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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3answers
906 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) ...
4
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1answer
49 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 ...
3
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1answer
37 views

Why do small fonts strain the eyes?

I understand that too much close reading will strain the ciliary muscles of the eyes. But what about small fonts? The contraction of the ciliary muscles is dependent on the distance not font size. In ...
5
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1answer
122 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?
4
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2answers
69 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 ...
2
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1answer
42 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 ...
3
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1answer
86 views

How common is complete heterochromia?

How common is complete heterochromia? (One iris is a different color from the other) Are there any statistics available for this? If no, why not?
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0answers
7 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. This paper gives values for some flies. Is there any database maintained for these values? ...
3
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2answers
95 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 ...
6
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1answer
111 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. ...
1
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1answer
39 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 ...
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0answers
26 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 ...
10
votes
1answer
308 views

What are the “stars” we see after a bump on the head?

Sorry if this might appear funny. When I close my eyes for a longer time, and suddenly open it, I see some twinkling white small circles, and when i concentrate on anyone of them it disappears, as ...
7
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6answers
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?
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1answer
20 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 ...
4
votes
2answers
100 views

Does myopia tend to decrease the risk for later hyperopia?

It seems like being nearsighted for much of your life due to elongated eyes would make it easier in general to focus on near objects rather than far since the lens would not have to change much. Since ...
4
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1answer
100 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 ...
5
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1answer
69 views

Can the negative afterimage appear only if there is light or is it possible in darkness?

Reading the following paragraph: After staring at the red and blue shamrock, you saw a green and yellow afterimage. Opponent-process theory proposes that as you stared at the red and blue ...
3
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0answers
24 views

What determines the thickness of Cornea?

In eye-operations such as Lasik and Femto, the thickness of cornea is key decision factor whether the operation is feasible. A normal thickness is between 500-600 µm. Cornea consists of a very special ...
2
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1answer
65 views

How do animals handle light refraction in different media?

For a human, when diving underwater, everything is blurry because of the water's different refractive index compared to that of air, which we are accustomed to. How do animals, like turtles, seals or ...
9
votes
2answers
1k views

How do we know the presence of light when our eyes are closed?

Last night I laid on my bed and tried to go to sleep with the light off. I closed my eyes (but hadn't gone to sleep). My younger brother touched the wireless mouse (which had laser) for the laptop. ...
0
votes
2answers
48 views

How come degraded eyesight still holds with a mirror? [closed]

When you use a mirror to look at something, you can position it at an angle arbitrary to your face and still look at an object far away. My question is, for degraded eyesight, how come the picture is ...
3
votes
1answer
72 views

Does human eye lens have a magnification of its own?

I have always wondered if the lens in our eyes have any sort of magnification by default. And if yes, if we're actually seeing everything around us bigger/smaller than what they actually are! Has any ...
5
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2answers
1k views

Do octopuses have better eyes than humans?

I've read that unlike humans, octopuses have eyes "designed" the "right way", i.e. with the nerve fibers behind the retina, thus getting rid of the blind spot we humans have as well as theoretically ...
9
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2answers
12k views

Is it possible for a brown eyed parent to have blue eyed child?

Here's the story: A young man has stunning blue eyes. On his mother's side are lots of instances of blue eyes, but on his father's side is no history of blue eyes. When he was born with these bright ...
64
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5answers
2k views

Is there a reason why human eyesight and plants make use of the same wavelength of light?

The accepted range for the wavelengths of light that the human eye can detect is roughly between 400nm and 700nm. Is it a co-incidence that these wavelengths are identical to those in the ...
4
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2answers
53 views

What animal's lower eye lid moves to upper one when closing eyes?

I know cock's lower eye lids moves to meet the upper one when it closes its eye. What other animals does this? BTW, "cock-eyed" can mean upside down, I think.
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1answer
151 views

Are these claims of “revolutionising” understanding of human vision and hearing valid?

I've started a hobby machine vision project (and posted some questions to this end on other SE sites) and on a side track, also been looking at relevant research in human vision (and partly, hearing). ...
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1answer
72 views

Are human eyes equally sensitive to AC, and DC lamps?

Definitely anecdotal. This friend is hypermetropic, and uses reading glasses. He doesn't have major issues facing car headlights, or using a torch (the one with a bulb - not a white LED). Yet place ...
2
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0answers
27 views

What does salt do to styes?

