What is the best age to operate on a child with strabismus? It depends on the type of strabismus. In the case of internal strabismus, especially congenital internal strabismus, which means that the child develops within 6 months after birth, we will do basic examinations such as optometry to exclude factors such as amblyopia, and generally recommend that the child be operated around the age of two. For intermittent strabismus, such as the most common intermittent exotropia, the child’s eyes are not in the strabismus state for a long time, and the frequency is not high, which means that the child is not always in the strabismus state, so the child can wait until he/she is 4 years old before surgery. In the case of vertical strabismus, especially if the child has a compensatory head position, that is, a tilted head, the earlier the surgery is performed, the better. It is difficult to correct a child’s long-term head tilt because it can form a habit. Therefore, if a child is found to have vertical strabismus and a tilted head, surgery should be done as long as the child can cooperate with the examination, usually around one year old.