Strabismus diagnosis

Evaluation of the state of the oculomotor apparatus involves the study of both sensory (sensory) and motor (motor) functions.

When staging a diagnosis of strabismus, one must also take into account the history

1. The time of onset can indicate the etiology of strabismus. The earlier the strabismus arose, the more likely a need for surgical removal. The later there was a squint, the more likely the accommodation component. Evaluation of previous photographs can be useful for documenting strabismus or involuntary head position.
2. The variability of the angle is an important criterion, since periodic strabismus indicates a certain safety of binocular vision. Alternating strabismus suggests a symmetrical visual acuity in both eyes.
3. The general condition or developmental abnormalities have a sign (for example, the frequency of strabismus in children with infantile cerebral palsy).
4. Anamnesis of childbirth, including the period of pregnancy, weight at birth, pathology of prenatal development or during childbirth.
5. Hereditary anamnesis is important, since often strabismus is a hereditary pathology, although a certain type of inheritance is not found. It is necessary to know what treatment was given to other family members.

The study of sensory functions includes the definition of binocular vision and the degree of its stability, deep (or stereoscopic) vision, its severity, presence or absence of bifoveal fusion, fusional reserves, functional scotoma of suppression, the nature of diplopia.

In the study of motor functions determine the mobility of eyeballs, the magnitude of deviation, the degree of impairment of the functions of various oculomotor muscles.

When collecting anamnesis, it is necessary to find out at what age the strabismus appeared, the probable cause of its development, the presence of traumas and the transferred diseases, whether one eye always mowed or alternating deflection of both eyes, the nature of treatment, the duration of wearing glasses was manifested.

The study of visual acuity should be carried out with glasses and without them, as well as with two open eyes, which is especially important in nystagmus.

In addition to general ophthalmological research, special methods are used.

To determine the pattern of strabismus (monolateral, alternating), a fixation test should be performed: cover with the palm resting eye (for example, right) of the subject and ask him to look at the end of the pencil or pen of the ophthalmoscope. When the rejected eye (left) begins to fix the object, remove the palm and leave the right eye open. If the left eye continues to fix the end of the pencil, then the subject has an alternating strabismus, and if the left eye again mows with two open eyes, then the squint is monolateral.

The form of strabismus and the magnitude of deviation (angle of strabismus) are determined in the direction of the eye's deflection (convergent, divergent, vertical).

The angle of strabismus can be determined by the Hirschberg method. The doctor, applying a manual ophthalmoscope to his eye, asks the patient to look into the opening of the ophthalmoscope and watches the position of light reflexes on the cornea of both eyes of the patient from a distance of 35-40 cm. The magnitude of the angle is judged by the mixing of the reflex from the center of the cornea of the mowing eye in relation to the pupillary margin iris and limbus with an average pupil width of 3 - 3.5 mm. With convergent strabismus orientate along the outer edge of the pupil, and when divergent, they are oriented along the inner edge.

The mobility of the eyes is determined by moving the fixation object, followed by the patient's eyes, in eight directions of vision: right, left, up, down, up-right, up-left, down-right, down-left. With a friendly strabismus, the eyes move in full enough. With paralytic strabismus, it is advisable to use special methods - co-ordination and provoked diplopia, to identify the affected muscle.

With vertical deviation, the angle of strabismus in lateral positions is determined, with adduction and abduction. An increase in the angle of vertical strabismus with adduction indicates a lesion of oblique muscles, with abduction - the direct muscles of vertical action.

In the presence of amblyopia, the state of visual fixation on a monobinoscope is assessed - one of the main instruments used to study and treat strabismus. The device is designed according to the type of the Gulshtrand stationary ophthalmoscope, which allows, when fixing the child's head, to perform an examination of the fundus, determine the state of visual fixation, and perform medical procedures. The child looks at the end of the fixation rod ("needle") of a monobinoscope, the shadow of which is projected (on the fundus) onto the fixation site.

