Loading...
Loading...
The PD Journal
Plain-language guides on measuring PD, reading a prescription and ordering glasses online, written to be checked against the sources they cite.
Everything you need to know about PD—what it is, why it matters, and how it affects your glasses prescription.
Step-by-step instructions for measuring pupillary distance accurately without visiting an optometrist.
Use a bank card as a ruler: setup, steps, what the software does with the photo, and what limits accuracy.
Camera distance, angle, lighting and upload tips for a clean selfie-based PD measurement.
Card not detected, head turned, eyes closed, out-of-range result, camera blocked: what each message means and how to fix it.
Pupil detection, scale object, depth offset, head turn and eye convergence, explained with numbers.
The near-PD rule of thumb, a conversion table for common reading distances and a worked example.
Convert a single PD into two eye values and back, with tables and the mistakes to avoid.
PD formats, prescription abbreviations (OD, OS, SPH, CYL, AXIS, ADD) and what to do if PD is not listed.
Why glasses interfere with photo-based PD measurement and what to do instead.
How a small PD error turns into unwanted prism, with a table by lens power and error size.
Face and iris detection, card scale, perspective and convergence corrections, and what the tool does not do.
Six practical checks: repeat readings, normal range, left/right balance, old prescription, second method and reported error.
Cost, equipment, error sources and best use for every common way to measure PD.
Seven causes of inconsistent readings and a repeatable routine that fixes them.
What stays in your browser, what the page downloads, and what is stored locally.
Understanding the optical science behind pupillary distance and its impact on vision quality.
When single PD works and when you need separate measurements for each eye.
Special considerations for measuring PD when ordering multifocal or progressive glasses.
The most frequent errors people make when measuring pupillary distance and their solutions.
The business and medical reasons behind this common frustration—and what you can do about it.
A technical analysis of smartphone and web-based PD tools compared to professional measurements.
How pupillary distance develops in children and what parents need to know.
How incorrect pupillary distance contributes to visual discomfort and what to do about it.
Comprehensive data on pupillary distance norms across different demographics and populations.
Special considerations for people with strong prescriptions where PD accuracy is critical.
Common misconceptions about pupillary distance and the truth behind them.
Everything you need to know about PD when ordering prescription eyewear from online retailers.
Understanding near PD and why reading glasses have different requirements.
How to get the right PD for intermediate-distance computer and office glasses.
How pupillary distance measurement evolved from simple tools to modern technology.
When one number works and when you need two separate measurements.
How pupillary distance develops from childhood through adulthood.
Special considerations when ordering prescription sunglasses online.
Understanding the relationship between face shape, PD, and frame selection.
Use our free online tool to get an accurate measurement in 30 seconds. No special equipment needed.