I am feeling bad about the hijack of this thread, and I’m interested in the subject, so I thought I’d try to move the discussion over here. Basically, it’s a discussion of binocular vision, and how people perceive depth perception if they have a vision problem in one eye.
I have 20/20 vision in one eye, and 20/200 or so in the other, so I have lousy depth perception. Wearing glasses helps, and I think I compensate for it in other ways, as well, because I can drive fine, although I’ve always been a washout playing tennis or softball.
My question is this…I mentioned in the other thread that there are other ways that the brain “figures out” depth perception other than through binocular vision. I remembered one from a college course as being the relative size of objects that are close vs. far. Does anyone know what the other ones are?
I don’t have binocular vision, but I can still see how deep things are, through a couple of ways:
perspective, as you point out.
Parallax – how things move relative to each other as I move my head. For example, I look out my window and see the mullion of the window, a power cable, a tree branch, and the house opposite, in that order. As I move my head, the mullion moves a great distance, the power cable moves somewhat less, the tree branch less still, and the house opposite less still, which indicates what order of depth they’re in. (Likewise, the moon, which is a great distance away, doesn’t move at all in your visual field even if you’re in a fast-moving car.)
Focus – Focus works through the deformation of the lens of the eye and therefore only requires one eye to work. When I’ve focused on an object, other objects that are not the same distance away from me (nearer or farther) are out of focus. The effect is subtle.
Knowledge – I know that my bike helmet is on the shoe rack the hall rather than floating in the air between me and the shoe rack; I know the tree is across the street rather than right up in my face; and that adds to my perception of things near them. I also know the positions of my body parts through proprioception, and that allows me to judge the positions of nearby objects relative to my body.
Thanks! I guess I could have looked there. Some of them do sound familiar (this class was gulp 20 years ago!)
I saw your post in the other thread about going down stairs…that’s interesting to me. I always wondered why I can’t walk down a staircase normally! Now I know I’m not just clumsy.
Interesting what you say about staircases, as my vision is similar to yours (although my “poor” eye is not as bad, I can’t remember the figures). I’ve never had a problem negotiating staircases. Unless I think too hard about it, of course, but if you really concentrate on a “natural” activity then even walking can become difficult!
I didn’t have binocular vision until I was 11 or 12, when I got glasses for the first time. I don’t have great vision in either eye, but the astigmatism in my right eye was so much worse that my brain gave up using it. I’ll tell you, it’s a very weird moment when you see in 3D for the first time, especially when you never realized that you didn’t. Perspective and the other cues worked just fine for me to pick things up, hit baseballs, etc.
Even after I had the glasses, the optometrist had to give me some exercises to encourage my eyes to focus in sync better. Interestingly, I noticed that my vision was sharper in general after doing them.
(I never connected any of this before to the numerous flights of stairs I fell down as a child. I just thought that I was clumsy.)
Rule of thumb I was taught was that stereo effects from two normal eyes provide most of the depth perception information out to about 10 feet. After that, the stereo effect is negligible and the rest of the monocular cues predominate.
So other than field of view issues, a one-eyed person & a two-eyed person have functionally equivalent depth perception beyond 10 feet.
It is about a woman who didn’t gain binocular vision until her 40s. The full Oliver Sacks New Yorker article about it is very interesting but apparently not online.
I have no cites (which is sad, because this is GQ and all), but I can tell you that my father has only one eye in total - the other having been removed as a result of a childhood archery accident (no, really! His dad shot his eye out!) and has no difficulties with depth perception. He wears corrective lenses, but that’s largely because his remaining eye is a little myopic - he wears glasses to correct the vision in that eye (and takes them off if he’s doing things within a couple of feet of his eyes - his uncorreted vision, like mine, is great up close and degenerates rapidly the farther away an object is). Some circumstances indicating he has no trouble with depth perception include:
He’s an avid hunter (or was before he got to be in his late-60’s).
He serves as the home plate umpire for the local Little League Baseball in my hometown (and has for some 30-odd years now).
He drives all the time. The only limit on his drivers license is the requirement that he wear glasses while driving - and that’s not because he has no binocular vision, it’s because of the myopia.
