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Medical Forum / General / Vision / January 2007Shocking Clarity: Reading thru a small hole
Background: I had cataract surgery in my good eye last year and the vision is set for 16." I wear -2.50 glasses with little bit of astigmatism correction (-.75, 170) for distance vision. When my doc tried that astigmatism correction with no spherical correction to see if my near vision could improve, my near vision became less clear. So, I & my doc decided that I wear nothing for reading. After all, my near vision, tested with a reading card, is 20/20. Last night, I was reading a book and happened to momentarily read it through my wedding ring. I noticed something and did some experiment. When I was reading through a small hole (1/4 inch diameter or so), print looked extremely sharp and ultra clear. I was completely amazed. I continued the same experiment, holding various books and newspapers at 16" distance & reading normally and through a small hole. The same result. So, my questions are, "Why does reading through a small hole make such a difference?" & "Does it mean that there is room for improvement in my near vision?" I'll see my doc next month and I want to be armed with some questions for him regarding this. Thanks. > Background: I had cataract surgery in my good eye last year and the vision > is set for 16." I wear -2.50 glasses with little bit of astigmatism [quoted text clipped - 15 lines] > vision?" I'll see my doc next month and I want to be armed with some > questions for him regarding this. Thanks. What you are describing is how an aperture works on a camera, and how it changes the amount of light and the depth of focus of an image on a film plane. http://en.wikipedia.org/wiki/Aperture I'm suspicious of what you are describing; it doesn't add up. True, a pinhole will give you sharp vision, but you should be getting sharp vision with that eye without any Rx at near, or if the astigmatism is indeed blurring you, that weak pair should have worked. So I'm thinking that astigmatism Rx is off. Unless, perchance you were talked into getting a multifocal IOL in which case yes, the pinhole effect will clear the horrible optics of those terrible IOLs. Unfortunately, it's not too pleasant to have to wear pinhole glasses. Or, per another chance, were you doing this on your "bad" eye? w.stacy, o.d. >Background: I had cataract surgery in my good eye last year and the vision >is set for 16." I wear -2.50 glasses with little bit of astigmatism [quoted text clipped - 17 lines] > > > I'm suspicious of what you are describing; it doesn't add up. True, a > pinhole will give you sharp vision, but you should be getting sharp vision [quoted text clipped - 7 lines] > > w.stacy, o.d. My description is true and that's why I'm so puzzled. I have an Alcon monofocal (didn't want to take a chance with multifocals and don't mind wearing glasses) and I think the astigmatism Rx is more or less correct. I've had several post-ops and the astigmatism Rx has been the same. So, I guess there are two possibilities. 1. My doc tried a wrong astigmatism Rx for my near vision. 2. Or, astigmatism of my near vision is different from that of my distance vision <-- Is this possible? > So, I guess there are two possibilities. > > 1. My doc tried a wrong astigmatism Rx for my near vision. > 2. Or, astigmatism of my near vision is different from that of my distance > vision <-- Is this possible? It is #1. #2 is not possible. w.stacy, o.d. On 1/19/07 1:58 PM, in article babsh.72$GY7.4@newsfe11.lga, "Fidelis K" <sdfs@hotmail.com> wrote: > Background: I had cataract surgery in my good eye last year and the vision > is set for 16." I wear -2.50 glasses with little bit of astigmatism [quoted text clipped - 3 lines] > I wear nothing for reading. After all, my near vision, tested with a reading > card, is 20/20. I only understand a bit of this paragraph. > Last night, I was reading a book and happened to momentarily read it through > my wedding ring. I noticed something and did some experiment. When I was > reading through a small hole (1/4 inch diameter or so), print looked > extremely sharp and ultra clear. I was completely amazed. I continued the > same experiment, holding various books and newspapers at 16" distance & > reading normally and through a small hole. The same result. Ah! 16. " means 16" . > So, my questions are, "Why does reading through a small hole make such a > difference?" & "Does it mean that there is room for improvement in my near > vision?" I'll see my doc next month and I want to be armed with some > questions for him regarding this. Thanks. A 1/4 inch hole is LARGE for this kind of test. Your eye's pupil is not likely to have opened up that much unless you are in pretty dark environment that would make reading difficult. A 1/16 inch or smaller hole seems to me to be a more realistic size. What it indicates to me is that you do not have a good prescription or that your eye is aberrated to the extent that you cannot get sharp vision. How big is your pupil? What a small hole does is to limit the area of the eye's optical system thereby avoiding the most aberrated portion of the eye. If by chance your pupil is indeed larger than 1/4 inch, the outer part of the eye lens and cornea will contribute most of the spherical aberration. That would be avoided by using the hole. It is this spherical aberration that degrades the visual acuity when your eyes are dilated for examination. I am not medically trained. I resort to my knowledge of optical physics to reach my opinion. Bill -- Fermez le Bush--about two years to go. > So, my questions are, "Why does reading through a small hole make such a > difference?" & "Does it mean that there is room for improvement in my near > vision?" I'll see my doc next month and I want to be armed with some > questions for him regarding this. Thanks. This is a well known optical fact. If you just turn up the light, your pupil will constrict and you will have a natural small hole. This might well help with your astigmatism, as well as your other vision. >>So, my questions are, "Why does reading through a small hole make such a >>difference?" & "Does it mean that there is room for improvement in my near [quoted text clipped - 4 lines] > pupil will constrict and you will have a natural small hole. This might > well help with your astigmatism, as well as your other vision. Or it can hurt, as when you have a CENTRAL opacity, on which fact is based the BAT (brightness acuity test) w.stacy, o.d. > > This is a well known optical fact. If you just turn up the light, your > > pupil will constrict and you will have a natural small hole. This might > > well help with your astigmatism, as well as your other vision. > > Or it can hurt, as when you have a CENTRAL opacity, on which fact is > based the BAT (brightness acuity test) Hadn't thought about that, and didn't know about the BAT. When I had cataract, I guess that is what I had? On second thought, no. >>>This is a well known optical fact. If you just turn up the light, your >>>pupil will constrict and you will have a natural small hole. This might [quoted text clipped - 5 lines] > Hadn't thought about that, and didn't know about the BAT. When I had > cataract, I guess that is what I had? On second thought, no. Most cataracts that are operated for have some central opacity. The test really is for those who have sufficient clear lens periphery to do ok in low light but who are essentially "blinded by the light" of the BAT. It's how you can often justify cataract surgery on someone who has 20/20 vision. |
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