Strabismus - Treatment

The ultimate goal of treating concomitant strabismus is to restore binocular vision, since only under this condition can visual functions be restored and asymmetry in the position of the eyes be eliminated.

They use a system of complex treatment of concomitant strabismus, which includes:

• optical correction of ametropia (glasses, contact lenses);
• pleoptic treatment (pleoptics - treatment of amblyopia);
• surgical treatment;
• Orthoptodiploptic treatment aimed at restoring binocular functions (pre- and postoperative) and depth vision.

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Optical correction of strabismus

Optical correction of ametropia helps restore visual acuity and normalize the ratio of accommodation and convergence. This leads to a decrease or elimination of the angle of strabismus and ultimately helps restore binocular vision (with accommodative strabismus) or create conditions for this. Correction of ametropia is indicated for any form of strabismus. Glasses should be prescribed for constant wear under systematic visual acuity monitoring (once every 2-3 months).

Pleoptics

Pleoptics is a system of methods for treating amblyopia.

One of the traditional and main methods of pleoptic treatment is direct occlusion - switching off the healthy (fixing) eye. It creates conditions for fixation of objects by the squinting eye, including it in active visual activity and in a significant number of cases, especially with timely appointment, leads to restoration of visual acuity of the squinting eye. For this purpose, special plastic occluders are used, attached to the spectacle frame, or homemade soft curtains (curtains), as well as translucent (with varying degrees of density) occluders, since to treat amblyopia it is enough to exclude only the shaped vision.

As the visual acuity of the amblyopic eye increases, the degree of transparency of the occluder in front of the dominant eye can be increased. Translucent occlusion also promotes the development of binocular coordination of both eyes. The occlusion regimen is determined by the doctor. Occlusion is prescribed for the entire day (the occluder is removed at night), for several hours a day, or every other day, depending on the degree of visual acuity reduction.

It should be remembered that direct occlusion can lead to dysfunction and reduction of binocular cortical neurons, resulting in deterioration of binocular vision, therefore, a gradual transition to other treatment methods or the use of penalization is used. The principle of penalization (from the French penalite - a fine, a penalty) is to create artificial anisometropia in the patient using special temporary glasses. The reason for developing the method was the observation of French researchers (Pfandi, Pouliquen and Quera), who noted that amblyopia is absent in anisometropia against the background of weak myopia of one eye and emmetropia or weak hypermetropia of the other eye.

Penalization glasses "penalize" the better seeing eye. They are selected individually, while artificially creating anisometropia, for example, by hypercorrection (by 3.0 D) of the better eye with plus lenses, sometimes in combination with its atropinization. As a result, the leading eye becomes myopic and its distance vision deteriorates, while the amblyopic eye is connected to active work by full optical correction. At the same time, unlike direct occlusion, the ability to see with both eyes is preserved, so penalization is more physiological, but it is more effective at an earlier age - 3-5 years.

In combination with occlusion or separately, methods of light stimulation of the amblyopic eye are used: the method of local "blinding" stimulation of the central pit of the retina with light, developed by E. S. Avetisov, the method of successive visual images according to Küppers, illumination of the paracentral area of the retina (area of eccentric fixation) according to the Bangerter method. These methods provide a disinhibiting effect and remove the phenomenon of suppression from the central zone of the retina.

The method is chosen depending on the child’s age, the characteristics of his behavior and intelligence, and the state of visual fixation.

For treatment using the Avetisov method, which can be combined with direct occlusion, various sources of brightness are used: a light guide, laser illumination. The procedure lasts several minutes, so it can be used in young children.

The method of successive images of Küppers is based on their excitation by illuminating the fundus of the eye while simultaneously darkening the central fovea with a round test object. After illuminating, successive visual images are observed on a white screen, and their formation is stimulated by intermittent illumination of the screen. When using this method, higher demands are placed on the patient's intellect than when treating using the Avetisov method.

