What is Eye: Definition and 268 Discussions

Eyes are organs of the visual system. They provide animals with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and convert it into electro-chemical impulses in neurons. In higher organisms, the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in molluscs, chordates and arthropods.The most simple eyes, pit eyes, are eye-spots which may be set into a pit to reduce the angles of light that enters and affects the eye-spot, to allow the organism to deduce the angle of incoming light. From more complex eyes, retinal photosensitive ganglion cells send signals along the retinohypothalamic tract to the suprachiasmatic nuclei to effect circadian adjustment and to the pretectal area to control the pupillary light reflex.

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  1. R

    How Do You Calculate the Change in Focal Length for a Human Eye Lens?

    Homework Statement Suppose the lens in a human eye has far focal length equal to f0 = .0405 m, for distant objects to be in focus. (a) An object K is 1.72 m from the lens. How much should the focal length change to focus on the object K? (b) What is the magnification ( = image size divided...
  2. R

    Human Eye Optics - Answers Needed

    I reposted because I "bumped" this thread already with 2 replies and no one is answering.
  3. Danger

    Medical Is it Safe to Make Your Own Costume Contact Lenses Using Gelatine?

    Any opthalmologists or other occular medical experts out there? For decades, I've been making my own (usually elaborate) Hallowe'en outfits, including latex appliances. My avatar is one example of that. One thing that I've never been able to justify buying is costume contact lenses such as...
  4. W

    What is the Naked Eye Comet in Perseus?

    Hey guys. If it is clear out in your part of the World, look to the left of Delta and Alpha Perseus. There is a naked eye comet there. Look for a fuzz ball (it doesn't have a tail) that makes a point in a equallateral triangle with delta and alpha. It is beautiful in a telescope.
  5. M

    Distance of Hurricane from Grand Bahama Island: 104 km

    Homework Statement The eye of a hurricane passes over Grand Bahama Island. It is moving in a direction 60.0° north of west with a speed of v1 = 37.0 km/h. Exactly three hours later, the course of the hurricane shifts due north, and its speed slows to v2 = 27.0 km/h, as shown in Figure 3-30...
  6. Evo

    Is Your Workplace Stress Giving You Blepharospasm?

    My left eye has started twitching and it's making me crazy. Let's see, Medline says "The most common things that make the muscle in your eyelid twitch are fatigue, stress, and caffeine. Ok, guilty of all three. The caffeine I can control, I'm doomed on the other two. Would anyone like to...
  7. B

    What is the Relationship Between Focal Length and Distance in the Human Eye?

    Homework Statement Joe is hiking through the woods when he decides to stop and take in the view. He is particularly interested in three objects: a squirrel sitting on a rock next to him, a tree a few meters away, and a distant mountain. As Joe is taking in the view, he thinks back to what he...
  8. L

    Calculating the Distance of an Eye Chart: Tanya's Story

    Tanya is sitting in an optometrist’s chair, facing a mirror that is 2.25 m from her eyes. It the eye chart she is looking at is hanging a wall behind her head, 1.75 m behind her eyes. How far from her eyes does the chart appear to be?
  9. D

    Human Eye Structure: Investigating the Adaptive Function

    I've noticed that most animals have irises that fill the entire eye,but humans do not. Does anyone have an explanation for this? Does our sclera provide us something unique? What's the adaptive function one way or the other? This question has been bugging me for weeks. Thanks
  10. J

    Why Don't We See a Black Area When We Close One Eye?

    Hey In each eye there is a blind zone, and the eyes complete each others blind zone But now how come : when i close one eye, and open one i don't have any black in the view i have because the closed eye gives me a totally black image so on the side of opened eye : i should have a...
  11. A

    What color is best for the eye's resolving power?

    hi, i was just wandering what colour you see best in a why?, i mean if a room was to be flooded in red blue or green what would be the best for the resolving power of the eye. thank you very much, alex
  12. E

    What Can You Do About a Red Eye That Won't Improve?

    my left eyes got red since thursday and hasnt got well. it just gets worst when i work a lot with it but even though i don't work hard with it its still red! my right eye was red as well but a bit less and now it gets well totally but my left eye:confused:
  13. S

    Is it true you lose depth perception when looking out of one eye?

