Meditation on <i>The Mind's Eye</i>
I am a physicist, with a specialty in optics, so I was especially interested in The Mind's Eye, by Oliver Sacks (not to mention the less well known The Island of the Colorblind). The Mind's Eye is a fascinating book about the visual system, many of the things that can go wrong with it, and what we learn from them. It is also the book in which Dr. Sacks reveals that he suffers from prosopagnosia, or face blindness; is not a surgeon because he cannot visualize; and functions only with great difficulty now that he has monocular vision as a result of a retinal cancer. I have great difficulty recognizing faces, but nothing approaching prosopagnosia, and it is a marvel to me that he could cover it up for the better part of 80 years.
Dr. Sacks claims to have had a very acute stereoscopy and even belongs to a Stereoscopy Society. When he lost the vision in one eye, he obviously lost stereo vision, but he also completely lost depth perception. I find that extremely peculiar, because most of us, as far as I know, can walk around with one eye closed and still see depth as a result of what you might call psychological cues; we do not bump into door jambs just because we have a patch over one eye. Indeed, I always walk around an art museum with a program to cover my weaker eye: When I look at a painting, the stereoscopy I get due to having binocular vision tells me that the painting is flat; when I cover one eye, that clue is absent, and the painting pops into life, almost as if I were seeing in stereo. (I would have called it "cyclopean stereo," because it is what I see with one eye, but that term seems to mean something else. Let us call it "monocular stereo." Learning it takes only a few minutes practice.)
What is odd is that, unlike Dr. Sacks, I have always had very poor stereoscopy. Then, when I was perhaps 65 years old, I developed a slight diplopia, or double vision, due to a membrane growing on my retina. I visited an optometrist for perhaps 6 months or a year and did a battery of eye exercises during that time and for several years thereafter. One day, while I was still seeing the optometrist, I looked out my window and noticed that everything popped into stereo -- for the first time, the leaves in the foreground stood out from the house in the background as they never had before. I have since acquired a smidge of macular degeneration, so the diplopia is not so important, and I stopped doing the exercises a few years ago. I am looking out my window right now, however, and the enhanced stereoscopy remains. I still walk around art museums with one eye covered, but I do not think that the monocular stereo effect has changed.
The surprise to me, though, was that my brain was plastic enough to acquire stereo vision after 60-odd years of not having it. I now consider it a miracle that I could play tennis at all.
I billed this as a meditation, not a book review, but I have to say: Read the book! You may find the section about the ocular cancer a little overlong, but otherwise I thought it was typically, Sacksianly fascinating. The only question is why I waited so long to read it.
19 Comments
Mike Elzinga · 5 December 2014
I'm having a rather "interesting" effect at the moment with what is called a "branch vein occlusion." I have a blockage in one of the veins carrying blood out of the eye; and the back pressure has caused swelling in the central part of my eye, making my vision in that eye extremely blurry and distorted.
If I close that eye, I lose my stereoscopic vision. If I open it, I have stereoscopic vision in the areas surrounding the central part of my vision where the swelling occurs, but a strange seeming increase in distance of objects in the central part where I can distinguish letters with my good eye. I frequently miss when reaching to pick up small objects.
I have another retinal exam coming up, so I don't yet know the prognosis for this.
Zetopan · 5 December 2014
I have an unusual eye condition that both helps and hinders. Firstly, I have very different magnifications in each eye - and I mean large differences not small differences. Secondly, I have very different color vision in each eye, and this actually provides better color discrimination that what most normal vision people can achieve. Color vision discrimination tests that are trivial for me to get exactly correct are quite difficult for everyone that I know.
Palaeonictis · 5 December 2014
I actually have 20 by 15 vision, which just to clarify I don't mean to boast. Although quite frankly the cephalopod eye is superior to ours (= vertebrates), so my vision compared to them isn't good after all.
TomS · 6 December 2014
Zetopan · 6 December 2014
"See the Wikipedia article âTetrachromacyâ."
