Understanding your eye prescription

 

When you go to the eye doctor, have your eye examination, and now it is time to get your prescription, you are perplexed by all those letters and numbers. What do they mean? How do they suggest what type of glasses you should purchase?

You do not need to worry. No matter how complicated eye prescriptions may seem, we will explain all their components so you understand them. It will not only help you understand your eyewear better, but also make for an extremely useful party trick.

Here is an explanation of your glasses prescription

Whether your prescription is written on paper or digitized, it may be displayed as a grid or chart containing rows, columns, and cells incorporating letters, numbers, and words.

Taking a look at our example eye prescription chart, you will be able to put what you have learned into action.

Abbreviations for eye prescriptions

It is commonly referred to by the Latin term oculus dexter, which means “right eye” in Latin. The same root is used for the words dextrous and dexterity.

The term “OS” refers to your left eye. The Latin word means “left eye,” which is merely a reference to your direction. We promise that your left eye does not have any morally sinister characteristics compared to your right.

OR: Both of your eyes. OR is Latin for oculus uterque, which means both eyes.

NV stands for near vision (the ability to see close-up).

Distance vision (seeing things from a distance).

It is a measurement of how far your pupils are apart. Your pupillary distance helps align the lens center with the center of your pupils so that your vision is as accurate as possible. There are several methods for measuring pupillary distances, including manually or using a pupillometer.

If you are lucky, your eye doctor will always include your pupillary distance on your prescription. However, this does not always occur. If yours does not, you can always use the online tool to measure your pupillary distance.

A sphere is a correction that is generated in all meridian directions of the eye. You will see numbers listed in the SPH column, and we will discuss these in the next section. 

Scale for determining eye prescriptions

A diopter is a unit of measurement, just like a gram or an ounce. It appears in the “Sphere” or “Cyl” column of your eye prescription. However, diopters measure a lens’ refractive power, not its mass. When your prescription is high, you will see larger numbers (more optical power!) and when your vision requires less assistance from glasses or contacts, you will see smaller numbers.

If you do not require glasses at all, then your vision would not require any optical power from lenses. If you do not require glasses at all, then you would not require any optical power from lenses.

When the number is shown with a negative sign, that indicates myopia, or nearsightedness. A person with -3 diopters of nearsightedness, for example, may have difficulty reading words on a chalkboard from a considerable distance.

In the case of positive numbers, these indicate diopters that will correct farsightedness, or hyperopia. For example, someone with a positive diopter of farsightedness might have difficulty reading text very close to their face.

Term(s) that may appear on your eye prescription

Your eye prescription may include other terms, depending on the type of lenses you require:

A CYL or cylindrical lens refers to a lens power needed to correct astigmatism in a person with astigmatism. Astigmatism occurs when the cornea or lens of your eye is not spherical. Astigmatism requires cylindrical vision correction rather than spherical vision correction for patients with the condition. (If there is no number attached to this term on your prescription, then there is no astigmatism to correct!)

Axis: Again, this is for astigmatism patients. The axis is the number (between 1 and 180) on your prescription that determines the orientation of your astigmatism correction. Axis measures in degrees, not diopters. A cylinder and an axis are always inextricably linked—neither can exist without the other!

There is also a possibility of adding additional magnification. If you have age-related presbyopia, you may find it hard to read text close up, so you can reserve a section of your glasses lenses for extra magnification. This is similar to having reading glasses built into your regularly prescribed glasses.

A prism can occur when the eyes are misaligned, resulting in symptoms such as double vision. (Strabismus, also known as crossed eyes, is one disorder that leads to misalignment of the eyes.)

A prism can be added to your lenses in order to account for this condition. The prism will be placed based on the prescription of your eye doctor, noting the direction of the prism’s thickest edge, or base.

• BU: bottom-up

• BD stands for base down

• The BI stands for base in

• Outbound: base out

Additionally, a prism has a specific refractive strength, which is measured in prism diopters.

If you want to ensure that your eyes are seeing as clearly as possible, it is important to have them examined regularly. Your prescription may not remain the same forever. 

There is a general rule that eye prescriptions will be valid for a year or two before they expire (the exact time period depends on state laws). Once they expire, you must have an eye exam to renew the prescription.

How Do You Know If Your Eye Prescription Is “Bad”?

Every now and then, people ask: “How bad is my eye prescription?” But you shouldn’t be negative about your eye prescription! There is no such thing as a “bad” prescription-you are likely worried that your prescription is unusually strong.

In case you are interested in determining the cutoff between moderate and severe types of vision problems, we can advise you that nearsightedness that requires refractive corrections of -5 diopters or more can be considered high myopia, whereas hyperopia is defined as a prescription of +5.25 diopters. Institutions may differ in their usage of these scales.

There is another interesting fact about vision correction: Individuals with severe nearsightedness can have issues with their near vision in addition to their distance vision, and it is also possible for people with severe farsightedness to have issues with their distance vision.

You should take away the most important point that your eyesight is neither good nor bad-it just requires a specific level of stylish tech to perform at its best.

Is your eye prescription likely to change?

The fluctuation of your vision prescription is not normal over time and should be investigated (unless they are the anticipated result of an injury or treatment). However, small, gradual changes are definitely possible, especially as your eyes and body age.

In your forties, you might find that you begin to develop presbyopia, which will require you to purchase reading glasses or incorporate progressive lenses into your regular frames.

Annual eye examinations are a good idea even if you do not notice any differences in your vision or are not experiencing any alarming symptoms. Annual eye exams ensure that your eye health is being monitored and that your prescription is being updated as necessary.

What is the status of prescriptions for contact lenses?

Is my prescription for contact lenses the same as my prescription for glasses?

A pair of glasses is positioned at a slight distance from your eyes, while a pair of contact lenses rest directly on your corneas. The difference in distance between the two means that the prescriptions of the two might differ.

A doctor may also need to adjust your contact prescription accordingly because contact lenses are made with fixed parameters determined by their manufacturers. These adjustments will also enable the doctor to differentiate your contact prescription from your glasses prescription.

Contact lens prescriptions should include the name of the brand you have been prescribed, even if the values on both prescriptions are the same (e.g. Acuvue, Clariti, Daily, etc.).

Your optometrist also needs to include information on your contact lens prescription regarding the fit of your contacts. That’s right—your contacts must fit you properly.

Your contact lens prescription should also include the following measurements:

Usually between the numbers 8 and 10, the base curve (BC) refers to the curvature of your contact lens, which should be adjusted to fit your natural eye shape comfortably.

An eye contact lens has a diameter of 13 to 15 millimeters, which is equivalent to the diameter in regular math. Most contact lenses have a diameter between 13 and 15 millimeters.

It is not possible to purchase contact lenses without all of the above information. Submitting only your glasses prescription is not sufficient. Therefore, please inform your eye doctor when scheduling your exam if you intend to wear contacts in addition to (or as an alternative to) glasses. As a result, they will know to include a contact lens fitting to determine whether the contacts fit and are visible.

Keep in mind that you have a right to your eye prescription

As a consumer, you have the right to receive a copy of your eye prescription, which should be provided by your eye doctor following your examination.

We recommend holding onto a copy so that it’s easy to shop online for glasses and contacts. You should never be required to purchase eyewear from their office in order to get your eye prescription.

Once you’ve determined your eye prescription precisely, all that remains is for you to find frames (or contacts) that make you feel fabulous!