Updated: Sep 4, 2019
If you've ever purchased glasses online, you probably noticed that in addition to the numbers used for the glasses prescription, you need to enter one additional number. That extra number is called your Pupillary Distance, or PD, and it's a measure of exactly how far apart your eyes are, down to the half-millimeter. Typically when glasses are ordered by an optician, the measurement is taken very accurately with a pupillometer.
So if you are trying to save money by skipping the optician and buying glasses online yourself, what is the best way to obtain this measurement? You could use a ruler and a mirror or try to get a friend to help you- but we don't recommend it. Because if the measurement is off, even by a little bit, it can cause blurry vision, eyestrain, and headaches.
Chances are your PD exists on file already at your optometrists office. So, why not just call and ask for it? Sometimes, its not that easy. Many offices prefer not to give out the PD, or charge a fee for it. Because they know if you need the PD it means you are going to the internet for your purchase. Seems obvious to you that they withhold a PD to force you to buy from them! How rude! Well, let me present their point of view in a slightly different light.
Imagine you need to buy a nice suit. You head over to a specialty shop and try on a few things and get measured with a tape measure by a person who has plenty of expertise. But after hearing the price, you have second thoughts and go decide to compare prices. You check out prices of suits online and the prices are great. So you call the shop and ask for your inseam, waist measurement, etc. and happily place the order online. Pretty savvy right? Some would argue, that's not savvy- that's stealing. Because this person who took your measurements pays for rent, inventory, and employees to be able to provide this buying experience for you. If customers continue to come in and get these services without purchasing, how is this business supposed to stay afloat? By charging a fee for the measurements? By refusing to give them away, while risking spoiling their reputation? There is no good answer. Optometrist and opticians face the same predicament when a patient asks for the PD. After all, they paid a highly trained employee and used an expensive piece of equipment to take that measurement, with the hopes of making a sale.
Personally, I feel differently. I ALWAYS give out PDs because I never want to give the impression that the only reason I am prescribing glasses is to sell them. My prescriptions are genuinely what will work best for you whether you buy them from me or don't buy them from me. I am a doctor first, and a salesperson second. By design, my collection of frames is good quality products, and for that reason they may be out of price range for some. I never want my patients to feel shame if they need to make the financial decision to buy glasses elsewhere. I never want my patients to feel awkward about asking my staff for a copy of the prescription or the PD, so we give it to you before you even ask. After all, it is your medical records, and technically, that belongs to you. Sure, I might be losing a little bit of time and money by taking everyone's PDs and giving them away. But that is a small courtesy I am happy to do because I love helping out my patients.
PS. I do feel the need to warn you that sometimes getting glasses online is not a safe option, especially for kids. By law, glasses in the United States prescribed to anyone 18 and under have to pass safety standards for being impact resistant. Sometimes when glasses are ordered online, they come from countries where those safety standards don't exist- so they could be more prone to shattering. More on this topic another time.