Amblyopia is a persistent one- or two-sided decrease in vision that is not associated with an organic pathology of the visual analyzer and is not amenable to optical correction. The course of amblyopia may be asymptomatic or accompanied by the impossibility of stable fixation of the gaze, a violation of color perception and orientation in space, a decrease in visual acuity (from slight weakening to light perception). Diagnostics includes determination of visual acuity, perimetry, determination of color perception and dark adaptation, examination of the fundus, tonometry, biomicroscopy, determination of the type and angle of strabismus, refractometry, skiascopy, electroretinography, ultrasound of the eye, neurological examination, etc. Treatment of amblyopia is aimed at eliminating the causes that caused its development: it can be surgical (correction of strabismus, elimination of ptosis, cataract extraction) or conservative (eyeglass correction, pleoptics, penalization, physiotherapy).
H53.0 Amblyopia due to anopsia
Amblyopia (“lazy” eye syndrome) is characterized by inactivity, non-participation of one of the eyes in the process of vision. In clinical ophthalmology, amblyopia is considered as one of the leading causes of unilateral visual impairment. Worldwide, about 2% of the population suffer from amblyopia. Lazy eye syndrome is a disease mainly of childhood, therefore, the problem of its early detection and correction acquires such an important aspect.
Causes of amblyopia
Multiple factors can act as direct triggers for various types of amblyopia:
- Strabismus. The cause of dysbinocular amblyopia is monolateral friendly strabismus, when the rejected eye is excluded from participation in the visual act. With strabismus, amblyopia occurs in the squinting eye. In order to avoid diplopia, the brain suppresses the image coming from the squinting eye, which eventually leads to the cessation of impulses from the retina of the deflected eye to the visual cortex. In this case, a vicious circle is formed: on the one hand, strabismus is the cause of dysbinocular amblyopia, on the other – the progression of amblyopia aggravates strabismus.
- Anisometropy. Anisometropic amblyopia is based on uncorrected anisometropia of a high degree: in this case, amblyopia develops in the eye with more pronounced refractive errors. In turn, the causes of anisometropia can be high degrees of myopia (>8 dptr bilaterally), hyperopia (>5 dptr bilaterally), astigmatism (>2.5 dptr in any meridian).
- Refractive errors. Refractive amblyopia develops with prolonged absence of optical correction of hyperopia (hypermetropia), myopia (myopia) or astigmatism. Amblyopia develops with the following refraction differences of both eyes: hypermetropic >0.5 dpt, astigmatic >1.5 dpt, myopic > 2.0 dpt.
- Other pathologies of the visual organ. The development of obscuration amblyopia is usually associated with corneal opacity (leukoma), congenital cataract, ptosis of the upper eyelid, corneal dystrophy and trauma, gross changes in the vitreous, hemophthalmos.
- Psychogenic factors. The development of hysterical amblyopia is caused by adverse psychogenic factors, accompanied by hysteria, psychosis. At the same time, both unilateral and bilateral visual impairment, concentric narrowing of the visual fields, impaired color perception, photophobia and other functional disorders can develop.
At risk for the development of amblyopia are children born from premature birth (especially with a deep degree of prematurity), with a burdened perinatal history, mental retardation, having a family history of amblyopia or strabismus. Amblyopia is accompanied by a number of inherited diseases – Kaufman syndrome, Bench syndrome, ophthalmoplegia with myosis and ptosis.
Despite the many forms of amblyopia, the mechanism of development of the disease in all cases is associated with deprivation of shaped vision and/or pathological binocular connections, which leads to a functional decrease in central vision.
According to the time of pathology development, primary (congenital) and secondary amblyopia are distinguished. Taking into account the reasons, several forms of secondary are distinguished: strabismatic (dysbinocular), obscuration (deprivation), refractive, anisometropic, hysterical, mixed.
- Strabismatic (dysbinocular). It is based on binocular vision disorder caused by prolonged suppression of one eye. Strabismic amblyopia can be of two types: with central (correct) fixation, when the central part of the retina acts as a fixing area, and non-central (incorrect) fixation – with any other fixing area of the retina. Dysbinocular amblyopia with incorrect fixation is diagnosed in 70-75% of cases. The type of strabismic amblyopia is taken into account when choosing a treatment method.
- Obscuration (deprivation). It is caused by congenital or early acquired opacity of the optical media of the eye. It is diagnosed if reduced vision persists despite the elimination of the cause (for example, cataract extraction), and in the absence of structural changes in the posterior parts of the eye.
- Refractive. In this form, there is an error of refraction, which is not being corrected at the moment. Its origin is based on the long-term and constant projection of a fuzzy image of objects of the surrounding world onto the retina.
- Anisometropic. It develops with unequal refraction of both eyes, as a result of which there is a difference in the magnitude of the display of objects on the retina of the right and left eyes. This feature prevents the formation of a single visual image.
- Hysterical. A rare form of functional disorder that occurs on the basis of any affect is psychogenic blindness). In this case, the degree of vision loss may be partial or complete.
Amblyopia can be diagnosed in one eye (unilateral) or in both eyes (bilateral). Depending on the degree of decrease in visual acuity, amblyopia of 4 degrees is distinguished:
- weak (0.4-0.8),
- medium (0.2-0.3),
- high (0.05-0.1)
- very high (from 0.04 and below).
