inter-pupillary distance

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simonineaston
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Joined: 9 May 2007, 1:06pm
Location: ...at a cricket ground

inter-pupillary distance

Post by simonineaston »

Tidying up just now, I found the simple ruler I made to measure my own pupillary distance as it was missing from my last eye prescription printout. You're supposed to look through the pinholes at a distant object then measure how far apart they are. Specsavers now have a natty online tool, so I was interested to see that they agreed.
https://www.specsavers.co.uk/glasses/bu ... y-distance
2 bits of card and a bulldog clip
2 bits of card and a bulldog clip
May be of use to those who wish to buy prescription eyewear online.
S
(on the look out for Armageddon, on board a Brompton nano & ever-changing Moultons)
Psamathe
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Joined: 10 Jan 2014, 8:56pm

Re: inter-pupillary distance

Post by Psamathe »

My prescription never has inter-pupillary distance. I'm currently going through the "grief" of a new pair of glasses (last pair 15 years ago!). Managed to find some frames that I could wear, got new prescription, purchased frame and lenses from same optician (shop) massively expensive.

It was one of the "assistants" who then did all the measurements after the optician established the prescription - although assistant is probably the wrong title.

1st pair was a disaster. Couldn't focus on reading or computer unless far too close but even worse, sides of my laptop were no longer parallel and a square was pincushion - despite having paid lots extra for the special Nikon lenses that avoid distortion. Had another optician appointment yesterday for new prescription and assistant re-did all the other measurements for pupillary distance and loads of others readings.

This time he decided on a different lens form, many of the measurements differed from just a week before (lens to pupil, pupillary distance, angle of frames, etc.).

So in a few days I'll be finding if I can use these newer ones. Glad I paid the higher price for a retail optician as I seem a "difficult case".

Ian
Edit: I would say this has really brought home to me the importance of the non-prescription measurements but I don't as yet have any idea if the new set of measurements/lens design is going to make a difference.
thirdcrank
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Joined: 9 Jan 2007, 2:44pm

Re: inter-pupillary distance

Post by thirdcrank »

This is almost like being able to remember our (LICS) Co-op number from the 1940s and about as little use in 2022 although it doesn't go back so far. The first substantial purchase I made when I had money in my pocket (1964) was a pair of binoculars on special offer in an optician's window. The optician set them up for me including measuring the distance between my pupils. (The alternative being to move the two eyepieces apart till things seem right.) So, mine is 69 and I've never been asked for it since. Ditto our Co-op number.
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simonineaston
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Re: inter-pupillary distance

Post by simonineaston »

The story of the ipd measurement is mildy interesting, at least from the pov of us customers. As far as I can tell, eons ago it simply formed part of the standard set of measurements that the optician took when you were tested. Before the advent of bifocal / varifocal lenses, it may not have been very critcal. After the high street franchises arrived and prices got keener, I think it became one way retailers could use to get some leverage over customers, ie the results of the measurement taken as part of free eye tests were withheld from the prescription if the customer asked for a copy.
With the advent of the next development, of shopping online for eyewear, there came a hiatus. The ipd was important for wearers looking to buy certain types of lens. Customers either had to press whoever did their test for it or else, do it themselves - which to be honest isn't that hard! The outfit that carried out the eye test - often those high street franchises, for reasons of geographical convenience, were naturally keen to retain the business and so obtaining the ipd could be subject to resistance.
Now that more & more business is done online it, appears the next step has been taken, that of the ipd measurement being taken via the retailer's website and the buyer's devices camera. Interesting!
S
(on the look out for Armageddon, on board a Brompton nano & ever-changing Moultons)
Bonefishblues
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Location: Near Bicester Oxon

Re: inter-pupillary distance

Post by Bonefishblues »

Lots of apps in Apple/Googles stores
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Mick F
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Re: inter-pupillary distance

Post by Mick F »

Mirror. Fixed on the wall.
Fine nib felt pen.
Wear your glasses.
Dab a spot of felt pen on your glasses where your pupils are.
Remove your glasses, and use a ruler.

Simple.

I used that technique to order my previous Optilabs cycling glasses ............. and my present ones too.
Perfect.
Mick F. Cornwall
Psamathe
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Joined: 10 Jan 2014, 8:56pm

Re: inter-pupillary distance

Post by Psamathe »

One aspect that was explained to me by the optician retailer (yesterday and during the issues) is that your brain is very good at adapting to things wrong with your glasses. I will admit/assume I am particularly sensitive to distortions (e.g. laptop screen sides not appearing parallel) but optician taking measurements was also measuring and coping some from my old glasses because they were OK and my brain had adapted to any distortions they had been causing.

So I would wonder about if you got the DIY measurements wrong, would you actually necessarily notice after a couple of days? (I'd assume a lot will depend on your prescription, any astigmatism, type of optics e.g. distance, near, bi/vari-focal, etc.).

Ian
thirdcrank
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Re: inter-pupillary distance

Post by thirdcrank »

Psamathe wrote: 6 Dec 2022, 3:36pm One aspect that was explained to me by the optician retailer (yesterday and during the issues) is that your brain is very good at adapting to things wrong with your glasses. I will admit/assume I am particularly sensitive to distortions (e.g. laptop screen sides not appearing parallel) but optician taking measurements was also measuring and coping some from my old glasses because they were OK and my brain had adapted to any distortions they had been causing.

