*Bonjour et merci for posting this at just the time I, too, have a question about lens choice.
I want the best optics possible. Someone I spoke with suggested that CR39 (which is also least expensive) has better optical qualities -- which seemed to mean less distortion -- than polycarbonate. Can anyone here enlighten me further about that? My Rx is primarily for a high degree of astigmatism, but I don't think I need to spring for a high-index lens, since only part of the lens will look thick. Furthermore, these are going to be reading/computer lined-bifocals (so fashion is relatively unimportant here). My thanks for any clarification any of you can give. Jane* On Sun, Jan 25, 2009 at 2:57 PM, Chuck Knight <[email protected]> wrote: > OK, let's take your questions in order. > > 1) The numbers you mention are refractive indexes. The bigger the number, > the thinner the lenses will be. Only you can decide whether the difference > in cost is justified, but to make it easier, opticampus has an online lens > thickness calculator. You enter in your prescription, and it estimates the > thickness of the lens edges. > > http://www.opticampus.com/tools/thickness.php > > 2) UV coatings are a way to make the lenses resist UV light. Each > retailer produces a different product, so the easiest way to see if it's > included is to read the description. If you're in doubt about the > details...ask the retailer. > > To further complicate matters, UV (ultraviolet) resistance is inherent to > the 1.56 polycarbonate material -- the other lens materials may or may not > have UV resistance built in. > > 3) AR is Anti-Reflection. It's a coating that makes the lenses less > visible, and makes them reflect light less obviously. Here is a video that > explains it quite well. > > http://www.youtube.com/watch?v=WLEmSsIqw4Q&feature=channel > > 4) Semantics, though if you're in doubt, ask someone at the dispensary. > > 5) Tints are rated in percentage form, by how much light they block. i.e. > 40% is less opaque than 80%. Most companies will make only 80% or less. > > 6) It's just a way to block light. I, personally, wear a pair of 80% dark > amber lenses...brown, in your parlance. They work great, and I like them > very much. My previous pair of sunglasses was 80% gray...from a functional > standpoint, it's the same thing, but with a color shift. The colors through > gray were more neutral. > > 7) Gradient tint... > > 8) I'm sorry, but I never took French. If there's something on your > prescription that you don't understand, I *always* say that you should ask > your doctor, or maybe his nurse. But, have the office clarify anything you > don't understand. > > You said you speak French...where are you located? Different countries > have different laws regarding the release of medical information. Maybe > someone on the list can advise you with regards to the specifics for your > locale. > > Hope this helps! > > -- Chuck Knight > > P.S. From your email address, I'm guessing you're interested in physics. > Nice choice! > > > > > On Sun, Jan 25, 2009 at 11:42 AM, Woe <[email protected]>wrote: > >> >> Hi everyone :) >> >> Fist,I want to thank Ira a lot for his blog and this place.You changed >> completely the way I'm seeing the world.Quite litteraly in fact :) >> >> How can I say this...My glasses where "deathly wounded" about 2 weeks >> ago.They were berely wearable.While desperately searching online for >> prices I found your blog.And I don't think I'll ever buy glasses in >> store.Now I can even have beatiful glasses,fashionable...And change >> them when I want!Even sunglasses!Seriously,I spent one full day in >> some kind of dazzed exitement when the realisation hit me. >> >> And now time has come to make a move. >> >> Since I'm a french speaker I don't understand some formulation or >> words.And I forgot to ask my optometrist some questions.Not sure he >> would have answered anyway,I was clear about my intention to buy >> online.He refused to give me my pupillary distance,saying it was the >> optitian's job. >> >> I intend to start with 3 pairs of glasses.One bendable but simple,one >> more fashion,funky,and one pair of sunglasses.My intention is to buy >> from at least 2 stores,if possible 3. >> >> >> What stresses me is the type of lenses (1.57 , 1.61 , 1.67,etch) and >> the types of coating.I'm pretty sure I found those informations when I >> was looking at the reviews but I can't find it now than I need it. >> >> And I'm sorry to ramble so much.Fact is than I'm exited to try...And >> anxious too,a lot. >> >> I'll try my best to translate informations from my prescription >> >> | | | Spherical | Cylindrical >> | Axis | Prism | Vertex >> >> far vision E.R. -5.75 >> E.L. -5.75 >> +0.50 085 >> >> _____________________________________________________________________________ >> optical ecart (google's traduction) | A.V(??) | >> ____________________________|___________| >> ________________________________ >> | far near | | >> E.R E.R | E.R 6/6 | >> E.L E.L | E.L 6/6 | >> >> >> I've put only the informations where something was hand written.The >> prescription was not made on a computer but on a paper pad with the >> clinic's logo. >> >> >> So my questions are: >> >> 1: Witch type of lenses should I look for?(1.57 , 1.61 ...?)I don't >> want to pay for thinner (or the thinnest) lenses if the difference >> would be minimal.I'll do the shopping,I just miss a number target. >> >> 2: I saw somewhere tant the UV coating was at some place included in >> the price and at others already in the lenses.How do I know it's >> already there? >> >> 3:What's the AR coating? >> >> 4: Anti reflective coating...Is it the same thing as Antiglare?Looks >> like it to me,but I'm just not sure.If it's not,what is the difference? >> Would I need either anyway? >> >> 5:Tints...I think I saw somewhere that brown was best for >> protection.But a wich %?I'm searching an almost completely opaque >> ideally.I mean tha my eyes would be barely visible while I'm wearing >> it.Well,if it even exists.Never had one in my entire life^^Never >> looked for it either. >> >> 6:Not crazy about the brown anyway...Is it possible to obtain an >> equivalent protection and opacity with black or gray?Or mirror?(That >> one is from my boyfriend :D)At about wich % ? >> >> 7:As far as you know,is (I don't know how to say it...) progressive >> tint existing somewhere?I mean that the color is darker in the upper >> part of the lenses,going progressivelly clearer,see-trought.I searched >> for it on a few web sites,but if they have it,it's somewere I did't >> looked or I didn't understood what it meant. >> >> 8: What this A.V. in french could mean? >> >> I'm sorry if I ask questions allready answered a million times.And I'm >> sorry if the answers are somewhere not too far,I was unable to find >> it. >> >> Ant I'll share the knowledge gladly when the occasion present itself :) >> >> >> > > > > --~--~---------~--~----~------------~-------~--~----~ Check us out at the oft-updated http://www.glassyeyes.com! 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