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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Why can I feel pressure changes in my ears when I close my eyes and roll my eyeballs as far upward as I can? [closed]

My eyes were sore from staring at the screen all day, so I closed them and rolled my eyeballs up as far as I could. My ears started humming and I could feel an air pressure change in my inner ears.
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Why was light eyes selected for while non-myopia was not?

Assumption: Blue/green/grey (light) eyes in europeans were developed to see better at night in dark forests. Assumption: Myopia (nearsightedness) is to a large extent genetic. Given that these ...
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Non-Salticidae with °oo° Eye Arrangements

Since childhood, I've always thought of the °oo° pattern of four frontmost eyes as iconic for spiders (note: the pattern does not account for any additional eyes or lack thereof further to the sides ...
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Does my nearsightedness come into play when creating light outlines in the distance?

After looking at a light and closing your eyes, you see an outline of the light. I was curious how my nearsightedness would come into play. I look at a light in the distance without my glasses on and ...
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How far can a human see at night?

I am not talking about seeing in total darkness, which I understand is not possible. I am looking more about a question how far can a human see during starry night or with half moon/full moon. I tried ...
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What standard procedure taken to measure eye far point and near point?

I've read from various link that to measure power/dioptre of eye glasses lens, we need to put far point into equation for nearsightedness and near point for farsightedness. The problem is I cant ...
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Comparion between machine vision & human vision

I hope this is the correct Stackexchange to ask this question. I am trying to know : What is the current status of knowledge regarding human vision and pattern recognition. More specifically, How ...
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(How) do horizontal pupils dialate?

I was looking at mongoose eyes in particular, but my understanding is: Circular (human-like) pupils simply get larger/smaller depending on light levels, no change in "shape" Vertical slit (cat-like) ...
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How do cone cells underneath capillaries receive light?

Came across this image of retina's cross section: 1) How do the cone cells directly underneath the blood vessel ('demarcated in the picture') receive a spectrally correct representation of the ...
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140 views

Can Green color give Rest to Eyes?

Is it correct that Green color gives rest to our eyes compare to other colors?
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What is violet color?

We have 3 color receptors in our eye, so assuming the above picture is precise we are checking for 3 wavelengths: 450nm, 540nm and 700nm. Pink for example has an RGB value of R (700nm): 1 G (540nm): ...
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If one of eyes is blind, can that eye still feel pain?

I was wondering this when I touched my bare eye (my eye was open) and since I'm not blind I was wondering if an eye is blind, can it still feel pain?
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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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How many frames per second do human eyes see? [duplicate]

I observed when a helicopter rotor or fan is spinning the blades blur making it impossible to count the blades, but after a certain speed the blades seem to become visible making it possible to count ...
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Latest estimates for shortest and longest wavelengths of light visible by dogs?

Dogs (canis lupus familiaris) are dichromats, meaning that their eyes contain two types of cone, responding maximally to two different wavelengths of light, namely blue (429 nanometres) and yellowish ...
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What is the average eye sight for humans? How bad is one's eyesight if you are1 or 2 SD below average?

What is the average eye sight for humans? How bad is one's eyesight if you are 1, 2 or 3 SD below average? I googled but it was hard to find good search terms.
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Reason for acephalgic migraines

I suffer from acephalgic migraines, known commonly as ocular migraines. I’d like to know the reason why such migraines occur. Moreover, I’d be interested in knowing why do the following occur in the ...
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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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Do animals with their eyes ~180 degrees apart have depth perception?

Lots of animals have their eyes more on the side of their head, like an octopus or a parrot. Are animals with eyes more on the side able to tell the depth of objects at different distances? It seems ...
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What might alien have large eyes? [closed]

Don't rush to conclusions. This is a serious question. The most widespread depiction of intelligent, "human-like" aliens are that of a species with considerably larger eyes in proportion to body ...
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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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Why green light is good for our health? [closed]

I have a knowledge that when you woke up and see green light it increases your sight power. How it does so?
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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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how much can changing light enter the eye shap what you see? [closed]

Does it change the shape and how objects are seen or does it just stop you from seeing certain things?
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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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Why did we evolve to be able to see this specific set of wavelengths only? [duplicate]

It is understandable that life didn't evolve the capability to sense all wavelengths of light, it simply didn't need it. My question is, why did it evolve the set of wavelengths it has, for example, ...
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Does night mode on iPhone really help?

