Infantile internal strabismus is a common type of internal strabismus, also known as congenital internal strabismus, accounting for 28%-54% of all internal strabismus, with an incidence of 1% in the general population. The onset of the disease is within the first 6 months of life, usually between 2 and 4 months. Etiology: Current studies suggest that congenital motor fusion disorders may be an important cause. Clinical features 1. The strabismus angle is quite large, 40△-60△ on average, 80△-100△ is not uncommon. 2. Mild refractive error, but generally not more than 2.00D hyperopia; 3. 35-70% of infants with internal strabismus will have amblyopia in the future, timely correction of strabismus can avoid the occurrence of amblyopia. Those who do not have the conditions for surgery should be instructed by the physician to change the monocular strabismus into alternating strabismus by masking. 4, accompanied by other eye movement abnormalities: upper oblique muscle paralysis, lower oblique muscle overfunction, separated vertical strabismus, occult nystagmus, etc. 5.It is difficult to obtain normal binocular vision function and stereopsis. Treatment 1. Correction of refractive errors of clinical significance. It is best to correct all children with internal strabismus with hyperopia over 2.50D. 2. Treatment of amblyopia; 3. Correction of eye position: surgical treatment, preferably within one year of age, usually no older than two years. Prognosis: The prognosis is poor if treatment is started after two years of age. Prognosis may be better if treatment is started before two years of age. Surgical treatment of infantile internal strabismus in babies born at 6 months of age.