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Medical Forum / General / Vision / December 2006Special vision test for computer glasses?
I'm going to be getting glasses to use with a new laptop computer. I assumed that the correct add would just be a function of the working distance form the eye to the computer's display. But then I saw claims that because of all the little dots, the eye focuses differently on a computer screen than it would on printed text at the same distance. In fact, there's a product designed specifically for determining the correct refraction for computer use. It uses a simulated computer display to do the eye test. The implication is that you would get a different result than using an eye chart at the same distance. Here's the link: http://www.prio.com And here's a picture of the testing device: http://www.prio.com/consumers/solution.cfm Frankly, this looks like pure BS to me. But I've been fooled before. What do the experts think? > http://www.prio.com/consumers/solution.cfm > > Frankly, this looks like pure BS to me. But I've been > fooled before. What do the experts think? You are right on. It IS pure BS. I've looked at their research and THEIR OWN DATA proves they are screwed up; they just don't know how (or refuse to) understand it. w.stacy, o.d. > I'm going to be getting glasses to use with a new laptop > computer. I assumed that the correct add would just be a [quoted text clipped - 18 lines] > Frankly, this looks like pure BS to me. But I've been > fooled before. What do the experts think? There are two issues: 1. Is there a difference in the Rx with their method of using a computer screen instead of a chart (both at computer distance)? 2. What is the difference in the lens they sell, compared to other computer lenses? I don't know anyone who always views the computer screen at the same exact distance each time, or views the entire screen at the exact same distance. It is hard to believe that their measurement technique with an actual computer screen will come up with a different Rx compared to a regular chart held at computer distance. If the distance alone was a factor, then it could easily be corrected by moving further or closer to the screen by a few inches. Is there something about the lens that is an improvement over other computer lenses. I doubt it, except that most computer lenses are made from a normal Rx with distance and reading power without a specific measurement of computer distance, and a 'standard" adjustment (instead of a custom measurement) is made from the reading power to the computer power to achieve the optimal computer power in the upper portion of the lens. For example, I believe that Zeiss Gradal RD always assumes that the right power for computer distance is .50 subtracted from the reading power. So their could be some advantage for taking a custom Rx to the computer distance, but I don't think using an actual computer screen helps, and a good OD could come up with the exact Rx to make a pair of customized computer glasses with any of the name brand lenses like Zeiss Gradal RD. > Is there something about the lens that is an improvement over other computer > lenses. I doubt it, except that most computer lenses are made from a normal [quoted text clipped - 4 lines] > believe that Zeiss Gradal RD always assumes that the right power for > computer distance is .50 subtracted from the reading power. Confused here -- "optimal computer power in the upper portion of the lens" makes no sense to me, especially with a lens like the Gradal RD, which I understand is designed to allow a presbyope the ability view with clarity far-intermediate targets at 2 or 3 meters through the upper portion of the lens. Near-intermediate viewing (computer screens) would be through the middle area of the lens...correct? http://www.zeiss.de/c125679b00315836/Contents-Frame/3b6d61f53c9edbfdc125679e004c6aa9 bg > Confused here -- "optimal computer power in the upper portion of the > lens" makes no sense to me, especially with a lens like the Gradal RD, [quoted text clipped - 6 lines] > > bg Yes, that is correct. The Zeiss Gradal RD has a wider intermediate area that is used for computer distance. As you mentioned, and unlike a normal progressive, the upper portion does not have the correct distance power (usually 2-3 meters max), so you cannot use them for driving. Also, some opticians use regular progressives to make custom computer lenses with the upper portion optimized for computer distance, and the lower portion for reading, and one cannot even see clearly at 2-3 meters in the upper portion of the lens. In theory this gives a larger area for computer distance, but is less flexible in seeing beyond that (like being able to see someone sitting across the desk from you). If you go the custom route, you can do whatever you wish, but as you say the Zeiss Gradal RD does allow one to see up to 2-3 meters if you give them a normal progressive Rx and they make the standard adjustment. > > Confused here -- "optimal computer power in the upper portion of the > > lens" makes no sense to me, especially with a lens like the Gradal RD, [quoted text clipped - 22 lines] > Zeiss Gradal RD does allow one to see up to 2-3 meters if you give them a > normal progressive Rx and they make the standard adjustment. Am I correct in my understanding that the Gradal RD always has 0.50 in the upper portion of the lens and that the lower areas simply add more *diopter* as needed to provide the viewer with clarity at closer ranges? -bg > > Am I correct in my understanding that the Gradal RD always has 0.50 in > the upper portion of the lens and that the lower areas simply add more > *diopter* as needed to provide the viewer with clarity at closer > ranges? roughly correct. I think they also have rather wider intermediate and near zones than do conventional progressives. w.stacy, o.d. actually, I