Concomitant strabismus: clinical guidelines

List of Abbreviations

ARC – abnormal retinal correspondence

D – diopter

ICD-10 – International Classification of Diseases 10th Revision

pdpt – prism diopter

arcmin – arcminute

CNS – central nervous system

Terms and Definitions

Amblyopia — a symptom complex based on mono- or binocular decrease in visual functions without visible organic lesions of the visual analyzer, which developed as a result of sensory deprivation during the period of visual system formation.

ARC — sensory cooperation between the central fovea of the fixing eye and the paracentral retinal area of the squinting eye, accompanied by the appearance of asymmetric binocular vision, possible in microstrabismus.

Binocular vision — the ability of the visual analyzer to compare two optical images of the observed visual scene formed on the retinas of the right and left eyes, taking into account the positions of the two eyes when fixing an object.

Haploscopy — separation of the visual fields of the two eyes.

Diploptics — a method of treating strabismus, based on eliminating the phenomenon of visual image suppression of the squinting eye under natural conditions by inducing diplopia and developing the fusion reflex of bifixation.

Visual fixation — a relatively immobile setting of gaze on the object being viewed.

Strabismus — deviation of the eye from the common fixation point, accompanied by impaired binocular functions.

Simultaneous vision is the ability to perceive an object with both eyes simultaneously.

Orthoptics is a system of therapeutic methods aimed at restoring bifoveal fusion by eliminating functional inhibition (functional scotoma) under conditions of mechanical haploscopy.

Pleoptics (pleoptic treatment) is a system of therapeutic methods aimed at increasing visual acuity in amblyopia.

Concomitant strabismus is a form of oculomotor and visual disorders characterized by the deviation of the eye from the common fixation point, leading to impaired binocular vision. In concomitant strabismus, the functions of individual muscles are not impaired.

Suppression is functional inhibition resulting from the active suppression by the visual cortex of the image coming from one eye when both eyes are open, manifesting as a functional scotoma.

1. Brief information on the disease or condition

1.1 Definition of the disease or condition

Concomitant strabismus – a form of oculomotor and visual disorders characterized by the deviation of the eye from the common fixation point, leading to impaired binocular vision. In concomitant strabismus, the functions of individual muscles are not impaired.

Convergent strabismus (esotropia) is the deviation of the visual axis inward. The most frequent form of concomitant strabismus (70-80% of cases).

Divergent strabismus (exotropia) is the deviation of the visual axis outward (15-20% of cases). Divergent concomitant strabismus is less common than convergent strabismus and is characterized by a later onset and lower frequency of sensory disturbances [1-7].

1.2 Etiology and pathogenesis of the disease or condition (group of diseases or conditions)

Concomitant strabismus is polyetiological in nature [1,2,5-11].

The following etiological factors of concomitant strabismus are distinguished:

• Congenital and acquired CNS diseases.

• General infections.

• Psychological traumas.

• Decreased vision or blindness of one eye.

• Congenital defects of binocular vision.

Heredity plays a major role in the development of strabismus. Both strabismus and predisposing features are inherited: absence or weakness of fusion, refractive errors, anisometropia, astigmatism, etc. [12]. Embryopathies and phenopathies play a significant role: toxic, infectious, radiation effects, metabolic disorders, rhesus incompatibility. Complicated labor aggravates genetic and embryonic prerequisites for strabismus and, in combination with them or by itself, creates prerequisites for the development of strabismus [13,14].

In the pathogenesis of concomitant strabismus in children, sensory adaptation to such pathological conditions as diplopia and confusion plays a leading role, which is most often carried out through the mechanism of suppression. The emergence of suppression is associated with the plasticity of the developing visual system in children under 6-8 years of age.

Suppression (functional inhibition) occurs as a result of active suppression by the visual cortex of the image coming from one eye with both eyes open. Stimuli for suppression include diplopia, confusion, defocused image in astigmatism or anisometropia. With the long-term existence of functional inhibition, the chances of restoring binocular functions in children, even upon achieving a symmetrical position after surgical intervention, are small [1,2,12,15].

Another form of adaptation of the visual system to the asymmetrical position of the eyes is anomalous retinal correspondence (ARC). ARC refers to cases where the central fovea of the fixing eye corresponds to a paracentral area of the retina of the squinting eye, which is accompanied by the appearance of asymmetrical binocular vision. It is believed that such cooperation is possible only in microstrabismus [1,2,16,17,18].

