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Questions tagged [human-eye]

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

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Why we see black colour when we close our eyes

Why is it neccessary that if there is no light then everythimg is black and when we close our eyes we see everthing black usually when we are in black room??
5
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1answer
69 views

Do Colorblind People Have Stronger Sensitivity in Their Other Remaining Cones?

I came across this paper Color defect and color theory. The paper explained about how unilateral color blind (people who color blind only in 1 eye) actually see less bright in their color-blind eye (...
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37 views

Can some colours be processed faster/more accurately than others?

Is the human visual / motor system able to track, and move in response to, objects of certain colours more quickly and reliably than for others? By more reliably, I mean with greater accuracy in ...
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1answer
24 views

Rod and cone photoreceptors are neurons?

i mean the photoreceptors have axon and dendrite and body cell or it is not neuron any more . can we say outer segment of photoreceptor cell is dendrite ? of course these have body cells but i am ...
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1answer
27 views

how much can changing light enter the eye shap what you see? [closed]

Does it change the shape and how objects are seen or does it just stop you from seeing certain things?
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22 views

If human rod cells are damage will night vision help?

This may seem very strange or even dumb. But if a human rod cell are damage can night vision correct like can I then be able to see. I'm guessing if I use night vision it will be the cone cells that ...
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2answers
120 views

Why is 450 nm monochromatic light perceived as blue or violet depending on its intensity?

Trying to do some color matching I purchased a 450 nm laser. I expected monochromatic light of this laser to have similar properties to those of all others I've already played with — 808, 640, 520, ...
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47 views

Can low melatonin levels and/or LED lights cause or exacerbate macular degeneration?

I have two questions that may or may not be interconnected. My first question is: Does melatonin prevent macular degeneration? Could low melatonin levels (caused by blue-rich light exposure in the ...
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20 views

Does the ratio between M and L cone cells vary in one indiviual?

Wikipedia says: The ratio of M and L cones varies greatly among different people with regular vision (e.g. values of 75.8% L with 20.0% M versus 50.6% L with 44.2% M in two male subjects). This ...
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118 views

Could being exposed to excess UV in the arctic lead to a human eye color change? If so, what is the mechanism?

The CBS News article Expedition Antarctica: A father and son's journey to save the planet says (in part): Thirty-two years ago, Robert Swan made history as the first person to walk to both poles. ...
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0answers
34 views

How many different colors can a normal human distinguish? [closed]

I am not talking about asking a person to sit for 10 hours to separate one color. I want to know is the normal person in a normal life. How many different colors can a normal human separate?
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1answer
42 views

Viral susceptiility of Nose and eyes

I read that opening in our face like nose and eyes are one which get us infected with numerous communicable diseases like cold , flu ebola etc. Both these organs have preventive mechanism like nose ...
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1answer
65 views

What parts of the visual system could be responsible for a fixed, monocular scotoma?

Light enters the cornea, crosses the lens, hits the retina. Electric sinal travels from retina through the optic nerve, reaches the chiasma, crosses and makes its way to the visual cortex. My ...
4
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1answer
86 views

How do you check how many cones you have in your eye?

Following my previous question: What color does the other cone in Tetrachromacy correspond to? People with normal color vision posses 3 cones in their eye. But there are some rare cases when people ...
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0answers
260 views

What is the cause behind negative afterimages in our visual system?

Quoting Physiology of Behaviour by Carlson, 2013, The most important cause of negative afterimages is adaptation in the rate of firing of retinal ganglion cells. When ganglion cells are excited or ...
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0answers
112 views

What is the average volume of the human Psychic tear? (“emotional tear”)

My goal is to find out the volume of the average human "emotional tear" (Psychic tear - sadness, happiness), specifically when crying. I found a lot of information about Basal tears (constant ...
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1answer
53 views

Trying to understand reduction of color dimension in colorblind case

I understand that dichromats have one of their cone missing/not functioning. And as for Monochromats, 2 or all of their 3 cones are missing/not functioning. And I read from Wikipedia - Color Blindness ...
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31 views

Are asian eyes better at sun protection?

Today I have visited a very popular tourist place in Tokyo. It was a very sunny weather and there were HUGE crowds of Japanese tourists and I was one of very few Europeans. I have noticed a surprising ...
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1answer
81 views

What color does the other cone in Tetrachromacy correspond to?

Human with normal vision possesses 3 cones, which correspond to blue (S), green (M) and red (L). What about tetrachromacy, where people have 4 cones in their retinae? What is the fourth cone exactly, ...
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485 views

What are the max angles of human eyeball rotation?

