We often see people around us with two eyes that are not the same size, but maybe you have never wondered why their eyes are not the same size? Is it natural? Or do they have some kind of disease? Don’t underestimate the “size of the eye”, there are countless possibilities, and some of them are diseases that need to be treated, even major diseases that require surgery as soon as possible. First, ptosis in one eye can lead to large or small eyes. Our eyelids can open and close freely because of a muscle called the levator muscle. This muscle is like a leather band and uses its elasticity to be responsible for opening and closing the eye. If this muscle loses its elasticity due to congenital abnormalities or traumatic injury, the eye will never open wide. And in severe cases, the eyelid will block the vision and affect the development of vision. This is when we need to intervene surgically to make the eye open wider. Secondly, hyperthyroidism can cause large and small eyes. In people with hyperthyroidism, because of the growth of fat behind the eyeball and the thickening of the muscles responsible for turning the eyeball, along with the atrophy of the eyelid muscles, the eyeball can protrude so much that it feels like it is about to fall out of its socket. If this protrusion continues to worsen without treatment, it can eventually lead to loss of vision or even loss of vision. Another common disease that causes large and small eyes is a tumor behind the eye. As the tumor grows, the eye will gradually protrude and become more and more severe due to the pressure of the tumor. In some cases, the tumor may also compress the optic nerve and cause the loss of vision. It must be removed surgically as soon as possible. Human body is an intelligent machine with fine structure and perfect symmetry. Any abnormality requires high attention. Especially the ever-changing asymmetry and abnormal changes must have their reasons and need to be treated with caution.