On 25/02/2021 08:29, Andy Burns wrote:
Bob Eager wrote:

alan_m wrote:

But its so easy to measure your PD. Take a selfie with your smart phone
with a ruler held at eyebrow level.

I have got SWMBO to do that. In fact I measure from mid nose to the
centre of my right eye, then double it. That's more accurate - for me.

I took a sneaky photo of the PC screen in specsavers while the person
had gone off to speak to a colleague, they measure the PD and OC per eye

I think the OC is mainly needed for varifocals. For single vision
glasses the optician held a ruler up to determine the PD. For varifocals
I looked through a device and the optician noted stuff or made marks on
something, except when I was using existing frames, when she looked at
me wearing the old glasses and put marks on the lenses.

--
Max Demian