Different PD for distance and reading glasses?

mime20

Hi,
My Dad was at Boots getting some new reading glasses. He's had his distance ones done there since 2015 and the same girl used to dispense them with a PD measurement of Right 33.5 and Left 32.5. She's now left and the new girl said the PD for the new reading glasses is Right 31.5 and Left 31.5. She said the PD was different for reading glasses and distance glasses, but I thought PD was just the distance between pupils, so why would it be different between reading and distance glasses?

(I have the PD for my distance glasses and was thinking of getting some reading glasses online for when I do crafting, but won't if I need a different measurement).

Thanks

M

Ames

The optician told me it's because when you're reading you're looking down. If you think about it when you're reading a book you're focusing down and inwards at a point, instead of looking up and around.

mime20

Thanks - that makes sense

pmduk

It's an interesting point, I've never been measured for 2 different PDs, even at Boots (the one time I used them.)

GlasweJen

pmduk wrote: »

It's an interesting point, I've never been measured for 2 different PDs, even at Boots (the one time I used them.)

We don't remeasure, it's a standard distance PD - 3mm to get the reading PD unless there's a prism or other special circumstance.

sillyvixen

The distance pd is more than the reading as the eyes converge when reading. I was taught to measure the distance with a ruler and take 3-4 mm off depending on the total distance pd. Boots policy is now pupilomiters are used to measure pd's and they have a setting for both distance and near, so the process may be the same as last time distance glasses were ordered, the setting will be different for near vision glasses.

kirtondm

Their are various ways of doing it but as indicated your eyes converge for near and it is rarely measured as they normally equally converge and the number can be calculated mathematically.