Methods of examining binocular functions with strabismus are based on the principle of separation of the visual field of the right and left eyes (haploscopy), which allows to identify the involvement (or non-participation) of the mowing eye in binocular vision. Haploscopy can be mechanical, color, raster, etc.

One of the main haploscopic devices is synoptophor. The separation of the visual fields of the right and left eyes in this device is carried out mechanically, using two (separate for each eye) mobile optical tubes, by which the test subject is presented with paired test objects.

The test objects of the synoptophor can be moved (horizontally, vertically, torsionally, i.e. Clockwise and counterclockwise) and set according to the angle of strabismus. They differ in control elements for each eye, which makes it possible to judge the presence or absence of binocular fusion, that is, fusions, and in its absence, about the presence of a functional scotoma (when the part or the entire figure disappears, when combining the paired (right and left) patterns) before the mowing eye). In the presence of a confluence, fusional reserves are determined by reducing or diluting the test objects (optical tubes of synoptophore) until the test object is doubled. When converging the synoptophor tubes, positive fusional reserves (convergence reserves) are determined, while dilution, negative fusional reserves (reserves of divergence) are determined.

The most significant are positive fusional reserves. When tested on synoptophor with test No. 2 ("cat") in healthy individuals, they are 16 ± 8 °, negative - 5 + 2 °, vertical - 2-4 prism diopters (1-2 °). Torsion reserves are: inclines (at the inclination of the vertical meridian of the figure to the nose) - 14 ± 2 °, the exclocreparations (with the inclination to the temple) - 12 + 2 °.

Fusional reserves depend on the research conditions (using different methods - synoptophore or prism), the size of the test objects, their orientation (vertical or horizontal) and other factors that are taken into account in determining the tactics of treatment.

To study binocular vision under natural and close conditions, methods based on color, polaroid or raster separation of fields of vision are used. For this purpose, for example, red and green light filters (red in front of one, green in front of the other eye), polaroid filters with vertically and horizontally oriented axes, raster filters of mutually perpendicular orientation for both eyes are used. The use of these methods allows one to answer the question of the nature of vision in the patient: binocular, simultaneous (diplopia) or monocular.

The color four-point color test of Bialystok - Friedman has two green (or blue) circles, one red and one white circle. The subject looks through the red-green glasses: before the right eye is a red filter, in front of the left - green (or blue). The average white circle, visible through the red and green filters of the glasses, will be perceived as green or red, depending on the predominance of the right or left eye. With monocular vision of the right eye through the red glass, the subject sees only red circles (there are two), with monocular vision of the left eye - only green (three of them). With simultaneous vision, he sees five circles: two red and three green, with binocular - four mugs: two red and two green.

When using polaroid or raster filters (the so-called Bagolini glasses), as well as in a color device, there is a common object for merging and objects visible only to the right or just the left eye.

Methods of examining binocular vision differ in the degree of dissociative ("dissociating") action: it is more pronounced in a color device, less in a polaroid test and in raster glasses, since the conditions for vision are closer to natural ones.

When using raster glasses, all the surrounding space is visible, as in natural conditions (unlike the view in color red-green glasses), and the uncoupling action of the rasters is manifested only by thin, mutually perpendicular light strips passing through a common round light source-the fixation object. Therefore, when examining different methods in the same patient, one can identify simultaneous vision on a four-point test and a binocular test - in Bagolini raster glasses. This must be remembered when assessing the binocular status and for determining therapeutic tactics.

There are various depth-vision devices and stereoscopes that allow to determine the sharpness and thresholds (in degrees or linear magnitudes) of deep and stereoscopic view. In this case, the examinee must correctly assess or locate the test objects, which are displaced in depth. By the degree of error, the sharpness of the stereo vision in angular or linear magnitudes will be determined.

Divergent friendly strabismus is a more favorable form of oculomotor disorders than convergent, it is less often accompanied by amblyopia. Disturbances of the binocular vision are manifested with a diverging strabismus in a lighter form, mainly a lack of convergence is revealed.

[1], [2], [3], [4], [5], [6], [7]