When ordering glasses online, you may need to know your pupillary distance (PD) to ensure you can see clearly and comfortably while wearing them. However, PD is not equally important for all prescriptions or lens types.
How important is pupillary distance for your specific prescription and lenses? We’ll explain here so you can understand your prescription and feel confident when placing your order.
PD is the distance from the center of one pupil to the center of the other. Glasses manufacturers use your PD to ensure the optical center of each lens is positioned correctly in front of the pupil so you can see clearly without straining your eyes.
Your eye doctor might include your PD on your prescription, but if not, you can ask them to measure it or do it yourself.
For a quick, easy, and accurate measurement, use our Luna tool or explore three other easy methods with our online guide.
PD is the distance from the center of one pupil to the center of the other. Glasses manufacturers use your PD to ensure the optical center of each lens is positioned correctly in front of the pupil so you can see clearly without straining your eyes.
Your eye doctor might include your PD on your prescription, but if not, you can ask them to measure it or do it yourself.
For a quick, easy, and accurate measurement, use our Luna tool or explore three other easy methods with our online guide.
The short answer is that it varies by prescription.
Generally, minor discrepancies in PD aren’t a problem for mild prescriptions. However, the same discrepancy for a stronger prescription or progressive lenses could cause severe vision problems and discomfort.
To help you determine the importance of pupillary distance for your specific needs, here are some clear examples:
Progressive lenses feature a vertical “corridor” or “channel” where the power level gradually changes, allowing you to focus on objects near, far, or intermediate, depending on which part of the lens you look through.
Progressive lenses feature a vertical “corridor” or “channel” where the power level gradually changes, allowing you to focus on objects near, far, or intermediate, depending on which part of the lens you look through.
When wearing progressives, your eyes must align with the corridor to prevent blurry or uncomfortable vision, especially with tasks like reading, using a computer, or looking at the dashboard of a vehicle.
When wearing progressives, your eyes must align with the corridor to prevent blurry or uncomfortable vision, especially with tasks like reading, using a computer, or looking at the dashboard of a vehicle.
If your PD is incorrect, it can throw off the near and far zones of your lenses, making it difficult for you to see clearly or causing uncomfortable symptoms like headaches and eye strain.
If your PD is incorrect, it can throw off the near and far zones of your lenses, making it difficult for you to see clearly or causing uncomfortable symptoms like headaches and eye strain.
According to the ANSI Z80.1 standards developed by the American National Standards Institute, there are set tolerances for pupillary distance. That means manufacturers can deviate slightly from prescriptions, but they should remain within a standard range to ensure the quality and accuracy of the lenses.
However, for prescription lenses with a cylinder power, which corrects astigmatism, there’s less flexibility. As the cylinder power on a prescription increases, the margin for error decreases, and PD accuracy becomes more important. Here’s why:
Misalignment can result in poor vision
If the optical center of a lens with cylinder power is not aligned precisely with the pupil, it can cause the wearer to see prisms, rainbow-like rings, or halos.
Small errors can cause unwanted side effects
For those with more severe astigmatisms and higher cylinder powers, even small PD errors can cause prismatic effects, leading to undesirable side effects like headaches, eye strain, or even double vision.
High-powered lenses are more sensitive to incorrect PD placement
Even a minor deviation in PD will have a stronger impact on the way light passes through these lenses, potentially causing vision problems and discomfort.
| Sphere Meridian Power (minus cylinder convention) | Tolerance on Sphere Meridian Power (minus cylinder convention) | Cylinder ≥ 0.00 D ≤ -2.00D | Cylinder > -2.00 D ≤ -4.50 D | Cylinder > -4.50 D |
|---|---|---|---|---|
| From -6.50 D to +6.50 D | ± 0.13 D | ± 0.13 D | ± 0.15 D | ± 4% |
| Stronger than ± 6.50 D | ± 2% | ± 0.13 D | ± 0.15 D | ± 4% |
| Sphere Meridian Power (minus cylinder convention) | From -6.50 D to +6.50 D | Stronger than ± 6.50 D |
| Tolerance on Sphere Meridian Power (minus cylinder convention) | ± 0.13 D | ± 2% |
| Cylinder ≥ 0.00 D ≤ -2.00D | ± 0.13 D | ± 0.13 D |
| Cylinder > -2.00 D ≤ -4.50 D | ± 0.15 D | ± 0.15 D |
| Cylinder > -4.50 D | ± 4% | ± 4% |
Pupillary distance can be an essential factor when ordering prescription glasses. But whether or not its accuracy will impact your vision depends on your lenses and prescription.
If you have a strong prescription or you wear multifocal lenses, it’s imperative to measure your PD correctly. However, if you have a simple prescription, there’s more margin for error when it comes to PD.
Source: Quick Reference Guide – ANSI Z80.1-2015. (2016). The Vision Council of America.
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