Questions tagged [human-eye]

Questions about the biological function and structure of the human eye.

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2answers
231 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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4k 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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1answer
69 views

What is a good set of notes to study human's eye mathematically?

I want to learn about the human eye. I could read a lot of online literature about it. However, ideally I would like to study human's eye by solving some maths exercises. I suspect people have done ...
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0answers
1k 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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2answers
343 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
2k views

Telling distance with one eye

Basic mathematical/logical reasoning makes it clear that you need two eyes to have depth of vision. By seeing an object from two perspectives, our brain can calculate the distance of the object based ...
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1answer
291 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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0answers
263 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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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
303 views

Are brown eyes healthier than blue eyes? [closed]

I have read somewhere brown eyes have more melanin than blue eyes and as melanin protects our body from cancers, I thought that brown eyes are more healthier.
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3answers
9k views

Why does closing one eye in bright light allow me to open the other?

I often find it physically painful to open my eyes past a squint after stepping out into the full summer sun. However, if I close one eye entirely, I can keep the other open without pain. This seems ...
11
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1answer
3k views

Do colour blind people see white?

I know that white colour is perceived on excitation of red, blue and green cones simultaneously. It is also said that a colour blind person doesn't see a particular colour and just perceives it as a ...
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0answers
365 views

Can human perception differentiate between monochromatic and polychromatic light?

Maybe monochromatic is not the right word, what I mean is light consisting of a single wavelength (i.e. a spectral color) versus light composed of photons of multiple wavelengths (intermediate color). ...
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0answers
61 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
470 views

Why are we able to differentiate between colored objects without the presence of light?

Rods help us to see during the dark. We can see colour of the object when it reflects light. But in a dark room(room of any color but the light is switched off and it is night),we still can ...
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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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586 views

Is the human eye supposed to see the lense effect?

Just as the GoPro cameras, we need lenses to be able to focus. Nevertheless, we can see the "fisheye effect" on the shots taken by GoPros. I am talking about this: Is it possible to notice the "fish ...
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2answers
347 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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0answers
74 views

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
188 views

What is a 5'-cGMP?

I know in cGMP , there is a bond between phosphate, 5' and 3' C of sugar , but what is 5'-cGMP? [It is involved in cascade of vision.]
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2answers
1k views

Could there be any effects from low powered infrared being used to track eye movements long term?

Basically, looking into infrared LED's and a camera with an infrared bandpass filter for tracking eye movements; my concerns are whether there would be any potential negative long term effects from ...
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2answers
9k views

Why does getting soap in your eyes cause redness and irritation?

I am wondering why do eyes become red after getting soap in them. What is the cause behind it?
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1answer
2k views

Why do we see black when we close our eyelids? [closed]

Why do we usually see black when we close our eyelids assuming there is no strong light source outside? I realize we never really stop seeing as long as our eyes are healthy but based on assumption ...
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1answer
4k views

Why do eyes feel overwhelmed by light when we wake up?

Many people (I saw a 9gag post 3 days ago and couldn't find it, I'll edit later if I do find it)experience dry/hurting/overwhelmed eyes when they wake up because the light feels too bright. I happen ...
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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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1answer
100 views

Do humans squint more readily at green light?

I know that humans won't squint their eyes even if exposed to dangerous levels of ultraviolet or infrared light because our eyes simply don't have the capability to detect it. Neither do the irises ...
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1answer
2k views

Would the human body react faster to touch or sight

I am currently working on an assignment for my physics class, but I believe my question is biology related. For a two person lab, I am trying to time how long it takes a tennis ball to fall two ...
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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
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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0answers
2k views

Why does vision gradually becomes dimmer in bright setting?

I don't know if this is only happens to me, but if I am in a well lit room and I stare at one point or just look at one area without moving my eyes around my vision in that specific light setting ...
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1answer
52 views

Is it possible to genetically alter human beings to see parts of the infrared? [duplicate]

Most electron transitions take place in the infrared region,The ability to see this part of the electromagnetic spectrum without reliance on sophisticated technology would have tremendous advantages. ...
3
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1answer
219 views

What happens when the congenitally blind brain receives visual input?

