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Medical Forum / General / Vision / December 2006Myopia & hyperopia
Why is it that my mother with her +3 prescription for distance can see better without her glasses than I can without my -2.75? She also has some stronger glasses for reading. > Why is it that my mother with her +3 prescription for distance can see better > without her glasses than I can without my -2.75? She also has some stronger > glasses for reading. Easy. She has pinpoint pupils. DrG Shooting from the hip again, eh, Leukoma. > > Why is it that my mother with her +3 prescription for distance can see better > > without her glasses than I can without my -2.75? She also has some stronger [quoted text clipped - 3 lines] > > DrG > Shooting from the hip again, eh, Leukoma. Why not. You shoot without looking. -MT > Shooting from the hip again, eh, Leukoma. I would say that even from the hip, I hit the target more often than you do. Actually, if the mother is presbyopic, she should not be able to accommodate through 3 diopters of hyperopia, and her distance visual acuity should be approximately the same as her son's 2.75 diopters of myopia. The size of the blur circle ought to be about the same. Miosis, however, occurs when the ciliary muscle tries to accommodate. That, plus the miosis that naturally occurs with age, would tend to support my theory that the mother would enjoy the benefits of greater depth of field. Do you have anything constructive to say? DrG > Why is it that my mother with her +3 prescription for distance can see > better > without her glasses than I can without my -2.75? She also has some > stronger > glasses for reading. You see *much* better than she does up close; she sees better far away. -MT Yes she does have tiny pupils!! Years ago she was told by her optician that she should wear her glasses constantly but she never has. Perhaps she never really needed to? OK then she likely has both accommodation and depth of field working for her. Depending on her age, one factory may be more effective than the other. w.stacy, o.d. > Yes she does have tiny pupils!! > Years ago she was told by her optician that she should wear her glasses > constantly but she never has. Perhaps she never really needed to? I am surprised by the answers, which might have some truth to them, but don't address the obvious answer. Obviously we have to make some assumptions about your ages, and I'll guess you are a teenager and she's 40ish. If so, and if she's under age 55, she has a significant amount of accommodation she can use to focus through her hyperopia. You can't do this because there is no such thing as "reverse" accommodation. You cannot focus any farther away than about 35 cm. Accommodation for you only focuses you NEARER than that, which is obviously counterproductive when gazing at more distant objects. Pupil size might play a minor role here (smaller pupils increasing depth of field) because she likely has smaller pupils than you, although that is speculation. I seriously doubt that she has "pinhole" pupils. w.stacy, o.d. > Why is it that my mother with her +3 prescription for distance can see better > without her glasses than I can without my -2.75? She also has some stronger > glasses for reading. The man said his mother has small pupils. I win! In fact, I win twice because Otis responded to my post and made a fool of himself...hehehe. DrG > I am surprised by the answers, which might have some truth to them, but > don't address the obvious answer. Obviously we have to make some [quoted text clipped - 14 lines] > > without her glasses than I can without my -2.75? She also has some stronger > > glasses for reading. A reasonable assumption, although I've seen some young hyperopic mothers who have pretty good sized pupils. Re otis, he actually posted some decent items lately, but then unfortunately relapsed into his droning mantra on myopia, now even claiming hyperopia prevention. Next he'll be curing astigmatism, presbyopia and heterotropias. The man is indeed a fool, although I'm not sure the post you're talking about is a good example of that. It's those little glimmers of apparent intelligence that occasionally peek through his haze of dementia that puzzle me. Maybe it's like ocean sailing. Long periods of relaxing boredom broken by occasional episodes of startling terror, fortunately not long lasting. In dementia, long periods of irritating nonsense broken by occasional episodes of startling lucidity, unfortunately not long lasting. w.stacy, o.d. > The man said his mother has small pupils. I win! > [quoted text clipped - 21 lines] >>>without her glasses than I can without my -2.75? She also has some stronger >>>glasses for reading. Even a stopped clock tells the correct time twice a day. DrG > Maybe it's like ocean sailing. Long periods of relaxing boredom broken > by occasional episodes of startling terror, fortunately not long > lasting. In dementia, long periods of irritating nonsense broken by > occasional episodes of startling lucidity, unfortunately not long lasting. On 12/17/06 3:47 PM, in article 1166399249.446890.86890@t46g2000cwa.googlegroups.com, "Dr. Leukoma" <drg@leukoma.com> wrote: > Even a stopped clock tells the correct time twice a day. That statement is certainly true, but the typical stopped clock provides zero information! Put another way, You cannot rely upon a stopped clock for navigation. While a slightly slow or fast clock (every clock is either slow or fast) can be used to navigate for a considerable time after it has been set correctly. Thus, aphorisms such as the one quoted above have no real utility. Bill -- Fermez le Bush > That statement is certainly true, but the typical stopped clock provides > zero information! Put another way, You cannot rely upon a stopped clock for > navigation. While a slightly slow or fast clock (every clock is either slow > or fast) can be used to navigate for a considerable time after it has been > set correctly. Thus, aphorisms such as the one quoted above have no real > utility. If a person glances at a stopped clock, and doesn't know that the clock is stopped, the person might conclude that the clock is indeed providing the correct time, in which case the clock was providing misinformation if the person acted on it. The person would only know the clock was stopped if they looked at the clock again some time later and the time it signified was still the same. For exactly two moments everyday, the clock is indeed signifying the correct time. DrG On 12/18/06 4:55 AM, in article 1166446557.384085.299500@48g2000cwx.googlegroups.com, "Dr. Leukoma" <drg@leukoma.com> wrote: > If a person glances at a stopped clock, and doesn't know that the clock > is stopped, the person might conclude that the clock is indeed [quoted text clipped - 5 lines] > For exactly two moments everyday, the clock is indeed signifying the > correct time. It is this kind of logical process that causes me to question everything you aver. No matter how you cut it a stopped clock is useless for any purpose. An inaccurate clock can be used for measuring time differences with little error. Indeed, chronometers were labeled with their average error rate. That enabled them to be used for months or even years of navigation with reasonable accuracy even though they ALWAYS read incorrectly. Bill -- Fermez le Bush > On 12/18/06 4:55 AM, in article > 1166446557.384085.299500@48g2000cwx.googlegroups.com, "Dr. Leukoma" [quoted text clipped - 19 lines] > Bill > -- Fermez le Bush Sometimes, dear navigator, clocks are just used to tell time. -bg |
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