Amblyopia: Clinical Guidelines

List of Abbreviations

BF – Biofeedback

D – diopter

VEP – visual evoked potentials

BCVA – best-corrected visual acuity

MP – microperimetry

M-BFB – microperimetric biofeedback

RLS – register of medicines

CNS – central nervous system

cpd – cycles per degree

ERG – electroretinography

EP – electrophysiological studies

BCEA – bivariate contour ellipse area

PRL – preferred retinal locus

TRL – training retinal locus

Terms and Definitions

Amblyopia is a symptom complex characterized primarily by mono- or binocular reduction of visual functions without visible organic lesions of the visual pathway, which developed as a result of restricted sensory experience (deprivation) during the development of the visual system.

Binocular vision – the integrated activity of the sensory and motor systems of both eyes, ensuring the simultaneous orientation of visual axes toward the fixation object, the fusion of monocular images of this object into a single visual percept, and its localization in the corresponding spatial location.

Biofeedback is a treatment and rehabilitation method based on developing a patient's self-control and self-regulation skills for various bodily functions to improve overall health.

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

Visual fixation is a relatively immobile positioning of the gaze on the object being viewed.

Orthoptic treatment is a functional treatment method aimed at restoring the symmetrical position of the eyes.

Microperimetry is the combined use of computer perimetry and fundus biomicrophotography using a fundus camera.

Pleoptic treatment (pleoptic therapy) is a system of treatment methods aimed at improving visual acuity in amblyopia.

Concomitant strabismus is a form of oculomotor and visual impairment 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.

1. Brief information on the disease or condition

1.1 Definition of the disease or condition

Amblyopia is a symptom complex characterized by mono- or binocular reduction of visual functions without visible organic lesions of the visual pathway, which developed as a result of sensory experience restriction during the development of the visual system [1,2,3,4,5].

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

In amblyopia, there are no organic changes, and its main causes are visual deprivation (refractive/deprivation amblyopia) and/or abnormal binocular interaction (strabismic/anisometropic amblyopia) [1,2,3,4,5,6].

The physiological mechanisms of binocular vision are based on the classical theory of retinal correspondence, according to which binocular vision is a sensory-motor apparatus organized on the principle of a reflex arc. In strabismic amblyopia, the sensory-motor mechanism that implements the transfer from disparate (non-corresponding) retinal points to corresponding ones—the bifixation mechanism—is disrupted. Confusion arises in the binocular center, i.e., the superposition of two different images. To eliminate confusion, a functional suppression scotoma is formed, which shuts down the retino-cortical pathway of the squinting eye, leading to a persistent decrease in vision and the development of amblyopia [1,2,7,8,9]. The second stage involves the formation of eccentric fixation: when the leading eye is covered, the amblyopic eye positions itself such that the image of the fixated object is projected onto a non-central area of the retina with better visual acuity than at the center—within the zone where the suppression scotoma forms. According to various authors, strabismic amblyopia is frequently complicated by incorrect fixation [1,3,4,10].

The cause of refractive amblyopia is the absence of a clear image on the retina and, consequently, of normal sensory experience during the development of the visual system. In 33–98.4% of children with refractive errors, particularly with astigmatism, refractive amblyopia is observed due to the late prescription of appropriate correction [1,3,4,6].

The cause of anisometropic amblyopia is aniseikonia—differing image sizes on the retinas of both eyes, which prevents the fusion of two images into a single visual percept [1,2,3]. At high degrees of anisometropia (above 5.0–6.0 D), the visual system of the worse eye severely lags in development, which can lead to the deviation of the eye from the visual axis and the occurrence of mixed-origin amblyopia [1].

The cause of obscuration amblyopia can be complete or partial opacification of the optical media (cornea, lens, vitreous body), developmental anomalies (lenticonus, lens coloboma, congenital aphakia, ptosis), leading to limited visual experience and typically high and very high degrees of amblyopia, which may persist even after surgical removal of the obscuration (deprivation) [1,5,11,12].

The role of hysteria in functional visual disorders is well known and widely recognized. Psychogenic factors can be the cause of hysterical amblyopia. Even with a thorough ophthalmological examination, this type of amblyopia is difficult to detect. It is observed in 1.5–1.75% of children with amblyopia [2,4,5,13].

1.3 Epidemiology of the Disease or Condition

Amblyopia is the most common cause of monocular visual acuity loss in children, with its prevalence ranging from 0.05% to 7.54% according to various studies [14,15,16,17,18,19,20,21,22]. In Russia, according to federal statistical reporting forms for 2011–2017, more than 1 million children suffer from visual impairments: myopia, hyperopia, astigmatism, amblyopia, and strabismus [23,24,25]. Ametropias account for up to 6% of the structure of visual disability, and visually impaired individuals from childhood make up 20.7% of the total number of disabled people in Russia [14,15,23]. Amblyopia is observed in 52.4% of patients with divergent strabismus and in 69.6% of patients with convergent strabismus. High and very high degree strabismic amblyopia is frequently complicated by incorrect fixation [1,3,4,10,26].

