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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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 ...
theforestecologist's user avatar
25 votes
3 answers
111k views

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' ...
theforestecologist's user avatar
4 votes
0 answers
25k views

Are there animals / mammals which only have one eye?

Do all animals (of a certain size and not thinking about worms) have the possibility to perceive depth? Do all mammals have at least two eyes? Are there mammals with more than two eyes?
Martin Thoma's user avatar
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2 votes
2 answers
1k views

Can the retina emit light?

The retina is light sensor, which converts light to an electrical signal. LEDs can both emit and receive light. Similarly, is it possible to apply electricity to retina to generate light? Simply put,...
Thaina's user avatar
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-1 votes
1 answer
943 views

Do any dogs have blue iris - not just sclera? [closed]

I was looking in to the question of whether any dogs in fact have "blue eyes"... A quick search gives plenty of information on and images of dogs with blue sclera and black iris. Every "blue-eyed" ...
Fattie's user avatar
  • 11
7 votes
1 answer
3k views

What is the function of the human eye white?

If you have a look at the eyes of most animals, you never see the white part unless the eyes are averted. In contrast, humans always have the whites visible because the iris is quite small. The only ...
Lisa's user avatar
  • 73
3 votes
1 answer
450 views

When you blow through your nose while holding it closed to "depop" you ears, why do you sometimes feel it in your eyes?

After your ears have "popped", for example on a flight, I heard you are supposed to hold your nostrils closed and blow through your nose to readjust the pressure to the normal level. Why do you ...
Jack Graveney's user avatar
4 votes
2 answers
5k views

How can some animals see ultraviolet or infrared light?

I know that some animals like birds, bees, and fish can see ultraviolet and infrared light. Whether it is to detect flowers that bear nectar, or the urine trails of prey. But what I don't understand ...
AyyAyyRon97's user avatar
5 votes
1 answer
12k views

Why do snakes not have eyelids?

Why is it that snakes do not have eyelids? Is it due to that fact that they are not as evolved as we humans and other organisms that have eye lids, or is there any other significance behind it if any?...
Aneesh's user avatar
  • 53
2 votes
0 answers
60 views

Can a stationary eye with a moving pupil exist? [closed]

I am making a sci-fi web-comic set on an alien world and I thought up an idea for an eye that works much like an eye from a mammal, but instead of moving the whole eye, only the pupil moves. This idea ...
Jesse's user avatar
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0 votes
1 answer
525 views

What is the surface area of the vitreous humour in contact with aqueous humour?

This is a question regarding the anatomy of the human eye, however for my purposes medium sized mammals should do. I am interested in estimating the surface area of the hyaloid membrane of the ...
Freeman's user avatar
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11 votes
1 answer
2k views

Does your iris color have an effect on your vision?

I've always wondered if having different iris colors, (eye colors) may have any advantages or disadvantages on ones vision. Specifically regarding the effects of light. Personally, I have troubles ...
AstroMax's user avatar
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1 vote
0 answers
623 views

Would a VR headset exacerbate myopia or could it be used to retrain the eyes?

I've learned that there are two primary hypotheses to explain myopia: not enough use of distance vision or not enough sunlight If the distance between an eye and what it's focusing on is the primary ...
MetaSean's user avatar
  • 119
4 votes
1 answer
3k 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 ...
Freeman's user avatar
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5 votes
1 answer
866 views

Why did Opabinia have 5 eyes?

I recently read about a fossil called Opabinia. What intrigues me is that it had five eyes. I was under the impression that most features, such as eyes, ears and legs are always even-numbered, i.e., 2,...
Mnementh's user avatar
  • 183
2 votes
1 answer
2k views

Does "squinting" make you concentrate better on a logic test?

We have all had those moments of intense concentration on some tough exam, perhaps a college test or whatever... Why is it that when we squint, it feels like we can focus and concentrate better on ...
Neri Rocha's user avatar
3 votes
1 answer
152 views

How does tearing work?

I found the question about tear gas very interesting. Shigeta says there that crying helps the cells of the eye to wash themselves clear of the toxic components in the tear gas. Does non-emotional ...
Probably's user avatar
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0 votes
1 answer
774 views

What happens in lasik operation?

