How To Read Prescription For Glasses: An Ultimate Guide

How To Read Prescription For Glasses: An Ultimate Guide

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When you cannot understand even a single number on your eye prescriptions, it turns out to be quite difficult while acquiring glasses on the Internet. 

Don't rush to give up! If you are searching for a solution, look no further than our website.

Once you reach our simplest explanation on how to read prescriptions for glasses, we're sure you will be able to figure out all meanings hidden behind the tricky numbers and abbreviations.

how to read prescription for glasses

OD vs. OS 

Usually, when looking at the eye prescription, you will see a series of numbers lying under the abbreviations OD vs. OS. What are OD and OS? How do they work in terms of visual health? 

Usually, notations are all Latin abbreviated forms; OD and OS are not exceptional. OS stands for the phrase "oculus sinister," which means "left eye," while the other is a short term of "oculus dexter," referring to "right eye." 

Besides, a column titled OU, which implies both eyes may also appear on occasion. You might ask why they don't normally label them as the acronyms of "right eye" and "left eye"? The fact is that they do call so. 

In eyewear and eye medication, these phrases such as "OD" or "OS" are widespread. However, some eye doctors prefer to update their prescription writing by utilizing LE (indicating "left eye") and RE (indicating "right eye") rather than OS and OD.

Another intriguing fact is that the data for your right eye (OD) will show first at all times, followed by the data for your left eye (OS). 

This happens as whenever the doctors see your face, they will catch your right eye on their left side first and your left eye on their right side after that.

Sphere (SPH)

SPH is a common abbreviation for the sphere section, which is also a measurement that demonstrates how severe the eye adjustment must be. In other words, it indicates the amount of lens power recommended to treat nearsightedness or farsightedness.

If you see a minus sign (-) beside the number under this section, it means that you're nearsighted, and your close view is better than the far view. Conversely, if a plus sign (+) appears, you are farsighted and need near sight adjustment.

Plus, because the unit of this measurement for the correction is diopters (D), there will appear a combination of a minus sign (-) or a plus sign (-), numbers, and diopters (D) written under the Sphere column.

For example, "+8.00 D" denotes that you are eight diopters farsighted. In general, the more a number deviates from 0, the more vision correction is required.  

Aside from that, occasionally, there will be other presents in this Sphere field, such as the infinity sign (which looks like a horizontal eight) and the term Plano (or Pl). They are both the alternatives of 'zero' and are used when no sight adjustment is needed.

V/A (or visual acuity) is another familiar word found on prescription, which refers to the quality of vision fixed.

Cylinder (CYL)

So what about Cylinder? The cylinder (or CYL) stands for lens power required for astigmatism in your eyes. The word "cylinder" actually refers to the lens power used to correct astigmatism is not spherical but rather curved.

A meridian has no additional curvature along with the meridian perpendicular to it can have the full value and lens curvature to cure astigmatism.

This measure occurs when a portion of the cornea has a different curvature than the rest, being more like a football than a normal circle because of astigmatism.

Plus, a negative sign (representing for treatment of nearsighted astigmatism) or a positive sign (representing for correction of farsighted astigmatism) may appear next to the number in the cylinder field.

In case your eyes don't suffer from astigmatism or your astigmatism isn't severe enough to have a correction, you won't see any figures in this column.


If you have double vision, which causes you to see two distinct images of the same object, your prescription will have a prism field. It tells you how much prismatic power your glasses need to compensate for changes in your eyes' alignment.

However, this measurement is not very common in eye prescriptions as this problem is relatively rare.

Still, if the prism does appear, in most cases, the doctors will write the infractions or metrics and measure it in prismatic diopters (as "p.d." abbreviation or triangle in handwriting).

To be more specific, when you need an eye alignment, there will be more acronyms needed for prism direction or thickest edge, including BO (base out), BU (base up), BI (base in), and BD (base down).


In short, Axis indicates the location of astigmatism on the cornea. This value also conveys an image of the lens meridian without any cylinder power to treat astigmatism.

Due to this involvement, whether there is cylinder power in a prescription for eyeglasses, an axis figure must exist, too. The Axis measured in degrees ranging from 1 to 180 will show how astigmatism aligns in your eyes. 

Granted that it drops in the number 90, your astigmatism will be in the vertical meridian of the eye. Just like that, we can infer the number 180 relates to the eyes' horizontal meridian.

After going through those figures, your eye doctors will offer you the Axis, the lens meridian perpendicular to the meridian containing cylinder power, and get the best treatment for your astigmatism.


Add stands for the extra presbyopia correction (age-related farsightedness).

Let's imagine. Some people over the age of 40 have to suffer from farsightedness while not having good nearsighted eyes. However, an extra pair of glasses for other purposes seem to be fairly disturbing. In that case, a bifocal or progressive lens won't be the best choice.

Yet, how can they know which one is most suitable for them? Depending on the situation, Add will help them get rid of their confusion by assisting in focusing their vision for either long or short distances at the same time.

In this way, you can easily combine two prescriptions into one, one for farsightedness and one for nearsightedness.

This kind of number frequently appears on reading glasses prescriptions or the underside of bifocal or progressive lenses. Even though it may not include a plus sign besides, the number in this field of the prescription is a plus power all the time,

Also, it often varies from +0.75 D to +3.00 D and is nearly identical for both eyes.

What's more, there is also another measurement called Intermediate ADD (Int Add). You may have an Int Add number if you need glasses for visual tasks such as computer work. 

How Everything Is Measured

Luckily, the units of all the measurements above are vastly simple for you to keep track of. Sphere, cylinder, and add powers are typically present in the form of diopters. They are usually shown in quarter-diopter (0.25 D) intervals and are in decimal notation.

Although the prism is quite equivalent to those three above since they all appear as decimal forms, just one number usually follows the period (for example, 0.3).

Otherwise, The axis values from 1 to 180 represent just a meridional position instead of a power.

Can You Use The Prescriptions To Buy Contact Lenses?

Contact lenses have a separate prescription compared to eyeglasses since they rest directly on your eye. Unlike an eyeglasses prescription, a contact lens prescription comprises dimensions for the size and brand of contacts you're wearing.

To make sure the customers are comfortable with the products, whenever you take the medication, the store will let you try on a sample to see whether the lenses are suitable for you.

That's why you can not utilize your glasses prescription to purchase contact lenses. 

Bottom Line

It can be easy to find overwhelming when confronted with complicated numbers and symbols. Yet, if you dig in, you would see things in different ways.

Hope you could get every backed-up information about reading prescription for glasses in mind after scrolling down our content. Now you could undoubtedly shop for your favorite glasses on sites without any hesitation!