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| Thread ID: 129114 | 2013-02-03 22:09:00 | A tip if you're buying prescription glasses for the first time | BBCmicro (15761) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 1326394 | 2013-02-04 18:04:00 | It's all to do with how the lenses get their curve. Cheap and nasty sun lenses are made from a flat sheet of tinted or polarised material. The material is heated and pressed into the desired curve to make the 'lens'. It's a fast and dirty technique that gives a lens that is riddled with minor optical defects, waves, ripples, dents, pits etc. But adequate for something that's going to be treated poorly and flogged off cheap. Whereas optical quality is more likely to have been made from a much thicker block of material that is then machined (ie ground, cut, polished) into the desired curve and thickness, and will not suffer from the warping issues of a pressed sheet of tint. Much more intensive in terms of the work and machinery that is used to create those curves, but a far superior optical surface. The ultimate in cheap and nasty is a flat lens that has no curves whatsoever. I even got asked yesterday where someone could buy pinhole glasses. Garbage product for suckers. Luckily I have no idea where to source such rubbish. Pinhole glasses are essentially 'technology' from the 1800's. Why someone in 2013 would choose 200+ year old techniques to see is perhaps a reflection of the costs of a modern job, or perhaps the gulibility of the individual making the request. Don't go there! |
Paul.Cov (425) | ||
| 1326395 | 2013-02-04 20:48:00 | The reality is, anybody needing a reading addition of +1.50 or higher is dreaming if they expect a 'single vision' lens to be OK over a wide range of distances Yes, I found that out when I wore my modified +2.25 glasses to the supermarket as a test. Head bobbing up and down trying to get the correct focus, dancing in and out from the shelves to get the right distance... it was hopeless. Actually my prescription glasses are progressive. I should have got prescription glasses earlier but I thought I didn't need them because a distance prescription is not really needed in my case. The advantage of them is that I can read anything anywhere without fishing for a pair of reading glasses. These days Mrs Micro is always asking me to read plant labels, etc, to avoid having to put on her own reading glasses. Other advantages are always knowing where they are, not having to put them down where they can be lost, scratched or bent; good quality frame and lenses; and being able to buy shirts without pockets However prescription glasses are no good for my desktop computer (24", 1920 x 1080) not due to the prescription but to the narrow angle of the progressiveness. I use dedicated +1.5 for this application Although I am pleased with my progressives, we have a friend who doesn't seem able to adjust to hers. So they may not be for everybody The modified glasses in the photo are 'rough as guts' because I don't have a bench grinder. Used an angle grinder and had to hold it down with one hand |
BBCmicro (15761) | ||
| 1326396 | 2013-02-04 22:58:00 | I even got asked yesterday where someone could buy pinhole glasses. Garbage product for suckers. Luckily I have no idea where to source such rubbish. Pinhole glasses are essentially 'technology' from the 1800's. Why someone in 2013 would choose 200+ year old techniques to see is perhaps a reflection of the costs of a modern job, or perhaps the gulibility of the individual making the request. Don't go there! Probably they wanted to look 'cool' in a rap video or something... :lol: |
Agent_24 (57) | ||
| 1326397 | 2013-02-05 04:06:00 | Another hijack ,sorry, Paul I have never been able to wear sunglasses, they seem to stress me out after a while and I develop a headache. I was just curious as to why this would be. | PPp (9511) | ||
| 1326398 | 2013-02-05 06:31:00 | At BBCMicro - I hadn't realised it was a DIY job at cutting down your lenses. I salute your good ol' red blooded give it a go attitude. It's so sadly lacking in many folk these days. If you repeat the job in future, a small tip is to leave a bit more material around the holes where the frame is bolted to the lens, and then it'll take more punishment before the lenses split from those mounting points. A U shaped top edge, a bit like Fred Hollows wore will do the job ok. As for progressives, well sadly, the better progs give wider channels, so to get one that's good on computers means spending a bit more (typically - I won't promise that in every case). I think my latest set are awesome (much better than the previous set), but much like everyone, I hated the price of them (despite getting staff discounts as well). You all have my sympathies, coz it's a tough line between budget progs and premium progs at a premium price, and you need to be able to trust the crew doing the job if you're forking out the dollars