Questions regarding how the brain interprets information from the eyes. Consider using the "eyes" tag for discussion of eye anatomy, physiology and evolution.

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Why does squinting allow you to see objects more clearly?

How does squinting alllow one to see clearer pictures? What are the harmful effects?
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239 views

How does someone with red-green colorblindness see yellow on a monitor/television?

I recently watched the video This Is Not Yellow explaining how red, green, and blue pixels can be used to create images of all other colors. Since yellow is created with red and green pixels, how is a ...
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2k views

Does coloring affect the perception of depth?

I have a question about the mechanics of human vision which may be as much of a physics question as it is a biology/physiology question. I noticed that if I try to imagine a clear blue daytime sky ...
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1answer
102 views

Congenital blindness due to retinitis pigmentosa - does it exist?

Retinitis pigmentosa (RP) patients typically become blind after a period of years in which their eye sight slowly deteriorates due to photoreceptor degeneration. Generally RP patients develop ...
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1answer
115 views

Do blind people learn Braille equally fast as the sighted?

The visually deprived brain undergoes extensive remodeling due to cross-modal plasticity. This leads to increased areas of the cortex being available for other purposes such as tactile processing. Now ...
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1answer
78 views

Are some facial features more important than others in human facial recognition?

I'm often surprised by the human ability to correctly identify other individuals despite significant modifications due to ageing, hairstyle, injury, etc. But, sometimes the addition of a beard and a ...
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1answer
82 views

Can the negative afterimage appear only if there is light or is it possible in darkness?

Reading the following paragraph: After staring at the red and blue shamrock, you saw a green and yellow afterimage. Opponent-process theory proposes that as you stared at the red and blue ...
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95 views

Improving myopia

I have a friend who no longer needs glasses. He previously had myopia in both eyes but over the years it has improved until he no longer needs glasses clinically. He's had glasses for over 30 years ...
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Would constant light or fading light be registered as more wakefulness promoting by the Supra Chiasmatic Nucleus?

During the fall and winter season, a number of people are experiencing Seasonal Affective Disorder. One of the way it has traditionally been treated is with a dedicated lightbox - a very high ...
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183 views

Why don't myopic people see the world upside-down?

I found this image while reading optical instruments in physics. If we look at the uncorrected rays, we see that the image they outline gets inverted. So why don't people with myopic vision see ...
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5answers
120 views

Why is human vision restricted to 400-700 nm?

Across the electromagnetic spectrum, 400-700 nm is a narrow spectrum of frequencies and focused in the region of short wavelengths. For example, radio waves cover a large range of frequencies ...
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1answer
209 views

Are these claims of “revolutionising” understanding of human vision and hearing valid?

I've started a hobby machine vision project (and posted some questions to this end on other SE sites) and on a side track, also been looking at relevant research in human vision (and partly, hearing). ...
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182 views

Can the human eye distinguish colors in the periphery?

In the back of my mind I have the idea that human eyes can't notice the color of objects in the far periphery, and that any subjective perception of colors is done by the brain that tries to fill in ...
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177 views

How does optogenetics work?

I am aware of the post here 'Optogenetics - How do microbial opsins work?' however it is a bit too technical for me. I am struggling to understand how the neurons can be genetically engineered to ...
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3answers
3k views

What is the equivalent of shutter-speed in Human eye?

I just learned that in video cameras, every frame of the video has its own shutter speed. And I know how frame-rate in human eye works out, well, not completely, hence the question. ...
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1answer
129 views

Was life less colorful before color vision evolved?

According to Wikipedia, we know that color-vision photopigments appeared in the common ancestors of tetrapods and fish at least 360 MY ago. Would life have been less colorful before the evolution of ...
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2answers
715 views

Why can't the human eye focus blue light?

I recently noticed that it is hard to focus on blue light sources, especially at night. When observing a blue light source, e.g. a neon sign, it looks somewhat blurry. A sign with a different colour ...
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3answers
217 views

Is it technically possible to make someone see something when their eyes are closed?

I'm writing a little article and need any information about how human vision works and latest technologies and discoveries around. Actually its not a professional article. Its for a group of my ...
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1answer
426 views

Why do we squint?

Recently, I was having an eye exam and admitted to squinting my eyes to sharpen blurred edges. Later, while waiting for the dilation to set in, my brother (a would-be pharmacist fresh off an anatomy ...
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1answer
78 views

Can other animals see black differently?

I am not sure if this is the right place for this question, but this is a debate that has been going on between two colleagues for days and I need a resolution because it's driving me crazy. So any ...
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72 views

HSL Lightness vs Eye sensitivity

In a monochromatic spectrum, is the human eye equally able to distinguish between lighter colors just as it is in distinguishing between darker colors? I mean is there really a linear relationship ...
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70 views

Does retinal detachment happen more frequently at night?

My understanding and experience is that during the night photoreceptors are less tightly coupled to the retinal pigment epithelium. Does this make it more likely for a retinal detachment to happen at ...
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1answer
40 views

What is the relationship between W, X, Y and P, M retinal ganglion cells?

In Guyton and Hall Textbook of Medical Physiology (12e) the retinal ganglion cells are classified into W, X, and Y types. However in Gray's Anatomy (40e) they are classified into Midget and Parasol ...
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43 views

What are those visual and auditory reflex controlled by the midbrain? [closed]

The midbrain is a centre for certain visual and auditory reflexes. But what are those reflexes exactly? My study book says that these reflexes are, e.g., responsible for moving the eyes to view ...
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59 views

How far can birds see? [closed]

I have heard that birds have exceptional eyesight. How far does this mean they can see? What's the resolution like? Are we talking about just vague shapes or something like, at 100 feet, seeing ...
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1answer
165 views

Does 405 nm light set off phosphorescence in the eye?