1.3 Epidemiology of the Disease or Condition

Concomitant strabismus ranks second after refractive errors among pediatric ocular pathology [11]. The prevalence of concomitant strabismus ranges from 1.5–2.0% [1,2,8] to 3.5-5% [11,19]. There are at least 10 million patients with strabismus worldwide [19]. In 60–70% of cases, the pathology occurs at the age under 2 years [1,2].

1.4 Features of Coding the Disease or Condition

H50.0 - Convergent concomitant strabismus

H50.1 - Divergent concomitant strabismus

1.5 Classification of the disease or condition

Clinical classification of concomitant strabismus [1,2,3,4,8,19]

By the direction of deviation of the squinting eye:

convergent strabismus (esotropia) – deviation of the squinting eye toward the nose;

divergent strabismus (exotropia) – deviation of the squinting eye toward the temple.

By the character of eye deviation:

unilateral or monolateral strabismus, when one eye constantly squints;

alternating strabismus, when first one and then the other eye alternately squints.

By the degree of accommodation involvement:

accommodative;

partially accommodative;

non-accommodative strabismus.

By the duration of manifestation

intermittent;

constant

1.6 Clinical presentation of the disease or condition

In concomitant strabismus, patients' complaints boil down to periodic or constant deviation of the eyes, deterioration of visual acuity, most often of the squinting eye. When strabismus occurs at the age over 5-6 years, patients complain of double vision of surrounding objects.

Strabismus usually occurs at the age of two to three years, suddenly or gradually against the background of a previous viral infection, psychological stress, severe fright, and often without apparent cause. The congenital form of concomitant strabismus is usually associated with the pathology of pregnancy and childbirth.

Visual inspection reveals constant or periodic deviation of one or alternately two eyes inward or outward, eye mobility is preserved in full.

Visual acuity testing may reveal a decrease in corrected visual acuity, which indicates the presence of concomitant amblyopia.

Objective refraction testing under conditions of cycloplegia reveals various types of ametropia: hyperopia, myopia, astigmatism. In convergent strabismus, hyperopia is more often detected, while in divergent strabismus, myopia is more common.

Examination of the binocular status reveals impaired binocular vision: monocular or simultaneous vision. Examination on a synoptophore often reveals a functional scotoma.

In the majority of patients with concomitant strabismus, the anterior segment of the eye is unchanged, media are transparent, and no pathological changes are detected in the fundus. However, decreased visual acuity due to other eye diseases detected during the examination of a patient with strabismus can serve as a cause of concomitant strabismus development [1,2,4,5,6,7,10,12,15,18,19].

2. Diagnostics, medical indications and contraindications for diagnostic methods

Criteria for establishing concomitant strabismus: constant or periodic deviation of one or alternately two eyes inward or outward with preservation of eye mobility and/or impaired binocular vision.

2.1 Complaints and Anamnesis

For adults: Grade of Recommendation C (Level of Evidence – 5).

Comments: assess the time of onset of strabismus (age of onset, sudden or gradual); duration of strabismus; potential contributing factors (general diseases, psychological trauma, eye diseases, maternal pregnancy and childbirth pathology); whether the strabismus is constant or intermittent; age at which glasses were first worn, whether worn constantly or intermittently, and the effect of glasses on eye position; prior treatments received (surgical, functional); general health status of the patient; and central nervous system status.

2.2 Physical Examination

Comments: depending on the side affected, strabismus is classified as right-sided, left-sided, or bilateral; depending on the direction of eye deviation, it is classified as convergent or divergent [1,2,4,5,6,7,10,12,15,18,19].

2.3 Laboratory Diagnostics

Laboratory diagnostic tests are not performed for concomitant strabismus.

2.4 Instrumental Diagnostics

Comments: visometry in children under three years of age is performed approximately – determining whether the child has object vision. More precise measurement is possible using the preferential looking test, optokinetic nystagmus recording methods, and visual evoked potentials. Visometry in children aged three years and older is performed using charts: from 3 years of age using a chart with silhouette pictures for children, and from 5 years of age using Landolt rings or "E" tests. Visual acuity is determined by the chart row in which all symbols are correctly recognized [25,26].

