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Medical Forum / General / Vision / September 2007Simple Prescription Question
If my prescription is: L: -1.25 ADD 2.50 R: -1.25 ADD 2.50 for a pair of SV reading glasses do I need +1.25 left and right ? TIA BW > for a pair of SV reading glasses do I need +1.25 left and right ? Yes, if you hold everything at 16 inches. Tall people and computer users often prefer a longer working distance. +1.00 is usually the weakest non-rx power available, and it calculates to 18", a little more generous. -MT Having listened to the comments from all, I guess the question is not as simple as I thought; it sounds like the gist of it is that a *lower* number +1.00 vs +1.25 gives you "stronger" reading glasses? ... "stronger" in the sense of being able to focus a given point size of text from a longer distance ... is that the deal? I'm a little perplexed with the apparent difficulty of "solving" my vision problems; the reality is that with *no glasses* on at all, my vision isn't all that bad ... I could (but don't) drive a car and can read maybe 80-90% of what's in front of me without any glasses ... but neither is great and I need to sharpen things but Mike, just to clarify, if I went down to the local "eye shop" and handed them my Rx and said I wanted a pair of SV reading glasses made, what would they likely do? would they use the "calculated" +1.25? (based on the -1.25 add 2.50, both eyes) I just had an eye exam and the numbers on the Rx are what they are ... are they even allowed to adjust it to +1.00 when an OD has said otherwise ? or is there more to the arithmetic? Perhaps you were advising on the assumption that I was just going down to the drug store to buy a pair of "readers" ?? which is perhaps what I should do? as always, thanks to all for the input BW >> for a pair of SV reading glasses do I need +1.25 left and right ? > [quoted text clipped - 5 lines] > > -MT > but Mike, just to clarify, if I went down to the local "eye shop" and > handed them my Rx and said I wanted a pair of SV reading glasses made, > what would they likely do? Licensed opticians will feel obligated to fill the rx as written. The way it's written, "SV reading glasses" will be made at +1.25 in each eye. Other than frame quality and some refinements, these would be indistinguishable from decent drugstore glasses. The distance rx of -1.25 means you see pretty well at (1/1.25=0.8m=) 30 inches with no glasses. This obvious benefit for reading is why nature made you nearsighted in the first place. You see better at 30 inches than someone who isn't nearsighted, because your eyes already have "built-in" reading glasses just as someone else would get from +1.25. So you only need +1.25 more to add up to +250, which will be clear at (1/2.50=0.4m=) 16". So whether you "need" reading glasses depends on how well you can cope with that 30-inch "natural" working distance, eg pushing your monitor back and holding your newspaper out. But if you can see your monitor without glasses now, you probably won't be able to see it from the same position with a pair of +1.25 glasses. That's OK if you get "half-eye" frames so you can look over them. The 16" assumption is traditional, but these days it only works for laptops, watchmakers and cross-stitiching. In your situation, working distance is everything. So for a 16" working distance, you need +125 more near power than nature gave you. For an 18" WD, you need +100. For 20", you need +0.75. Drugstores don't sell +0.75 but you can probably find them on the internet. For 30", you take your glasses off. > would they use the "calculated" +1.25? (based on the -1.25 add 2.50, both > eyes) I just had an eye exam and the numbers on the Rx are what they are > ... are they even allowed to adjust it to +1.00 when an OD has said > otherwise ? or is there more to the arithmetic? My own radical opinion is that educated and licensed opticians should be able to make these adjustments, since those without the need for distance correction are free to choose any power they like, from +1.00 to +3.25 at any wal-mart. But alas in most states, licensing boards will consider it an actionable offense for an optician to provide the same options to ametropes (people who need glasses for distance.) To me it's inconceivable that you have no right to ask for a +0.75 pair of SV. But if you want something custom, you may have to make your doctor understand what you want and get a written script. It's often difficult with younger doctors who haven't experienced the intricacies of presbyopia themselves. :) Your situation is simple enough you could write your own script and have some made on the Internet. > Perhaps you were advising on the assumption that I was just going down to > the drug store to buy a pair of "readers" ?? which is perhaps what I > should do? Well you certainly could. I recommended you think about +100 rather than +125, but it all depends on where you sit, where is your monitor, where do you read, and such. You can try the two in a drugstore and you'll find that one is clear about two inches closer than the other. You'll probably find +1.25 a little confining. DON'T base it on "print size." Pick some small print and move your head in and out to see what _distance_ works best. You could benefit from a drugstore pair that is ridiculously strong, like +200 or +250, to put away in the medicine cabinet or tacklebox, for untying knots and taking out splinters, things you hold 10 inches away. The biggest problem with SV glasses is they're SV - only clear at certain distances. You can approximate what you need with this pair or that, but you wind up with an assortment of powers and they disappear right before you need them. My favorite fix, in your situation, is a custom progressive with about -0.50 in the top and a +1.50 add, depending on how long your arms are. These are "indoor" glasses only, because they contain only the range of powers that are useful in a small room, cubicle, or workshop. -MT, OD > But alas in most states, licensing boards will consider it an > actionable offense for an optician to provide the same options to ametropes > (people who need glasses for distance.) To me it's inconceivable that you > have no right to ask for a +0.75 pair of SV. Mike, please explain what do you mean Lena ok ... now I think I get it; even knowing better, I haven't really been properly accounting for the difference in distance from reading material I typically experience ... do people really consistently read stuff at 16" ?? well, guess you have settle in on something or the other .. unless you want to keep a variety of glasses around what we need is auto-zoom lenses ... maybe one of these days nanotechnology will give us microprocessors embedded in lenses; AI will figure out the focal distance and trigger changes in refractive power something along the lines of "Transitions" changing the level of tint ... not in my lifetime I would not think ... we'll probably just fix the eye itself instead ... << > My own radical opinion is that educated and licensed opticians should be > able to make these adjustments, since those without the need for distance [quoted text clipped - 3 lines] > ametropes (people who need glasses for distance.) To me it's inconceivable > that you have no right to ask for a +0.75 pair of SV. I'd have to go along with this one, being of a libertarian bent ... just so long as the opticians are making these judgments in consultation with the patient thanks ... BW >> but Mike, just to clarify, if I went down to the local "eye shop" and >> handed them my Rx and said I wanted a pair of SV reading glasses made, [quoted text clipped - 75 lines] > > -MT, OD >ok ... now I think I get it; even knowing better, I haven't really been >properly accounting for the difference in distance from reading material I [quoted text clipped - 8 lines] >would not think ... we'll probably just fix the eye >itself instead ... These have already been invented. They are called progressives. From my experience they work. Although my Rx is different than yours, I recommend Zeiss PAL, unless the ODs around here think that it won't be proper for your prescription.  SignatureMsBrainy > >ok ... now I think I get it; even knowing better, I haven't really been > >properly accounting for the difference in distance from reading material I [quoted text clipped - 18 lines] > > Message posted viahttp://www.medkb.com Mrs Brainy, do not worry, His prescription assumes progressives. >>what we need is auto-zoom lenses ... maybe one of these days >>nanotechnology [quoted text clipped - 3 lines] >>would not think ... we'll probably just fix the eye >>itself instead ... > These have already been invented. They are called progressives. From my > experience they work. Although my Rx is different than yours, I recommend > Zeiss PAL, unless the ODs around here think that it won't be proper for > your > prescription. I don't think so, MsBrainy ... progressives don't adjust the refractive power of their segments dynamically based on the wearer's changing focal point ... what I'm talking about is (very) roughly akin to a camera's AutoFocus capabilities .. without the mechanical elements, which would be unwieldy at best ... not knowing enough about optics, nanotechnology, light valves, molecular array manipulation, optoelectronics, or even ordinary materials technology, how you would dynamically alter refractive power I haven't a clue ... it may all be sci-fi ... and it may not. Maybe Mike knows something about this and can fill us in on the state of play ... There is some incredible research going on in those areas. again, though, if I had to guess -- or invest in an optical tech company -- I think I'd bet on the one that was working on IOL implant technologies ... which I guess is already a reality in the multifocal domain, no? PALs will be around for a good many years ... anyway, I'm glad to know you've had a good outcome with your Zeiss PALs; I have no idea whether their lenses would be suitable for me or not ... but I don't think you're contradicting anything offered up by the good ODs contributing here ... only thing I know is that the Augen Trivex lenses I'm using now have to be adjusted/remade or replaced with another ... One note