While playing with a blue/violet laser (5 mW, 405 nm) tonight, I noticed that on dark, non-fluorescing surfaces, the beam reflection was trailed by what looked like a dimmer reflection of the beam. ...
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1answer
51 views

Color vision across species

Is it true that color vision is sex-linked for all species with binary sexes? Is there an evolutionary significance to the fact that color vision is X-linked in humans? E.g., only female humans can be ...
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1answer
117 views

Retina Transplant Difficulties

Why is retina transplant not as easy as the normal eye donation and transplant (I think the latter involves the cornea ) ? This says that a new method has come up but why isnt the process similar and ...
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1answer
77 views

Do human visual functions degenerate due to genetic factors or by external factors?

Does eyesight primarily deteriorate 'naturally' due to genetics (genomic/epigenomic factors), or due to external factors such as normal wear and tear, or disease? By normal wear and tear I include ...
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319 views

What exactly is the neural receptive field?

Neural receptive fields map the spatial or temporal distribution of the data to individual neuron excitation, if I understand correctly, but I do not understand if receptive fields (especially in the ...
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1answer
46 views

What are limitations on the number of objects the eye determine at a glance?

Take two people Sam (average human) and Jack. Jack says to Sam "I'm going to show you some skittles (or other object) and I want you to tell me as quick as you can how many I'm holding." He opens ...
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1answer
245 views

Ventral stream pathway and architecture proposed by Poggio's group

Please can you give me a very brief explanation about all functions in the ventral stream architecture summarized in this figure: This figure is from Serre et al.'s A quantitative theory of ...
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2answers
212 views

Why do our eyes “wrap” hue from UV to IR?

On the high-wavelength side of things, we see almost-infrared as reddish, with a slight tinge of magenta. On the low side, we see violet fading into the same magenta color. Why is that? You can see ...
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3answers
19k views

What is it called when one human eye is seeing brighter color than the other?

What is the name of a phenomenon where one of the human eyes is seeing brighter/more saturated color than the other? I can observe the same object from the same position while alternating which eye is ...
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1answer
77 views

Animal UV vision

It is reasonably well known that many species, such as bees and some types of birds as examples can see into the ultraviolet (UV). How is the structure of their eye different to humans to allow this? ...
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1answer
222 views

Perception of distant lights without glasses

I am fairly short-sighted and wear glasses pretty much all the time. Naively, I would expect that when I take my glasses off, the image I see should look very much the same as as a photograph that's ...
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2answers
77 views

Myopia as a microscopic superpower?

A few years back my Physics professor made a joke that his myopia (i.e., nearsightedness) gave him a "superpower" that allowed him to see close objects much more clearly than someone with typical ...
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1answer
234 views

Why do small fonts strain the eyes?

I understand that too much close reading will strain the ciliary muscles of the eyes. But what about small fonts? The contraction of the ciliary muscles is dependent on the distance not font size. In ...
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1answer
148 views

How much energy is required to blind someone?

As I understand the ravages of sunlight upon the (human) eye; the cause of ocular damage and blindness is too much energy delivered to the cones and rods that ultimately make up our eyes; so the ...
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30 views

Color perception vs shade perception demo

I can't seem to find one of the best demos I've seen of color vs brightness perception. It consisted of a rotating animation of earth made of red of bright red points on a dark green background. As ...
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62 views

The Operation of tuning in the S1 layer of ventral model

According to my previous question in ventral Stream pathway and architecture, I want now to get a brief example about how the S1 layer is constructed. In other words, how all the simple units are ...
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348 views

Why does vision go blurry after microscope use, and how to prevent it? [closed]

After using a binocular microscope recently for about 20 minutes, my vision went blurry and for an hour or so it was much harder to read small text. This occurs to a (far) lesser extent whenever I use ...
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1answer
93 views

What are dreams, biologically?

Falling asleep or states of subconsciousness does not stop the mind from making its own fictional images. These seem like sensations just like those received from human eyes. But, how do we define ...
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2answers
109 views

Parallels between pixelized image and the human retina

On Wikipedia it is explained that the human eye has a certain 'resolution'. Does this mean that the retinal image consists of pixels? If yes, what shape would these pixels have?
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2answers
192 views

What is the minimum eye?

What is the minimum eye which confers some evolutionary advantage? By minimum I mean anything less than this has no advantage whatsoever and therefore is not favored by natural selection. By eye, I ...
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60 views

Does “squinting” make you concentrate better on a logic test?

We have all had those moments of intense concentration on some tough exam, perhaps a college test or whatever... Why is it that when we squint, it feels like we can focus and concentrate better on ...
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2answers
121 views

Possibility of orthogonal view for a creature?

Just a pure curiosity: Does there exist a creature with an orthogonal view to the world instead of perspective? What would be an optical explanation for possibility/impossibility?
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1answer
437 views

Can visual acuity be improved?

Is it possible to completely cure myopia using natural methods (i.e. not with Lasik etc.)?. I have seen websites claiming that exercising the eyes will help improve eyesight. Is this true?
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1answer
30 views

How does myopia actually work?

This is potentially more or less a question about optics, but I've never been truly satisfied with any explanation that I've been given about Myopia. In fact, I almost can't even believe it. There are ...
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1answer
64 views

What is the difference between myopia and hyperopia?

In myopia the lens is bending the light too much even in the most relaxed state. Thus the image is produced in front of the retina. If the object comes closer the lens just adjusts a bit less than a ...