If I look towards the sun with my eyelids closed, and focus, I can just barely make out small red blobs moving along in single files through a maze of straightish lines, against an overall pink/red background.
I’ve always assumed I am seeing red blood cells flowing through the capillaries of my eyelids – but I don’t know how or where to check on this. Actually, if seeing blood cells is that easy, why did it take centuries and the invention of microscopes for them to be commonly known of?
In case this is a factor, I am extremely near sighted. On the order of 20/240 without correction.
uhhh … just a note of advice. Dont look directly into the sun even with your eyes closed. not a good idea…
unless microscopic nano-aliens have invaded your body and are using your eyelids as a supply route, I would hazard to say that is your blood cells flowing. Sometimes I see micro dustparticles flowing around on my eyeball, since they dont move, I aint worried. Oh, and I use a light source like a lamp or overhead light and squint.
That ain’t dust. Those are cells floating around inside your eyes, drifting in the vitreous humour that fills your eyeballs. They’re the dead remnants of a blood vessel that supplied your cornea and lens with blood before your eyes opened at birth.
They’re floaters, multi-cellular debris which wanders around in the vitreous of the globe of the eye. Most human cells are too small to be seen by the unaided eye (Ova are the chief exception).
Uncorrectable 20/200 vision is considered legally blind. I have 20/800 vision, but since it is correctable to 20/15, I am not considered blind (except in the shower).
SpoilerVirgin - You’re completely and hopelessly blind without your contacts but you can see better than the average person without them? I must admit complete ignorance here as I’ve never had vision problems but this seems extreme. Is it common for glasses or contacts to work that well? Do you have a unique condition that causes them to work so well?
Not to answer anything for SpoilerVirgin, but my eyesight was said to be at 20/400 in my left eye and 20/450 in my right eye the last time my eyes were examined (two years ago, they’ve gotten slightly worse since then, and I’m only 20 right now). If I don’t have my glasses on and look at a generic paperback book, it has to be about 5 inches from my face before it’s actually in focus. A few inches further away makes the type mostly legible but extremely blurry (needing some serious squinting). Further than 8" or so and I can’t read anything on the page.
I’ve always been able to get 20/20 glasses (however long they actually last as ‘perfect’ before my eyes deteriorate further is another matter), and I have astigmatism as well. Even my dad, whose vision is somewhere around 20/600, hasn’t really had a problem.
Our glasses do seem to be more expensive, but that’s just anecdotally. We also get compressed lenses. With compression, my lenses are about 1/8" thick, but if I (or the insurance plan or my parents ;)) didn’t spring for the compressed lenses, they’d be at least twice that thickness, if not more.
I believe what you may actually be seeing is the blood vessels in your eyes, not your eyelids. I have looked at a black-light (or was it infra red? Well, something.) and with my eyes open I could clearly see the blood pumping through my own eyes. It was the freakiest thing.
I also believe that when you see ‘stars’ it has something to do with these same blood vessels. Not sure, though, just going by observation.
The human eyes (average) cannot focus on anything closer than 10cm to the eye. It certainly has no way to image blood flow within the eye, on the retina. You may be experiencing changes within the retina caused by blood flow but certainly you are not “seeing” it.
On top of that, since each eye will have different blood flow, whatever you experience as vision in these curcumstances is probably the brain’s best guess as what to do with unintelligible input.
What I saw was a quite clear image of things flowing through tubes. They moved relative to where I turned my head. I dunno what else they could’ve been but actually part of my eye.
Yes, I’m absolutely sure Cecil is right about floaters (what am I saying? could he ever be wrong?) but so far as I could tell he has never addressed the ‘stuff flowing through tubes’ effect I was asking about.
I’m relieved to hear GuanoLad has seen them, too, though I agree they can’t be the blood vessels in your eyes themselves. If I remember my anatomy courses correctly, the blood vessels in the back of your eyes lie behind the retina, and the sides and most of the front of your eyes are opaque to light.
OTOH, as childhood experiments with flashlights show, you can see light through the membranes between your fingers, and I doubt eyelids are thicker than that.
I really do think I must be seeing RBCs, based on how they move, and my being able to see them is due in part to nearsightedness.
How about some empirical evidence? Everyone look at a bright light source (near the sun, not directly at it, of course, or a high watt incandescent bulb) through your closed eyes and report back:
a) Can you see the moving blobs?
b) Are you near/normal/far sighted?
You don’t necessarily have to focus on an object to have a sharp image projected onto the retina. Looking through a microscope ocular can make you see the eyelashes directly in front of your eye, for instance.
I am legally blind without my glasses, but that is very different from being completely and hopelessly blind.
I actually have only moderate myopia (nearsightedness). Myopia is classified as “moderate” up to 20/800, and as “high” above that. Myopia is caused by an elongation of the eyeball, and is generally correctable to 20/20 or better with eyeglasses or contacts. 20/20 itself is just the standard that was chosen to represent average vision. “Perfect” vision, or the best that the human eye can ever get, is about 20/8.
I can’t find any information on how bad myopia has to be to be uncorrectable. There are certain rare forms of progressive myopia that eventually become uncorrectable.
When I am 20 feet away from something, it looks to me the way it would look if you were standing 800 feet away. (That’s an approximation, since one of my eyes is better than the other, and I also have an astigmatism, but you get the idea). That doesn’t mean that I can’t see, just that things get out of focus for me at short distances. Right now I am sitting about 20 feet from the T.V. Without my glasses, I can see that there is a large (32") rectangle of colored light over there, with various blobs of different colors moving around. Another way of looking at it is that my far point, the farthest point at which I can see clearly, is about 15 cm or 5-6 inches. I just tested this with my computer screen, and without my glasses I need to have my eyes 5 inches from the screen in order to be able to read it clearly.
I do wear high index lenses, or as I usually refer to them, “that special thin plastic.” The thick edge is about 3/16 inch or 5mm. They don’t seem like cokebottles to me – at least you can see my eyes through them clearly, without distortion.
I don’t wear contacts, and for obvious reasons I do have to be wearing my glasses at all times, so either drachillix confused me with someone else, or was so overwhelmed by my cuteness that he failed to notice the specs. That’s not as uncommon as you might think. There are people who have seen me face-to-face who are startled when I remind them that I wear glasses. I think they’ve just become so much a part of me that they’re easy to overlook.
Yes, you can see moving blood. Retinal capillaries are IN FRONT of you retina (a fact which skeptics love to use for baiting anti-evolution creationists, as in “how could any ‘creator’ be that stupid.”
One clue is that the moving chains of “stuff” move in a fast-slow rhythm… which is simply your heartbeat.
I’ve never seen chains of red cells, but moving leukocytes are certainly very visible. They act as little transparent holes in the solid-packed chains of red cells in the capillaries. They appear as little moving white dots, each one having a little grey “motorboat wake” caused by firing of edge-detector cells in the retina. If you follow one white dot you’ll often see it perform a little wiggle as it moves. Apparently the retinal capillary bed has vessels which resemble little sine waves.
I usually see the moving white cells after suddenly leaping off the couch while in a well-lit room. For a few moments I can then see my heartbeat as slight surges of brightness in my vision (blood pressure in my head must be momentarily low), and I also see the hundreds of moving white specks all over my visual field, all of them synchronously moving slow-fast-slow-fast (jerking suddenly ahead at one particular point during my heartbeat.)
For the record, I have 20/20 vision with my contacts on, but without them I can’t read past the first line on an eye-chart. The world is simply a mass of fuzzy colorful blobs. Modern optics are pretty amazeing.
