(a) Conservative treatment Early overcorrection within 1~2 weeks of ectropia surgery, small degree (10~15△), mostly temporary, gradually decrease or disappear with time, no treatment within 2 weeks. If the internal strabismus is greater than 17 △ in the early stage after exotropia surgery, the chance of secondary internal strabismus will be greatly increased in the long term. If persistent diplopia occurs after surgery or if the strabismus deviation does not improve after 2 weeks of observation, intervention should be performed to establish fusion and reduce the deviation. In young children with poor binocular function and immature visual function, if the overcorrection exceeds 10△, conservative treatment should be performed by (1) suture adjustment; (2) selective masking, trigeminal therapy, local spot pupil reduction, and refractive correction. In the case of combined hyperopic adjustment factors, early removal of the adjustment factors is generally chosen as the method of hyperopic refractive correction. Studies have concluded that over-adjustment and high AC/A are the causes of internal strabismus. Patients with intermittent exotropia who have a large difference between near and far strabismus may have high AC/A. If these patients have combined hyperopia, which is not corrected after surgery, the strong accommodation and AC/A are not corrected after surgery or overcorrection, which aggravates the occurrence of internal strabismus. After 4 weeks of treatment with alternating masking, trigeminal treatment, and pupil reduction drops (echolesters, diethylphosphonothiocholine agent), 72% of patients with near and far strabismus were less than 10△, and only 6% of patients were greater than 20△, requiring secondary surgery. Therefore, the recent conservative treatment of secondary internal strabismus after external strabismus surgery is very important. In addition, some patients may have secondary strabismus caused by abnormalities of central regulation function after surgery, which requires neurological consultation to exclude brain disorders. (B) Surgical treatment Surgical principles, no abduction limitation, previous bilateral retroversion of the external rectus muscle, internal strabismus surgery is appropriate to use the internal rectus muscle retroversion of both eyes. If the external rectus muscle of one eye is receding and the internal rectus muscle is shortened, internal strabismus surgery should be performed in the contralateral eye. In patients with limited abduction, surgery for internal strabismus should be performed on the eye where the first surgery was performed. If there is no limiting factor in the passive traction test, the external rectus muscle is explored to strengthen the surgery; if there is a limiting factor in the internal rectus muscle, the internal rectus muscle is separated and regressed; if the external rectus muscle is not found during surgery with a larger degree of internal strabismus, the vertical muscle needs to be transposed to replace the external rectus function. The surgical volume was calculated exactly according to the strabismus degree of the second internal strabismus examination.