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Questions tagged [human-eye]

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

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25 views

Why do we see a differnet color when we see two colors changing rapidly?

When you see two alternating colors on a screen with high frequency (60Hz), our eyes see a totally different color! I would like to understand why this phenomenon happens? Is this something related ...
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12 views

What standard procedure taken to measure eye far point and near point?

I've read from various link that to measure power/dioptre of eye glasses lens, we need to put far point into equation for nearsightedness and near point for farsightedness. The problem is I cant ...
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2answers
48 views

Why do our eyes not have interference from other sources of light?

When one looks forward at a glass of wine, one is seeing it via the reflection of light off of the glass. But if you have a person to your right, looking to the left side of you (still in front of ...
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24 views

Why does brain invert the image formed on retina? [duplicate]

I have been studying about the human eye and it's working in school for some time. I came across something. I have been taught that the image formed on the retina of the eye by the lens is inverted ...
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1answer
47 views

Comparion between machine vision & human vision

I hope this is the correct Stackexchange to ask this question. I am trying to know : What is the current status of knowledge regarding human vision and pattern recognition. More specifically, How ...
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1answer
59 views

Jungle blindness?

Can people who live in green scenic areas like a jungle be more exposed to green light causing them to not be able to perceive green light as well as someone who may live in a desert void of color? ...
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1answer
48 views

How do cone cells underneath capillaries receive light?

Came across this image of retina's cross section: 1) How do the cone cells directly underneath the blood vessel ('demarcated in the picture') receive a spectrally correct representation of the ...
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41 views

Is there any biological basis for the commonplace “eyes popping out” cartoon?

We might all be familiar with images like these below: I see this clearly "works" in a cartoon context. It makes a point. That "eyeballs" hanging outside belong to the individual and can be shown ...
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1answer
106 views

Can Green color give Rest to Eyes?

Is it correct that Green color gives rest to our eyes compare to other colors?
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1answer
47 views

What is violet color?

We have 3 color receptors in our eye, so assuming the above picture is precise we are checking for 3 wavelengths: 450nm, 540nm and 700nm. Pink for example has an RGB value of R (700nm): 1 G (540nm): ...
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1answer
90 views

If one of eyes is blind, can that eye still feel pain?

I was wondering this when I touched my bare eye (my eye was open) and since I'm not blind I was wondering if an eye is blind, can it still feel pain?
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1answer
51 views

Do nerves work as I think they work and what does that mean for our senses?

Let me start off with a couple of metaphors. In the third Lord of the Rings film, a signal for help is sent from Minas Tirith to Gondor, using a chain of beacons. When the keepers of one of these ...
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1answer
54 views

Why has the human eye evolved to become sensitive only to the visible light? [duplicate]

The human eye has evolved to become sensitive only to visible part of the electromagnetic spectrum. Why? Why is infrared vision disfavoured for us by evolution but not for some other animals? I am not ...
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45 views

How is the eye damaged by computer screens?

Eyes are damaged by persistent use of computer screens. On giving it some thought, it felt quite magical that your eyes are damaged simply by looking at something. I googled where there were articles ...
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21 views

What is the average eye sight for humans? How bad is one's eyesight if you are1 or 2 SD below average?

What is the average eye sight for humans? How bad is one's eyesight if you are 1, 2 or 3 SD below average? I googled but it was hard to find good search terms.
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40 views

Double vision from one eye? [closed]

I have recently experienced getting double vision out of one eye. When I cover my dominant right eye the double vision corrects and become a solid image? I am not asking if it is possible to get ...
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1answer
280 views

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??
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1answer
95 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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1answer
66 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
300 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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37 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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2answers
235 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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0answers
91 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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0answers
24 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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172 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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42 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
57 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
130 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
294 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
300 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
76 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 ...
6
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1answer
122 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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1answer
1k 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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1answer
100 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
447 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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1answer
66 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
70 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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67 views

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
123 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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1answer
386 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
205 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.
3
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1answer
896 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
333 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
101 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
1k 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
54 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
77 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
584 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
204 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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0answers
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, ...