"Regarding the pin-hole, it does not make the image clear, but I do notice that when pin-hole it requires less straining and effort to get the blurry image into focus. So to express this observation in another way... with no pin-hole it requires a lot of straining to get image into focus, and with the pin-hole it requires a medium amount of straining."
But, at some point it does clear up? To what acuity level does it clear? Can you eventually read the lower lines after you put effort into it or is it blurry always?
If your vision does clear up at any point with focusing or with pin-hole by glasses
or by whatever means then there should be some way of correcting it either with spectacles or vision therapy. If the vision never clears whatsoever and all other disease eye conditions
have been ruled out then the only thing I can think of to check would be neurological.
There are several neurological conditions which do not show up as problems on MRI or other scanning procedures but which can affect the vision. The eye acts as a camera to capture light. Processing of that light does start at the back of the eye, but most of the processing begins after the optic nerve has transmitted that information to the brain.
Again, if the vision ever clears up via pin-hole or spectacles, then there should be a way to maintain that cleared vision. If, as I think you're saying, it does not completely clear then the source of the problem is likely behind the retina and lies somewhere between the back of the eye and the back of the brain, in which case a neurologist would be your next stop.
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