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Questions tagged [human-eye]

Questions about the biological function and structure of the human eye.

32 questions with no upvoted or accepted answers
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Could being exposed to excess UV in the arctic lead to a human eye color change? If so, what is the mechanism?

The CBS News article Expedition Antarctica: A father and son's journey to save the planet says (in part): Thirty-two years ago, Robert Swan made history as the first person to walk to both poles. ...
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91 views

Can low melatonin levels and/or LED lights cause or exacerbate macular degeneration?

I have two questions that may or may not be interconnected. My first question is: Does melatonin prevent macular degeneration? Could low melatonin levels (caused by blue-rich light exposure in the ...
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311 views

What is the average volume of the human Psychic tear? (“emotional tear”)

My goal is to find out the volume of the average human "emotional tear" (Psychic tear - sadness, happiness), specifically when crying. I found a lot of information about Basal tears (constant ...
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53 views

Infrared emitting diode eye safety

I'm thinking of creating my own laser tag system and am a bit concerned about the eye safety aspect. Most of the homebrew system I've seen use the TSAL 6100 diode(http://www.vishay.com/docs/81009/...
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45 views

How is the eye damaged by computer screens?

Eyes are damaged by persistent use of computer screens. On giving it some thought, it felt quite magical that your eyes are damaged simply by looking at something. I googled where there were articles ...
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61 views

Are there people who can change one of their eyes' depth of focus, while not changing the other eye's?

Are there people who can change one of their eyes' depth of focus, while not changing the other eye's depth of focus, without any surgical or other external mechanical intervention? Edit: let's ...
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632 views

Do blurry images cause eye strain? At what point is an image so blurry the eye stops trying to focus it?

I'm a user experience designer concerned about a new trend of blurring screens when showing a lightbox/dialog box over top (see below). From what I know, blurry images cause the brain to work hard ...
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43 views

Controlling the pursuit path of the human eye

The human eye scans images by panning focus along a certain path. Stork et al. (2002) revealed that there is a feedback process involved in moving ocular focus along a path that produces minimum ...
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646 views

Reason for different color perception in left/right eyes?

What could be the reason for a difference in color perception between the two eyes of an adult individual without any known eye conditions? In particular, a difference in the perceived color ...
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852 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'...
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796 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 ...
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21 views

What is the average eye sight for humans? How bad is one's eyesight if you are1 or 2 SD below average?

What is the average eye sight for humans? How bad is one's eyesight if you are 1, 2 or 3 SD below average? I googled but it was hard to find good search terms.
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24 views

Does the ratio between M and L cone cells vary in one indiviual?

Wikipedia says: The ratio of M and L cones varies greatly among different people with regular vision (e.g. values of 75.8% L with 20.0% M versus 50.6% L with 44.2% M in two male subjects). This ...
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68 views

If longer wavelength color is perceived faster by human, what about non-spectral color (black)?

Related to human vision, I read the hypothesis about how longer-wavelength color is perceived faster by human eye than shorter-wavelength color source : A Brief Classification of Colour Illusions. But ...
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77 views

Differences that are too small to see

Consider two identical pieces of paper. Scenario 1: On both something is drawn in black ink. If the difference between the areas covered in black ink is sufficiently small, I cannot see the ...
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263 views

Why bipolar neurons in retina transfer information via graded potentials?

Why should bipolar cells prefer graded potentials to action potentials? My attempt: I know that graded potentials are better in processing information since stimulus is directly proportional to ...
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342 views

Can human perception differentiate between monochromatic and polychromatic light?

Maybe monochromatic is not the right word, what I mean is light consisting of a single wavelength (i.e. a spectral color) versus light composed of photons of multiple wavelengths (intermediate color). ...
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578 views

Is the human eye supposed to see the lense effect?

Just as the GoPro cameras, we need lenses to be able to focus. Nevertheless, we can see the "fisheye effect" on the shots taken by GoPros. I am talking about this: Is it possible to notice the "fish ...
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71 views

Do squids or octopus suffer from myopia(hyperopia)? Do other vertebrates get myopia(hyperopia)?

Both vertebrates and cephalopods evolved very sophisticated camera-type eyes, and both are capable of focus. But it also pose a risk of inability of focusing, such as myopia in human. So is myopia a ...
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2k views

Why does vision gradually becomes dimmer in bright setting?

I don't know if this is only happens to me, but if I am in a well lit room and I stare at one point or just look at one area without moving my eyes around my vision in that specific light setting ...
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392 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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48 views

Does the change in eye color (melanin concentration) affect the iris pattern?

In cases of acquired heterochromia, is there a quantifiable change in the iris pattern; the clefts , furrows, etc. If yes, what changes are observed? And if no, are there any diseases or acquired ...
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39 views

How quickly can lasers of various wavelengths and powers impair human vision or cause pain in the eyes?

There is a discussion on HackerNews about how self-driving cars might be susceptible to confusion attacks using a cheap laser pointer and a RaspberryPi. Some people argue that human drivers, too, are ...
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398 views

Why are there ghost images of objects just out of focus

I have observed an interesting phenomena with my vision lately. I just think I have never reflected over this before but it might always have been this way. I am nearsighted and have no problem with ...
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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 ...
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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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14 views

What standard procedure taken to measure eye far point and near point?

I've read from various link that to measure power/dioptre of eye glasses lens, we need to put far point into equation for nearsightedness and near point for farsightedness. The problem is I cant ...
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49 views

Is there any biological basis for the commonplace “eyes popping out” cartoon?

We might all be familiar with images like these below: I see this clearly "works" in a cartoon context. It makes a point. That "eyeballs" hanging outside belong to the individual and can be shown ...
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4k views

Why do we see better on stretching our eyelids to the side?

I've often noticed that on stretching my eyes to the side I see a lot better. On searching, I read that this happens because the cornea reshapes itself (due to the ciliary muscles). But is that all, ...
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101 views

Nystagmus drug FDA approval?

Congenital Nystagmus is an eye focusing disorder. It happens in manuals. Wikipedia lists several treatments on its page. Are any of those FDA approved for human use of that disease. drugs found to ...
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29 views

Why do I see two of every object?

When I place one finger in front of my eyes and focus on something far, I see two fingers. When I focus back on finger I see the far things becomes two and finger becomes one.
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38 views

Why are there multiple eye colors?

Human eyes vary in color between people. Why are there multiple colors? Any continuous property of the body, like arm length, varies during the evolution, there are changes between it's value of a ...