How Many Frames Per Second Can Your Eyes See

How to Read Your Eyeglasses Prescription

Making sense of your eye prescription chart

The numbers on your eyeglass prescription chronicle to the shape of your optics and strength of your vision. They can help you figure out whether you have nearsightedness, farsightedness or astigmatism — and to what degree.

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

OD vs. OS: One for each eye

Center doctors employ the abbreviations "OD" and "OS" to denote your right and left eyes.

Your heart medico may give y'all a paper prescription that looks something like this.

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

• OS is your left heart. Bone is brusque for oculus sinister, Latin for "left middle."

Your vision prescription may as well take 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 spectacles, contact lenses and eye medicines, merely some doctors and clinics have opted to modernize their eye prescriptions past using RE (correct eye) and LE (left heart) instead of OD and Os.

The information for your right eye (OD) always comes earlier the information for your left middle (Os). Middle doctors write prescriptions this fashion because, when they confront you, they see your right heart on their left (outset) and your left eye on their right (second).

Sphere (SPH)

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

• If the number under this heading comes with a minus sign (–), you lot 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 corporeality of lens power needed for astigmatism. Information technology ever follows the sphere power on an eyeglass prescription.

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

If goose egg appears in this column, you either don't have astigmatism, or your degree of astigmatism is so pocket-size that information technology doesn't need to be corrected.

The term "cylinder" means that this lens power added to correct astigmatism is not spherical, but instead is shaped so i meridian has no added curvature, and the height perpendicular to this "no added power" summit contains the maximum power and lens curvature to right astigmatism.

Meridians of the eye are determined by superimposing a protractor scale on the middle's forepart surface. The 90-caste meridian is the vertical height of the eye, and the 180-degree meridian is the horizontal summit.

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

Centrality

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

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

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 top of the eye.

The axis is the lens peak that is 90 degrees abroad from the meridian that contains the cylinder ability for astigmatism correction.

Add

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

The number appearing in this department of the prescription is always a "plus" power, fifty-fifty when yous don't run across a plus sign. By and large, it will range from +0.75 to +three.00 D and will exist the same power for both eyes.

Prism

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

But a pocket-size pct of eyeglass prescriptions include a prism measurement.

When present, the corporeality of prism is indicated in either metric or fractional English language units (0.v 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'due south ear).

How they're measured

Sphere power, cylinder power and add power always appear in diopters. They are in decimal form and generally are written in quarter-diopter (0.25 D) increments.

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

When prism diopters are indicated in decimal grade, typically only one digit appears after the menstruum (e.g., 0.5).

An example eye prescription chart

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

	SPH	CYL	Centrality	Add	Prism
OD	-2.00	SPH		+2.00	0.v BD
Os	-1.00	-0.l	180	+2.00	0.5 BU

In the correct center (OD), the eye dr. prescribed:

• -2.00 D sphere for the correction of nearsightedness.

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

The left center (Bone) was prescribed:

• -1.00 D sphere for nearsightedness correction.

• -0.fifty D cylinder for the correction of astigmatism.

• A cylinder power with an centrality at the 180 meridian. This means that the horizontal (180-caste) tiptop of the eye has no added ability for astigmatism and the vertical (ninety-degree) meridian gets the added -0.50 D from the cylinder column.

Both eyes were prescribed:

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

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

Your eye doctor may as well write specific lens recommendations on your eyeglass prescription. They might advise 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 exist used to buy contact lenses?

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

An eyeglass prescription only works for the purchase of eyeglasses. It does non contain certain data that is crucial to a contact lens prescription.

That data can only be obtained through a contact lens plumbing fixtures, an additional process that tin be performed during your eye doctor visit.

Eyeglass lenses are positioned at a distance from the optics, while contacts balance directly on the eyes. That distance affects the lens power required for optics 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 make proper noun of the lens.

Also, the power of an eyeglass prescription oft is modified when determining the all-time contact lens ability. This is because eyeglass lenses are worn some altitude (normally most 12 millimeters) from the surface of the eye, whereas contact lenses residuum straight on the cornea of the eye.

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

Run into Too: Contact lens vs. eyeglasses prescriptions

Your eyeglass prescription is yours to keep

The Federal Merchandise Commission (FTC) is the U.S. authorities's consumer protection agency. Their Prescription Release Rule requires that center doctors requite patients a copy of their eyeglass prescription at the end of an heart test that includes a refraction.

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

Your centre doctor must give you a copy of the prescription whether or not you ask for it. Center doctors may non condition the release of your prescription on your understanding to purchase eyeglasses from them, nor may they accuse you an actress fee to release your prescription.

If yous think your eye medico has violated this rule, yous tin report the trouble to the FTC.

Page published in February 2019

Folio updated in January 2022

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

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