This is all being very interesting.
Is Nava’s analogy of the brain accurate? I would have thought it would be forever trying to get ‘signal’ from the eyes even if they’re not there. We don’t have a ‘turn off eyes’ function. All we can do close the lens caps.
If not, is there something about certain types of blindness that tell the brain not to bother?
Yes of course. But the point was, that you were comparing the blind spot to what we “see” behind us. There is a difference, and it’s a significant difference considering the topic of this thread.
If we were to say that what the blind perceive is like what we see in our blind spot, then the conclusion would be that they do actually perceive something, and have some sense of vision. I don’t think this is what you were arguing.
I will say this about being totally blind in one eye, at least in my case. The good eye sees better with the blind eye open, or at least it tests better on the eye charts. I’ve proven this to myself and clinically. It works this way except when doing close work that relies on depth perception. If you hand me something, or vice-versa, I’ll close the bad eye. I postulate that with it open the brain keeps trying to use it for depth perception, but when I close it the brain relies more on other cues to determine distance.
That’s fascinating. Thank you for sharing it.
<<<<<< Bill doing close work.
I was able to talk with a blind person once , who said that he sees dark gray swirls. I believe he was not always blind so he was able to know what “gray” was.
I was working in a set for a TV show episode that was supposed to be a diffuse white interior (it was supposed to end up looking like when Morpheus and Neo were standing in the empty Matrix and they were surrounded by pure white light.) I was painting the walls a uniform white, so my entire field of vision was white.
I became aware of a blind spot in my right eye. It was kind of like a roundish grey blob in my upper right-ish peripheral vision. If your field of vision was a clockface, the grey blob of “nothing” was at 2 o’clock kind of peripherally in hard to distinguish. It made me kind of nuts because I kept trying to look over that way and of course you can’t actually look at your blind spot. I can’t even tell you if it really was round or what, it was just like a dot of grey.
No matter how much I try I can’t notice it without a plane of pure white in front of me though. And then the blob just looks like an “absence of white” (as far as I can tell. It’s very difficult to process it.)
ETA: It looked exactly like this. But smaller, I think. Hard to tell.
There is a famous case of a guy who went blind around age 3. When he was 46 they found a way for him to get limited sight back by way of stem cells. The problem he ran into was the area of his brain that works with sight never developed correctly so he can’t see a lot of things normally now, such as text. They did a bunch of research on him in order to find out how the brain works.
http://www.nydailynews.com/entertainment/culture/2007/05/13/2007-05-13_seeing_the_light.html
I believe Nava is right about neural pathways. In particular, stories are available in (I think) Oliver Sach’s books. If I’m remembering correctly, I think he describes cases in The Man Who Mistook His Wife for a Hat of people who are either blind or deaf from birth who have operations to restore some sight or hearing. Unfortunately, these people will never have hearing or vision like normally sighted or hearing people - because they didn’t grow up sighted or hearing, they didn’t develop the neural pathways to make sense of what they were seeing or hearing.
They might see the exact same room as someone else, in precisely the same way, but won’t be able to separate what’s important (the giant hole in the floor they’re walking towards) from what’s not (the relatively benign picture on the south wall). Likewise, someone who’s had hearing restored after being deaf from birth can’t distinguish foreground sounds (their co-worker’s question) from background noise (the radio playing three cubes away) - it’s all just a wall of sound. They just can’t process images and sounds the way the normal person can.
I’ve had a similar loss of vision due to trauma (or, rather, my own stupidity, not really trauma) like Wakinyan’s. In organic chemistry lab in college, we were working with some concentrated ammonia for whatever purpose. I had two rags on my bench - one soaked with the ammonia, one wet with regular water. Ignoring all safety protocol and practices, I grabbed one rag, held it up to my nose, and took a big ole whiff to determine which one it was. The ammonia was so strong it totally overwhelmed all my senses - my vision totally went all gray and staticy, like the TV station that won’t come in. There were a few seconds of total panic, then the world started coming back as the smell faded. Definitely scary. Kids, follow all the practices they tell you in chemistry lab. Really.
This may be slightly off-topic, and a little strange.
I don’t have a cite, but I remember some talk about there being some human visual perception behind the knees (i.e. on the backside of the legs.) It might have been some ability to determine various degrees of brightness.
I’m not making this up, and I just thought I’d ask my fellow Dopers before looking elsewhere.
Whenever a waitress hands me a drink, and I take it with one eye closed, I usually say, “I’m not winking at you, I’m just closing my bad eye. Unless the winking works for you, in which case…” Sadly, the winking has never worked, but hope springs eternal.
I suspect the answer to this question might well differ for people blind from birth and those who lost sight. I’ve been blind in my left eye since birth and I agree with this basic sentiment. I’ve had people ask if I could see anything and when I say no, they then ask what if you cover your eye, is it darker? They just don’t seem to understand. It’s not that I see black or gray or white. I see nothing. I am unaware (for vision purposes) that I have a second eye. It’s exactly like saying do you see less or is it darker for your big toe if you have shoes on?
Keep trying! You never know when it might work! 
OldGuy, I must admit, I didn’t get it, either, until my friend explained it to me just that way. Then it all made sense.
I can’t give you a decent link to back you up, but I do remember something about people wearing bright lamps behind their knees to fight jetlag and seasonal depression.
Here you go, there’s already a Cecil column waiting for you.
I developed cataracts after the birth of my first child, and due to my young age and their rapid development they wanted me to go to the best hospital to get them fixed. That and waiting for my kid to be big enough to leave / hub to get a good chunk of time off work to look after said kid, I had to wait from January to October before the surgery was done.
In that time I got to the point where to read required me to hold the book up to within an inch of my right eye, and look at each word at a time. I had trouble crossing roads or walking alone. On the other hand, I could look across at a mountain scene and still see it and appreciate it. But if someone admired the trees, I’d say “What trees?” Friends kept asking me what it was like and I’d say it was like having perfect vision but sitting looking out through a net curtain. My son would either be there in front of me, or not there. There was only a very small distance in which he’d be fuzzy. Made taking a nearly two year old to the park VERY nervewracking!!
When the surgery was done on the first eye, and the bandage taken off later in the afternoon, I just about fell off the examining stool. (I actually told them they need a chair with a back for that bit!) The world was SO BRIGHT and all the colours had come back. I still couldn’t see properly because of all the swelling and of course my glasses were no good, but the brightness and colour I will remember to my dying day.
My son’s hair wasn’t the same colour that I had thought it was. My husband was greyer and more wrinkly (poor guy - he kept telling me to stop staring at him!) My hands had similarly got wrinklier, and I couldn’t eat any meal without staring and staring at it first! I hadn’t missed any of those things, they must have just faded away without my knowing it, but getting them back was nothing short of miraculous.
And my house was FILTHY. Bleh!