Wrong PD on your glasses? Symptoms and how to check
New glasses feel strange for a day or two while your eyes adapt. But if the strangeness will not fade, one common culprit is a PD mismatch: the optical centers of the lenses do not line up with your pupils.
Typical symptoms of a wrong PD
- Eye strain or fatigue that builds over the day
- Headaches around the brow or temples
- A subtle "pulling" or crossed feeling, as if your eyes are being steered
- Sharp center but smeared or swimming edges
- Worse symptoms with stronger prescriptions
These overlap with symptoms of a wrong prescription, a poor frame fit, or simple adaptation, so treat PD as one suspect among several, not a certain diagnosis.
Why it happens
A lens acts like a prism everywhere except its optical center. When the center is not in front of your pupil, every glance passes through an unintended prism, and your eye muscles quietly fight it all day. The effect scales with lens power: at ±1.00 D a 2 mm offset is barely there; at ±5.00 D it is hard to ignore.
How to check
- Measure your actual PD. Ten seconds with PDgo on a Face ID iPhone, or a few minutes with the on-screen ruler.
- Find what your glasses were made for. Check your order confirmation email for the PD you entered, or ask any optical shop to spot the optical centers with a lensmeter; many will do it free.
- Compare. A difference of 1 mm or less is normal manufacturing tolerance. At 2–3 mm or more with a moderate to strong prescription, contact the retailer; most online stores remake glasses with a corrected PD under their guarantee.
Note: persistent visual discomfort can have many causes. If symptoms continue with glasses made to a verified PD and prescription, see your optometrist.