1.4 Features of Coding the Disease or Condition

H53.0 – Amblyopia

1.5 Classification of the disease or condition

The clinical classification by E.S. Avetisov, based on the causes of vision reduction in this pathology, visual acuity assessment, and the state of fixation [1].

According to the degree of visual acuity reduction, amblyopia is classified as:

▪ mild – with a visual acuity of 0.4–0.8;

▪ moderate – with a visual acuity of 0.2–0.3;

▪ severe – with a visual acuity of 0.05–0.1;

▪ very severe – with a visual acuity of 0.04 and below.

According to the mechanism of development, amblyopia is classified as:

▪ strabismic (arising due to impaired binocular vision);

▪ refractive (in the presence of refractive errors and untimely or inconsistent wearing of optical correction);

▪ anisometropic (difference in refraction between the eyes);

▪ obscuration (due to opacities of the ocular media — congenital cataract, corneal leucoma, etc.);

▪ hysterical;

▪ relative (in nystagmus, congenital myopia).

According to the state of visual fixation, the following are distinguished:

▪ stable central fixation (foveal);

▪ stable and unstable non-central fixation (parafoveal, macular, paramacular, and peripheral);

▪ absence of visual fixation.

1.6 Clinical presentation of the disease or condition

Patient complaints include deterioration of distance and near visual acuity, visual fatigue, and headaches associated with visual load. Patients frequently complain of constant or periodic strabismus.

Examination of visual acuity reveals a decrease in both uncorrected and corrected visual acuity. In cases of high and very high degree amblyopia, non-central fixation in the amblyopic eye is frequently diagnosed. Objective refraction testing typically reveals abnormalities.

Many patients with amblyopia are diagnosed with impaired binocular functions: monocular vision, simultaneous vision, functional scotoma.

The anterior segment is generally unremarkable. No pathology is detected in the fundus.

2. Diagnostics, medical indications and contraindications for diagnostic methods

Criteria for establishing the diagnosis of "amblyopia": best-corrected visual acuity (BCVA) values of 0.7 and below without structural abnormalities of the visual pathway [1].

2.1 Complaints and Anamnesis

Comments: when assessing the medical history of the disease, special attention should be paid to the age at which optical correction was first prescribed and the time of the latest correction prescription. Evaluation of the existing correction should be performed using a lensmeter. Assessment of refraction dynamics should be based on previous examination data or previously prescribed corrective glasses. Assessing refraction dynamics based on the patient's words is of low информативность. When assessing the personal history, special attention should be paid to the features and conditions of the patient's visual activity, compliance with the pleoptic treatment regimen, and prior orthoptic-pleoptic treatment [1,3,4,9].

2.2 Physical Examination

Physical examination is not performed for amblyopia.

2.3 Laboratory Diagnostics

Laboratory diagnostic tests are not performed for amblyopia.

2.4 Instrumental Diagnostics

Comments: visual acuity testing in children under three years of age is performed tentatively – it is determined whether the child has object vision. More precise measurement is possible using the preferential looking test and the visual evoked cortical potentials recording method [29,32]. Visual acuity testing in children aged three years and older is performed: from 3 years of age using children's silhouette pictures [32], and from 5 years of age using Landolt rings or "E" tests [29].

Comments: automatic refractometry and keratorefractometry is a reliable method for diagnosing refractive errors. The method allows for rapid and accurate refraction testing in children older than three years under both narrow and wide pupil conditions. In children older than one year, the examination is possible using a handheld modification of the autorefractometer [35], and in children under 1 year of age, a pediatric remote autorefractometer can be used [36].

Comments: in amblyopia combined with concomitant strabismus, the mobility of the eyeballs is fully preserved. In amblyopia combined with incomitant strabismus, there is a restriction of eyeball mobility (depending on the affected extraocular muscle).

Comments: fixation is examined using a monobinoscope, ophthalmoscope, and/or microperimeter.

