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Can You Convert Glasses Prescription To Contacts

What Do The Numbers On My Prescription Mean

Can I convert my glasses prescription to a contact lens prescription?

Your prescription may include the following: SPH, CYL, Axis, ADD and Pupillary Distance .

The first four parameters have to do with your visual correction. PD is a crucial measurement we need to make your glasses.

Heres the meaning behind each of these letters and numbers on your glasses prescription:

1. OD oculus dexter indicates your right eyes parameters.

2. OS oculus sinister shows your left eyes parameters.

3. SPHsphere indicates the amount of lens power prescribed for nearsighted or farsighted vision. It is measured in diopter and uses for farsightedness and for nearsightedness .

4. CYL & AXIS: a Cylinder and Axis number are required to correct Astigmatism. Both parameters will be required together.

5. ADD: provides magnifying power for reading, bifocal, multifocal and progressive lenses. You will most likely have the same number for both eyes that usually ranges between +0.75 and +3.00. Occasionally, lower add powers than +0.75 can be found on a prescription. These are for Anti-Fatigue lenses such as our SightRelax lenses.

There is a separate prescription for your right eye and your left eye. Most of the time, OD and OS are indicated on the left of your prescription and the following numbers show each eyes specific needs. Some glasses prescriptions also include additional numbers such as:

6. Prism: measured in prismatic diopter . It is required when eye alignment needs assistance. It is indicated as follows:

Add The Sphere Power Line

Look at the glasses prescription that youre working with and locate the Axis number. This number represents a degree value and will be somewhere between 1 and 180. Now draw a line in the direction of the Axis .

In our example prescription, thats 45. That means that a line at 45° must be drawn on the power cross. This is the Sphere Power Line. It represents the sphere power so write it down next to that line.

Are Glasses And Contact Prescriptions The Same

By: Eyetique|Published on: Feb 11, 2020|Categories: Eye Health, Glasses, Kids Health|

Heres everything you ever wanted to know to understand your glasses and contact lens prescriptions.

If you wear both glasses and contact lenses, you might have wondered if your prescriptions are interchangeable. Could you submit an eyeglass prescription to get a prescription for contact lenses filled, for example, and vice versa?

The answer is no. While they both have the same objective to correct what eye doctors call refractive errors that prevent you from seeing correctly prescriptions for eyeglasses and contact lenses are distinctly different.

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Why Do Contact Lenses Require A Prescription

Contact lenses are comfortable and a great form of vision correction, but they do carry some risks if theyre not worn and cared for as directed. Contact lenses are classified as medical devices by the FDA, and should only be purchased when you have a prescription for them. Wearing contacts without a prescription, or wearing a different brand than prescribed , can seriously endanger your eye health and will not adequately correct your visiononly an optometrist or ophthalmologist can determine the type and degree of vision correction you need.

How To Convert A Contact Prescription To A Glasses Prescription

Can you convert a glasses prescription to a contact lens prescription ...

Contact prescriptions differ from glasses prescriptions. Because contact lens prescriptions require different information, including the size and shape of the lenses, the two prescriptions contain different details 1. It is important to understand the differences before converting contact prescriptions to glasses.

Note the prescription power of the contact lenses. The power, also called diopter, is written as plus for farsightedness, such as +2.00, and minus for nearsightedness, or -2.00. Your power can start at 0.00 and increases in .25 steps to as high as 20.00 diopters or more. If your contact prescription is plus or minus 4.00 diopters or more, optical math is used to convert the prescription.

Check with your eye doctor to compensate for vertex distance if the prescription is stronger than plus or minus 4.00 diopter. The power changes depending on how far a corrective lens is from the eye. Contact lenses sit right on the cornea. Glasses lenses rest an average of 10 millimeters away. The lens power is different as you move a lens further from the eye and the numbers will be different in a contact and glasses prescription beginning around 4.00 1.

Measure the PD . Hold a ruler in front of the person to be measured and have them look straight ahead. Line up the 0 on the ruler in front of his right eye.


Check with your eye care professional if you need additional help interpreting your contact lens or glasses prescription.

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Why Does Distance Between Lens And Eye Matter

It matters because of this:

In a nutshell, this simple equation states that the perceived power of lenses changes as you change the distance between the lens and the eye.

The perceived power of lenses changes as you change the distance between the lens and the eye.

Now, as we know, the lenses in glasses are at a different distance from the eyes than contact lenses are. The distance between a corrective lens and they eye is called the vertex distance.

  • For glasses, the vertex distance is usually somewhere between 12-15mm
  • For contact lenses, the vertex distance is always zero

This equation tells us that, for example, a -6.00D lens held 13mm from the eye will not feel like a -6.00D lens if placed directly on the eye. Thats why we need this equation in order to convert a glasses prescription to contact lenses.

How To Read A Multifocal Contact Lens Prescription For Presbyopia

If you have presbyopia and are a good candidate for multifocal contact lenses, youll see one or both of the following terms on your prescription. Sometimes these are referred to as progressive contacts.

