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What Is Sphere And Cylinder In Glasses

An Example Of An Eye Prescription

Sphere, Astigmatism, Axis and The Eyeglasses Prescription

Confused? Let’s use an example to clear things up.

Here is a sample spectacle prescription:

RE -2.00 SPH +2.00 add 0.5 p.d. BD

LE -1.00 -0.50 x 180 +2.00 add 0.5 p.d. BU

In this case, the optician has prescribed -2.00 D sphere for the correction of myopia in the right eye . There is no astigmatism correction for this eye, so no cylinder power or axis is noted. This optician has elected to add “SPH,” to confirm the right eye is being prescribed only spherical power.

The left eye is being prescribed -1.00 D sphere for myopia plus -0.50 D cylinder for the correction of astigmatism. The cyl power has its axis at the 180 meridian, meaning the horizontal meridian of the eye has no added power for astigmatism and the vertical meridian gets the added -0.50 D.

Both eyes are being prescribed an “add power” of +2.00 D for the correction of presbyopia, and this spectacle prescription includes a prismatic correction of 0.5 prism dioptre in each eye. In the right eye, the prism is base down in the left eye, it’s base up .

What Are Add And Prism

That leaves just two other measurements on your prescription. Add, which refers to the magnifying power added to the bottom of multifocal lenses for presbyopia correction. This will always be written as a + power, even if the doctor has not filled it out with a plus sign. It normally ranges from between +0.75 and +3.00 D and is the same level for both your eyes.

Prism refers to the prismatic power, which has a value in prism diopters, which is either written as p.d. or when it is written freehand, a superscript triangle. This part of the prescription relates to compensation made for eye alignment issues. Relatively few glasses prescriptions have a prism reading.

When it is featured on a prescription, the prism is normally identified in either fractional or metric units, ½ or 0.5, as an example. The prism direction is identified by the position of its thickest edge, or base. There are four different abbreviations used in describing prism direction. BO is short for base out and means towards your ear, BI is short for base in and means towards your nose, BD is short for base down, while BU is short for base up.

As you can no doubt see, therefore, the sphere, cylinder and, where appropriate, axis values on your prescription are three of the most important numbers. When you understand those and understand what part describes the lens power needed for each eye, you have a better understanding of what your glasses do to correct your vision issues.

What Do Od & Os Mean

Youll typically find the abbreviates OD and OS on the left side of your prescription. These are abbreviations for the Latin terms oculus dexter and oculus sinister.

Essentially, OD means right eye, and OS means left eye. You may also have a column labeled OU, which means oculus uterque, or both eyes.

Some eye doctors have modernized this and replaced OD with RE and OS with LE.

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What Is Normal Eye Sph

Sphere means the spherical correction where the meridians of the human eye are equal. It does not matter whether the correction is of farsightedness or nearsightedness it is always in spherical form. The lens power amount is, therefore, measured in D for farsightedness or nearsightedness. When the person has no astigmatism, the perfect eye shows 0 diopters. Those individuals having 1.5 or more diopters will definitely need to use eyeglasses in order to correct the vision.

Eye Prescription Chart Example

Prescription Sunglasses myopia presbyopia men glasses with diopter ...

Here are two examples of eye prescriptions, one for someone without astigmatism, and one for someone with it. Can you spot the differences and decode the terms youve learned? If so, youve learned how to read a glasses prescription like a pro.

A prescription written for someone with nearsightedness.

A prescription written for someone with nearsightedness and astigmatism.

Also Check: What Do Prisms Do In Glasses

Can Eyeglass Prescriptions Be Used To Buy Contact Lenses

No, you cannot use your glasses prescription to buy contact lenses.

An eyeglass prescription only works for the purchase of eyeglasses. It does not contain certain information that is crucial to a contact lens prescription.

That information can only be obtained through a contact lens fitting, an additional procedure that can be performed during your eye doctor visit.

Eyeglass lenses are positioned at a distance from the eyes, while contacts rest directly on the eyes. That distance affects the lens power required for eyes to focus properly.

In addition to the information in an eyeglass prescription, a contact lens prescription must specify the base curve of the back surface of the contact lens, the lens diameter, and the specific manufacturer and brand name of the lens.

Also, the power of an eyeglass prescription frequently is modified when determining the best contact lens power. This is because eyeglass lenses are worn some distance from the surface of the eye, whereas contact lenses rest directly on the cornea of the eye.

An accurate contact lens prescription can be written only after a contact lens fitting has been performed and the prescribing doctor has evaluated your eyes’ response to the lenses and to contact lens wear in general.

SEE ALSO: Contact lens vs. eyeglasses prescriptions

How To Read Your Eyeglasses Prescription

By Gary Heiting, OD

You’ve just had an eye exam and your optician has given you a spectacles prescription.

He or she probably mentioned that you are short sighted, long sighted, or perhaps that you have astigmatism. (If that’s not the case, and you still need an eye exam, please find an optician or optical shop near you.

