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.

learn more… | top users | synonyms

3
votes
1answer
782 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 ...
2
votes
1answer
2k 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, ...
7
votes
2answers
270 views

What is the eye muscle status when you stare at distant view through a glass wall?

The book said when you look at object close to you, the eye muscles contract and vice versa. I wonder what will be the status of the eye muscles when I stare at distance view (such as a mountain) ...
2
votes
1answer
151 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. ...
2
votes
1answer
72 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 ...
5
votes
2answers
606 views

Why does squinting allow you to see objects more clearly?

How does squinting alllow one to see clearer pictures? What are the harmful effects?
2
votes
3answers
207 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 ...
1
vote
1answer
350 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 ...
14
votes
1answer
1k views

Why does looking at bright light trigger sneezing in some people?

Why does looking at bright light trigger sneezing in some people? Are there any recent studies that have found a cause for this Photic sneeze reflex? The Wikipedia article only references studies ...
2
votes
1answer
66 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 ...
3
votes
1answer
90 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
votes
2answers
154 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 ...
1
vote
1answer
513 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 happened if one looked directly ...
8
votes
2answers
2k views

Preferred Aspect Ratio for Human Eyes

Our eyes are spherical, our retina is circular, but still our eyes can see more in the horizontal direction than in vertical direction. Why is it so, why is the preferred aspect ratio not square? ...
1
vote
2answers
106 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 ...
3
votes
2answers
2k 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 ...
0
votes
1answer
63 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
90 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 ...
0
votes
1answer
219 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, ...
5
votes
0answers
272 views

Reason for seeing grid-like patterns when strobing a solid black-white image?

I was trying to do some stimulation for SSVEPs by strobing a solid black square and a solid white square. Weird thing was, I ended up seeing weird grid like patterns that looked like this, always of ...
10
votes
1answer
143 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 ...
1
vote
1answer
61 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 ...
2
votes
1answer
2k views

What negative effects can pinhole glasses have on the body?

While shopping in the local supermarket yesterday, I was surprised to find this display on one of the shelves. I also realize that I should have taken a pamphlet with me, as well as a picture of ...
8
votes
1answer
159 views

Is it a limitation of the eyes, or the brain, that we can't see a moving bullet?

Are the photoreceptors in our eyes not fast enough to register the fast moving bullet, or is the brain not powerful enough to make sense of something happening that fast?
6
votes
1answer
3k views

What causes the colors we see in eyes?

Genetics aside, what are the biochemical reasons the different colours of human irises? Also, related, how does eye colour change, particularly in childhood? (example: my eyes used to be blue, ...
2
votes
1answer
461 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 ...
3
votes
2answers
310 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 ...
1
vote
1answer
1k views

Why do I always close my eyes when someone takes a photo of me using a flash?

Everytime some tries to take a photo of me with a flash I manage to close my eyes (blink). It's not intentional and it's quite annoying. Why am I doing it?
4
votes
1answer
62 views

Does retinal detachment happen more frequently at night?

My understanding and experience is that during the night photoreceptors are less tightly coupled to the retinal pigment epithelium. Does this make it more likely for a retinal detachment to happen at ...
1
vote
1answer
77 views

Eye Brain Mapping

If our eyes are separated by some kind of full proof barrier/isolation, is it possible that our brain can picture/visualize two different pictures at a time? How the brain will function in this ...
1
vote
1answer
183 views

Why are trichromat cone cells unable to sense ultraviolet and infrared radiation?

I understand that cone cells vary in the color they sense, is this because of wavelength, frequency, something else, or a combination of the previous? I also understand that tetrachromats can see an ...
2
votes
0answers
74 views

Eye color genetics

I am trying to find a model to link the phenotype eye color to its genotypes. I know that there exists a simple model from Davenport, which explains {brown,blue} eyes. Further, there is an extended ...
8
votes
1answer
1k views

How does this illusion work?

I found this image on Google+ If you shake your head you can see a portrait of a person. Can anyone explain how the image is constructed in the brain?
2
votes
1answer
92 views

Is RGB diode lighting okay for the eyes?

