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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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2 answers
29 views

Do all Physocyclus globosus have pedipalps

While browsing photos of Physocyclus globosus (short-bodied cellar spider) on iNatrualist, i noticed that some have pedipalps while others does not, they are not Physocyclus globosus or not all ...
7 votes
1 answer
10k views

Dark veil when getting up too fast [closed]

I was asking myself this weird question. When you get up or stand up too fast, sometimes, you see something like a dark veil, and you aren't able to see anything distinctly for 2 or 3 seconds, then ...
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1 answer
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Do compound eyes exist in nature that have multiple "pixels" per ommatidium?

If yes, which species? What is the terminology for such eyes?
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1 answer
103 views

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 ...
1 vote
1 answer
68 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 ...
1 vote
1 answer
42 views

Can both lenses of different eyes intentionally focus at different amounts

Can each lens of both eyes have different accommodation rates, or have a different focal length to view objects of different distances. I understand that this can be a problem known as Anisometropia, ...
3 votes
2 answers
124 views

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 ...
1 vote
2 answers
204 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 ...
1 vote
0 answers
64 views

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 ...
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18 views

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 ...
-1 votes
1 answer
63 views

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 ...
0 votes
0 answers
16 views

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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30 views

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 ...
0 votes
1 answer
783 views

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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0 answers
27 views

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 ...
3 votes
0 answers
78 views

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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1 answer
58 views

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 ...
1 vote
0 answers
49 views

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 ...
16 votes
3 answers
4k views

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.
0 votes
0 answers
48 views

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 ...
1 vote
2 answers
25k views

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 ...
12 votes
3 answers
8k views

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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0 answers
32 views

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. ...
4 votes
2 answers
6k views

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 ...
0 votes
0 answers
219 views

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 ...
2 votes
1 answer
213 views

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 ...
2 votes
2 answers
85 views

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 ...
0 votes
1 answer
47 views

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 ...
0 votes
1 answer
66 views

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 ...
3 votes
1 answer
359 views

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 ...
3 votes
1 answer
181 views

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 ...
1 vote
1 answer
2k views

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 ...
4 votes
2 answers
1k views

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,...
0 votes
1 answer
49 views

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 ...
0 votes
1 answer
388 views

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 ...
25 votes
3 answers
119k views

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' ...
3 votes
2 answers
5k views

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: (...
13 votes
2 answers
5k views

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 ...
1 vote
0 answers
25 views

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 ...
4 votes
1 answer
79 views

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 ...
4 votes
1 answer
188 views

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 ...
1 vote
0 answers
175 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'...
0 votes
1 answer
142 views

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 ...
-4 votes
1 answer
166 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 ...
7 votes
2 answers
1k views

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 ...
0 votes
1 answer
244 views

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 ...
5 votes
1 answer
467 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 ...
1 vote
1 answer
217 views

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 ...
45 votes
3 answers
14k views

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 “...
3 votes
1 answer
2k views

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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