ADD: ADD stands for addition or additional magnification. It might also be listed as Add Power or Extra Strength. This is another measure of vision correction for near vision that will help with close-up tasks. It will either be a number in diopters, or be a written level: low, medium, or high.

D/N: D/N stands for dominant or nondominant eyemultifocal and bifocal contacts have different levels of vision correction for each. Your dominant eye is associated with distance vision, and your nondominant eye is associated with near vision. Only some brands of multifocal contacts use D/N, so you might not see this term on your prescription.

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Soft Lens Vs Gp Contact Lens Prescriptions

A spherical soft lens does not correct for astigmatism. For someone wearing soft lenses, a toric soft lens would be needed if there is, at minimum, 0.75D of astigmatic correction. Therefore, in our example, the right eye would require either a GP lens or a soft toric lens.

Because the spherical correction for the right eye is 4D or greater, and because toric soft lenses are typically available in 0.25 diopter increments, the contact lens prescription may be closer to -4.25 – 1.25 x 180. The exact prescription can be determined only with diagnostic lens fitting by an eye care professional.

For the left eye, it’s possible that a spherical soft lens with a correction identical to the glasses prescription will work, but again, this determination is best made after a diagnostic fitting.

How To Read A Contact Lens Prescription

How to convert eye glasses prescription into contact lens prescription?

Understanding your contact lens prescription can be tough if you arent familiar with the different numbers and abbreviations that eye doctors use. Looking at it, you might be wondering: Which numbers correspond to which eye? Wheres the strength of my contact prescription? And what is BC?

There may even be more information on your contact prescription than your glasses prescriptionand yes, the two prescriptions are different.

Thankfully, learning how to read your contact prescription is easy. Well go over all the terms youre likely to see for the different types of contact lenses, whether your prescription is on paper or on a box.

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What Do The Abbreviations And Symbols On Both Prescriptions Mean

Some of the abbreviations and symbols youll see on your eyeglasses prescription:

  • OD refers to the right eye. OS refers to the left eye. You may also see the abbreviation OU, which refers to both eyes. All are Latin abbreviations.
  • SPH stands for sphere, or the amount of lens measured in diopters .
  • CYL stands for cylinder, indicating the amount of power you need to correct astigmatism.
  • Axis is what tells you the orientation of the astigmatism.
  • ADD stands for addition, and is used in bifocals to add correction for farsightedness.
  • PD indicates the pupillary distance, or the distance between the centers of your pupils.
  • A minus sign indicates you are nearsighted.
  • A plus sign indicates you are farsighted.
  • The further from zero the number is on your prescription, the stronger your prescription is.

In addition to many of the above, your contacts prescription will include the power, base curve and diameter, as well as the contact lens material and brand or type of contacts.

  • Power is the same as sphere .
  • BC is the abbreviation for base curve, the measurement of the curvature of the back surface of the contact lens. Its determined by the shape of your cornea.
  • DIA stands for diameter, and indicates the size of your lends. It works with the base curve to determine how your lens will fit.
  • The contact lens material and/or brand is indicated because different lens materials have different degrees of oxygen permeability. Your eye care professional will know which one is best for you.

How To Adjust Binoculars With Glasses

Since eyeglasses hold binoculars away from the eyes and let in peripheral light anyway, retract the eyecups if you do wear glasses. Next, set the barrels of the binoculars to match the distance between your eyes. Looking through them, adjust the barrels until you have a solid image through both eyes.

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How To Convert Your Glasses Prescription To Contacts

In this article, you will learn how to convert your glasses prescription to contact lenses. There are a few exceptions you need to keep in mind when doing the conversation. The easiest way to convert your glasses prescription into your contact lens prescription is to use a conversion sheet I listed at the end of this article.

In this sheet, you will find three columns. The middle shows the spectacle power. This spectacle power is the same as the lens power on your prescription under the acronym SPH for the right and the left eye. When the lens power is negative you need to check what the needed prescription will be on the left of the conversion sheet.

In this case, you would be shortsighted. When you are farsighted and the lens power in your prescription is positive you need to look in the right part of the sheet to what your prescription needs to be converted.

What you need to know is such a conversion sheet uses standard parameters. The supposed distance in such a case is 12mm between your cornea and the back surface of the lens in your glasses.

While this is obviously an average your actual distance from the standard could differ a lot. And with this, the conversion needs to be calculated with a formula you find below.

How To Use A Vertex Distance Conversion Chart

3 Ways to Convert Your Glasses Prescription to Contact Lenses ...

Using a vertex distance conversion chart is simple.

  • The Glasses Lens Power column refers to the power on the glasses prescription.
  • If the power on the glasses prescription is negative, then the converted power is directly to the left.
  • If the power on the glasses prescription is positive, then the converted power is directly to the right.

Lets do a quick example to demonstrate this.

Say you have this glasses prescription and want to convert it to contact lenses:

You could use the formula:

Perceived lens power = -6.25 / = -5.75

Or, we can simply refer to the vertex distance conversion chart:

Find the number on the glasses prescription in the middle column. If that number is negative, the converted number is the one on the left as is the case in this example. If number on the glasses prescription was positive, the converted number would be on the right.

