Which strabismus needs surgery? Strabismus is a disease of the extraocular muscles in which both eyes cannot look at the target at the same time. It can be divided into two categories: common strabismus and paralytic strabismus. The former is characterized by a temporal eye position, no eye movement disorder and no diplopia; while paralytic strabismus has limited eye movement, diplopia and systemic symptoms such as vertigo, nausea and unstable gait. The cause of strabismus is complex, and modern western medicine has no ideal method for those whose cause is unknown, except for the treatment of the cause and surgery. Clinically, except for the adjustable internal strabismus caused by hyperopia and convergence, which can be fully corrected by wearing glasses, all other types of strabismus require surgery. After strabismus surgery, a certain degree of fusion function will be beneficial to maintain the orthophoria, and the orthophoria can restore normal or certain degree of stereopsis in some patients, especially intermittent or recent onset patients can expect to obtain good binocular monocular function. Therefore, no matter what kind of strabismus, if conservative methods and training therapy are ineffective, surgery can restore the normal and coordinated function of the eye muscles, and the strabismus not only becomes orthotropic in the original position, but also synchronizes and agrees with each direction of movement, and can have binocular monocularity and stereopsis, and the surgery has no adverse complications. Patients with occult strabismus or intermittent strabismus often report eye fatigue, which seriously affects their work. Once conservative treatment (such as wearing negative lenses or trigeminal lenses) fails, surgery can also be considered. Surgical correction of eye position can reduce over-aggregation and eliminate over-adjustment, so that the symptoms of visual fatigue can be reduced and disappear. Some patients often exhibit compensatory head position in order to eliminate diplopia or improve visual acuity. A deviated head position and a heavy strabismus affect the aesthetics. If the surgery can resolve the compensatory head position and there are no complications, it can also be used as an indication for strabismus surgery. In paralytic strabismus or other non-common and common strabismus, patients often complain of diplopia, and when wearing glasses and conservative therapy are ineffective for more than six months, strabismus surgery can be performed to eliminate diplopia and restore binocular monocularity in one or more diagnosed eye positions. If the strabismus surgery can only make the eye position ortho or basic ortho to achieve certain cosmetic purpose, and the patient has understood before surgery, it can also be used as an indication for strabismus surgery.