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Anisometropia in children and adults
Last reviewed: 12.07.2025
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Among the existing pathologies of vision, ophthalmologists note anisometropia. What is it? This is a refractive imbalance - when a person's right and left eyes have different refractive powers, and this difference can be several diopters. This refractive disorder (ametropia) in ICD-10 has the code H52.3. [ 1 ]
Epidemiology
Some studies have reported an increase in the prevalence of anisometropia with age [ 2 ], [ 3 ] while others have shown a nonlinear relationship between age and anisometropia [ 4 ], [ 5 ] or no relationship between age and the prevalence of anisometropia. [ 6 ], [ 7 ] Gender differences in the prevalence of anisometropia in school-aged children have generally not been found. [ 8 ], [ 9 ] However, it has been reported that the prevalence of anisometropia and astigmatic anisometropia [ 10 ] may be higher in girls than in boys.
The prevalence of anisometropia at different ages averages approximately 2% (range 1% to 11%).
This refractive error is detected in approximately 6% of children aged 6-18 years.
Atkinson and Braddick [ 11 ], [ 12 ] demonstrated that less than 1.5% of children (aged 6 to 9 months) had anisometropia greater than or equal to 1.5 diopters. Anisometropic amblyopia is less common than anisometropia and typically affects less than 1.5% of the population.
According to experts, in a third of cases, bilateral refractive errors of the same magnitude predominate (both eyes are myopic or hypermetropic).
Causes anisometropia
Despite studies of the structural and biomechanical characteristics of the eyes, as well as the features of the optical system of the eye, the main causes underlying anisometropia have not yet been sufficiently studied. In children, it is most often congenital, in adults - acquired.
There are various refractive errors: nearsightedness (myopia), farsightedness (hypermetropia), astigmatism, and presbyopia (a decrease in the ability to accommodate due to loss of elasticity of the lens in old age).
The cause of myopia is excessively high optical power of the eye (reverse focal length) or too long sagittal (front-to-back) axis of the eye, for example, due to elongation of the eyeball. This leads to displacement of the main optical focus of the eye in front of the retina of its posterior chamber. When anisometropia and myopia are combined, anisometropic myopia is defined.
In hypermetropic anisometropia, anisometropia and hypermetropia coexist, the causes of which are also associated with the morphometric features of the eye: a shortened anterior-posterior axis or insufficient optical power - with a shift in focus behind the retina.
The cause of anisometropia in some adults is unclear, but is thought to be due in most cases to an underlying condition called lazy eye (amblyopia).[ 13 ]
Acquired anisometropia in adults can also be associated with age-related changes in refraction or changes in the lens in one eye against the background of farsightedness.
But anisometropia in children and adolescents is etiologically associated not only with refractive disorder, but also with:
- congenital anatomical ophthalmological defects;
- heredity, which initially determines the state of the optical system of the eyes;
- different eye sizes, for example, with unilateral microphthalmia – a congenital reduction in the size of the eyeball.
At the same time, anisometropia in a teenager with myopia continues to increase throughout adulthood. More information in the material - Refractive Anomalies in Children.
Risk factors
Experts associate risk factors for the development of anisometropia in adults with certain diseases, in particular, myopia, a history of eye trauma, [ 14 ] cataracts, [ 15 ] retinal dystrophy, [ 16 ] lens displacement, vitreous hernia, ptosis, microvascular complications of diabetes and asymmetric diabetic retinopathy, [ 17 ] exophthalmos in diffuse toxic goiter, and autoimmune diseases of connective tissue.
In children, risk factors include congenital toxoplasmosis, [ 18 ] retinopathy of prematurity, [ 19 ] capillary hemangioma of the eyelids, glioma of the oculomotor nerve (developing within the orbit), [ 20 ] unilateral congenital obstruction of the nasopharyngeal duct, congenital myasthenia gravis [ 21 ], etc.
Pathogenesis
The mechanism of development, that is, the pathogenesis of anisometropia, is not fully understood.
Perhaps the point is that very few people are born with the same optical power in both eyes, but the brain compensates for this, and the person does not even suspect that his eyes are different.
