how to tell what my vision is from prescription
How to Read Your Eyeglasses Prescription
Making sense of your eye prescription chart
The numbers on your eyeglass prescription relate to the shape of your eyes and strength of your vision. They can assist yous figure out whether you accept nearsightedness, farsightedness or astigmatism — and to what degree.
If you know what to look for, you tin make sense of the numbers and abbreviations on your prescription chart.
OD vs. Bone: Ane for each eye
Eye doctors use the abbreviations "OD" and "OS" to denote your right and left eyes.
Your centre doctor may requite you a paper prescription that looks something like this. 
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OD is your right middle. OD is brusque for oculus dexter, the Latin phrase for "right eye."
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OS is your left centre. OS is curt for oculus sinister, Latin for "left eye."
Your vision prescription may also have a cavalcade labeled "OU." This is the abbreviation for oculus uterque, which means "both eyes" in Latin.
These abbreviated terms are mutual on prescriptions for glasses, contact lenses and eye medicines, but some doctors and clinics accept opted to modernize their middle prescriptions by using RE (right eye) and LE (left eye) instead of OD and OS.
The data for your correct eye (OD) e'er comes before the data for your left middle (Os). Center doctors write prescriptions this way considering, when they face yous, they encounter your correct eye on their left (offset) and your left eye on their correct (second).
Sphere (SPH)
Sphere indicates the amount of lens ability prescribed to correct nearsightedness or farsightedness. Lens power is measured in diopters (D).
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If the number under this heading comes with a minus sign (–), you are nearsighted.
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If the number under this heading has a plus sign (+), y'all are farsighted.
The term "sphere" means that the correction for nearsightedness or farsightedness is "spherical," or equal in all meridians of the centre.
Cylinder (CYL)
Cylinder indicates the amount of lens power needed for astigmatism. It e'er follows the sphere power on an eyeglass prescription.
The number in the cylinder column may take a minus sign (for correction of nearsighted astigmatism) or a plus sign (for farsighted astigmatism).
If cypher appears in this cavalcade, you lot either don't take astigmatism, or your caste of astigmatism is then pocket-size that it doesn't need to be corrected.
The term "cylinder" ways that this lens power added to correct astigmatism is not spherical, but instead is shaped so i superlative has no added curvature, and the meridian perpendicular to this "no added power" meridian contains the maximum ability and lens curvature to right astigmatism.
Meridians of the middle are determined by superimposing a protractor scale on the center'due south front surface. The ninety-caste meridian is the vertical superlative of the center, and the 180-degree meridian is the horizontal meridian.
Meridians of the eye are adamant by superimposing a protractor scale on the eye's front surface. The 90-degree height is the vertical meridian of the eye, and the 180-degree superlative is the horizontal tiptop.
Axis
Axis describes the lens superlative that contains no cylinder ability to correct astigmatism.
If an eyeglass prescription includes cylinder power, information technology also needs to include an centrality value, which follows the cylinder power.
The axis is defined with a number from 1 to 180.
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The number 90 corresponds to the vertical meridian of the eye.
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The number 180 corresponds to the horizontal meridian of the eye.
The axis is the lens meridian that is 90 degrees away from the meridian that contains the cylinder power for astigmatism correction.
Add
"Add together" is the added magnifying power practical to the lesser function of multifocal lenses to correct presbyopia — the natural farsightedness that happens with age.
The number actualization in this section of the prescription is e'er a "plus" power, even when yous don't run across a plus sign. Mostly, it will range from +0.75 to +3.00 D and will be the same ability for both optics.
Prism
This is the amount of prismatic ability, measured in prism diopters ("p.d." or a triangle when written freehand), prescribed to compensate for eye alignment problems.
Only a pocket-size percentage of eyeglass prescriptions include a prism measurement.
When present, the corporeality of prism is indicated in either metric or partial English language units (0.5 or ½, for instance), and the direction of the prism is indicated by noting the relative position of its "base" (thickest edge).
