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CONSERVATIVE METHODS OF AMBLYOPIA AND STRABISMUS TREATMENT

Optical correction is one of the oldest methods of vision correction. Usually it is utilized at the initial stage of the treatment of amblyopia, strabismus and refractive disorders. It helps stimulate visual functions in children, contributing to the normalization of binocular functions development. Using optical correction is possible from the age of 6 months old. Objective parameters of cycloplegic refraction must be taken into account. Cycloplegia allows to “turn off” accommodation process temporarily in order to evaluate the refraction in the child carefully and precisely. The doctor evaluates all the data obtained, takes into account the existing complaints of parents and patient to choose the appropriate treatment.

There are several options of optical correction:

1. Spectacles – one of the most popular method of optical correction in children of preschool age

Indications:

 

Contraindications:

 

Fitting and use:

 

Fitting is carried out in one or several stages, depending on the age of the child and the existing vision disorders.

The first stage is the assessment of refraction under conditions of cycloplegia (wide pupil, induced paralysis of the ciliary muscle). For cycloplegia, a 1% cycloplentolate solution or 0.1-1% atropine solution is used. The most common instillation scheme is as follows: 1 drop in both eyes (twofold) with an interval of 10-15 minutes. Sometimes, the doctor may prescribe instillation of this drug at home for 3-5 days in cases of:

The second stage is fitting in order to check visual acuity taking into account the obtained values ​​of refraction, assessment of refraction after 3-5 days of cycloplegia, assessing the position of the eyes with objective correction (when lenses’ power is not taking into account visual acuity) in children with strabismus.

The duration of wearing spectacles is determined by the doctor depending on the pathology, but most often ophthalmologists advocate the principle of constant wearing with follow-up visits once every 2-3 months. During these visits, the position of the eyes, visual acuity and the overall state of the child are assessed.

2. Contact lenses vision correction. Some parents still consider contact lenses harmful to chilren’s eyes, but any ophthalmologist or optometrist will say that this is not the case. Advancement of contact lens materials and possibility of customization allow doctors fit contact lenses in children as young as several months old.

Indications:

Contraindications:

Fitting and use

The approach is patient-specific. Most optometrists consider that for children, especially young, the best option is to use daily replacement soft contact lenses or frequent replacement lenses (replacement is more frequent than once a month). Such lenses minimize the risk of secondary complications (conjunctivitis, keratitis), which may be due to improper care of the lenses during scheduled replacement or violations of the lens installation technique. The latter is most applicable to parents who help or fit contact lenses in children themselves. It was revealed that children are able to look after contact lenses better than many adults. Scheduled replacement lenses (replacement is less frequent than once a month) or extended wear contact lenses can also be used in children, but the using such lenses requires an even more careful monitoring, due to a relatively higher risk of complications.

Fitting contact lenses in children of 6-7 years old is not very different from fitting lenses in adult patients. In children of a younger age group, the fitting is often carried out empirically when the doctor evaluates several main parameters:

After the examination, necessary parameters of the contact lenses are calculated (base curvature – BC and lens diameter – Dia). Fitting soft contact lenses is carried out without instillation of drugs that dilate the pupil. Leneses are fit (by the doctor himself), then the fit, lens mobility and centration are evaluated. If necessary, the lens parameters are changed and a second examination is carried out.

In infants, this fitting method is not applicable and usually, after calculation of lens parameters, the doctor fits lenses, assesses the fit, instructs parents regarding the lens installation and removal technique and schedules a second appointment to evaluate how well treatment was working.

3. Vision therapy

A set of various exercises and physical therapy that help normalize and stimulate visual functions. The choice of a particular treatment depends on the vision disorder. In Russia, several types of vision therapy are usually distinguished:

a. Pleoptic treatment – system of methods aimed at the treatment of amblyopia:

 i. Occlusion – the method the essence of which is to cover (occlude) a better seeing eye to improve the vision in the lazy eye. It is important to explain to parents that this procedure does not correct refractive errors and does not cure strabismus, which was the reason for the formation of amblyopia. Occlusion is best used in conjunction with optical correction.

Principles of use

The use of occlusion is possible from the very birth, if the doctor has identified the appropriate indications – congenital strabismus, severe refractive errors (high hyperopia, high myopia, anisometropia).

Specialists distinguish:

Occlusion types:

Occlusion duration:

The duration and type of occlusion is determined for each patient individually and may vary during treatment based on its course. The most common occluders are made of plastic that are attached to the spectacle frame, or various home-made occluders of various types. Occluders can be opaque, translucent, depending on the task and the psychological state of the child.

In most cases, occlusion therapy requires incredible patience as children tend to put off the occluders, glasses with occluders, especially in cases of severe degrees of amblyopia (visual acuity < 0.1), which negatively affects the healing process. In this case, the doctor can choose the so-called "occluding contact lenses" These are soft contact lenses that are colored in a central optical zone either partly (from 3 mm) or fully (up to 12.5 mm). This method was first tested in the USA and is being successfully applied at present.

