The weather is abnormal. Why can't our eyes feel cold?

When the weather is cold, the human body will feel cold, but have you found that people's eyes don't feel cold?

The structure of human eyes is very complicated. Cornea, aqueous humor, lens and vitreous constitute the refractive system of eyeball, which is equivalent to the objective lens of camera. Light enters through the refractive system of the eyeball and is imaged on the retina. The eyeball is similar to a sphere, including its wall, lumen, contents, nerves, blood vessels and other tissues, which are all protected by eyelids.

The reason why the human body can distinguish between hot and cold is because there are receptors on the skin of the body surface, which can feel the changes of hot and cold. The receptors are distributed in "points", including "cold points" and "hot points".

However, there are no "cold spot" and "hot spot" receptors on the surface of cornea and sclera of human eyeball, and the receptors are rarely distributed on conjunctiva and eyelid skin. Therefore, when the temperature of the eye (eyeball) drops with the external temperature, the brain will not guide the temperature of the eyeball because there is no sensor to report to the brain. As for conjunctiva and eyelid skin, because there are few sensory organs, the feeling of external cold and hot changes is extremely slow, so it will not be disturbed by external cold and hot changes.

Just because there are few receptors in the eyes that feel the changes of cold and heat doesn't mean that the eyes are really not afraid of cold. In fact, winter is the season of high incidence of some eye diseases, especially the elderly with degraded physiological functions, whose eye tissues are fragile and more prone to problems.

People's blood vessels will gradually become "brittle" with age, that is, arteriosclerosis. When the elasticity of blood vessels is not good and they are stimulated by cold weather, the blood vessels will contract, the lumen will narrow and the blood flow will slow down, thus forming a thrombus. In addition, cold temperatures may induce glaucoma, and may aggravate diseases such as tears in the wind and dry eye. Chun Wong, a senior teacher of No.2 Middle School in Chaisang District, Jiujiang City, Jiangxi Province, made a scientific investigation.