Treatment with the above methods, as well as with the use of general illumination, illumination through a red filter and other varieties of them, is carried out on a monobinoscope. The device allows, when fixing the child's head, to conduct an examination of the fundus, visual fixation, pleoptic and diploptical treatment under ophthalmoscopy control.

All of the above methods must be used in combination with active everyday visual training (drawing, playing with small parts such as "Mosaic", "Lego", etc.).

Laser radiation is used in pleoptic treatment in the form of reflected laser light, the so-called speckles, by observing laser "granularity" that has a stimulating effect on the retina. Domestic devices "LAR" and "MAKDEL" are used: the first is remote, the second is applied to the eyes. Laser speckles can also be used on a monobinoscope.

The listed methods make it possible to influence mainly the light and brightness sensitivity of the eye. A complex effect on various types of sensitivity in amblyopia is successfully carried out using dynamic color and frequency-contrast stimuli of varying brightness, shape and semantic content. This is implemented in special domestic computer programs "EUE" (exercises "Shooting Range", "Chase", "Crosses", "Spider" and others). The exercises are interesting for children, require their active participation. Stimulating tests are dynamic and easily changed. The principle of dynamic change of color and contrast-frequency stimuli is also used in the method based on the phenomenon of ^ interference of polarized light by A.E. Vakurina. A complex effect on various types of visual sensitivity significantly increases the effectiveness of pleoptic treatment.

Surgical treatment of strabismus

In case of strabismus, the goal of the operation is to restore symmetrical or close to it position of the eyes by changing the muscle balance. Weak muscles are strengthened or strong muscles are weakened.

Operations that weaken the action of muscles include recession (moving the muscle attachment site posterior to the anatomical one), partial myotomy (making transverse marginal incisions on both sides of the muscle), lengthening the muscle by various plastic manipulations), tenotomy (cutting the muscle tendon). Tenotomy is practically not used at present, since it can lead to a sharp limitation of the mobility of the eyeball and exclude the possibility of restoring visual functions.

In order to enhance the action of the muscle, a section of the muscle is resected (4-8 mm long, depending on the degree of dosage of the intervention and the magnitude of the angle of strabismus) or a muscle fold or a muscle tendon fold is formed - tenorrhaphy, as well as the attachment site of the muscle is moved forward (anteposition). In case of convergent strabismus, the internal rectus muscle is weakened and the external rectus muscle is strengthened; in case of divergent strabismus, the opposite actions are performed.

The basic principles of performing surgical intervention for strabismus are as follows.

• It is necessary to refuse forced interventions, to observe the principle of preliminary dosing of the operation in accordance with the existing calculation schemes. The operation is performed in stages: first on one eye, then (after 3-6 months) on the other.
• The dosed intervention is evenly distributed across several eye muscles (weakening of strong muscles, strengthening of weak muscles).
• It is essential to maintain the connection between the muscle and the eyeball during surgery on it.

Restoring the correct position of the eyes creates conditions for restoring binocular vision, which can ensure self-correction of the residual angle of strabismus in the postoperative period. For large angles of strabismus (30° or more), operations are performed in 2 (or 3) stages depending on the initial value of the angle of strabismus.

A high cosmetic and therapeutic effect is observed when using the dosage scheme of the effect of the operation developed by E. S. Avetisov and Kh. M. Makhkamova (1966). This scheme provides for a recession of the internal rectus muscle by 4 mm with a deviation according to Hirschberg of less than 10 °. A greater degree of recession often leads to a limitation of the mobility of the eyeball. With strabismus angles of 10 °, 15 °, 20 °, 25 °, this operation is performed in combination with resection (strengthening) of the antagonist - the external rectus muscle of the same eye - in a dosage of 4-5; 6; 7-8 and 9 mm, respectively. If residual deviation persists, the second stage of the operation is performed on the other eye using a similar dosage scheme no earlier than 4-6 months later. Symmetrical position of the eyes is achieved in 85% of patients and more.

