Single eyelids can appear as double eyelids in case of bad sleep or poor health, but this condition is very short-lived and fades quickly. There are also single eyelids into double eyelids that can be permanently preserved, mainly seen in the following two cases: 1. Double eyelids are dominantly inherited, if both parents are born with double eyelids, many children have double eyelids, but maybe the child’s double eyelids do not appear at the time of birth, and with The eyelid tissue is very thin, with little muscle and skin in the orbital septum and little fat in the orbital septum, and the upper eyelid is sunken, which can be seen in young people or in older people. In congenital sunken upper eyelid, the tissue also turns up when you look upwards, because there is less tissue between the upper eyelid and the orbit, and it can form a fold with the bone, which looks like a double eyelid mark, but it is a pseudo phenomenon because of the mechanics, the sunken upper eyelid causes no extra tissue to wrap around it, and there is a fold with the bone, which is mistaken for double eyelid, but as the sunken eyelid gets worse and changes with age , the double eyelid mark will become heavier and heavier.