Is a light source giving off light composed of red, green and blue lights harmful to the eyes? Does it lack any important qualities that other artificial light sources, such incandescent lamps or ...
1
vote
2answers
196 views

How long can you keep sheep eyes in formaldehyde before dissecting?

We're preparing for an experiment in our classroom and my teaching partner and I are at different points in the unit. I am concerned that the experiment will be less successful because of the ...
4
votes
3answers
184 views

Is it technically possible to make someone see something when their eyes are closed?

I'm writing a little article and need any information about how human vision works and latest technologies and discoveries around. Actually its not a professional article. Its for a group of my ...
2
votes
1answer
970 views

Perception of artificial light - flickering

I noticed something strange a couple of years ago. I was walking down the street at night, when it struck me that the street lights were flickering. But, when I turned to take a direct look at the ...
5
votes
1answer
63 views

Is the eyes' movement discrete?

When tired and it was dark, I noticed that if I focused on a dim light source and moved my eyes fairly rapidly sideways, the resulting images that lingered for a short while were not smoothly blurred ...
3
votes
1answer
142 views

Eyelids interconnected?

I've seen a patient who had a Vitrectomy (eye surgery) done on a single eye manifest massive swelling on both eyelids. That seems like having my left hand swell after punching a wall with my right ...
2
votes
1answer
330 views

Screen brightness for reading in dark room [closed]

While searching online I did not find any conclusive article on whether it is good or bad for one's eyesight to read on a computer screen in a dark room. Most mention that it will cause strain that ...
2
votes
1answer
339 views

Can visual acuity be improved?

Is it possible to completely cure myopia using natural methods (i.e. not with Lasik etc.)?. I have seen websites claiming that exercising the eyes will help improve eyesight. Is this true?
6
votes
2answers
87 views

Why do glial cells of the retina become more abundant the closer they are to the optic nerve?

I am doing a project on expression of GFAP in the zebrafish retina. GFAP is a marker for glial cells. I have found that the glial cells are more abundant the closer they are to the optic nerve at the ...
10
votes
1answer
318 views

Foveal ganglion cell density (Tay-Sachs Disease)

I’m currently reading on Tay-Sachs disease and have stumbled upon something regarding the typical “cherry red” macula symptom. On the one hand it is mentioned that the macula is almost devoid of ...
12
votes
2answers
500 views

When did vision evolve for the first time?

Today I wondered what the first organism to evolve vision would have been. I assume that it would have been kind of primitive and basic, but of course extremely innovative and eventually useful to a ...
4
votes
1answer
450 views

Why do rod cells not recover after bleaching upon exposure to bright light?

I'm confused as to why, when exposed to bright light, rod cells cease to function. I understand that exposure to bright light bleaches all of the rhodopsin, but...so what? Why doesn't the bleached ...
9
votes
1answer
422 views

Why does this illusion work?

This is another image I found on Google+ All lines are absolutely straight, parallel and perpendicular but why does it appear to have a curvature? Related: How does this illusion work?
1
vote
0answers
197 views

How do optical illusions work? [closed]

Hello fellow investigators I have two questions about optical illusions 1) A photo mosaic is something like this http://i.stack.imgur.com/Pzplp.png What are the optical principles behind our eye ...
10
votes
1answer
92 views

Are rods/cones rejuvenated periodically?

Pretty much what the title states. Some cells/structures in the human body undergo rejuvenation periodically by flushing away older cells and growth of new ones. E.g Skin, Blood Does this (for want ...
4
votes
1answer
229 views

Cause of short sightedness/ far sightedness

I recently had gone for an eye test. The doctor told that short sightedness/ far sightedness is caused due to shrinking or expanding of the eye. One thing i forgot o ask him was what causes that ...
9
votes
1answer
555 views

How does laser surgery correct accommodation problems?

When someone undergoes laser surgery to improve eyesight, how does it correct accommodation problems? Why does it not help presbyopia?