First of all,I am very bad at biology. So please bear if it sounds elementary. I heard about lasik operation for reshaping cornea. Assume the patient is suffering from myopia implying lens is ...
Abhinav Ashok's user avatar
1 vote
1 answer
4k views

Why does our eyes got wet when we feel emotional or whenever we are hurt? [duplicate]

I was thinking like whenever when we feel emotional or whenever we got hurt we got tears from our eyes but why is that happen ? Why our eyes got wet ?
Shashank's user avatar
  • 577
17 votes
1 answer
16k views

What portion of the electromagnetic spectrum do cats see?

I have seen numerous articles and various information about how cats and dogs see into the ultraviolet spectrum with interesting artistic renderings such as this: http://www.livescience.com/40459-...
ylluminate's user avatar
4 votes
1 answer
8k views

Wearing sunglasses during a solar eclipse [closed]

Note: I had asked this on Physics, but it is off-topic there due to being about safety. On the BBC's guide to eclipse-watching, Dr Lucie Green says: Watching an eclipse with normal sunglasses ...
binaryfunt's user avatar
1 vote
1 answer
1k views

Is it safe to look indirectly at the Sun?

I.e., is exposure of sunlight onto the peripheral vision less damaging than exposure onto the fovea?
binaryfunt's user avatar
1 vote
2 answers
25k views

Why is my peripheral vision better for seeing in the dark? [duplicate]

I often walk around my house at night with the lights turned off and one night I noticed that looking straight at an object with very little light available made the object disappear from sight but if ...
Eric's user avatar
  • 117
11 votes
1 answer
9k views

Why can I see a light flicker when it's in my peripheral vision?

When I'm looking at an old CRT monitor or a worn fluorescent lamp, but not directly in the center of my gaze, the light from it seems to flicker. When I focus my gaze onto the monitor or lamp, the ...
Marc Dingena's user avatar
19 votes
2 answers
6k views

How do birds deal with their eyes drying out at high speeds?

My eyes tear up when cycling at 15 mph, which is nothing compared to bird airspeeds. Do birds continuously produce lots of tears and blink a lot, or do the eyes self-moisturize from the inside ...
SuperElectric's user avatar
0 votes
0 answers
872 views

Why does a human's field of view narrow when moving faster?

A relative of mine is a driving instructor and he regularly likes to bring up that the field of view narrows noticeably when driving at higher speeds. Is this true, why is this so and does this apply ...
Etheryte's user avatar
  • 296
1 vote
1 answer
170 views

What is the minimum functional biological light sensor? [closed]

As a follow up to this question regarding the evolution of the eye, it was suggested that primitive eyes only needed to evolve a light sensor and could perhaps use the existing biochemical cascade ...
r2d2's user avatar
  • 186
3 votes
2 answers
315 views

What is the minimum eye?

What is the minimum eye which confers some evolutionary advantage? By minimum I mean anything less than this has no advantage whatsoever and therefore is not favored by natural selection. By eye, I ...
r2d2's user avatar
  • 186
1 vote
1 answer
8k views

Are the irises an exact match in a human's set of eyes?

Are the irises an exact match in a human's set of eyes? Assuming the eyes are healthy with 20/20 vision.
ZZZ's user avatar
  • 816
2 votes
0 answers
953 views

Sensitivity of eyes to flashing lights

My eyes are very sensitive to flashing lights - for example I'm always the first person to notice that a fluorescent tube is about to fail because I see it flickering when other people can't. When I'...
Lefty's user avatar
  • 351
2 votes
0 answers
243 views

White/Gold vs Blue/Black dress

So I'm sure you've all seen the dress photo where people see the dress as either White and Gold or Blue and Black. It has essentially 'split' the internet because some people see the dress and they ...
JamesENL's user avatar
  • 129
2 votes
1 answer
5k views

How come all my family have brown eyes and I have blue eyes?

My whole family tree up to my grandparents have brown eyes, I have blue eyes, how come? I don't know if it matters but I have not received enough oxygen at birth, doctors said it's probably the ...
mountSin's user avatar
17 votes
3 answers
5k views

Superhuman eyesight

My ten year old son was reading car number plates that were too fast, too far away and at the wrong angle for any of us to read or even believe that it was possible for him to read. We thought he was ...
Claire's user avatar
  • 181
13 votes
1 answer
18k 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 ...
hello_there_andy's user avatar
2 votes
1 answer
259 views

Why do eyes water in response to particular emotions?

