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  • From blind spots in our retinas to an eye colour that didn't exist until recently, we

  • count 40 bizarre facts about our own eyeballs 40

  • Human eyes blink an average of 17 times a minute. This equates to 14,280 times a day

  • or 5.2 million times a year.

  • 39 Blinking removes debris from the eye’s surface

  • by spreading tears over it. The tears help moisten and lubricate the eyes. They also

  • have anti-bacterial properties.

  • 38 Eyes heal quickly. With proper care, corneal

  • abrasions can repair within 48 hours.

  • 37 Newborns don’t produce tears. While they

  • do make crying sounds, their tears don’t start flowing until they are 4–13 weeks

  • old.

  • 36 Approximately six in a thousand people are

  • born with heterochromia iridus. This is a condition where the person’s eye are two

  • different colours.

  • 35 A shark’s corneas are very similar to those

  • of humans’. Because of this similarity, shark corneas have been used as replacements

  • in human eye surgeries.

  • 34 Schizophrenia can be diagnosed with 98.3%

  • accuracy using a simple eye test that tracks eye movement abnormalities.

  • 33 Dogs are the only species other than humans

  • that seek visual cues from other individualseyes. Dogs only do this when interacting with

  • humans.

  • 32 ‘Impossibleorforbiddencolours

  • are colours that are too complex for the human eye. Although it is impossible to perceive

  • them under regular viewing conditions, they can be seen in special circumstances

  • 31 The pupil of your eye expands as much as 45%

  • when you look at someone you love. Similarly, a person's pupils may dilate when looking

  • at someone they are sexually attracted to.

  • 30 It's possible for your eyes to be sunburned.

  • Prolonged sun exposure eventually leads to a thickening of the eye tissue, which might

  • require eye surgery.

  • 29 Your retinas perceive the outside world as

  • upside-down. The brain must then flip and make sense of the image.

  • 28 Eye colouror our perception of itcan

  • change with lighting conditions. Neither blue nor green pigments are present in the human

  • iris or ocular fluid.

  • 27 Octopus eyes have no blind spot and evolved

  • separately from vertebrate eyes. This is an example of convergent evolution.

  • 26 Up until 10,000 years ago, brown was the only

  • known human eye colour. This changed when a person living by the Black Sea developed

  • a genetic mutation that made their eyes blue.

  • 25 If one red eye appears in a flash photograph,

  • there is a chance this person has a strand of treatable eye cancer called Leukocoria.

  • For this test to work, both eyes must be looking directly at the camera.

  • 24 Human retinas cannot detect the colour red.

  • Ourredreceptor only detects colours in the yellowgreen spectrum; thus, our

  • brains must combine multiple signals to perceive red.

  • 23 It’s possible for eyesight to improve with

  • age. However, this can be a sign that something is wrong with a person’s overall health.

  • 22 Your eye’s lens sits behind the iris and

  • is roughly the size of an M&M candy. Developing a cataract in your eye is like developing

  • a peanut in that M&M.

  • 21 Our peripheral vision has a very low-resolution,

  • and is almost black-and-white. But we don’t notice this because our eyes move and fill

  • in the details.

  • 20 The visual centres in the brain are located

  • at the lower back part of your head. This is why people with head injuries can sometimes

  • experience temporary blindness.

  • 19 Tetrachromacy is a rare genetic mutation occurring

  • in 2% of women. It gives them an extra retinal cone, allowing them to see 100 million colours.

  • 18 Staring directly into the sun will burn a

  • spot in the retina, causing permanent blindness. This is called solar retinopathy.

  • 17 Iris pigmentation develops over the first

  • year of life. This means our eyes are darker now than they were when we were newborns.

  • 16 Our eyeballs grow just like the rest of our

  • body. At birth, they are roughly 16 centimetres wide; by puberty, they will have grown to

  • a maximum width of 24 millimetres.

  • 15 ‘20/20 visionisn’t perfect vision.

  • It simply means a person can see 20 feet in front of them with the same clarity as a normal-visioned

  • person.

  • 14 If youre short-sighted, your eyeball is

  • longer than normal. If youre farsighted, it’s shorter than average.

  • 13 The composition of tears differs depending

  • on whether youre crying, yawning or have an irritant in your eye.

  • 12 In order for you to see, your brain must interpret

  • the signals it receives from your eyes. Optical illusions occur when there are discrepancies

  • between what your brain and eyes perceive.

  • 11 Our eyes constantly make tiny involuntary

  • jerking movements calledmicrosaccades’. These stop objects from fading from our vision.

  • 10 Although the human eye is thought to be capable

  • of detecting around 10 million unique colours, they only have the capacity to detect 30 shades

  • of grey.

  • 9 The refractive power of a human eye lens is

  • approximately 18 dioptres, roughly one third of the eye’s total power. This makes an

  • eye’s lens quicker than a camera’s.

  • 8 Human eyes contain 107 million cellsall

  • of which are light sensitive. Seven million cones help with the detection of colour and

  • detail, while 100 million rods allow us to distinguish black and white. This means that

  • less than a tenth of our visual receptors detect colour.

  • 7 Human eyes have a small blind spot in the

  • back of the retina where the optic nerve attaches. We don’t notice this hole in our vision

  • because each eye works together to fill the other’s blind spot.

  • 6 The human eye can only make smooth (non-saccadic)

  • motions if it’s tracking a moving object. A person cannot will their eye into making

  • a smooth motion.

  • 5 Pirates used eye patches to quickly adjust

  • their eyes from above to below deck. They would have one eye trained for the bright

  • light and the other for dim, below deck lighting.

  • 4 All kittens are born with blue eyes, which

  • if they are going to do sowill change colour by around 8 weeks of age. 65–85%

  • of all white cats born with blue eyes are deaf.

  • 3 To detect nocturnal predators, many animal

  • species will sleep with one eye open. One hemisphere of their brain is asleep while

  • the other is awake.

  • 2 Our two eyes give us depth perception. Comparing

  • two images allows us to determine how far away an object is from us.

  • 1 People generally read 25% slower from a computer

  • screen compared to paper. Reports also suggest that late-night screen-reading may be damaging

  • to our eyes.

From blind spots in our retinas to an eye colour that didn't exist until recently, we

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あなたの目について知らなかった40のこと (40 Things You Didn't Know About Your Eyes)

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    SylviaQQ に公開 2021 年 01 月 14 日
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