The research has shown significant efficacy of utilizing such lenses and an improvement in children’s adherence to treatment, due to a decrease in cosmetic discomfort compared to wearing patches (Collins, McChesney et al, 2008).

Specifics of the method

In cases of a full-time monocular occlusion, visual acuity of the better seeing eye may decrease. In such cases, it is advisable to switch to alternate occlusion. Alternating occlusion schemes imply, for example, 6 days occlusion of a better seeing eye and 1 day occlusion of an amblyopic eye.

Occlusion therapy is performed in series of repeated courses, each lasting at least 2-3 weeks, depending on the severity of amblyopia and the presence or absence of visual fixation disorders. Courses can be repeated up to 6 times a year, depending on the observed dynamics.

Occlusion does not treat strabismus, but it improves and evens out the visual acuity of both eyes, which is usually a good sign and increases the likelihood of maintaining the correct position of the eyes after surgical treatment. After occlusion therapy is cancelled, visual acuity of the squinting eye may again deteriorate, albeit slightly.

It is important to keep in mind that a prolonged occlusion can disrupt binocular functions, so it is important to use the tactics of a gradual transition to other stages and methods of treatment such as penalization. Recommended duration of a single course of occlusion therapy is 14-20 days.

 ii. Penalization is a method of pleoptic treatment of amblyopia, which implies creation of artificial anisometropia (difference in refraction between the eyes greater than 1 diopter), which leads to a decrease in visual acuity of the dominant eye and the development of visual fixation in an amblyopic eye.

Principles of use

A distinctive feature of penalization is that the better seeing eye maintains spatial perception and remains uncovered while its visual acuity decreases. This result can be achieved in the following ways:

Specifics of the method

This method allows you to connect the amblyopic eye to active work and not exclude (as in case of occlusion) the fixing eye from seeing. In case of a severe amblyopia (visual acuity of the amblyopic eye lower than 0.1), the child may refuse to use the classic occlude. In this case, penalization may be the best and sometimes the only applicable method of pleoptic treatment.

 iii. After-image method – use of images occuring after a blinding retinal glare and visible with eyes open and closed

The visible image will correspond to the source that caused this blinding light (for example, the flash of the camera, the letters of the board, the bright light of the lamp). After light, during blinking, the alternation of light (negative) and dark (positive) sequential images takes place.

Principles of use

The child is wearing an occludor on the better seeing eye, spectacles are put on; then the gaze is fixated on a round black mark located on a white, luminous screen from at distance of about 10-15 cm. The child looks at the fixation mark during 20-30 seconds to blind the peripheral retina.

After turning off the screen, the child can return to his or her activities, you can even ask to draw an image that is now visible. When blinking, images alternate from positive (dark) to negative (light).

The procedure is repeated after the child noted the disappearance of the visible image. On average, up to 30 exposures take place during one session. Up to 15-20 sessions per day can be performed. The duration of each session is within 60 minutes. The duration this treatment depends on the results obtained and the overall treatment dynamics.

Specifics of the method

The need for a good intellectual level of development of the child to understand the consequences of this method. Therefore, this method is not most commonly used.

 iv. Red light therapy – method based on the fact that red light selectively stimulates the cones of the retina. Thus, the fovea with its exclusive cone component is predominantly stimulated by the light which passes through a red filter.

It is recommended for patients:

Treatment is performed under conditions of a full correction, with occlusion, 1-2 times a day during 60 minutes. During the procedure, the most important thing is to maintain the activity of the child.

 v. Cross-strobing (by Pospelov) is used for treatment of strabismus. It is based on the principle of the aspiration of the human brain to combine received, slightly heterogeneous images into a single image.

This mechanism is disturbed in children with strabismus, when the brain receives pronounced asymmetric visual information from both eyes, which leads to further suppression of the image from the squinting eye and there is an alternate perception of the right or left image. Contraindication for this method is a pronounced eccentric (off-center) visual fixation.

Principles of use

The treatment method is very easy to use and is often prescribed for home practice. A flashlight (preferably a diode) is covered in front by an opaque shutter with a slot, like a keyhole. Parents are asked to fix the child’s gaze on the switched on flashlight – which is located 10-15 cm away – through the center of the keyhole. The duration of fixation is 20-30 seconds, for one eye the keyhole is horizontal, while for the other it is vertical. After exposure, the child is asked to close his eyes and, in order for him to recognize the obtained images, direct the light from the flashlight to his eyes. When the child understands what he sees, they ask him to open his eyes and sketch the picture he saw, according to which his perception is evaluated. Treatment is successful if, according to the results of the courses, the child sees a figure in the form of a cross (+) and can hold images in the form of this figure for some time. This indicates the achievement of a bifoveal fusion and the absence of physiological and pathological blind spots in the field of view of the child, even in the presence of strabismus.

A similar method is used after surgical treatment as an additional method of stimulation.

General contraindications:

 vi. Laser speckle contrast imaging (LSCI) is based on the use of low-intensity laser radiation projected into the central zone of the retina (macula) and has a tangible stimulating effect, which contributes to the improvement of visual functions.

