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Eye color from green to dark brown is affected by melanin contained in the iris. If this pigment reaches a certain amount, the eyes have a brown color. If no – blue collagen appears through melanin.
Pedigree
All blue-eyed people have one common ancestor. Given color the eye, by the way, is much younger than hazel, and therefore is recessive, that is, genetically weaker. About 6-10 thousand years back he appeared as a result of a mutation. In itself she is neutral, that is, does not affect the survival of the individual.
Quantitative indicators
Our retina contains 107 million photoreceptors. Of which 100 million – sticks with which we distinguish objects in the dark, and 7 million – cones responsible for our perception of color. IN there are three types of cones in the human eye, their maximum sensitivity falls on red, green and blue areas spectrum. It is curious that in the eyes of some insects there are up to 16 types of cones. I would like to see the world at least once by their eyes! ..
Normative indicators
We often hear that a person’s vision is For example, minus one and a half. What does this mean and what vision is normal? Per unit is one hundred percent vision. Human, having it is able to read 10 rows from the Sivtsev table. Therein if someone sees 5 lines, his visual acuity is minus 0.5.
Adaptation
The structure of the human eye is such that it sees this world upside down. It’s no secret that newborns perceive reality upside down, and subsequently their brain adapts and begins “show” a normal picture. If a person wears glasses with special lens system, the image will turn over again – on a few days until the brain “puts” everything in its place. Take off such glasses – the world will turn over again for a while …
Reflexes
To protect our eyesight and moisturize the eyeball, by nature a blinking reflex is provided. For a day, a person blinks from 10 to 40 and even 50 thousand times. Sometimes blinking is a consequence psychological processes, not without reason they say: if someone often blinking, it means he is lying or very worried.
Speed
The fastest muscle in our body is the ophthalmic circular muscle that provides blinking and movement of the eyelid. Her work saves our eyes are from dust and other small particles. Thus, reflexive squinting at such a high speed saves human ability to see.
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