Since buying prescription glasses online are getting increasingly popular and affordable. Many people take an eye exam and get their prescription first before making a purchase. Before this, there are some points we need to pay attention to, like do you know about your prescription? Which prescription type you should choose? Not to worry, we'll guide you through this and make sure you'll get correct prescription glasses when you shop online.

 1 What are these abbreviations on your prescription?

In your prescription chart, you can find lots of abbreviations and the values. Compare your prescriotion and find the related abbreviations below, you'll have a through understanding your prescription and your eyesight conditions. 

Related: HOW TO READ PRESCRIPTION

OD: right eye

OS: left eye

SPH(Sphere/Spherical): This represents the degree of lens power prescribed to address either nearsightedness or farsightedness. If the value beneath this section is preceded by a minus sign (–), it indicates nearsightedness; whereas, if the number has a plus sign (+) or is not preceded by any sign, it signifies farsightedness. The magnitude of the number following the +/- sign indicates the strength of the prescription, with a higher number indicating a stronger prescription.

CYL(Cylinder/Cylindrical): This value represents the lens power for astigmatism, denoted with either a "+" or "-" sign. However, if you see "DS," "SPH," "spherical," or "PL" mentioned under the "CYL" section, it indicates that you do not have astigmatism.

AXIS: This numerical value denotes the orientation of your astigmatism and is measured in degrees, falling within the range of 1 to 180. Whenever an eyeglass prescription includes cylinder power to correct astigmatism, it is crucial to include an axis value as well. The axis value specifies the specific direction of the astigmatism and follows the cylinder power in the prescription, ensuring precise correction for clear vision.

ADD: Abbreviated as "Reading Addition," this represents the extra correction needed for reading. It is utilized to create reading glasses, bifocal glasses, or multifocal glasses, tailored to meet individual vision needs for close-up tasks like reading.

PD(Pupillary Distance): PD stands for Pupillary Distance. It is the measurement, in millimeters, between the centers of your two pupils. Pupillary distance is an essential value in an eyeglass prescription because it helps ensure that the optical centers of the lenses are aligned properly with your pupils. The average adult pupillary distance (PD) value range is typically between 54 and 74 millimeters. If you don't have this number on your prescription. you may ask your eye doctor for it or measure it with our guides.

Prism: Prismatic power corrects vision displacement, aiding conditions like squints. Measured in Prism Dioptre, values can reach up to 10, increasing in steps of ½ or 1 Prism Dioptre.

PL: "PL" stands for "Plano" or "Plano power." Plano indicates that there is no refractive correction needed for that particular aspect of the prescription. In other words, it means that the lens has no optical power and is used when there is no need for nearsightedness (myopia) or farsightedness (hyperopia) correction in that specific part of the prescription.

Base: "base" refers to the orientation of the prism used to correct vision alignment. It can be indicated as BU (Base Up), BD (Base Down), BI (Base In), or BO (Base Out).

2 Which prescription type you should choose?

If your prescription contains add values, you can choose different prescription types according to your needs:

a. For Multi-Distance Vision:

• Progressive Lenses: If you need to see far, near, and middle distances, choose progressive lenses. Fill in all the values from your prescription.
• Bifocal Lenses: If you only need to see far and near distances, without the middle area, bifocal lenses will work for you.

b. For Distance Vision Only:

• Single Vision Lenses for Distance: If you just need to see far, choose single vision lenses for distance. Ignore the add values and leave them blank, as add values are used to correct near vision, not distance.

Original prescription:

Switch to single vision for distance:

The add value should be 0.00. 

• Single Vision Lenses for Near: If you just need to see near, you need to add the "add values" to the "sph values"; and leave the "add values" as blank.

Original prescription:

Switch to single vision for near:

The right eye sph value should be: SPH+ADD: 2.25+2.50=0.25, and the add value should be 0.00. 

Understanding which prescription type to choose can be overwhelming, but you can make an informed decision according to your needs. If you're unsure which type to choose, you may consult your eye doctor or contact our customer service at service@sllac.com. We'll guide you step by step to ensure you buy the right glasses online.