Strabismus is a disease of the extraocular muscles in which both eyes cannot look at the target at the same time. If there is a severe strabismus, abnormal eye position can be detected by direct vision. If the strabismus is of a milder degree, it is difficult to determine by this method. If there is a family history of strabismus, it is recommended that the child be examined at a hospital within 2 years of age. Specific examinations include: 1. examination of binocular visual function: mainly the same visual machine examination; 2. refractive examination: optometry after paralysis of the ciliary muscle with atropine to understand the presence or absence of amblyopia and refractive status; 3. determination of eye position and strabismus angle: determine the type of strabismus and check the size of the strabismus angle; 4. eye movement examination: determine the function of the extraocular muscles; 5. 5.Check to determine the paralysis muscle: red lens test or check by Hess screen method; 6.Pull test: ①passive pull test: it can understand whether there is mechanical pulling of extraocular muscles or spasm of muscles. ② Active contraction test: to understand the function of the muscles; 7. Examination of occlusion: quantitative determination with occlusion meter. Strabismus is mainly divided into 5 types according to eye position, namely, internal strabismus, external strabismus, upward strabismus, downward strabismus and occult strabismus. The details are as follows: 1. Internal strabismus: refers to the inward deviation of both eyes, commonly known as “opposite eye”. It is called congenital internal strabismus, and the angle of deviation is usually large; 2. Exotropia: refers to the outward deviation of the eye position of both eyes, and can be generally divided into intermittent and constant exotropia; 3. Upward and downward strabismus: refers to the upward or downward deviation of the eye position, which is less common than internal and exotropia. fusion control to maintain binocular monocularity, an imbalance of potential extraocular muscles and neural reflexes. It is common in the normal population and may develop into a dominant strabismus under certain conditions.