Questions tagged [human-eye]

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

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Why does Haidinger's brush tilt depending on rotation direction?

Based on the Wikipedia explanation of Haidinger's brush I would expect it to remain oriented to the light polarization, no matter which way I rotate my head. However that is not what I observe. When I ...
jpa's user avatar
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Is there a functional model of the human retina for simulation of conversion of illuminance pattern to nerve signals?

I'm looking for a model that would take a pattern of spectral irradiance over the retina as a function of time and space and convert this into the signals propagating through the fibers of the optic ...
Ruslan's user avatar
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How do we see the violet color?

Here is exactly the same question with an accepted answer. However, that answer looks wrong (I can’t find the “alert moderators” button). Firstly, it refers to a dubious source. Secondly, it ...
Imyaf's user avatar
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Why do different people perceive the colors of the Northern Lights (Aurora Borealis) differently?

A few days ago, I was in Norway with a group of about 20 people. We were fortunate enough to witness an impressive display of the Northern Lights that lasted several hours. The next day, we discovered ...
Vorbis's user avatar
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Does the VR headsets make us focus extremely close?

Firstly, if I ask this question in Ask Different or Super User, the users there may say this is related to a biology or physics. The background is: we were in general told that: don't read a book too ...
Stefanie Gauss's user avatar
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2 answers
120 views

What is the part between the eyebrow tail and above the eyelid called?

I need to know that anatomical name of the portion of the face between the eyebrow tail and the eyelid, as highlighted in red in the image below, as I need to refer to that particular area in writing ...
hecate's user avatar
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Human Eye Diagram: question about some dimensions

Does anyone know any of the answers to these questions about this human eye diagram: What points should be the center of the circle for the radius numbers (Rn) in the following diagram? The ...
Nick's user avatar
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How is opsin of rhodopsin is different from that of iodopsin? [closed]

Rhodopsin contain retinal, an aldehyde of vitamin A and opsin protein and iodopsin also contains retinal along three different types of opsins namely erythropsin, chloropsin and cyanopsin. But kind of ...
Venkatesh Choudhary's user avatar
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Is the amount of pigment in one feature (e.g. hair, eyes, skin) connected to the amount of pigment in another?

Let's say, genes allowing it, you have a red-haired child with hazel eyes. The hair is a darker/deeper orange color, so (if I recall correctly) having some degree of eumelanin—not much compared to ...
inkwell87's user avatar
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Would asymmetrically positioned eyes impair vision?

Assuming one eye is 5 cm further down compared to the other, would that somehow change perception if the brain has long enough to deal with that incoming information? For example, if you were born ...
iwab's user avatar
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Does tetrachromacy affect eye color?

The majority of people have three cones in their eyes, though there are rare cases of some people having 4 cones (tetrachromacy). There is some genetic testing to support evidence of tetrachromacy, as ...
Nick Muterspaugh's user avatar
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Relation between image on retina and the real one: looking at the two objects that are 45 degrees apart, what's the distance in the actual image?

These are what I understand about the vision. lights come through the pupil. an inverted image of the real objects is formed on the retina. which is determined by the angles. (so (a, d) and (b, c) ...
stay stay's user avatar
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Would using positive numbered glasses while using a computer help prevent myopia?

There are multiple web pages linking screen-time and myopia. While this is not necessarily proven, for example as shown on the NIH page here https://pubmed.ncbi.nlm.nih.gov/31943280/ , it seems ...
123's user avatar
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Laser in mirror experiment

Apologies if this question is very simple I performed an experiment where I would shine my toy laser at the mirror and it would be reflected. Now here is what I tried: I could see my laser toy , I ...
Naveen V's user avatar
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How deep under water can humans open their naked eyes without damaging them?

Humans can tolerate a maximum pressure of 100atm, but it becomes uncomfortable above 30 atms. Deep divers usually wear protective equipment like goggles among other things and our eyes seem to be more ...
Aditya Kumar Panda's user avatar
10 votes
2 answers
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What is the minimum light intensity that a human eye can detect?

By doing a quick search in Google, I find a series of pages dedicated to physics exercises claiming that the human eye threshold for light intensity is $10^{-10}$ W/m${}^2$. However I cannot find any ...
Mauricio's user avatar
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Is harmonic resonance in Photoreceptors explored?

Look at the resonance curves of the L-cone (OPN1LW) in humans, it has its peak at ~570nm and rises up in the lower wavelength (higher frequency) area. For me as a musician, that looks like a natural ...
rhavin's user avatar
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1 answer
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Why do humans see exactly one octave of light?

