Intermittent exotropia is a type of strabismus between exotropia and common exotropia. It is a strabismus in which the visual axes are often separated, initially occurring when looking at a distance, and when looking at a distance, the fused scattering amplitude exceeds the fused total collection amplitude, which produces exotropia, and intermittent exotropia is preceded by exotropia.
Causes of intermittent strabismus
Its onset is mainly due to the imbalance of abduction and assembly functions. When the pooling ability is insufficient and the fusion ability is low, it cannot counteract the excessive abduction ability and makes the eye position tend to be outwardly oblique.
Symptoms of intermittent strabismus
Intermittent exotropia often occurs in early childhood, initially only when looking at a distance, but as the disease progresses, the number and duration of intermittent exotropia increases, and finally exotropia can occur when looking at the near. The apparently oblique phase of intermittent exotropia often occurs during fatigue, illness, drowsiness, or inattention. Intermittent emmetropia may occur in visually immature children with temporary diplopia that is soon suppressed and has abnormal retinal correspondence.
The common symptom is photophobia, and in outdoor daylight, one eye is often closed, the cause of which is unknown. It is estimated that patients look at distant targets outdoors, without near objects to stimulate the collection of both eyes, and bright daylight flashes the retina, interfering with the fusion, and the patient changes from exotropia to obvious, but it is not necessarily certain that such patients close one eye to avoid diplopia. It is possible that the bright light affects the fused pooling of the patient with intermittent exotropia, causing one eye to close.
Intermittent exotropia can be combined with the A-V sign, or with other vertical strabismus, such as separated superior strabismus.
What tests should be done for intermittent exotropia?
All strabismus items should be examined, with special attention to the measurement of the diagnostic strabismus angle, such as the angle of deflection when looking at a distance, and it is better to make the patient look at the target >6m away in order to fully examine the degree of exotropia and determine the type of exotropia, because the timing of treatment and treatment methods are different. Refractive error should be corrected at the time of measurement to control its adjustment. If intermittent exotropia is only present when looking at distance, and the distance oblique angle is greater than the near oblique angle at least 15△, a masking test should be done, one eye should be masked for 30-45 minutes, when the mask is removed, the two eyes must remain separated, that is, when one eye is unmasked, the other eye must be blocked by a universal eye shield, and when opened, the near obliquity should be measured quickly with the trigeminal uniformity masking test, and then the far obliquity should be viewed to prevent the patient from having Burian and Franceschetti observed a group of 237 patients with exotropia, and only 10 cases were of the separate process type. Thus, it appears that most patients with exotropia look at the distant oblique angle more than the near oblique angle and should be classified as similar to the separated over-strong type.
The degree of upward and downward deviation was measured to determine the presence or absence of the A-V sign.
Measure the oblique angle when gazing to the left and to the right, whether there is any lateral incomitance (lateralincomitance) problem. By definition, lateral incomitance refers to patients with exotropia, when looking to both sides, the obliquity is 20% smaller than the first eye position obliquity, and clinical practice proves that patients with lateral incomitance are easily overcorrected surgically and cause the internal V sign.
Check the stereopsis sharp: the patient must also measure his stereopsis during the occlusion period, if the stereopsis is not normal, it means that the stereopsis caused by the intermittent apparent strabismus declines, and the stereopsis continues to decline within a few months is a strong indication for surgery to correct intermittent exotropia.
How should intermittent exotropia be treated?
1, ciliary muscle paralysis refractive examination has obvious refractive error, especially astigmatism and refractive aberration patients, in order to ensure a clear retinal image, should be fully corrected; surgery with myopia dry, should be fully corrected; exotropia with hyperopia, correction of hyperopia will reduce the regulatory collection, so that the exotropia increases, the need for full correction or partial correction, depends entirely on the degree of hyperopia, the patient’s age and AC/A ratio, usually less than +2 For infants and children with +2.00D, no correction is necessary. For older patients, correction of hyperopia is usually necessary to avoid refractive fatigue. The elderly have exotropia with presbyopia, weakened regulation, such as hyperopia, need to be corrected, you can give the minimum number of degrees to facilitate seeing near.
2, negative spherical mirror with negative mirror to correct intermittent exotropia, can be done as a temporary measure, or placed in the upper half of the bifocal mirror, to treat the separation of too strong; or placed in the lower half of the bifocal mirror, to treat the collection of insufficient, stimulate its regulatory collection, control exotropia, this treatment method, should not be advocated, the child with this method of treatment, often cause visual fatigue.
