the Optician: Measuring Your Own Pupillary Distance

the Optician: Measuring Your Own Pupillary Distance:

So you've hung out through my lecture and you want to know how to do it right. It's ridiculously simple. I don't know why no online opticals recommend this. I'm sure people simply assume a slick looking digital system like the one above is more accurate than any manual system, and are inspired with confidence in their cut-rate online supplier. But manual is simply the best for doing this on your own. Here it is:

1. Wear your glasses. (Or any glasses if you don't have your own. Even just try on demo glasses at the mall if you are that bold.)
2. Have a felt-tip maker handy.
3. Focus on a single object in the far distance (anything farther than 20 feet works, but farther is better).
4. Raise the marker to your right lens and precisely put a dot on it directly over the distant object.
5. Repeat for your left eye. If done correctly, with both eyes open the two dots should overlap into a single dot over the distant object. If not repeat making the markings until they do form a single dot.
6.  Measure the distance between the two dots on your lenses with a millimeter ruler.
7. That's your distance PD.
8. If you need a near PD for reading or computer glasses, just do the same procedure but focus instead on the object you will be looking at, either reading material or computer monitor.

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I modified the method a bit: I used 8mm stick on dots and a pair of safety glasses. using a circle on the computer monitor, I placed the dots and then moved them with my fingernail until they had no discernible overlap while looking at the circle. Then I measured them with vernier calipers. Next used a streetlamp outside. For the near vision I got 61 and for distance I got 64. The website you said was the best was quite a bit out, just as you found (58/60). The distance reading was same as Zenni's ruler method and 1mm off what my spouse got using the calipers while I stared at the smoke detector. So the lesson I took away from this is I may have been OK with the distance prescription using the online directions and the printout ruler, but the PD for the readers would have been out by 3mm. One other thing you may want to mention to your readers, if you mark your lenses with a marker, make sure it's not a permanent marker !