Comments: autorefractometry and autorefractokeratometry are reliable methods for diagnosing refractive errors. The method allows for rapid and accurate measurement of refraction in adults and children over three years of age with both narrow and wide pupils. In children over one year of age, the examination is possible using a handheld modification of the autorefractometer; in children under 1 year of age, a pediatric remote autorefractometer can be used [25,27].

Comments: skiascopy (retinoscopy) using a flat mirror of a handheld mirror ophthalmoscope or an electric ophthalmoscope is a reliable method for assessing refraction, but it has low accuracy in diagnosing astigmatism, particularly its main meridians [23,25,31].

Comments: 1% cyclopentolate is instilled as 1–2 drops twice with an interval of 15–20 minutes. Instillation into the conjunctival sac of 1–2 drops of 0.5% or 1% tropicamide** twice with an interval of 5 minutes induces less deep cycloplegia than cyclopentolate [32,33]. According to the instructions, 0.5% tropicamide** should be used with caution in infants; 1% tropicamide** is contraindicated in children under 6 years of age.

Comments: measurement of the angle of strabismus in young children is possible using a remote pediatric autorefractometer [27,29].

Comments: to determine ocular motility, a fixation target followed by the patient's eyes is moved in eight gaze directions: right, left, up, down, up-right, up-left, down-right, and down-left. In concomitant strabismus, the eyes move in full range. To rule out non-concomitant strabismus, the functions of all extraocular muscles are assessed.

Comments: evaluation of binocular functions includes assessing binocular vision, its stability, depth or stereoscopic vision, visual acuity, presence or absence of bifoveal fusion, fusional reserves, functional suppression scotoma, the nature of diplopia, and other functions [1,2,34].

Methods for examining binocular functions in strabismus are based on the principle of separation of visual fields (haploscopy). This allows for the identification of the participation (or non-participation) of the strabismic eye in binocular vision. Haploscopy can be mechanical, color-based, raster-based, polarization-based, and phase-based (temporal) [2,8,34]. In clinical practice, mechanical, color, and polarization haploscopy are most commonly used.

Mechanical haploscopy is used in a synoptophore. In this device, the separation of the visual fields of the right and left eyes is carried out by means of two separate movable optical tubes for each eye, in each of which the subject is presented with paired test objects for alignment and fusion. The synoptophore is used to determine the angle of strabismus (subjective and objective), the capacity for binocular (bifoveal) image fusion, fusional reserves, and the presence or absence of a functional scotoma. The synoptophore contains three pairs of test objects: for alignment, fusion, and stereoscopy. The synoptophore test objects can be moved horizontally, vertically, and torsionally (by tilting sideways). The device is also used for therapeutic orthoptic exercises [2,6,8,34].

In healthy individuals, positive fusional reserves have the largest magnitude, negative reserves are substantially smaller than positive ones, and vertical fusional reserves are even smaller. The magnitude of in- and excyclorerves is close to the values of positive fusional reserves [6,34].

Color haploscopy is performed by presenting the patient with four objects: two green, one red, and one white under conditions of color separation of the visual fields – a red light filter is placed in front of the patient's right eye and a green one in front of the left. The Worth test (Worthtest) or the Belostotsky-Friedman four-dot color test is used [2,5,6,34].

Polarization haploscopy is achieved by presenting test objects in polarized light and using polarizing filters. Due to the polarization separation of the visual fields, the presented test objects are seen separately by the right and left eyes. Some tests also contain a common fixation object [2,23].

Comments: based on patient questioning, it is necessary to determine the type of diplopia: constant or intermittent, horizontal, vertical, or combined, manifesting when looking into the distance and/or near.

2.5 Other Procedures

3. Treatment, including drug and non-drug therapies, diet therapy, and pain management

3.1 Optical correction

Optical correction is the first and mandatory stage of concomitant strabismus treatment. Subsequent stages of concomitant strabismus treatment are undertaken after the compensation of refractive errors [1,2,8,18,23,42].

Comments: in esotropia, which is more commonly accompanied by hyperopia, positive lenses reduce accommodation effort. This weakens the convergence impulse and helps reduce or eliminate the deviation.

