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Coachrobmd, Doctor (non-eye specialty)
Category: Eye
Satisfied Customers: 1785
Experience:  Medical Internist
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When I strain/tense my eye muscles, I'm able to get my

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When I strain/tense my eye muscles, I'm able to get my near/far vision clear. When I also add a little astigmatism correction to this (or pin-hole), it gets even clearer.

My understanding is that pin-holing removes the variable of refraction? So the fact that pin-holing does not get my vision clear (only straining does), means my vision issue is not due to refraction error?

What physical change am I'm inducing when I strain to get vision clear? (Again, when I strain, near and far are clear, when I relax, near and far are very blurry.)
this is called Accommodation,it is the way the eye increases optical power (the degree to which the lens converges or diverges light). This is necessary to produce a clear image (focus) on an object when it draws near the eye. A lens that is more convex( fatter in the middle) would refract more light rays than a less convex lens( thinner lens). The lens can change shape because the cells of the lens contain an elastic crystalline protein. The young human eye can change focus from distance to seven centimeters from the eye in 350 milliseconds. The eye focuses on a given object by changing the shape of the eye lens through accommodation. This is controlled by ciliary muscle,which is attached to the lens.
Unless you have any other questions please press ACCEPT so I would get compensated for my time and answer
Customer: replied 5 years ago.
I already know everything you said, as it's basic knowledge. That was not my question.

Also, if I was accommodating, it would expect it to make my near-vision clearer, not infinity distance. I can't find any plus nor minus powers to make my vision clear, but straining does.

(I need a highly skilled Board Certified Ophthalmologist for this question.)
The process of straining the eye muscles is used to change the shape of the lens. This can actually improve near OR farsightedness due to the degree of change of the lens shape. As we age, the lens become less flexible and taken to the extreme, may form cataracts.

The reason pinhole boards work is that the send light through just the CENTER portion of the lens, and prevent refractive error from the edge of the lens, which becomes distorted more rapidly than the central portion of the eye. This refractive error is prevented by taking the full light source down to a very narrow band through the pinhole and sending it through just the CENTER of the crystalline lens.

You should understand something unique about the eye's lens. It is the ONLY tissue in the human body that lays down new cells on the OUTSIDE, so that the older, more senescent cells are trapped. This is what makes the lens thicker and less pliable as we age, and leads to presbyopia.

In the skin we flake off dead skin. In the GI tract, we shed off mucosa and pass it out as waste. With the eye lens, that cannot happen and thus the new cells are laid down in a somewhat uneven pattern, causing the refractive error mentioned above.

Plenty of people who have near sight strain to see things far away. The ciliary body has opposing fibers and can both collapse and expand the eye's lens. I'm doing it at this very moment looking out my window as I try to focus on a distant bird without my glasses on.

Is this the answer you're looking for? If so, please click ACCEPT so I can receive credit for my answer.

If not, could you please clarify your question so I can try further? Thank you so much. (This does not replace a physician visit.)
Customer: replied 5 years ago.
ok, that's interesting the ciliary muscles can exert effort to flatten the lens also; I had thought their flexing could only curve it.

So I'm left with the dilemma of how to get clear vision without straining? None of the lens powers tried have helped. Should a lens help with this, if so, plus or negative?
or - is best determined during refraction with a pheropter in the eye doctor's office. It's not possible for me to determine that from a distance and not examining you.

It really seems like you need an eye exam that includes:
1. testing for glaucoma
2. visual field testing
3. anterior chamber evaluation
4. tests of accommodation
5. dilated exam to look at the back (retina) of the eye and the lens itself
6. color blindness testing if it was never done

And the ciliary muscles are much more complicated than people believe. My father was an ophthalmogist for 49 years and we were constantly discussing eye problems.

So, see an optometrist or opthalmologist, get good visual testing, and perhaps glasses. They'll need to check you for +/-, sphere, and axis as well, something that takes a good deal of training, You cannot do that for yourself.

POSITIVE feedback is FREE for you to leave about our session today. It is very important for me to get feedback so I can help customers the best way possible. This is VERY different than an office setting where I can see if you're satisfied with our discussion. Please consider taking one minute to fill this out. Thank you.
Coachrobmd, Doctor (non-eye specialty)
Category: Eye
Satisfied Customers: 1785
Experience: Medical Internist
Coachrobmd and other Eye Specialists are ready to help you
Customer: replied 5 years ago.
Yeah, I've had all those tests done by 9 different opthalmologist in several cities, including Duke, Mayo, etc. and no one can figure out what my prescription is. It's very frustrating, so I was hoping to figure things out with the help of this site.
It's awfully tough for us, who can't examine you, to beat the guy who has you in his office when it comes to diagnosis. The best thing we can do is broaden your horizons by coming up with alternate differential diagnosis that you can then bring in and discuss with your doctor.

Thanks for the positive feedback by the way. I really do appreciate it.

On thing you MIGHT ask is if a prism added to the lens will make a difference. At times, this is overlooked, and it can make all the difference. But I'm sure at Duke and Mayo the considered that option.

Hope I've helped you a little bit.