So I would wonder about if you got the DIY measurements wrong, would you actually necessarily notice after a couple of days? (I'd assume a lot will depend on your prescription, any astigmatism, type of optics e.g. distance, near, bi/vari-focal, etc.).

Ian
Looking down the other end of the spyglass, I fancy this is one of the things it's so easy to get het up over that a lot of other things get out of proportion.
Psamathe
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Re: inter-pupillary distance

Post by Psamathe »

thirdcrank wrote: 6 Dec 2022, 3:42pm
Psamathe wrote: 6 Dec 2022, 3:36pm One aspect that was explained to me by the optician retailer (yesterday and during the issues) is that your brain is very good at adapting to things wrong with your glasses. I will admit/assume I am particularly sensitive to distortions (e.g. laptop screen sides not appearing parallel) but optician taking measurements was also measuring and coping some from my old glasses because they were OK and my brain had adapted to any distortions they had been causing.

So I would wonder about if you got the DIY measurements wrong, would you actually necessarily notice after a couple of days? (I'd assume a lot will depend on your prescription, any astigmatism, type of optics e.g. distance, near, bi/vari-focal, etc.).

Ian
Looking down the other end of the spyglass, I fancy this is one of the things it's so easy to get het up over that a lot of other things get out of proportion.
Quite possibly. The initial lenses had apparently been made flatter than my current very old set and optician guy said the replacement lenses he wanted to make same outer curvature. I raised "Doesn't flatter mean less distortion?" and he said it did but that my brain had acclimatised to my current lenses so safer for 2nd attempt to go for same outer curve.

I do find sides of computer screens not being parallel particularly noticeable - brain seems to "know" they should be parallel but they aren't ... Initial re-test couple of days ago, they gave me a test print book and my 1st comment was that it was not rectangular!

Unfortunately I couldn't persist with the new lenses so couldn't give my brain a chance to acclimate as I couldn't focus on laptop nor Kindle nor printed book without them being ludicrously close to my face) so when the repeated the prescription tests they also came-up with a lower reading prescription (though reassuringly got the slight astigmatism identical).

Ian
irc
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Location: glasgow

Re: inter-pupillary distance

Post by irc »

I wear bifocals. I'm happy to order most things online but for my specs think the high street adds enough value to be worthwhile.

For bifocals as well as the pupil distance needing to be correct the line between the insert for close work and the upper part of the lense needs to be at the right height.

I got an online quote - £66 for one pair.. Two pairs from Specsavers £180. Not a huge amount for something I wear all day every day.

The other benefit of buying local being if there are any issues or if something breaks many months down the line they repair for free without ny posting hassle involved.
Psamathe
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Joined: 10 Jan 2014, 8:56pm

Re: inter-pupillary distance

Post by Psamathe »

Another example yesterday about how good glasses need a lot more measurements than just the inter=pupillary distance. After the issues with the 1st set a week ago, optician said they'd re-make the lenses so had the measurements done again, incl. things like lens "form"(?) where they chose the curvature of the outer surface.

Collected 2nd attempt yesterday and laptop screen wider on the left than on the right (like a flower pot on it's side). discovered that if I hold the galsses above/higher than the bridge of my nose (i.e. as though the bridge of my nose was higher up) then laptop rectangular again.

On 1st attempt the optician had me wear the glasses and he drew horizontal line at the level of my pupils. 2nd attempt different optician decided he's allow Nikon to default that setting so only drew vertical lines. Looks like that horizontal line is an important measurement not to default (lens manufacturer will default any measurements not supplied by the optician).

So today decided I'm not going to keep bouncing back and forth and not go for 3rd time lucky and went for a refund - it was a lot of money and still they couldn't get it right.

And that's just for reading glasses (no distance, no bi/vari anything).

Ian
axel_knutt
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Joined: 11 Jan 2007, 12:20pm

Re: inter-pupillary distance

Post by axel_knutt »

I need adjustable frames, they're fine at this moment, but the spacing has been too wide for most of the day up until now.
“I'm not upset that you lied to me, I'm upset that from now on I can't believe you.”
― Friedrich Nietzsche
Stradageek
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Joined: 17 Jan 2011, 1:07pm

Re: inter-pupillary distance

Post by Stradageek »

I used microscopes at work and I use binoculars at home - simply reading the gradation on either tells me my IPD is 65mm :D
axel_knutt
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Joined: 11 Jan 2007, 12:20pm

Re: inter-pupillary distance

Post by axel_knutt »

There wouldn't be much point in measuring mine.

When my left eye feels 'wrong' I have to turn my head to the right when looking through the left lens and to the left when looking through the right lens, ie: everything is behaving as if the lenses are too far part. When my left eye is feeling ok, 'normal', the lenses feel right, and I can see clearly through both at the same time, without turning my head.
“I'm not upset that you lied to me, I'm upset that from now on I can't believe you.”
― Friedrich Nietzsche
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