Questions tagged [eyes]
The discussion of the anatomy and evolution of eyes. Consider using the "vision" tag for questions regarding how the brain interprets information from the eyes.
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Is there a reason why human eyesight and plants make use of the same wavelength of light?
The accepted range for the wavelengths of light that the human eye can detect is roughly between 400nm and 700nm. Is it a co-incidence that these wavelengths are identical to those in the ...
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Are humans more adapted to "light mode" or "dark mode"?
I was discussing with a colleague about using dark-mode vs. light mode and remembered an article arguing that humans vision is more adapted to light-mode rather than dark-mode:
I know that the trend “...
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How long do your eyes need to adapt to darkness and reach full contrast?
I heard you should wait some time until your eyes adapt to darkness and are able to see smallest luminosity differences, otherwise you might overlook faint objects in the ocular. Are there any rules ...
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Why does looking at bright light trigger sneezing in some people?
Why does looking at bright light trigger sneezing in some people?
Are there any recent studies that have found a cause for this Photic sneeze reflex? The Wikipedia article only references studies ...
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Why can't we see in low light if staring long enough?
For me it seems reasonable that if I kept my gaze on a fixed point in a room with low light, a progressively brighter and better picture would appear before my eyes, just like a camera can see in the ...
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Why do I see different hues of colors between each of my eyes?
Frequently, I see colors with a slightly different hue when looking through my eyes individually. The right eye is more red-tinted ('warmer' hued) and the left is typically more blue-tinted ('cooler' ...
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When did vision evolve for the first time?
Today I wondered what the first organism to evolve vision would have been. I assume that it would have been kind of primitive and basic, but of course extremely innovative and eventually useful to a ...
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How do birds deal with their eyes drying out at high speeds?
My eyes tear up when cycling at 15 mph, which is nothing compared to bird airspeeds.
Do birds continuously produce lots of tears and blink a lot, or do the eyes self-moisturize from the inside ...
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Superhuman eyesight
My ten year old son was reading car number plates that were too fast, too far away and at the wrong angle for any of us to read or even believe that it was possible for him to read. We thought he was ...
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What portion of the electromagnetic spectrum do cats see?
I have seen numerous articles and various information about how cats and dogs see into the ultraviolet spectrum with interesting artistic renderings such as this:
http://www.livescience.com/40459-...
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Do insects with compound eyes have depth perception?
Do insects with compound eyes have depth perception? They fly as if they do, but their eyes are so close together it seems like the image would be 2 dimensional.
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What is the difference between a circular and a cat's-eye (slit) pupil?
I've been to local zoo the other day and one lizard caught my attention: its pupils are circular, which, I thought, is not usual for reptiles. Turns out it is, but now I can't find any explanation on ...
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Why do dog's eyes glow green on a photo?
Taking my current profile picture as a prominent example:
This photo has been taken with flash. As I gather, this is the same effect that makes a human's eyes glow red on photos, namely the ...
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Why do we go blind for a few seconds after switching off the light?
At night, when I switch off the lights, I always seem to go blind for a while. The room becomes pitch black and I am unable to see anything. After a while, however, my vision slowly recovers and I ...
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How does this illusion work?
I found this image on Google+
If you shake your head you can see a portrait of a person. Can anyone explain how the image is constructed in the brain?
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How do we know the presence of light when our eyes are closed?
Last night I laid on my bed and tried to go to sleep with the light off.
I closed my eyes (but hadn't gone to sleep). My younger brother touched the wireless mouse (which had laser) for the laptop. ...
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Are there specific conditions that allow humans to see ultraviolet wavelengths
It is fairly common knowledge that the lens in its normal state absorbs ultraviolet (UV) radiation. An interesting notion has come up from time to time in my reading that suggests there are a small ...
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What's the minimum distance of focus for the lens of a human eye to reach maximum flatness?
According to the Wikipedia article on eye accomodation, the range in which a human eye can focus is from 7 centimetres away up to essentially an infinite distance. Of course, people can't see things ...
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Why do human eyes glow red on a photo and dog's eyes green?
Previous Research
I know that cameras sometimes come with an anti "red eye" functionality that involves two flashes, presumably the second flash coincides with the shutter opening.
Question
Why do ...
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Why can't ciliary muscles in the human eye relax like other muscles?
I had laser eye surgery a decade ago, but in recent years my eyesight has become significantly myopic. I consulted an ophthalmologist to see if this was eye strain because I work at computers a lot, ...
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Can "red" cone cells actually see much red light?
In electronics, the most common color scheme is the "red-green-blue" (RGB) scheme. This choice is often justified by claiming that the long- (L), medium- (M), and short- (S) type cones in the human ...
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How deep under water can humans open their naked eyes without damaging them?
Humans can tolerate a maximum pressure of 100atm, but it becomes uncomfortable above 30 atms. Deep divers usually wear protective equipment like goggles among other things and our eyes seem to be more ...
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Is it possible for two brown-eyed parents to have blue-eyed child?
Here's the (real) story: A young man has stunning blue eyes. On his mother's side are lots of instances of blue eyes, but on his father's side is no history of blue eyes. Both parents have brown eyes.
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Why does this illusion work?
This is another image I found on Google+
All lines are absolutely straight, parallel and perpendicular but why does it appear to have a curvature?
Related: How does this illusion work?
