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Medical Forum / General / Vision / January 2006Question to ask before going to my eye exam
Hi all, I'm Jamie, a 28 yr old guy. I'm due for a new eye exam sometime in the next month or so and had a question before going in for the exam. Current rx is: -6.00 -3.00 005 -6.50 -3.75 167 Anyway, here is the question. Sometimes later in the day, if I have been doing a lot of reading and/or been on the computer, I start to notice some eyestrain. Got a pair of those stick-on Optx lenses and have placed them on another pair with the same prescription. When I begin to feel that eyestrain kicking on, I will occasionally put on the pair with the stick-on add and they do help. So, my question is this is something fairly normal today or I should inquire about possibly getting bifocals. Most of the day I don't tend to have a problem, it's only on days that I spend a lot of time reading or on the computer that it begins to be a problem in the evening. BTW, I'm a graduate student working on their Ph.D if it helps Thanks a lot-Jamie > Got a pair of those stick-on Optx lenses and have placed them on > another pair with the same prescription. When I begin to feel that > eyestrain kicking on, I will occasionally put on the pair with the > stick-on add and they do help. > So, my question is this is something fairly normal today or I should > inquire about possibly getting bifocals. You might consider getting a pair of glasses for near work. That is what I would do, in your situation. Adding +2.0D to the spherical component of your prescription gives you glasses that should be good for a computer screen at 1/2.0 meters. That is kind of standard for old people's reading glasses, but since you have good accomodation ability still, you might be comfortable with less of an "add". You can ask your eye guy what might be good for you, but it is cheap to try, since mail-order single-vision eyeglasses are offered cheap as $19. (I am very pleased with a fancy rimless pair I got from Zenni in two weeks for $30.90, though a bit of very careful, high-tech bending was needed to get the lenses flat to the eyes.) (Why do some eyeglass makers think that eyeglasses should be stream- lined?) Using reading glasses might possibly slow or prevent myopic progression. -- Dicky -------------------------------------------------------------------------------- http://www.zennioptical.com/index.html http://www.specs4less.com/ http://www.39dollarglasses.com/cgi-bin/store/index.html (& many more) I am 23 and I read without glasses. Not possible for you due to high astigmastim. You however can get progressive glasses. Not easily noticable unlike bifocals. I would get progressives myself if I had astigmastim. I do have a seperate pair of glasses I use for the computer, my eyes feel much better now :) >I am 23 and I read without glasses. Not possible for you due to high >astigmastim. I have nearly as much astigmatism as the OP and read just fine without glasses - as long as the book is less than a foot from my face. You however can get progressive glasses. Not easily >noticable unlike bifocals. No-line bifocals have been on the market for years. I know a lot of people who don't like them as much as they like "traditional" bifocals. I would get progressives myself if I had >astigmastim. Astigmatism has nothing to do with any potential need for an add to accomodate near work. +++++++++++++ Reply to the list as I do not publish an email address to USENET. This practice has cut my spam by more than 95%. Of course, I did have to abandon a perfectly good email account... Yeah, unfortunately when I try to read without my glasses. I have to hold it very close and then will eventually get a headache due to the astigmatism. The progressives do sound like a possible option because that is one worry I have about bifocals. About it being too noticable, which at 28 I am not sure I want everyone to know > I am 23 and I read without glasses. Ace, here is a joke you might like: There was this very nearsighted lady who wanted to prove that she could see quite well. So she stuck a needle in the old oak tree way down by the road, near the mailbox. In the evening, when everyone was gathered 'round out on the front porch, she exclaimed: "Say, is that a needle way down there in the oak tree?". Of course the folks all said: "We don't see any needle". So she said "Wait, I'll go get it", and she took off lickety-split down the front yard. But she tripped over a cow. Ace, tell that one to your Dad. I'll bet he will like it. And it might help make your case. -- Dicky > You might consider getting a pair of glasses for near work. That is what > I would do, in your situation. [quoted text clipped - 4 lines] > good accomodation ability still, you might be comfortable with less of > an "add". An add of +2.00 might be a bit strong (as you said). For a 28 yr old +0.75 would be fine. Dom > An add of +2.00 might be a bit strong (as {Dicky said). For a 28 yr. old > +0.75 would be fine. Well, I was saying what I, if I were in his boots, would do, based on my thoughts over 50 more years. My thinking is to take stress off the eyes by fooling them into thinking the computer screen (or book, or whatever) is at a distance of virtual infinity (the horizon). I would also consider base-out prisms so that the eyes converge there (at infinity) also. As my accommodation range