Questions tagged [eyes]

The discussion of the anatomy and evolution of eyes. Consider using the "vision" tag for questions regarding how the brain interprets information from the eyes.

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Why does a non-functional retinoblastoma protein cause tumours in the cells of the retina specifically?

I know that the name of the protein itself is the retinoblastoma protein - but that's only because the result of a pathogenic variant is retinoblastoma. I'm trying to kind of reverse engineer the name ...
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1 answer
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When do retinal cells stop differentiating? [closed]

I am having a hard time recalling where I had heard this, but I do recall someone saying (perhaps in a video) that cells in the retina divide very rapidly during infancy due to ongoing development of ...
2 votes
1 answer
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Why does there have to be two muscles to control the size of the pupil?

In dim light, the circular muscles relax and radial muscles contract to allow more light to enter the eye, and vice versa in bright light. Why is there the need to have two muscles when probably the ...
-1 votes
1 answer
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How does the brain activate retinal cones in darkness?

The activation of retinal cones by light is how vision is formed; yet there are other methods, such as mechanical one, for activating light, such as pressure photopsia/phosphenes. This occurs when ...
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1 answer
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Image sensitivity of eyes and peripheral vision

I have bad eyes and need glasses. However I have noticed when it is dark, I am able to see contrasting colours a lot better in the corner of my eyes, than in the center, e.g a mark on my wall I can't ...
0 votes
1 answer
54 views

Is 50Hz noticably worse for eyes than 60Hz on a 4K monitor?

I was told in ux.stackexchange that this question is better suited for biology.stackexchange, so, here we go ;). I have a 50Hz 4k monitor (28 inch and using 1920x1080 scaling - so, the text is super ...
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Is the nervous message sent by an eyelash being flexed sent all the way to the brain?

Since the reflex to close the eyelid once an eyelash is touched seems very fast, does the signal from the neuron detecting the touching travel all the way to the brain, get processed then back to the ...
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4 votes
1 answer
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Allometry of vision, can mice see their own fingers?

Looking around, I've found a lot of research on the allometry of visual acuity and vision at a distance, but not so much on vision close-up. As I understand it, the "near point" of vision is ...
1 vote
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Why are we more sensitive to green light when 65% of our cone cells are red cone cells?

I read, "human eyes are most sensitive in 555nm which is green. Human eyes are more sensitive to green than to red, and in low-light conditions even more to cyan than to green." But it doesn'...
-1 votes
1 answer
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Do the activity patterns of an owl species determine their eye colour?

Recently I've been thinking about the colour of owl eyes, and trying to figure out if there is a pattern anywhere between species. I have read for example, that yellow-eyes implies they are day time ...
-4 votes
1 answer
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How fast does eyelid close when eyelash is triggered?

What is the reaction of blinking like when an unexpected piece of wood or something hits an eyelash and then an eyeball? A piece of stone flew into my eyeball when we knocked a wall down, and it hit ...
0 votes
1 answer
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Why do colors clash in your brain?

Wen pairing two or more colors together, some "clash" or cause a effect visually where the two colors meet. To me it appears to be a black line between the colors or shading when in fact ...
5 votes
1 answer
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How much light can pass through the human eyelid?

My sister tells me that at night when the lights in the room are off that she can see the ambient outdoor light from neighboring buildigns and streetlights through her eyelids (i.e., when her eyes are ...
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Why do I see purple stripes when moving a small source of light (flashlight) quickly in a dark room?

I was playing with my phone's flashlight (white) in a dark room, Just moving it around quickly when I noticed that I could see thin stripes of purple in the same shape as my hand moved, they didn't ...
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44 votes
3 answers
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Are humans more adapted to "light mode" or "dark mode"?

I was discussing with a colleague about using dark-mode vs. light mode and remembered an article arguing that humans vision is more adapted to light-mode rather than dark-mode: I know that the trend “...
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2 votes
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Eye Optics/Emmert's law: Where to place scaled copies of an object so they have identical images on the retina?

I read that the center of projection of the human eye is the entrance pupil. So given a light ray which intersects the objects position and the center of the aperture stop, all copies of said object ...
2 votes
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How would our vision be improved if our photoreceptors were not backwards?

I'm curious to how much better human eyesight would be if the nerves from our rods and cones were correctly placed behind the receptors? Are there any Animal Models with correctly placed ...
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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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7 votes
1 answer
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Why exactly are the reflections of sunlight in this dragonfly's eye hexagonal?

