Glasses

Anyone on here tried these?

Glasses

They look worth a punt, never happy with what I get from the optiction and get better results with the cheap ready reader supermarket offerings.

I wear varifocals and it can be incredibly frustrating trying to angle your head to get the tiny screw heads in focus when they are nearly buried in the item when you are doing intricate work, these glasses might just be the answer, definitely worth a try.
Dave W

My wife had one of those marketing emails for these. "50% off for seniors".

Turns out it was 50% off if you bought three. If you bought one it was 30% off making the grand total including shipping and discount, a mere $50 .

So I dug around and found these on eBay for $4.88 (the identical item).

(Assuming the link survives the censorship on this forum)

Edited By Peter Greene on 13/11/2020 22:34:46

Have you tried the little questionaire DaveW on the website? I also wear varifocals but with distance vision correction. The result returrned a negative unlikely to help.

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Following your lead, but being in the U.K. ... I bought a pair for £3.69 with free postage.

They arrived very promptly, in a nice lightweight mailer ... and they are rubbish.

Being a good-hearted chap [probably as a result of the quadruple bypass and the pacemaker], I decided to leave ‘Neutral’ feedback ... at which point ebay suggested that I contact the Seller first

MichaelG.

Edited By Michael Gilligan on 01/12/2020 22:42:58

Oh sure - completely destroy my "it's better to travel hopefully than to arrive" (mine haven't arrived yet)

Actually I was guessing that, if they worked at all, the field of view would be limited and the viewing centres would perhaps shift.

I seem to remember an idea like this on tomorrow’s world, I think the lenses were flexible and a fluid was forced into the space between to change the magnification level. The idea was that in areas without access to optical lense grinding and opticians they could just use these and for many people it would bring an improvement but obviously it will not correct for complex prescriptions, if nothing else is available it could help.

Mike

'My first question is 'how do they work?' Does the screw change actually distort the lens into a different magnification or simply carry the lens further from the eye. This is not a complex zoom lens system.

I also wear varifocals but for fine needs I resign myself to ocassional hand lens additions. When I was working I had an extra flip-down built onto my specs but that prescription is outdated.. You can buy clip-on flipdowns for extra mag but a bit more unwieldy than one's built on the specs. Cheap enough though and a simple shed solution.

High mag was handy for fine surgery but did mean keeping one's head within a set focal distance - quite tiring on long procedures

Chris Evans 6 If unhappy with your opticians solutions you should tell them - or try a different optician

pgk

I'm very short sighted so they wouldn't work for me anyway. I use varifocals but don't find them easy in the workshop. A binocular head magnifier works quite well but I'm avoiding going to the opticians because of the Covid so I got two pairs of reading prescription glasses online from Glassed Direct for about 20 quid and use those in the workshop. You give them your latest prescription and tell them what you want them for and they produce them to suit. So I got a pair for close reading and pair that focus at 2 feet. I find them very useful.

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The short answer is No ... neither of those.

There are two elements to the lens, one of which is displaced laterally by adjustment of the screw.

The concept is interesting, but the execution of the pair that I bought is so bad that it is impractical to even test them.

In due course, I may find time to check the elements between crossed polars ... I expect to observe some quite ‘impressive’ stress concentrations.

MichaelG.

I did buy a pair of these a few years ago

they were fascinating...how badly they were made and ....words fail me how unusable they were.

but they were a good novelty item...everyone who saw them laughed...lucky bag quality didn’t come into it

paypal refunded promptly

Do I understand correctly that the moving lens has a change of mag over a very short lateral distance? That would have to lead to distortions that the fixed lens cannot correct unless the wearer had very good residual accommodation or only views through the very centre of the lens?

pgk

The lens in my pair looked like a reject part from a injection moulding machine and there was 2 of them ...one sliding across the other perhaps 20mm in total ...absolutely impossible to use.

I also buy my glasses from Glassed Direct and have done for the past 5 or 6 years. When the optician gives me my prescription I take it home and insert the details on Glassed Direct platform and a few days later the glasses arrive. They have lots of different frame and styles as do those in the high street, but at a fraction of the cost. Just a satisfied customer. John

Similar laterally sliding lens ideas were investigated a few times by the optical folks in the department of RARDE / DERA / DSLT / QinetiQ that I worked for. I suspect at least once for every incarnation! One of several hardy chestnut ideas from "management" types needing regular debunking.

The theory works fine for a very small field of view and very small collecting optics. Think of two arrays of insect eye like elements moved so as to bring different pairs into alignment immediately in front of the eye. With the rest of the field of view blacked out.

That idea actually has been used for switchable fields of view / magnification on things like weapons sights, infra red imagers and the like. Basic design is a true flat field, parallel light in parallel light out, telescope with a selection of lenses on the back. Simple enough for small fields of view but the design gets hairy fast if you want a large one.

For glasses the optical surface curvatures needed to bring the whole field of view into focus at the right plane regardless of the angle you are looking through them rapidly become impossibly complex in both design and manufacture. In the limit an infinite number of infinitesimally small lenses that can be assembled into an infinite number of pairs all having the same back focal length. Four sets of surfaces. There is no linear equation solution to give acceptable optical quality. There are approximations that can be found quite easily but none good enough.

Obviously not symmetrical as the effects due to sliding is different for vertical and horizontal planes.

Because the instantaneous field of view of the eye is small and because the human brain has a huge amount of processing power to generate useful images from the eyes "signal output" they can apparently sort of work. But the eye is shifting focus every time it moves and the processing applied changes too to get some sort of image. No wonder attempting to use them is a strain. Don't forget that the human eye is always moving to generate a useful image. The true, in focus, field of view is very small.

The cheapy "con trick" ones will at best be lightly parabolic modifications of spherical surfaces.

I think "Buzz' Busselle said that a pair of fresnel lenses rotating about offset centres might get you close! Of course fresnel lenses and glasses don't mix. Shame, life would be so much easier.

The oil filled lens idea mentioned by Mike is impractical. It requires the "bag" material to have physically impossible stress / strain variation with extension curves to create optically viable surfaces over any useful range. I was given a 3 ft diameter concave mirror made on such principles to test. Interferometric results were "interesting" demonstrating that the the theory of design was inadequate. Probably solvable for infra red wavelengths over a short range by manipulating the material thickness but no good for optics.

Clive

Edited By Clive Foster on 02/12/2020 11:37:25

Here [for what it’s worth] is the instruction leaflet:

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Click the images to see a larger version.

MichaelG.

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[my emboldening]

Impossibly tricky for my eyes, as I have fixed-focus [cataract replacement] lenses installed

MichaelG.

I've never had the nerve to ask the optician for my prescription - do they have to give it to you? Somehow seems slightly unfair when they do the eye test and then you go somewhere else for the glasses, but given the prices they charge for frames, I could get over that reservation.

Rob

Rob, yes they have to issue you with the prescription. You or the govt are paying for the eye test.

Tony