A similar dosing scheme is used in operations for divergent strabismus, but in this case the external muscle is weakened (its recession is made) and the internal rectus is strengthened.

An indication for performing the operation is the lack of a therapeutic effect with constant (for 1.5-2 years) wearing of glasses (if they are indicated).

Usually, the operation is performed at the age of 4-6 years, which depends on the time of onset of the disease. In case of congenital forms of the disease and large angles of deviation of the eye, the operation is performed earlier - at 2-3 years. It is advisable to eliminate strabismus at preschool age, which contributes to the increase in the effectiveness of further functional treatment and has a beneficial effect on the restoration of visual functions.

Orthoptic and diploptic treatment of strabismus

Orthoptics and diploptics are a system of methods for restoring binocular vision, or more precisely binocular functions, the elements of which are: bifoveal fusion, fusion reserves, relative accommodation, stereo effect, depth perception of space and other functions. Orthoptics is treatment using devices with complete artificial separation of the visual fields of both eyes: each eye is presented with a separate object and set at the angle of strabismus; diploptics is treatment in natural and close to natural conditions.

Binocular exercises are carried out after achieving the maximum possible visual acuity of the squinting eye, however, a visual acuity of 0.3-0.4 is acceptable.

Orthoptic exercises are usually performed on devices with mechanical separation of the visual fields (mechanical haploscopy), the most important of which is the synoptophore (analogues - amblyophore, orthoambliophore, synoptiscope, etc.). Paired test objects for both eyes are movable and can be located at any angle of strabismus. This is a great advantage of the synoptophore over devices with fixed patterns. The synoptophore has diagnostic and therapeutic purposes. For diagnostic purposes (determination of functional scotoma, bifoveal influence), test objects for combination ("chicken and egg") or small (2.5 ° or 5 °) test objects for fusion ("cat with tail" and "cat with ears") are used. To determine functional reserves and for therapeutic purposes, large test objects for fusion (7.5 °, 10 ", etc.) are used.

The purpose of the exercises is to eliminate functional scotoma and develop bifoveal fusion (sensory fusion). Two types of exercises are used for this: alternating or simultaneous light stimulation ("blinking"). Test objects must be installed at the objective angle of strabismus, then they are projected onto the central pits of the retina. The device allows changing the blinking frequency from 2 to 8 per 1 sec, which is successively increased during the exercises.

The third type of exercises is the development of fusion reserves: horizontal (positive and negative, i.e. convergence and divergence), vertical, cycloreserves (circular). At first, large and then smaller tests for fusion are used. Exercises are prescribed both in the pre- and postoperative periods and are carried out in courses of 15-20 sessions with an interval of 2-3 months.

Orthoptic devices, despite their attractiveness and necessity (at the initial stages of treatment), limit the possibility of restoring binocular functions in natural conditions and provide a cure only in 25-30% of patients, which is due to the artificial conditions of vision on these devices. In this regard, after achieving a symmetrical position of the eyes, treatment should be carried out to restore binocular functions in "free space", without mechanical separation of the visual fields.

One of such methods is the method of binocular sequential images. It allows to restore bifoveal fusion, eliminate functional scotoma and restore binocular vision. The method can be used in combination with exercises on a synoptophore with symmetrical or close to it position of the eyes in the postoperative period. Sequential images (in the form of a circle with a right horizontal mark for the right eye and with a left mark for the left) are evoked, as in the case of the Küppers method (in the treatment of amblyopia), on a monobinoscope, but both eyes are illuminated, sequentially: first one, then the other. Then the patient observes the images evoked in each eye on a white screen with intermittent lighting and combines them into a single image. After 1-2 minutes, the illumination procedure is repeated 2 more times. The use of the method of binocular sequential images increases the effectiveness of treatment and helps to restore binocular vision.

