A strabismus of 5 degrees is not considered serious and generally does not require treatment. Some congenital internal strabismus surgeries are followed by a deliberate effort to preserve 10 trigeminal degrees of microscopic internal strabismus in order to facilitate the establishment of peripheral fused stereopsis, which is measured in trigeminal degrees. The prevalence of strabismus is 3%, and severe strabismus can affect the development of visual function in both eyes. The earlier the age of correction of internal strabismus in children, the easier it is to restore visual function in both eyes, which is generally required around the age of 2. Children with exotropia are more likely to have intermittent strabismus, and if corrected at an older age, the chances of restoring visual function in both eyes are also high. Adults with secondary strabismus need to be treated conservatively first by examining the relevant causes, and then consider correction after the condition has been stable for more than 6 months if the causes are removed.