Internal strabismus, also known as “crossed eyes” or “crossed eyes” by most parents, is a common and frequent disease in children, but the causes of internal strabismus are different, the diagnosis is different, and there are many differences in treatment. The following is a brief introduction to the more common types of internal strabismus and treatment methods (we have not included the rare types), but internal strabismus has serious damage to children’s visual acuity and binocular vision function, and non-professionals are unable to make accurate judgments, so if you find or suspect that your child has internal strabismus, please take your child to a professional medical institution for examination as soon as possible to avoid delays. Treatment I. Congenital common internal strabismus Internal strabismus occurs within the first 6 months of life. The cause is not clear. The child exhibits large-angle internal strabismus with early crossed gaze (both eyes may alternate), which changes to monocular gaze when refractive error or amblyopia is present (the rate of monocular amblyopia is extremely high). The degree of refractive error rarely exceeds +2.0 D. It has a significant impact on binocular vision and can be combined with vertical strabismus. [Treatment]: All children need dilated eye examinations (preferably with atropine to completely paralyze the ciliary muscle), and small degrees of hyperopia can be treated without glasses. However, if there is amblyopia in one eye, the amblyopia must be treated first and then surgically treated after being able to alternate gaze. It is best to perform the surgery before the age of 2. If the surgery is performed after the age of 2, the fusion of the two eyes will be almost impossible to form. Refractive accommodative internal strabismus is the more common type of internal strabismus. It is caused by uncorrected hyperopic refractive error with separate fusion insufficiency. It usually develops at the age of 2-3 years, and the hyperopia is between +3D and +6D. However, there are a few children who are not in this range in terms of age and degree of hyperopia. Early on, parents may notice an internal strabismus when the child looks at near objects, but it can return to an orthotropic position, but if left uncorrected for a long time it can turn into a normal strabismus. [Treatment]: Refractive error must be completely corrected after atropine dilated pupil examination (wearing glasses), regular review after wearing glasses, and amblyopia treatment for children with amblyopia. For children with amblyopia, amblyopia should be treated. For children with partially adjusted internal strabismus, microstrabismus, and vertical strabismus, surgery is possible. The non-refractive regulatory internal strabismus is caused by the abnormal joint movement between regulation and assembly. The age of onset is usually between 8 months and 7 years. Orthopia, hyperopia and myopia can occur, but mild hyperopia is common. AC/A is usually greater than 6:1. [Treatment]: Correction of refractive error, wearing bifocal glasses, and treatment of amblyopia if there is amblyopia. For children who cannot wear bifocal glasses, pupil reduction agents can be used; for children with small strabismus and who can cooperate, orthoptic training can be performed to expand the range of external fusion. When the effect of the above treatment is not obvious, surgery can be chosen. Partial Adjustment Internal Strabismus is more common in children with internal strabismus, and is currently thought to be caused by a combination of factors associated with infantile-type internal strabismus and post-growth refractive adjustment internal strabismus. It usually develops at the age of 1-3 years, and moderate hyperopic refractive error is common, often accompanied by astigmatism and refractive aberrations, and the internal strabismus remains after wearing corrective glasses. [Treatment]: Complete correction of refractive error, amblyopia treatment for amblyopes, regular review in order to adjust the refractive power of glasses. In the case of basically balanced vision in both eyes, surgery is performed to treat the remaining internal strabismus (correction of vertical strabismus for combined vertical strabismus). Non-adjusted internal strabismus is also common in children, and is caused by hypertrophy of the internal rectus muscle and other anatomical changes due to the imbalance between the tension set and the separation reflex. The age of onset can be between 6 months and 6 or 7 years of age, and there is a genetic predisposition. The disease is usually preceded by a causative factor, such as trauma or high fever, with no apparent refractive error, and is not associated with regulatory factors. It can also be associated with other types of strabismus. [Treatment]: First of all, dilated pupils must be examined to exclude refractive error factors. If alternating gaze is possible, surgical treatment should be performed as soon as possible. If alternate gaze is not possible, the amblyopic eye should be treated urgently, and surgery should be performed