The shortcomings of orthoptic methods have led to the development of another treatment system - diploptics. The main principle of diploptics is to eliminate the phenomenon of suppression of the visual output of the squinting eye in natural conditions by stimulating diplopia and developing a fusion reflex of bifixation.

All diploptic methods are used with both eyes open, bifoveal fusion, symmetrical or close to it position of the eyes, achieved by surgery or optical correction. There are a number of diploptic methods, in the application of which various dissociating ("provocative") techniques are used to excite diplopia.

Restoration of the bifixation mechanism using the method developed by E. S. Avetisov and T. P. Kashchenko (1976) is carried out using a prism rhythmically presented in front of one eye for 2-3 sec with an interval of 1-2 sec. The prism deflects the image of the object of fixation to the paracentral areas of the retina, which causes double vision, which is a stimulus for binocular fusion - the so-called fusion reflex (bifixation). The prism power is successively increased from 2-4 to 10-12 diopters. A series of "Diploptik" devices has been developed, which includes a set of prisms. There are devices that allow changing the prism power and the direction of its base either to the nose or to the temple in automatic mode.

The method of separating accommodation and convergence (the "dissociation" method) "teaches" binocular fusion under conditions of increasing load with negative lenses, and then under conditions of successive relaxation with positive spherical lenses. The patient overcomes the resulting double vision. The method promotes the development of not only bifixation and fusion, but also binocular (relative) accommodation, without which binocular vision is impossible. With the help of the domestic device "Forbis" it is possible to train binocular vision and relative accommodation under conditions of color, raster and polaroid separation of the visual fields.

Any diploptic exercise is performed for 15-25 minutes, 15-20 sessions are prescribed for a course. When performing the exercises, binocular vision is monitored from different working distances - 33 cm, 1 m, 5 m, with and without glasses. The reserves of relative accommodation are also monitored: the value of the transferred negative spherical lenses characterizes the positive reserves, the transferred positive lenses - the negative reserves. When using the "dissociation" method on a color tester for near vision from 33 cm (on the "Forbis" device), the negative reserves normally average +5.0 D, positive - up to 7.0 D; in patients at the initial stages of treatment they are significantly less and can be approximately +1.0 and -1.0 D.

The diploptic method of using color (red, green, etc.) filters of increasing density is realized with the help of special rulers - filters. The density (or throughput) of filters differs by an average of 5%. The weakest filter is No. 1 (5% density, or high throughput - up to 95%), the densest is No. 15 (75% density).

A ruler with light filters is placed in front of one eye of the patient (with both eyes open, as with any diploptic exercise) and the patient is asked to fixate a round glowing test object with a diameter of 1-2 cm, located at a distance of 1-2 m. After the appearance of double vision, provoked by the color filter, the patient must connect (merge) slightly different in color images of the fixation object (for example, white and pink). The density of the color filter is successively increased and binocular fusion is trained on each of them.

The first time a ruler with red filters was used by the Italian scientist V. Bagolini (1966) for diagnostic purposes. In domestic strabology, red filters are used not only for therapeutic purposes, but also to determine the stability of the achieved binocular vision. The criterion for assessing stability is the density (measured in percent) of the filter at which binocular vision is impaired and double vision occurs.

For therapeutic purposes, a set of neutral (light gray), green (blue), red and yellow filters is used. If fusion is difficult when red filters (which are also used as diagnostic filters) are presented, treatment begins with less dissociating (separating) neutral filters. After achieving binocular fusion on neutral filters (of all densities), green or blue filters are successively presented, and then red and yellow filters. This method has entered clinical practice as chromatic diploptics.

For binocular training in the diploptic treatment system, computer programs ("EYE", "Contour") are used, based on the color division of the visual fields. The exercises are exciting, playful, and ensure the active participation of the patient.

In diploptics, the method of binarimetry is also used, which consists of presenting two paired test objects on a binarimeter in free space. During the exercise, the fusion of test objects is achieved by decreasing the distance between them, bringing them closer and further away along the axis of the device (searching for a comfort zone).

