How To Read Your Eye Prescription and Adjust to New Glasses

Prescription glasses can make a night and day difference for those who need them, allowing wearers to take in the world with a crisp, clear view.

Many people buy prescription glasses online for the convenience, affordability, and endless style options. If you’re new to shopping for glasses online, however, the process can feel a bit daunting and confusing.

Not to mention, when you receive your new prescription glasses, they can take a little getting used to. This is particularly true for those wearing progressive lenses.

Fortunately, we’ve put together a comprehensive guide to help make your experience of buying and adjusting to prescription glasses as smooth as possible. Here’s what you need to know.

Understanding Your Prescription

After completing an eye exam with an optometrist or ophthalmologist, they may determine that you require prescription glasses or that you need to update to a new prescription.

In those cases, you’ll be provided with a prescription, and when ordering prescription glasses online, you’ll be asked to provide your prescription details. While you don’t need to fully understand what every letter or number on your prescription means to order a pair of glasses, it can help to have a general idea.

How to Read Your Eye Prescription

On your prescription, you’ll notice several abbreviations, words, and positive/negative numbers, such as on the sample glasses prescription chart below. Let’s review what these mean.

Pupillary Distance (PD)

This is the distance between your pupils, and it determines where the optical centers on each lens should be placed. PD can be written in two ways: e.g. 62 (Binocular PD - distance between both pupils) or 32/30 (Monocular PD - distance of each individual pupil to the center of your nose).

With Monocular PD, the first number is for the right eye and the second for the left. Monocular PD is often required when buying progressive glasses online, but is usually unnecessary otherwise. If you only have a Monocular PD, you can add the two numbers together to get your Binocular PD.

If your prescription doesn’t include a PD number, you can learn how to measure Pupillary Distance yourself here.

OD Versus OS Eyes

OD and OS refer to your right and left eye, respectively. OD is short for the Latin term oculus dexter, which means “right eye,” while OS is short for the Latin term oculus sinister, which means “left eye.”

Sphere

Sphere indicates the power of the lens prescribed to correct nearsightedness or farsightedness. The numbers listed in the “Sphere” column stand for diopters—a unit of measurement that measures the refractive power of a lens. The higher the number, the more optical power you require.

• If the number has a minus sign in front of it (-), you are nearsighted (difficulty seeing far away objects).
• If the number has a plus sign in front of it (+), you are farsighted (difficulty seeing close objects)

Cylinder (CYL)

Cylinder indicates the lens power for astigmatism, which is an imperfection in the eye’s curvature.

You can have astigmatism in both eyes, one eye, or neither. If you don’t have astigmatism, you won’t be provided with cylinder numbers. If you only have astigmatism in one eye, you’ll only be provided with one cylinder number.

• If the number has a minus sign (-) in front of it, then your prescription was probably written by an optometrist.
• If the number has a plus sign (+) in front of it, then your prescription was probably written by an ophthalmologist.

Axis

If you have a cylinder number, you’ll also have an axis number. This tells the glasses manufacturers where to place your astigmatism correction in your lens. As with cylinder, you may have an axis number for both eyes, one eye, or neither. If you don’t have astigmatism, you will not be provided with axis numbers.

Add

Add refers to additional magnification. This is used for those seeking progressive/bifocal lenses, which have additional reading lens power on the lower segment of the lenses. Think of it as having both reading and distance glasses built into one pair of glasses. Add will always have a (+) in front of the number.

You can learn more about how to determine what strength reading power you need here.

Prism

Prism correction is used in prescription glasses for some people with double vision (diplopia). This is when someone sees two images of a single object. The prism helps align the two images, eliminating double vision.

Expiration Date

Because eye prescriptions tend to change over time, your prescription will have an expiration date. Prescriptions are typically valid for a year or two. After that, you’ll need to visit an optometrist or ophthalmologist to get an up-to-date prescription.

Adjusting to New Glasses

Receiving your new prescription glasses in the mail is exciting, but it’s important to be aware that there’s a bit of an adjustment period when wearing your new specs. Let’s review some common questions about this.

How Long Does it Take to Adjust to New Glasses?

When you start wearing a pair of prescription glasses for the first time, or you start wearing glasses with an updated prescription, it can take your eyes and brain time to adjust to the clearer image you’re seeing.

For most people, this adjustment period only lasts a few days, but it can take up to two weeks for some, particularly if it is your first time wearing progressives.

Is it Normal to Struggle with New Glasses?

While the adjustment period is normal and natural, it can cause some symptoms, including:

• Dizziness
• Blurry vision
• Eye strain
• Distortion
• Lack of depth perception
• Fishbowl effect (feeling like what you’re seeing is bent)

These symptoms are typically mild and only last a few days. If the symptoms are severe or persist for more than a few days, contact your optometrist or ophthalmologist, as your prescription may need to be adjusted.

Pro tip: Try your new glasses first thing in the morning. Your eyes are well rested and less strained, so adjusting may be easier.

Should I Wear My Prescribed Glasses All the Time?

Whether or not you should wear your glasses all the time depends on your unique vision needs and lifestyle. Your eyecare professional should let you know how to use your glasses when you are given your prescription. If not, call and ask.

Some people may only need to wear prescription glasses when doing certain activities like reading, working on a computer, or driving.

Others may require prescription glasses for most of the day (minus showering and sleeping) to maintain a safe level of vision.

In other cases, people might swap their prescription glasses for contact lenses in certain circumstances, such as when playing sports or exercising.

Pro tip: After you receive your new prescription glasses, try not to go back to your previous pair. It takes time for your brain and eyes to become comfortable with a new power, and going back and forth will delay this process.

Understanding Progressive Lenses

We briefly mentioned progressive lenses above, but let’s dive deeper into what they are, why someone might need them, and what the adjustment period is like.

What Are Progressive Lenses?

When buying prescription glasses online, you’ll often be presented with two options: single vision and progressive lenses.

Single vision lenses correct one field of vision, either near or distance, while progressive lenses correct multiple fields of vision in one lens. Instead of having different pairs of glasses for different needs (i.e. distance, computer and reading), progressive lenses include multiple powers in one pair of glasses. This eliminates the need to swap glasses for different activities.

How exactly do they work?

Progressive lenses have zones designed for close-up, intermediate, and distance vision. The top portion of the lens typically helps with distance viewing, the middle portion is designated for intermediate viewing, and the bottom portion is reserved for close-up vision.

Pro tip: When you put your progressives on for the first time, try to read something up close. Pointing your nose at what you want to read, move your chin up and down until the image is clear. This is the reading area of your glasses.

Now look at something arms length away or just beyond. Again move your chin up and down until whatever you're looking at becomes clear. This is your intermediate range.

Finally, point your nose and look at something about twenty feet away and - you guessed it - move your chin up and down until it becomes clear. This is your distance vision.

Eventually your brain and eyes will communicate automatically and know which zone you need to look through to see clearly.

In most cases, progressive glasses are meant to be worn all day.

How Long Does It Take to Adjust to Progressive Lenses?