The weather is abnormal, why can’t our eyes feel the cold?
When the weather is cold, the human body will feel cold, but have you ever noticed that human eyes do not feel cold.
The structure of the human eye is very complex. The cornea, aqueous fluid, lens and vitreous fluid constitute the primary axis refractive system of the eyeball, which is equivalent to the objective lens of a camera. Light enters through the refractive system of the eyeball and forms an image. in the retina. The eyeball is approximately a sphere, including the eyeball wall, intraocular cavity and contents, nerves, blood vessels and other tissues, and is protected by the eyelids.
The reason why the human body can distinguish between hot and cold is because there are receptors on the surface of the body that can feel changes in hot and cold. The receptors are distributed in "points", with "cold spots" and "hot spots" divided.
There are no "cold spot" and "hot spot" receptors on the surface of the solid internal organs of the cornea and sclera of the human eyeball. The receptors are rarely distributed on the conjunctiva and eyelid skin, so when the eye (eyeball) When the temperature of the eye drops with the outside temperature, because there are no receptors to report to the brain, the brain will not direct the cooling and heating of the eyeballs. As for the conjunctiva and eyelid skin, because they have few receptors, they are extremely insensitive to changes in external cold and heat, so they will not be disturbed by changes in external cold or heat.
The number of receptors in the eyes that sense changes in cold and heat is small, and the inability to sense hot and cold does not mean that the eyes are really not afraid of cold. In fact, winter is the peak season for some eye diseases, especially the elderly with degraded physiological functions. The eye tissues are fragile and more prone to problems.
Human blood vessels will gradually become "brittle" with age, which is called arteriosclerosis. When blood vessels have poor elasticity and are stimulated by cold weather, the blood vessels will constrict, the lumen will become narrow, and the blood flow will slow down, thus forming thrombus. In addition, cold temperatures may induce glaucoma and may aggravate diseases such as wind tears and dry eye syndrome. This article was scientifically reviewed by Huang Shaohua, a senior teacher at No. 2 Middle School in Chaisang District, Jiujiang City, Jiangxi Province.