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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836 views

What kind of eye strain causes an visual aurora effect? [closed]

When I have done too much reading on the PC sometimes I feel a tickling sensation inside my eyeball. At first I didn't even notice the tickle, however my eye would start to see blurred in one area, ...
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1k views

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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2answers
309 views

Seeing with one eye, why intensity doesn't get half?

Today I just closed one eye(for finding blind spot), and as usual some of the visual field is lost, but I wonder why is not intensity of light(brightness) reduced to half? Shouldn't it be since our ...
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110 views

Insects are attracted to light, what if the light is too bright?

Insects are known to approach light sources. I know that they use it as navigation tools, by maintaining a constant angle between their path and the light beam. However, if a light source is ...
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76 views

The colors blue and golden (yellow-orange) and the human eye / brain

Many years ago I read a review in an article about why we love for example Lapis Lazuli so much. The article stated that there are two specific colors, yellow as golden (when it glows or shines) and a ...
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2answers
152 views

If my sunglasses provide “100% UVA/UVB Protection” why can't look directly at the sun?

Is it simply the amount of visible light entering the eye? I'm simply confused as to why experts say that sunglasses do not provide adequate protection when they are advertised as blocking 100% of the ...
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5k views

Why do we see better on stretching our eyelids to the side?

I've often noticed that on stretching my eyes to the side I see a lot better. On searching, I read that this happens because the cornea reshapes itself (due to the ciliary muscles). But is that all, ...
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3answers
1k views

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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2k views

What are those brown scars in the eyes? [closed]

I have recently realised that one of my friends had brown scars or marks inside his eyes. He says that he doesn't know what they are and has been there since young. What could this possibly be ? Are ...
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344 views

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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1answer
318 views

What is the mass of a human retina?

I'm struggling to find a reference for the mass or density of a human (monkey or rabbit would also work) retina. I'd appreciate any help!
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270 views

Why bipolar neurons in retina transfer information via graded potentials?

Why should bipolar cells prefer graded potentials to action potentials? My attempt: I know that graded potentials are better in processing information since stimulus is directly proportional to ...
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2answers
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Is the bipolar neuron of the retina considered a sensory neuron?

Any neuron that participates in sending impulses from receptors to CNS are referred as sensory neurons. But I often see bipolar neurons of eye(which according to the above definition should be sensory ...
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1answer
52k views

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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1answer
1k views

If mantis shrimp have 16 photoreceptors then how many other colors on the spectrum are there? [closed]

Mantis shrimp have 12 to 16 photoreceptors and humans have 2, and in rare occasions even 3. But if mantis shrimp can see 16, how many other colors are out there? How many photoreceptors is possible? ...
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2answers
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What negative effects can pinhole glasses have on the body?

While shopping in the local supermarket yesterday, I was surprised to find this display on one of the shelves. I also realize that I should have taken a pamphlet with me, as well as a picture of the ...
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3answers
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How can fruit flies and mice share the same gene that says to build an eye if they evolved separately?

I saw a documentary where they inserted the gene of a mouse that basically is the starting "build an eye" command into a fruit fly, and a fruit fly eye grew. My question is, if eyes of different types ...
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69 views

What do I need to do to make a Reverse colorblind image?

As a 15 year suffering from moderate Protan colorblindness, I've wanted to find any advantages of colorblindness. I discovered there are Reverse colorblind tests, which only colorblind people are able ...
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1answer
311 views

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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1answer
2k views

Why can myopic eyes focus on nearby objects, but not on distant ones?

In myopic eyes, far away objects get blurry. I understand that myopia means that the focus of the lenses concentrates light at a point in front of the retina, thus by the point the light rays reach my ...
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62 views

Are there people who can change one of their eyes' depth of focus, while not changing the other eye's?

Are there people who can change one of their eyes' depth of focus, while not changing the other eye's depth of focus, without any surgical or other external mechanical intervention? Edit: let's ...
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1answer
2k views

What is the connectivity between on-center & off-center bipolar cells?

Do rod-photoreceptors only form synapses with on-center bipolar cells (and on-center ganglion cells in the next step)? If so, why is that? Why do rod-cells only connect to on-center cells, while the ...
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1answer
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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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1answer
11k views

What causes the colors we see in eyes?

Genetics aside, what are the biochemical reasons for the different colours of human irises? Also, related, how does eye colour change, particularly in childhood? (example: my eyes used to be blue,...
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1answer
715 views

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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1answer
69 views

Oculus rift (or, what do other eye placements see?) [closed]

I could be WAY out of line in the placement of this question, but here goes: Everyone I'm sure has heard of the Oculus Rift or any of the several other VR headsets making their way around. It ...
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2answers
2k views

How are colors outside the standard RGB color scheme perceived?