In this case, a third, middle binocular image appears - an imaginary one, and in depth it is located closer or further than the device ring and can coincide with its plane when moving the frame with test objects. These exercises develop binocular, depth perception and train relative accommodation.

There are other methods of performing psi diploptic exercises. Diplopia is caused by creating artificial aniseikoria by increasing the size of one of the monocular images using a variable magnification lens. Under natural conditions, a difference in the size of images between the right and left eyes of up to 5% is tolerated, artificially induced aniseikonia in healthy people can be tolerated with a difference in the size of images of up to 50-70%, and in patients with strabismus only up to 15-20%.

The original diploptic method is based on the phase (in time) presentation of stimulating tests, first for the right eye, then for the left eye.

There is an opinion that visual information is transmitted alternately - now through the right, now through the left visual channel. A certain frequency ("phase") of such transmission is also noted, which is disrupted in various pathological conditions, for example, in strabismus. This is the basis for the method of phase haploscopy using liquid crystal glasses (LCG). When an electric impulse passes through the plates of such glasses in a certain frequency-phase mode, their transparency changes: one glass will be transparent, the other at this moment - opaque. The subject does not feel the high frequency of change of such temporary phases in the LCG (more than 80 Hz). This is the advantage of LCG compared to other methods of phase presentation of test objects.

These glasses are used in two variants. In the first, the patient must perform fascinating deep exercises "hitting the target" on a computer screen, on which drawings are presented with the same frequency, disparately located for both eyes, which creates the effect of depth. In the process of performing the exercises, the level of their complexity increases (convergence of paired drawings, reduction of depth thresholds), which helps to increase the acuity of depth vision.

The second variant uses LCD for wearing with an autonomous power supply system. In these glasses, along with the phases alternately presented to each eye, a binocular phase is included, when both eyes look through the transparent plates of the glasses, as a result of which the trainee gradually approaches the natural conditions of visual perception.

Diploptical exercises, compared to orthoptic ones, increase the effectiveness of treatment and contribute to a more significant restoration of binocular vision - from 25-30% (after orthoptics) to 60-65%, and more with early use.

Depth vision and stereo vision are trained using various depth-measuring devices and stereoscopes. Exercises using depth devices (a device for throwing balls, a three-rod Howard-Dolman device, a Litinsky device, etc.) are based on presenting a real depth difference. During the examination, the patient should not see the ends of the rods of the three-rod device (the movable middle one and two side ones standing on the same transverse line). After the middle rod has been shifted (by the researcher), the patient should place it in the same row with the side ones using a movable needle. The acuity of depth vision (in degrees or linear units) is determined by the degree of divergence of the rods. Normally, the acuity of depth vision during examination from 1-2 m is up to 1-2 cm. Depth vision is well trained in a real environment, for example, in ball games (volleyball, tennis, basketball, etc.).

The study using stereoscopes is based on the presentation of stereopair test objects with varying degrees of disparity (shift). They are used to measure the acuity of stereo vision, which depends on the size of the test objects, age and training level of the subject. In healthy individuals, it is 10-30 (angular seconds).

In diplooptic treatment, a certain role is given to prismatic glasses. Prismatic lenses, as is known, refract a light beam, shifting the image of the object of fixation on the retina towards the base of the prism. In the presence of small or residual angles of strabismus in the postoperative period, prismatic glasses are prescribed for wearing along with diplooptic treatment. As the angle of strabismus decreases, the strength of the prismatic lenses is reduced, and then the glasses are canceled.

Prisms are also used to develop fusion reserves in "free space". It is convenient to use a Landolt-Herschel type biprism, the design of which allows for a smooth increase (or decrease) of its prismatic action by rotating the disk.

A domestically produced biprism (OKP - ophthalmocompensator prism) can be fixed in a special device or spectacle frame. Changing the direction of the prism base to the temple promotes the development of positive fusion reserves, to the nose - negative.