The visible spectrum of light is often defined as 350nm to 700nm. On Wikipedia, it says 380nm to 750nm. Either way, the upper bound is very close to double the lower bound. This means humans can see ...
Lycodo's user avatar
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Can color-blind people see the effect of combining red, green, and blue light beams?

When combined, red, green, and blue light beams result in white light. This effect is observed by most of us, but can color-blind people also see this effect?
Jordan G's user avatar
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1 answer
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Will lidocaine stimulate photoreceptors?

Lidocaine apparently blocks voltage-gated sodium channels in sensory neurons and thus prevents action potentials, but photoreceptors like rod cells require hyperpolarization (through blockage of its ...
Rayan's user avatar
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What is the best estimate of RGB color sensitivity of human eye?

Web has a lot of references for human eye color sensitivity curves. Examples are This article: J.J.Vos, Colorimetric and Photometric Properties of a 2° Fundamental Observer (1978) [3] has a very ...
Jennifer M.'s user avatar
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What is the physiological difference between looking at small things vs far away things?

If you look at an item that is far away, vs a smaller version of the same item up close, such that both objects take up the exact same degrees of arc in your field of view, what do your eyes do ...
David Kennell's user avatar
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Percentage of nervous energy used by human eyes

I am reading a book 'How to stop worrying and start living' by Dale Carnegie. I stumbled across this statement below and I couldn't find any research article to backing this claim. Does anyone know if ...
Naman Parikh's user avatar
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Vision System: neural activity is modulated using FSK?

I’m learning about the human vision system and signaling. Does anyone know if the signaling used by the vision system is modulated at the neuron using amplitude frequency shift keying? I present my ...
Nick's user avatar
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Why do eyes feel exhausted after reading on a computer screen for a long time? [duplicate]

Similar question before closing this one was: Question. The answer holds true for most of the observations, but my observation differs from what is described in that question. Even if we consider that ...
lousycoder's user avatar
25 votes
2 answers
4k views

Why do blood vessels in the eye not obstruct vision?

As light enters the eye, it reaches the photoreceptors at the "base" of the retina, which then pass that signal to the bipolar and ganglionic neurons -- the latter of which send the signal ...
theforestecologist's user avatar
3 votes
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31 views

Are ganglion cells in the foveal avascular zone served by choroidal blood supply or diffusion from retinal layer capillary beds?

I am trying to determine which blood supply (choroidal or retinal) serves the retinal ganglion cells that respond to foveal cone stimulation. I know that the fovea is supplied by the choroid, but it ...
Joe's user avatar
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Non- brown, blue,green eye colour genotypes and genes

In genetics, eye colours (brown, green and blue) are determined by bey2 and gey genes. But what about hazel, grey and amber and more? I read a webpage about hazel eye colour and saw that there is a ...
AdvilDuttay's user avatar
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What is the true response of human photoreceptors to different wavelengths? Why is there so much disagreement in the literature?

I can find several qualitatively different diagrams of the responsiveness of human cones and rods to different wavelengths of light. A page referencing Bowmaker and Dartnall, 1980 has the following ...
RavenclawPrefect's user avatar
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174 views

Why are we more sensitive to green light when 65% of our cone cells are red cone cells?

I read, "human eyes are most sensitive in 555nm which is green. Human eyes are more sensitive to green than to red, and in low-light conditions even more to cyan than to green." But it doesn'...
Lisa Baron's user avatar
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2 answers
191 views

Would green light look different if blue and red cones were deactivated

When looking at a graph plotting "blue", "green" and "red" cones reponses to different wavelengths, you can see that any wavelength trigerring a response from green cones ...
Uretki's user avatar
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-4 votes
1 answer
155 views

How fast does eyelid close when eyelash is triggered?

What is the reaction of blinking like when an unexpected piece of wood or something hits an eyelash and then an eyeball? A piece of stone flew into my eyeball when we knocked a wall down, and it hit ...
bandybabboon's user avatar
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Are there any congenital anomalies that cause a lack of epicanthic folds in a child who would normally have them?