    I've heard this a lot - that you lose depth perception when looking out of only one eye. So I have to ask - is this true? When I try it everything looks exactly the same to me. :confused:
  14. T

    Medical How Does the New Bionic Eye Technology Restore Vision?

    http://www.newscientisttech.com/article/dn11200?DCMP=Matt_Sparkes&nsref=bionic-eye Title : Better 'bionic eye' offers new hope of restored vision A tiny electronic pad is placed onto the retina of one eye, so that the electrodes are in direct contact with the ganglion cells. Each of the...
  15. P

    Minimum Frequency Needed to Perceive Motion and Avoid Flickering

    I have read somewhere that motion on TV is really a series of still pictures presented very fast in succession but forgot the minimum number of still pictures / second to just allow us to perceive motion. What is that number? I also realize that power supplied to our homes is in the form of...
  16. E

    What's the farthest distance a star visible to the naked eye can still be seen?

    I was wondering how far away the stars are at night that can be seen by the naked eye. I would venture to guess that the galaxies that are billions of light years away must be seen with a high tech telescope. o| Hiram
  17. R

    From the corner of my eye, I misread the caption

    http://www.cbc.ca/arts/film/story/2006/11/16/clooney-people.html
  18. O

    Why Does Aiming Lower in Projectile Motion Miss the Target?

    Any help or simply reasons why my answer is incorrect would help greatly, thanks! Question: A projectile is fired from a horizontal spring-loaded gun aimed directly (along the line of sight) at a distant bull’s eye. Because of the pull of gravity during flight, the projectile misses and hits...
  19. Evo

    Why do primates have good eyesight?

    No, no, no. A friend sent this to me and it's just wrong. For one thing, it says dogs can't do brain surgery. Sorry, but my dog aka The Fruitbat" has been performing brain surgery on the cats for two years. He almost killed Dr Foofer. He drills holes in the sides of their heads, but I...
  20. $

    Eye Color Change: Will It Change With Age?

    hey all I've read a couple articles about eye color changing with ageing, well here's the thing i have brown eyes but my father which is 48 has light brown kind of hazel looking eyes and my mom brown.I was wondering sense I am 16 will my eye color change as i grow older?
  21. N

    LED Lights for Desk: College Student's Guide to Eye Strain Relief

    Hello. Does anyone here use and LED light for their desk? I am a college student and spend a lot of time at my desk reading. I get pretty bad eye strain from reading so much. I am thinking about getting one of these LED lamps. Also, does anyone use any other type of lamp that is better...
  22. M

    Rotations, Speed and Directions by eye (may be biology)

    I have a problem thinking about rotations. As we all know, it takes 360 degrees to complete a circle, 720 to do two rotations, 1080 for three full rotations, 1440 degrees for four and 1800 for five and so on. My question is, what is the amount of complete rotations a human eye can see in one...
  23. A

    Calculating Eye Resolution at Different Distances

    hey how would you work out resolution of an human eye at defeerent distances looking at 2 lines 0.25mm apart? cheers alex
  24. A

    Human Eye Resolution: Testing Light Levels

    hi, I've just done an experinemt to try and show the resolution of the human eye in different light levels. i did it by putting a 0.25mm apart slits in a tube then, behind it had an adjustbable light, then i moved the slit further back, and asked them to say if they could see the two slits...
  25. J

    Is There a Market for Smart, Adaptive Eyeglasses?

    OK - here's something I'd like to "see" before I'm worm food... Since a fairly modest percentage of the world population either now regularly uses or will eventually use some type of eye glasses, I'm surprised that there isn't a clamor to develop an affordable, "smart", variable/tunable focal...
  26. Mk

    Red Eye: Causes & Effects of Sclera Swelling

    When I get tired it looks like the blood vessels in my eye swell up, why? Are they in the sclera?
  27. V

    Aiming for the Bull's Eye: Accounting for Gravity

    an acher shatneds 40m away from his target. If the arrow is shot horizontally with a velocity of 90m/s how far above the bull's eye must he aim to compensate for gravity pulling down. No air resistance and I guess the target is level with him.
  28. Pengwuino

    Something I noticed about eye droppers

    I've noticed something a bit odd when I use an eye dropper in one of my labs. If I pull up water near the middle of the container, the water will fill up to a certain level. Now if I bring the eye-dropper down and touch the buttom (effectively putting it in a position to suck up the wall of...
  29. Math Is Hard

    FYI: Sharp paper corner in the eye = bad

    For any of you thinking of trying this at home, let me tell you this is not fun. I accidentally jabbed myself in the eye a couple of weeks ago, and after a couple of minutes of screaming in pain, I thought it was over. But last week, I started having this hard eye-twitch and some pain in my...
  30. N

    Can eye color change years after birth?

