The most common strabismus: common strabismus, which is characterized as follows: (1) no obstacle to eye movement; (2) no change in the strabismus angle when gazing in any direction; (3) equal or ≤5° difference in strabismus angle when gazing in the left and right eyes respectively, when it should be noted that the strabismus angle is not equal when gazing in both eyes respectively; (4) ≤10° difference in strabismus angle when gazing upward and downward; (5) no organic lesion in the extraocular muscles and their nerves and nuclei. (5) no organic lesions of the extraocular muscles and their nerves and nuclei. The common strabismus includes occult strabismus, common internal strabismus, and common external strabismus. Cryptotropia is a potential eye position deviation, and this tendency can be controlled by the fusion reflex, so that no eye position deviation occurs and the monocular function is maintained, and only when some artificial method breaks the fusion, the eye position deviation occurs. Common internal and external strabismus can also be understood as a kind of dominant strabismus, and the direction of the deviation of the two eye positions is exactly opposite. (2) Non-common strabismus: clinically, it mainly refers to paralytic strabismus, which is characterized by: (1) diplopia, visual confusion, vertigo; (2) eye movement disorders; (3) the strabismus angle is larger than that of the healthy eye when the eye is gazing; (4) the strabismus angle increases in the direction of the action of the paralytic muscle; (5) there is often an abnormal head position; (6) there are lesions in the extraocular muscles themselves or their nerves and nuclei. 3, A-V syndrome: is a subtype of horizontal strabismus, because accompanied by vertical paralysis, when the upward and downward gaze, the horizontal strabismus changes significantly, the international can use the letter A and V form to name this strabismus. The direction of the opening of the two letters indicates strong separation or weak collection of the two eyes, and the direction of the tip of the letters indicates strong collection or weak separation. 15%-25% of strabismus combined with A and V signs. 4.Special type of strabismus: caused by many different special causes, there are more than 10 kinds. 5. Rotational strabismus: It is a rotational strabismus of the front and back axis of the eye. There are also people who classify strabismus into internal strabismus, external strabismus, vertical strabismus, etc. according to the morphology of strabismus.