 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Medical Forum / General / Vision / March 20062 pair vs. progressives
First, a question about my prescription. It is distance: -2.25 left and right, Reading +2.00 left and right. Is this prescription for a single vision lens with curvature that varies or is it for a bifocal? Second, I've tried progressives before and had difficulty with them - couldn't stand moving my head so much. I'm at a computer for many hours each day. Would a pair of single vision glasses for distance and a lined bifocal for reading/computer work? Could a bifocal be made for reading and intermediate ranges and would that be effective for working at my PC/desk? Thanks. Ever thought of talking to your optometrist, it is his job you know. If he won't discuss it, you are at the wrong place and look for another. For what it's worth, this script won't work on a computer, bifocals will give you a sore neck and you will whinge here about how you hate bifocals and how horrible your glasses are. You can try some of the new generation MF's like Ipseo, SolaOne HD, or the like, get an intermediate script made or whatever else you like, but it would help if you got a good optom to test you and give you your options with you in presence. dr grant > Ever thought of talking to your optometrist, it is his > job you know. [quoted text clipped - 12 lines] > good optom to test you and give you your options with you > in presence. I guess this is on topic for this thread... How does a progressive "progress"? I'm assuming there is some sort of seg height where the lens power starts to diverge from the distance Rx and starts to move towards the add. I assume it hits the add power somewhere before the bottom of the lens (assuming the lens is large enough?). ...that brings up a second part of the question. First, not considering lens size, is the rate of change in power constant from the distance Rx to the Add? Or are there transition zones and segment areas? Is this variable dependent on lens height? Can all the above be specified? Could I design my progressive lens to have 3 sort of segment areas where the rate of change in power over the segment area is small relative to the transition zones. This is what I would expect a "no line tri/bifocal" to be. Naturally I have something in mind... A "progressive" trifocal with maybe 1/2 the lens distance, 1/3 computer and 1/6 near. -Quick > First, not considering lens size, is the rate of change > in power constant from the distance Rx to the Add? > Or are there transition zones and segment areas? It's pretty uniform, a smooth gradient. > Is this variable dependent on lens height? The rate must be influenced by the "add" power. Assuming all lenses have a 16-mm "corridor" then a +200 add must increase twice as fast as a +1.00 add. > Can all the above be specified? Could I design my > progressive lens to have 3 sort of segment areas > where the rate of change in power over the segment > area is small relative to the transition zones. No. Well, not without a *big* investment and a cooperative manufacturer willing to loan you his engineers and tool-makers. > This is what I would expect a "no line tri/bifocal" to > be. Naturally I have something in mind... A "progressive" > trifocal with maybe 1/2 the lens distance, 1/3 computer > and 1/6 near. A "blended trifocal" would have the lines polished out into linear smears, and those are rare these days. All other "no-lines" are "progressive addition lenses" (PALs), which pretty much have uniform power gradients. Some PAL brands have "shorter corridors" meaning a faster rate of increase toward the bottom, so that they fit in smaller frames. Others emphasize corridor width, pushing peripheral distortion further to the side and perhaps up into the distance portion, in order to provide a wider field of view through the intermediate or near. Some optimize the intermediate, moving it up into the line of sight and reserving clear distance vision to a small portion at the top of the lens. The variations are numerous, and then the prescriptions can be manipulated at the optical shop if it's decided to compromise one distance in favor of another. -MT Sorry, Mike, but I will qualify some of what you have said, well, semantic little bits anyway. > > First, not considering lens size, is the rate of change > > in power constant from the distance Rx to the Add? > > Or are there transition zones and segment areas? > > It's pretty uniform, a smooth gradient. Most lens designs these days have a more rapid shift in the first (top) half. A Varilux Comfort lens (older design, but I remember the figures as it was the first of its kind) reached 85% of the near add at 50% of the corridor. The purpose is to get quicker to the reading zone without the head tilt. > > Is this variable dependent on lens height? > > The rate must be influenced by the "add" power. Assuming all lenses have a > 16-mm "corridor" then a +200 add must increase twice as fast as a +1.00 add. Yes, but remember Quick, that different designs have different corridor lengths and different shift characteristics which are dependant on the manufacturer and what they want to achieve. > > Can all the above be specified? Could I design my > > progressive lens to have 3 sort of segment areas [quoted text clipped - 3 lines] > No. Well, not without a *big* investment and a cooperative manufacturer > willing to loan you his engineers and tool-makers. This is the good thing about having so many designs on the market. You effectively do this by selecting a design. Some perform better for intermediate, some for distance and others near. > > This