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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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6
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2answers
17k 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. ...
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0answers
119 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 ...
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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
819 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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2answers
274 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 ...
2
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1answer
74 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 ...
4
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1answer
2k 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 ...
0
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2answers
981 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
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1answer
6k 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 ...
4
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2answers
1k 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 10(...
5
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1answer
297 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 ...
2
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0answers
777 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
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1answer
9k 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
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1answer
1k 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
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2answers
2k 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 ...
14
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2answers
9k 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. ...
8
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1answer
249 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) ...
5
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1answer
172 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
42 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 ...
6
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3answers
23k 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?
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2answers
1k 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 ...
5
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1answer
5k 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
1k 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 ...
9
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2answers
7k 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 ?
4
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1answer
16k 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 ...
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1answer
212 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?
10
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1answer
23k views

What's the minimum distance of focus for the lens of a human eye to reach maximum flatness?

According to the Wikipedia article on eye accomodation, the range in which a human eye can focus is from 7 centimetres away up to essentially an infinite distance. Of course, people can't see things ...
11
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5answers
19k views

Why can't ciliary muscles in the human eye relax like other muscles?

I had laser eye surgery a decade ago, but in recent years my eyesight has become significantly myopic. I consulted an ophthalmologist to see if this was eye strain because I work at computers a lot, ...
2
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1answer
329 views

eye myopia power changes with brightness

Is there a condition where myopic power changes with ambient brightness. When I drive in the morning in bright sunlight my power is -4.0; however when I wear the same -4.0 glass in the evening (dusk ...
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1answer
2k views

Amber eye color in Neolithic Africa

Given what we know of the genetics of eye color and their historical distribution, is it possible or at least plausible for a person born in the Horn of Africa during the early Neolithic (ca. 9000 BCE)...
2
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3answers
1k views

What do you see if you look at your own retina with the same eye? (optical feedback)

When you record a video while pointing the viewfinder towards the screen showing a live preview you create optical feedback: video example. An anoalogous effect occurs when you turn your microphone ...
4
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1answer
139 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 ...
4
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1answer
813 views

The arrangement of retinal cells?

The section of retina shows a layered arrangement of the various retinal cells. Starting from the inside (where the light strikes first) is the nerve fibre layer, ganglionic layer, amacrine cell layer,...
2
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1answer
153 views

How Much Longer For The Gene For Blue Eyes?

In the year 1900 roughly 50% of the people in the United States were homozygous for the gene for blue eyes. By 1950 the number had dropped down to 30%. Just now, (2013) barely 12% of the people living ...
3
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1answer
538 views

Why don't we have more cone cells (bigger fovea)?

Background Apart from being able to sense color, cone cells are able to perceive finer detail and more rapid changes in images, because their response times to stimuli are faster than those of rods. ...
10
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2answers
42k views

Is it safe to look at infrared LEDs?

What happens if one looks directly at infrared LEDs? Sometimes I see this kind of LED at night as red dots and I'm also courious about it. I was wondering what would happen if one looks directly to ...
3
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1answer
780 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?
2
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1answer
85 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 (B....
6
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2answers
16k views

Does bright environment strain eyes more than dim?

I'm trying to figure out how to modify my working conditions so that I can program longer without harming my eyes. Because doing so experimentally hasn't given conclusive results so far, I decided to ...
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2answers
1k views

What does ophthalmologist see in your eye?

I always wondered what ophthalmologists see inside someone's eye and what they're looking for. The whole thing is a mystery to me. Are there any photos of what the eye of a patient looks like from the ...
0
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1answer
123 views

Does the eye image interval refresh? [closed]

It's known the human eye takes 24 images per second. But does this refresh? For example after sleeping. Or will it always be the same interval? I talk about when the eye takes the images. So it are ...
1
vote
1answer
185 views

Detecting UV by humans

From my experience humans can detect UV - not by seeing it but by pain in their eyes. Many people (me too) feel pain when looking at UV lamps. When looking at sun through clouds I still can feel pain ...
2
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1answer
2k views

What is the strength of human cornea?

What is the difference of pressure a human eyeball cornea (cornea, lens and other elements separating vitreous body from air) can handle? Or asking differently: what the outside pressure should be to "...
13
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2answers
42k views

Is it possible for two brown-eyed parents to have blue-eyed child?

Here's the (real) 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. Both parents have brown eyes. ...
5
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4answers
754 views

Why do our eyes “wrap” hue from UV to IR?

On the high-wavelength side of things, we see almost-infrared as reddish, with a slight tinge of magenta. On the low side, we see violet fading into the same magenta color. Why is that? You can see ...
0
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1answer
851 views

Why are human eye colours limited?

Related to the question What causes the colors we see in eyes?, I am wondering why human eyes are restricted in colour. Most common eye colours are blue, green and brown. Why not yellow, orange, ...
14
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1answer
244 views

Are there specific conditions that allow humans to see ultraviolet wavelengths

It is fairly common knowledge that the lens in its normal state absorbs ultraviolet (UV) radiation. An interesting notion has come up from time to time in my reading that suggests there are a small ...
2
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1answer
3k views

Difference between 'Orbit' and 'Globe' in eye anatomy?

What's the difference between 'Orbit' and 'Globe' in eye's anatomy. Do they refer to the same ? I encountered this in this text: ... ciliary ganglion, which is approximately 3 mm in size, and ...
5
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3answers
4k views

How can fruit flies and mice share the same gene that says to build an eye if they evolved separately?

I saw a documentary where they inserted the gene of a mouse that basically is the starting "build an eye" command into a fruit fly, and a fruit fly eye grew. My question is, if eyes of different types ...
4
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2answers
717 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.