3, trigeminal and masking therapy bottom inward trigeminal can strengthen the central concave stimulation of both eyes, about 1/2 to 1/3 of the skew can be corrected by trigeminal stimulation fusion, recently, some people proposed in the early stage of intermittent exotropia, masking as a good non-surgical treatment, with this method of treatment, about 40% of patients whose apparent obliquity (see far) can be changed into a hidden oblique. In the early stage of intermittent exotropia, because most of the time it is exotropia, the number of apparent oblique is not much, and the degree of skew is not big, it is not advocated for surgical treatment.
The most suitable age for surgery for exotropia is still under debate. Some people advocate that the earlier the surgery, the better, otherwise it will become a constant exotropia. Since most intermittent exotropia has good fusion and binocular vision, the results of surgery after the age of 2 to 3 years or 10 years are almost the same and can be observed for several years. For infants and children with immature vision, in order to avoid overcorrection of surgery, it is recommended to delay surgery, strengthen fusion with negative spherical lenses, and prevent suppression by alternate masking, and consider surgery if the fusion function deteriorates rapidly or if the oblique angle is stable.
The indications for surgery are determined by the fusion control, the size of the oblique angle and the age of the patient. If there is no intermittent exotropia, surgery should be performed as soon as possible; Huynh considers that the strabismus measured by masking is greater than 20△; Jampolsky says that it is more than 15△; Hiles advocates that the deviation is greater than 20△, and there is a clear component of apparent obliquity and visual loss of compensation. From the viewpoint of the effect of surgery on retinal correspondence, intermittent exotropia can occur in order to eliminate the interference of diplopia and confusion, abnormal retinal correspondence and inhibition, and the best time to operate is to eliminate exotropia before it develops into inhibition and abnormal retinal correspondence.
The younger the age, the higher the chance of restoring normal binocular vision after surgery, while most adults cannot restore normal binocular vision after surgery even if the eye position is corrected. It is not easy to master the best timing of surgery clinically. If the age is too young, the examination is not cooperative and the amount of surgery is not easy to control, which increases the rate of reoperation. It is believed that children with intermittent exotropia who are around 4 or 5 years old and have normal intelligence can cooperate with general eye position examination after repeated training, and this is the right time for surgery. Conclusion: The earlier and more frequent the surgery, the higher the reoperation rate and the greater the risk of amblyopia and fusion loss.
We believe that for children with progressive intermittent exotropia, those with deviations greater than 20△ and those with more than 50% of the apparent oblique period, the surgical plan can be designed according to the size of their deviations and the masking test, and if the deviations are greater than those of the near after 30-45 minutes of masking, the posterior migration of the external rectus muscle can be done bilaterally, and the amount of surgery can be determined according to each physician’s test and method. If the oblique angle of looking near is greater than that of looking far by at least 15△ and less than 55△, the posterior migration of external rectus muscle can be done bilaterally or the posterior migration of non-dominant eye and tendon amputation surgery. If the exotropia is greater than 55△, three muscles can be done, posterior migration of the external rectus muscle in the main eye and posterior migration-truncated tendon surgery in the non-dominant eye. If the external obliquity is greater than 70△, a bilateral posterior migration-tendon amputation is done.
If the strabismus is at least 20% smaller than the first eye position when the patient gazes to the left and right, there is a significant risk of overcorrection, especially for patients with immature vision.
For children with immature vision, undercorrection should be advocated, because a mild overcorrection to an internal oblique state is more likely to result in monocular gaze syndrome than a mild undercorrection to an external oblique state, and may result in the formation of an inhibitory dark spot, leading to developmental amblyopia. On the contrary, if the patient’s visual acuity has developed, a mild overcorrection of 10 to 20 △ is ideal, and it will eventually produce stable results. Overcorrection at 25Δ should be avoided even in visually mature patients, as such overcorrection can lead to blind spot syndrome and prevent postoperative fusion.
If the patient has an A or V sign, caused by an overactive superior or inferior oblique muscle, an intramuscular reduction of the overactive muscle can be done at the same time as the horizontal strabismus surgery, and if both the superior and inferior obliques are overactive, reduction of either oblique muscle is contraindicated.
The prevalence of overcorrection in exotropia has been reported to be between 6% and 20%. If a large degree of overcorrection occurs immediately after external oblique surgery, the patient should be reoperated within 24 hours because there is a risk of muscle loss or slippage, and the external rectus muscle is less likely to be lost than the internal rectus muscle. Significant overcorrection can also occur if the mechanical factor internal rectus muscle has an excessive amount of tendon amputation, but the amount of overcorrection is not as large as the former.
