Cock-eye, also known as esotropia, is usually caused by developmental abnormalities or high farsightedness. Under normal circumstances, both eyes are parallel, but when there is an abnormality in the position of the eyes, the direction of vision will be crossed or separated. If the direction of vision of both eyes is crossed, the eyes will be inwardly squinted, which is also called cross-eyed. The most common cause of esotropia is a lack of coordination between the extraocular muscles in both eyes due to congenital developmental abnormalities, which is usually present in childhood and may worsen with age. High farsightedness is also a cause of strabismus, which is due to the fact that patients with high farsightedness need to use more adjustment force to see things, thus inducing more convergence reflexes, causing both eyes to converge to form strabismus. Patients should go to the ophthalmology department of the hospital for examination in time, and after clear diagnosis, actively cooperate with the treatment, so as to avoid adverse effects on visual function.