Heterophoria

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Classification according to ICD-10
H50.5 Heterophoria - Latent squint
ICD-10 online (WHO version 2019)

As Heterophoria ( give a wiki. Hetero , variously 'and phor that being carried') refers to a latent, ie hidden squint . It is called latent because it usually only occurs when binocular vision is interrupted . In most cases, a heterophoria can be balanced free of symptoms by motor and sensory fusion , a mechanism of binocular vision. This is also known as normophoria . In contrast to this, one speaks of orthophoria if, after the fusion is canceled , there is no deviation from a common line of sight of both eyes . Heterophoria can be detected in around 70–80% of all people.

The heterophoria only becomes worthy of treatment when this disorder of the ocular muscle balance results in symptoms such as headaches, burning eyes, double vision or blurred vision. If the two-eyed single vision can no longer be maintained by an affected person, one speaks of decompensated heterophoria, which, however, now has a manifest squint. Even if this may sound confusing to the layperson, it is nonetheless part of the clinical picture of "latent" strabismus .

Diagnosis

To detect a heterophoria, methods are used that interrupt binocular vision and thus the motor fusion in different degrees of dissociation. The visual impressions of both eyes are either completely separated or differently from each other.

The masking test , one of the most important methods for the detection of strabismus, enables a complete interruption of the binocular vision . Other examinations in free space are carried out, for example, with the Schober test or the Worth test . Both are processes in which the image is separated using red-green glasses. Another examination variant is the so-called light trail test according to Bagolini. A vertical prism can be used in addition to the methods mentioned above for an even more precise assessment of the situation . Apparatus diagnostic methods offer so-called haploscopes , such as the synoptometer / synoptophore .

classification

Latent squint forms are divided according to the direction in which one eye deviates from a common line of sight .

Exophoria

Example of an exophoria with an outward deviation of the “covered” eye

In the case of an exophoria , under certain conditions one eye deviates from the common direction of vision outwards (towards the temples).

to form

If the difference in distance and near is approximately the same, one speaks of the basic type or basic exophoria . In the case of the so-called divergence excess type , the deviation is greater in the distance than in the vicinity, in the case of the convergence insufficiency type the difference in the vicinity is greater than in the distance.

As a rule, an exophoria is compensated for symptom-free by means of sensory and motor fusion. However, some patients also use the mechanism of accommodation to compensate for their distant exophoria , which is often associated with considerable discomfort and distant pseudo myopia .

Differential diagnosis

Basically, one should differentiate exophoria with and without sensory anomalies (e.g. hypo-accommodation). Likewise, intermittent exotropia should not be confused with decompensating exophoria. While sensory adaptation processes have already taken place in intermittent exotropia (exclusion, panoramic vision ), decompensating exophoria leads to double vision .

therapy

Treatment is provided, if necessary, either in an ophthalmological practice or clinic with an attached visual school or department for orthoptics . Depending on the complaint situation and findings, there are various options. These range from the correction of existing ametropia ( hyperopia , myopia , astigmatism ), through the prescription of prism lenses , to the implementation of orthoptic exercise treatments and strabismus operations . Regardless of the planned treatment, a diagnostic occlusion ( Marlow bandage ) should always precede it to ensure that the symptoms described, which trigger the treatment measures, are actually causally associated with the diagnosed exophoria.

Esophoria

In the case of esophoria , under certain conditions one eye deviates from the common direction of vision inwards (towards the nose).

to form

If the difference in distance and near is approximately the same, one speaks of the basic type . In the so-called divergence insufficiency type , the deviation in the distance is greater than in the vicinity, in the convergence failure type the deviation in the vicinity is greater than in the distance. Purely accommodative esophorias disappear after the hyperopia has been compensated (clarity). In the case of the accommodative convergence excise type, this is usually done after prescribing a corresponding near additive (bifocal lenses).

Most people with symptomatic esophoria suffer from sensory abnormalities (e.g., obligatory fixation disparity , subnormal binocular vision ). However, there are also esophorias with perfectly normal binocular vision.

