Human eye. Español: Iris de un ojo humano. El ojo recibe los rayos de luz que provienen del exterior y los transforma en impulsos nerviosos en la retina, formada por las células de la visión conocidas como conos y bastones. فارسی: چشم انسان Français : Œil humain Italiano: Occhio umano. ქართული: ადამიანის თვალი Русский: Глаз человека Türkçe: İnsan Gözu 中文: 人眼 (Photo credit: Wikipedia)
Perhaps the most complicated and incredible feat of biological engineering in the natural world, the organ which allows creatures the ability to make visual sense of their surroundings is a wondrous and amazingly beautiful thing, but rarely given the accolades it deserves. One only sees nature’s most wonderful creations in your mirror-image, the reflection of the eye, a feat of biological technology more complex than any engineer could ever produce artificially. Human fascination with the eye is so powerful that defective eyes have traditionally been viewed as harbingers of bad luck or evil.
19th century people would customarily spit three times on making eye contact with someone who had a squint, cross-eyed people were seen as ill omens, and those rare women with double pupil eyes were automatically witches. The eye is loaded with powerful symbolism such as the Masonic All Seeing Eye on U.S. one dollar bills. Representative, we are told, of God’s constant vigilance, yet full eye contact with others is something people tend to avoid, the mirrors to the soul, so-called often giving far too much away for comfort.
Staring at someone is rude and aggressive, by far the most threatening thing in nature, and certain species even display false eyes to frighten off attackers, yet eyes are never still, the focus changing many times a second, keeping visual signals to the brain fresh and immediate. REM, or rapid eye movement occurs several times during sleep, eyes moving wildly beneath closed lids, probably as a direct result of the brain purging itself, which could account for strange dreams as well, but no one really knows, though our continued mental good health can depend on REM
The most sophisticated camera cannot possibly ever emulate what the eye makes seem simple, a lens focusing an image on light sensitive cells in the retina which convert these to electrical signals sent for interpretation by the brain, but do not be deceived by first appearances. With thousands of different types highly specialized cells within the eye, over 150 million of them hard at work the complexity is staggering. An eye lens is flexible and constantly in motion, the retina unlike any photographic plate. with an astonishing 10 layers of nerve cells, interconnected with mind-boggling complexity. These cells switch each other on and off, edit visual signals into categories like color, shape and movement so that messages get more quickly and easily dealt with.
Eye colors and shapes fascinate people, shade dependent upon certain pigment levels within the iris. Pigment level at the back is constant, but it front levels vary. People with darker eyes tend to respond faster to visual and auditory stimuli than lighter- eyed counterparts, seen clearly in the animal world, dark eyed predators chasing down prey, while light eyed ones lay in wait. These differences are thought due to neuromelanin which speeds up electrical signals to the brain, developing from birth. All white babies look blue eyed because no front pigment is present. The pigment melanin builds up at the front of the iris, the darkness of the eye dependent on the amount. the eye color being fixed by age six.
Schematic diagram of the human eye in english (Photo credit: Wikipedia)
The eye outer chamber is full of clear, watery fluid, the crystalline lens concealing a larger chamber full of a soft jelly like albumen. The retina is not black at all, the secret being in the structure of the retina covering cells and the pigments they contain, basically reflecting very little light and appearing black to observers. That incredible complexity gives the eye such a universal appeal, any medical diagram of it looking very much like an astronomer’s map of some alien world, and the component names seem equally alien, such as Descemet’s membrane, the Zonule of Zinn, the Hyalocytes of Balzacs and the Canal of Sclemm.
Perhaps not surprisingly, the fastest human body reflex is that of the cornea at a mere tenth of a second, reflecting vital extreme sensitivity, humans unconsciously blinking every 2 to 10 seconds to keep the surface of the eye clean and moist. and clean. research has now made it possible to bounce light off the cornea and monitor the reflections via computer, very useful in helping create devices enabling severely handicapped people to control appliances and even synthesize speech.
Eye tracking, as this technology is called, also enables jet fighters pilots the hands-free capability to target and fire weapons.. Technology and research are working hard at developing artificial eyes able to be directly connected to optic nerves, meaning that within a century, blindness could easily become a thing of the past. Evolution has provided the creatures of earth amazing ability to make sense of their surroundings, , but surely the most wondrous and valuable gift of them all was the utterly incredible eye.
I have been writing for pleasure for half a century, but only started writing for money around 1994. Since then I have had a few thousand articles, stories and poems published on line and in print all round the world.
I am now 63 years old, male, from Burnley in the UK, and apart from writing, I love to read - mainly crime thrillers, conspiracy theory books and science fiction, though I also love films, gardening and chatting with my wife who is also my best friend.
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