Questions tagged [human-eye]

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

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31 views

The position of the macula in comparison to the blind spot

Which is located in a higher postion? Macula or blind spot?
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1answer
42 views

How much percent of image does our eyes focus at any instant?

I learned in highschool that even thought we have a wide view, we only observe a tiny fraction of that view through our eyes. So at any instant we are not really looking at all the objects infront of ...
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1answer
56 views

Why does our visible range not include infrared or UV radiation? [duplicate]

As the radiation peak of the sun is in the UV region and since at around room temperature materials emit radiation at IR, I wonder why our eyes are not capable of using these wavelengths. I guess ...
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35 views

Why do we get tunnel vision during fight or flight response?

I have a question regarding tunnel vision during the fight or flight response. I believe that during fight or flight high levels of adrenaline are released which causes the pupils to dilate allowing ...
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17 views

Why does Cyan appear bluish rather than greenish, when the phototopic eye sensitivity is highest in green (and Cyan contains blue and green equally)?

Cyan contains blue and green equally. Phototopic eye sensitivity is highest in green. Why, then, does Cyan appear bluish to most of us, rather than greenish?
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15 views

Can the eye determine which type of defocus is presented to it?

I have a question regarding myopic and hyperopic defocus. My question is, is the eye able to determine which type of defocus is presented to it and if so what mechanisms allow it to distinguish ...
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2answers
91 views

What are the physiological effects of retinal exposure to 380–400nm light?

There are two categories of sunglasses: UV380 sunglasses block all light with wavelength 380nm or lower, while UV400 sunglasses block all light with wavelength 400nm or lower. This made me wonder, ...
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1answer
106 views

Can the human eye axial length decrease?

I just have a quick question regarding the axial length of the eyeball. I understand that the axial length of the eyeball grows up until your around 20 years of age which is why hypermetropia ...
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49 views

How does sleep prevent our eyes from drying out?

If we don't sleep for about 16 hours, our eyes start to get dry, and no amount of eye drops helps. You use eye drops and then you're dry 10 minutes later. However, after you've slept for 8 hours, your ...
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1answer
37 views

What causes eye strain when viewing any display?

Few everyday experiences: Staring at the physical paper (or any other sight in nature) doesn't cause eye strain. Staring at the LCD screen causes eye strain. Some of the differences in properties I ...
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1answer
52 views

What is the smallest visual unit perceptible to the human eye, like a pixel? (esp. in visual static)

If you close your eyes, you can often see visual static, where individual pixel-like things are much more visible than with the more smooth, crisp images one gets with open eyes. This led me to wonder ...
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35 views

Does the human eye’s field of view shrink when focusing on far away objects?

It seems like the lenses of the eye is like a fisheye lens that flattens out to a normal lens when looking at far away objects. Does that also mean that the field of view gets narrowed down as well? ...
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43 views

Do pinhole glasses help reduce eye strain?

I've noticed that I can read about 10x longer at screens and books without my eyes tiring using the "pinhole trick" - where you curl your fingers and look through the hole (great explanation here ...
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129 views

Why did we lose our fourth type of cone cell (in the eye)?

Most species of birds, reptiles and fish have four types of cone cells in their retina, thus they have four independent channels for conveying color information. They are: short-wave (S) cones: ...
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1answer
107 views

Is the human iris concave or convex?

Most drawing and 3D modeling tutorials show the iris to be concave. But all the diagrams I Googled show the iris is at best flat, otherwise even a little convex (discounting the optical distortion in ...
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1answer
88 views

Is the backward positioning of photoreceptors bad design?

(Several questions have been asked about this topic but most are quite old and there has been at least one study since then that has attempted to answer this in a new way) Since photoreceptors are ...
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54 views

Does the human eye see things at twice the distance in a mirror?

If I'm standing 3ft away from a mirror and looking at something in it that is behind me but 5ft away from the mirror, do my eyes see that object as 3ft? Or 8?
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1answer
70 views

Does the Human Eye White Balance?

OK, this may be a stupid question…but here goes. Does the human eye “white balance” itself? I assume that each human perceives colour slightly differently according to the peculiarities of their own ...
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1answer
102 views

How are the images of both eyes combined to form one image?

When you see an object by one eye, ex.right eye, you see it from the right direction and the opposite if you see it by your left eye, but when you open both eyes, the image appears somehow centric in ...
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102 views

Is it possible to simulate tetrachromatic vision in a trichromat?

Suppose we are able to stimulate the whole matrix of cones of a human retina, targeting each cone individually¹. Normally we would project an image in the LMS color space onto the cones, in such a way ...
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2answers
53 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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42 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
57 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
77 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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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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200 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
228 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
95 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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97 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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59 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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67 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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48 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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22 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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41 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
687 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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112 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
114 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
796 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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38 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
376 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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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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27 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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223 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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59 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
159 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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1answer
478 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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550 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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108 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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145 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, ...