Snake oil, or not?

[Roger Mills]

I keep getting unsolicited adverts thrust at me in my Twitter feed - two of which I wonder about.

One is for adjustable spectacles, where you twiddle a knob each side to adjust the diopter rating of the lenses. Each lens is in two sections, which move relative to each other. I can't work out whether they slide from side to side or simply move apart axially. The prices in the Twitter adverts are ridiculous - special half price offer for *only* £59

- whereas Amazon and Ebay have very similar offerings for a fraction of that price.

I suspect that they are "snake oil" and that the optics are too poor to be able to see anything clearly. Also, I wonder how you're supposed to clean between the sections of the lenses unless (unlikely) they're hermetically sealed.

Any comments from anyone who has actually tried them?

The other one is for bags filled with bamboo charcoal which are supposed to filter the air and get rid of smells and dust. These may be in with a chance in that charcoal does have some filtration qualities - e.g. war-time gas masks. But unless the air in the room gets circulated through them, they aren't going to do a lot - unless I'm missing something.

Again, informed comments would be appreciated.

[alan_m]

And have you read the amazon reviews?

[Fred]

That?s not the problem, the problem is that they are mechanically very poor.

It shouldn?t get dirty in there.

I did buy one of the cheaper ones but its useless for the reason I stated.

No you arent.

[Dave W]

I have been interested in these but the cheapest ons are £30. They have two lenses on each eye, one of which can be slid sideways by its knob. This can only adjust the strength in the horizontal plane, so will introduce astigmatism (but which may be small and acceptable). Reviews have also said that dirt gets in between the lenses and can't be cleaned.

So not a good buy.

[jon]

I bought a pair from China for £7 and they were very poorly constructed. The left eye adjustment didn't work at all.

[Brian Gaff (Sofa]

There are some which are supplied to those with partial sight, these seem to be a bit like opera glasses but thinner and hinged on the bridge. The idea is to flick them down when a bus is coming and twiddle the knob to get an enlarged but smaller field of view to help read the number. I have never tried them but some people seem to find them useful. The idea of having sufficient adjustment in one pair of glasses sounds a little suspect to me, one assumes plastic lenses or they would be heavy like the ones I mentioned above. As for filters, that sounds like one of the filters used in a clean air room I used to visit. It also had high voltage ionisers and all sorts of other filtration systems in it. Brian

[Brian Gaff (Sofa]

Something like those bags used to be in those Braun air filter things that they sold, but to me an isolated little device circulating air on the sideboard is hardly going to process air over the other side of the room.

There have been devices like this with built in negative ion generators and all sorts but to be honest I've never noticed anything happen in houses where they lifed, better off with one of those plug in stink bomb machines, I mean air fresheners that cause interference to everything and stink the place out like a freshly valletted car.

Brian

[Jethro_uk]

Can't speak to those, but there's been an idea for *years* about using electrostatics to shape a drop of liquid (water - although I guess refractive index might be an issue) to provide an adjustable lens.

One of those ideas which seems to work in description. But I have yet to see the goods.