Differential diagnosis

For prognostic reasons alone, esophorias with facultative microanomalies (see above) should be differentiated from those without such disorders. Microstrabisms with a so-called latent component are also to be distinguished from esophoria. In the case of the accommodative convergence excess type, there may also be hypo- accommodation . A esophoria the divergence insufficiency type can by a slight neurogenic conditional sixth nerve palsy are faked.

therapy

Purely accommodative esophorias with or without an excess of convergence are usually treated with glasses that correct any existing hyperopia as much as possible. For this purpose, preschool children are usually prescribed the values ​​determined in cycloplegia (pharmacological, temporary elimination of accommodation) minus the 0.5 diopter sphere. This serves to improve the acceptance of the glasses. For older children and adults, a subjective refraction determination is necessary, although the prescribed glasses should come as close as possible to the cycloplegic values. If a close squint angle (excess of convergence) persists after the hyperopia has been compensated for, this may make it necessary to adjust bifocal lenses, which is by the way the only form of therapy of choice for hypo-accommodative excess of convergence.

Orthoptic exercise treatments are less promising in esophoric patients. Deviations of up to approx. 5 ° can, if necessary, be corrected with prism glasses , which should be prescribed for the distance range in which there are complaints. If there are deviations of more than 5 ° and if a prism treatment fails, a squint operation is indicated. A number of tried and tested methods are available here, depending on the individual findings. To determine the greatest possible constant squint deviation, it is advisable to carry out a preoperative prism build-up.

Other forms

Latent deviations in height ( vertical phoria ) are divided into hyper and hypophoria . With hyperphoria the deviating eye is higher, with hypophoria it is lower.

There are also deviations that occur around the sagittal axis of the eye, i.e. curls or cyclophories . A distinction is made between incyclophoria ( curling inwards) and excyclophoria ( curling outwards). These forms of squint cannot be corrected with optical aids.

A direction-dependent heterophoria of varying degrees is called anisophoria . It is triggered by the prismatic side effects of the spectacle lenses with high-grade anisometropia .

etiology

Essentially three basic concepts have been discussed in the literature regarding etiology , namely static , accommodative and neurogenic heterophoria. The first group of static heterophoria includes mechanical and anatomical components, such as the structure and position of the orbit or the holding and movement apparatus of the eyes. Accommodation heterophorias are said to be caused by incorrectly corrected refractive errors or by a disruption of the ratio of accommodative convergence to accommodation achieved ( AC / A quotient ). In this sense, uncorrected hyperopia can also trigger esophoria. The group of neurogenic heterophorias finally summarizes the central nervous causes, such as disorders of sensory fusion (image merging) or brain stem disorders.

This type of classification nevertheless only includes the motor disorders of the heterophoria and does not take into account the possible complaints and anomalies of binocular vision. For this reason, the terms normophoria (heterophoria without complaints, asymptomatic heterophoria) and pathophoria (heterophoria with complaints, symptomatic heterophoria) have been proposed.

Symptoms

The complaint situation with symptomatic heterophoria can be very different. It also depends on whether the sensitivities are triggered by motor or sensory causes. Such a symptom complex is generally summarized under the term asthenopia . The symptoms can appear individually or in combination. These include:

  • Double vision
  • nonspecific headache
  • Blurred vision
  • reddened or burning eyes
  • general feeling of tension in the eyes and head
  • Decreased visual resilience, especially when doing activities nearby
  • Lack of concentration
  • increased sensitivity to glare
  • dizziness

What is significant about asthenopic symptoms is that they only appear during the day. The determination of the relationships under which they occur and a correspondingly careful anamnesis are of correspondingly high importance.

Ametropia

Main article: Angular ametropia

A heterophoria can be differentiated into dissociated and associated heterophoria on the basis of the examination method used. An associated heterophoria is by some opticians and a few ophthalmologists in close connection with a particular procedure ( MKH = Measurement and Korrekstionsmethode Haase) also phoria called. This term from the field of ophthalmic optics was rejected by the majority of evidence-based medicine , as a scientifically sufficient validation of the overall concept has not yet been provided. In principle, however, “ametropia” and the associated heterophoria differ only in the measurement and examination method used. The results obtained are then to be assessed and, if necessary, treated using the known and proven methods provided by ophthalmology in general and strabology in particular. A study on the supposed effectiveness of prism correction according to MKH was published in 2015. Wearing the MKH prisms for several weeks is said to have significantly reduced both the objective and the subjective fixation disparity .

See also

Web links

Individual evidence

  1. ↑ Herbert Kaufmann, Heimo Steffen (Ed.): Strabismus . 4th edition. Georg Thieme Verlag, Stuttgart, New York 2012, ISBN 978-3-13-156934-9 , pp. 193 (660 p., Limited preview in Google Book search).
  2. ↑ PLOS.org

literature