Iv abbreviations are used for prism direction: BU = base up; BD = base down; BI = base in (toward the wearer's nose); BO = base out (toward the wearer's ear).
How they're measured
Sphere power, cylinder power and add power always announced in diopters. They are in decimal form and generally are written in quarter-diopter (0.25 D) increments.
Axis values are whole numbers from i to 180 and signify only a meridional location, non a ability.
When prism diopters are indicated in decimal grade, typically merely one digit appears later the catamenia (eastward.chiliad., 0.5).
An example eye prescription chart
Still confused? Let's look at an example prescription chart:
| SPH | CYL | Axis | Add | Prism | |
|---|---|---|---|---|---|
| OD | -2.00 | SPH | +2.00 | 0.5 BD | |
| Os | -ane.00 | -0.50 | 180 | +2.00 | 0.five BU |
In the right eye (OD), the eye md prescribed:
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-2.00 D sphere for the correction of nearsightedness.
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No cylinder power or axis, which means no astigmatism is present. This dr. chose to write "SPH," to ostend the right center is being prescribed only spherical power. Some doctors will add together "DS" for "diopters sphere" and others will leave it blank.
The left center (OS) was prescribed:
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-1.00 D sphere for nearsightedness correction.
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-0.fifty D cylinder for the correction of astigmatism.
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A cylinder power with an axis at the 180 meridian. This means that the horizontal (180-degree) meridian of the center has no added ability for astigmatism and the vertical (90-degree) meridian gets the added -0.50 D from the cylinder cavalcade.
Both optics were prescribed:
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An "add ability" of +ii.00 D for the correction of presbyopia.
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Prismatic correction of 0.5 prism diopter in each middle. In the right eye, the prism is base of operations down (BD); in the left centre, it'due south base up (BU).
Your centre doctor may besides write specific lens recommendations on your eyeglass prescription. They might propose anti-cogitating coating, photochromic lenses and/or progressive lenses to give you the about comfortable vision correction possible.
Come across RELATED: How "bad" is my prescription?
Can eyeglass prescriptions be used to purchase contact lenses?
No, you cannot use your spectacles prescription to buy contact lenses.
An eyeglass prescription merely works for the purchase of eyeglasses. It does non contain certain information that is crucial to a contact lens prescription.
That data can merely be obtained through a contact lens fitting, an additional procedure that can be performed during your eye physician visit.
Eyeglass lenses are positioned at a distance from the eyes, while contacts rest straight on the optics. That distance affects the lens power required for eyes to focus properly.
In add-on to the information in an eyeglass prescription, a contact lens prescription must specify the base of operations (key) curve of the dorsum surface of the contact lens, the lens diameter, and the specific manufacturer and make name of the lens.
Also, the ability of an eyeglass prescription frequently is modified when determining the best contact lens power. This is because eyeglass lenses are worn some distance (normally nigh 12 millimeters) from the surface of the centre, whereas contact lenses rest directly on the cornea of the eye.
An accurate contact lens prescription can be written only after a contact lens plumbing fixtures has been performed and the prescribing md has evaluated your eyes' response to the lenses and to contact lens habiliment in general.
SEE Too: Contact lens vs. eyeglasses prescriptions
Your eyeglass prescription is yours to keep
The Federal Merchandise Commission (FTC) is the U.Southward. authorities's consumer protection agency. Their Prescription Release Rule requires that eye doctors give patients a copy of their eyeglass prescription at the end of an eye exam that includes a refraction.
The Prescription Release Dominion is intended to permit the "portability" of your eyeglass prescription, giving you the freedom to buy glasses from any vendor of your pick.
Your center doctor must give you a copy of the prescription whether or not you lot ask for it. Eye doctors may non condition the release of your prescription on your agreement to purchase eyeglasses from them, nor may they accuse you an extra fee to release your prescription.
If you think your eye md has violated this rule, you lot tin can report the problem to the FTC.
Page published in February 2019
Page updated in February 2022
Source: https://www.allaboutvision.com/eyeglasses/eyeglass-prescription.htm
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