, the science says otherwise.

What Does Nearsighted and Farsighted Mean?

Nearsightedness (or myopia) is a condition where you can see well up close, but you cannot see well at a distance.

On the other hand, farsightedness (or hyperopia) is a condition where you can see well at a distance, but you cannot see well up close.

Nearsightedness is caused by the light refracting incorrectly in your eye. When the curvature of your cornea or your eye is off, the light that comes into your eye won’t focus correctly. This is most common with eyes or corneas that are long or oval-shaped.

Farsightedness is also caused by light that is refracted incorrectly in your eye. However, instead of being caused by long corneas, hyperopia is caused by short corneas or eyes.

The scale will vary depending on which optician you see, but typically, a correction of -5 diopters or more is considered to be high myopia. Meanwhile, a correction of +5.25 or more is generally considered to be high hyperopia.

What Are Bifocals and Progressive Lenses?

All of the information up until now makes sense if you’re simply nearsighted or farsighted — but what if you’re both? Or, what if you’d like to consolidate your reading glasses and prescription glasses into one pair of frames?

This is where multifocal lenses come into play. Multifocal lenses are eyeglass lenses that contain more than one prescription.

Bifocals are lenses that contain two prescriptions. Typically, the top part of the lens is made to correct distance vision, while the lower part of the lens corrects up-close vision. Usually, you’ll see a very clear line on the lens where one prescription starts and the other one ends.

Trifocals are lenses that contain three prescriptions. In trifocals, usually, the top part of the lens corrects distance vision, the lower part of the lens corrects up-close vision, and the main part of the lens corrects middle-distance vision. As with bifocals, there is usually a clear and visible line between each prescription area.

The modern solution for multifocal lenses is progressive lenses. Just like with trifocals, progressive lenses provide three separate prescription areas. However, unlike multifocal lenses, progressive lenses seamlessly blend between prescription areas.

This helps get rid of the unsightly line that others can often see in multifocal glasses. Plus, it makes it easier to see, as you can easily switch between prescriptions without needing to refocus your vision. Also, since the prescriptions gradually fade into each other, there are various levels of each prescription that you can use to see what you’re looking at.

Is the Prescription the Same for Contact Lenses?

Not everyone wants to wear glasses. If you don’t want to wear glasses but still need a prescription to see, then you can try contact lenses!

Contact lenses are pieces of soft hydrogel that sit directly on your eye. You need to take contact lenses out at the end of each day, and you must care for contacts differently than you do glasses.

Because contact lenses sit much closer to your eye than regular eyeglasses, they can’t use the same prescription as your regular glasses. To get a contact lens prescription, you’ll need to add a contact lens exam and fitting onto your regular eye exam.

Aside from the prescription elements above, three notes you’ll see on your contact prescription include:

  • Base Curve (BC): This number measures the curvature of your eye and is necessary for the contact to properly mold to your eye shape. The base curve is expressed in millimeters and is always between eight and 10 mm.

  • Diameter (Dia): This number measures the width of your contact lens to make sure that it fits your eye properly and provides enough prescription coverage. This number is often expressed in millimeters and usually falls between 13 and 15 mm.

  • Lens Name: Your eye doctor will also need to note the brand name of the contacts they are prescribing to you.

How Can You Tell if Your Prescription Is Expired?

Once you have your eye prescription, you can use it forever — right? Well, not quite. Your eye health can change over time, which means that your vision prescription might also change, as well. You shouldn’t notice any drastic changes in vision, but it’s normal to experience gradual changes in eye alignment or health.

Because of this, it’s important to get a comprehensive eye exam once a year to make sure your prescription still matches your vision. Most eye prescriptions will expire after two years. This doesn’t mean that suddenly they won’t work — it just means that you’ll need to visit your eye doctor to make sure everything still looks good.

Yearly visits to the eye doctor are also an important part of eye care. While you’re there, your optometrist will also ask you questions about your vision to get a comprehensive picture of your eye health. This way, they can catch any potential concerns before they become serious.

What Are the Benefits of Wearing Prescription Glasses?

Eyewear is more than just a trendy accessory — it actually has many benefits. Here are some reasons you may want to commit to wearing your prescription glasses.

Helps You See Better

This one may be a bit obvious, but wearing your prescription glasses can help you see better. Your prescription is designed to correct any vision problems you may be experiencing — putting your glasses on should feel like waking up from a dream.

This also means that they can make driving safer, help you to see more details, and even help you succeed in work and school environments that require attention to detail.

Prevents Eye Strain and Headaches

If you need a glasses prescription but have been living without one, then you may be used to eye strain. Eye strain happens when you’re using your vision intensely for a long period of time, such as when you’re driving or staring at a screen. However, it can also happen if your eyes are having to overcompensate for poor vision.

Symptoms of eye strain include:

  • Sore or itching eyes

  • Watery or dry eyes

  • Blurry vision

  • Headache

  • Sore neck, shoulders, and back

  • Sensitivity to bright light

  • Difficulty concentrating

  • Eyes that feel heavy

Provide Sun Protection

As an added bonus, many glasses feature UV protection. Just like UV rays can damage your skin and overall health, they can also damage your eyes and eventually compromise your eyesight.

Many glasses are made with lenses that offer protection against both UVA and UVB rays, both of which can damage the eyes. Plus, you can also put your prescription in sunglasses. If you do this, you may also be able to take advantage of features like polarized lenses, mirrored lenses, and gradient lenses that can also influence the amount of light your eyes are exposed to.

Easily Accessorized

We said earlier that glasses aren’t just trendy accessories. This is true, but let’s face the facts — you’ll probably be wearing your glasses most of the day. They’ll be with you from the office to the clubs, so they definitely do fall into the category of everyday accessories.

Just like any accessory, it’s important to choose glasses that fit your personal style and make you look good. However, we know that your individual style can change from day to day.

That’s why we came up with our unique frame system to give you ultimate style-ability. With Pair Eyewear, you’ll first select a base frame that suits your face shape. We have a few different colors and patterns that our base frames come in, so make sure you choose a pair that reflects your personality.

Once you’ve chosen your base frames, it’s time to pick your top frames. These lightweight covers come in all sorts of fun designs and prints, and they easily snap onto the face of your base frames thanks to our extra-strong magnet system. With multiple collections of top frames to choose from, plus more being added every week, you’ll be able to build a new perfect pair of glasses every day.

The Bottom Line

If you’ve just received a glasses prescription, you might be curious about what it all means. Common features in an eyeglasses prescription include the sphere, cylinder, lens power, axis, and prisms. Your prescription will likely be different if you get contact lenses.

If you’re not vibing with any of the eyeglasses options at your optometrist’s office, head on over to Pair Eyewear. We can add your prescription to any one of our glasses so that you can have the best of both style and function. Browse our available glasses styles today!


Lens Power, Nominal Power, Focal Length, Sagittal Depth, Thick Lens Power | NAO

Nearsightedness - Symptoms and causes | Mayo Clinic

What Is Astigmatism? Symptoms, Causes, Diagnosis, Treatment | American Academy of Ophthalmology

Choosing Glasses for Your Face Shape |