Anisometropy
| Classification according to ICD-10 | |
|---|---|
| H52.3 | Anisometropy and aniseikonia |
| ICD-10 online (WHO version 2019) | |
If the right and left eyes differ in their refractive power ( ametropy ), one speaks of anisometropy . For example, one eye can be nearsighted and the other farsighted . It also happens that one eye is only very slightly farsighted, while the other has very strong farsightedness. This can also apply to myopia and astuteness . The extent of this side difference is given in units of diopters . Small anisometropia values are the rule, anisometropia of more than 2 diopters is found in around 3% of all people.
causes
A distinction is made between the refractive power anisometropy and the length anisometropy . Differences in the refractive index of the cornea and the lens of the eye are the cause of the refractive index anisometropia and thus also of the ametropia. The length anisometropy, in turn, is caused by different overall lengths of the two eyeballs ( myopia and hyperopia ).
Correction and therapy
When correcting anisometropia with spectacle lenses - more so than when using contact lenses - retinal images of different sizes are created ( aniseikonia ). From a refractive index difference of three dioptres, sometimes massive disruptions of binocular vision can occur. The eyeglass corrections, which can be necessary due to the widely differing refractive indexes of the eyes, also lead to a cosmetically striking appearance of the eye area and, due to the different weight, to a one-sided pressure load. In addition, prismatic side effects can occur which, depending on the current visual point of the glasses, lead to heterophoria of varying degrees ( anisophoria ).
From a certain degree of anisometropia, spectacle lenses are therefore no longer suitable as suitable corrections. B. be replaced by contact lenses or a refractive procedure , so this allows the organic, anatomical and functional situation.
Refractive amblyopia
In childhood, i.e. at a time when vision is still developing, above a certain level anisometropia can lead to functional impaired vision, so-called refraction amblyopia (synonym: amblyopia ex anisometropia ) on the more ametropic eye. Correct treatment in these cases requires appropriate glasses correction, which as a rule has to be supported by consistent occlusion treatment .
Refraction amblyopias can usually no longer be treated successfully after the onset of puberty. The reason for this is that insufficient quality neural stimulation of the eye leads to permanent damage in the first few years of life. Exceptions to this rule are known in individual cases and recent studies have shown that refraction amblyopia can also be improved in adulthood. Above all, the adult neural system also shows itself to be adaptable ("plastic"), albeit to a comparatively lesser extent and only for certain qualities.
Monovision
A certain form of anisometropy, congenital or caused by a spectacle lens or contact lens correction or surgery (e.g. cataract surgery ) enables one eye to see objects in the vicinity and the other to see objects in the distance without glasses to be able to. This phenomenon is independent of accommodation and therefore continues into old age and is also known as monovision . Due to this condition, full stereoscopic vision is often not possible and can therefore U. viewed as undesirable.
The innate form of this anisometropy was z. B. also with Johann Wolfgang von Goethe (and also Konrad Adenauer ) and is therefore also referred to as Goetheblick.
literature
- Herbert Kaufmann (Ed.): Strabismus. With the collaboration of Wilfried de Decker et al. Enke, Stuttgart 1986, ISBN 3-432-95391-7 .
- Theodor Axenfeld (founder), Hans Pau (ed.): Textbook and atlas of ophthalmology. With the collaboration of Rudolf Sachsenweger and others 12th, completely revised edition. Gustav Fischer, Stuttgart et al. 1980, ISBN 3-437-00255-4 .