He’s a more avid fisherman than a hunter - he takes his boat out in the north Pacific salmon and halibut fishing throughout the fishing season.
He used to build houses for people as a sideline, including roof and second-story external work and never was in any danger of a fall that I know of, saw, or even heard of.
He plays golf like a fiend. My mother beats his score on a regular basis, but that’s mostly because she hits straight and he has a wicked slice.
I’ve never seen him have difficulty catching an object thrown at him as long as it wasn’t coming from his blind side - and I’ve seen thousands of objects thrown at him (he coached baseball, volleyball and basketball at various times).
Binocular vision is not the only way to judge depth perception, and the brain can adjust to getting along without it. My dad’s eye was removed when he was about 7 - so his brain has had 65 years or so to adjust to using cues other than binocular vision.
That is interesting. I suppose that at that distance, it’s easier to use the other cues, such as perspective, also.
The funny thing about this is that I’ve never really been aware of having a depth perception problem until recently. I’ve always known, for example, that I’m bad at tennis, but I don’t consciously perceive things as “flat,” so I didn’t realize lack of binocularity was my problem. It just kind of occurred to me when I tried to take up tennis again at the request of my husband, and I was embarrassingly bad. Games like volleyball, where the ball is bigger and you actually hit it with your hand, and games like golf, where the ball is stationary when you hit it, are not a problem, but trying to hit a small ball in motion with an object like a bat or a tennis racket…forget it…I can’t make contact at all. The only thing I can figure out to account for that is bad depth perception.
That is so interesting! I am going to look for more info.
There was an article in, I think, Discover Magazine recently, which mentioned that human eyesight is markedly better than other primates, and primate eyesight is significantly more accurate than other animals. We can, for instance, see the ridges on a quarter or dime, and most animals aren’t capable of seeing detail that fine.
The reason given in the article is nystagmus, the involuntary movement of the eyes related to vestibulo-ocular reflex - the eyes flickering back and forth as we look at an object. It happens constantly as we look at something, and we’re not aware of it. In an experiment where researchers used (I think) goggles to compensate for nystagmus, the subjects lost a large portion of their fine detail vision. Usually, we speak of nystagmus as a symptom of intoxication, brain injury, or drug use. However, a low, constant baseline version is normal.
By which they meant better than other mammals, I assume. I’m pretty sure that at distance vision, raptors and many other birds kick our hairy, unfeathered, behinds.
I lost vision in one eye when I was 16, just about a decade ago.
It’s absolutely amazing how much you can intellectually compensate for what you physically lack. I was a set designer for my college’s theatre and I could estimate long distances better than anyone else on my crew.
Like I mentioned in the hijacked thread, it’s small distances that are the killers with monocular vision. Judging anything more than three feet away from me is no problem.
My dad does okay with close distances also - for instance, I’ve never seen him miss a nail with a hammer or miss trying to pick something up - or at least not more often than anyone else. Then again, he’s had 55 more years to learn to compensate than you, too - and started at a younger, more malleable age.
I was born with morning glory syndrome, which means I have an abnormally developed optic nerve resulting in very poor vision in my otherwise normal left eye. My right eye is dominant and my vision does not change when I close my left eye. I look normal and do not suffer from Amblyopia(lazy eye), although I fear its development as I age.
My parents were unaware of my vision problems until I was learning badminton and could not hit the birdie. I looked foolish swinging at air heh.
Stairways never seem flat relative to me but then again I’ve never had binocular vision so I can’t compare. 3D IMAX works for me but magic eyes do not. I still have trouble catching/hitting objects but I practice my depth cues by bouncing and catching a tennis ball. I also must wear eyewear to protect my healthy eye from injury. If my good eye goes, well then I’ll be navigating in a world painted by Monet…
I believe the lack of depth perception has allowed me to pursue activities which may otherwise paralyze me with fear. I am an automotive enthusiast and have no trouble getting within inches of another vehicle’s bumper on the race track. I can also jump out of [perfectly good]airplanes with relative ease, and often wonder how spectacular(and scary) the views must be up there for those with binocular vision. This may be compensation for my inability to excel in popular sports such as baseball and soccer.