If a congenital blind person gets eye sight (either hypothetically, or in the near future due to advancements in technology), will their brain be able to handle that information, or will it become ...
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3answers
10k views

Why can't we feel pain when the eye lid touches the eye ball?

When I press a finger on a closed eye lid it means the eye lid touches eye ball, then I didn't feel any pain. Now I open my eye lid, then I small touch(not press) the eye ball, it gives me pain, why ...
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0answers
681 views

Do blurry images cause eye strain? At what point is an image so blurry the eye stops trying to focus it?

I'm a user experience designer concerned about a new trend of blurring screens when showing a lightbox/dialog box over top (see below). From what I know, blurry images cause the brain to work hard ...
2
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1answer
8k views

How can alcohol cause blindness?

Strong alcoholic beverages (e.g. moonshine) are reported to have caused blindness amongst some people. How exactly can alcohol make someone go blind? Is that because different forms of "rubbing" ...
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0answers
397 views

How fast the human eye can [temporarily] change its color?

I know that human eye can change its color during lifetime because of disease or medication (similar question on Biology.SE). And I know that it may change depending on the lighting. But I saw ...
2
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1answer
549 views

Relaxing Eyes when using Virtual-Reality-Glasses?

Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image or focus on an object as its distance varies (eye focusing). For distant vision, the ciliary ...
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0answers
48 views

Does the change in eye color (melanin concentration) affect the iris pattern?

In cases of acquired heterochromia, is there a quantifiable change in the iris pattern; the clefts , furrows, etc. If yes, what changes are observed? And if no, are there any diseases or acquired ...
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0answers
43 views

Controlling the pursuit path of the human eye

The human eye scans images by panning focus along a certain path. Stork et al. (2002) revealed that there is a feedback process involved in moving ocular focus along a path that produces minimum ...
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1answer
842 views

Does our brain contain an innate function about closing only one eye?

I wasn't sure where to post this, but biology seemed fitting for me. Sorry if I'm wrong. I was wondering why, when we close both our eyes and look at light, it is clear we can see the light even ...
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0answers
54 views

The evolution of poor eyesight: is there weaker selection in modern humans? [duplicate]

Short question: Poor eyesight might have been a major impediment to survival and reproduction in early man (say, 100,000 years ago), but, with the advent of agriculture, major cultural changes, and ...
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1answer
330 views

Why eyes don't get heated while converging sunlight into retina?

It is a common observation that a magnifying glass when used to converge rays of sun to a fine point in paper, the paper burns due to intense heat. Why doesn't this happen in our eyes? Our eyes are ...
3
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1answer
188 views

Do primate RGCs have overlapping receptive fields?

According to this link, http://hubel.med.harvard.edu/book/b10.htm retinal ganglion cells (RGCs) receive input from overlapping receptive fields (RFs). This is also an idea used in convolutional ...
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1answer
2k views

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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0answers
46 views

Why are eye defects so common? [duplicate]

The title says it all, what makes eye defects so common in the world? Whereas defects of any other body part is quite uncommon, I searched online and one of the articles said that 6 out of 10 people ...
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1answer
667 views

Can one eye affect the other eye's low-light adaption?

This previous question addresses how long eyes need to adapt to darkness and reach full contrast. My question is how does one eye affect the "transition" and/or efficacy of this "night vision" of the ...
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3answers
34k views

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' ...
22
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1answer
1k views

Why can't I read everything in my field of view?

When I look at a piece of text, I can see all the text on the paper, no matter where I look, because my field of view covers it all. However, if I stare at a specific word, I cannot read the text a ...
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2answers
3k views

Why can't our eyes smoothly transition from side to side without focusing on a moving object?

Why are we not able to slowly and smoothly look from side to side, or up and down in a single and smooth transition, given that we are able to do this if our eyes are focused on a moving object?
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2answers
1k views

How many mega pixels does the eye have?

What is the number of mega pixels available in the human eye? It seems that newer camera models continuously keep increasing their pixel count. However, they never seem to be capable of reproducing ...