Causes of strabismus_What causes strabismus

If you feel that the other person cannot look you in the eye when you are talking to him/her, and if you feel that he/she is looking at someone else even though he/she is clearly looking at you, this is strabismus. Strabismus is generally caused by acquired factors. Many babies' eyes are always tilted to one side when they are just born, which leads to uneven muscle strength inside and outside the eyes, resulting in strabismus. Strabismus can be adjusted and corrected through certain methods.

Slanting of the eyes is medically called "strabismus", slanting towards the nose is called "esotropia", and slanting towards the ear is called "exotropia". Some children are born with good eyesight, but when they are three or four years old, their eyes suddenly become squinting. Some people said that it was a strange wind; some people said that it was due to the strong sunlight, and so on, but in fact, none of them were true.

Normal people's eyes can see far and near, look left and right, and move up and down, and the two eyes always move together. This is mainly the result of the traction of six muscles around each eyeball, which work together and closely cooperate with each other. If the contraction force of a muscle is too strong or too weak and cannot be balanced with its antagonistic muscle; or if one muscle is paralyzed and loses its function, the pulling force of the eyeball will also lose balance, and the eyeball will deviate to one side.

The causes of strabismus are as follows:

(1) Irregular development:

Children, especially infants and young children, have incomplete binocular vision function and cannot coordinate the extraocular muscles well. Any unstable factors can lead to the occurrence of 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 abnormal development of the position 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) Characteristics of eye development make children susceptible to strabismus:

Because children have small eyeballs and short eye axes, most of them are farsighted. Also, because children's cornea and lens have strong refractive power and ciliary muscle contraction force, 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 eye movement center:

If the convergence is too strong or the abduction is insufficient, or both exist at the same time, esotropia will occur; conversely, if the abduction is too strong and the convergence is insufficient, or both exist at the same time, exotropia will occur.