on the Augens : they were supposedly not AR coated but it appears to me they are ... there is observable reduction in glare from fluorescent lighting and they are a total bitch to keep clean ... BW > what I'm talking about is (very) roughly akin to a camera's >AutoFocus capabilities .. without the mechanical elements, which would be >unwieldy at best ... not knowing enough about optics, nanotechnology, light >valves, molecular array manipulation, optoelectronics, or even ordinary >materials technology, how you would dynamically alter refractive power I >haven't a clue ... it may all be sci-fi ... and it may not. Not. http://www.pnas.org/cgi/content/full/103/16/6100 Robert Martellaro ~~~~~~~~~~~~~~~~~~ Optician/Owner Roberts Optical Wauwatosa Wi. ~~~~~~~~~~~~~~~~~~ "Science is a way of trying not to fool yourself." - Richard Feynman >> what I'm talking about is (very) roughly akin to a camera's >>AutoFocus capabilities .. without the mechanical elements, which would be [quoted text clipped - 5 lines] > > Not. > http://www.pnas.org/cgi/content/full/103/16/6100 > > Robert Martellaro how about that; closer at hand than I thought ... thanks for posting it, Robert ... > Having listened to the comments from all, I guess the question is not as > simple as I thought; it sounds like the gist of it is that a *lower* number > +1.00 vs +1.25 gives you "stronger" reading glasses? ... "stronger" in the > sense of being able to focus a given point size of text from a longer > distance ... is that the deal? No, stronger and weaker are poor terms. You want the "right" strength for the distance you want to use. > Perhaps you were advising on the assumption that I was just going down to > the drug store to buy a pair of "readers" ?? which is perhaps what I should > do? That's what I would do. At least you can then easily tell what strength is best for your needs. > >> for a pair of SV reading glasses do I need +1.25 left and right ? > > [quoted text clipped - 5 lines] > > > > -MT Dear Barrie, Subject: Depth-of-Focus. As Mike said, your "distant" focus is at 30 inches or -1.25 diopters. The amount of "change" from 30 inches to 20 inches is 0.75 diopters. Dead-band, or depth-of-field is about 1 diopter. Thus your vision at 20 inches should be very good, simply on that basis -- even if you had no accommodation at all. If you have 2 diopters of accommodation, then that is even better. As Mike stated, the "readers" of +1.25 diopters would accomplish this task for you -- if you find them more comfortable. Best, Otis > Having listened to the comments from all, I guess the question is not as > simple as I thought; it sounds like the gist of it is that a *lower* number [quoted text clipped - 34 lines] > > - Show quoted text - thanks, Otis and Robert ... I won't counter-comment just for the sake of counter-commenting .. your input is helpful .. BW > Dear Barrie, > [quoted text clipped - 72 lines] >> >> - Show quoted text - Dear Barrie, Subject: An alternative. What you decided to do depends on the range of your accommodation. With your refractive STATE of -1.25 diotpers, you probably have good vision at "near". You man in fact find you can use your eyes at 20 inches (-2 diopters) better with no lens on your face. Just take them off and check. Best, Otis > If my prescription is: > [quoted text clipped - 6 lines] > > BW Sorry. Rishi Giovanni Gatti (Zetsu), Lena102938, and Otis Brown are trolls who haunt s.m.v. Rishi has published, and is trying to sell worthless books. Otis is pathologically dishonest and actually hurts people. Following his advice can induce double vision in those not working closely with an eye doctor. Lena102938 uses anti-eye doctor rhetoric as a substitute for ANY actual information. It seems she now has to wear glasses and has developed a pathological (and ILLOGICAL) resentment toward the industry that "foisted these glasses upon her." You'd do well to ignore them and wait for responses from the caring, compassionate eye doctors who DO also participate in this site. Dear Barrie, Subject: Basic math and optics. In fact your eyes have a focal-length (or forcal point) of about 31 inches. (Maximum distance for clear focus). With no minus lens you could wear a +0.75 diopter lens and see cleary ar 20 inches or closer -- if you like the idea of the plus -- and don't like a bifocal. Otis > If my prescription is: > [quoted text clipped - 6 lines] > > BW Sorry. Rishi Giovanni Gatti (Zetsu), Lena102938, and Otis Brown are trolls who haunt s.m.v. Rishi has published, and is trying to sell worthless books. Otis is pathologically dishonest and actually hurts people. Following his advice can induce double vision in those not working closely with an eye doctor. Lena102938 uses anti-eye doctor rhetoric as a substitute for ANY actual information. It seems she now has to wear glasses and has developed a pathological (and ILLOGICAL) resentment toward the industry that "foisted these glasses upon her." You'd do well to ignore them and wait for responses from the caring, compassionate eye doctors who DO also participate in this site. |
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