for the premium product. It also depends on whether you can trust yourself not to wreck the lenses over the next year or two, otherwise an insurance type scheme on the lenses (OPSM calls it Eyewear Protection Plan) is a sensible choice, otherwise it makes sense to go budget if you're mean on your specs. At PPp, your issue with sunnies probably comes down to having some focussing issues. When your pupils dilate behind a dark lens they are more vulnerable to the effects of any uncorrected visual error. I'd pick you've probably got some latent hypermetropia in one or both eyes, if not some astigmatism as well... it's a fair gamble. Also, see my earlier reply about pressed lenses vs ground lenses. Some folks just can't tolerate the aberrations through a pressed lens. It's unpredictable. No two people are the same in that regard. Some folk are perfectly happy with a pressed cheapie. Others are miserable looking through them. |
Paul.Cov (425) | ||
| 1326399 | 2013-02-05 07:58:00 | Hi Paul, Interesting, I have not had any problems with my eyes, and although having a prediliction to be long sighted I have also been an avid reader most of my life. I have had my eyes checked periodicaly but all seems well, except for reading glasses in my dotage. The sunglasses that have been "put away" for the last 30 odd years have optically ground lenses, they were a last attempt to fit me out with some quality 'sunnies' . It did always interest me why I couldn't wear them. I shall keep you comments in mind at my next appointment with my optometrist |
PPp (9511) | ||
| 1326400 | 2013-02-05 08:20:00 | Thank you Paul for the reply. | Renmoo (66) | ||
| 1326401 | 2013-02-05 08:45:00 | Hi Paul, Interesting, I have not had any problems with my eyes, and although having a prediliction to be long sighted I have also been an avid reader most of my life . I have had my eyes checked periodicaly but all seems well, except for reading glasses in my dotage . The sunglasses that have been "put away" for the last 30 odd years have optically ground lenses, they were a last attempt to fit me out with some quality 'sunnies' . It did always interest me why I couldn't wear them . I shall keep you comments in mind at my next appointment with my optometrist Perhaps you need some transition lens . Here . ( . essilor . co . nz/materials_and_treatments/general_information/transitions_vi/" target="_blank">www . essilor . co . nz) :) |
Trev (427) | ||
| 1326402 | 2013-02-05 20:35:00 | Thanks Trev I will be keeping my optometrist busy. | PPp (9511) | ||
| 1326403 | 2013-02-06 02:01:00 | At BBCMicro - I hadn't realised it was a DIY job at cutting down your lenses. I salute your good ol' red blooded give it a go attitude I'm quite proud of the them! But they don't have the lens and construction quality of the real thing and I never considered doing any more than conducting a test with them My prescription glasses have the maximum width of focus (ie, are the most expensive) but they are not up to desktop computer use (24", 1920 x 1080 px, glasses +1.75). Experimenting just now, the problem seems to be one of 'speed'. My eyes want to flit around the screen at about the same rate as the mouse pointer but I can't adjust my head quick enough and there's a lot of time out-of-focus. The only solution is to have a wider field of focus in the lenses. I note that the angle subtended by the screen is about 2.3x the angle subtended by my Sony tablet, which I don't have a problem with. My cheapie +1.5 glasses are fine for desktop use, and I always know where they are because the desktop screen doesn't move far ;) With my prescription glasses I also got the most expensive frames - 'memory metal'. In retrospect I don't think that was necessary. I got memory metal because I was very hard on my cheapie reading glasses and wanted the mechanically-strongest prescription glasses. But now that I wear glasses all the time I am not nearly so tough on them. I think the main wear on my cheapie glasses was from taking them on and off, leaning over and have them fall out of my pocket*, or putting them down in unwise positions. Going to permanent 'on' means a cheaper frame is now OK. The same applies to getting 2 pairs. The second pair is not really needed now because I am far less likely to lose or damage the first pair (I got 2 pairs - sucked in by the sales talk). The other thing I would consider (if doing it again) is getting larger glasses. I got the largest that the optometrist had, but even larger would be better. I understand that larger glasses have the same real estate for the distance and intermediate vision, but more land for close-up focus? That would be better for reading a smartphone on your chest while watching TV, as you do *on two occasions I started the lawnmower and did not notice that my glasses had fallen out until I got back to the start and heard a 'clink'! |
BBCmicro (15761) | ||
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