as soon as the vision of both eyes is basically balanced. Secondary common internal strabismus (1) Perceptual internal strabismus: due to low vision in one eye early after birth, resulting in sensory fusion destruction, internal strabismus occurs under the effect of convergence function. Generally, it develops at the age of 0-5 years, the visual acuity of one eye is lower than 0.1, the gaze function is lost, the degree of internal strabismus is more serious, the amblyopia of the eye with low visual acuity is more serious, and other types of strabismus can be combined. [Treatment]: Surgery can be appropriately delayed to reduce the incidence of postoperative exotropia. (2) Continuous internal strabismus: usually caused by overcorrection after exotropia. [Treatment]: If the angle of the internal strabismus is small, it can be observed, corrected by wearing corrective glasses, or by adding pressure to paste trigeminal lenses; if the degree of internal strabismus is large, it needs to be operated again. (3) Residual internal strabismus: caused by undercorrection after internal strabismus surgery. [Treatment]: Basically the same as continuous internal strabismus. VII. Other types of internal strabismus (1) Periodic internal strabismus: The cause of the disease is still unclear, but it is generally believed to be related to the biological clock mechanism. The appearance of internal strabismus is cyclic, generally a cycle of 48 hours (1 day of internal strabismus, 1 day of orthotropia), but also a cycle of 72 hours or 96 hours. It usually appears within 10 years of age and changes to permanent internal strabismus after 1 year of onset. [Treatment]: Surgery is the main treatment. (2) Acute common internal strabismus: sudden onset of internal strabismus, no impairment of eye movement, and no obvious organic lesion on neurological examination, but a few patients may have some intracranial lesions leading to this disease. [Treatment]: Small degrees of internal strabismus can be corrected by pressing the trigeminal lens; for large degrees of internal strabismus, children younger than 5 years old should be operated in time to avoid inhibition and amblyopia, while older children can be observed and then operated after the symptoms are stabilized. (3) Microdegree internal strabismus: the degree of strabismus is less than 10 trigeminal, the etiology is still unclear, and it is usually abnormal retinal correspondence with abnormal sensory fusion and near stereo vision. [Treatment]: In principle, no surgery. timely treatment should be given before the age of 5 to correct refractive error, cover the healthy eye and train the amblyopic eye. A portion of children treated before the age of 5 can achieve better treatment results. (4) Nystagmus block syndrome: It usually occurs in infancy, and nystagmus is reduced or disappears when the eye is turned inward or assembled, and intensifies when the eye is turned outward. [Treatment]: Surgery is generally used, but the surgery can be postponed appropriately, and the surgical effect is unpredictable, the chance of re-operation is high, and the surgery is only to obtain cosmetic effect. Congenital adductor nerve palsy is rare, with an inward strabismus and limited external rotation of the affected eye. The child’s face is often turned to the lateral gaze. Amblyopia may be combined, but there is usually no diplopia. The clinical observation is that the onset is more in both eyes than in one eye. [Treatment]: Surgical treatment, children with amblyopia should be treated for amblyopia first. Some children with Duane’s retrobulbar syndrome show internal strabismus, mostly congenital. It is generally believed to be caused by abnormal myofascial development or abnormal innervation. The eye is limited in external rotation, with the eyeball receding and the lid fissure narrowing in internal rotation; in external rotation, the lid fissure opens up and the eye can turn sharply up or down. Some children have a compensatory head position with the face turned to the affected side. [Treatment]: Correction of refractive error and treatment of amblyopia first if amblyopia is present. Some patients may opt for surgical treatment. In principle, surgery is not necessary if the eye position is orthotropic when gazing to the front, but surgery is considered if the strabismus is obvious and the compensatory head position is obvious. The above are some of the more common clinical cases of “true internal strabismus”, but there are also some cases of “false internal strabismus” in which parents suspect that the child has “opposite eyes”. It can be seen that although the symptoms are similar in appearance, the specific causes and treatment are different, so we recommend that parents go to a professional medical institution for early examination once they find that their child has “crossed eyes” or “crossed eyes”. We recommend that parents go to a professional medical institution for early detection of “cross-eye” and “cross-eye”, and not to have the mentality that “children are like this when they are small and will be fine when they grow up”.