In the conceptual analysis, neither “secondary internal strabismus” nor “continuous internal strabismus” is the only expression for internal strabismus secondary to exotropia. Since the type of natural regression is very rare, it is customary to refer to the internal strabismus after exotropia as continuous internal strabismus; secondary internal strabismus includes both the internal strabismus that occurs after exotropia correction and the perceptual internal strabismus that occurs due to perceptual fusion disorder caused by low visual acuity. Therefore, whether the internal strabismus occurring after exotropia should be called secondary or continuous internal strabismus has not been unified in the literature. The authors believe that it is actually a secondary internal strabismus secondary to surgery. It is also called “continuous internal strabismus”. What is the incidence of continuous internal strabismus: The incidence of secondary internal strabismus after external strabismus surgery is about 6%-20%. The occurrence of continuous internal strabismus is not only related to surgery, but also related to the patient’s own adjustment and the type of strabismus as well as the brain’s regulation of eye position. 1. Surgical overcorrection Early overcorrection of more than 20 PD in exotropia surgery is prone to secondary internal strabismus, and overcorrection of more than 17 PD in the early postoperative period is a risk factor for the occurrence of secondary internal strabismus; mild overcorrection is more appropriate for older children and adults, and overcorrection is not appropriate for children. It plays a very good role in preventing the occurrence of continuous internal strabismus. (1) The problem of refractive adjustment: children have a strong ability to adjust, especially after surgery if the refraction is not sufficiently corrected, too strong adjustment aggravates the collection, and the inability to control the separation fusion will aggravate the secondary internal strabismus. Atropine ciliary muscle paralysis is given to determine and alleviate the factors of accommodation during pupillometry. (2), the central adjustment of the problem: secondary strabismus is generally constant internal strabismus, some children have central adjustment problems, for example, we found in the clinic some periodic secondary internal strabismus, after treatment of the eye position is very positive, but with time, the patient gradually formed exotropia, so secondary internal strabismus may also have a central adjustment of the factors, pending from the neurological Therefore, whether there may be a central regulation factor in the occurrence of secondary internal strabismus remains to be discovered at the neural level. 4. High AC/A Studies have suggested that hyper-regulation and high AC/A are the causes of internal strabismus. If these patients are combined with hyperopia, some patients with strong adjustment will not be able to correct their strong adjustment and AC/A after surgery or overcorrection, which will aggravate the occurrence of internal strabismus. 5. Combination of other strabismus Difficulty in reconstruction of binocular vision is the reason for the occurrence of re-strabismus. The incidence of secondary internal strabismus combined with other strabismus such as vertical strabismus accounts for (58.9%) that secondary internal strabismus is more likely to occur after surgery for non-simple external strabismus. This may be related to the complexity of the surgical design and the influence of each other. 6. other: some think that the risk factors for the occurrence of secondary internal strabismus also include high myopia, amblyopia, in addition to the type of intermittent exotropia, the difference in the strabismus degree between distance and near vision, and the surgical method. The diagnosis of continuous internal strabismus Because the part of internal strabismus that appears after exotropia may disappear or reduce with time, some people think that the overcorrection is found early within 1~2 weeks after exotropia surgery, and the small degree (10~15△) is mostly temporary and will gradually decrease or disappear with time, so no treatment can be performed within 2 weeks, therefore, the secondary internal strabismus after exotropia is considered to appear 2 weeks after surgery as far-sightedness or near-sightedness +10PD. Therefore, the secondary internal strabismus after exotropia is considered to be a secondary internal strabismus when it appears 2 weeks after surgery with distance or near vision +10 PD. The following symptoms are also combined: diplopia: ipsilateral diplopia may occur in secondary internal strabismus, especially in patients with limited abduction who have increased diplopia distance when gazing to the sides. Amblyopia: Children with secondary internal strabismus are prone to monocular gaze amblyopia. Oculomotor disorders: mainly include monocular or binocular