Okay so I know that night mode is supposed to filter out blue light that is bad for the eyes, but is it really more helpful than annoying? At night I do use it when I’m on the phone but it doesn’t ...
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102 views

How do our eyes see an inverted image? [duplicate]

How exactly do our eyes see an inverted image of what we are looking at? Does it have something to do with the shape of our lens (i.e. convex)?
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What are reciprocal inhibitory synapses?

Quoting Kandel's Principles of Neural Science, 2013, Amacrine cells generally receive excitatory signals from bipolar cells at glutamatergic synapses. Some amacrine cells feed back directly to the ...
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What are these tiny, almost transparent, dots in my vision? [duplicate]

Sometimes when I stare at a very bright thing such as the sky I see little dots. It's actually more of a circle with a little dot inside it. They are half-transparent and they move around a lot. When ...
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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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How many ommatidia does a honeybee have?

European honeybees (Apis mellifera) have compound eyes made of tiny facets called ommatidia. The number of ommatidia is usually known in most model insects, but I cannot find reference for the ...
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Why do eyes change colour after death?

Why exactly do eyes turn black when we die? (Or even change colour at all). The source of inspiration to this question is due to this video https://www.youtube.com/watch?v=6mNs_TcUyHc&t=627s (it's ...
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126 views

At what minimum distance the direction at which eyes point becomes parallel?

This is very similar, but different than this question about focus, let me explain why it's not a duplicate at all.. That other question is about the distance of EACH individual eye FOCUS, this one is ...
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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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280 views

What photoreceptors are necessary to permit infrared vision?

Humans have red green and blue photoreceptors allowing them to sense colours in the spectrum of about 400-700nm. Certain proteins allow for the extending of wavelength range in the RGB receptors, this ...
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Why do left and right eyes can require different power of lenses?

Both the eyes almost see the same things throughout our life. It is not like we use one eye more than other that it should become weaker. What causes requirement for different power of lenses for both ...
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Family eye genetics [duplicate]

Both my parents have brown eyes. My older and younger siblings have brown eyes. I have green eyes. Is this genetically possible? Back in 1962, this was questionable and led to family problems, ...
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131 views

Is it the theory of the 5 senses obsolete? [closed]

An enigmatic topic in traditional science was labelled as the mystery of the 5 senses, and how to best group senses by type. Is that theory now meaningless? Do Scientists still agree that that ...
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How do photoreceptors overcome the ambiguity of wavelength vs intensity to determine brightness? [duplicate]

I asked a similar question about the Principle of Univariance yesterday, but now I have another one. According to the Principle of Univariance, the input to a photoreceptor differs along two ...
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What is the neural coding of rod and cone cells?

In Rushton's paper on the Principle of Univariance, he states: Thus, though the rod input has two variables, wave-length and energy, the output differs only in one respect, namely 'brightness'. ...
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Why do floaters in the human eye appear to have a squiggly-line, tubular shape?

If you intentionally try not to tune out visual floaters in the eye, you can see them very clearly and they seem to have a squiggly line shape but with a volumous tubular look. Why is this? They ...
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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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How can Giant squid have $20,000 mm^{-2}$ photoreceptor cells, but no cones?

According to this post, Cephalopods have about $20,000 mm^{-2}$ photoreceptors in there eyes. However, Cephalopods (in my case, the Giant Squid) aren't born with cones (cells that dictate which ...
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What is the minimal focal length of the human eye?

What is the minimum length to which the focal length of our eye can go, even when considering the blurred images too.
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Myopia & the Blur Effect

I know myopia is caused by elongation of the eyeball. When the eye is too long, light entering the eye balls falls in front of the retina instead of on it. However I do not quite understand how this ...
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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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Question to the color scientists

I have a question. if you look at these two spectral diagrams (SPDs) from two different televisions that is calibrated to the same white point (D65) 6500K with a spectrometer. The problem is that ...
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What kind of eye strain causes an visual aurora effect? [closed]

When I have done too much reading on the PC sometimes I feel a tickling sensation inside my eyeball. At first I didn't even notice the tickle, however my eye would start to see blurred in one area, ...

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