Amblyopia

from Wikipedia, the free encyclopedia
Classification according to ICD-10
H53.0 Amblyopia ex anopsia
ICD-10 online (WHO version 2019)

As amblyopia (from Greek. Ἀμβλύς, dull ', and ὅψις, eye', 'face', 'See') or amblyopia is the functional visual impairment of one or more rarely both eyes indicated that on an inadequate development of the visual system early during Childhood is based. The result is an impairment of shape perception with a reduction in visual acuity , which cannot be explained by organic defects in the eye, and which persists even with optimal optical correction with glasses or contact lenses .

Symptoms

The main symptom is a unilateral or bilateral reduction in visual acuity, the extent of which can reach the degree of blindness . In addition to the central deterioration in visual acuity, so-called contour interactions (separation difficulties or crowding) often occur , which can lead to considerable problems when reading text and recognizing series optotypes . Furthermore, it can lead to disturbances of the binocular vision , especially the spatial vision .

Frequency and social importance

Taking into account geographical differences, an amblyopia frequency of 5 to 6% of the population in Central Europe is assumed. Certain sources represent amblyopia as the main cause of visual functional impairment during the first 45 years of life. Amblyopia in only one eye is often not even perceived and subjectively does not bother much, while poor vision in both eyes is more likely to be perceived as a disability requiring treatment. However, untreated amblyopia, for example as a result of an undiagnosed microstrabismus , can result in visual acuity of less than two percent (visual acuity of 0.02 or 1/50) in the affected eye, which must be equated with one-sided blindness .

In addition, the diagnosis oculus ultimus (“last eye”) has to be made here. This situation poses a not inconsiderable risk in daily life and has fatal consequences if something should happen to the healthy eye as a result of an accident or illness. Scientific studies have shown that the loss of the better eye in adult amblyopia is around 1.75%, almost three times the general frequency of blindness. This is mainly due to accidents followed by other diseases in a ratio of 14: 9.

Risk factors

The following are considered risk factors:

Causes and classification

Amblyopia often develops during early childhood development, especially in the sensitive visual development phase of the first 3-4 months of life. The earlier amblyopia occurs, the more massive the deficits will develop. The cause is always a qualitatively inadequate or even lacking stimulation of the sensory cells, which is necessary for normal visual acuity development. Amblyopias arise in an initially normal nervous system / brain . Secondary, however, there are organic changes in the lateral knee cusps (corpus geniculatum laterale) of the brain and detectable changes in the cerebral cortex , presumably also in the retina and optic nerve , with persistent visual impairment . In infants , these cell changes and pathological excitation processes develop very quickly within a few weeks to months, depending on their age .

Some forms of amblyopia can appear later in childhood (late amblyopia). Only in adulthood does the risk of amblyopia tend to zero.

Amblyopias in the strict sense of the word are not toxic, for example visual impairments caused by cassava , alcohol or tobacco , since they are based on optic atrophy .

The following groups can be divided according to their etiology.

Stimulus deprivation amblyopia

The cause of amblyopia lies in a reduced or completely absent foveolar stimulus, often caused by congenital organic disorders. These include, for example, all types of opacities in the refractive media ( cornea , lens , vitreous humor ), but also the closure of the eye due to congenital ptosis or a hemangioma . The resulting lack of stimulation leads to a loss of excitability in the corresponding cells in the visual cortex . Even during school age, late-night amblyopia can be triggered by acquired causes or injuries.

An intensive and uncontrolled closure of an eye with a plaster can lead to massive amblyopia. Incorrectly performed occlusion therapies, which are actually supposed to treat amblyopia, can therefore lead to a deterioration in visual acuity of the occluded eye and in this sense also belong to the deprivation amblyopia.

In the case of unilateral or uneven organic defects in childhood, the impairment of visual acuity is superimposed by functional aspects, the extent of which is not always obvious. In such cases one speaks of relative amblyopia.

Stimulus deprivation amblyopias can occur unilaterally or bilaterally. Another term for this form of amblyopia is amblyopia ex anopsia .

Suppression amblyopia

Pure suppression amblyopia results from a functional visual field loss , the so-called suppression scotoma , and occurs in unilateral strabismus . For this reason, one speaks here of the strabismus amblyopia . It accounts for about half of all cases of amblyopia. The suppression of a visual impression of the cross-eyed eye prevents the perception of annoying double images, but at the same time also a necessary stimulation of the sensory cells. The eye is not used. Suppression amblyopia can also occur at school age, for example in the course of so-called normosensory late squint . This form of amblyopia is often accompanied by a so-called eccentric fixation , in which the retinal point of sharpest vision, the fovea centralis , is no longer used for fixation, but a place next to it. Associated with this is a transition from the main visual direction of the eye, which is usually associated with the fovea, to the point of eccentric fixation.

