How Do You Read a Lens 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 force of your vision. They tin can assistance you figure out whether you take nearsightedness, farsightedness or astigmatism — and to what degree.

If yous know what to await for, y'all can make sense of the numbers and abbreviations on your prescription chart.

OD vs. OS: One for each center

Center doctors apply the abbreviations "OD" and "Bone" to denote your right and left optics.

Your eye medico may give y'all a paper prescription that looks something similar this.

• OD is your right eye. OD is short for oculus dexter, the Latin phrase for "correct eye."

• Os is your left eye. Os is short for oculus sinister, Latin for "left center."

Your vision prescription may as well have a column labeled "OU." This is the abbreviation for oculus uterque, which means "both eyes" in Latin.

These abbreviated terms are common on prescriptions for glasses, contact lenses and eye medicines, but some doctors and clinics have opted to modernize their eye prescriptions by using RE (right eye) and LE (left eye) instead of OD and Os.

The information for your right eye (OD) always comes before the information for your left eye (OS). Center doctors write prescriptions this way considering, when they face you, they see your right heart on their left (first) and your left eye on their right (2nd).

Sphere (SPH)

Sphere indicates the amount of lens power prescribed to correct nearsightedness or farsightedness. Lens power is measured in diopters (D).

• If the number nether this heading comes with a minus sign (–), you are nearsighted.

• If the number nether this heading has a plus sign (+), you are farsighted.

The term "sphere" means that the correction for nearsightedness or farsightedness is "spherical," or equal in all meridians of the eye.

Cylinder (CYL)

Cylinder indicates the amount of lens power needed for astigmatism. Information technology always follows the sphere ability on an eyeglass prescription.

The number in the cylinder column may have a minus sign (for correction of nearsighted astigmatism) or a plus sign (for farsighted astigmatism).

If null appears in this column, you either don't have astigmatism, or your degree of astigmatism is so small that it doesn't demand to be corrected.

The term "cylinder" means that this lens power added to right astigmatism is not spherical, merely instead is shaped then ane tiptop has no added curvature, and the meridian perpendicular to this "no added power" height contains the maximum power and lens curvature to correct astigmatism.

Meridians of the centre are determined past superimposing a protractor scale on the heart's forepart surface. The 90-degree superlative is the vertical meridian of the heart, and the 180-caste meridian is the horizontal meridian.

Meridians of the eye are adamant by superimposing a protractor scale on the eye'due south front surface. The xc-caste meridian is the vertical pinnacle of the eye, and the 180-degree meridian is the horizontal meridian.

Axis

Centrality describes the lens meridian that contains no cylinder ability to right astigmatism.

If an eyeglass prescription includes cylinder power, it also needs to include an axis value, which follows the cylinder power.

The axis is defined with a number from 1 to 180.

• The number 90 corresponds to the vertical peak of the eye.

• The number 180 corresponds to the horizontal meridian of the eye.

The centrality is the lens superlative that is 90 degrees abroad from the top that contains the cylinder ability for astigmatism correction.

Add together

"Add" is the added magnifying power applied to the bottom office of multifocal lenses to correct presbyopia — the natural farsightedness that happens with age.

The number appearing in this section of the prescription is e'er a "plus" power, even when you don't run across a plus sign. Generally, it will range from +0.75 to +three.00 D and will be the same ability for both eyes.

Prism

This is the amount of prismatic power, measured in prism diopters ("p.d." or a triangle when written freehand), prescribed to compensate for eye alignment issues.

Only a small percent of eyeglass prescriptions include a prism measurement.

When present, the corporeality of prism is indicated in either metric or partial English units (0.five or ½, for example), and the direction of the prism is indicated by noting the relative position of its "base of operations" (thickest edge).

Four abbreviations are used for prism direction: BU = base up; BD = base of operations downward; BI = base in (toward the wearer'southward nose); BO = base of operations out (toward the wearer's ear).

How they're measured

Sphere power, cylinder power and add ability always appear in diopters. They are in decimal form and more often than not are written in quarter-diopter (0.25 D) increments.

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

When prism diopters are indicated in decimal form, typically merely one digit appears later on the menses (east.m., 0.5).

An example centre prescription chart

Still dislocated? Let's look at an example prescription chart:

	SPH	CYL	Axis	Add together	Prism
OD	-2.00	SPH		+2.00	0.v BD
OS	-one.00	-0.50	180	+2.00	0.5 BU

In the right eye (OD), the eye medico prescribed:

• -2.00 D sphere for the correction of nearsightedness.

• No cylinder power or axis, which ways no astigmatism is present. This doctor chose to write "SPH," to confirm the correct heart is being prescribed but spherical power. Some doctors volition add "DS" for "diopters sphere" and others will get out it blank.

The left eye (Bone) was prescribed:

• -ane.00 D sphere for nearsightedness correction.

• -0.50 D cylinder for the correction of astigmatism.

• A cylinder power with an axis at the 180 pinnacle. This ways that the horizontal (180-caste) meridian of the eye has no added power for astigmatism and the vertical (90-degree) meridian gets the added -0.fifty D from the cylinder cavalcade.

Both optics were prescribed:

• An "add together ability" of +two.00 D for the correction of presbyopia.

• Prismatic correction of 0.5 prism diopter in each eye. In the correct center, the prism is base down (BD); in the left eye, information technology's base upwards (BU).

Your eye doctor may as well write specific lens recommendations on your eyeglass prescription. They might suggest anti-cogitating blanket, photochromic lenses and/or progressive lenses to give you the almost comfy vision correction possible.

Encounter RELATED: How "bad" is my prescription?

Can eyeglass prescriptions be used to buy contact lenses?

No, yous cannot apply your glasses prescription to purchase contact lenses.

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

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

Eyeglass lenses are positioned at a distance from the eyes, while contacts residuum 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 (central) curve of the back surface of the contact lens, the lens diameter, and the specific manufacturer and brand name of the lens.

Too, the power of an eyeglass prescription oft is modified when determining the best contact lens power. This is because eyeglass lenses are worn some distance (usually near 12 millimeters) from the surface of the eye, whereas contact lenses remainder straight on the cornea of the eye.

An accurate contact lens prescription tin be written only subsequently a contact lens fitting has been performed and the prescribing physician has evaluated your eyes' response to the lenses and to contact lens wear in general.

SEE Likewise: Contact lens vs. eyeglasses prescriptions

Your eyeglass prescription is yours to go along

The Federal Trade Committee (FTC) is the U.S. regime'south consumer protection agency. Their Prescription Release Rule requires that middle doctors requite patients a copy of their eyeglass prescription at the finish of an heart exam that includes a refraction.

The Prescription Release Rule is intended to allow the "portability" of your eyeglass prescription, giving you the freedom to buy glasses from any vendor of your choice.

Your eye dr. must give yous a copy of the prescription whether or not you ask for it. Eye doctors may not 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 doctor has violated this rule, you tin study the trouble to the FTC.

Page published in February 2019

Folio updated in Feb 2022

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Source: https://www.allaboutvision.com/eyeglasses/eyeglass-prescription.htm

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