This is showing that a -6.25D lens placed at 14mm from the eye would only seem like a -5.75D if it was place directly on the eyes surface. Recall that a prescription for glasses is measured with lenses at 14mm from the eye, not at the eyes surface. So if -6.25D was given in contact lenses, it would actually feel like -6.75D at 14mm which would be too strong!

This may feel a little confusing but the minutia of the exact reason and mechanism by which this happens is not overly important to practitioners like yourselves.

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Glasses Prescription Vs Contact Lens Prescription

Glasses prescriptionContact lens prescription

Note: The glasses prescription and the contact lens prescription above are just samples. Yours may differ but should contain the same information.

Note: not everything shown on the above table will necessarily be included on your prescription. The above is just an example of what could be found on your prescription and what will not be found on your prescription depending on whether you wear contact lenses or glasses.

What Happens If Contacts Are Too Strong

It doesnt happen often, but if an error was made in your contact lens prescription and you are wearing lenses that are too strong, too weak or otherwise incorrect, this could cause eye strain and headaches. If this is the cause, replacing the lenses with contacts of the correct power should eliminate your headaches.

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Prescription Eyeglasses And Contact Lens Prescriptions: Faq

Lets start with some of our most frequently asked questions about glasses and contact lens prescriptions. Follow our guide to find the answers on how to read glasses prescriptions:

The following tips will help you decipher and understand your eyewear prescriptions. If you get stuck, get in touch with our Customer Service team. Well be happy to contact your Eye Care Provider to verify your prescription for you.

Can You Convert A Glasses Prescription To A Contact Lens Prescription

How to convert toric spectacle prescription into contact lens prescription?

A common query for contact lens wearers is whether you can convert your glasses prescription into a contact lens prescription. Weve got the answer for you.

Both contact lenses and glasses correct common refractive errors such as myopia , hyperopia , astigmatism which requires toric contact lenses and presbyopia which requires multifocal contact lenses. Although your contact lens and glasses prescription may look similar, it does not mean they will give you the same visual acuity if you try to convert one to the other.

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Can You Get A Contact Prescription Online

You will need a current, valid prescription before you order more contacts. Fortunately, if your eyes and contacts feel fine you can now renew your contact lens prescription online using 1-800 Contacts Online Prescriptions. All you need is 8-10 minutes and you can easily get your prescription from home.

Is Glasses Prescription The Same As Contacts

Eyeglasses and contact lenses are valuable vision aids that allow people with refractive errors such as nearsightedness, farsightedness, astigmatism, etc. to see clearly and comfortably. You must have seen people using both eyeglasses and contact lenses in your family and friends at different points of time.This generally leads to a notion that since both eyeglasses and contact lenses are being used to correct the vision errors, they will even have a similar prescription. However, this is not true.

Why is glasses prescription different than lenses?Eyeglasses and contact lenses are made up of different types of materials. Contact lenses, in general, are made of hydrogel or silicone hydrogel. This material helps your contacts to stay moist and allows more oxygen to be transmitted through the contacts into the eye. Newer eyeglasses are in fact made up of advanced kinds of plastic in place of actual glasses. These glasses are lightweight, thinner, and better scratch-resistant than glass or older plastic types. Both contacts and eyeglasses also differ in their positioning with respect to the eyes. Eyeglasses are positioned around 12 mm from the eyes however, contacts sit directly on the eyes. Hence, different types of eye tests and measurements are required for each of them. This leads to differences among the elements of the prescription of the eyeglasses and contacts.

Prescription for eyeglasses and contacts: How are they different?

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Glasses Prescriptions Vs Contact Lens Prescriptions

Glasses sit some distance from the eyes, while contacts rest on the eye, meaning the prescription will not be the same. The tests and measurements are different, so substituting one prescription for the other will not give you similar visual acuity.

The information that goes into prescriptions will include the refractive error, the lens strength, and the type of lens needed. Glass prescriptions indicate a value for cylinder and axis, which does not exist for contacts.

What Are The Side Effects Of Using My Glasses Prescription For Contact Lenses

How To Convert Eyeglass Prescription To Contact Lens

Ordering the wrong type of contact lenses or the wrong prescription can lead to symptoms such as blurry vision , headache, eye fatigue, and eye pain.1 In the worst-case scenario, contact lenses purchased without a proper prescription and eye examination may lead to eye health complications and potentially lasting damage.2

Need more information about different types of contact lenses? Have a look through our Contact lenses page, or read our article explaining what glasses prescriptions mean. You can also book in online for an eye test at Specsavers.


  • American Academy of Ophthalmology. . Can outdated contact lenses harm your eyes? . Available at: .
  • engör T, Alkibay S, Ermeç Sertolu A, Aydn Kurna S. Survey to Determine Perceptions and Practices in Contact Lens Use and Identify Key Features of Safe Use Education. Turk J Ophthalmol. 2018 48:288294. . Available at: .
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