How much can our eyeballs rotate towards the nose, away from it, towards the top and bottom?
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31 views

Deuteranopia confusion lines

For people with protanopia (absence of "red" cones), confusion lines look like this (which is quite intuitive for me) Analogous picture for tritanopia (absence of "blue" cones) But picture for ...
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2answers
166 views

Seeing new colours with new photoreceptors

If we developed new "eyes" that could see "non-visible spectrum colours" and connected them to our brains, would our brain be capable of identifying and interpreting those new colours? Is our brain ...
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19 views

Dark adaptation of the human eye - effects on days and weeks timescales

The adaptation behaviour of the human eye is well-studied and well-documented on a timescale of one hour. But what about the really long term behaviour (on timescales of hours-days) when exposed to ...
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44 views

Why do we see black as white with our eyes closed suddenly?

If we look at black lines on a white background and then suddenly close our eyes, why are we able to continue seeing the black lines as white lines? A Google search didnt show research done on this....
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1answer
60 views

Family eye genetics [duplicate]

Both my parents have brown eyes. My older and younger siblings have brown eyes. I have green eyes. Is this genetically possible? Back in 1962, this was questionable and led to family problems, ...
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1answer
67 views

Why do tears fall from our eyes when we ride a bike too fast?

When we ride a bike too fast why do tears fall from our eyes. What is going on biologically and what may the evolutionary story be behind this? This quora Q&A gives a few ideas, none of which ...
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If longer wavelength color is perceived faster by human, what about non-spectral color (black)?

Related to human vision, I read the hypothesis about how longer-wavelength color is perceived faster by human eye than shorter-wavelength color source : A Brief Classification of Colour Illusions. But ...
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1answer
64 views

Does octopus eye presents the equivalent of fovea in primates?

I'm working on a simple computational model of Primate eye: as we know, it presents a central part, the fovea, that is very rich of receptors in comparison with eye periphery. I'm wondering if other ...
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361 views

effect of infrared light to eyes and skin?

Recently some new "head mounted displays" which are wearable devices for augmented and virtual reality for industrial, research and entertainment purposes have added infrared light emitting diodes ...
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1answer
146 views

Visual phototransduction, neurons depolarization when no light: why?

While reading into visual phototransduction I was surprised to learn that photoreceptor cells are actually depolarized when there is NO excitation (no light, i.e. when you see nothing, black) and ...
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1answer
113 views

20/20 vision translated to resolution [closed]

What resolution and or DPI would a TV or VR headset need to be to equal 20/20 vision? and 20/10? With even the 4K TV it does not seem as sharp as my own vision.
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1answer
676 views

For humans, why is red the color of distinction rather than green? [closed]

The human eye is most sensitive to the color green. However, for some reason red is often selected as the color of distinction or alert. For example, in Renaissance times, painters would outline their ...
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1answer
188 views

Are all cone cells connected directly to the brain?

Coming from a computing science background, I noticed that cameras have orders of magnitude fewer wires than pixels. For example, the Raspberry Pi Camera v2 has 8 megapixels, but only 10 wires ...
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1answer
89 views

Why do floaters in the human eye appear to have a squiggly-line, tubular shape?

If you intentionally try not to tune out visual floaters in the eye, you can see them very clearly and they seem to have a squiggly line shape but with a volumous tubular look. Why is this? They ...
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2answers
987 views

Do eye's muscle share the same nerve?

When I try to rotate my eye, both of my eyes will rotate the same amount and in the same direction (obviously). I'm wondering if it is possible to control each eye separately. I've never seen anyone ...
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1answer
50 views

Myopia & the Blur Effect

I know myopia is caused by elongation of the eyeball. When the eye is too long, light entering the eye balls falls in front of the retina instead of on it. However I do not quite understand how this ...
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0answers
76 views

Differences that are too small to see

Consider two identical pieces of paper. Scenario 1: On both something is drawn in black ink. If the difference between the areas covered in black ink is sufficiently small, I cannot see the ...
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1answer
311 views

What is the advantage of the inverted image on the retina?

Recently, I learned that the image of the world which we see actually reaches the retina inverted. This is due to the fact that the retina lies behind the focus of our eyes. I have two questions: ...
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2answers
152 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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2k 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
64 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
271 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
329 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
1k 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
213 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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409 views

How much time human eye needs to focus on an object?

Here's the setup: i ride in a train at 100km/h and watch at the trees out of an 1.5m wide window sitting 2m away from it (so, the window takes only 45° for me). Trees outside are moving, and at ...
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0answers
159 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
738 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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232 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
5k 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 ...