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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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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23 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
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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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3answers
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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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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
101 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

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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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
45 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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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
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
10k views

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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1answer
53 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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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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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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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
98 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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1answer
94 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
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
275 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
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
293 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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2answers
231 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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1answer
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Near point and far point of myopic eye

Suppose a person wears the specs of power -6D, the far point for that person is 16cm. But the near point of normal eye is 25cm. So, is the near point of a person with myopia (having far point less ...
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397 views

Why are there ghost images of objects just out of focus

I have observed an interesting phenomena with my vision lately. I just think I have never reflected over this before but it might always have been this way. I am nearsighted and have no problem with ...
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1answer
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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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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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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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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1answer
2k views

How are the vitreous humour and aqueous humour of the eye, connected?

My question is regarding the biological nature of the separation between the vitreous humour and aqueous humour of the human (or mammal) eye. What connects the two in terms of the passive transport of ...
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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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2answers
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Is it biologically possible for an adult's eye color to change?

Can it be that the adult eye can change color? Specifically my question is about a unilateral color change, such that the color of one eye remains constant, while the other changes color over time. ...
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0answers
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
597 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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6answers
19k views

Why is human vision restricted to 400-700 nm?

Across the electromagnetic spectrum, 400-700 nm is a narrow spectrum of frequencies and focused in the region of short wavelengths. For example, radio waves cover a large range of frequencies ...
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3answers
1k views

How do we know the brain flips images projected on the retina back around?

Why do we turn images upside down again rather than dealing with them directly, still vertically rotated after passing through our lens? I don't see how that would cause any problems, and how we'd ...
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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 ...
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3answers
9k 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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1answer
287 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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1answer
23k views

How the conjunctivitis virus spread just by seeing a person's eye who is infected

Conjunctivitis or 'pink eye'. I have a few questions on conjunctivitis. When I was suffering from conjunctivitis, my doctor advised me to wear sunglasses so that no one else gets infected. I wonder ...
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291 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
75 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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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
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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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
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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2answers
1k views

Do the eyes play any role in producing the visual experiences you have during dreaming?

Sometimes, you remember a vivid picture of a dream that you saw. What is the role of your eye in this experience? Please provide me with the answer that is as simple as possible since I am in Class 10(...