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Medical Forum / General / Vision / January 2006acuity versus error in refraction
To whom it concerns, Wake up all nitwits, there is no excact conversion possible from diopters into vision acuity and vice versa, period. There is a relation nothing more nothing less. A clip and clear example ace or otis? A blind eye with a refractive error zero (0 diopter) or a refractive error plus ten (+10 diopters) still possess both a vision acuity of zero, cappice?  SignatureFree to Marcus Porcius Cato: ''Ceterum censeo Carthaginem esse delendam" In conclusion, I think that the "Otis therapy" should be destroyed Jan (normally Dutch spoken) > Wake up all nitwits, there is no excact conversion possible > from diopters into vision acuity and vice versa, period. > There is a relation nothing more nothing less. A pretty good statistical correlation. Valid within limits, of course. Go look up the "Dead Horse Equation" on google. -- Robert >> Wake up all nitwits, there is no excact conversion possible >> from diopters into vision acuity and vice versa, period. [quoted text clipped - 4 lines] > > -- Robert One simple question Robert, can you tell me what the refraction error should be when I say the vision acuity is 0.5 or as you might say 20/40? And please tell me myopic or hyperopic (or maybe emmetropic?) or astigmatic. To make it simple, layman (aceotisace) in this NG think they simply can convert vision acuity in diopters and vice versa, forgetting there is more to say when you have to explain for instance a low vision in an emmetropic. SignatureJan (normally Dutch spoken) > One simple question Robert, can you tell me what the > refraction error should be when I say the vision acuity is > 0.5 or as you might say 20/40? And please tell me myopic > or hyperopic (or maybe emmetropic?) or astigmatic. _If_ the error is purely myopic, it is approximately -0.1 diopter. If it is something else, you will have to go fish. Statistics are tools for those who know how and when to use 'em. -- Robert >> One simple question Robert, can you tell me what the >> refraction error should be when I say the vision acuity is [quoted text clipped - 4 lines] > If it is something else, you will have to go fish. Statistics are > tools for those who know how and when to use 'em. Just the answer I needed, statistics don't tell you what type of ametropia exist and what would be the best vision acuity possible. BTW, -0.1 diopters ( about 1/8 dioptr) should make the difference from 20/40 to 20/20 to a myopic with an average BCVA of 20/20? I agree with your ''Statistics are tools for those who know how and when to use 'em" SignatureJan (normally Dutch spoken) 20/40 correlates most often to -1 diopters but your BCVA plays a huge factor. Have a 20/40 BCVA and you could be plano or -.25 and 20/40. Have 20/20 and your typically a -1. Diopters to 20/something values are taken based on a 20/20 BCVA. I know this guy whos 20/40, corrected to 20/15 with -1.5 diopters. -1 diopters gets him to 20/20, but since his eyes are capable of better, -1 is too weak for him. I have heard of people with -2 to -2.5 diopters having 20/40 UCVA, corrected better than 20/15 but its rare! A blind person by our standards is 20/200 or worse BCVA. Many (legally) blind people here do have some vision, but very poor, nonfunctional. I knew this lady in person who was blind but she could see light, darkness, shadows and the outline of large objects. She has light perception(LP) "I know this guy whos 20/40, corrected to 20/15 with -1.5 diopters. -1 diopters gets him to 20/20, but since his eyes are capable of better, -1 is too weak for him. I have heard of people with" and one time, there was this guy at band camp... > Just the answer I needed, statistics don't tell you what type of > ametropia exist and what would be the best vision acuity possible. Graag! Yes, there are many different ways to impair vision, and myopia is only one. > BTW, -0.1 diopters ( about 1/8 dioptr) should make the > difference from 20/40 to 20/20 to a myopic with an average > BCVA of 20/20? This is what the correlation would imply. _HOWEVER_, it is nothing but a correlation with error bands, and most likely centered much higher, around -3-5D. I think most practitioners would report somewhat more for 20/40, say between -0.5-1.0D > I agree with your ''Statistics are tools > for those who know how and when to use 'em" Thank you. Unfortunately, people frequently misuse them with malica a-forethought. "Figures don't lie, byt liars figure" [Mark Twain]. -- Robert A blind eye would have