should add that the .5 in the distance is in addition to any distance Rx that has been prescribed. w.stacy, o.d. > actually, I should add that the .5 in the distance is in addition to any > distance Rx that has been prescribed. > > w.stacy, o.d. Interesting that some computer glasses are chosen for viewing the screen through top portion of the lens. My purposes for an occupational progressive are more conventional, however: I need to see clearly and find objects at room distances -- up to 3 meters, no more, but also need to read up-close and view computer screens at more than arm's length. I do require distance correction also, but that's being accomplished with contacts (+1.25) and I intend to keep wearing the contacts all the time. Instead of continuing to rely upon an assortment of OTC readers for near and intermediate distances, I'm thinking the Gradal RD might provide an optimal solution for my sometimes demanding "room distance" requirements -- provided I can find a pair. -bg > Am I correct in my understanding that the Gradal RD always has 0.50 in > the upper portion of the lens and that the lower areas simply add more > *diopter* as needed to provide the viewer with clarity at closer > ranges? Yes.. if your distance prescription is +1.00 and your near "add" is +2.00, RD lenses are modified to +1.50 for distance with a +1.50 add (still totaling +3.00 at near.) There are many benefits and one of them is that +1.50-add progressives will always be "wider" than +2.00 progressives of the same design. I wear generic progressives modified this way, and the blur driving is tolerable for short trips in daylight. -MT > > Am I correct in my understanding that the Gradal RD always has 0.50 in > > the upper portion of the lens and that the lower areas simply add more [quoted text clipped - 12 lines] > > -MT Ok, I see. The Gradal RD, for the upper area of the lens, always adds +0.50 to whatever the user's distance prescription is and that makes the "distance" area of the lens a bit blurry for actual far-distance viewing, but possibly tolerable for far-distance viewing over short period of time. Question: I wear +1.25 contacts for distance viewing and continue to do so. On top of the contacts, my prescription calls for a near "add" of +2.50 for fine reading and +1.25 for reading a computer screen at arm's length. If this prescription is applied to an order for a pair of Gradal RD, then what will these lenses actually provide? (I'm thinking it would be an actual +0.50 in the upper part of the lens, but can't figure what the lower up-close viewing area of the lens would provide with the Gradal RD design.) -bg > Question: I wear +1.25 contacts for distance viewing and continue to do > so. On top of the contacts, my prescription calls for a near "add" of > +2.50 for fine reading and +1.25 for reading a computer screen at arm's > length. If this prescription is applied to an order for a pair of > Gradal RD, then what will these lenses actually provide? With contacts, your prescription presumably reads "0.00" for far away, so the +2.50 "add" represents the total reading power for near vision. To customize your own "RD" lenses, you could put any amount you want in the top, as long as you "remove" it from the add so that the total remains +2.50 in the bottom. > (I'm thinking > it would be an actual +0.50 in the upper part of the lens, but can't > figure what the lower up-close viewing area of the lens would provide > with the Gradal RD design.) -bg +0.50 distance with +2.00 more "added" toward the bottom, total +2.50. -MT > > Question: I wear +1.25 contacts for distance viewing and continue to do > > so. On top of the contacts, my prescription calls for a near "add" of [quoted text clipped - 17 lines] > > -MT Actually my contacts prescription is +1.25 for far-away vision. When the +2.50 "add" specified in the prescription for supplemental readers is included (when I'm wearing my contacts) the total reading power for near vision is +3.75. So...what I'm now understanding now is that Gradal RD lenses (ordered for use with the contact) would have +0.50 in the upper area and would have +2.00 added toward the bottom for a total of +2.50. The order to Zeiss then would specify 0.00 as the far-distance viewing parameter and +2.50 for up close... correct? Worn over my +1.25 contacts, the total up-close reading power would then be +3.75, the middle intermediate area would provide around +1.75, and the upper "distance" area would provide a total of +1.75. (A little much for my far-distance needs, but I could tolerate it for a while if I wanted to!) Will consider customizing an "RD" lens. But wonder if the Zeiss product would work better. -bg > > Question: I wear +1.25 contacts for distance viewing and continue to do > > so. On top of the contacts, my prescription calls for a near "add" of [quoted text clipped - 17 lines] > > -MT Oops... I think I read too much into your reply... anyway, yeah, my supplemental progressives (RD or whatever) precription assumes "0.00" for far away and reads +1.25 for computer screen (intermediate) and +2.50 for fine reading (up-close). -bg "Mark A" <nobody@nowhere.com> wrote in message news:... > Yes, that is correct. The Zeiss Gradal RD has a wider intermediate area > that is used for computer distance. As you mentioned, and unlike a normal [quoted text clipped - 11 lines] > the Zeiss Gradal RD does allow one to see up to 2-3 meters if you give > them a normal progressive Rx and they make the standard adjustment. BTW, Zeiss has new computer lens called Zeiss Business which is only suitable for vision up to 4 feet (1.3 meters). It comes in two power "differentials", depending on you add power is in your normal progressive Rx. http://www.zeiss.com/41256820002524a3/Contents-Frame/ac94e29ba0c4621985256e600070bda5 |
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