Paralytic strabismus
Last reviewed: 23.04.2024
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[Symptoms of paralytic strabismus
It is characterized primarily by the limitation or lack of mobility of the mowing eye toward the action of the paralyzed muscle. When you look at this side, there is double vision, or diplopia. If, with a friendly strabismus, the functional scotoma relieves doubling, then in case of paralytic strabism, another adaptation mechanism arises: the patient turns his head towards the action of the affected muscle, which compensates for its functional insufficiency. Thus, the third characteristic symptom for paralytic strabismus is the forced turn of the head. So, with paralysis of the abducent nerve (a violation of the function of the external rectus muscle), for example, the right eye, the head will be turned to the right. The forced turn of the head and the inclination to the right or left shoulder during cyclotrophy (the shift of the eye to the right or to the left of the vertical meridian) is called a cortex. The eye corticollis should be differentiated from the neurogenic, orthopedic (torticollis), labyrinth (with otogenous pathology). Forced rotation of the head allows you to passively transfer the image of the fixation object to the central fossa of the retina, which eliminates doubling and provides binocular vision, although not completely perfect.
At early occurrence and long existence of paralytic strabism, the image in the mowing eye can be suppressed and diplopia disappears.
Sign of paralytic strabismus is also the inequality of the primary angle of strabismus (mowing eye) secondary angle of deflection (healthy eye). If you ask the patient to fix the point (for example, to look at the center of the ophthalmoscope) with a mowing eye, then the healthy eye will deviate to a much larger angle.
Diagnosis of paralytic strabismus
In paralytic strabismus, it is necessary to determine the affected oculomotor muscles. In preschool children, this is judged by the degree of mobility of the eyes in different directions (definition of the field of vision). In the older age, special methods are used - co-ordination and provoked diplopia.
The simplest way to determine the field of view is as follows. The patient sits opposite the doctor at a distance of 50-60 cm, the doctor fixes the head of the examinee with his left hand and suggests that he follow each eye one by one (the second eye is covered at that time) behind the movement of the object (pencil, manual ophthalmoscope, etc.) in 8 directions. The lack of muscle is judged by limiting the mobility of the eye in one direction or another. Special tables are used. With the help of this method, only pronounced limitations of eye mobility can be detected.
With a visible deviation of one eye vertically, a simple method of adduction - abduction - can be used to identify the paretic muscle. The patient is offered to look at an object, move it to the right and left, and observe whether the vertical deviation increases or decreases at the extreme directions of the gaze. Definitions of the affected muscle in this way are also carried out according to special tables.
The Chess co-ordination is based on dividing the fields of the right and left eyes with red and green filters.
To conduct the survey, a co-ordinate set is used, which includes a screen, red and green flashlights, red-green glasses. The research is carried out in a semi-dark room, on one wall of which a screen is divided, divided into small squares. The side of each square is equal to three angular degrees. In the central part of the screen there are nine marks placed in the form of a square, the position of which corresponds to the isolated physiological effect of the oculomotor muscles.
The patient in red-green glasses sits at a distance of 1 m from the screen. To study the right eye in his hand give him a red flashlight (red glass in front of the right eye). In the hands of the researcher a green flashlight, a beam of light from which he alternately directs to all nine points and suggests the patient to combine with a green light spot a light spot from a red flashlight. When trying to combine both light spots, the subject is usually mistaken for some amount. The position of a fixed green and trimmed red spot is recorded by the doctor on a chart (a sheet of millimeter paper), which is a small copy of the screen. At the time of the study, the patient's head should be immovable.
On the basis of the results of a co-ordi- nary study of one eye, one can not judge the state of the oculomotor apparatus, it is necessary to compare the results of the coordination of both eyes.
The field of the eye on the chart drawn up by the results of the study can be shortened in the direction of the action of the weakened muscle, at the same time there is a compensatory increase in the field of the eye on the healthy eye toward the action of the synergist of the affected muscle of the mowing eye.
The method of examining the oculomotor apparatus in conditions of provoked diplopia in Haabu-Lancaster is based on an estimation of the position in the space of images belonging to the fixing and deflected eye. Diplopia is caused by putting a red glass to the mowing eye, which allows simultaneously to determine which of the double images belongs to the right and to the left eye.
The scheme of the study with nine points is analogous to that used for co-ordination, but it is one (and not two). The study is conducted in a semi-dark room. At a distance of 1-2 m from the patient there is a light source. The head of the patient should be immovable.
As with coordinate measurements, the distance between the red and white images is recorded in nine positions of the eye. When interpreting the results, it is necessary to use the rule that the distance between the double images increases when looking towards the action of the affected muscle. If the field of the eye is registered with coordination (decreases with pareses), then with "provoked diplopia" - the distance between the double images, which decreases with pareses.
Treatment of paralytic strabismus
Treatment for paralytic strabismus is primarily carried out by a neurologist and pediatrician. The ophthalmologist clarifies the diagnosis, determines refraction, assigns glasses at ametropia, conducts occlusion. With light paresis, orthoptic exercises are useful. To eliminate doubling, glasses with prisms are used. Assign medication resorption and stimulant therapy. Electrical stimulation of the affected muscle and exercises aimed at developing the mobility of the eyes are performed. With persistent paralysis and paresis, surgical treatment is indicated. The operation is performed no earlier than 6-12 months after active treatment and in consultation with a neurologist.
Surgical treatment is the main type of treatment for paralytic strabismus.
Plastic surgery is often indicated. Thus, with the paralysis of the abducent nerve and the absence of movements of the eyeball outside, the upper and lower rectus muscles can be filed to the outer rectus muscle of the fibers (1 / 3-1 / 2 of the muscle width).
More difficult surgical approaches to oblique muscles, especially to the upper oblique, which is due to the complexity of its anatomical course. Different types of interventions on these as well as straight muscles of vertical action (upper and lower lines) are suggested. The latter can also be recycled (weakened) or resected (strengthened).
When performing surgery on oculomotor muscles, you must treat them with care, without disrupting the natural direction of the muscular plane, especially if it is clinically not justified. Special operations performed with complex types of strabismus can change not only the strength, but also the direction of the muscles, but before performing them, a thorough diagnostic study should be carried out.
One of the methods of treating paralytic strabismus is prismatic correction. More often it helps in the treatment of newly emerging paresis and paralysis of oculomotor muscles in adults, for example after traumatic brain injuries.
Prismatic glasses combine double images, preventing the patient from developing diplopia and involuntary rotation of the head. Paralytic strabismus can also be treated with medication and physiotherapy.