Strabismus is a phenomenon in which the visual axis of both eyes cannot look at the same target at the same time, and only one eye looks at the target while the other eye’s visual axis deviates to the side of the target. There are many kinds of strabismus, the most common one is the inward strabismus, which is medically called internal strabismus, commonly known as “opposite eye” and “crossed eyes”. The most common type of strabismus is inward strabismus, which is known as “crossed eyes” and “crossed eyes”, and outward strabismus, which is known as exotropia. Of course, strabismus does not only refer to cases where the relative position of the two eyes is obviously deformed, but also includes cases where the obliquity is so small that it is not easily detectable on the surface, but the visual function of both eyes is not normal, and also includes those cases where there is no oblique position at all but both eyes are not normal. Therefore, the concept of strabismus should be understood as an abnormality in both the relative position of the two eyes and the visual function of both eyes.
(I) Causes of strabismus formation in children
1.Improper development
Children, especially infants, have imperfectly developed binocular monovision function and cannot coordinate extraocular muscles well, and any unstable factors can contribute to the occurrence of strabismus. The monocular function of human is gradually developed later in life, and this function is gradually developed and matured by repeatedly accepting the stimulation of external clear images as the visual function. The establishment of precise fusion function lasts until after 5 years of age, and the establishment of stereopsis is the latest, and can approach that of adults only at 6-7 years of age.
During this time, strabismus can occur if the child has high refractive error and refractive aberration, abnormal retinal macular development, macular disease, and visual conduction pathway disorders that prevent the formation of binocular monocularity. Or because the child originally formed binocular monovision function is unstable, external stimuli (such as fever, shock, trauma, etc.) to make this unstable ability to weaken loss and cause strabismus. After the eye strabismus and impede the development of binocular monovision, aggravating the development of strabismus, forming a vicious circle. Therefore, it is said that the period before the age of 5 when binocular monovision is not perfect is the high incidence of strabismus in children.
2.Congenital anomaly
This strabismus is mostly caused by anatomical defects such as abnormal development of the position of the congenital extraocular muscles, abnormal development of the extraocular muscles themselves, incomplete differentiation of the mesoderm, poor separation of the ocular muscles, abnormal and fibrotic muscle sheaths, or paralysis of the nerves innervating the muscles. In some cases, the head and face of the baby are damaged by the use of forceps during delivery, or the mother exerts excessive force during delivery, resulting in punctate hemorrhage in the brain, and the hemorrhage happens to be in the nucleus of the nerve that governs eye movements, causing extraocular muscle paralysis. In addition, there is also a genetic component. Strabismus is not inherited in all members of the family, and the defect is often inherited indirectly to the next generation of children. Generally, strabismus occurs within 6 months of birth and is called congenital strabismus, which does not have the basic conditions for establishing binocular vision and is the most harmful to the development of visual function.
3. The developmental characteristics of the eye make children susceptible to strabismus
Because children have small eyes and short eye axes, they are mostly hyperopic, and because children have large corneal and crystal refractive power and strong ciliary muscle contraction, i.e. strong adjustment power. Such children need more adjustment force to see objects clearly, and at the same time, both eyes also turn inward with force to produce excessive convergence, which easily causes internal strabismus, and this kind of internal strabismus is called regulatory internal strabismus.
4.Insufficient control of the eye movement center
If the collection is too strong or the abduction is not enough or both exist at the same time, it produces “internal strabismus”; on the contrary, if the abduction is too strong, the collection is not enough or both exist at the same time, it produces “exotropia”.
(B) The main symptoms of children’s strabismus
1. Eye position deviation Inward deviation of the eye is internal strabismus, outward deviation of the eye is external strabismus, upward deviation is upward strabismus, and downward deviation is downward strabismus.
2. Weak binocular vision The ability of depth vision and stereoscopic vision requires the use of both eyes in parallel, so children with long-term strabismus will lack depth and stereoscopic sense.
3. Abnormal head position In order to use both eyes, some children with long-term strabismus will tilt their head or face. Parents should take their children to the regular hospital as soon as possible when they find the above strabismus symptoms.