shortened, I personally was quite happy with a single vision pair that put stuff on the bench, and most stuff in the room, in my range, which, in practice, meant delaying my visit to the eye guy as my myopia progressed (to meet my needs?!). Up to age ~60, ~1D of under- correction was quite nice as long as I did not need to do any night driving. (It was also my experience, as I had a complex prescription including base-up and base down- prisms, that my eyeglasses could be very expensive, esp. if bifocal, and whether or not bifocal, my eyes had much trouble in navigating the surfaces of the chunks of glass, even if the eyeglasses were competently made, which they were not always.) (It should be pointed out to the otis naysayers, that I am not exactly invoking *The Plus*, but, in this case, the less-minus, and, more precisely less-minus in accordance with a specific rationale, with optional convergence correction as well.) I also mentioned *The Cheapest* as a possibility, as it frequently occurs that *The Cheapest* turns out to be *The Best*. And, considering the responses already posted, I'd also suppose the most practical. -- Dicky P.S. The El Cheapo prescription reading glasses I mentioned seem to be anti- reflection coated -- reflections are very faint, and light blue. The lenses shed water beautifully when cleaned. Let the Crystal Alligator merchants chew on that. >(It should be pointed out to the otis naysayers, that I am not exactly >invoking *The Plus*, but, in this case, the less-minus, and, more precisely >less-minus in accordance with a specific rationale, with optional convergence >correction as well.) Good job ;-)  SignatureLive simply so that others may simply live > Hi all, > [quoted text clipped - 27 lines] > > Thanks a lot-Jamie Yeah a form of bifocals might help you. Not literally bifocals but maybe consider a lens called the Sola Access: http://www.compukiss.com/vc/products/accesslens/accesslens.html http://www.sola.com/professionals/access.shtml Of course this is assuming your current glasses are still the correct strength for your distance vision. Don't get a 'bifocal' as these usually don't work very well with computers. The other option is a multifocal (=progressive) lens but for heavy computer/reading days you might be better with the Access. Dom Dom, Thanks for the suggestion about those lenses. I hadn't heard of them before, but they do look interesting. Thanks for the suggestions regarding bifocals/progressives >Current rx is: >-6.00 -3.00 005 [quoted text clipped - 3 lines] >been doing a lot of reading and/or been on the computer, I start to >notice some eyestrain. Jamie, In addition to a comprehensive eye exam I would also have an experienced optician take a very close look at optical center position on each lens. If new lenses are required I would recommend an atoric surface design like Sola's Vizio. Hope this helps Robert Martellaro ~~~~~~~~~~~~~~~~~~ Optician/Owner Roberts Optical robopt@execpc.com ~~~~~~~~~~~~~~~~~~ "An expert is a person who has made all the mistakes that can be made in a very narrow field." - Niels Bohr for "Jamie" whose Current rx is: -6.00 -3.00 005 -6.50 -3.75 167 > In addition to a comprehensive eye exam I would also have an experienced > optician take a very close look at optical center position on each lens. I guess that would be a second opinion with respect to that of the optician who made the eyeglasses, as to whether the lenses line up correctly with Jamie's eyes. > If new lenses are required I would recommend an atoric surface design like > Sola's Vizio. I did not know about *atoric* but read this: http://216.25.63.52/learn/Principles_of_Atoric_Lens_Design.pdf Since Jamie's glasses are strong with much cylindrical component, atoric lenses may make sense. In making a decision, figure 7. in the PDF document my be useful, in connection with economic considerations. (Professional advice is sometimes slanted away from economical solutions.) Jamie, let us know what you come up with, and how well it solves your problem. -- Dicky (X-myope) >for "Jamie" whose Current rx is: >-6.00 -3.00 005 [quoted text clipped - 5 lines] >I guess that would be a second opinion with respect to that of the optician who >made the eyeglasses, as to whether the lenses line up correctly with Jamie's eyes. Most of the eyeglasses that I've seen (old glasses presented to me by new clients) are poorly designed, fitted, and manufactured, resulting in varying degrees of asthenia. >> If new lenses are required I would recommend an atoric surface design like >> Sola's Vizio. > >I did not know about *atoric* but read this: >http://216.25.63.52/learn/Principles_of_Atoric_Lens_Design.pdf Yup, Darryl's the man. Check out Optiboard.com and Opticampus.com. >Since Jamie's glasses are strong with much cylindrical component, atoric lenses >may make sense. A 3.75DC lens using standard curves will offer very little clear off-axis vision near the central gaze, and poor peripheral vision. An atoric design will more than double the area of clear vision and improve the peripheral substantially. I think that's sensible. Regards, Robert Martellaro ~~~~~~~~~~~~~~~~~~ Optician/Owner Roberts Optical robopt@execpc.com ~~~~~~~~~~~~~~~~~~ "An expert is a person who has made all the mistakes that can be made in a very narrow field." - Niels Bohr > A 3.75DC lens using standard curves will offer very little clear off-axis vision > near the central gaze, and poor peripheral vision. An atoric design will more > than double the area of clear vision and improve the peripheral substantially. I > think that's sensible. I rarely disagree with you but here I must, having worn 3 cyls for years, and having practiced optometry for over 30. I don't recall any problems ever with off axis vision with my own glasses, and don't remember any high cyl patients complain of "very little clear off-axis vision", and I've fit some pretty high cyls over the years, many above 4 D.C. and a few even in the double digits. The plots of clear vision through ordinary CC lenses and atorics does show a larger area of "perfect" correction with the atorics, but only marginally larger and probably only marginally better (the diagrams don't even quantify the amounts of error for either type of lens; why don't they do it just like the plots for progressive lenses?). I mean if you get a .25 better cyl correction 15 mm off axis, is it worth losing sleep (or money) over? I don't think so, since you rarely direct your line of sight that far off axis, and your peripheral vision doesn't care a whit if the cyl is off .25 or more. The upshot of this is that I've not yet prescribed or filled an Rx for an atoric. Not one. I'd be interested to see utilization rates from you or other practitioners... w.stacy, o.d. >> A 3.75DC lens using standard curves will offer very little clear off-axis vision >> near the central gaze, and poor peripheral vision. An atoric design will more [quoted text clipped - 24 lines] > >w.stacy, o.d. Most of my clients wear multifocals, mostly PALs. Off-axis performance at 15 degrees is a concern, and is a typical if not conservative reading depth considering that very few PALs achieve their full add power at this distance. A +5.00DS crown glass lens, with the gaze 18 degrees off-axis, an object distance of 40cm, and wearers vertex of 12mm will have an oblique astigmatism of .08 and a mean power error of -.28, when using a front curve of +10.00, or essentially "best form". Use the same curve on a +9.00DS lens and the oblique astigmatism increases to *1.23* and +.82 mean power error. Change to a prolate ellipsoid aspheric surface and the aberrations reduce to .06 and -.22 respectively. Unfortunately the aphericity increases the aberrations to 1.09 and -.91 on the +5.00DS lens. However, if both surfaces are aspheric and optimized on all meridians the aberrations remain low around the clock on a +9.00 -4.00 X xxx lens. Even non-astigmatic corrections can benefit from this technology. For instance, a -4.75DS under the above conditions using a +4.00BC has .23D of oblique astigmatism. Changing to a +2.00BC improves slightly to .19D. If a +3.00BC was available the astigmatism would be .06. A bi-aspheric lens would achieve the same result using +2.00BC, resulting in better off-axis performance *and* on minus powers an appreciable thinner and lighter lens. Although not all direct surfaced or free-form lenses are atoric, other benefits include wider near and intermediate zones (when the progressivity is on the back surface) along with optimized insets by power and reading distance. I would recommend these lenses for those who perform above average near tasks, higher power Rxs, and especially moderate to high astigmatism. Regards, Robert Martellaro ~~~~~~~~~~~~~~~~~~ Optician/Owner Roberts Optical robopt@execpc.com ~~~~~~~~~~~~~~~~~~ "An expert is a person who has made all the mistakes that can be made in a very narrow field." - Niels Bohr Change degrees to mm in the above two paragraphs. Reading angle would be about 40 degrees. ok that answered one of my questions in the prev. post, meaning way off axis, at least to me... also, I'll say I don't care for very flat lenses that are being pushed. They look like mirrors even with AR coatings... w.stacy, o.d. >Change degrees to mm in the above two paragraphs. Reading angle would be about >40 degrees. > >Most of my clients wear multifocals, mostly PALs. Off-axis performance at 15 >degrees is a concern, and is a typical if not conservative reading depth >considering that very few PALs achieve their full add power at this distance. > > Right, although most or all PALs are not atoric, are they? I mean you'd have to have some super finishing equipment to generate an atoric inside curve, and I haven't heard PAL mfrs claiming atoric capabilities, or have I just not been paying attention???? No argument that PALs are a challenge esp in the moderate to high plus, which is where I tend to avoid them. Maybe the Rodenstock Multigressiv? >A +5.00DS crown glass lens, with the gaze 18 degrees off-axis, an object >distance of 40cm, and wearers vertex of 12mm will have an oblique astigmatism of [quoted text clipped - 3 lines] >ellipsoid aspheric surface and the aberrations reduce to .06 and -.22 >respectively. Right, the reason we like aspheric lenticulars for aphakic powers, which +9 is really into. >Unfortunately the aphericity increases the aberrations to 1.09 >and -.91 on the +5.00DS lens. However, if both surfaces are aspheric and >optimized on all meridians the aberrations remain low around the clock on a >+9.00 -4.00 X xxx lens. > So for your +9-4x? lens, it sounds like non aspheric might be better than ordinary aspheric? Theoretically, atorics would improve dramatically over aspheric but only marginally over best form? >Even non-astigmatic corrections