This means that the development of the ciliary muscles and their functional completeness may be different during the growth of the eyeball; weakening of the sclera (the main support of the eyeball); stretching of the retina due to increased intraocular pressure, etc. [ 22 ]
The relationship between anisometropic refractive deviations and the difference between dominant and non-dominant eyes during myopia progression is studied. As it turns out, with the development of myopia, the size of the left eye increases to a lesser extent than the right eye - when the right eye is the "aiming" eye, i.e. dominant (oculus dominans).
In children, the prevalence of anisometropia increases between 5 and 15 years of age, when some children's eyes become longer and myopia develops. However, anisometropia accompanying hyperopia suggests the existence of other mechanisms of refractive imbalance.
Symptoms anisometropia
Sometimes anisometropia may be present at birth, although it is often asymptomatic until a certain age.
The key symptoms of anisometropia are:
- eyestrain and visual discomfort;
- deterioration of binocular vision;
- diplopia (double vision), which is accompanied by dizziness and headaches;
- increased sensitivity to light;
- decreased level of visual contrast (visible images are blurred);
- difference in the fields of vision of the eyes;
- violation of stereopsis (lack of perception of depth and volume of objects).
Anisometropia and aniseikonia. A symptom of a pronounced difference in the refractive power of the eyes is aniseikonia - a violation of the fused perception of images, as a result of which a person sees a smaller image with one eye, and a larger image in the other eye. In this case, the overall image is blurred. [ 23 ]
Forms
The following types of anisometropia are distinguished: [ 24 ]
- simple anisometropia, in which one eye is nearsighted or farsighted, and the refraction of the other eye is normal;
- complex anisometropia, when there is bilateral myopia or hypermetropia, but its value in one eye is higher than in the other;
- mixed anisometropia – with myopia in one eye and hyperopia in the other.
In addition, three degrees of anisometropia are defined:
- weak, with a difference between the eyes of up to 2.0-3.0 diopters;
- average, with a difference between the eyes of 3.0-6.0 diopters;
- high (more than 6.0 diopters).
Complications and consequences
During the development of the optical system of the eye, anisometropia leads to amblyopia. It is believed that almost a third of all cases of uncorrectable amblyopia are caused by anisometropia. This is explained by a violation of binocular vision, when the visual cortex of the brain during its development (during the first 10 years of life) does not use both eyes together, suppressing the central vision of one of them. [ 25 ], [ 26 ], [ 27 ]
Moreover, the risk of amblyopia is approximately twice as high in hyperopia.
In addition, the consequences and complications of anisometropia include strabismus or squinting in children, which affects at least 18% of patients with this type of ametropia, as well as accommodative esotropia (converging squint) and exotropia (diverging squint).
Diagnostics anisometropia
Early detection and treatment of anisometropia are important for the development of optimal visual function.
Initially, anisometropia can be detected by testing the binocular red reflex of each eye using the Bruckner test.
For more information on how refractive errors are diagnosed, read the separate publication – Eye examination.
Instrumental diagnostics are mandatory, see – Methods of refraction research
The goal of differential diagnostics is to identify congenital anomalies of the eyeball, lens, vitreous body, retina, which in one way or another affect the refractive power of the eyes.
Who to contact?
Treatment anisometropia
Currently, the initial treatment of young patients who are found to have anisometropia and amblyopia begins with optical correction and then additional treatments (eg, occlusion) are added if necessary.[ 28 ] If the human visual system exhibits a process of isoemmetropization, it is advisable to leave these patients untreated to allow the anisometropia to resolve and thus improve the retinal image quality in the amblyopic eye.
The most effective methods of correction are presented in the materials:
By the way, with a high degree of anisometropia, glasses do not give the desired effect, moreover, they can worsen the impairment of binocular vision, therefore contact lenses are used, for details see the article - Contact vision correction. [ 30 ]
Surgical treatment of anisometropia and its methods are given in the publications:
Prevention
There are no special methods for preventing anisometropia.
Forecast
Mild childhood anisometropia may disappear as the refraction of the eyes develops. Moderate degrees (≥ 3.0 diopters) may persist for a long time, and amblyopia often develops in preschool children.
With age – after 60 years – the risk of increasing anisometropia only increases.