Constant hyperopia correction close to full is prescribed: for infants in the first year of life at 6-9 months of age, 1.0-2.0 D weaker than the cycloplegic refraction [42,43]; for older children, no more than 1.0 D weaker than the cycloplegic refraction [1,8,42,44]; for adults, the maximum tolerated positive correction [23,42].

Constant or intermittent exotropia combined with myopia generally requires full optical correction [23,42,45].

Comments: prismatic correction is implemented in the form of spectacles with prismatic power or elastic Fresnel prisms.

3.2 Functional treatment

Comments: one or more pleoptic treatment methods are used to treat amblyopia: occlusion or penalization, local macular dazzling according to E.S. Avetisov, Cuppers' negative successive images method, Campbell's method based on contrast sensitivity training, localization methods, reflexology, and other stimulation methods.

Comments: to achieve bifoveal fusion on the synoptophore, light stimulation (flashing) methods are used at the objective angle (OA) using fusion tests of various sizes: alternating and simultaneous. After achieving bifoveal fusion on the synoptophore, the process moves on to developing fusional reserves: positive for exotropia, negative for esotropia. fusion test objects. Exercises are prescribed both in the pre- and postoperative periods and are performed in courses of 15–20 sessions at intervals of 2–3 months [1,2,6,34].

Comments: an eye position close to symmetrical can be achieved as a result of surgical treatment of strabismus or optical correction. Bifoveolar fusion – as a result of synoptophore exercises (orthoptics).

Indications for diploptic treatment include: symmetrical or near-symmetrical eye position (up to 5-10 degrees according to Hirschberg), presence of bifoveal fusion or unstable functional scotoma (on the synoptophore), diplopia or simultaneous vision, binocular vision at specific working distances (e.g., at 33 cm).

Methods of dissociation of accommodation-convergence (dissociation method), restoration of the bifixation mechanism (reflex), binarimetry, phase haploscopy, etc. are used.

3.3 Surgical Treatment

Comments: restoration of a symmetrical or near-symmetrical eye position is achieved by altering muscle balance. Muscle-weakening procedures include: recession (moving the muscle attachment site posterior to the anatomical insertion), tenotomy (severing the muscle tendon), partial myotomy (making transverse marginal incisions on both sides of the muscle), and muscle lengthening via various plastic manipulations. Muscle-strengthening procedures include resection of a muscle segment, creation of a muscle or tendon fold – tenorrhaphy, as well as anterior transposition of the muscle attachment site (anteplacing). If a residual strabismus angle persists after the first stage of surgery, the second stage of surgery on another muscle of the same eye or on the other eye is performed 6–8 months later.

4. Medical Rehabilitation and Sanatorium-Resort Treatment

5. Prevention and Dispensary Observation

Comments: the frequency of preventive examinations in children and adults is determined by the relevant orders of the Russian Ministry of Health (see Appendix A3). Examinations during the first year of life and the prescription of correction for identified refractive errors are of particular importance [43].

6. Organization of Medical Care

Planned medical care is provided for concomitant strabismus.

Primary pre-medical health care for adults is provided by medical optometric opticians.

Primary medical health care for children and adults with concomitant strabismus is provided by ophthalmologists. An ophthalmologist in an ophthalmological office provides: consultative, diagnostic, and therapeutic care; dispensary follow-up of children; in the presence of medical indications, refers children to the pediatric vision protection room, and children and adults to specialized ophthalmological medical institutions for inpatient medical care.

In case of suspected or detected signs of strabismus and/or signs of vision loss in children and adults, pediatricians, district pediatricians, general practitioners (family physicians), district general practitioners, district occupational therapists, and neurologists refer patients for a consultation with an ophthalmologist (initial ophthalmologist appointment (examination, consultation)).

During routine medical examinations of minors, including upon admission to educational institutions and during the period of study, the ophthalmologist examines children at the age of 1 month, 12 months, 3 years, 6 years, 7 years, 10 years, 11 years, 15, 16, and 17 years.

The ophthalmologist examines adults with concomitant strabismus during mandatory preliminary medical examinations (assessments) upon employment and periodic medical examinations (assessments) of workers exposed to harmful and (or) hazardous working conditions (including underground work), work related to vehicle traffic, as well as workers in the food industry, public catering and trade, water supply facilities, medical organizations and childcare facilities, and certain other employers who undergo these medical examinations for the purpose of public health protection, prevention of the emergence and spread of diseases.

