Questions tagged [human-eye]
Questions about the biological function and structure of the human eye.
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Please help me understand these depictions of the neural tube regarding the embryology of the eye
I am struggling to understand the embryological development of the human eye, and I would be grateful for some hints.
A commonly found drawing of the formation of the neural tube is this.
I understand,...
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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 ...
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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 ...
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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 ...
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Why does grey-blue look violet?
The top right corner of this color picker is RGB(0, 0, 255). However we can see a slight violet tint, in the light-blue, blue-gray areas.
The top right corner of this color picker is RGB(0, 60, 255). ...
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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 ...
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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?
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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'...
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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 ...
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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 ...
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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 ...
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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.
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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?
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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 ...
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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 ...
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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 ...
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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?
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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 ...
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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, ...
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Can the human eye axial length decrease?
I just have a quick question regarding the axial length of the eyeball.
I understand that the axial length of the eyeball grows up until your around 20 years of age which is why hypermetropia ...
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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 ...
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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 ...
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What is the smallest visual unit perceptible to the human eye, like a pixel? (esp. in visual static)
If you close your eyes, you can often see visual static, where individual pixel-like things are much more visible than with the more smooth, crisp images one gets with open eyes. This led me to wonder ...
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Does the human eye’s field of view shrink when focusing on far away objects?
It seems like the lenses of the eye is like a fisheye lens that flattens out to a normal lens when looking at far away objects. Does that also mean that the field of view gets narrowed down as well? ...
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Do pinhole glasses help reduce eye strain?
I've noticed that I can read about 10x longer at screens and books without my eyes tiring using the "pinhole trick" - where you curl your fingers and look through the hole (great explanation here ...
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Why did we lose our fourth type of cone cell (in the eye)?
Most species of birds, reptiles and fish have four types of cone cells in their retina, thus they have four independent channels for conveying color information. They are:
short-wave (S) cones: ...
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Is the human iris concave or convex?
Most drawing and 3D modeling tutorials show the iris to be concave. But all the diagrams I Googled show the iris is at best flat, otherwise even a little convex (discounting the optical distortion in ...
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Is the backward positioning of photoreceptors bad design?
(Several questions have been asked about this topic but most are quite old and there has been at least one study since then that has attempted to answer this in a new way)
Since photoreceptors are ...
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Does the human eye see things at twice the distance in a mirror?
If I'm standing 3ft away from a mirror and looking at something in it that is behind me but 5ft away from the mirror, do my eyes see that object as 3ft? Or 8?
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Does the Human Eye White Balance?
OK, this may be a stupid question…but here goes.
Does the human eye “white balance” itself?
I assume that each human perceives colour slightly differently according to the peculiarities of their own ...
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How are the images of both eyes combined to form one image?
When you see an object by one eye, ex.right eye, you see it from the right direction and the opposite if you see it by your left eye, but when you open both eyes, the image appears somehow centric in ...
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Is it possible to simulate tetrachromatic vision in a trichromat?
Suppose we are able to stimulate the whole matrix of cones of a human retina, targeting each cone individually¹. Normally we would project an image in the LMS color space onto the cones, in such a way ...
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Why do our eyes not have interference from other sources of light?
When one looks forward at a glass of wine, one is seeing it via the reflection of light off of the glass. But if you have a person to your right, looking to the left side of you (still in front of ...
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Why does brain invert the image formed on retina? [duplicate]
I have been studying about the human eye and it's working in school for some time. I came across something. I have been taught that the image formed on the retina of the eye by the lens is inverted ...
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