Before you buy eyeglasses online, you need to have your latest prescription on hand. If you are not sure about how to enter your prescription online, you may think about sending a fax copy of your prescription or email it to the online store. While getting your prescription is important, don’t forget to also ask for and obtain your PD measurement. These two pieces of information are vital to getting a good pair of corrective vision eyewear.
Different ways of writing the prescription
Keep in mind that no two doctors write their prescriptions in the same way. Typically, you need to have the following pieces of information in your prescription: Sph, Cyl, Axis and Add for both eyes. The SPH is short for sphere and is the main part of your prescription. The Cyl is the short form for the cylinder which shows the strength of your astigmatism if you have one. The Axis is the rotation of the CYL that runs on a plane of between 1 and 180 degrees.
Positive or negative values
When providing your prescription at the time of buying eyeglasses online, you need to understand that the numerical values are either positive or negative. You need to be very careful about entering these signs correctly. If you mix up the positive with the negative, you won’t be able to see clearly through your lenses.
The Sphere shows the strength of your prescription and it increases by 0.25. if you have a nearsightedness problem then your prescription numbers will probably be in the negative. If you are farsighted, then the numbers will be positive.
The PD or pupil distance is a very important measurement as it helps in creating the lenses that will exactly match with your prescription. The center of each lens can only be aligned with your pupils if the correct PD measurement is provided. The PD can be written in many different ways including 62, 32/32. 33/31 and 30.6/33.6 or it can also be written as 62/60.
If the doctor writes your PD at 62 it means to just insert it at 62. If the 32/32 measurement is used, then the two numbers need to be added together to ensure that the insert is 64 or at 32/32.
A PD measurement that is written as 33/31 or 30.6/33.6 means the measurements are from the center of your nose to your pupil on each eye and is not equal for both eyes. In case your doctor wrote your PD measurement as 62/60, then it means the first number is for your distance vision and the second number is for near vision. Normally, your PD for your near vision is about 3 mm less than that of the distance vision.
After obtaining your prescription and PD measurement, you are ready to buy eyeglasses online. Simply choose a frame that is of the right material, size and shape and then choose lenses that work well with your prescription. The last thing you need to do is pick lens coatings for your lenses. Be careful you do not go overboard with the add-ons because they will only add to the total cost of your eyewear.