Thank you but I am actually familiar with that and I don't seem to have that condition. Firstly, that condition has been known to be sex linked and hence restricted to females, which I am not (at least as far as I know). Secondly, one eye has everything as being more reddish and the other eye has everything as being more bluish. This is most noticeable in the yellowish part of the visible spectrum. Tetrachromats on the other hand can see shorter wavelength off the blue end of the visible spectrum, which I don't think I can (at least I have never been tested for that).
Robert Byers · 6 December 2014
I have been blind in one eye since I was twelve and now its decades later. The other eye also having serious issues.
I never heard of this, one eye equals interference general sight.
Why should it?
i have seen this Sacks stuff on youtube things if the same guy.
I don't agree its amazing that the sight reorganizes itself as pointed out here.
We do not see anything. We only observe a memory of what our eyes record and place in the memory.
So all that is going on is minor memory reorganization.
Its not surprising to see quick adaption.
it should be understood all senses are used by us exclusively through the memory mechanism.
Its not that complicated despite God making it indeed complex.
Keelyn · 6 December 2014
harold · 6 December 2014
callahanpb · 6 December 2014
Since we're sharing... I had good vision in both eyes until recently and normal stereoscopic vision as far as I know. I liked Matt Young's "monocular stereo" point. On a similar note, I would sometimes look at 3d surfaces and try to turn them inside out mentally (so e.g. a bump looks like a dent). This is possible with one eye closed, but I don't think I ever managed it with both eyes open, which is how I conclude I have normal stereoscopic vision.
As of last year, I started needing reading glasses. That part is expected, but I also find that I have lost my distance vision in one eye, particularly at higher wavelengths. Red traffic lights at a distant turn into asymmetrical splatters rather than points. It's quite disconcerting having my eyes showing different images. My optometrist didn't seem alarmed by any of this, and suggested it could be astigmatism. He also agreed with my thought that it might be an early sign of cataracts. Once the optics are corrected, my vision is still good, so I don't think it's anything going on with my retina.
I'm curious if anyone with previously good vision had this happen in middle age. I thought I was prepared for presbyopia, but this is more than I signed up for, and I have to say it's kind of a bummer, though small in the scheme of things.
Matt Young · 6 December 2014
I have always had very slightly different color vision between my two eyes, but it was generally apparent only when looking at something off-white. My right eye sees slightly colder tones -- less red -- so the effect may be the result of looking into too many helium-neon laser beams before we knew any better. I remember aligning a ruby laser using a (red) helium-neon laser, and only a very small fraction of the total power in the helium-neon laser beam made the blue sensitivity of my eye disappear for a short while. (My mother took the occasion to remind me that her friend, a radiologist, was sterile, as was his partner, but we will not go into that now.)
When I got the epiretinal membranes, which are growing over my maculas, I began to lose blue sensitivity in the macular region. It is generally not noticeable, unless I happen to be looking through a cobalt blue filter, but blue LED's and flashing police lights disappear as soon as I look directly at them. I reported it to my ophthalmologist, and she said, "Oh."
I too hope that Mr. Byers deals with his condition successfully.
Just Bob · 6 December 2014
https://www.google.com/accounts/o8/id?id=AItOawmKClPHRhWOQyCVGlIJhJOKy_uJujWHa74 · 6 December 2014
Speaking of brain/vision adaptability, roughly 20-25 years ago I saw a documentary (on PBS, I think "Nova") of an experiment in which a grad student volunteer had a mask with lenses placed over her eyes for a couple months. As you all probably know, the eye focuses an image on the retina upside-down, and our brains compensate for that. Her lenses switched the image to right-side up. After about a month, she could see normally with the lenses. After the lenses were removed, she saw everything upside down for a while, and then her brain relearned how to compensate.
About a year ago I suddenly had extreme double vision. While walking along a sidewalk, my left eye saw the sidewalk continuing at ground level, and my right eye saw it slanting up above the next telephone pole. Two ophthalmologists and one GP doctor later, a CAT-scan technician diagnosed the cause as a sinus infection in my right macular sinus (under my right eye) which was putting pressure on the eye socket. I had an operation to remove gunk from that sinus and was told I might need another operation to adjust the orb. Whether the orb adjusted itself or my brain learned to compensate, I never had the second operation but see as well as normal again.