Assessment of fixation stability using a microperimeter is carried out under mesopic conditions, monocularly, without mydriasis. Before the examination, patients are instructed and undergo trial testing. A 2° red cross is used as a fixation target during the examination. The patient is asked to fixate on the center of the red cross for 30 seconds. During the examination, the preferred locus of fixation is determined automatically and displayed at the end of the examination as a red cross on the fundus image. Fixation stability is evaluated quantitatively by measuring the area of two-dimensional contour ellipses (BCEA°²) encompassing 68%, 95%, and 99% of the fixation points. A smaller BCEA area indicates more stable fixation. Fixation density is evaluated in the 2° and 4° areas according to the classification of G.Y. Fujii. Unsteady central fixation is defined when less than 75% of fixation points fall within the 2° area, and eccentric fixation is defined when the deviation of the fixation point from the center of the fovea is more than 2° [41,42,45].

Comments: devices for optical examination of the posterior segment of the eye are equipped with computer software that allows for image acquisition, database creation, and data storage. They provide a quantitative assessment of the status of retinal and optic nerve parameters in children with amblyopia.

Comments: electroretinography (ERG) is a graphical representation of the electrical activity of the retina arising in response to light stimulation. ERG can be recorded from the entire retinal area (full-field or ganzfeld ERG) and from a local area of various sizes (macular ERG). ERG reflects the electrical activity of the majority of retinal cellular elements and depends on the number of healthy photoreceptors and neurons. Modern computer systems are used to record VEPs, allowing low-amplitude potentials to be isolated from noise by employing averaging and filters that neutralize various artifacts. The study is performed both while the child is awake and under sedation or general anesthesia. The main focus is on latency parameters. When analyzing the obtained data, it is taken into account that the formation of the VEP P1 wave is primarily influenced by the integrity of the retinocortical pathway, the maturity of the foveal region of the retina, and the integrity of the striate cortex. The method does not assess the integrity of the associative and cognitive functions of the brain that provide "visual recognition".

2.5 Other Procedures

Other diagnostic examinations are not used for amblyopia.

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

3.1 Optical correction

3.2 Functional treatment

Comments: one or more methods of pleoptic treatment are used to treat amblyopia.

Comments: visual and acoustic BFB training is performed monocularly, under mesopic conditions, using a microperimeter and wireless headphones. A 2° training locus in the central zone of the macular area is selected for unstable central fixation, and 5° for eccentric fixation, and it is stimulated with a light pattern of 4° for unstable central fixation and 8° for eccentric fixation with maximum brightness and a flicker frequency of 20 Hz. The patient is provided with auditory motivation to fixate their gaze within the selected locus for 10–12 minutes, 3 times a week, for a total of 12–18 sessions [41,42].

3.3 Dietary therapy

Diet therapy is not used for amblyopia.

3.4 Pain Management

Pain management is not required in the treatment of amblyopia.

4. Medical Rehabilitation and Sanatorium-Resort Treatment

Data on the efficacy, indications, and contraindications for sanatorium-resort treatment and the use of medical rehabilitation methods based on natural therapeutic factors in children with amblyopia are absent.

5. Prevention and Dispensary Observation

6. Organization of Medical Care

Medical care for amblyopia is provided on a scheduled basis.

Primary first-aid medical care for amblyopia is provided by medical personnel with secondary medical education; primary healthcare for amblyopia is provided by district pediatricians and general practitioners (family physicians). When amblyopia is suspected or detected, medical personnel with secondary medical education, district pediatricians, and general practitioners (family physicians) refer patients for a consultation with an ophthalmologist. For amblyopia, primary specialized healthcare is provided by an ophthalmologist.

In accordance with Order No. 211n dated April 14, 2025, "On approval of the procedure for minors undergoing preventive medical examinations, accounting form No. 030-PO/y 'Certificate of preventive medical examination of a minor', the procedure for maintaining it, as well as the form of sectoral statistical observation No. 030-PO/o 'Information on preventive medical examinations of minors', the procedure for filling it out during preventive medical examinations of minors, including upon admission to educational institutions and during the period of study in them," an ophthalmologist examines children at the ages of 1 month, 12 months, 3 years, 6 years, 7 years, 10 years, 13 years, 15 years, 16 years, and 17 years.

The ophthalmologist of the ophthalmology office provides: consultative, diagnostic, and therapeutic care; in the presence of medical indications, refers children to the pediatric vision conservation room or the pediatric ophthalmology department.

Medical care for children with amblyopia may (if outpatient treatment is impossible) be provided in a day or round-the-clock inpatient setting (at the discretion of the head of the pediatric ophthalmology department).

The indication for hospitalization is amblyopia requiring functional treatment that cannot be organized in an outpatient setting.

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

7. Additional Information

When managing patients with amblyopia, the following factors must be considered: the child's age, previous diagnostic and therapeutic measures, and whether there is a positive effect from previous therapeutic measures. The special importance of timely diagnosis of amblyopia is also due to the fact that there is a certain "sensitive" period, up to 7–8 years [1,3,4,5], during which the maturation and formation of the visual pathway occur, and the visual prognosis in the child will depend on age, duration of visual deprivation, and the adequacy of the treatment performed during this period. Early examinations of children with mandatory determination of refraction and, if necessary, the prescription of corrective glasses and/or contact lenses are of decisive importance in amblyopia.