Symptoms of amblyopia
Various forms of pathology have their own manifestations. With a weak degree of severity, an asymptomatic variant is possible. Children, due to lack of sensory experience, cannot adequately assess how well they see and whether both eyes are equally involved in the process of vision. The possibility of amblyopia in a small child can be thought of in the presence of strabismus, nystagmus, the inability to clearly fix the gaze on a bright object.
In older children, a decrease in visual acuity and the lack of improvements from its correction, a violation of orientation in an unfamiliar place, a deviation of one eye to the side, the habit of closing one eye when looking at an object or reading, a tilt or turn of the head when looking at an object of interest, a violation of color perception and dark adaptation can indicate amblyopia.
Hysterical amblyopia in adults develops against the background of strong emotional shocks and is characterized by sudden deterioration of vision, which persists from several hours to several months. Visual disturbances in amblyopia can vary from a slight decrease in visual acuity to almost complete loss of it (light perception) and the inability of visual fixation.
To detect amblyopia, it is necessary to conduct a comprehensive ophthalmological examination. During the initial examination of the eyes, the ophthalmologist pays attention to the eyelids, the eye slit, the position of the eyeball, determines the reaction of the pupil to light. Instrumental diagnostics includes:
- Functional tests. General information about the state of vision is obtained using ophthalmological tests: visual acuity tests without correction and against its background, color testing, perimetry, refraction test. Depending on the decrease in visual acuity, the severity of amblyopia is determined.
- Inspection of eye structures. Ophthalmoscopy, biomicroscopy, examination of the eye day with a Goldman lens is performed. To determine the transparency of refractive media (lens and vitreous), an examination of the eye in transmitted light is used. With the opacity of the media, their condition is examined using an ultrasound of the eye.
- Biometrics. From biometric studies, the most important role is played by determining the angle of strabismus according to Hirschberg and measuring the angle of strabismus on the synaptophore.
- The study of refraction. In order to exclude refractive and anisometropic amblyopia, refraction studies are shown: refractometry and skiascopy.
- Other studies. A comprehensive examination of patients with amblyopia may include tonometry, electroretinography; if necessary, a neurologist’s consultation.
Treatment of amblyopia
Only early, individually selected and persistent treatment gives positive results. Correction is preferably performed at the age of 6-7 years; in children older than 11-12 years, amblyopia is practically untreatable.
The success of ophthalmic correction is directly related to the elimination of its cause. Thus, with obscuration amblyopia, cataract removal, surgical correction of ptosis, resorption therapy or vitrectomy for hemophthalmos is necessary. In the case of dysbinocular amblyopia, surgical correction of strabismus is performed.
Treatment of refractive or anisometropic amblyopia is carried out by conservative methods. At the first stage, optimal vision correction is assigned: glasses, night or contact lenses are selected, laser correction is performed with anisometropia. With hysterical amblyopia, sedatives are prescribed, psychotherapy is carried out.
After about three weeks, pleoptic treatment begins, with the aim of eliminating the dominant role of the better-seeing and activating the function of the amblyopic eye. Active and passive pleoptics are used to treat amblyopia.
Passive pleoptics consists in sealing (occlusion) of the leading eye; active pleoptics combines occlusion of the leading eye with stimulation of the retina of the defective eye by means of light, electrical impulses, special computer programs. Among the hardware methods, Amblyocore training, laser stimulation, light-color stimulation, electrostimulation, electromagnetic stimulation, vibration stimulation, reflexostimulation, computer stimulation methods, etc. have become the most widespread in abliopia. Pleoptic courses for amblyopia are repeated 3-4 times a year.
In young children (1-4 years old), amblyopia is treated with penalization – a purposeful deterioration of the vision of the dominant eye by prescribing hypercorrection or instilling an atropine solution into it. In this case, the visual acuity of the leading eye decreases, which entails the activation of the amblyopic eye. With amblyopia, physiotherapy methods are effective – reflexotherapy, vibration massage, medicinal electrophoresis.
After the pleoptic stage of amblyopia treatment, they proceed to the restoration of binocular vision – orthoptic treatment. This stage is possible when visual acuity in both eyes is at least 0.4 and the child is at least 4 years old. Usually, a synoptophore device is used for this purpose, looking into the eyepieces of which the patient sees separate parts of the whole image, which must be visually combined into one picture. Amblyopia is treated until approximately the same visual acuity of both eyes is achieved.
Prognosis and prevention
The prognosis depends on the causes and time of detection of the disease. The earlier amblyopia correction is started, the more successful the result will be. The greatest effect is achieved when the treatment is carried out before the child reaches 7 years of age, until the formation of the eye is completed. In the case of timely and complete treatment of amblyopia, in most cases it is possible to almost completely normalize vision. Adults with amblyopia develop a persistent irreversible decrease in visual acuity.
Prevention is achieved by conducting a regular medical examination of children, starting from 1 month of life. When detecting opacity of the optical media of the eye, ptosis, nystagmus, strabismus, early elimination of defects is necessary. A lasting effect can be achieved with the passage of a full course of treatment, strict compliance with the prescriptions of an ophthalmologist (wearing glasses, occluders, regular examination).