In the presence of concomitant strabismus requiring surgical intervention on extraocular muscles (A16.26.028 myotomy, tenotomy of extraocular muscle, A16.26.029 transplantation, excision of extraocular muscle, A16.26.030 resection of extraocular muscle, A16.26.031 recession, tenorrhaphy of extraocular muscle, A16.26.032 dissection of extraocular muscle adhesions) and/or functional treatment (A.16.26.110 stimulation of normal function of the fovea centralis (pleoptic treatment), A19.26.001 exercises for the restoration and strengthening of binocular vision), patients with concomitant strabismus are referred for inpatient treatment to receive specialized medical care.

Indications for hospitalization in the day care unit of a medical organization:

1. concomitant strabismus in children when indications for functional treatment are identified and it cannot be performed on an outpatient basis in a pediatric vision protection room;

2. concomitant strabismus in adults when indications for surgical intervention on extraocular muscles and/or indications for functional treatment are identified.

Indications for hospitalization in the 24-hour inpatient department of a medical organization:

1. concomitant strabismus in children when indications for surgical intervention on extraocular muscles are identified;

2. concomitant strabismus in adults when indications for surgical intervention on extraocular muscles are identified, and it cannot be performed or is inappropriate in a day care unit;

3. concomitant strabismus in children when indications for functional treatment are identified and it cannot be performed on an outpatient basis in a pediatric vision protection room or in a day care unit.

The basis for discharging a patient from a medical organization is the complete completion of the planned treatment.

7. Additional Information

Concomitant strabismus is one of the frequent forms of visual pathology in childhood, accompanied by severe impairment of mono- and binocular visual functions, and is also a burdensome cosmetic defect. Individuals suffering from strabismus are limited in their professional choices [5].

The treatment of concomitant strabismus should follow a phased approach:

1. optical correction (A23.26.001 selection of spectacle correction, A23.26.002 selection of contact lens correction) of identified concomitant refractive errors;

2. pleoptics (A.16.26.110 stimulation of normal function of the fovea centralis (pleoptic treatment)) is prescribed if amblyopia is detected (in concomitant strabismus, most commonly dysbinocular);

3. orthoptic treatment (A19.26.001 exercises for the restoration and strengthening of binocular vision) – overcoming functional scotoma or abnormal retinal correspondence, formation of bifixation, and development of fusion reserves;

4. diploptics (A19.26.001 exercises for the restoration and strengthening of binocular vision) – development of binocular, depth, and stereoscopic vision in natural or close-to-natural conditions;

5. surgical treatment (A16.26.028 myotomy, tenotomy of extraocular muscle, A16.26.029 transplantation, excision of extraocular muscle, A16.26.030 resection of extraocular muscle, A16.26.031 recession, tenorrhaphy of extraocular muscle, A16.26.032 dissection of extraocular muscle adhesions).

The surgical stage may precede orthoptic and diploptic treatment.

Criteria for Evaluating the Quality of Medical Care

Table 1. Criteria for assessing the quality of primary health care for children with concomitant strabismus

Table 2. Quality assessment criteria for primary health care delivered to adults with concomitant strabismus

Table 3. Quality assessment criteria for specialized medical care delivered to children with concomitant strabismus

Table 4. Quality assessment criteria for specialized medical care delivered to adults with concomitant strabismus

References

Appendix A1. Working Group Composition

1. Apaev, Aleksandr Vyacheslavovich, Candidate of Medical Sciences, Association of Ophthalmologists LLC

2. Zhukova, Olga Vladimirovna, Doctor of Medical Sciences, Association of Ophthalmologists LLC

3. Plisov, Igor Leonidovich, Doctor of Medical Sciences, Association of Ophthalmologists LLC

4. Proskurina, Olga Vladimirovna, Doctor of Medical Sciences, Association of Ophthalmologists LLC

5. Stalmakhova, Regina Rasulovna, Candidate of Medical Sciences, Association of Ophthalmologists LLC

6. Tarutta, Elena Petrovna, Group Head, Doctor of Medical Sciences, Professor, Association of Ophthalmologists LLC

Conflict of interest: none declared

Appendix A2. Methodology for Developing Clinical Guidelines

Methods used for evidence collection/selection: electronic database search; analysis of contemporary scientific developments on the problem of concomitant strabismus in Russia and abroad; synthesis of practical experience of Russian and foreign colleagues.