Styes formed in the eyes are cured by dabbing at them with lukewarm water(I saw this being done many a times as a home remedy.) At times, common salt is added to the water before dabbing. My mother ...
7
votes
1answer
911 views

Dark veil when getting up too fast

I was asking myself this weird question. When you get up or stand up too fast, sometimes, you see something like a dark veil, and you aren't able to see anything distinctly for 2 or 3 seconds, then ...
4
votes
1answer
53 views

Are common eye defects inherited?

If one parent is nearsighted and the other is farsighted. One parent developed nearsightedness later in life, while the other was born farsighted and they are both the first ones in their family to ...
4
votes
1answer
60 views

HSL Lightness vs Eye sensitivity

In a monochromatic spectrum, is the human eye equally able to distinguish between lighter colors just as it is in distinguishing between darker colors? I mean is there really a linear relationship ...
5
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1answer
111 views

Which part of human eyes is getting tired?

It's a thing of common sense that if you read, drive or look at computer screen for too long your eyes will get tired. They burn, itch and try to close all the time. But I was wondering which part(s) ...
2
votes
2answers
101 views

Can someone who is color blind recover color vision by surgical means?

I am currently studying color blindness, and there is no medicine that can help it. Is it possible nonetheless for someone who is color blind to have their eyes restored to normal color vision by ...
2
votes
1answer
42 views

What is the focus distance of a 3D screen?

I've thought long and hard about wheter this is the appropriate section for this question, because I guess it's kind of an interdisciplinary subject. My understanding of stereopsis (please, correct ...
0
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0answers
28 views

What exactly are “floaters”? [duplicate]

i was reading this artical after hearing about it on the news, while reading i saw the term "floaters" which made me remember of a recent Family Guy Episode in which there is a joke about them in ...
2
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2answers
197 views

How do bats distinguish between day and night?

How do bats distinguish between day and night? Do they hunt at night - if yes, how they know that? Are they afraid of sunlight?
7
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3answers
972 views

What is the difference between a circular and a cat's-eye pupil?

I've been to local zoo the other day and one lizard caught my attention: its pupils are circular, which, I thought, is not usual for reptiles. Turns out it is, but now I can't find any explanation on ...
0
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0answers
12 views

Where is cartilage in the developing eye in embryo?

I am not completely sure where there are cartilage in the eye. I think the developing vitreous body (very light coloured) does not have cartilage. You can assume the eye is during the weeks 11-13 of ...
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3answers
522 views

Why do our eyes close when we sleep?

Why do our eyes close when we sleep? Is it to relax our eye muscles? How can it be explained from an evolutionary point of view?
6
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1answer
308 views

Why do people sleep with their eyes open?

It's a fact that some people sleep with their eyes open, but why does that happen? Is it normal behavior, not a symptom of any sort of disorder? Are there any (dis)advantages to sleeping with eyes ...
9
votes
2answers
26k views

Which shades/hues of color are easiest to distinguish for humans?

I'm trying to represent data graphically and am using a variation of hue/lightness to distinguish one data point from the next. I would like to use a color that would allow me to convey most ...
2
votes
1answer
31 views

Function of an VEGF inhibitor in the treatment of macular degeneration

I'm working on a short presentation of treatments of macular degeneration for a biomedical optics seminar on macular degeneration. Since I don't have any relevant medical or biological background ...
3
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1answer
132 views

Why basement membrane thickens in diabetes mellitus?

Untreated diabetes mellitus may lead to blindness and kidney failure because the basement membrane of small blood vessels in these organs thickens due to increased production of collagen and laminin. ...
7
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1answer
550 views

Crusty eyes in the morning

Often, after waking up from a night's sleep hard, flaky, pale yellow crystals are deposited around the eyelids (which easily wash off with water). What are these? Why are they yellow? What are they ...
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1answer
53 views

What happens when we dream?

When a human dreams does the brain activate the cones and rods in the eyes creating the images we see in dreams?
5
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3answers
251 views

Does our eyeball increase in size as we grow?

Does the size of the eye increase as we develop from the stage the complete eye first forms to infancy and then to adulthood ?
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1answer
524 views

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 ...
6
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1answer
5k views

Why can cats interpret things on a monitor/tv, but dogs cannot?

E.g. you can see a lot of videos where cats are smashing some mouse or spider on an ipad, but I have never seen it with a dog. I have a dog myself and I know that he sometimes responds to the sounds ...