But what do all those numbers on your spectacle prescription mean? And what about all those abbreviated terms, such as OD, OS, SPH and CYL?

This article will help you decipher all parts of your prescription and discuss it knowledgeably with an optician when you’re buying eyeglasses.

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A Glasses Prescription Is Not A Contact Lens Prescription

Spectacle and contact lens prescriptions aren’t the same. A spectacle prescription is for the purchase of spectacles only. It does not contain certain information that is crucial to a contact lens prescription and that can be obtained only during a contact lens consultation and fitting.

Eyeglass lenses are positioned at a distance from the eyes, while contacts rest directly on the eyes. That distance affects the lens power required for eyes to focus properly.

In addition to the information in a spectacle prescription, a contact lens prescription must specify the base curve of the back surface of the contact lens, the lens diameter, and the specific manufacturer and brand name of the lens.

Also, the power of a spectacle prescription frequently is modified when determining the best contact lens power. One reason is that spectacle lenses are worn some distance from the surface of the eye, whereas contact lenses rest directly on the eye’s cornea.

An accurate contact lens prescription can be written only after a contact lens fitting has been performed and the prescribing optician has evaluated your eyes’ response to the lenses and to contact lens wear in general.

Your Eye Prescription Is Yours To Keep

What The Numbers On Your Glasses Prescription Mean (Close Up Look At Sphere Power)

The Optical Consumer Complaints Service clarifies that “an optician is obliged to provide you with the written prescription following the eye examination. You are then able to take the prescription to another practice.

“By law, the prescription must provide the basic results of the eye examination.

“There are however other measurements or results which are needed to dispense glasses but these will need to be taken by the ‘dispensing practice’ . This can sometimes cause difficulties when purchasing online but the law does not require the examining optometrist to include these details as they may vary depending on the type of frames and lenses selected.”

The rule is intended to protect the “portability” of your spectacle prescription, allowing you to use it to buy glasses from the optician of your choice.

Page published on Monday, December 30, 2019

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What Is Axis In Glasses

In the third part, we will show you what the Axis in glasses is. The Axis means the angle between the two meridians of an astigmatic eye. The Axis in your prescription is usually measured from 1 to 180. The number 90 means the vertical meridian of the eye and the number 180 means the horizontal meridian.

Whats more, if an eyeglass prescription includes cylinder power, it also must include an Axis value, which follows the CYL power. In the following picture, you can see an eye prescription.

How Theyre Measured

Sphere power, cylinder power and add power always appear in diopters. They are in decimal form and generally are written in quarter-diopter increments.

Axis values are whole numbers from 1 to 180 and signify only a meridional location, not a power.

When prism diopters are indicated in decimal form, typically only one digit appears after the period .

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What Does Add Mean

Add indicates the magnifying power applied to the bottom part of bifocal, multifocal, or progressive lenses used to correct presbyopia .

This number is always positive, even if it doesnt have a plus sign in front of it. These numbers typically are the same for both eyes and range from +0.75 to +3.00.

What Does Sph Mean

What does my glasses prescription mean anyway?

Sphere, sometimes abbreviated as SPH, indicates the amount of lens power needed to correct nearsightedness or farsightedness.

The term sphere refers to the fact that distance vision correction is spherical, or equal in all meridians of the eye.

It is measured in diopters, the unit of measurement for the lens’s refractive power.

If the number is negative , it means it is correcting nearsightedness. If the number is positive , it is correcting farsightedness.

A number between +/-.025 to +/-2.00 is considered mild, a number between +/-2.25 to +/- 5.00 is considered moderate, and a number greater than +/- 5.00 is considered severe.

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How To Read A Glasses Prescription The Numbers Demystified

After an eye exam, the optometrist writes a prescription containing the information needed to correct your vision. By reading this article, you will notice that it contains many numbers and abbreviations. Are you curious to know what they mean? Here is some information to help you better understand your prescription.

First and foremost, your prescription is divided in two parts: one for each eye. On the first line you will find the letters O.D., this is an abbreviation from the Latin words Oculus Dexter, which means, right eye. On the second line, we will find the letters O.S., which stems from the Latin words Oculus Sinister, referring to the left eye.

Now, let’s take a look at what is in each section of your prescription.

Abbreviations For Contact Lens Prescriptions

Contact lens prescriptions provide the same information as eyeglass prescriptions, with the addition of some extra numbers.

The size of the lens, for example, is included for contact lenses. Because contact lenses sit directly on your eye rather than a few centimeters away, the power of a contact lens will also likely be different than an eyeglass prescription for the same person.

Additional information provided on a contact lens prescription includes:

  • BC, which is the base curvature of the lens.
  • DIA, which is the diameter of the lens.
  • An expiration date.
  • Different parameters for each eye.
  • The brand of contact lens.