The internal oblique is common and can wait for observation, and can disappear completely when the internal oblique is 10 to 15△ after surgery. The small amount of overcorrection after exotropia also depends on the age of the patient. Children with immature vision who have a small amount of overcorrection should be carefully monitored for the development of inhibited dark spot and developmental amblyopia. If the patient does not have a tendency to gaze, alternate masking is feasible, and if there is a moderate tendency to gaze, masking therapy is feasible. In addition, further optometry should be performed. If there is hyperopia, full correction should be applied, and if there is a large near skew, treatment with pupil reduction agents or bifocal lenses should be applied. After the above treatment for 4 months, vision has not done much small amount, to treat a new patient, can not simply restore the previous exotropia surgery.
It is ideal to overcorrect 20△ for vision maturity sufferers and still have 20△ internal obliquity 6 weeks after surgery, 2 surgeries are feasible and the surgery should be performed 6 months after the first surgery. It is important to do a traction test before surgery, and if traction is found, the muscles, conjunctiva and fascial sac should be properly posteriorly migrated.
The management of undercorrection of surgical residual large degree exotropia greater than 15-20△ can be performed within 6-8 weeks after the first surgery with 2 surgeries, and this case should be considered as a new case. If the residual oblique angle is equal to the near oblique angle, the first surgery is posterior migration – tendon amputation, then the other eye can do the same surgery; the first surgery is bilateral posterior migration of external rectus muscle, can do one side of the external rectus muscle marginal myotomy combined with the same side of the internal rectus muscle amputation tendon. If the residual external oblique angle is greater than the proximal oblique angle, the first operation should be posterior migration of the external rectus muscle or marginal myotomy of the external rectus muscle; if the first operation is posterior migration – tendon osteotomy, posterior migration of the external rectus muscle can be done on the other eye. When the second surgery of the external rectus muscle is done, it is better to posteriorly migrate the temporal bulbar conjunctiva at the same time in order to prevent the scar from moving forward and counteracting the surgical effect.
For patients with mild undercorrection, the residual obliquity is less than 15 to 18△, and they can be trained with de-suppression and fusion set to achieve a stealth oblique state. If the patient is myopic, all should be corrected. If the patient is orthoptic or hyperopic, ciliary muscle paralyzing agent can be used to stimulate the regulatory collection to make both eyes orthotropic. After obtaining fusion using the above method, the number of drops can be reduced to once every 3 days and continued for 2 months, while using base-to-inward trigeminal lenses with the same degree as the undercorrection is effective for patients with mature vision.
Protection methods
I. Eye rolling method
Choose a quiet place, either sitting or standing, relax your whole body, clear distractions, open your eyes, keep your head and neck still, and turn your eyes alone. First, the eyes will gaze directly below, slowly turn to the left, then turn to gaze directly above, to the right, and finally back to gaze directly below, so that the first clockwise turn 9 circles. Then let your eyes turn from gazing down, to the right, to the top, to the left, and then back to the bottom, so that you can turn counterclockwise 6 times again. Do this 4 times in total. Each time you turn, your eyes should reach the limit as much as possible. This eye turning method can exercise the eye muscles, improve nutrition, so that the eyes are flexible and shining.
Second, eye breathing concentration method
Choose a fresh air, or sit or stand, relax your whole body, eyes flat in front of you, slowly breathe in enough, eyes then open wide, pause for a moment, and then slowly breathe out, eyes also slowly closed, do 9 times in a row.
Three, ironing eye method
This method is best done sitting, the whole body relaxed, close the eyes, and then quickly rub two palms with each other, so that the heat, while hot with both hands over the eyes, after the heat dispersion of the two hands fiercely removed, both eyes also at the same time with a strong open, so 3 to 5 times, can promote eye blood circulation, enhance metabolism.
Four, wash the eyes method
First disinfect the basin, pour warm water, adjust the water temperature, put your face into the water, open your eyes in the water, make your eyes move up and down and left and right 9 times, and then rotate clockwise and counterclockwise 9 times. At first, the water enters the eyes, the eyes are unbearable, but with the rotation of the eyeballs, the eyes will slowly feel very comfortable. In doing this action, if you feel breathing difficulties, you may want to lift your face from the basin and take a deep breath outside. This method, which can wash away harmful substances and dust from the eyes, is also effective for mild cataracts and can improve the degree of refractive error of astigmatism, farsightedness and myopia. Appropriate eye patch method Gently close your eyes, put the eye patch on the lower edge of the eyebrows, both sides of the nose, gently smooth the eye patch, so that the eye patch and eye skin full contact with closed eyes rest for 15-20 minutes.