What is the reason for children's cross-eyes?

Cross-eye is an eye disease that often occurs in children. To put it simply, cross-eye is a form of strabismus. Some people say that cross-eyes cannot be cured. This makes sense when medical technology is underdeveloped. However, with modern medical technology, cross-eyes can be cured. But for patients, the only problem is that the disease cannot be cured. So, what are the reasons why children cross their eyes?

Cross-eyes refers to the situation where the pupils in the middle of the eyes are naturally or artificially moved closer to the center, making them look like two chickens fighting. Hence the name cross-eyes, also known as crossed eyes. When a normal person looks at the same object with both eyes, images of the object are formed on the retinas of both eyes and overlap in the visual center of the brain to become a complete, three-dimensional single object. This function is called binocular single vision. However, infants and young children are easily affected by external factors during the process of developing binocular single vision, causing one eye to focus on a target while the other eye deviates and cannot look at the same target, thus resulting in strabismus. In medicine, the condition of the eyes looking inward when looking at an object is called esotropia, which is commonly known as "cross-eyed".

Cause

(1) Imperfect development: Children, especially infants and young children, have incomplete binocular vision function and cannot coordinate the extraocular muscles well. Any unstable factors can cause strabismus. Human's monocular vision function is gradually developed after birth. Just like the visual function, this function is established by repeatedly receiving stimulation from clear external images, and gradually develops and matures. Infants only have gross fusion image 2 months after birth, and the establishment of precise fusion image function will continue until after 5 years old. Stereoscopic vision is established at the latest, and it is close to that of adults at 6 to 7 years old. Therefore, the period before the age of 5 when binocular single vision function is not yet perfect is a high incidence period of strabismus in children.

(2) Congenital abnormalities: This type of strabismus is mostly caused by congenital abnormalities in the position and development of the extraocular muscles, abnormal development of the extraocular muscles themselves, incomplete differentiation of the mesoderm, poor separation of the eye muscles, abnormal muscle sheaths and fibrosis, and other anatomical defects or paralysis of the nerves that control the muscles. Some cases are due to the use of forceps during delivery, which causes damage to the baby's head and face, or the mother's excessive force during delivery, which causes increased intracranial pressure on the fetus and produces punctate hemorrhages in the brain. The bleeding happens to be in the nerve nucleus that controls eye movement, causing paralysis of the extraocular muscles. In addition, there are also genetic factors. Strabismus is not inherited by all members of the family. This defect is often indirectly passed on to the next generation of children. Generally, strabismus that occurs within 6 months after birth is called congenital strabismus. It does not have the basic conditions for establishing binocular vision and has the greatest harm to the development of visual function.

(3) The characteristics of eye development make children susceptible to strabismus: because children’s eyeballs are small and their eye axes are short, they are mostly farsighted. Also, because children’s corneas and lenses have strong refractive power and their ciliary muscles have strong contraction power, they have strong accommodation power. Such children need more accommodation power to see objects clearly. At the same time, their eyes turn inward forcefully, resulting in excessive convergence, which can easily cause esotropia, a type of esotropia called accommodative esotropia.

(4) Insufficient control of the eye movement center: If convergence is too strong or abduction is insufficient, or both exist at the same time, esotropia will occur; conversely, if abduction is too strong, convergence is insufficient, or both exist at the same time, exotropia will occur.