When selecting publications as potential sources of evidence, the methodology used in each study is examined to ensure its reliability. The result of this examination affects the level of evidence assigned to the publication, which in turn influences the strength of the resulting recommendations.

A preliminary version of these guidelines was reviewed by independent experts who were asked to comment primarily on whether the interpretation of the evidence underlying the recommendations is reliable and accessible to practicing physicians and patients.

Comments were received from ophthalmologists dealing with oculomotor system pathology and binocular vision, and from primary care physicians regarding the clarity of presentation and the importance of recommendations as a working tool for daily medical practice.

Comments received from experts were carefully systematized and discussed by the chairs and members of the working group. Every item was discussed. Changes and additions recommended as a result of the discussion were incorporated into the text of the guidelines.

Target audience for these clinical guidelines:

1. Ophthalmologists;

2. General practitioners (family physicians);

3. Pediatricians;

4. District pediatricians;

5. General practitioners;

6. District general practitioners;

7. Neurologists;

8. Medical optics optometrists.

Table 1. Scale for assessing levels of evidence (LE) for diagnostic methods (diagnostic interventions)

Table 2. Rating scale for levels of evidence (LE) for preventive, therapeutic, and rehabilitation methods (interventions)

Table 3. Rating scale for levels of evidence (LoE) for prevention, diagnostic, treatment, and rehabilitation methods (preventive, diagnostic, therapeutic, and rehabilitative interventions)

Procedure for updating clinical guidelines.

The mechanism for updating clinical guidelines provides for their systematic revision at least once every three years, as well as upon the emergence of new evidence-based medicine data on the diagnosis, treatment, prevention, and rehabilitation of specific diseases, or in the presence of justified additions/comments to previously approved clinical guidelines, but no more frequently than once every 6 months.

Appendix A3. Reference Materials

These clinical guidelines were developed taking into account the following regulatory legal documents:

1. Order of the Russian Ministry of Health No. 442n dated October 25, 2012, "On Approval of the Procedure for Providing Medical Care to Children with Diseases of the Eye, Its Adnexa, and Orbit" (Registered with the Russian Ministry of Justice on December 20, 2012, No. 26208).

2. Order of the Russian Ministry of Health No. 902n dated November 12, 2012, "On Approval of the Procedure for Providing Medical Care to Adults with Diseases of the Eye, Its Adnexa, and Orbit" (Registered with the Russian Ministry of Justice on December 13, 2012, No. 26116).

3. Order of the Russian Ministry of Health No. 203n dated May 10, 2017, "On Approval of Criteria for Assessing the Quality of Medical Care" (Registered with the Russian Ministry of Justice on May 17, 2017, No. 46740).

4. Order of the Russian Ministry of Health No. 514n dated August 10, 2017, "On the Procedure for Conducting Preventive Medical Examinations of Minors" (along with the "Procedure for Completing Accounting Form No. 030-PO/u-17 'Minor's Preventive Medical Examination Card'"; "Procedure for Completion and Submission Deadlines of Statistical Reporting Form No. 030-PO/o-17 'Information on Preventive Medical Examinations of Minors'") (Registered with the Russian Ministry of Justice on August 18, 2017, No. 47855).

5. Order of the Ministry of Labor of Russia No. 988n, Russian Ministry of Health No. 1420n dated December 31, 2020, "On Approval of the List of Harmful and (or) Hazardous Production Factors and Jobs, in the Performance of Which Mandatory Preliminary Medical Examinations upon Employment and Periodic Medical Examinations Are Conducted" (Registered with the Russian Ministry of Justice on January 29, 2021, No. 62278).

6. Order of the Russian Ministry of Health No. 29n dated January 28, 2021, "On Approval of the Procedure for Conducting Mandatory Preliminary and Periodic Medical Examinations of Workers Provided for in Part Four of Article 213 of the Labor Code of the Russian Federation, the List of Medical Contraindications to Performing Work Involving Harmful and (or) Hazardous Production Factors, as Well as Work Performed with Mandatory Preliminary and Periodic Medical Examinations" (Registered with the Russian Ministry of Justice on January 29, 2021, No. 62277).

