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How to Read Your Eyeglasses Prescription

Making sense of your centre prescription chart

The numbers on your eyeglass prescription relate to the shape of your optics and strength of your vision. They tin can help yous figure out whether y'all take nearsightedness, farsightedness or astigmatism — and to what caste.

If you know what to expect for, y'all can brand sense of the numbers and abbreviations on your prescription chart.

OD vs. OS: One for each centre

Heart doctors use the abbreviations "OD" and "Os" to denote your right and left eyes.

Your eye medico may requite you a paper prescription that looks something like this.

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

• Bone is your left centre. OS is curt for oculus sinister, Latin for "left eye."

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

These abbreviated terms are mutual on prescriptions for spectacles, contact lenses and eye medicines, but some doctors and clinics have opted to modernize their heart prescriptions by using RE (correct heart) and LE (left eye) instead of OD and Bone.

The information for your right middle (OD) always comes earlier the information for your left eye (OS). Eye doctors write prescriptions this mode because, when they face you lot, they meet your right centre on their left (starting time) and your left eye on their right (second).

Sphere (SPH)

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

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

• If the number under 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 ability needed for astigmatism. It 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 nothing appears in this column, you either don't accept astigmatism, or your degree of astigmatism is then small that it doesn't need to be corrected.

The term "cylinder" means that this lens power added to right astigmatism is not spherical, simply instead is shaped so one meridian has no added curvature, and the pinnacle perpendicular to this "no added power" pinnacle contains the maximum ability and lens curvature to correct astigmatism.

Meridians of the eye are adamant by superimposing a protractor calibration on the center's front surface. The 90-degree meridian is the vertical meridian of the eye, and the 180-caste meridian is the horizontal pinnacle.

Meridians of the centre are adamant by superimposing a protractor scale on the middle'southward front surface. The 90-degree meridian is the vertical meridian of the center, and the 180-degree meridian is the horizontal meridian.

Axis

Axis describes the lens meridian that contains no cylinder power to correct astigmatism.

If an eyeglass prescription includes cylinder ability, 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 meridian of the center.

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

The centrality is the lens meridian that is 90 degrees away from the meridian that contains the cylinder power for astigmatism correction.

Add

"Add" is the added magnifying ability applied to the lesser part of multifocal lenses to correct presbyopia — the natural farsightedness that happens with age.

The number appearing in this section of the prescription is always a "plus" ability, fifty-fifty when y'all don't meet a plus sign. By and large, information technology will range from +0.75 to +iii.00 D and will be the same power for both eyes.

Prism

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

But a small percentage of eyeglass prescriptions include a prism measurement.

When nowadays, the amount of prism is indicated in either metric or fractional English units (0.5 or ½, for example), and the direction of the prism is indicated by noting the relative position of its "base" (thickest edge).

Four 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'southward ear).

How they're measured

Sphere power, cylinder power and add together power e'er appear in diopters. They are in decimal grade and mostly are written in quarter-diopter (0.25 D) increments.

Axis 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 only one digit appears after the period (east.k., 0.5).

An example eye prescription chart

Withal confused? Let's wait at an example prescription chart:

	SPH	CYL	Axis	Add	Prism
OD	-ii.00	SPH		+2.00	0.5 BD
OS	-1.00	-0.l	180	+2.00	0.5 BU

In the right eye (OD), the center doc prescribed:

• -2.00 D sphere for the correction of nearsightedness.

• No cylinder power or axis, which means no astigmatism is present. This doc chose to write "SPH," to ostend the right eye is being prescribed only spherical power. Some doctors will add "DS" for "diopters sphere" and others will leave it blank.

The left eye (Os) 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 elevation. This means that the horizontal (180-caste) tiptop of the eye has no added power for astigmatism and the vertical (xc-degree) elevation gets the added -0.50 D from the cylinder cavalcade.

Both optics were prescribed:

• An "add together power" of +2.00 D for the correction of presbyopia.

• Prismatic correction of 0.5 prism diopter in each eye. In the correct eye, the prism is base down (BD); in the left eye, it'due south base up (BU).

Your centre doctor may also write specific lens recommendations on your eyeglass prescription. They might suggest anti-reflective coating, photochromic lenses and/or progressive lenses to give you the most comfortable vision correction possible.

SEE RELATED: How "bad" is my prescription?

Tin eyeglass prescriptions be used to buy contact lenses?

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

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

That information can merely be obtained through a contact lens plumbing equipment, an additional procedure that can exist performed during your eye dr. visit.

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

In add-on to the information in an eyeglass prescription, a contact lens prescription must specify the base (central) bend of the back surface of the contact lens, the lens diameter, and the specific manufacturer and brand proper name of the lens.

Besides, the ability of an eyeglass prescription frequently is modified when determining the all-time contact lens power. This is because eyeglass lenses are worn some altitude (ordinarily about 12 millimeters) from the surface of the centre, whereas contact lenses remainder directly on the cornea of the centre.

An accurate contact lens prescription can exist written simply after a contact lens plumbing fixtures has been performed and the prescribing doctor has evaluated your eyes' response to the lenses and to contact lens vesture in general.

Run across Likewise: Contact lens vs. eyeglasses prescriptions

Your eyeglass prescription is yours to keep

The Federal Trade Commission (FTC) is the U.Due south. government'southward consumer protection bureau. Their Prescription Release Rule requires that middle doctors requite patients a re-create of their eyeglass prescription at the end of an heart examination that includes a refraction.

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

Your middle doctor must give you a re-create of the prescription whether or not you enquire for it. Eye doctors may non condition the release of your prescription on your understanding to purchase eyeglasses from them, nor may they charge you an extra fee to release your prescription.

If you recollect your heart doctor has violated this rule, you can study the problem to the FTC.

Page published in Feb 2019

Page updated in February 2022

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

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