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Medical Forum / General / Vision / January 2006EyeglassExam: Meaning Of "Red-Green Corrected" ?
Hello: Received a prescription from an opthamologist for new eyeglass lenses during visit. He mentioned that I should make sure to request in the future that any new eye exams, and prescriptions, say "Red-Green Corrected". Might someone please explain this a bit for me. e.g. Is it for the prescription exam, or in the making of the lenses ? what exactly is being corrected ? etc. ? Should have asked him, but things were rushed, and i didn't. Thanks, B. I've been in the business a long time and don't know what that means. Ask him for clarification. w.stacy, o.d. > Hello: > [quoted text clipped - 15 lines] > Thanks, > B. perhaps he means that the prescription should be red-green balanced. to assure the patient is not overminused and that both eyes are equal. > perhaps he means that the prescription should be red-green balanced. > to assure the patient is not overminused and that both eyes are equal. Perhaps he means achromatic, which is a term known to lensmakers. After that, there is apochromatic (corrected for three colors c.f. two for achromatic). Well, I noticed here that some eyeglasses are aspheric. So, why not color-corrected as well. There's a bunch of folks for who good enough is not enough, so why not go the whole ten yards. Maybe it can be done for contacts and IOLs. Will there be some special eyeglasses for pseudomyopes. My dentist is wearing little telescopes sticking out from his eyeglasses -- maybe I should have had some of those. -- Dicky (implanted now) he means red/green balance as pclarkii said correctly. Personally, I don't think the guy knows what he is talking about (the ophthal, not pclarkii) as: 1) ophthals can't refract 2) not many people do red/green balance 3) I can't do it and I know what I am supposed to be looking for 4) easy to stuff it up if you are an active accommodater, you will easily get more minus than you need 5) push plus method is much more effective 6) finish in a trial frame with +/- 0.25 flippers to correct for muscle tone and proximal factors. cheers, dr grant The theory is, we want to get you to determine if the letters are sharper on the red or green background.This is using chromatic aberration, or green being bent more easily than red to get the resting point of the script. If the correction is too strong on the + side, the letters look sharper on the red background, if too much minus or not enough plus, then the letters look sharper on the green. This does not work well, in my experience, for hyperopes, who like to accommodte and are used to it, so get too low a script often with this method, and myopes, especially those who do a lot of near work and have an accommodative component to their script, and again get too much minus correction which can lead to asthenopia. dr grant >The theory is, we want to get you to determine if the letters are >sharper on the red or green background.This is using chromatic [quoted text clipped - 10 lines] > >dr grant MY problem is that when looking at eg an ad that has green and red letters near each other, one of them (I forget which, I think it was the red) seems, like in 3-D, to stand up out of the paper and be closer to my eyes. Any idea what that's all about? Thanks, David > > MY problem is that when looking at eg an ad that has green and > red letters near each other, one of them (I forget which, I think > it was the red) seems, like in 3-D, to stand up out of the paper > and be closer to my eyes. Completely normal phenomenon. The red and green wavelengths are refracted to a different extent (red bent less, green more), setting up a disparity at the junction of the colors that give an (erroneous) depth sensation. Ignore it, or filter it (red OR green filters would do). w.stacy, o.d. > > >> MY problem is that when looking at eg an ad that has green and [quoted text clipped - 8 lines] > >w.stacy, o.d. Thanks for the info. However, of all the people I've mentioned it to, I'm the only one who's experienced it. Plus, you're the only o.d. or similar who even recognizes that it happens! Thanks for the nice explanation. David > However, of all the people I've mentioned it to, > I'm the only one who's experienced it. > > Plus, you're the only o.d. or similar who even > recognizes that it happens! Dr. Stacy had it down pat, so I stayed mum. I first noticed it in high school - one of the textbooks had blue and hot-pink on the cover and it seemed to "jump" with each eye movement. Printers and layout artists call it "color vibration". -MT |
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