7. Decree of the Government of the Russian Federation No. 2406-r dated October 12, 2019, "On Approval of the List of Vital and Essential Medicines, as well as Lists of Medicines for Medical Use and the Minimum Assortment of Medicines Required for the Provision of Medical Care."

8. Order of the Russian Ministry of Health No. 909n dated November 12, 2012, "On Approval of the Procedure for Providing Medical Care to Children in the Profile 'Anesthesiology and Reanimatology'" (Registered with the Russian Ministry of Justice on December 29, 2012, No. 26514).

9. Order of the Russian Ministry of Health No. 919n dated November 15, 2012, "On Approval of the Procedure for Providing Medical Care to Adults in the Profile 'Anesthesiology and Reanimatology'" (Registered with the Russian Ministry of Justice on December 29, 2012, No. 26512).

10. Federal Law No. 323-FZ dated November 21, 2011, "On the Fundamentals of Protecting Citizens' Health in the Russian Federation."

Appendix B. Physician Action Algorithms

Appendix C. Patient Information

Concomitant strabismus is a form of oculomotor and visual disorders characterized by deviation of the eye from the common point of fixation, leading to impaired binocular vision. In concomitant strabismus, the functions of individual muscles are unimpaired. Concomitant strabismus is predominantly a pathology of childhood and most frequently occurs in children aged 2–3 years, but can also develop in adults.

Concomitant strabismus is not merely a cosmetic defect affecting children's psyche and character development. Due to marked impairment (or even absence) of binocular vision, the functioning of the two eyes as a unified system is disrupted. Perception of the outside world is incomplete, and difficulties arise in spatial perception of the surrounding environment and depth estimation. Concomitant strabismus affects all spheres of life, including career choice. Convergent strabismus is detected more frequently, while divergent strabismus is significantly less common.

When concomitant strabismus is detected, follow-up and treatment by an ophthalmologist are required. Treatment of concomitant strabismus is staged and sometimes continues for several years. At the first stage of treatment, optical correction is prescribed (selection of spectacle correction of vision, A23.26.001 and/or selection of contact lens correction of vision, A23.26.002), since concomitant strabismus is almost always accompanied by refractive errors. Hyperopia is frequently the direct cause of convergent strabismus in young children during their first years of life. After prescribing optical correction, functional treatment is required: pleoptics (stimulation of normal retinal fovea function (pleoptic treatment), A16.26.110) is prescribed when vision loss is detected and may require patching the dominant (non-strabismic) eye to develop visual acuity in the strabismic eye; orthoptics (exercises to restore and strengthen binocular vision, A19.26.001) is prescribed to establish the bifixation reflex and is performed using a synoptophore when the child's age allows for such sessions; diploptics (exercises to restore and strengthen binocular vision, A19.26.001) is prescribed to develop full binocular, depth, and stereoscopic vision in natural or near-natural conditions. At each stage of functional treatment, surgical intervention may be required if optical correction and exercises are insufficient to restore straight eye alignment and establish binocular vision.

If the treatment of concomitant strabismus is performed timely and in full, achieving symmetrical eye alignment and restoring binocular vision is possible; however, follow-up by an ophthalmologist is required (dispensary examination (assessment, consultation) by an ophthalmologist (B04.029.001) for children, follow-up examination (assessment, consultation) by an ophthalmologist (B01.029.002) for adults) to prevent disease recurrence.

In adults, concomitant strabismus may be accompanied by diplopia. To manage concomitant strabismus in adults, exercises to restore and strengthen binocular vision (A19.26.001), prismatic correction (selection of spectacle correction of vision (A23.26.001)), and surgical treatment (A16.26.028 myotomy, tenotomy of extraocular muscle, A16.26.029 transplantation, excision of extraocular muscle, A16.26.030 resection of extraocular muscle, A16.26.031 recession, tenorrhaphy of extraocular muscle, A16.26.032 dissection of extraocular muscle adhesions) are utilized.

If binocular vision is not established and strabismus is noticeable, surgical treatment is resorted to for cosmetic purposes; however, the effect of such an intervention may be unstable.

Appendix G. Assessment Scales, Questionnaires, and Other Evaluation Tools

Not used.