Off-topic - that was my first medical problem since breaking my nose in high school, and did not leave a good impression of the medical profession. I had to fill out identical two-page forms three times for different doctors, and one surgeon charged me $560 for a half-hour visit in which I filled out the form and waited for 15 minutes, then when I saw him he spent three minutes looking at the DVD of my CAT-scan, and twelve minutes telling me what a great surgeon he was and what techniques he would use. I decided not to use him for the surgery, so from my point of view he did nothing useful for his $560. From his point of view, he may have spent about a half-hour of his valuable time on me, including a phone conversation with my GP who recommended him.
JimV
Marilyn · 7 December 2014
The first time I watched a 3D film with a pair of those red-green plastic/paper glasses when I took them off I could only see in black and white for a good few minutes, that was scary, I wear the all black ones now. Also once on an occasion after that I was sat at the side of the window concentrating reading not noticing the sun was shining across my eyes and when I looked up, again I could only see in black and white.
Joe Felsenstein · 8 December 2014
My vision is very boring (nearsightedness and astigmatism, fully correctible by lenses). Am waiting to see when, probably soon, I will start getting my parents' macular degeneration issues. This is all very routine.
But one interesting experience was having some facial bones broken in my 20s, and then being operated on which involved incisions near my left eye, but not directly involving the eyeball. For some days afterwards I had stitches just below my left eye and on the zygomatic arch just above it and to the left. They put a big gauze pad over my left eye to cover them. It didn't totally cover the eye. People used to stare at me wondering how large a hole I had in my head. I could see past the pad on the right side of that eye's field of vision.
The result was that when the stitches were taken out and the pad was removed I found that my left and right eyes were not synchronized. If I looked straight ahead the images were superimposed, but when I tracked my eyes right or left the two images separated. Basically the horizontal planes in which my two eyes moved had become different by a few degrees. The result was double vision.
I was quite alarmed at this. Fortunately it self-corrected after a few more days. The lesson is that the muscles that move your eyeball are continually adjusting their actions based on how well the images from your two eyeballs correspond. The horizontal planes in which your eyes move are the same, but only because of this self-correction.
KlausH · 8 December 2014
KlausH · 9 December 2014
I don't think I am directly seeing ultraviolet; I think I am picking up a harmonic. Is the wavelength of yellow-green a multiple of near ultraviolet?
Zetopan · 9 December 2014
Examining a rainbow is not a valid way to determine your color vision characteristics. Likewise, the most common forms of color vision testing are only designed to determine if the subject has some form, of color blindness, so those are inadequate as well. Doing a proper test would involve using a monochromator with a broad spectrum light source.
http://en.wikipedia.org/wiki/Monochromator
davemullenix · 12 December 2014
KlausH,
UV-A runs from 400-315 nm.
UV-B runs from 315-280 nm.
UV-C runs from 280-200 nm.
UV-Vacuum is 200-100 nm.
X-rays start at 100 nm.
Yellow-Green is about 590 nm. 1/2 of 590nm would be 295 nm which is right in the middle of UV-B.
Matt Young · 13 December 2014
I will be surprised if Mr. H is seeing a harmonic -- second-harmonic radiation generally requires considerable irradiance. Additionally, if he saw a harmonic of, say, red light, it would appear in the red line of the rainbow, not below the blue.
More likely, his ocular media are unusually clear, and he sees short wavelengths that are absorbed or scattered in other people's eyes (how old are you?). I cannot account for why he sees an "extra," infrared band, but the infrared radiation he sees can certainly not be a harmonic, since infrared is a longer wavelength than red. Possibly turbidity in the ocular media preferentially affects red sensitivity as well as blue, but if so I have never heard that.
Finally, I propose an experiment: Find some very young people, say 10 years old, who have vision that is correctable to 20/20, and see whether they see the supposed ultraviolet and infrared bands. As you get older, the net transmittance of the ocular media decreases markedly, and I understand that it may be as little as 10 % in an old person. Children are the place to start.