DeaconBlues wrote:
Tinnitus has, of course, been a part of my life forever.
I was once told there is a pressure point which can (sometimes) turn it off. If you follow the line of your cheekbone backwards, there is a hollow hust in front of your rear. I don't remember whether the relevant point is in that hollow or just below it. I think Chuck knows that sort of thing. Chuck? Anyway, first time I used it, was like magic. Tinnitus started, I pressed the point, it was like turning down the volume to 0 in a few seconds. Later attempts had mixed success, and I haven't suffered from tinnitus for long enough, I don't quite remember where the point is. YMMV.
lau wrote:
how can you show a visual field where a whole chunk of it is... not there. It's not that it's white (one picture) or black (the other picture) or even blurry. It just isn't there. I only notice it's not there if... I know something has happened there, and I haven't seen it?
There are two comparisons. One is that the half of the possible visual field which is behind you is not a big black spot in your visual perception, it's just not there. There is no part of your brain which is trying to look at it. You only get a black spot if a bit of visual cortex is waiting for information it doesn't get. If there is no cortex looking, there is no black spot.
The other thing is that the blind spot, where your optic nerve goes through the retina, so you don't have visual receptors there, is a scotoma that every mammal has (I think every tetrapod, actually, meaning fish, amphibians, reptiles and birds, and mammals). I found a site that lets you
map your blind spot. It's designed for the right eye. Start the applet, close the left eye, fixate the cross with your right, and move to wards the screen until the black dot disappears. Keep your head steady and your gaze fixated on the cross. If you look elsewhere, that screws up the results. Then move the cursor to where you last saw the black spot, until the cursor disappears as well. Move it until you just see it again, click, and repeat. After a while, you will have mapped your blind spot. If you have another scotoma, you should notice that if you move the cursor around and it disappears at another location. You could map that in the same way.
Of course, you don't need a computer for this. You can do it just as well with a piece of paper and a pen.
If I understand what Lau says, a migraine shuts down part of visual cortex for a while and so creates a temporary scotoma. Is that right, Lau?