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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do game animals have poor eyesight?

I have been watching some bow hunting videos on youtube. When hunting with a bow, the hunter needs to get really close to the animal, sometimes less than 10 meters. It seems to me implicitly, and ...
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1answer
36 views

How does an octopus eye react in free fall?

according to Wikipedia: Attached to the brain are two special organs, called statocysts, that allow the octopus to sense the orientation of its body relative to horizontal. An autonomic response ...
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29 views

How fast the human eye can [temporarily] change its color?

I know that human eye can change its color during lifetime because of disease or medication (similar question on Biology.SE). And I know that it may change depending on the lighting. But I saw ...
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1answer
43 views

Relaxing Eyes when using Virtual-Reality-Glasses?

Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image or focus on an object as its distance varies (eye focusing). For distant vision, the ciliary ...
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1answer
49 views

How many people in the world have bad eyesight?

I was watching this ted.ed episode and heard it was around 500,000 but that didn't sound right-- does anyone know?
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2k views

Why do we go blind for a few seconds after switching off the light?

At night, when I switch off the lights, I always seem to go blind for a while. The room becomes pitch black and I am unable to see anything. After a while, however, my vision slowly recovers and I ...
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1answer
89 views

What is the rationale for the complex eye structure? [closed]

The eye is a lens that focuses rays of light from a limited spectrum, after which the the image is turned over to the brain receptors that interpret it (beginning with turning it the right side up ...
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1answer
60 views

Explanation of the ‘cherry red spot' in Tay Sachs disease

In Tay Sachs disease, a hallmark symptom is a cherry red spot in the macula of the eye surrounded by a halo of white. I understand that the ganglion cells, which are higher in numbers around the ...
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1answer
78 views

Does our brain contain an innate function about closing only one eye?

I wasn't sure where to post this, but biology seemed fitting for me. Sorry if I'm wrong. I was wondering why, when we close both our eyes and look at light, it is clear we can see the light even ...
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51 views

Why do I see the world in blue when I open my eyes? [closed]

So I was standing outside, waiting for the train. I was tired so I closed my eyes for a while. Then when I opened them, the world was a lot more blue than it normally is - why is this? I tried it a ...
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7answers
5k views

Why can't we see in low light if staring long enough?

For me it seems reasonable that if I kept my gaze on a fixed point in a room with low light, a progressively brighter and better picture would appear before my eyes, just like a camera can see in the ...
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22 views

Did the number of rods changed from ancient time?

Correct me if I am wrong, but I know that rods work under limited light conditions only. But now we are in a world that always have lights everywhere unlike ancient time when humans had to deal with ...
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1answer
29 views

A limit to birds affinity for high vantage points [closed]

Birds seem to have a natural affinity for high vantage points, including power wires, the tops of trees, and the sides and tops of buildings. However I presume the top of the Burj Khalifa is not ...
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1answer
140 views

Why do we blink instead of winking each eye independently?

Question Why do we blink both eyes at the same time rather than winking each eye as needed? Why would winking independently be better? The benefit would be a minor improvement whereby a person ...
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0answers
10 views

What causes the color boundary in irises?

The iris shown in the image below has a radial color boundary. The part closest to the pupil is a brownish color while the part farther from the pupil is an aqua color. What causes this to develop? Is ...
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0answers
39 views

Why are eye defects so common? [duplicate]

The title says it all, what makes eye defects so common in the world? Whereas defects of any other body part is quite uncommon, I searched online and one of the articles said that 6 out of 10 people ...
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0answers
66 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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1answer
151 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' ...
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1answer
547 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?
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83 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 ...
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1answer
95 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" ...
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0answers
17 views

Can a computer display work as a daylight lamp?

During winter time I often see advertisements for daylight lamps which are supposed to compensate for the lack of daylight in a winter season. The specs of such a daylight lap seems to be an LED ...
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1answer
130 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 ...
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1answer
75 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 ...
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2answers
242 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 to detect flowers that bare nectar, or the urine trails of prey. But what I don't understand is ...
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2answers
437 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 ...
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0answers
33 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 ...
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22 views

What is the permeability of proteins across the hyaloid membrane of vitreous to retina?

Does anyone know of any experimental work to test the permeability of the hyaloid membrane between the vitreous humour of the eye to the retina to proteins? Currently the largest molecule I can find ...
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1answer
102 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 ...
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1answer
407 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 ...
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0answers
223 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 ...
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0answers
7 views

How do drugs (or other molecules) move between the vitreous humour and aqueous humour of the eye? [duplicate]

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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1answer
225 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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1answer
306 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., ...
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1answer
173 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 ...
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0answers
106 views

Random small after-images of things not really there [closed]

I am 44 years old and have noticed that I often get small blotch afterimages that last for about 5-10 mins. Normally, everybody gets these when they look at a bright light. I seem to get these every ...
3
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1answer
57 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 ...
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1answer
39 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 ...
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0answers
29 views

Undistorting peripheral vision

I am interested in a procedure which can be applied to an image (or video) which is situated in my peripheral vision, and will result in an undistorted copy being presented to my brain. I do not know ...
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1answer
231 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 ?
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1k 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: ...
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1answer
55 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 ...
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1answer
100 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?
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2answers
2k 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 ...
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1answer
1k 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 ...
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2answers
2k 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 ...
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0answers
87 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 ...
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1answer
65 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 ...
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2answers
210 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 ...
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1answer
693 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.