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Types of Prescription Lenses

When you shop at JoyLot.com you will find plenty to see! JoyLot.com offers the best prices and selections for all of your eyewear needs. Choose from eyeglasses, prescription eyeglasses, sunglasses, prescription sunglasses and goggles from all the best brands right here and right now! Choose from Judith Leiber, Ralph Lauren, D&G, Carrera, Versace, Dsquared2, Ray Ban, Bolle, Revo, and many others all on sale at discounted prices. As an authorized distributor we guarantee the lowest discounted sale prices on all models. All of our prescription orders filled are custom made to the prescription information that you provide. JoyLot.com recommends you retesting your eyes if your prescription is 1 year old or more. This will ensure that you are getting an up to date prescription enabling you to see your best.

Types of Prescription Lenses

There are 4 prescription lens types. You will have either single vision, bifocal, trifocal and progressive lenses used to complete your Rx order. Your eye exam will yield a prescription that will determine which is right for you:

Single vision lenses - These types of lenses have just one viewing area throughout the lens. The corrected area for vision is set for either far distance, near distance or for reading.

Bifocal lenses - These lenses take care of 2 distinct viewing areas; the first area is for distance and the second is for the near area. The distance area is designed similar to the single vision lens meanwhile the near area consists of the prescription for the distance and the ADD power for viewing at a reading distance. The ADD power is the part of the prescription that tells the laboratory how to make the reading field of your multi focal lens, and this can not be done without an ADD power value.

Trifocal lenses - These lenses are similar to Bifocal lenses as far as the distance and the near area is concerned, but a third line of vision, the intermediate area, is added which is the middle just above the reading area. This viewing area is uncorrected and gives about an arm's length worth of vision.

Progressive lenses - Progressive lenses are used for correcting vision on 2 or 3 areas, without the visual line marks viewed on bifocals and trifocals. Instead of a line there is a seamless progression from one prescription to the next in each viewing area.

Prescription Abbreviations and Terms

In this section you will find some of the most common abbreviations and terms used for prescriptions with their meanings:

SPH or SPHERE - The numerical value under ' SPHERE ' is considered the main part of your prescription. This number measures the strength of the lens in diopters. Diopters is a unit of measurement that simply is the inverse of the focal distance of the lens. Simply put SPHERE is the amount of long or short sightedness and the numerical value is always accompanied with a plus (+) or minus (-) symbol above or in front of it. The plus (+) is used for reading distance and near vision power while the minus (-) is used for distance power.

CYL or Cylinder - This refers to the degree of astigmatism, an uneven roundness present in the cornea's shape which is very common. You will see this value empty if you do not have astigmatism.

Axis - When you have astigmatism , a disturbance in your cornea's shape which is very common , you will need a special cylindrical lens to correct it which must be rotated into a specific position along with the lens strength. The axis represents the rotation amount in degrees ranging from 1 to 180.

Prism - This is used when eyes need to be realigned when looking at the same item. This can happen occasionally, in which case prism is ground into the lenses in order to realign them. When you turn your eye ( known as 'strabismus' ), or when your eye is under tremendous strain but properly aligned you will have this occur.

Base - This refers to the rotation of the prism is specified as ' base in ' or ' base out ' ( ' in ' means towards the nose ) or ' base up ' or ' base down. ' Vertical and horizontal combinations of prisms in the same lens can be used in conjunction with the various base positions.

PD or Pupillary Distance - PD or Pupillary Distance, is the distance in between the center of one pupil to the center of the other pupil. The PD is measured in millimeters (mm) and can also be written in this form: 35/34 ( Normally done if one eye is a little further away than the other from the center of the nose ).

Step 1. Place the ruler at the bridge of your nose (Click here to print a millimeter ruler).
Step 2. Ask your friend to stand an arms length away.
Step 3. Please have your friend measure the distance between the center of your pupils.

( Please be advised that you will still need to contact your optician to get accurate Near and Dist PD measurements required only for bifocal and progressive Rx lenses )

ADD or ADD power - The ADD power is the part of the prescription that tells the laboratory how to make the reading field of your multi focal lens, and this can not be done without an ADD power value.

SEG HT or Segment Height - This is the vertical distance from the bottom of the lens to the bottom of the wearer's lower eyelid if they are wearing bifocals, or the distance to the wearer's pupil for progressives and trifocals.

O.D. or OD - is an abbreviation for oculus dexter, which is Latin for "right eye." (most eyeglass prescriptions simply say "left" and "right" instead of "O.S." and "O.D.") Oculus means "eye." An eye doctor is sometimes called an "oculist" (although eye doctors themselves usually prefer to use either the term ophthalmogist or optometrist, O.D. can also stand for Doctor of Optometry).

O.S.
or OS - An abbreviation for oculus sinister, Latin for "left eye."

O.U.
or OU - An abbreviation for oculus uterque, Latin for "each eye."

D.V.
or DV - An abbreviation for "distance vision". This is specific to the part of the prescription designed primarily to improve far vision. In a bifocal lens, this will normally indicate what is to be placed in the top segment of the lens.

N.V.
or NV - An abbreviation for "near vision". This will usually represent a single vision lens prescription to improve near work, or the reading portion of a bifocal lens.

PL
or plo - An abbreviation for Plano which is used when no correction is needed. The spherical power will sometimes be written as "0.00" and sometimes as "Plano" or "Pl" (because the lens, although not flat, is optically equivalent to a flat piece of glass).

D.S.
or DS - An abbreviation for diopters sphere (it means that you have sphere power only)

X
- This refers to the axis and the number that follows completes the axis value. As an example x 90 stands for axis 090.

Some Important Reminders Concerning Your Prescription


Sample prescriptions

Please be advised your prescription may be written out on a blank Rx pad, it does not have to come on a pre-made Rx sheet ( see the sample prescriptions above). The top values are the prescription for the right eye and the bottom values are the prescription for the left eye.

When there are no numbers for CYL, AXIS or ADD in your prescription, leave these fields blank when ordering. If only one number appears for each eye, it is for the sphere power only.

On some prescriptions there will be no astigmatism correction for one or both eyes. Your doctor may just write the sphere power alone, or may use abbreviations like SPH ("sphere") or D.S. ("diopters sphere").

When you see only one ADD power on your prescription for bifocals, this means that the same ADD power is used for both eyes. Please note if there is no ADD power given, leave this section blank when ordering.

Please note that you may not be able to see well with your new prescription sunglasses if you enter incorrect prescription information such as inaccurate pupillary distance measurement when placing your order! Please note that we cannot be responsible for mistakes in prescription information provided by you or your optometrist or ophthalmologist.


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