I photographed a rather cooperative, large dragonfly today and after getting back to my desk and looking closer at the images I realized that the reflection of the Sun in its eyes produced large ...
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2 answers
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Has anyone yet figured out how sensory signals for eyes and ears are encoded by our organ into electrical signals? [closed]

The most obvious way to give sight to blind and hearing to deaf is to give them a replacement organ for these. In order to do that we would need to understand how our eyes and ears encode sensory ...
0 votes
1 answer
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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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2 votes
1 answer
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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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1 vote
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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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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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What is the very hard sphere inside the eye of many common fish made of and how is it called?

Inside the eye of many common fish, like tuna, scad, snapper, actually probably all fish I have eaten, is a small sphere made of some very tough substance. This sphere is even hard to crush with teeth,...
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Why do the eyes of this cat have different colours when viewed from different angles?

Why do the eyes of this cat have different colours when viewed from different angles? Both of the eyes of this cat appear yellow when looking straight at the camera. However, when the cat looks at ...
4 votes
1 answer
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What happens to eyeball when you push your eye muscles harder? [closed]

I have myopia and I read that the rays of light intersect before the retina. When I can not see clearly I can push somehow my eye muscles and can see a bit clearly. The object gets clear but moves ...
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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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1 answer
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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 ...
0 votes
1 answer
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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? ...
5 votes
1 answer
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Vitamin A Deficiency

I have a quick question regarding Vitamin A deficiency. The photoreceptor molecules in both rods and cones have the same general structure which is retinal which is bound to a protein called opsin ...
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1 vote
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Why do some mammals have incomplete orbits?

I've noticed that a lot of carnivorous/omnivorous mammals (most, if not all the members of carnivora and some ancestral cetaceans), as well as some herbivores (marsupials), have incomplete orbits that ...
-1 votes
1 answer
110 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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4 votes
1 answer
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Non-Salticidae with °oo° Eye Arrangements

Since childhood, I've always thought of the °oo° pattern of four frontmost eyes as iconic for spiders (note: the pattern does not account for any additional eyes or lack thereof further to the sides ...
2 votes
1 answer
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Does my nearsightedness come into play when creating light outlines in the distance?

After looking at a light and closing your eyes, you see an outline of the light. I was curious how my nearsightedness would come into play. I look at a light in the distance without my glasses on and ...
0 votes
2 answers
2k views

How far can a human see at night?

I am not talking about seeing in total darkness, which I understand is not possible. I am looking more about a question how far can a human see during starry night or with half moon/full moon. I tried ...
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3 votes
1 answer
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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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3 votes
1 answer
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(How) do horizontal pupils dialate?

I was looking at mongoose eyes in particular, but my understanding is: Circular (human-like) pupils simply get larger/smaller depending on light levels, no change in "shape" Vertical slit (cat-like) ...
3 votes
1 answer
179 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 ...
1 vote
1 answer
386 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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1 answer
191 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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1 answer
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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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What happens to eyelids when we feel sleepy?

Why is that whenever we feel sleepy, our eyelids start to feel heavier. It is not like we can any time close our eyes and will immediately fall asleep. But, when we feel sleepy our eyelids ...
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0 answers
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How many frames per second do human eyes see? [duplicate]

I observed when a helicopter rotor or fan is spinning the blades blur making it impossible to count the blades, but after a certain speed the blades seem to become visible making it possible to count ...
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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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Does cataract condition cause red film when sun is shining?

Since two years ago I have a red film in my field of vision when the sunlight (or a white spot) is at the border (or even lightly behind) of the vision field, the red color is especially obvious at ...
8 votes
3 answers
672 views

Do animals with their eyes ~180 degrees apart have depth perception?

Lots of animals have their eyes more on the side of their head, like an octopus or a parrot. Are animals with eyes more on the side able to tell the depth of objects at different distances? It seems ...
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Difference in frame rates of normal and peripheral vision

I recently encountered an incident in my laboratory. It was evening and the sunlight entered the lab through a window with exhaust fans. So the ray kept flickering at fixed intervals. I noticed that ...
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Why green light is good for our health? [closed]

I have a knowledge that when you woke up and see green light it increases your sight power. How it does so?
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Would preserving your Eyes from Light keep them healhty?

I read about why eyesight diminishes with age. I am aware of the fact that there are different causes that can affect the quality of image received by our eyes and that being vague would not lead to a ...

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