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How to read a contact lens prescription

Do you want to buy contact lenses online? Great! That saves you valuable time and money. But first you need to know which contact lenses will suit you and how to read a prescription (prescription) for your eye type or optician. After you become familiar with contact lenses, and after you have completed the eye exam, your eye doctor or optician will suggest a specific brand and model based on the characteristics of your eye and the type of vision defect. There are not only differences between daily, weekly or monthly lenses but also different brands that will feel different for each wearer. So it is important to follow the instructions of your eye specialist. Please do not forget that such an eye examination and the corresponding prescription are also necessary for colored lenses, even without diopters. Also, keep in mind that a prescription for glasses is not the same as a prescription for contact lenses, but more on that later. Now let's take a look at all of those numbers and acronyms on your contact lens prescription.

Overview of the parameters

Your prescription consists of 3 main parts: your parameters, a brand recommendation, and special instructions. To make it understandable for you, we have created a small overview that lists all parameters and their abbreviations.

Abbreviationimportance
OD / ROculus Dexter - displays the parameters for the right eye
OS / LOculus Sinister - displays the parameters for the left eye
OUOculus Uterque - indicates that the parameters are the same for both eyes
SP (H), PWR or DSphere, power or diopter value - shows the value for farsightedness or nearsightedness (+ or -)
CYL or CPCylinder - indicates astigmatism and reveals the vertical curve of the eyeball
X, AXAxis - indicates the degree and direction of the cylinder
ADDADD power - shows the additional power for multifocal (varifocal) lenses
BCBase curve - indicates the degree of curvature of the lens
SLIDEDiameter - describes the width of the lens
PLPlano - shows colored lenses with no power
EXPExpiration Date - indicates when the lenses will expire

This table will help you find the right parameters based on your optician's recommendation. But even if it already offers some answers, you will still have some questions. We have therefore listed some frequently asked questions from our customers for you below.

Right or left eye?

Your optician can describe this either with a simple “L” or “R” or with the Latin terms “Oculus Dexter” (right) or Oculus Sinister ”(left). If you have different values ​​for each eye, you have to click "Select parameters for the other eye" when you order in the Alensa shop. There is no left or right decision when ordering, just think of it as Eye # 1 and Eye # 2. If you have the same strength in both eyes, you only have to enter the parameters once and then select the required pack size.



Plus or minus?

Are you nearsighted (myopia), which means that it is difficult to see in the distance. Then your eyesight is indicated by a (-). Are you farsighted and cannot see things nearby? This visual defect is also called hyperopia and it means that your strength is always marked with a (+). This value of strength can be written on your prescription as either a "D" diopter value; "PWR" strength; or "SPH" sphere. Be careful when choosing your strength when ordering, as a small step up or down can make a big difference in vision. If you have ordered the wrong strength, you can return the unopened packaging at any time in accordance with our exchange and return conditions.

Can I also use my prescription for glasses with contact lenses?

NO! The parameters for glasses and contact lenses can be very different, depending on where the respective lens sits in relation to the eyeball. The glasses of the glasses are a few centimeters in front of the eye, while the contact lenses lie directly on the eyeball. Also, your glasses prescription does not contain the necessary information about the correct base curve for contact lenses and the diameter that is right for you.

How do I choose the cylinder and axis for toric lenses?

The cylinder and axis are two units that are necessary for toric lenses to compensate for astigmatism. The cylinder is an extra correction that describes the degree of astigmatism and a minus value that is displayed in steps of 0.25. The axis is specified in degrees between 0 ° and 180 °. We advise you to contact your optician if you have any doubts about these two parameters.

What does the ADD strength mean?

If you have presbyopia and need multifocal lenses, this value will likely be on your prescription. This means "additional strength" and is intended for better close-up vision (reading a book, etc.). The ADD strength ranges from +0.50 to +3.00. Some brands offer ADD strength in low (low), medium (medium) or high (high) levels. CooperVision lenses also differentiate between dominant and non-dominant eyes. If you have any questions about your ADD strength, please ask your optician.

Are the base curve and diameter important when choosing a contact lens?

The base curve shows how strong the curvature of the contact lens is or how close it is to the eyeball. A lower BC value (BaseCurve) such as 8.40 means that the lens is more curved and will therefore fit the eye well. A high value such as 8.70 means a flatter lens. The diameter relates to the width of the lens and is specified in millimeters. Usually it is between 13 and 15 mm. A small difference (0.1 or 0.2 mm) is unlikely to have any noticeable effect on your vision. But if you wear lenses with a significantly different BC or DIA value than prescribed in your prescription, wearing them can be uncomfortable and vision can be distorted. It is therefore essential to follow the values ​​on your prescription.

I lost the paper version of my recipe. Where can I find the information on it?

You may also order contact lenses without a prescription from Alensa. If your last eye examination was not more than a year ago and you have not noticed any major differences in the quality of your vision, you will also find all the important information on your contact lens packaging. We have deciphered this for you:



Please remember that you should have your prescription renewed at least once a year. Even if you don't notice any changes, it is important that your optician examines your eyes.

Can I order trial lenses?

Please note that we are not allowed to offer trial lenses. Only your eye specialist knows your eyes inside out and can prescribe trial lenses for you. But even if we cannot offer trial lenses, there is a money-back guarantee on our TopVue lenses. If for any reason you find them unsuitable, you can return them.