Wikipedia lists several medical conditions associated with epicanthic folds. Mount Sinai says that epicanthic folds in a baby who would not be expected to have them is a diagnostic tool that indicates ...
Adam Lincoln Steele's user avatar
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How RGB cones see other frequencies? [duplicate]

Orange,violet and yellow have different frequencies. How can we see them, as we have only three receptors rgb? Merely combining those frequencies cannot generate a new one.
Mini kute's user avatar
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92 views

Eye vision for distant large objects versus small close objects

We often hear that looking at distant objects after staring at screens is good for the eyes to prevent strain. But from the perspective of eye muscles, what is the difference between small font that ...
WDUK's user avatar
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5 votes
1 answer
401 views

How much light can pass through the human eyelid?

My sister tells me that at night when the lights in the room are off that she can see the ambient outdoor light from neighboring buildigns and streetlights through her eyelids (i.e., when her eyes are ...
prata's user avatar
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2 votes
1 answer
61 views

Is chromatic aberration related to the spectral sensitivity of the human eye and can it cause "relative myopia" and "relative farsightedness"?

in the text below, the authors equate chromatic aberration and the spectral sensitivity of the human eye. Aren't these two very different phenomena though? They also propose a so-called "relative ...
Fipah's user avatar
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0 votes
1 answer
70 views

Inheritance of FEVR (Genetic Disease)

If a woman has FEVR and is affected by the disease, what are the chances of her passing the disease to future generations. I read somewhere from a credible source like NIH(I couldn't find the link ...
Stephen Jacob's user avatar
2 votes
0 answers
43 views

Eye Optics/Emmert's law: Where to place scaled copies of an object so they have identical images on the retina?

I read that the center of projection of the human eye is the entrance pupil. So given a light ray which intersects the objects position and the center of the aperture stop, all copies of said object ...
InteractiveCube's user avatar
2 votes
0 answers
62 views

How would our vision be improved if our photoreceptors were not backwards?

I'm curious to how much better human eyesight would be if the nerves from our rods and cones were correctly placed behind the receptors? Are there any Animal Models with correctly placed ...
Gabriel Fair's user avatar
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The position of the macula in comparison to the blind spot

Which is located in a higher postion? Macula or blind spot?
a.RR's user avatar
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0 votes
1 answer
761 views

How much percent of image does our eyes focus at any instant?

I learned in highschool that even thought we have a wide view, we only observe a tiny fraction of that view through our eyes. So at any instant we are not really looking at all the objects infront of ...
gfdsal's user avatar
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2 votes
1 answer
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Why does our visible range not include infrared or UV radiation? [duplicate]

As the radiation peak of the sun is in the UV region and since at around room temperature materials emit radiation at IR, I wonder why our eyes are not capable of using these wavelengths. I guess ...
Ben's user avatar
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1 vote
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368 views

Why do we get tunnel vision during fight or flight response?

I have a question regarding tunnel vision during the fight or flight response. I believe that during fight or flight high levels of adrenaline are released which causes the pupils to dilate allowing ...
James's user avatar
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1 vote
0 answers
61 views

Why does Cyan appear bluish rather than greenish, when the phototopic eye sensitivity is highest in green (and Cyan contains blue and green equally)?

Cyan contains blue and green equally. Phototopic eye sensitivity is highest in green. Why, then, does Cyan appear bluish to most of us, rather than greenish?
Ritesh Singh's user avatar
1 vote
0 answers
15 views

Can the eye determine which type of defocus is presented to it?

I have a question regarding myopic and hyperopic defocus. My question is, is the eye able to determine which type of defocus is presented to it and if so what mechanisms allow it to distinguish ...
James's user avatar
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2 votes
2 answers
981 views

What are the physiological effects of retinal exposure to 380–400nm light?

There are two categories of sunglasses: UV380 sunglasses block all light with wavelength 380nm or lower, while UV400 sunglasses block all light with wavelength 400nm or lower. This made me wonder, ...
hb20007's user avatar
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3 votes
1 answer
956 views

Can the axial length of the human eye decrease?

I understand that the axial length of the eyeball grows until you are around 20 years of age, which is why hypermetropia decreases with age but myopia doesn't. My question is: can the axial length of ...
James's user avatar
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2 votes
0 answers
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How does sleep prevent our eyes from drying out?

If we don't sleep for about 16 hours, our eyes start to get dry, and no amount of eye drops helps. You use eye drops and then you're dry 10 minutes later. However, after you've slept for 8 hours, your ...
Pavel Orekhov's user avatar
-1 votes
1 answer
87 views

What causes eye strain when viewing any display?

Few everyday experiences: Staring at the physical paper (or any other sight in nature) doesn't cause eye strain. Staring at the LCD screen causes eye strain. Some of the differences in properties I ...
henceproved's user avatar

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