Principles of use

This method is not applicable for home use and is an integral part of the vision therapy cabinets. The main principle of treatment by laser stimulation devices is that the child fixes his gaze on the sources of laser radiation fixed at various distances (depending on the settings of the device, the installed power and the degree of vision disorder), guided by the doctor or nurse throughout the course of treatment. The duration of one session does not exceed 10 minutes, 1 course comprises from 10 to 15 sessions, depending on the severity of vision disorder and the child’s readiness for similar medical procedures. During the treatment process, in addition to the distance to the laser radiation source, the doctor or nurse can change the power and frequency of the laser radiation to enhance the therapeutic effect.

Specifics of the method

This treatment method requires careful selection of patients, since a long fixation at one point is required during the treatment process, which is not possible for all young patients, even under the supervision of a specialist and parents. Without proper attention and interest of the child, the laser will not be able to focus on the central area of ​​the retina and the effect of the treatment will be extremely low.

In most cases, laser stimulation does not act as the leading and only treatment, and is usually prescribed in combination with other methods.

Contraindications

Psychogenic factors, hyperactivity, age under 4-5 years, presence of concomitant neurological disorders, impaired transparency of the optical media of the eye (after injuries, surgical interventions, inflammatory processes).

 vii. Stimulation methods utilizing digital devices. These methods are relatively young and have recently started attracting attention of ophthalmologists around the world. The development of multimedia technologies encourages creation of more and more portable gadgets that attract the attention and help treatment of the visual system. Some gadgets not only help develop visual functions, but also motor skills, enhance perseverance, which also positively affects the overall results of treatment.

b. Orthoptic therapy is a program of eye exercises designed to help people with eye-focusing problems. These exercises are mostly prescribed for children with convergence and/or accommodative insufficiency.

This method is usually a next step after occlusion or penalization, since the main condition for orthoptic treatment is the presence of almost symmetric indicators of visual acuity in both eyes. Orthoptic treatment is carried out under conditions of haploscopy (separation of the visual fields of the right and left eye).

Synoptophore – a device designed for the diagnosis and treatment of various types of oculomotor disorders (strabismus). The device utilizes principle of artificial separation of visual fields (haploscopy) by presenting various test objects separately for each eye through special optical heads. In orthoptics, in addition to diagnostic aspects, a synoptophore is used for developing the amplitude of eye movements, develop fusional reserves (reserves that allow you to keep two different images visible by the right and left eye), stimulate and maintain binocular functions (eliminate functional blind spots, asymmetric binocular vision, bifoveal image merging).

Principles of use

The device is applicable if visual acuity in both eyes is not lower than 0.4 (as per decimal scale) and the difference between the visual acuity of both eyes does not exceed 1 line. Initially, the following parameters are determined:

These are two main parameters, based on which the doctor suggests a treatment plan and evaluates the prospect of a further need for a surgical treatment. Since the synoptophore does not correct strabismus, it creates artificial conditions for enhancement of binocular functions, thereby it trains the visual analyzer and prepares for the simultaneous perception of two images after surgical treatment, when both eyes will be in the correct position.

If such stimulation was not performed in a timely manner or was not performed at all, after surgical treatment there may be a relapse and resumption of the strabismus angle, since the eye does not take into account the images entering the squinting eye.

Having determined the objective and subjective strabismus angle, the doctor compares the results obtained, which is important for assessing the prospects of treatment:

The minimum number of sessions is 15-20 per course. To achieve long lasting positive results, at least 4 courses per year are required, especially considering the fact that the first course is always introductory to the child and the effect of its implementation is minimal.

Specifics of the method

Therapeutic tactics are based on subjective indications (responses of the child), which affects the results of treatment and diagnostics, as well as the results of repeated studies, when the values ​​obtained change. Other features of the device include its limited effect on the oculomotor system. Usually doctors can most effectively influence the oculomotor system and improve binocular functions in children up to 3-4 years old, however this device cannot be used in patients that young, since verbal contact with the child is difficult and the specialist cannot obtain the results of the subjective strabismus angle. At an older age, chances of dramatically affecting binocular functions are reduced and the synoptophore gains more diagnostic value than therapeutic value.

Contraindications

c. Diploptic treatment is a term first proposed in the 1980s by academician E.S. Avetisov, describing a set of measures aimed at restoring, developing and stabilizing a normal binocular vision (in children with normal retinal correspondence).

Unlike orthoptic treatment, diploptic treatment is performed in natural conditions, without separation of the fields of view (haploscopy). Treatment suggests achieving of doubling (diplopia) by irritating various parts of the retina with the help of prisms and developing the ability to merge double images. The main condition and indication for diploptic treatment is the visual acuity of both eyes of at least 0.5 (as per decimal scale) and the presence of a bifoveal fusion.

There are several methods of diplopic treatment:

 i. A training method with prismatic lenses. One of the main methods of diploptic treatment using trial prismatic lenses, conventionally divided into several stages:

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