Congenital esotropia usually occurs during the postnatal period or within the first few days of life. Because parents rarely see their children during the neonatal period, congenital esotropia is rarely seen clinically. Because the parents of the infant are often unable to make an accurate and objective judgment of the infant’s binocular position within one year of age, they may mistake the instability of equal binocular axes for congenital internal strabismus. In addition, during infancy, because the nasal area is not yet well developed, there is mostly inner canthus and pseudo-strabismus, which also easily cause confusion. Some acquired regulatory strabismus can also occur at this time, and all of the above, can cause confusion in diagnosis. Clinical manifestations of congenital strabismus are characterized clinically by a large angle of deviation and a stable oblique angle of vision with abnormal eye movements. Congenital internal strabismus can occur in children with normal body, but also in infants and children with cerebral palsy and hydrocephalus, and in children with brain injury, whose oblique angle is mostly variable with age, the oblique angle can disappear, and occasionally, at 6 months to 1 year, the internal strabismus can become exotropia. Diagnosis and differentiation: 1. Most patients with congenital internal strabismus: alternate fixation in the first eye position, equal vision in both eyes, crossed gaze when looking to both sides (Figure 1), that is, when looking to the right, the left eye gaze, and when looking to the left, the right eye gaze. A few patients do not have alternate gaze, amblyopia can occur in strabismic eyes (amblyopia), and the incidence of amblyopia is about 40%, and the degree of amblyopia is very deep, accompanied by paracentral gaze. 2, strabismus angle is large; generally greater than 30△, about 50% of patients more than 50△, near and far strabismus angle equal, and stable, not affected by the adjustment, occasionally see strabismus angle in a few months there is a significant change. It should be noted that the child is often unable to abduct both eyes, but this is not a result of bilateral abduction nerve palsy, but secondary to crossed gaze. In other cases, children with congenital internal strabismus have a greater degree of deviation and amblyopia, but no crossed gaze, which can easily be mistaken for a side abduction nerve palsy in eyes with paracentral gaze. In fact, congenital unilateral or bilateral abductor nerve palsy is rare. Congenital internal obliquity should also be distinguished from retrobulbar syndrome, Mobius syndrome, and abducens nerve palsy by the following methods: ① Fix the child’s head in an upright position and make the child’s head turn slightly horizontally and rapidly and slowly to give stimulation to the vagus, especially the horizontal semicircular canal, which can instantly appear a subtle abduction movement, which can be detected by close observation of the hair; ② Place a child with crossed gaze with congenital children with internal strabismus, including one eye for several days, then the other eye can produce abduction movement; ③ traction test, under general anesthesia, children with congenital internal strabismus with crossed gaze have normal traction test and passive resistance to abduction. If the anesthesia deepens, the internal strabismus can disappear, and can present an exotropia. 3, often combined with vertical strabismus: children with congenital internal strabismus can develop dissociated vertival deviation (DVD) by the age of 2 to 3 years, which is manifested as upward and external rotation of the non-gaze eye and downward and internal rotation of the gaze eye; 78% of patients have hypermetropia; nystagmus can also be seen, which is rotational or horizontal, and the nystagmus is sometimes hidden, appearing only after The nystagmus is sometimes occult, appearing only after covering a glance, or the nystagmus is reduced during internal retraction and increased during abduction. 4. Refractive examination of ciliary muscle palsy demonstrates mild to moderate hyperopia in 90% of cases, with similar refraction in both eyes. 5.AC/A is normal. 6, measurement of oblique angle, because infants and young children are not easy to do trigeminal masking test, commonly used Hirschberg and Krimsky method of measurement, so that the child look at the light, with the base outward trigeminal to see how much can be reflected in the corneal reflective point in the central cornea that is the oblique angle. Treatment: 1, hyperopia greater than +2, 00D should be corrected. 2, with amblyopia, available masking treatment. Alternate masking is effective for a few amblyopic patients, but it is not effective for preventing suppression and abnormal retinal correspondence, because in infancy, only binocular orthophoria, or at least 10△ to internal strabismus can produce binocular monocularity. Therefore, it is not right to use alternate masking for several years in the early stage of children with congenital internal strabismus, and later train fusion before surgery. 3, less than 1, 50D can be used strong pupil constrictor, once a day for 2-3 weeks, when the child ≥ 6 months, and can alternate gaze, you can consider surgery. 4, surgery, congenital internal strabismus treatment is mainly surgery to correct the eye position, the debate is when and how to perform surgery. parks, Taylor, Costenbader advocate that surgery should be performed within 6 to 12 months, Parks believes that in the period of 6 to 12 months to perform surgery than in the period of 12 to 18 months after surgery to restore the chance of fusion function to me. von Noorden, Jampolsky et al. demonstrated, based on research material, that surgical correction of congenital internal strabismus after 1 year of age can result in fusion of both eyes. They concluded that the percentage of obtaining central fusion of both eyes by correcting the eye position before the age of 2 years was no higher than that of those who underwent surgery between 12 and 18 months after birth. In addition, their study further demonstrated that postoperative ophthalmoscopic correction, i.e., trigeminal or negative spherical lenses to correct postoperative residual obliquity, significantly increased the rate of binocular central fusion; approximately 53% of children with postoperative ophthalmoscopic correction achieved binocular central fusion, compared with 6% of those with surgery alone. In addition, children younger than 1 year of age have difficulties in examination, diagnosis, and accurate measurement, and are more likely to be overcorrected or undercorrected if they are not adequately prepared for surgery. Parks believes that congenital internal strabismus, even if the visual axes are parallel, does not result in good stereopsis, but only in peripheral fusion without central fusion, the so-called monofixation syndrome, which is also important because it prevents recurrence of internal strabismus or This is also important because it can prevent the recurrence of internal strabismus or its transformation into exotropia. The surgical procedure consists of a posterior migration of the medial rectus in both eyes (recession) or a posterior migration of the medial rectus combined with a tendon truncation of the external rectus (resection). If the oblique angle is 50~75△, three horizontal muscles can be done; if the oblique angle is 70~90△, four horizontal rectus muscles can be done in both eyes; if the lower oblique muscle is too strong, the lower oblique muscle is often posteriorly migrated. For children within 4 years old, correction of congenital internal strabismus is within 10△, and for older children, 15△ can be undercorrected, with the aim of restoring binocular vision opportunities for young children. In older children, the correction is cosmetic, and if the patient has no binocular vision, exotropia will occur several years after surgery, and if the residual 15△ internal strabismus, the occurrence of exotropia can be postponed. The occurrence of exotropia 10-30 years after surgery is not a reason to deny surgery, because exotropia can also be operated again, congenital internal strabismus to obtain binocular monovision, must be operated early in order to maintain binocular orthophoria, congenital internal strabismus after treatment, but also the occurrence of regulatory internal strabismus and amblyopia, so the child must be closely followed up within 5 years after surgery, and give appropriate treatment.