Refractive amblyopia

Refraction amblyopia, also known as amblyopia ex anisometropia or amblyopia ex ametropia , is either the result of very different refractive ratios in the right and left eyes (anisometropia) or a high degree of bilateral ametropia (ametropia). In the first case, there is a different stimulus situation between the two eyes, which usually disadvantages the more ametropic eye. In the second case, the degree of underdevelopment depends on the type and extent of the refractive errors and the quality of the stimulus that can be achieved with them. Children with bilateral nearsightedness ( myopia ) therefore generally do not have amblyopia, since the image quality in the vicinity is adequate. In the case of farsightedness ( hyperopia ), amblyopia on both sides is more likely to occur, despite the possibility of compensation through accommodation from a certain degree of ametropia. The likelihood of amblyopia ex ametropia is highest when a higher grade astigmatism is present, since here an acceptable image quality and thus stimulation of the sensory cells cannot take place at any distance.

Mixed forms

Despite the above classification of amblyopia according to its cause, the mixed forms predominate in practice, especially those of strabismus amblyopia and refractive amblyopia.

Examination and differential diagnosis

Amblyopia is usually diagnosed when carrying out eye tests or when checking visual acuity, the poor results of which cannot be adequately explained even by extensive ophthalmological examinations. When assessing small children, there are also other signs that indicate possible amblyopia, for example violent defensive movements when holding the healthy eye closed or eccentric fixation . The earlier amblyopia is detected, the better the prognosis for successful treatment. In principle, it is to be distinguished from visual impairments of other causes, which can also occur without recognizable organic problems of the eye. These include e.g. B. psychogenic disorders such as dissociative sensory disorders , night blindness and neuritis nervi optici .

A clear clarification of the causes is essential for an effective treatment approach, which often runs into difficulties, especially with mixed forms. For example, it is difficult to tell at first glance whether a lens opacity ( cataract ) is the reason for the deterioration in vision or an amblyopia that is concealed behind it. Special examination methods , for example laser retinometry (interference vision ), therefore allow corresponding prognostic statements to be made about the expected result of any surgical intervention. Another way of distinguishing organically caused visual impairments from functional ones is the so-called Ammann gray glass test .

Amblyopia is divided into mild (visual acuity 0.4-0.8), moderate (visual acuity 0.1-0.3) and high-grade (visual acuity less than 0.1). The diagnosis should be based on multiple examinations that take into account the physiological development of visual acuity for single and series optotypes .

treatment

The primary goal of treatment is to achieve or restore normal or at least improved visual acuity with central fixation and the associated reduction in the risks that arise from “practical one-eyedness”. Although it is assumed that once visual acuity has been passed can be reproduced with restrictions, functional visual impairments that arise during the first year of life and are not immediately discovered and treated are generally no longer curable once puberty has been reached . It is therefore advisable, especially if you have a family disposition, to have a routine preventive examination by an appropriately specialized ophthalmologist . Amblyopia treatments are generally not used to eliminate strabismus .

In the case of deprivation and refraction amblyopia, the first step in amblyopia treatment is to eliminate or correct the causal factors with the aim of enabling adequate stimulation of the sensory cells. This means, if necessary, surgical therapy of the organic disorders and / or the correction of the existing refractive errors using glasses or contact lenses .

For the reasons mentioned, amblyopias show only a limited improvement in visual acuity, even after the removal of organic disorders or the provision of optimal eyeglass correction. The next step therefore consists of supporting measures with which the affected eye is specifically stimulated or even forced to use it. This is particularly necessary in the case of strabismus amblyopia, as this eye is usually not used. For the symptomatic treatment of amblyopia, various methods have been found, e.g. B. occlusion or plaster treatment , penalization (special treatment using certain eye drops and glasses) or in some cases pleoptic exercise treatments have proven successful. The nature and extent of these treatments will depend on many different factors and precise examinations. However, a promising therapy often lasts up to the age of 13 or 14 and should not be stopped too early to avoid possible recurrences. Appropriate therapy is also strongly recommended for late school-age amblyopia and relative amblyopia.