It is common for people to experience very moving situations (sad movies, etc) and have a physical reaction to it (such as crying). I am curious about how emotions can physically lead to the act of ...
blackcornail's user avatar
6 votes
1 answer
6k views

Why do we get 'bags under our eyes'?

Why do these circles form around the eyes if somebody is tired? And why does fatigue express itself around the eyes this way? Can I get eye bags very quickly in another way? http://www.todayifoundout....
blackcornail's user avatar
1 vote
0 answers
185 views

Eye strain using 3D screens

I don't know if this is a physics or a biology question but this might be better orientated around the element of how the human eye works in a 3D visual situation than physics. Given the rise of 3D ...
Dave's user avatar
  • 111
16 votes
1 answer
4k views

Why do dog's eyes glow green on a photo?

Taking my current profile picture as a prominent example: This photo has been taken with flash. As I gather, this is the same effect that makes a human's eyes glow red on photos, namely the ...
Vogel612's user avatar
  • 263
7 votes
3 answers
1k views

What is the science behind the inaccurate perception of colors?

If I go into a green room (all walls are semitransparent and green) and spend some time - around 10+ min - in there, when I come out all my eyes see is white as pink. I see no (or very few other) ...
Tab's user avatar
  • 173
5 votes
1 answer
13k views

Why are irises unique?

I heard that irises are different and unique for every person. According this link, probability of two irises having identical pattern is 1 in 10 to the 78th power. That's how iris scanners identify ...
TanMath's user avatar
  • 3,079
10 votes
1 answer
16k views

How does the cornea breathe during sleep?

The cornea is not supplied with blood vessels and so exchanges gases directly with the atmosphere. So how does it breathe during sleep when our eyes are closed?
biogirl's user avatar
  • 8,599
10 votes
2 answers
6k views

How does the eye know whether to focus further out or nearer in order to bring a blurry object into focus?

If the eye sees an object, but the object is out of focus, the eye could be focusing too near or too far. How does the eye (or the brain) distinguish one situation from the other? How does it know ...
user85543's user avatar
  • 103
1 vote
1 answer
338 views

Flicker fusion threshold for insect eyes

I searched on bio-numbers for flicker-fusion threshold of insect eyes in general and for flies in particular. Ruck, 1961 gives values for some flies. Is there any database maintained for these values? ...
Dilawar's user avatar
  • 427
5 votes
2 answers
3k views

How do gory images lead to nausea?

How do gory images lead to nausea? Yesterday my friend visited shock sites (a website). He said that he got nauseous sensation within seconds after viewing the gory images. However, I don't ...
user avatar
5 votes
2 answers
18k views

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. ...
borenx's user avatar
  • 51
1 vote
0 answers
123 views

How to compare a camera and an eye

How could I compare what a normal eye can see to a camera lens? I just went through a very comprehensive article @ CambridgeInColor, but I'm still not really clear. When I take a picture with a SLR ...
Steven Van Ingelgem's user avatar
10 votes
6 answers
3k views

What is the use of eye banks, if eyeball transplants do not exist at present?

Corneas are donated and transplanted, but not the eyeball. I don't understand. What is the purpose of donating a cornea without an eyeball to a blind person?
user avatar
1 vote
1 answer
1k views

Does pupil size affect image focus in persons with no lens?

If an individual has no lens like Claude Monet (who had them removed). They should be able to still focus the images they see in a well light area if they shrink their pupils to a very small size ...
user46725's user avatar
  • 173
1 vote
2 answers
362 views

Can we directly stimulate M cones in retina with current technology?

I wonder if we could try to see imaginary "supergreen" color by directly stimulating M cones. For this I suppose we'd need: Non-destructively scan specific human's retina to locate exact positions of ...
Ruslan's user avatar
  • 395
2 votes
1 answer
86 views

Like size and colour constancy, why does the brain not maintain focus constancy?

I have progressive myopia. I grew up with perfectly normal eyes but slowly started getting myopic. The thing is, my brain knows (or should know) what the world looks like -- it knows that far away ...
varshmallow's user avatar