oculomotor disorders, especially extensor restriction; compensatory cephalic position: mostly meet to turn to the extensor restriction of paralysis; bilateral fusion function is weakened or disappeared: secondary internal strabismus abduction fusion can not be overcome will occur bilateral fusion dysfunction. Do I have to have surgery for continuous internal strabismus? Conservative treatment of continuous internal strabismus is very important. Therefore, once secondary internal strabismus occurs, the causes of the formation of secondary internal strabismus should be identified and active conservative treatment should be taken. The early detection of overcorrection within 1~2 weeks of exotropia surgery and the small degree (10~15△) is mostly temporary and will gradually decrease or disappear with time, so no treatment can be performed within 2 weeks. If an internal strabismus greater than 17 △ appears early after exotropia surgery, the chance of secondary internal strabismus will be greatly increased in the long term. In case of persistent diplopia after surgery or if the strabismus deviation does not improve after 2 weeks of observation, intervention should be performed to establish fusion and reduce the deviation. Methods include: (1) Selective masking: To prevent the occurrence of amblyopia, some scholars have adopted selective masking methods for training. It also reduces the degree of accommodation in both eyes and reduces the chance of internal strabismus. (2) Trigonometry: For small degrees of internal strabismus without refractive adjustment factors, trigonometry can be considered for transitional treatment. The application of trigonometry with the fundus of both eyes outward is beneficial to 1. the reconstruction of binocular visual function 2. the elimination of diplopia and confusion 3. the stimulation of fusion apart and the alleviation of secondary internal strabismus. Currently, we commonly use membrane-pressed trigeminal lenses for patients with good compliance in wearing. The rate of strabismus decrease was 2.9 PD per 6 months on average, with a 32% rate of mirror removal within 1 year, and 92% of patients had improved stereopsis compared to preoperative. However, patients who had their lenses removed within 1 year had more rapid changes in internal strabismus and were more likely to have exotropia drift. (3) Topical pupil reduction agents: For patients with high AC/A, we can also apply topical pupil reduction agents such as econolactone and diethylphosphonothiocholines, which can stimulate the central reduction of accommodative pooling. (4) Refractive correction. In patients with combined hyperopic accommodation, the early removal of accommodation is usually achieved by refractive correction of hyperopia. Our experience is that postoperative internal strabismus should be followed immediately by atropine dilated pupil examination, examination of refractive regulation, and wearing of appropriate hyperopic glasses to reduce regulatory factors and promote fusion function. After 4 weeks of treatment with alternating masking, trigeminal therapy, and drops of pupil reduction agents (echolesters, diethylphosphonothiocholinester), 72% of patients with distant and near strabismus were less than 10△, and only 6% of patients were greater than 20△, requiring secondary surgery. Therefore, the conservative treatment of secondary internal strabismus is very important in the near future after external strabismus surgery. V. When to operate for continuous internal strabismus If the secondary internal strabismus persists for more than 6 months after exotropia surgery and the degree of internal strabismus is more than 15△, the conservative treatment is ineffective and surgery is considered. Beijing Children’s Hospital has special treatment for continuous strabismus. 1. Application of adjustable sutures The operation of secondary strabismus has greater unpredictability. Meanwhile, continuous internal strabismus was operated again, and the surgical cure rate reached 82.3% after applying adjustable suture adjustment 2. Local injection of botulinum toxin Local injection of the internal rectus muscle in secondary internal strabismus, some patients eventually return to normal eye position, and some need further internal strabismus surgical treatment, but 2/3 of patients need multiple injections, and the effect is poor for those patients without potential fusion function. VII. Evaluation of postoperative results for the treatment of secondary internal strabismus The success rate of surgery for secondary internal strabismus was reported to be 76.9%. Studies have shown that after repositioning of the external rectus muscle, there is a tendency for the eye position to shift in the direction of external strabismus, which some people refer to as the rein effect of the external rectus muscle, that is, after strengthening surgery, there may be a tendency for a certain degree of eye position regression.