(C) Early detection of strabismus in children
There are many ways to detect strabismus at an early stage. To avoid children missing the treatment time of strabismus, so we introduce several methods that can detect strabismus in children more easily and quickly.
The first method is to use a flashlight at home to give the child an ortho-ocular irradiation. When a normal flashlight shines in front of the child’s two eyes, there is a manifestation in the child’s cornea, and the two points of light are in the middle of the eye, in which case parents can determine that the child does not have strabismus.
In the second case, the child’s black eye is skewed to the outside, which proves that the child is skewed, and there is another kind of light point on the outside of the child’s eye. Another method, a very simple method, when the child’s head is crooked to one side, we call it a strabismus, a very simple way, parents use a piece of gauze to wrap the baby’s one eye, after covering if the child’s head position is correct, or the original 45 degrees outside, now crooked 15 degrees, then certainly the child’s crooked head and eye strabismus is related.
(iv) Examination of strabismus in children
Eye position examination refers to the examination of eye position, which is further divided into orthophoria, cryptorchidism and apparent strabismus. Orthotropia means that the eye position remains orthotropic regardless of the presence of the fusion reflex. Occult strabismus is a condition in which the eye has a potential tendency to deflect, but the eye position is kept normal by the fusion reflex. This means that the eye position is orthotropic when the fusion reflex is present and oblique when the fusion reflex is broken. A strabismus is a condition in which the eye position appears significantly deviated regardless of the presence or absence of the fusion reflex.
We should pay attention to the eye position at distance (usually set at 6 meters) and at near (40 cm or 33 cm) when performing the eye position examination, and we should analyze the occult strabismus qualitatively and quantitatively. The commonly used detection methods are, are corneal reflection method and masking method.
Corneal light reflection method: the use of corneal reflection point to determine the degree of strabismus, light point in the nasal side of the cornea is exotropia, light point in the temporal side of the cornea is internal strabismus.
The masking method is the easiest and simplest method in strabismus examination, which not only can determine the absence of strabismus, but also can determine which kind of strabismus is. It is simple and easy to prepare, and includes a flashlight with a spotlight bulb and a masking piece that blocks light. Alternate masking method: The patient is made to sit upright and look at the light source of the flashlight in front of the examiner, at which time there is a light spot in the pupil area of each of the examined eyes. According to the position of the light spot and the direction of eye movement after masking, determine whether there is strabismus and the nature of strabismus.
If the light point is located in the center of the pupil of both eyes, the right eye is covered with a masking piece first, and the left eye does not move, and then the left eye is covered, and the right eye does not support the orthophoric eye, there is no apparent strabismus and no occult strabismus. The right eye is covered, the left eye moves inward from the outside, and then the left eye is covered, the right eye also moves inward from the outside to the front, and the light point is no longer moving when it is located in the center of the pupil, which is an external oblique or external oblique. In the same way, if the eye moves from the inside to the center, it means there is an internal occultation or internal obliquity. If there is upward and downward movement, it indicates vertical obliquity. Covering and uncovering method: When the covering piece is executed on the same eye, the pattern of movement of the two eyes is observed to identify occlusion and dominant strabismus.
(E) Correction and treatment of strabismus in children
The treatment methods for children with strabismus vary depending on the type of strabismus, and can be generally divided into surgical and non-surgical therapies.
1. Surgical treatment is to surgically adjust the strength of the external eye muscle and the position of the attachment point to normalize the eye position. Most congenital internal strabismus and upward and downward strabismus require surgical treatment, and non-adjusted strabismus with large obliquity usually requires surgical correction.
2.Non-surgical treatment: Not all strabismus needs surgical treatment. If the strabismus is moderate, it can be corrected by wearing appropriate farsighted glasses or bifocals. If there is also a middle or high refractive abnormality, glasses are often needed to correct it. In addition, axis correction training can be used to help restore the monovision of both eyes and increase the image blending ability. For example, training with an axis correction machine or wearing prism lenses ……. If amblyopia is also present, amblyopia training is also an essential treatment.