The base curve value of a contact lens typically ranges from 8.0 to 10.0. Base curves vary by brand, so your prescription may change depending on what brand of lenses you are using.

Diameter values range between 13 and 15. It is possible to use a different brand of contact lens in each eye based on the unique needs of each eye.

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Getting The Right Glasses Prescription

In order to get an accurate eyeglass prescription, you will need to see an eye care professional who can perform a complete eye exam.

According to AAO, all adults should receive a comprehensive eye exam by the age of 40. At 40, many early warning signs of disease and eye problems start to appear.

You do not need to wait until you are 40 to get your first eye exam. People with a history of diabetes, high blood pressure, and a family history of eye disease are encouraged to see an ophthalmologist for vision screenings sooner. For people already using corrective eyewear, it is wise to get an updated prescription each year.

Once your eye exam is complete, your eye doctor should be able to give you an accurate eyeglass or contact lens prescription right away.

References

What Is Cyl Axis And Sph In Eye Prescription

Cylinder in Prescription Glasses. Astigmatism Correction.

When we look at the eye prescription written by our consultant, different questions come to mind.

What is CYL, AXIS and SPH? This is an important question because this is related to the eyes and gives answers related to different changes in the human eye. The CYL stands for Cylinder. The AXIS stands for Axis and SPH stands for Sphere.

All these are used for the distance correction measurement. There are two vision conditions, nearsightedness, and farsightedness.

In nearsightedness, the person can see those objects clearly which are near to him but the far objects are blurry. On the other hand, in the farsightedness, the person can see those objects clearly which are far but near object seems blurry. The sphere is the indication of how strong the lenses need to be in order to correct the vision. The cylinder is the indication of the condition, astigmatism, in which the cornea is shaped irregularly causing distorted or blurred vision. The axis is the astigmatism orientation. The 20/20 vision is the correct vision for normal eyes. This means that a person can see the object clearly at 20 feet.

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Remember: You Have A Right To Your Eye Prescription

According to the Federal Trade Commission, you are legally entitled to a copy of your eye prescription. Your eye doctor should provide you with one after your exam, or whenever you request it.

You dont have to purchase eyewear from their office to get your eye prescription, and you should never have to pay a fee solely to access it. We recommend holding on to a copy so that its extra-easy to shop for glasses and contacts online.

Now that you understand your eye prescription perfectly, all thats left is to find frames that make you feel fab!

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How Do Sphere And Cylinder Measurements Combine In Eyeglass Prescriptions

For eyeglasses, if a cylinder prescription were combined into a single spherical prescription, how would it be weighted?

As an example, suppose the prescription is S=-3.0, C=+.5×90°.

If only spherical lenses were available, would it be:

  • -3.0 ignore the cylinder value
  • -2.5 add the cylinder value
  • -2.75 add half the cylinder value

or something else.

I assume the “90°” is irrelevant, and strongly suspect the “add half” case is correct or close, but would like to know for sure.

Wikipedia’s eyeglass prescription, cylinder component section, says:

“There are two different conventions for indicating the amount of cylinder: “plus cylinder notation” and “minus cylinder notation”. In the former, the cylinder power is a number of diopters more convergent than the sphere power. That means the spherical power describes the most divergent meridian and the cylindrical component describes the most convergent. In the minus cylinder notation, the cylinder power is a number of diopters more divergent than the sphere component.

  • Add the sphere and cylinder numbers together to produce the converted sphere
  • Invert the sign of cylinder value
  • Add 90° to axis value, and if the new axis value exceeds 180°, subtract 180° from the result

For example, a lens with a vertical power of -3.75 and a horizontal power of -2.25 could be specified as either -2.25 -1.50 x 180 or -3.75 +1.50 x 090.”.

You have “S=-3.0, C=+.5×90°”, so:

  • -3.0 + .5 = -2.5
  • Answer: -2.5 + = -2.75

    Additional information:

    Order Spherical Contact Lenses For You

    Prescription Sunglasses myopia presbyopia men glasses with diopter ...

    Whether its for color contact lenses or clear ones, contact lenses for astigmatism are more expensive and can create fluctuations in vision if the contact lenses are not stable on your eyes.

    If you have a small amount of astigmatism, your eye doctor may take the spherical equivalent of prescription to order you regular contact lenses.

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    What Is A Diopter Count

    Diopter is the measurement used for the strength of eyeglass lenses. The number under the OD and OS measurement in your prescription is measured in diopters.

    Now that you understand those mysterious letters and numbers, you know how to read a glasses prescription! Knowing what they mean will also help you more easily discuss your prescription with your eye care professional.

    To Help You Adjust To Your New Glasses Prescription

    If your eye doctor detects a large change in your cylinder, it is not uncommon for them to reduce the cylinder using the principles of the spherical equivalent in order to help you adjust to your new glasses. New glasses containing a large change in cylinder can cause symptoms of eyestrain, dizziness and headaches.

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