I found this image in a German book about biology. It's called DIN 5033 and represents the RGB color scheme. What colors are outside the RGB scheme, i.e., in the black areas of the picture?
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419 views

How do S and L cone cells sense colors like deep blue and red beyond their peak?

So I found this diagram of retinal cone cells: It looks like the S, M, and L cones peak at blue, chartreuse and orange, respectively. If so, how do we see colors past 575 nm and before 445 nm? If the ...
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42 views

Why do eyes close when we sneeze? [duplicate]

It is a behaviour that is very difficult to control. We can't sneeze with eyes open. Is it a reflex of brain to protect the eye from possible injury in sneezing motion or the neural pathway for ...
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3answers
1k views

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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1answer
4k views

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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2answers
353 views

Why can't we half-close our eyes?

Can we half-close our eyes such that they don't vibrate? If not, then why we are unable to half-close our eyes properly? Alternatively, why isn't it possible to keep the upper eyelid close to the ...
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86 views

Why do most fish move fins orthogonally with their axis of symmetry?

So recently I read the question why are most fishes vertical (in the sense of distribution of their body mass) and it got me thinking what is the reason behind the direction they move their fins. My ...
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1answer
397 views

How is color information transmitted from the eye to the brain via the optic nerve? [closed]

I would presume that is has something to do with synapses and specific chemicals starting specific charges through the optical nerve's sub-components, and that this is somehow interpreted by the brain ...
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4answers
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What are the floating translucent little objects called in the field of view? [duplicate]

Sometimes we see these small translucent shapes moving by when the eyes are open. When the eyes are moved they seem to follow that movement, but with a certain delay, as if they are floating in a ...
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1answer
176 views

What is the focus distance of a 3D screen?

I've thought long and hard about wheter this is the appropriate section for this question, because I guess it's kind of an interdisciplinary subject. My understanding of stereopsis (please, correct ...
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1answer
2k views

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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Do squids or octopus suffer from myopia(hyperopia)? Do other vertebrates get myopia(hyperopia)?

Both vertebrates and cephalopods evolved very sophisticated camera-type eyes, and both are capable of focus. But it also pose a risk of inability of focusing, such as myopia in human. So is myopia a ...
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2answers
17k views

Does bright environment strain eyes more than dim?

I'm trying to figure out how to modify my working conditions so that I can program longer without harming my eyes. Because doing so experimentally hasn't given conclusive results so far, I decided to ...
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259 views

Is Near-infrared focused light safe for your eyes?

I found a new product, but I'm afraid it's not safe. Can you help me understand what the safety limits are when it comes to near-infrared light focused on your eyes is? I'm assuming the wavelength ...
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2answers
42k views

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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1answer
164 views

Widest angular of binocular vision [closed]

Which out of eagle, rat, duck or owl has the widest angle of binocular vision? I am pretty sure it's not rat and duck but I am confused between owl and eagle. Can anybody help me figure out which ...
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1answer
4k views

What is the rest state for eyelids - Open or Closed?

If one were to not apply any efforts on the eyelid muscles, will they remain open or closed? In movies when we see a person die, either case could happen - their eyelids could be open or closed when ...
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Why do I see the world in blue when I open my eyes? [closed]

So I was standing outside, waiting for the train. I was tired so I closed my eyes for a while. Then when I opened them, the world was a lot more blue than it normally is - why is this? I tried it a ...
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2answers
307 views

Can we directly stimulate M cones in retina with current technology?

I wonder if we could try to see imaginary "supergreen" color by directly stimulating M cones. For this I suppose we'd need: Non-destructively scan specific human's retina to locate exact positions of ...
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1answer
4k views

Why does our eyes got wet when we feel emotional or whenever we are hurt? [duplicate]

I was thinking like whenever when we feel emotional or whenever we got hurt we got tears from our eyes but why is that happen ? Why our eyes got wet ?
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1answer
732 views

do game animals have poor eyesight?

I have been watching some bow hunting videos on youtube. When hunting with a bow, the hunter needs to get really close to the animal, sometimes less than 10 meters. It seems to me implicitly, and ...
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1answer
150 views

Accommodation mechanism. [closed]

Can anyone explain how contraction of the ciliary muscles causes relaxation of the zonules? Please explain it anatomically i.e. the attachments of ciliary muscles and its relation with the ...
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1answer
8k views

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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1answer
10k views

Why do people sleep with their eyes open?

It's a fact that some people sleep with their eyes open, but why does that happen? Is it normal behavior, not a symptom of any sort of disorder? Are there any (dis)advantages to sleeping with eyes ...