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Is it safe to look at infrared LEDs?
What happens if one looks directly at infrared LEDs? Sometimes I see this kind of LED at night as red dots and I'm also courious about it.
I was wondering what would happen if one looks directly to ...
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What really is color and how do we perceive it?
How do our brains actually transform the information that the cones in our eyes receive into the different colors that we can see and imagine?
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Why can cats interpret things on a monitor/tv, but dogs cannot?
E.g. you can see a lot of videos where cats are smashing some mouse or spider on an ipad, but I have never seen it with a dog. I have a dog myself and I know that he sometimes responds to the sounds ...
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Why can I see a light flicker when it's in my peripheral vision?
When I'm looking at an old CRT monitor or a worn fluorescent lamp, but not directly in the center of my gaze, the light from it seems to flicker. When I focus my gaze onto the monitor or lamp, the ...
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Does your iris color have an effect on your vision?
I've always wondered if having different iris colors, (eye colors) may have any advantages or disadvantages on ones vision. Specifically regarding the effects of light.
Personally, I have troubles ...
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Are rods/cones rejuvenated periodically?
Pretty much what the title states.
Some cells/structures in the human body undergo rejuvenation periodically by flushing away older cells and growth of new ones.
E.g Skin, Blood
Does this (for want ...
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What are the "stars" we see after a bump on the head?
Sorry if this might appear funny. When I close my eyes for a longer time, and suddenly open it, I see some twinkling white small circles, and when i concentrate on anyone of them it disappears, as ...
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What is the use of eye banks, if eyeball transplants do not exist at present?
Corneas are donated and transplanted, but not the eyeball.
I don't understand. What is the purpose of donating a cornea without an eyeball to a blind person?
user10246
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How does laser surgery correct accommodation problems?
When someone undergoes laser surgery to improve eyesight, how does it correct accommodation problems?
Why does it not help presbyopia?
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Do animals with their eyes ~180 degrees apart have depth perception?
Lots of animals have their eyes more on the side of their head, like an octopus or a parrot. Are animals with eyes more on the side able to tell the depth of objects at different distances? It seems ...
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How does the eye know whether to focus further out or nearer in order to bring a blurry object into focus?
If the eye sees an object, but the object is out of focus, the eye could be focusing too near or too far. How does the eye (or the brain) distinguish one situation from the other?
How does it know ...
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How does the cornea breathe during sleep?
The cornea is not supplied with blood vessels and so exchanges gases directly with the atmosphere. So how does it breathe during sleep when our eyes are closed?
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Why does squinting allow you to see objects more clearly?
How does squinting alllow one to see clearer pictures? What are the harmful effects?
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Can frogs see clearly under and above water?
If humans attempt to see underwater, the image is blurred due to refractive differences in air and water that disrupt the normal refractive effect of the lens in the eye. A diving mask overcomes this ...
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Which part of human eyes is getting tired?
It's a thing of common sense that if you read, drive or look at computer screen for too long your eyes will get tired. They burn, itch and try to close all the time.
But I was wondering which part(s) ...
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Do eye muscles relax when you close your eyes?
I wonder whether the eyes muscle relax when you close them. Common knowledge told us the eyes muscle get tense when you stare at nearby object. If you close your eyes, you eye lids have 0 distance ...
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Foveal ganglion cell density (Tay-Sachs Disease)
I’m currently reading on Tay-Sachs disease and have stumbled upon something regarding the typical “cherry red” macula symptom.
On the one hand it is mentioned that the macula is almost devoid of ...
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Does our eyeball increase in size as we grow?
Does the size of the eye increase as we develop from the stage the complete eye first forms to infancy and then to adulthood ?
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Preferred Aspect Ratio for Human Eyes
Our eyes are spherical, our retina is circular, but still our eyes can see more in the horizontal direction than in vertical direction. Why is it so, why is the preferred aspect ratio not square?
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Which shades/hues of color are easiest to distinguish for humans?
I'm trying to represent data graphically and am using a variation of hue/lightness to distinguish one data point from the next. I would like to use a color that would allow me to convey most ...
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Do other animals suffer from myopia or hypermetropia?
Mammals have eyes similar to humas and many other animals like octopuses have a lens in the eye. So do they have such eye defects? If yes, how do they overcome it? Do they feel selection pressure ...
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Why do we blink instead of winking each eye independently?
Question
Why do we blink both eyes at the same time rather than winking each eye as needed?
Why would winking independently be better?
The benefit would be a minor improvement whereby a person ...
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How do our eyes detect light at different frequencies?
Here is my confusion: we can see colored light of different wavelengths: form red to violet. To my understanding, these stimuli cause a confirmational change in the photoreceptors in our eyes and ...
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Why does my eyes see a red spot when over exposed to light?
When I looked into my projector when it was on the blue screen it left a red spot in my vision. I should not have tried it but all the colors left a red spot. Why not a blue or yellow spot was left?
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Cerebral activity during exposure to non - visible light
Our eyes only have the ability to sense light within a certain spectrum. My understanding is that particular frequencies energize specific cells in our eyes, each responsible for a different "color". ...
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Crusty eyes in the morning
Often, after waking up from a night's sleep hard, flaky, pale yellow crystals are deposited around the eyelids (which easily wash off with water).
What are these? Why are they yellow? What are they ...
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