Given that amblyopia, especially of high and very high degrees, is often combined with a disturbance of the fixation mechanism, it is necessary to carry out diagnostic measures aimed at investigating fixation, assessing its localization and stability, and, depending on the diagnostic results, prescribing treatment for this category of patients [1,3,4,33,41,42].

Amblyopia is a functional disorder; any structural abnormalities of the visual analyzer exclude the diagnosis of "amblyopia". To confirm/exclude the diagnosis of "amblyopia", it is necessary to assess the structural and functional features of the visual analyzer (optical examination of the posterior segment of the eye using a computer analyzer, ERG, VEP) [1,4,49,50,51].

Criteria for Evaluating the Quality of Medical Care

References

Appendix A1. Working Group Composition

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

2. Aklaeva Naila Anvarovna, Candidate of Medical Sciences, Association of Ophthalmologists LLC.

3. Zhukova Olga Vladimirovna, 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, Dr. of Med. Sci., Professor, Association of Ophthalmologists LLC.

No conflict of interest is declared.

Appendix A2. Methodology for Developing Clinical Guidelines

Methods used for collecting/selecting evidence: search in electronic databases; analysis of modern scientific developments on the problem of amblyopia 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 affects the strength of the recommendations derived from it.

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 specializing in amblyopia and primary care physicians regarding the clarity of presentation and the importance of recommendations as a working tool in 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.

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

Table 2. Scale for assessing levels of evidence (LoE) for prevention, treatment, and rehabilitation methods, including those based on natural therapeutic factors (preventive, therapeutic, and rehabilitation interventions)

Table 3. Scale for assessing grades of recommendation (GoR) for prevention, diagnostic, treatment, and rehabilitation methods (preventive, diagnostic, therapeutic, and rehabilitation interventions, including those based on natural therapeutic factors)

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. 614n dated October 9, 2025, "On Approval of the Procedure for Providing Medical Care to Children in the Profile 'Ophthalmology'."

2. Order of the Russian Ministry of Health No. 203n dated April 14, 2025, "On Approval of Criteria for Assessing the Quality of Medical Care."

3. Order of the Russian Ministry of Health No. 211n dated April 14, 2025, "On Approval of the Procedure for Minors Undergoing Preventive Medical Examinations, Accounting Form No. 030-PO/u 'Minor's Preventive Medical Examination Card', the Procedure for Its Maintenance, as Well as Industry Statistical Observation Form No. 030-PO/o 'Information on Preventive Medical Examinations of Minors', and the Procedure for Its Completion."

4. Directive of the Government of the Russian Federation No. 3867-r dated December 18, 2025.

5. State Register of Medicines (as of April 1, 2026).

Table. Drugs used for refraction determination in amblyopia

Appendix B. Physician Action Algorithms

Appendix C. Patient Information

Despite the diversity of visual physiology parameters, central vision is rightfully recognized as the main function of the organ. Upon its reduction or loss, a person loses the capacity for professional and practical activity, which leads to both a sharp decrease in quality of life and social maladjustment. Amblyopia is a pathology in which the decrease in central visual acuity is accompanied by impaired visual fixation, color, contrast, light, and electrical sensitivity. By its nature, amblyopia is a type of functional pathology of the higher divisions of the central nervous system, the pathophysiological basis of which is persistent cortical inhibition of the central vision function, developed as a consequence of sensory deprivation in early childhood. Such a condition as amblyopia reduces a child's quality of life; in high degrees, it leads to disability and a sharp restriction of future professional choice.

In amblyopia, it is very important to conduct diagnostic measures to exclude any other eye pathology and confirm the diagnosis of "amblyopia." Currently, modern diagnostics are oriented toward minimally invasive, fast, and, most importantly, safe devices that allow the study of the visual analyzer in pediatric patients.

Despite the large number of methods used for treating amblyopia, desired functional results are not always achieved after treatment, which, in turn, may be associated with diagnostic errors. It is necessary to diagnose the key pathogenetic link of amblyopia and chart a treatment vector taking into account the obtained data. It is worth remembering that high and very high degrees of amblyopia are often associated with impaired fixation mechanisms.

Thus, of decisive importance for children with amblyopia are correct diagnosis, timely detection of ametropia in a child and the prescription of adequate optical correction in early childhood; parental control and compliance with the pleoptic treatment regimen, and functional hardware treatment.

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

Not used.