can benefit from this technology. For instance, >a -4.75DS under the above conditions using a +4.00BC has .23D of oblique [quoted text clipped - 3 lines] >minus powers an appreciable thinner and lighter lens. > but .23 cyl to .06 cyl is an improvment of only .17 cyl, which is almost nothing, and we are talking way off center (I'm assuming you're using 18 deg in all calcs, and what does that equate to in mm off center?) >Although not all direct surfaced or free-form lenses are atoric, other benefits >include wider near and intermediate zones (when the progressivity is on the back [quoted text clipped - 3 lines] > > What brands progressives are made with inside adds? thanks w.stacy, o.d. >>Most of my clients wear multifocals, mostly PALs. Off-axis performance at 15 >>degrees is a concern, and is a typical if not conservative reading depth [quoted text clipped - 3 lines] >> >Right, although most or all PALs are not atoric, are they? No. Even amongst free-form PALs very few are strictly atoric. >I mean you'd >have to have some super finishing equipment to generate an atoric inside >curve, and I haven't heard PAL mfrs claiming atoric capabilities, or >have I just not been paying attention???? CNC (Computer Numerically Controlled) technology. Schneider and DAC's RXD lathe are examples. The technology is in its infancy, although I've been using Rodenstock's Multigressiv for at least two years. Very big in Europe and Japan. >No argument that PALs are a challenge esp in the moderate to high plus, >which is where I tend to avoid them. Maybe the Rodenstock Multigressiv? That or Zeiss's Individual (free-form on the front surface). >>A +5.00DS crown glass lens, with the gaze 18 degrees off-axis, an object >>distance of 40cm, and wearers vertex of 12mm will have an oblique astigmatism of [quoted text clipped - 16 lines] >than ordinary aspheric? Theoretically, atorics would improve >dramatically over aspheric but only marginally over best form? My point being if you only optimize one meridian, the other principle meridian suffers. If you optimize based on sphere equivalent it's spread equally along and between the primary meridian. This is the compromise that most manufactuers and opticians use. The best solution is to optimize all meridians by using atoric curves, reducing all off-axis aberrations (except for "Trans" or "Lateral" chromatic aberration). >>Even non-astigmatic corrections can benefit from this technology. For instance, >>a -4.75DS under the above conditions using a +4.00BC has .23D of oblique [quoted text clipped - 6 lines] >but .23 cyl to .06 cyl is an improvment of only .17 cyl, which is almost >nothing, A quarter diopter is probably smallest increment of power we can see, and is probably the reason why the ANSI Z80 standards are based on eighth of a diopter power errors. To be sure, recommending a lens design that costs a hundred dollars extra just to eliminate a .25D of oblique astigmatism might be unethical-the additional benefits from free-form designs (see below) makes sense to those who perform demanding visual tasks. >>Although not all direct surfaced or free-form lenses are atoric, other benefits >>include wider near and intermediate zones (when the progressivity is on the back [quoted text clipped - 5 lines] >> >What brands progressives are made with inside adds? Rodenstock Multigressiv/Impression ILT, Shamir Autograph, Seiko Internal to name a few. Another benefit for moderate to high power minus lenses when the back surface is aspheric/atoric is reduced thickness/weight, as opposed to front aspherics only. >thanks > >w.stacy, o.d. My pleasure. Robert Martellaro ~~~~~~~~~~~~~~~~~~ Optician/Owner Roberts Optical robopt@execpc.com ~~~~~~~~~~~~~~~~~~ "An expert is a person who has made all the mistakes that can be made in a very narrow field." - Niels Bohr One followup on atorics: It would be helpful if there were charts/formulae or what have you that would easily calc the amount and direction of induced cyl from the various lens shapes at various off-axis points on the lens.. I mean if the resultant cyl were a slight to moderate REDUCTION in overall cyl power along the same axis as the prescribed cyl at the reading point, it would be less a problem than if it were, say, a larger cyl at some other axis... w.stacy, o.d. Hi all, Just an update. Went to my eyedoc about a week ago and there was basically no change in my prescription. No reading add or scrip for a weaker pair. After doing some thorough testing, he found it was basically my eyes just telling me to take a break and that there was no need he saw at this time for me to have a reading add. Thanks for all your help through this Jamie I'd be sure to go in for the exam "fresh", that is, not after hours on the computer or in the book. Might get a better refractive result. Also, if the exam corroborates a need for weaker Rx for near, I'd do it in single vision and just swap back and forth, because multifocals of all types are more of a pain than 2 pair for most people who do such concentrated near work. w.stacy, o.d. >Hi all, > [quoted text clipped - 29 lines] > > Dr. Stacy, Thanks for the advice. I always make sure to try and go in fresh to an exam. If I do require an add, The idea of having a weaker pair for reading and the computer does sound like a good idea instead of getting a pair of multifocals. |
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