    I have no doubts that the eye colors of infants can change during the first several months of life. I've got my own proof in my sibling's (and my own) baby pictures. But what about years later, like adolescence or even adulthood? I know people who say their eye colors change depending on...
  31. 1

    Power and focal length of human eye

    I am extremely stuck on this question and do not know how to go about it. Could somebody help me? 1. (a) If the human eyeball is 4cm from lens to retina, what is the range of the power and focal length of the eye lens when focussing an object an infinite distance away and one at the normal...
  32. B

    Human Eye Resolution: Megapixels

    *What is the resolution (in megapixels) of the human eye?
  33. Z

    Solving a Word Problem: Preparing Special Eye Drops

    Word problem ! Hi , This is a Hw question i have am stuck on i don't know how to solve it ... A pharmacist is to prepare 16 milliliters of special eye drops for a glaucoma patient. The eye-drop solution must have a 5% active ingredient, but the pharmacist only has 10% solution and 1%...
  34. R

    News Venezuela to Provide Discounted Heating Oil and Free Eye Operations to U.S. Poor

    http://www.venezuelanalysis.com/news.php?newsno=1736
  35. S

    Eye Safety with Lasers: 15 mW & Fiber Coupling

    A question to people coupling lasers to optical fibers. What is the power and exposure time of laser beam directed in the eye which is considered dangerous? The ones I´m currently working with are 15 mW. Are there any ways to couple laser beam to a fiber without having to look into another end...
  36. S

    The Eye of the Beholder: Perception of Order & Events

    What if I said the only reason there is order and events is because we precieve it that way.
  37. N

    EYE: 3 cones- RGB: 255*255*255 HOw to convert

    The eye has 3 cones(RG,GY,B-component theory)...and bipolar cells( use the opponent theory). From these 3 types of cones how does the brain interpret the multiple of colors that occur...and how would one convert the wavelength(lambda) to RGB values or from RGB values to wavelength. for...
  38. Loren Booda

    Meeting Someone New: How Do You Make Eye Contact?

    When near another person, how do you meet their eye(s)?
  39. vincentm

    Hurricane eye + Nuclear missle

    Me and my friends are having a discussion on Hurricanes and the question came up if one was to detonate nuclear missile into the eye of a hurricane. what would happen ,some said the hurricane would get larger and more powerful. Is there some sort of answer to this? Maybe also a mathematical...
  40. wolram

    Neighbor has suddenly gone blind in one eye

    My next door neighbor has suddenly gone blind in one eye and has only blurred vision in the other, how can this happen so suddenly.
  41. Loren Booda

    Waking reflexive rapid eye movement

    We've all experienced REM. I notice that while awake, with eyes closed (or even open!), I can generate a sequence of images by allowing my eyes to integrate together the present image with my semiconscious lucid thoughts. For instance, I might visualize a vacation spot in the Black Forest and...
  42. wolram

    Exploring Crop Circles: Is There More Than Meets the Eye?

    I know that crop circles have been discussed to death but, has all the data gleaned from the investigations of these anomalies shown that they are hoaxes ie the node explosions?
  43. D

    Curious - a question concerning the eye.

    People are often attracted to eyes; however, do eyes diminish in beauty over time, like other physical attributes? If not, do marriages last longer among couples who both have, according to culture, beautiful eyes?
  44. D

    Can Gene Therapy Change Eye Color?

    Gene Therapy Can you use gene therapy to change eye color (or something other than that to permanently change eye color) or is gene therapy not available for that yet?
  45. K

    Do Dogs Have Different Eye Colors?

    Just a litle of curiosity as to whether or not dogs also have different eyed colors as humans ? Thank you
  46. A

    Calculating Speed of Human Eye Lens: f-stop = 4

    A human eyeball is about 2 cm long and the pupil has a maximum diameter of about 5 mm. What is the speed of this lens? f-stop = 2 cm / .5 cm f-stop = 4 is this it? I'm not sure if I found the right formula in my book thanks
  47. T

    Thanks for the present, I almost lost my eye.

    I got a airbrush for my birthday. I've never even held one before so I probably should have read the instructions. I don't have a compressor so I got a can of Propel, which appears to be full of butane. Anyway, I hooked the hose up to the can first, instead of to the airbrush first. As soon as I...
  48. Les Sleeth

    Eye Massage Corrects Farsightedness?

    When I saw the thread on eye meds, it encouraged me to ask something I've been wondering about. My wife has been nearsighted most of her life, and then at age 49 she started having trouble reading. She wears contacts, so her optometrist gave her a prescription for one contact for her...
  49. P

    Is the Lens of the Eye Living or Non-Living? Explained

    i just want to know, does the lens which present in the eye consider as living or non-living ? please can u provide me with a proper explanation. thenk you
  50. S

    Ideas about the eye sicknesses

    I have some ideas about the eye sicknesses. But, I couldn't find the maximum pressure for veins that are in eye sphere for STP. What do you think?
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