LP or NLP or 20/infinate. A +10 depending on accomodative amplitude has varable accuracy. Say he can accomodate +5 of the +10 diopters, the remaining +5 diopters would give him 20/400 UCVA from distance and worse from near. I heard of one college lady of 18 who was +6.5 and she could accomodate +4.5 diopters and had a manifast refraction of +2 and 20/70 UCVA. She got lasik and is now +2 and is glasses free for now but will soon need glasses again as her accomodative amplitude drops. There is a very close correlation between the two. Diopter is a measurement of the focal point. A +2 lens or an eye with +2 diopters is in focus at half meter and needs a -2 lens to cancel out. Everyone knows more diopters results in more defocus so therefore its predictable. A -3 myope would see worse than a -2.5 myope if both have the same BCVA Dear Ace man, Subject: A dumb comparision. Jan has been taught the box-camera theory. Therefore there can be no relationship between refractive state and visual acuity. And of course, what Jan says is true, the dead eye can have a refractive state of zero, and a visual acuity of infinity -- in a dead person. And of course he is 100 percent correct. Aceman you are a wacco for not recognizing Jans genius. Jan feels much better -- now that he has put you in your "place". But Ace-man, do you feel better for Jan's imparted knowledge? Remember -- the primate data tells the truth about the dynamic behavior of the living eye. Otis > Remember -- the primate data > tells the truth about the dynamic > behavior of the living eye. Of course, human studies are irrelevant because they're "medical" and medicine is not science. -MT > Jan has been taught the box-camera > theory. Indeed, among a lot other interresting subjects on photography by my father who was an exellent amateur photographer. BTW, an eye and a box-camera are not two off a kind TMHO. > Therefore there can be no relationship > between refractive state and visual > acuity. You are an incorrigible old man Otis, misquoting must be lifetime habbit of yours. This is what I stated: Wake up all nitwits, there is no excact conversion possible from diopters into vision acuity and vice versa, period. There is a relation nothing more nothing less. > And of course, what Jan says is > true, > > And of course he is 100 percent > correct. Keep these two in mind Otis. > Aceman you are a wacco for not > recognizing Jans genius. Absolutly true Otis! > Jan feels much better -- now that > he has put you in your "place". Almost, one person to go, gues who. SignatureFree to Marcus Porcius Cato: ''Ceterum censeo Carthaginem esse delendam" In conclusion, I think that the "Otis therapy" should be destroyed Jan (normally Dutch spoken) "Remember -- the primate data tells the truth about the dynamic behavior of the living eye." what does the HUMAN data tell about the behavior of the living human eye Otis? at the very least it tells everyone that otis the engineer is pissing in the wind with his plus lens theory. just because a theory of how the eye works (the "excess accommodation causes myopia" theory) sounds good, and it "feels" like it must be right, and it partially explains some of the data, does not mean that therefore it must be right! when you test it in humans and it doesn't pan out, then its back to the drawing board. not very objective of you to hang onto something thats disproven now is it otis? not very scientific of you is it otis? but alas i forgot-- otis is not a scientist, he's an engineer! go build something otis. or go play some shuffleboard. >>>>Jan wrote >>>>To whom it concerns, >>>>Wake up all nitwits, there is no excact conversion possible from >>>>diopters [quoted text clipped - 6 lines] >>>>plus ten (+10 diopters) >>>>still possess both a vision acuity of zero, cappice? The above is placed because ace refuses to make clear to whom and on what he is responding, a bad habbit of ace. >A blind eye would have LP or NLP or 20/infinate. A +10 depending on > accomodative amplitude has varable accuracy. Say he can accomodate +5 > of the +10 diopters, the remaining +5 diopters would give him 20/400 > UCVA from distance and worse from near. Blind is blind ace, even when accomodating. Besides, accomodating and having an error in refraction of +10 diopters means more error. The example of mine (in the above) is myopic, not hypermetropic. SignatureFree to Marcus Porcius Cato: ''Ceterum censeo Carthaginem esse delendam" In conclusion, I think that the "Otis therapy" should be destroyed Jan (normally Dutch spoken) |
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