is what I would expect a "no line tri/bifocal" to > > be. Naturally I have something in mind... A "progressive" [quoted text clipped - 16 lines] > > -MT Well stated Mike. The thing to remember Quick is that we are getting much better at MF design and the flexibility of newer designs is so much better than before. What you want is probably going to be easily achieved with the latest generation of lenses such as Ipseo, Hoya ID, Sola HD etc. By incorporating the multifocal on the back surface, you get less peripheral swing, wider reading and intermediate zones and better distance clarity. dr grant > Sorry, Mike, but I will qualify some of what you have > said, well, semantic little bits anyway. [quoted text clipped - 70 lines] > surface, you get less peripheral swing, wider reading and > intermediate zones and better distance clarity. Drat... better call my doc and put a hold on the order or talk to him about it. (and I left my script at home...). Now that I'm finally very happily fitted with my translating trifocal RGPs I figured I might as well get a pair of progressives as a backup. I hadn't planned to and figured I could make do with my drug store readers in a pinch but at the last moment figured what the hey, might as well. Being the ultimate consumer and sort of an impulse buyer it only took about 15 minutes to gravitate towards the Lindberg Air Titanium frames, grey transition progressive lenses, with Zeiss(sp?) gold (I understand that's better for night issues where the blue is better for daytime issues) AR. Doc recommended polycarb for my weak Rx and didn't know if the transitions came in trivex. Apparently they don't. He said plain CR39? plastic would be fine as well but he didn't like it because of no UV protection. I thought *any* plastic provided UV protection? I think my script is something like 0.75 with a 2.25 add and very slight astigmatism in the left eye. He did show me the trivex display where they have a special light that shows the trivex lens clear next to the polycarb that looks like a rainbow resulting from oil on water but said he didn't think it would make a difference with my script. I'm pretty discerning (perfectionist/anal) about everything and figured "trivex for me!). besides I felt like throwing as much business his way as possible sort of as thanks for the tremendous effort he put in working with me on the trifocals. thoughts? -Quick >Ever thought of talking to your optometrist, it is his job you know. > [quoted text clipped - 3 lines] >For what it's worth, this script won't work on a computer, bifocals >will give you a sore neck Would you please explain WHY you'd get a sore neck? "Executive"-style BI-focals are actually a *good* solution to his problem, perhaps the *best* solution. Like, suppose he's got a 20" screen, and wants to point his nose at its center and then be able to flip his eyeballs up, down, left, right, and see everything super-sharp? Fron a distance of maybe 24 inches. Just how can he (or you) do that via progressives. with their hourglass-shaped in-focus area? Just be careful to make sure both left and right eye, with the glasses on, come to exactly the SAME distance for perfect focus. If your accomodation has gone to about ZERO, as mine has, you'll have play with the balance between the two eyes, up to the most precise (one-quarter diopter, I think it is). Makes all the difference, having the left and right eye come to focus at EXACTLY the same distance. > and you will whinge here about how you hate >bifocals and how horrible your glasses are. > >You can try some of the new generation MF's like Ipseo, SolaOne HD, or >the like, One thing for sure about pregressives: they cost a LOT more than bifocals, with the extra fitting, etc. Might that be *one* of the (several) reasons for optometry-shops recommending them? ?get an intermediate script made or whatever else you like, >but it would help if you got a good optom to test you and give you your >options with you in presence. > >dr grant David > First, a question about my prescription. It is distance: -2.25 left and > right, Reading +2.00 left and right. Is this prescription for a single [quoted text clipped - 5 lines] > and intermediate ranges and would that be effective for working at my > PC/desk? Thanks. Your Rx is for bifocals or progressives. It can also be used for SV lenses that are used at a distance (such as driving) and the add power will be ignored. Distance lenses are optimized for 20 feet, and add power (reading) is optimized for about 13 inches. Measure the distance from your glasses to your computer monitor. If it is more than about 17 inches, you might want to get a special pair of bifocals or SV lenses that are optimized for computer work at your working distance (and one other distance if you want bificals or progressives). Ask your OD to give you an Rx for your computer monitor distance. If you sit around a foot and a half from your computer monitor, you dont need glasses for that. If you sit a little further, you can just move up so your 18" away from the monitor. If you sit far, what you can do is get "computer glasses" a pair of reduced power glasses just for the computer. This is what I did, so much easier than bifocals or progressives for the computer! If you cant handle progressive or bifocal, theres no need really. You are mildly myopic and can simply peak under your glasses or remove them for reading Shut up idiot. Why would he be asking about lenses if he wanted four pairs? Don't wear glasses and all will be well, as long as you don't want to sewe anything. dr grant
|
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.