im back

[Mike Ayling]

Gents, could you explain why glass lenses are better than plastic.

Thank you.

[Jags]

That's one for Andre.all my glasses are plastic or whatever the technical name is but after a few weeks of use its hard to keep them clean fog free.

[John Saxby]

In my experience, Mike, er, "It depends..."

My single-vision sunglasses have glass lenses, though the right lens is very thick indeed towards the edges.  Those lenses are also larger in surface area than my clear progressives, which are made of plastic.  Reason for that is that my eyes (esp the right one) are so weak that the progressive lenses (with three ranges of acuity) would not fit in any of the frames available if made of glass.

[Andre Jute]

Gents, could you explain why glass lenses are better than plastic.

I've never had plastic lenses that didn't scratch sooner rather than later. It seems to me, too, that one's vision is clearer with glass than the best plastics. Glass takes better than plastic to cleaning with mist reducers, an important point Anto made: it can be dangerous cycling with misted glasses: plastic lenses may come from the supplier with a coating of anti-mist oil on them, but it soon washes and wears off.

In addition, all my spectacles are progressively photochromatic, even the ones I wear only in my study, where the drapes are drawn all the time, because the slight tint the glasses take on from the glare of the Mac screen, which then cuts the glare, is huge in preventing migraines.

My single-vision sunglasses have glass lenses, though the right lens is very thick indeed towards the edges.  Those lenses are also larger in surface area than my clear progressives, which are made of plastic.  Reason for that is that my eyes (esp the right one) are so weak that the progressive lenses (with three ranges of acuity) would not fit in any of the frames available if made of glass.

I'm surprised to hear this, John. I used to have the same problem, that I had to choose frames with not too much depth before the eye because otherwise the edges of the glass would be too thick, and the completed spectacles would be abnormally heavy. The same reasoning, plus insufficient eye movement, also prevented me getting varifocals. But with new knowledge and processes, and essentially new eyes, for the first time I can now have progressive focal lengths -- and they're progressively photochromatic, and everyone in my family noted how thin the edges are compared to the old lenses. I just gave the optician Armani and Nautic frames to which I'm particular because I didn't realize how thin the new lenses would be.

But now I dwonder if I shouldn't have chosen new, larger frames so they could do double duty as cycling sunglasses. I have cycling glasses with prescription plastic lenses behind the huge tinted and curved over-lenses, but they suffer the misting problem Anto alludes to, so I'd be very happy with cycling glasses with glass prescription lenses, but they'd have to be larger than the spectacles I have now to offer my eyes protection against the airflow and chips of gravel thrown up by passing cars.

Cost of eye test and two pairs of complicated glass lenses, no new frames, 460 Euro, at an optician I've gone to for decades, three times what it cost ten years or so ago. I wonder how much of that, after carriage both ways and inflation, is accounted for by people accepting plastic lenses and thereby destroying the local optical glass grinding industry.

[Mike Ayling]

Thank you Gents

Mike

[John Saxby]

Thanks, Andre.  Complicated bizness, innit?

I'll have to renew my single-vision sunglasses and (probably) my progressives later this summer, so we'll see how it all plays out.  The coating of the glass lenses in my sunglasses is seriously mottled, and they do double-duty, for both driving the car and protecting my eyes while cycling, so that's the priority.

I may stay with my progressives a while longer -- am due to be checked again for possible cataract surgery next Feb.  OTOH, the increasingly common practice among manufacturers and retailers, of using 6-point font and grayscale print in their instructions in manuals & on boxes means I often slide the glasses to the end of my nose & bring the box/whatever to within a couple of inches of my eyes, before saying, "Ah, so that's what we have to do." 

[Danneaux]

I often slide the glasses to the end of my nose & bring the box/whatever to within a couple of inches of my eyes, before saying, "Ah, so that's what we have to do."

Oh, the joys of the natively myopic, counting myself amongst their number. Secret weapon for deciphering fine print...until middle-age presbyopia sets in!

I have progressives for a backup but my "daily driver" is a single contact lens for distance and mentally switching between the clearest/dominant image at various focal lengths.

Best, Dan.

[Andre Jute]

Thanks, Andre.  Complicated bizness, innit?

I should probably apologize to Mike. But my optician, Barry Hurley on Market Street in Bandon, and his young associate, John Egan, makes it painless to find one's way through the maze. I didn't realize it was so complicated until I tried to explain to Mike.

I went to the chain opticians only once, many years ago, and came away with the feeling that they hated people to come in with complicated eyes because they want to prescribe standard lenses which aids a high throughput of cases. They make most of their money from selling overpriced "fashion" frames. When I told the "optician" that I wanted my glass lenses in frames that I designed twenty years before for a Viennese frame-maker (I don't tell you his name because his children have really screwed up what was one of the greatest of the frame makers) and here are the prototypes which have another twenty years of service in them, she looked at me like I was crazy and said, "Men in Milan now have different glasses to go with different suits." When I replied, "I'm more about substance," she said, "You're not as funny as you think." I left without ordering anything, wondering if her attitude was a response to my pheremones or a class reaction or what she'd been taught to say by rote, and went to find a local optician, which is what I should have done in the first instance.

The coating of the glass lenses in my sunglasses is seriously mottled

Best to think of a photochromatic lens as a closely adhesive living crystal colony, or if you're a diver, a slice through a coral reef. The crystals in the lens, like all living things, have an expiry date: they die and the darkening effect gets less and less over the years.

OTOH, the increasingly common practice among manufacturers and retailers, of using 6-point font and grayscale print in their instructions in manuals & on boxes means I often slide the glasses to the end of my nose & bring the box/whatever to within a couple of inches of my eyes, before saying, "Ah, so that's what we have to do." 

Near the beginning of the previous century, Beatrice Webb, the mother of modern typography and one of the founders of the Fabian Society, said in paraphrase that "Graphic design should by like fine crystal surrounding a great vintage wine, invisible." Every time I hear someone in a dull black two-button suit with a thin black tie describe himself (!) as a "leading edge designer", I know without further discussion that he will try to put his own dull personality first rather than the client's product, and say, "Thank you, we'll let you know." When I held up Mrs Webb as a fount for all designers to honor in a book packaged by the last of the Bauhausers, who died during the production of the book, which is now used in applied arts courses around the world, all the favorable reviewers agreed approvingly that I was "the arch-conservative of typography". Specifically referring to the current pandemic of nearly invisible, unreadable text, Apple is responsible in its own materials for starting this nonsense, and the whole groupthink of edgelords followed them over the edge into treachery to their profession. That's about as edgy as they get.

Here's a tip. Your phone probably has an app that translates text in a photograph to manipulable text in a word processor. I take a photo of any text longer than a few lines in these stupid presentations, using my iPad Pro (a 13in tablet; my everyday phone is the physically smallest iPhone, too small to read on comfortably), and then I simply translate it into black text on white, at a size that I can read. I takes only seconds. For a whole book, I guillotine off the binding, and put the stack of newly single pages through a photocopier twice to get both sides of every page, saving to a flash key, which I then put through a professional optical recognition (OCR) program, and voila, I have something I can read.

my "daily driver" is a single contact lens for distance and mentally switching between the clearest/dominant image at various focal lengths.

Yah. When I saw that photo, mocked up to demonstrate your diplopia, you published during your traverse of Europe on the Thorn bike that grand forum member Andy lent you, I said to myself, "You may be going blind, Andre, but be grateful you don't have Dan's problems."