As an editor of 600 degrees myopia, I have always felt that contact lenses are a great invention. Especially when you are sweating in the summer and entering the warm indoors from the outside in winter - look at your companion wearing glasses, and then think about the contact lenses you wear, and feel more energetic.
However, many people have some taboos on contact lenses. For example, I once taught me to say, "After all, it is directly in contact with the eyes! How can it be harmless! What to do if the cornea is thin!"
Contact lenses do have an effect on corneal endothelial cells. A study of 126 cases of wearing soft contact lenses in Japan found that people in the same age group did have lower density of corneal endothelial cells than those who did not wear contact lenses.
This effect of contact lenses on the cornea may be due to its obstruction of the exchange of corneal endothelial cells with the outside world. There are no blood vessels in the cornea. The nutrients, oxygen, and metabolic waste required by the cells are exchanged through the aqueous humor inside the cornea and the tears outside. Wearing contact lenses makes this exchange impossible, and cells may be damaged by hypoxia. At the same time, the carbon dioxide produced by the metabolism of endothelial cells cannot be removed and retained in time, which may have a toxic effect on cells. Therefore, the shorter the time of using the contact lens every day, the less likely the corneal endothelial cells are damaged. Fortunately, in people who use less than 12 hours a day, the density of corneal endothelial cells is greater than 2000 per square millimeter.
Studies have found that the incidence of corneal epithelial damage in people wearing contact lenses during the day and night is 3 to 10 times that of those who wear only during the day. So try not to wear contact lenses overnight. Even if there are some types of contact lenses that can be worn overnight, they should not be worn overnight in non-special circumstances.