The basic function of optical glasses is vision correction. Corrected visual acuity in general needs to go through scientifically optometry, in order to test the right strengths and other relevant parameters. Meanwhile, only in strict accordance with the prescribed parameters can manufactures process qualified and suitable glasses. So we would like to suggest that all consumers go to the formal hospitals to have eyes checked and obtain the prescription.

Pupil Distance (PD)

The accuracy of PD measurement is an important indicator of optometry. In recent years, the PD measuring equipment becomes scientific in its Design, objective and accurate in results, so it is gradually adopted as an optometrist. PD measurement can be divided into Near Vision PD, distance PD and common PD. Sometimes a prescription has two numbers, such as PD 67/64. The former number 67 is your distance vision PD, while the latter is the reading or near vision PD, which is used only if you are ordering simple reading glasses.

The definition of PD

The PD simply means the distance between your two eyes, center to center, the center of one pupil to the center of the other, in Millimeters.

The method of PD measurement

In general, the PD is measured by holding a ruler under the pupils of your eyes and measuring the distance center to center. When measuring, you should be looking straight forward with your eyes fixed on distant objects. We generally don?? recommend you to measure by yourself owing to its inaccuracy. The accurate average PD is about 62mm, and most people may fall within 54 to 74 ranges. If your PD measurement is not within this range, it means that there may be a measurement mistake. So, please make sure that your PD measurement is accurate, which is of high importance to our later designing of glasses.

Commonly, a PD is the sum of measurements of your nose center to either eye, that is to say, Mono R +Mono L = PD. If you are off by a millimeter or two, it really does not matter, but try to be as accurate as you can, especially when you would like to wear progressive prescription glasses. You should also be able to get your PD from your previous eyeglass supplier. This figure does not expire with age, and it is your property for you to own it as well as your full prescription.

Next, we will brief some introductions of data occurred in the prescription, which may be difficult for some customers to identify.

Generally speaking, there are two sets of rows on a specific prescription. Most of the top portion is for your right eye (also called OD), while the bottom portion is for your left eye (or OS).

D.V - the abbreviation for Distance Vision, for Distance correction, there should always be a value under Sphere and most of the time it is negative. However, for Reading-only correction, there should always be a value under sphere and most of the time it is positive. If there is a value under Near Vision---N.V. or N.V.O as the abbreviation, then enter the power in the bottom half of the form and leave the ADD power blank.

About CYL

The Cylinder and Axis is for astigmatism, which means that the eyeball is not wholly spherical, but a little oblong or football shaped. The axis is an angle, from 1 to 180 degrees. For any value of CYL there should always be a value for Axis. If the optometrist wrote SPH in the Cylinder space here it means zero and consequently no Axis as well. The Add part is mostly for the over 40 group and is for bifocal reading or near correction. Some doctors use positive (+) cylinder and some uses negative (-), there is a big difference between the two, so please pay close attention to the positive and negative signs.

For Bifocals and Progressive lenses, please confirm with your optician whether the Addition is for Bifocals or Progressive. Mostly, the Addition of the Progressive is higher by 0.25 than that of Bifocals, so try to verify. If there is only one ADD on the form, it means that the addition for the left and right eyes is the same.

More importantly, you should pay much attention to the plus and minus signs in that they will greatly affect the lens. When you have any question about the prescription, please contact us by email or call or through our Customer Service, and we are willing to help you at any time.

Some Abbreviations

OD (Oculus Dexter) is the abbreviation of the right eye;

OS (Oculus Sinister) means left eye.

The Spherical (SPH) correction is intended for near or far sightedness and PL here means zero.

Don't write the Cylinder and Axis, if you have no astigmatism.

If you have a prescription for multifocal glasses, but you want to order a single vision at our website, just leave off the ADD part unfilled. Our manufacturers will notice and pay attention to it while dealing.

Acquiring this information, if you still have other questions about how to read prescriptions, you can contact us by email or call or through the online live chat. We are ready to assist you at any time.