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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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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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 ...
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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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What happens in lasik operation?
First of all,I am very bad at biology. So please bear if it sounds elementary.
I heard about lasik operation for reshaping cornea.
Assume the patient is suffering from myopia implying lens is ...
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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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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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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 ...
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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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Do insects with compound eyes have depth perception?
Do insects with compound eyes have depth perception? They fly as if they do, but their eyes are so close together it seems like the image would be 2 dimensional.
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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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Why is my peripheral vision better for seeing in the dark? [duplicate]
I often walk around my house at night with the lights turned off and one night I noticed that looking straight at an object with very little light available made the object disappear from sight but if ...
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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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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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How can some animals see ultraviolet or infrared light?
I know that some animals like birds, bees, and fish can see ultraviolet and infrared light. Whether it is to detect flowers that bear nectar, or the urine trails of prey. But what I don't understand ...
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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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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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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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Heart rate sensor electrodes to be used for blink detection (simple EOG)
I have a cheap ECG/HRV/heart rate sensor module for Arduino, bought from Aliexpress. It has 3 electrodes: RA, LA, RL, which I guess mean right arm, left arm, right leg. The module outputs one single ...
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When do retinal cells stop differentiating? [closed]
I am having a hard time recalling where I had heard this, but I do recall someone saying (perhaps in a video) that cells in the retina divide very rapidly during infancy due to ongoing development of ...
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Why does a non-functional retinoblastoma protein cause tumours in the cells of the retina specifically?
I know that the name of the protein itself is the retinoblastoma protein - but that's only because the result of a pathogenic variant is retinoblastoma. I'm trying to kind of reverse engineer the name ...
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Why does there have to be two muscles to control the size of the pupil?
In dim light, the circular muscles relax and radial muscles contract to allow more light to enter the eye, and vice versa in bright light.
Why is there the need to have two muscles when probably the ...
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Does our brain contain an innate function about closing only one eye?
I wasn't sure where to post this, but biology seemed fitting for me. Sorry if I'm wrong.
I was wondering why, when we close both our eyes and look at light, it is clear we can see the light even ...
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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 layer,...
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How does the brain activate retinal cones in darkness?
The activation of retinal cones by light is how vision is formed; yet there are other methods, such as mechanical one, for activating light, such as pressure photopsia/phosphenes. This occurs when ...
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Is 50Hz noticably worse for eyes than 60Hz on a 4K monitor?
I was told in ux.stackexchange that this question is better suited for biology.stackexchange, so, here we go ;).
I have a 50Hz 4k monitor (28 inch and using 1920x1080 scaling - so, the text is super ...
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Why do I see different hues of colors between each of my eyes?
Frequently, I see colors with a slightly different hue when looking through my eyes individually. The right eye is more red-tinted ('warmer' hued) and the left is typically more blue-tinted ('cooler' ...
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What is the direction of the processing of light by the (human) retina and how does it happen?
Quoting Textbook of Medical Physiology by Guyton and Hall, 2016, page 647,
...the functional components of the retina, which are arranged in layers from the outside to the inside as follows:
(...
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Can "red" cone cells actually see much red light?
In electronics, the most common color scheme is the "red-green-blue" (RGB) scheme. This choice is often justified by claiming that the long- (L), medium- (M), and short- (S) type cones in the human ...
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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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Allometry of vision, can mice see their own fingers?
Looking around, I've found a lot of research on the allometry of visual acuity and vision at a distance, but not so much on vision close-up. As I understand it, the "near point" of vision is ...
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What happens to eyeball when you push your eye muscles harder? [closed]
I have myopia and I read that the rays of light intersect before the retina.
When I can not see clearly I can push somehow my eye muscles and can see a bit clearly. The object gets clear but moves ...
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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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Do the activity patterns of an owl species determine their eye colour?
Recently I've been thinking about the colour of owl eyes, and trying to figure out if there is a pattern anywhere between species.
I have read for example, that yellow-eyes implies they are day time ...
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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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Is the bipolar neuron of the retina considered a sensory neuron?
Any neuron that participates in sending impulses from receptors to the CNS are referred as sensory neurons. But I often see bipolar neurons of the eye (which according to the above definition should ...
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Why do colors clash in your brain?
Wen pairing two or more colors together, some "clash" or cause a effect visually where the two colors meet. To me it appears to be a black line between the colors or shading when in fact ...
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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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Why do I see purple stripes when moving a small source of light (flashlight) quickly in a dark room?
I was playing with my phone's flashlight (white) in a dark room, Just moving it around quickly when I noticed that I could see thin stripes of purple in the same shape as my hand moved, they didn't ...
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Are humans more adapted to "light mode" or "dark mode"?
I was discussing with a colleague about using dark-mode vs. light mode and remembered an article arguing that humans vision is more adapted to light-mode rather than dark-mode:
I know that the trend “...
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What shape is the pupil of squirrels?
In the animal kingdom there is a striking variety of pupil shapes, with great variety among relatively close relatives. Cats have vertical slits. Siberian tigers have round pupils. Cuttlefish have a W ...
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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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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 ...
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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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Why exactly are the reflections of sunlight in this dragonfly's eye hexagonal?
I photographed a rather cooperative, large dragonfly today and after getting back to my desk and looking closer at the images I realized that the reflection of the Sun in its eyes produced large ...
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Has anyone yet figured out how sensory signals for eyes and ears are encoded by our organ into electrical signals? [closed]
The most obvious way to give sight to blind and hearing to deaf is to give them a replacement organ for these. In order to do that we would need to understand how our eyes and ears encode sensory ...
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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 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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