  • Recurrence rate in three different treatment groups depending on the period without treatment measures; Visual acuity decrease of 2 optotype levels or more
without therapy until Total number = 100% Visus unchanged Drop in vision
5 months 43 32 11 (25.6%)
6-11 months 25th 17th 8 (32.0%)
12-30 months 33 24 9 (27.0%)
  • Recurrence rate in three different treatment groups depending on age at the start of treatment; Visual acuity decrease of 2 optotype levels or more
Age at the start of therapy Total number = 100% VA equal or better Drop in vision
4th Ly. 56 43 13 (23.2%)
5th year 16 11 5 (31.3%)
6-10 Lj. 62 37 25 (40.3%)

Just like “pure” amblyopias, the “relative” amblyopias should also receive appropriate therapeutic intervention, even if the extent of the functional aspects of a visual impairment is not obvious. Even a partial improvement in visual acuity, not a cure, can be critical to the patient.

Prevention and early detection

As the best prevention against amblyopia, the professional association of ophthalmologists in Germany (BVA) recommends an early examination by an ophthalmologist. Assessment is usually possible as early as infancy.

In particular, if there is a family history of such illnesses, clarification is recommended within the first week of life; for all other children between the 4th and 8th week of life, in order to rule out congenital anomalies. If the appropriate risk factors are present, an examination to rule out strabismus and refraction-related amblyopias is recommended at 6–12 months. In principle, all children between 30 and 42 months should undergo an ophthalmological examination to rule out strabismus or amblyopia.

The aim is to ensure the best possible prophylaxis or therapy for amblyopia, to improve binocular vision and to minimize the risk of blindness due to a later loss of the non-amblyopic eye. In addition, efforts are made to achieve a significant improvement in the findings, if possible before school enrollment, since acceptance and compliance with regard to intensive amplyopia treatment decrease significantly after this point and necessary measures are increasingly difficult to carry out.

Treatment in adults

The question of how to treat amblyopia after the age of 12 is sometimes controversial. In principle, it is assumed that with increasing age, the possibility of an improvement in findings tends towards zero. It is true that rare cases are known in which, after therapy, the visual acuity of the amblyopic eye has improved even in adulthood, especially if the better eye had previously been lost. In other patients, however, the loss of the good eye and extensive training treatments over long periods of time did not lead to any increase in visual acuity in the amblyopic eye. Motivation on the one hand and the existing type of fixation on the other can play a role. However, the risks of possible persistent double vision and the foreseeable private and professional burdens with very little prospect of improvement make a therapy recommendation always a matter that has to be considered individually.

Web links

Wiktionary: Amblyopia  - explanations of meanings, word origins, synonyms, translations
Commons : Amblyopia  - collection of images, videos and audio files

literature

  • Herbert Kaufmann (Ed.): Strabismus. With the collaboration of Wilfried de Decker et al. Enke, Stuttgart 1986, ISBN 3-432-95391-7 .
  • Josef Lang: Microstrabismus. The importance of microtropy for amblyopia, for the pathogenesis of the large squint angle and for the heredity of strabismus (= library of the ophthalmologist. Issue 62). 2nd, revised and expanded edition. Enke, Stuttgart 1982, ISBN 3-432-83502-7 .

Individual evidence

  1. ^ Willibald Pschyrembel: "Clinical Dictionary" , 261st edition, Berlin, New York 2007, Walter de Gruyter , ISBN 978-3-11-018534-8 , page 61.
  2. ↑ Rudolf Sachsenweger : Prophylaxis and early treatment of eye-eye blindness. VEB Verlag Volk und Gesundheit, Berlin 1966.
  3. ^ W. Haase: Amblyopia. In: Herbert Kaufmann (Ed.): Strabismus. With the collaboration of Wilfried de Decker et al., Enke, Stuttgart 1986, ISBN 3-432-95391-7 , pp. 201–280, here p. 202.
  4. ↑ a b W. Haase: Amblyopia. In: Herbert Kaufmann (Ed.): Strabismus. With the collaboration of Wilfried de Decker et al. Enke, Stuttgart 1986, ISBN 3-432-95391-7 , pp. 201–280, here p. 268
  5. ^ W. Haase: Amblyopia. In: Herbert Kaufmann (Ed.): Strabismus. With the collaboration of Wilfried de Decker et al. Enke, Stuttgart 1986, ISBN 3-432-95391-7 , pp. 201–280, here p. 247.
  6. ↑ Information from the BVA on amblyopia ( Memento from January 1, 2009 in the Internet Archive )
  7. ↑ Guideline No. 26 a (Amblyopia) (PDF; 626 kB) of the Professional Association of Ophthalmologists in Germany and the German Ophthalmological Society
  8. ^ W. Haase: Amblyopia. In: Herbert Kaufmann (Ed.): Strabismus. 3rd, fundamentally revised and expanded edition. With the collaboration of Wilfried de Decker et al. Thieme, Stuttgart 2004, ISBN 3-13-129723-9 , pp. 243-318, here pp. 315 ff.