Strabismus (squint) refers to the inability of both eyes to look at the target at the same time, and can be divided into two categories: common strabismus and non-common strabismus. Common strabismus is characterized by the absence of eye movement disorders and equal strabismus in the first and second eye positions; paralytic strabismus, on the other hand, has limited eye movement and diplopia, which can be congenital or caused by trauma or systemic diseases. Clinical manifestations In strabismus, because of improper eye position, the image of an object falls on the central recess of the retina in the normal eye, but outside the central recess in the strabismic eye, so that double vision occurs. 1. Internal strabismus The position of the eye is skewed inward. It is called congenital internal strabismus when it occurs from birth. The angle of deviation is usually large. Acquired internal strabismus is divided into moderate and non-moderate. Moderate internal strabismus usually occurs in children between 2 and 3 years of age and is usually accompanied by moderate to high hyperopia or an abnormal moderate cohesion to moderate ratio. Exotropia is an outward slanting of the eye position and is generally classified as intermittent or constant exotropia. Intermittent emmetropia can be maintained in a normal position most of the time by the ability to fuse the eyes because of the patient’s good ability to fuse, and only occasionally in sunlight or when fatigued and distracted, does the eye position become emmetropic. Some children also exhibit a tendency to close one eye in strong sunlight. Intermittent exotropia often develops into constant exotropia. Upward or downward strabismus is less common than internal or external strabismus, and upward or downward strabismus is often accompanied by a skewed head, or compensatory head position. Complications Most patients with strabismus have reduced or lost stereoscopic vision, amblyopia may occur in patients with monocular suppression, and some patients have diplopia and confusion. Treatment 1. Non-surgical treatment Treatment of strabismus is aimed firstly at amblyopia to promote good visual development in both eyes, and secondly at correcting the skewed eye position. The treatment of strabismus includes: glasses, eye shields, and orthoptic training. Eye shields are the main treatment for amblyopia caused by strabismus. Eye muscle surgery involves relaxing (weakening) or shortening (strengthening) one or more of the extraocular muscles in one or both eyes. Mild strabismus can be corrected by wearing prismatic lenses. Orthoptic training can be used as a supplement before and after surgery. 2. Surgery The younger the age of strabismus treatment, the better the treatment results. Strabismus surgery is not only to correct eye position and improve appearance, but more importantly to establish binocular vision function. The best time for surgery is before 6-7 years old. After surgery, binocular vision training is used to enhance and maintain stable stereo vision.