Why the eyes do not freeze?
When it hits frost, we are in a hurry to put on the mittens, so as not to frozen hands, and tie a scarf higher to close the nose and cheeks. Frostbite does not threaten eyes only. Although at first glance it may seem strange. Not only is the vitreous body, occupying about ⅔ the volume of the eyeball, consists of a water of about 99%, so also the cornea of the eye is constantly moistened.
Moreover, there are no thermistors in the eyes, which are sensitive to changes in ambient temperature and send corresponding signals to the brain. Consequently, the cold eyes do not feel. It is logical to assume that with a strong frost, they should turn into ice. But this does not happen. Why? Eyes have reliable protection.
First, it is a tear film. It consists of three layers: adipose tissue, mucous and water. It is a water layer that protects the eyes from cooling, since it contains not clean water, and salty. High concentration of salts in tears allows them to not freeze even at low temperatures.
Secondly, the eyeball is very conveniently located. Most of it is in the deepening of the skull – the eye, and outside it covers the eyelid.
Finally, thirdly, the human body has a powerful thermoregulation system. It starts work every time the ambient temperature begins to differ from the optimal for a person. When frost, the bloodstream in the blood vessels is enhanced and brings additional heat to the eyes, not allowing you to freeze.
As for animals, the way to protect their eyes from supercooling depends on class. So, in mammals of the structure of organs of vision is identical to human. Therefore, there is no fundamental difference in thermoregulation.