1. augmented reality could get real and good very fast. Lots of people will be comfortable testing glasses at home instead of checking the optician. Visiting the optician is the most awkward shop I go to.
2. How long before we have advanced cameras and the eye test could be done online? Well, I think a bit longer than I'd think but that's in the realm of possibilities.
Also some conditions such as glaucoma can be difficult to test (http://www.glaucoma.org/glaucoma/diagnostic-tests.php). I remember one of the tests is to use a tonometer to check pressure by firing a puff of air at the eye, so for any of the tests today that give output values, these could feasibly be administered at home but wouldn't form a complete picture of our eye's health.
Interesting to think what an "opticians" could be in 20 years from now.
As I understand their logic is that the PD is part of the fitting process for the glasses and not the optical prescription.
Perhaps they obtain frame measurements at the same time as they measure PD. But the machine is capable of measuring PD alone.
Try another store/human.
I don't doubt that it could be measured as part of the optical prescription process but it isn't as far as I've seen. I'm in the UK.
As noted elsewhere in this discussion, it was expensive before. Independent opticians feel attacked on one side by e-commerce, and on the other side by Essilor/Luxottica, chains in general, and big-box stores The real issue may be that they can't see the value in changing how they have always worked or that even if individual opticians are open to change, they are stuck in a supply chain that may hold exactly the opposite view.