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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Are there animals / mammals which only have one eye?
Do all animals (of a certain size and not thinking about worms) have the possibility to perceive depth?
Do all mammals have at least two eyes? Are there mammals with more than two eyes?
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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 ...
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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 ...
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Why do the eyes of this cat have different colours when viewed from different angles?
Why do the eyes of this cat have different colours when viewed from different angles?
Both of the eyes of this cat appear yellow when looking straight at the camera.
However, when the cat looks at ...
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Is Near-infrared focused light safe for your eyes?
I found a new product, but I'm afraid it's not safe. Can you help me understand what the safety limits are when it comes to near-infrared light focused on your eyes is?
I'm assuming the wavelength ...
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Did the number of rods changed from ancient time?
Correct me if I am wrong, but I know that rods work under limited light conditions only.
But now we are in a world that always have lights everywhere unlike ancient time when humans had to deal with ...
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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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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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The colors blue and golden (yellow-orange) and the human eye / brain
Many years ago I read a review in an article about why we love for example Lapis Lazuli so much. The article stated that there are two specific colors, yellow as golden (when it glows or shines) and a ...
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Does Rüppell's Griffon Vulture Have Greatest Vision Acuity? (Small Carrion Spotted at 10 km+?)
Synopsis:
Some sources seem to imply the Rüppell's (griffon) vulture (Gyps rueppelli) can see objects at a distance in excess of 10 km -- roughly three times the ...
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What do I need to do to make a Reverse colorblind image?
As a 15 year suffering from moderate Protan colorblindness, I've wanted to find any advantages of colorblindness. I discovered there are Reverse colorblind tests, which only colorblind people are able ...
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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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Why do most fish move fins orthogonally with their axis of symmetry?
So recently I read the question why are most fishes vertical (in the sense of distribution of their body mass) and it got me thinking what is the reason behind the direction they move their fins. My ...
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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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Would a transparent iris serve its purpose?
The function of the iris is to regulate the aperture of the pupil. How does the iris obstruct light? Is it due to the pigment present in it? Or is it just due to the sheer presence of it?
I am doing ...
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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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White/Gold vs Blue/Black dress
So I'm sure you've all seen the dress photo where people see the dress as either White and Gold or Blue and Black.
It has essentially 'split' the internet because some people see the dress and they ...
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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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How does brain activity change when focusing on something within peripheral vision, as opposed to the fovea?
Normally when looking around, we mentally focus on what we see within our fovea, as that is where we have the greatest visual acuity. However, it is still possible to focus (both physically with the ...
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Is the nervous message sent by an eyelash being flexed sent all the way to the brain?
Since the reflex to close the eyelid once an eyelash is touched seems very fast, does the signal from the neuron detecting the touching travel all the way to the brain, get processed then back to the ...
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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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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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Why do some mammals have incomplete orbits?
I've noticed that a lot of carnivorous/omnivorous mammals (most, if not all the members of carnivora and some ancestral cetaceans), as well as some herbivores (marsupials), have incomplete orbits that ...
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What happens to eyelids when we feel sleepy?
Why is that whenever we feel sleepy, our eyelids start to feel heavier.
It is not like we can any time close our eyes and will immediately fall asleep. But, when we feel sleepy our eyelids ...
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Would preserving your Eyes from Light keep them healhty?
I read about why eyesight diminishes with age.
I am aware of the fact that there are different causes that can affect the quality of image received by our eyes and that being vague would not lead to a ...
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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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Does iris color effect the amount of light that reaches photosensitive ganglion cells?
Does eye color (of iris) have any effect on the amount of light reaching retina cells and hence effect melatonin production?
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What is the field of view of humans (not just fixed angle eyes)?
What is the human field of view also counting the maximum vertical and horizontal eye movement (rotation), with the head still.
It is unclear from this question whether the answer relates to the ...
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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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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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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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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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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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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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Would a VR headset exacerbate myopia or could it be used to retrain the eyes?
I've learned that there are two primary hypotheses to explain myopia: not enough use of distance vision or not enough sunlight
If the distance between an eye and what it's focusing on is the primary ...
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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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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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How are on and off bipolar cells of the retina arranged?
In the retina, there are both on and off bipolar cells. But how are they spread out in the retina? Are they so, that there is one of each after one another? Or are there areas where there are clusters ...
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light hitting the center of the retinal receptive field
In my teachers slides, it says "light hitting the center of the retinal receptive field can either increase or decrease the number of impulses fired"
Is this "or" because it ...
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How to calculate average Corneal Thickness?
I have a question which I may be making out to be a lot more complex than it actually is.
In my department we have a machine which can image the cornea and give values of various parameters (eg ...
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Is it possible to focus only one axis of astigmatism?
When we look at something close, we focus our eyes as a circle. But what if someone has astigmatism and focuses on something close, is it possible for the eyes to "focus" only the axis that ...
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Are afterimages centrally regulated?
As I understand, negative afterimages might be induced by retinal cone bleaching or neuronal adaptation. I have heard that some experiments have suggested that afterimages can be centrally regulated. ...
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Do all animals with eyesight get an upside-down image on their retina, or is it right-side up with some?
here's as good an image as any for showing the thing about human vision that I am asking about:
So, our retina gets an upside-down image.
My question is, do all animals' eyes work this way? Or do ...
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Image sensitivity of eyes and peripheral vision
I have bad eyes and need glasses. However I have noticed when it is dark, I am able to see contrasting colours a lot better in the corner of my eyes, than in the center, e.g a mark on my wall I can't ...
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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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Does cataract condition cause red film when sun is shining?
Since two years ago I have a red film in my field of vision when the sunlight (or a white spot) is at the border (or even lightly behind) of the vision field, the red color is especially obvious at ...
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Difference in frame rates of normal and peripheral vision
I recently encountered an incident in my laboratory. It was evening and the sunlight entered the lab through a window with exhaust fans. So the ray kept flickering at fixed intervals.
I noticed that ...
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Insects are attracted to light, what if the light is too bright?
Insects are known to approach light sources. I know that they use it as navigation tools, by maintaining a constant angle between their path and the light beam. However, if a light source is ...
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